JP5987535B2 - Printing medium conveying apparatus and printing apparatus - Google Patents

Description

  The present invention relates to a transport apparatus that transports a print medium with a sprocket hole (engagement hole) such as fanfold paper, and a printing apparatus including the transport apparatus.

  This type of transport device includes a tractor that sequentially engages engagement holes formed at a constant pitch on a print medium and transports the print medium along a predetermined transport path, and a print head of the print device. And a conveying roller disposed in the vicinity. A driving force from a common motor is transmitted to the tractor and the transport roller via a power transmission mechanism such as a train wheel or a belt. The tractor and the conveyance roller are driven and controlled in synchronization, and the print medium is conveyed by a predetermined amount (see Patent Document 1).

  A print medium such as fanfold paper is unfolded from the folded state and is conveyed. By differentiating the conveyance speeds of the tractor and the conveyance roller, tension is applied to the print medium to remove slack, bending, and the like of the print medium. Specifically, the conveyance speed by a conveyance roller is made larger than the conveyance speed by a tractor. Since the tractor is engaged with the engagement hole of the printing medium, the holding power of the printing medium is stronger than the conveyance roller. Therefore, the conveyance roller conveys the print medium with a constant tension while causing slippage with respect to the print medium (see Patent Document 2).

JP 2009-119574 A Japanese Patent Laid-Open No. 04-159956

  In order to meet the demand for high-quality printing, it is necessary to control the conveyance amount by the conveyance roller with high accuracy. For this purpose, the frictional force of the transport roller may be increased to reduce slippage between the transport roller and the print medium. When the tractor and transport roller are driven and controlled synchronously by the same motor, if the slip between the transport roller and the print medium is reduced, the transport error of the print medium that occurs in each of the transport roller and the tractor is reduced. It is not solved by slipping. As a result, the conveyance error increases, excessive tension is applied to the print medium, and the print medium may be torn. In addition, when the print medium is reversely conveyed by reversing the conveyance roller and the tractor, excessive tension may be applied to the print medium, and the print medium may be broken at the portion of the engagement hole where the tractor engages.

  In view of the above, it is an object of the present invention to realize a printing medium conveyance device capable of preventing damage to the printing medium due to excessive tension, and a printing apparatus including the conveyance device. .

The printing medium conveying apparatus of the present invention is
A tractor and engaging the formed print medium engaging hole, conveyed along the conveying path in a predetermined conveying direction,
A conveying roller for conveying along a pre SL printing medium to the conveying path,
A motor for driving the tractor and the transport roller;
Roller for transferring the printing medium from the motor rotation proceeds before transported in the transport direction toward the conveying rollers from the tractor, and, rotating the for withdrawal after conveying in the opposite direction of the conveying direction, the conveying roller A side power transmission mechanism;
A forward power transmission mechanism for transmitting the forward rotation from the motor to the tractor via a one-way clutch;
A reverse power transmission mechanism for transmitting the reverse rotation from the motor to the tractor.

  When the print medium is transported in the transport direction, the forward rotation from the motor that is the power source is transmitted to the transport roller via the roller-side power transmission mechanism, and is transmitted to the tractor via the forward power transmission mechanism. The When the transport roller is a roller having a friction layer with a high friction coefficient in which inorganic particles are dispersed on the surface, there is almost no slip between the transport roller and the print medium, and the print medium is transported with high accuracy. . In this case, the respective transport errors of the transport roller and the tractor are not eliminated by the slip of the transport roller, and an excessive tension is easily applied to the print medium.

  In the present invention, since the one-way clutch rotates idly before the print medium is put in a state where excessive tension is applied, the tractor rotates following the conveyance of the print medium by the conveyance roller. This prevents the print medium from being broken by excessive tension.

  When the print medium is transported in the direction opposite to the transport direction, the reverse rotation from the motor is transmitted to the transport roller via the roller side power transmission mechanism. Further, the reverse rotation from the motor is transmitted to the tractor via the reverse power transmission mechanism. In this manner, the reverse power transmission mechanism is provided to transmit the reverse rotational force to the tractor without being affected by the one-way clutch. Therefore, it is possible to perform a reverse transport operation for transporting the print medium in the reverse direction of the transport direction.

In the present invention, the backward power transmission mechanism, the pre-rotation Symbol rearward to feed transportable said print medium at a first conveying speed is transmitted to the tractor, the roller-side power transmission mechanism, wherein the print medium first is configured to pre-rotation Symbol rearward to feed transportable at a slower than 1 conveying speed second transport speed is transmitted to the conveying roller.

  When the print medium is reversely conveyed, the conveyance speed by the tractor driven by the same motor is faster than the conveyance speed by the conveyance roller. As a result, the reversely transported print medium is transported in a state where a predetermined tension is applied, so that the print medium is not loosened or creased, and there is no problem such as clogging.

