JP2019152215A - Drive transmission device, sheet conveyance device employing the same, and image recording device - Google Patents

Abstract

To provide a drive transmission device capable of immediately performing drive transmission and switching of a speed reduction ratio in the case of forward rotation/backward rotation.SOLUTION: In a drive transmission device which transmits an inputted torque through a drive transmission part to a rotary member, the drive transmission part comprises: a first gear train in which multiple gears are meshed and which transmits the inputted torque to the rotary member via a one-way clutch that transmits a torque in one direction but does not transmits a torque in the other direction; and a second gear train in which multiple gears are meshed and which transmits the inputted torque to the rotary member via a torque limiter that stops transmitting the torque when a rotational load more than or equal to a predetermined level is applied. A speed reduction ratio of the first gear train is different from a speed reduction ratio of the second gear train.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a drive transmission device that transmits a rotational force so that a rotation speed is different when a rotation member is rotated forward and backward by a drive source.

  2. Description of the Related Art Conventionally, there is a recording apparatus that forms an image while nipping and conveying a recording medium by a plurality of pairs of rollers in a conveyance path of the recording medium. In such a recording apparatus, in general, the conveyance speed of the downstream roller pair is set higher than that of the upstream roller pair. Thereby, tension is applied to the recording medium to be conveyed, and the recording medium is prevented from being loosened during conveyance.

  In addition, in the case of a recording apparatus that transports a long recording medium such as a roll sheet and performs printing by the recording head, the recording head after the recording medium that has been recorded is transported to the discharge port and cut by a cutter. In general, image formation is performed after so-called back feed, in which the leading edge of the recording medium is returned to the upstream side. As a result, it is possible to reduce the margin on the front side of the recording medium.

  However, if the transport speed of the downstream roller pair is set faster than the upstream roller pair as described above, the transport speed becomes slower toward the upstream side during backfeeding, There is a problem that jamming due to the sheet loosening on the conveyance path and a problem that the sheet is stretched to become a load when the printing is conveyed after that, resulting in deterioration of image quality.

  On the other hand, in Patent Document 1, a gear for forward rotation via a one-way clutch and a gear for reverse rotation via a torque limiter are arranged on one axis and can swing around a sun gear so as to mesh with these gears. The first planetary gear and the second planetary gear are arranged, and the gear via the one-way clutch and the first planetary gear mesh during forward rotation, and the gear via the torque limiter meshes with the second planetary gear during reverse rotation. Thus, a technique has been proposed in which the reduction ratio is switched during forward rotation and reverse rotation. Accordingly, the speed of the roller pair on the downstream side in the conveyance direction is increased both during normal rotation and during reverse rotation to suppress sheet slack.

JP-A-5-185668

  However, in the configuration of Patent Document 1, when the reduction ratio is switched between forward rotation and reverse rotation, the planetary gear swings around the sun gear according to the rotation direction, and the forward rotation planetary gear and the reverse rotation planetary gear are rotated. Engage with one of the planetary gears. For this reason, in order to perform forward / reverse switching, it is necessary to swing the planetary gear by a predetermined angle, and there is a concern that the recording medium may be jammed or the label is peeled off due to deflection of the recording medium.

  In addition, a space for swinging the planetary gear is required, and there is a problem that it is difficult to reduce the size.

  The present invention has been made in view of such problems existing in the prior art, and an object of the present invention is to provide a drive transmission device capable of immediately switching between drive transmission and reduction ratio during normal rotation and reverse rotation. Is to provide.

  In order to achieve the above object, a representative configuration according to the present invention is a drive transmission device that transmits an input rotational force to a rotating member via a drive transmission unit, wherein the drive transmission unit is engaged with a plurality of gears. A first gear train that transmits an input rotational force to the rotating member via a torque limiter that is not transmitted when a rotational load greater than or equal to a predetermined value is applied, and a gear in which a plurality of gears mesh with each other A second gear train that transmits the input rotational force to the rotating member via a one-way clutch that transmits the rotational force in one direction and does not transmit the rotational force in the other direction; And the reduction ratio of the first gear train and the reduction ratio of the second gear train are different.