  In the case where the print medium is reversely conveyed in a state where tension is applied, if excessive tension is applied to the print medium, the tractor may come out of the engagement hole of the print medium. In addition, the engagement hole portion of the print medium may be torn. In order to prevent such adverse effects, a torque limiter (torque clutch) that limits the transmission torque of the reverse rotation transmitted to the tractor to a predetermined value or less may be disposed in the reverse power transmission mechanism. .

The reverse power transmission mechanism provided for transmitting the reverse rotational force to the tractor without being affected by the one-way clutch can be configured using a planetary gear mechanism. In this case, the reverse power transmission mechanism is
A rotating shaft to which the reverse rotation is transmitted from the motor;
A tractor shaft that will be placed on the tractor,
A retraction sun gear that will be fixed to the rotary shaft coaxially,
A planetary carrier that will be supported by the rotary shaft in a state of pivotable about said rotary shaft,
The supported in a rotatable state by the planet carrier, and the planetary gear for reverse intends if chewing the retraction sun gear,
The tractor shaft, mounted coaxially through the torque limiter, and a backward transfer gear that can mesh with the retraction planetary gear,
During the transmission of the rotation retracted, the retraction planetary gear by pivoting of the planet carrier engages the backward transfer gear,
When transmission of the forward rotation, the backward planetary gear by pivoting of the planet carrier is in away from the retracted transfer gear.

In order to make the forward power transmission mechanism and the reverse power transmission mechanism small and compact using a planetary gear mechanism, a tractor power transmission mechanism including these power transmission mechanisms is as follows. It is desirable to configure. That is, the tractor power transmission mechanism is
And the rotary shaft, wherein the forward rotation and the rotation retracted before SL motor is transmitted,
A tractor shaft that will be placed on the tractor,
A sun gear and retracting the sun gear for forward Ru is fixed to the rotary shaft coaxially,
A planetary carrier that will be supported by the rotary shaft in a rotatable state about the rotary shaft,
The supported in a rotatable state by the planet carrier, and the planetary gear for forward intends if chewing on the forward sun gear,
By the planet carrier, and the supported rotary shaft at a position twice rolling freely in the state of a predetermined angle with respect to the forward planetary gear as the center, if intends backward planetary gear meshing with the retraction sun gear,
A forward transmission gear that is coaxially attached to the tractor shaft via the one-way clutch, and can mesh with the forward planetary gear;
The tractor rotary shaft, mounted coaxially through the torque limiter, and a backward transfer gear that can mesh with the retraction planetary gear,
Wherein when transmission of the forward rotation, by the turning of the planetary carrier, the forward planetary gear have if chewing on the forward transfer gear, the retraction planetary gear away from said retracted transfer gear,
During the transmission of the rotation retracted, said by pivoting the planet carrier, the separated forward planetary gear from the forward transfer gear, the retraction planetary gear is adapted to mesh with the backward transfer gear.

Next, the printing apparatus of the present invention includes:
A tractor that engages an engagement hole formed in the print medium and conveys the print medium along a conveyance path;
A transport roller for transporting the print medium along the transport path;
A motor for driving the tractor and the transport roller;
Roller side power for transmitting to the transport roller the forward rotation for transporting the print medium from the motor in the transport direction from the tractor toward the transport roller and the reverse rotation for transporting in the direction opposite to the transport direction. A transmission mechanism;
A forward power transmission mechanism for transmitting the forward rotation from the motor to the tractor via a one-way clutch;
A reverse power transmission mechanism for transmitting the reverse rotation from the motor to the tractor;
And a, a printing unit for printing on pre-Symbol print medium. A printing head that ejects ink droplets onto the printing medium can be used as the printing unit. Fanfold paper can be used as the printing medium.

1 is a schematic diagram illustrating an ink jet printer according to an embodiment of the present invention. FIG. 2 is a schematic plan view showing a part of a transport device of the ink jet printer of FIG. 1. It is a model side view which shows the power transmission mechanism in the conveying apparatus of the inkjet printer of FIG. It is the model side view and model perspective view which show a part of tractor side power transmission mechanism. It is explanatory drawing which shows the rotation transmission mechanism for advance. It is explanatory drawing which shows the reverse rotation transmission mechanism. It is explanatory drawing which shows an example of the printing medium used for the inkjet printer of FIG.

  Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In each figure, an arrow X indicates a direction along the conveyance path of the print medium, X1 is a conveyance direction (forward direction) of the print medium, and X2 is a reverse direction (retraction direction) of the conveyance direction X1. An arrow Y indicates the width direction of the print medium, and an arrow Z indicates a direction orthogonal to the X direction and the Y direction.