  According to the present invention, it is possible to easily switch the reduction ratio according to the input rotation direction while maintaining the meshing of the gear train.

FIG. 3 is a schematic cross-sectional view illustrating a schematic configuration for conveying a recording medium of the recording apparatus according to the embodiment. FIG. 3 is a schematic plan view illustrating a schematic configuration of a drive transmission unit of the recording apparatus according to the embodiment. FIG. 3 is a block diagram illustrating a configuration of a control system of the recording apparatus according to the embodiment. 6 is a flowchart of sheet conveyance control according to the embodiment.

  Next, an embodiment of a drive transmission device according to the present invention will be described by exemplifying an ink jet recording apparatus as an image forming apparatus using the same.

<Overall configuration of recording apparatus>
FIG. 1 is a schematic cross-sectional view illustrating a conveyance configuration of a sheet that is a recording medium of the ink jet recording apparatus according to the present embodiment.

  The recording apparatus of the present embodiment conveys a continuous sheet S wound in a roll shape as a recording medium in the direction of arrow A in FIG. 1, and ejects ink droplets onto the sheet according to an image signal by a recording head 30 to form an image. To record. The recording head 30 is a so-called line printer in which nozzles that eject ink droplets are arranged and fixed in the sheet width direction orthogonal to the arrow A direction, and image formation is performed while the sheet S is continuously conveyed. An image recording unit that records an image on a sheet serves as a recording head 30 and uses black (Bk), cyan (C), magenta (M), and yellow (Y) inks to perform full-color printing on the sheet S. The recording heads 30Bk, 30C, 30M, and 30Y for discharging are provided. These are juxtaposed 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 30” in the following.

<Sheet conveying device>
Next, the configuration of the sheet conveying apparatus that conveys the sheet S according to the recording operation will be described. The sheet S is conveyed to a guide platen 11 disposed downstream by a roller pair of a conveyance roller 1 and a pinch roller 2 that are a conveyance rotation body pair, and a conveyance belt 9 that is a conveyance rotation body that is disposed further downstream. The sheet is conveyed by belt pinch rollers 4 and 6 that rotate while pressing the sheet.

  The conveying roller 1 is rotated by driving force transmitted from a conveying motor 7 as a driving source through a gear train described later, and the pinch roller 2 pressed against the conveying roller 1 is driven to rotate. The conveyor belt 9 is an endless belt that is stretched between the upstream belt roller 3 and the downstream belt roller 5, and the rotational force of the conveyor motor 7 is transmitted to the downstream belt roller 5. The transport belt 9 is rotated by the driving rotation of the downstream belt roller 5, and the upstream belt roller 3 and the belt pinch rollers 4 and 6 that are in contact with the belt belt 9 through the belt 9 are driven to rotate.

  The conveying belt 9 has holes at predetermined intervals, and the sheet S is sucked from the holes of the conveying belt 9 and moved by driving a suction fan 10 disposed at a position facing the recording head 30 with the conveying belt 9 therebetween. It is conveyed with the conveying belt 9 to be carried out.

  Further, the leading edge of the sheet S to be conveyed is detected by the leading edge detection sensor 12, and the feeding amount of the conveying belt 9 is detected by an encoder (not shown) and an encoder sensor 104 (FIG. 3). The conveyance timing and conveyance amount of the sheet are controlled based on detection by the leading edge detection sensor 12 and the encoder sensor 104, and an ink droplet is ejected from the recording head to form an image.

  In the sheet conveying configuration as described above, during printing, an image is formed while conveying the sheet S in the sheet conveying direction A, and the rear end of the image is cut to a cutting position by a cutter (not shown) disposed downstream of the conveying belt 9. Transport, cut and discharge.

  On the other hand, the cut roll sheet is conveyed so that the leading edge of the sheet is returned to the upstream side of the recording head 30 at the minimum, preferably upstream of the leading edge detection sensor 12 for the next printing.

<Drive transmission device>
In the above-described sheet conveyance configuration, the sheet is conveyed by the conveyance roller 1 and the conveyance belt 9, but the sheet conveyance in the direction of arrow A during printing (hereinafter referred to as “front feed”) and the sheet conveyance in the direction opposite to the printing time. In either case (hereinafter referred to as “back feed”), the sheet conveying speed by the downstream rotating body in the conveying direction is set to be slightly higher than the sheet conveying speed by the upstream rotating body. As a result, in both the front feed and the back feed, the sheet to be conveyed is given tension and is conveyed without being loosened.

  When the rotational force of the conveyance motor 7 is transmitted to the conveyance roller 1 via the drive transmission unit so that the above difference occurs in the conveyance speed between the conveyance roller 1 and the conveyance belt 9, the reduction ratio is different between the front feed and the back feed. It is configured as follows.

  FIG. 2 is a plan view showing a schematic configuration of the drive transmission unit according to the first embodiment, and the recording head 30, the pinch roller 2, and the belt pinch rollers 4 and 6 are not shown.

  The rotational force of the conveyance motor 7 is transmitted to the downstream belt pulley 25 by the transmission belt 8, the downstream belt roller 5 fixed to the downstream belt pulley 25 rotates, and the upstream belt roller 3 is driven by the conveyance belt 9. Is transmitted. For this reason, the rotational force of the transport motor 7 is transmitted as it is to the transport belt 9 which is the first rotating member, and the transport belt 7 rotates forward and backward by the forward and reverse rotation of the transport motor 7 to feed the sheet front and back.

  A transmission gear 24 is fixed to the upstream belt roller 3. A rotational force is transmitted from the transmission gear 24 to the transport roller 1 through a gear train. As shown in FIG. 2, a first input gear 21 and a second input gear 22 are rotatably arranged integrally on a fixed shaft (first shaft) 23 fixed to a frame member (not shown). The first input gear 21 and the second input gear 22 may be configured to simultaneously rotate at the same rotational speed by the driving force from the transport motor 7, and are generally engaged by integral molding or coupling.

  The rotation direction of the conveyance motor 7 is a direction in which the sheet is front-fed when rotated clockwise (hereinafter referred to as “CW”), and the sheet is back-fed when it is rotated counterclockwise (hereinafter referred to as “CCW”). Direction.

  A rotation shaft (second shaft) 20 is rotatably provided on a frame member (not shown), and the first output gear 16 and the second output gear 18 are rotatably attached around the rotation shaft 20. The first output gear 16 meshes with the first input gear 21, and the second output gear 18 meshes with the second input gear 22. That is, the first input gear 21 and the first output gear 16 constitute a first gear train, and the second input gear 22 and the second output gear 18 constitute a second gear train. The driving force of the transport motor 7 is transmitted to the rotary shaft 20 by the first gear train and the second gear train.

  The driving force transmitted to the rotating shaft 20 is transmitted from the pulley 15 fixed to the rotating shaft 20 to the conveying roller pulley 13 via the transmission belt 14 and to the conveying roller 1 fixed to the conveying roller pulley 13. The

  The first output gear 16 is configured to be able to transmit a rotational force to the rotary shaft 20 via a torque limiter 19. That is, the rotational force transmitted from the first output gear 16 is transmitted as it is when the load applied to the rotating shaft 20 is below a predetermined value, but is not transmitted when a rotational load above a predetermined value is applied.

  The second output gear 18 is configured to be able to transmit a rotational force to the rotary shaft 20 via the one-way clutch 17. The one-way clutch 17 is locked when the second output gear 18 is rotated in one direction (CCW direction in the present embodiment) by the input from the second input gear 22, and transmits the drive to the rotary shaft 20. When the second output gear 18 is rotated in the other direction (CW direction in this embodiment), the second output gear 18 becomes free and does not transmit drive to the rotary shaft 20.