  FIG. 1 is a schematic diagram showing the overall configuration of the ink jet printer according to the present embodiment. The ink jet printer 1 takes in paper 2 as a printing medium from a supply port 4 provided on the rear side of the printer housing 3, prints the paper 2 in the printing unit 5, and is provided on the front side of the printer housing 3. It discharges from the discharge port 6.

  The printing unit 5 includes a print head 7, a carriage 8, and a carriage moving mechanism 9. The print head 7 has a plurality of nozzles 7 a that eject ink droplets onto the paper 2. The print head 7 is mounted on the carriage 8 with its nozzles 7a directed downward in the Z direction in FIG.

  The carriage 8 is supported in a movable state by a carriage shaft 11 extending in the paper width direction (Y direction: see FIG. 2), and is reciprocated in the Y direction by the carriage moving mechanism 9. The carriage moving mechanism 9 includes a carriage motor 12 and a timing belt 13 driven by the carriage motor 12. The carriage 8 is fixed to the timing belt 13 and is reciprocated in the Y direction according to the operation of the carriage motor 12.

  The inkjet printer 1 further includes a transport device 20 that transports the paper 2. FIG. 2 is a schematic plan view showing a part of the conveying device, and FIG. 3 is a schematic side view showing the conveying device 20 of the inkjet printer 1. Referring to FIGS. 1 to 3, the transport device 20 includes a transport path 21, a first transport mechanism 22, a second transport mechanism 23, a third transport mechanism 24, and a power transmission mechanism 25. In FIG. 2, the power transmission mechanism 25 is omitted.

  The conveyance path 21 starts from the supply port 4, passes through the printing position A by the print head 7 of the printing unit 5, and ends at the discharge port 6. A first transport mechanism 22, a second transport mechanism 23, a printing unit 5, and a third transport mechanism 24 are arranged in this order from the upstream side to the downstream side along the transport path 21.

  The first transport mechanism 22 is provided in the vicinity of the supply port 4 and includes a pair of tractors 31. Each tractor 31 includes a tractor pin 32, a tractor belt 33, a drive sprocket 34, and a driven sprocket 35. The tractor pins 32 are engagement members that can be inserted into the sprocket holes (engagement holes) 2 a of the paper 2, and a plurality of tractor pins 32 are formed at predetermined intervals on the outer peripheral surface of the tractor belt 33. The tractor belt 33 is bridged between the drive sprocket 34 and the driven sprocket 35.

  As shown in FIG. 2, the pair of tractors 31 are disposed on both sides of the conveyance path 21 in the direction of arrow Y. Each tractor 31 is in a position corresponding to each of the sprocket holes 2a at both ends in the width direction of the sheet 2 to be conveyed. The drive sprocket 34 of each tractor 31 is connected to a tractor shaft 36 on the drive side, and the pair of tractors 31 can be driven in synchronization.

  The second transport mechanism 23 is provided in the transport path 21 between the first transport mechanism 22 and the printing position A, more specifically at a position near the print head 7. The second transport mechanism 23 includes a transport roller 41 and a pressing roller 42. The transport roller 41 includes a metal roller body 43 and a roller shaft 44, and is provided on the lower side of the transport path 21 in the Z direction so as to cross the transport path 21. The pressing roller 42 is made of an elastic body such as rubber, and is disposed in a state where the sheet 2 conveyed through the conveying path 21 can be pressed against the conveying roller 41 from above in the direction of the arrow Z.

As shown in FIG. 2, a friction layer 45 in which inorganic particles are dispersed is formed on the surface of the roller body 43. The friction layer 45 has inorganic particles such as aluminum oxide (alumina: Al ₂ O ₃ ), silicon carbide (SiO), silicon dioxide (SiO ₂ ) dispersed in a resin layer made of epoxy resin or polyester resin. Formed by. For example, crushed alumina is used as the inorganic particles. Alumina is relatively inexpensive and does not hinder cost reduction, and has a relatively high hardness and a good function of increasing frictional resistance. By performing the crushing treatment, the tips of the alumina particles become sharp and exhibit a high frictional force.

  The third transport mechanism 24 is provided between the print position A and the discharge port 6 in the transport path 21, more specifically at a position near the print head 7. The third transport mechanism 24 includes a discharge roller 46 and a pressing roller 47. The discharge roller 46 includes a roller body 48 and a roller shaft 49, and is provided so as to cross the conveyance path 21 on the lower side of the conveyance path 21 in the direction of arrow Z. The pressing roller 47 is disposed in a state in which the sheet 2 conveyed through the conveying path 21 can be pressed against the discharge roller 46 from above in the direction of the arrow Z.