  As described above, the driving force from the transport motor 7 is transmitted to the transport roller 1 as the second rotating member from the two series of the first gear train and the second gear train. One of the first gear trains transmits the drive via the torque limiter 19, and the other second gear train transmits the drive via the one-way clutch 17. Thereby, the speed relationship between the conveyance roller 1 and the conveyance belt 9 can be changed between the case where the conveyance motor 7 is rotated in the CW direction and the sheet is front-fed and the case where the sheet is rotated in the CCW direction and the back-feed is performed.

<Reduction ratio>
Next, a configuration in which the speed relationship between the transport roller 1 and the transport belt 9 can be switched will be described. In the present embodiment, when the driving force of the conveyance motor 7 is transmitted to the conveyance roller 1, when the conveyance motor 7 rotates in the CW direction, the driving force is transmitted via the first gear train and rotates in the CCW direction. When doing so, the driving force is transmitted through the second gear train. The reduction ratio of the first gear train and the reduction gear ratio of the second gear train are configured to be different, and the driving force is transmitted via the first gear train and the second gear train via the second gear train. The speed of the transport roller 1 with respect to the transport belt 9 is switched depending on the case of transmission.

  In the present embodiment, the number of teeth of the first input gear 21 constituting the first gear train is set to 21, and the number of teeth of the first output gear 16 meshing with this is set to 22, and the reduction ratio of the first gear train is set. Is 22/21. On the other hand, the number of teeth of the second input gear 22 constituting the second gear train is set to 23, the number of teeth of the second output gear 18 meshing therewith is set to 20, and the reduction ratio of the second gear train is 20 / 23.

  The reduction gear ratio of the second gear train that transmits the drive via the one-way clutch 17 is set to be smaller than the reduction gear ratio of the first gear train that transmits the drive via the torque limiter 19.

  Furthermore, the total number of teeth of the two gears 16 and 21 forming the reduction ratio of the first gear train and the total number of teeth of the two gears 18 and 22 forming the reduction ratio of the second gear train are both It is configured to be equal to 43. By making the total number of teeth of the first gear train equal to the total number of teeth of the second gear train, the gears 16, 21 and 18, 22 of the first gear train and the second gear train are respectively fixed shafts. 23 and the rotating shaft 20 and can be rotated while maintaining the meshing state.

(When feeding the sheet to the front)
When the transport motor 7 rotates in the CW direction to feed the sheet to the front, the output gear 16 of the first gear train rotates in the CW direction via the torque limiter 19 and the output gear 18 of the second gear train It rotates in the CW direction via the one-way clutch 17. At this time, the input from the first input gear 21 is transmitted to the rotating shaft 20 by the set torque of the torque limiter 19 to rotate the rotating shaft 20 in the CW direction. When an overload related to sheet conveyance occurs on the conveyance roller 1 or the like, the torque limiter 19 rotates idly with the rotary shaft 20.

  The second output gear 18 that is driven and transmitted via the one-way clutch 17 rotates in the direction of rotating the rotary shaft 20 in the CW direction, but the first output is because the reduction ratio is smaller than that of the first gear train. The gear 16 rotates in the CW direction faster than the speed at which the rotating shaft 20 is rotated. For this reason, the second output gear 18 is overrunning and idles and does not transmit the driving force to the rotating shaft 20. Even if the rotation speed of the second output gear 18 is slow, as described above, the one-way clutch 17 is interposed between the rotation shaft 20 and the second output gear 18 is not locked in the CW direction. Rotate free.

  Therefore, the rotating shaft 20 rotates at the rotation speed of the first gear train by the torque limiter 19. That is, the reduction ratio rotates at 22/21, and the first output gear 16 rotates at a speed lower than that of the first input gear 21. As a result, the upstream conveying roller 1 in the front feed conveys the sheet at a slower speed than the downstream conveying belt 9. For this reason, the sheet is conveyed without sagging.

(When backfeeding a sheet)
When the conveyance motor 7 is rotated in the CCW direction to back feed the sheet, the output gear 18 of the second gear train that is driven and transmitted via the one-way clutch 17 is locked with respect to the rotary shaft 20 and thus rotates. The shaft 20 is rotated at the speed of the second output gear 18. At this time, since the first gear train that is driven and transmitted via the torque limiter 19 has a larger reduction ratio than the second gear train, the rotational speed of the rotary shaft 20 to which the first output gear 16 is to rotate is high. The rotational speed of the rotary shaft 20 rotated by the second output gear 18 will not be in time. For this reason, the first gear train slides at the torque value of the torque limiter 19, and thus the rotating shaft 20 rotates at the rotational speed of the second gear train.

  That is, the reduction gear ratio rotates at 20/23, and the second output gear 18 rotates at a speed higher than that of the second input gear 22. Accordingly, the downstream conveying roller 1 in the back feed conveys the sheet at a faster speed than the upstream conveying belt 9. For this reason, the sheet is conveyed without sagging.

  As described above, the conveying speed of the upstream and downstream sheet conveying members can be switched by switching the front feed and the back feed by switching between the first gear train and the second gear train having different reduction ratios. . In this embodiment, the reduction ratio can be switched during forward / reverse rotation of the motor with a relatively small number of parts such as two shafts, four gears, a one-way clutch, and a torque limiter. Further, since the drive transmission is performed by the gear train while maintaining the meshing when the reduction ratio is switched, unlike the conventional pendulum mechanism, the rotation angle until the reduction ratio switching by the forward / reverse rotation of the motor is not required. For this reason, it is possible to quickly switch the reduction ratio in the forward / reverse rotation with an error of only the backlash.

  In addition, since the conveyance speed increases toward the downstream side in the sheet conveyance direction during printing, the cueing timing of printing is shifted due to the difference between the sheet conveyance speed by the conveyance roller 1 and the sheet conveyance speed by the conveyance belt 9. However, this can be handled by a known technique.

<Drive operation>
Next, a driving operation for conveying a sheet by the above drive transmission will be described together with a control configuration.

  FIG. 3 is a block diagram illustrating a configuration of a control system of the recording apparatus. A CPU (control unit) 101 of the recording apparatus executes control processing of the operation of the recording apparatus, 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 30 and the conveyance motor 7 via the corresponding recording head control circuit 106 and motor driver 105, respectively.

  The CPU 101 receives output signals from the sheet leading edge detection sensor 12 and the encoder sensor 104. Then, the CPU 101 sends a signal to the motor driver 105 in accordance with the program stored in the ROM 102 to control the sheet S conveyance operation. Further, the CPU 101 performs image recording control for ejecting ink from the recording head 30 via the recording head control circuit 106 so as to eject ink in accordance with output signals of the sheet leading edge detection sensor 12 and the encoder sensor 104.

  FIG. 4 is a flowchart showing an image recording method of the recording apparatus according to the first embodiment of the present invention.

  In step S300, if a print command is received, it is determined by the leading edge detection sensor 12 whether there is a sheet on the conveyance path in the image recording unit. On the other hand, if it is determined that there is a sheet, the process proceeds to step S311.

  When it is determined that there is no sheet on the conveyance path, the conveyance motor 7 is driven in the CW direction to feed the sheet to the front (S301). When the sheet leading edge detection sensor 12 detects the sheet leading edge (S302), the encoder sensor 104 that detects the feed amount of the conveying belt 9 detects a predetermined number of pulses, and then ejects ink from the recording head 30 while conveying the sheet. The recording is executed (S303).

  After the recording is finished, in order to discharge the sheet on which the image is recorded, the sheet is conveyed until the rear end portion of the image is exposed from the discharge port (S304), the conveyance motor is stopped (S305), and the printing is ended. In the case of this front feed, printing is performed while applying tension to the sheet S because the speed of the transport belt 9 on the downstream side in the sheet transport direction is higher than that of the transport roller 1 on the upstream side in the sheet transport direction. Become.

  When the next print command is received in the state where printing is completed, the sheet S remains on the conveyance path, and the process advances from step S300 to step S311.

  On the other hand, when it is determined in step S300 that there is a sheet on the conveyance path, backfeed is performed by driving the conveyance motor 7 in the CCW direction to return the sheet S and perform printing from the leading edge of the sheet (S311). When the leading edge detection sensor 12 detects the leading edge of the sheet (S312), at least the number of pulses necessary for deceleration is performed, and then the driving of the carry motor 7 is stopped (S313), and the process proceeds to step S301. At the time of this back feed, since the speed of the transport roller 1 on the downstream side in the transport direction is higher than that of the transport belt 9 on the upstream side in the transport direction by the reduction ratio switching mechanism, the back feed can be performed while applying tension to the sheet S. Don't bend S.

  As described above, according to the image recording apparatus of the embodiment, it is possible to perform drive transmission and reduction ratio switching during normal rotation and reverse rotation with a small rotation angle. For this reason, in both the forward and reverse transport directions, it is possible to increase the speed on the downstream side in the transport direction so that the sheet does not become slack, and the transport reliability is improved. Furthermore, since a reduction ratio switching mechanism can be provided in a space-saving manner, it is possible to reduce the size and cost of the apparatus.

S: Continuous sheet 1 ... Conveying roller 2 ... Pinch roller 3 ... Upstream belt roller 4, 6 ... Belt pinch roller 5 ... Downstream belt roller 7 ... Conveying motor 9 ... Conveying belt 12 ... Lead end detection sensor 14 ... Transmission belt 16, DESCRIPTION OF SYMBOLS 18 ... Gear 17 ... One-way clutch 19 ... Torque limiter 20 ... Rotating shaft 21, 22 ... Gear 23 ... Fixed shaft 30 ... Recording head

Claims (7)

In the drive transmission device that transmits the input rotational force to the rotating member via the drive transmission unit,
The drive transmission unit is
A gear train in which a plurality of gears are engaged, and a first gear train that transmits an input rotational force to the rotating member via a torque limiter that does not transmit when a rotational load greater than or equal to a predetermined value is applied;
A gear train in which a plurality of gears are engaged, and the input rotational force is transmitted to the rotating member via a one-way clutch that transmits rotational force in one direction and does not transmit rotational force in the other direction. Two gear trains,
Have
The drive transmission device characterized in that a reduction ratio of the first gear train and a reduction ratio of the second gear train are different. The first gear train has a meshed first input gear and a first output gear;
The second gear train has a meshed second input gear and a second output gear,
The first input gear and the second input gear can rotate integrally around a first axis;
The first output gear and the second output gear are rotatable about a second shaft, and the first output gear transmits a rotational force to the second shaft via the torque limiter, The second output gear transmits a rotational force to the second shaft via the one-way clutch;
The drive transmission device according to claim 1, wherein a rotational force is transmitted from the second shaft to the rotating member.   The total number of teeth of a plurality of gears forming the reduction ratio of the first gear train is equal to the total number of teeth of a plurality of gears forming the reduction ratio of the second gear train. Or the drive-transmission apparatus of Claim 2.   4. The drive transmission device according to claim 1, wherein the input rotational force is transmitted simultaneously to the first gear train and the second gear train. 5. In a sheet conveying apparatus that conveys a sheet by a rotating member that is rotated by a rotational force transmitted from a driving source,
A first rotating member that transmits a rotational force from the driving source and conveys the sheet;
A second rotating member that conveys a sheet by transmitting a rotating force transmitted from the first rotating member via the drive transmission device according to any one of claims 1 to 4,
Have
When the driving source rotates in one direction, a rotational force is transmitted to the second rotating member via the first gear train,
When the driving source rotates in the other direction, a rotational force is transmitted to the second rotating member via the second gear train. The reduction ratio of the first gear train is greater than the reduction ratio of the second gear train,
The second rotating member is located upstream of the first rotating member in the sheet conveying direction,
When the drive source rotates in the other direction, the sheet is reversely fed so that the first rotating member is on the upstream side in the sheet conveying direction from the second rotating member.
The sheet conveying apparatus according to claim 5. In an image recording apparatus that conveys a sheet and records an image,
A sheet conveying device according to claim 5 or 6,
An image recording unit for recording an image on a conveyed sheet;
An image recording apparatus comprising:

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