  Next, with reference to FIG. 3, the transport device 20 includes a transport motor 60 as a drive source for transporting paper. The power transmission mechanism 25 includes a roller side power transmission mechanism 61 and a tractor side power transmission mechanism 62. The roller-side power transmission mechanism 61 rotates forward for transporting the paper 2 from the transport motor 60 along the transport path 21 in the transport direction X1 (forward direction), and the reverse direction X2 (reverse direction) of the transport direction. The reverse rotation for transporting to the transport roller 41 is transmitted to the transport roller 41 of the second transport mechanism 23. The tractor side power transmission mechanism 62 transmits the rotation from the transport motor 60 to the tractor 31 of the first transport mechanism 22. Further, the power transmission mechanism 25 includes a gear train (wheel train) 63. The gear train (wheel train) 63 rotates the discharge roller 46 of the third transport mechanism 24 in the same direction at the same transport speed in synchronization with the transport roller 41 of the second transport mechanism 23. In FIG. 3, a gear train (wheel train) 63 is indicated by a dotted arrow, and a specific configuration is omitted.

  The tractor side power transmission mechanism 62 transmits the forward rotation from the conveyance motor 60 to the first conveyance mechanism 22 via the one-way clutch, and the backward rotation from the conveyance motor 60. And a reverse power transmission mechanism 65 that transmits to the first transport mechanism 22 via a torque limiter (torque clutch) (see FIG. 4 described later).

  In the present embodiment, when the paper 2 is transported forward, the transport speed of the paper 2 by the transport roller 41 driven via the roller-side power transmission mechanism 61 is driven via the forward power transmission mechanism 64. It is larger than the conveyance speed of the paper 2 by the tractor 31 to be used. In order to obtain this relationship, the reduction gear ratio of the gear train constituting these transmission mechanisms is set. On the contrary, when the sheet is conveyed backward, the conveyance speed of the sheet 2 by the tractor 31 driven via the reverse power transmission mechanism 65 is the conveyance roller 41 driven via the roller-side power transmission mechanism 61. It is larger than the conveyance speed of the paper 2 by. In order to obtain this relationship, the reduction gear ratio of the gear train constituting these transmission mechanisms is set.

  The roller-side power transmission mechanism 61 includes a drive sprocket 60 a that is coaxially fixed to the motor shaft of the transport motor 60 and a drive gear 66 that is coaxially fixed to the shaft end portion of the roller shaft 44 of the transport roller 41 in the second transport mechanism 23. And a timing belt 67 spanning the drive sprocket 60a and the drive gear 66.

  FIGS. 4A and 4B are a side view and a perspective view schematically showing a main part of the tractor side power transmission mechanism 62. With reference to FIG. 3 and FIG. 4, the structure of the tractor side power transmission mechanism 62 which transmits the power which rotationally drives the 1st conveyance mechanism 22 to a forward direction and a reverse direction is demonstrated.

  The tractor side power transmission mechanism 62 includes a rotation shaft 70. A transmission gear 71 is coaxially fixed to the rotation shaft 70, and a timing belt 67 is bridged around the transmission gear 71. A forward sun gear 72 and a backward sun gear 73 are coaxially fixed to the rotating shaft 70. A planet carrier 74 is supported between the sun gears 72 and 73 so as to be rotatable about the rotation shaft 70.

  The planet carrier 74 includes two arm portions 74a and 74b extending in a radial direction from the rotation shaft 70 at a predetermined angle. A forward planetary gear 75 is rotatably supported at the tip of one arm 74a. The forward planetary gear 75 meshes with the forward sun gear 72. A reverse planetary gear 76 is rotatably supported at the tip of the other arm 74b. The reverse planetary gear 76 meshes with the reverse sun gear 73.

  On the other hand, a forward transmission gear 78 is coaxially attached to the shaft end portion of the tractor shaft 36 via a one-way clutch 77. The one-way clutch 77 may be either a sprag type or a cam type. The one-way clutch 77 transmits the forward rotation, but when the reverse rotation that is the reverse rotation is transmitted, the one-way clutch 77 is idled and the transmission of the reverse rotation is interrupted. Therefore, even when the transmission member on the downstream side of the transmission path of the one-way clutch 77 tries to rotate faster in the direction of the forward rotation than the transmission member on the upstream side of the transmission path in the transmission state of the forward rotation, the one-way clutch 77. Idles and the transmission path is interrupted.

  The forward transmission gear 78 is a gear that can mesh with the forward planetary gear 75, and is disposed at a position facing the forward planetary gear 75. Next to the forward transmission gear 78, a backward transmission gear 80 is disposed. The reverse transmission gear 80 is coaxially attached to the shaft end portion of the tractor shaft 36 via a torque limiter (torque clutch) 79. The reverse transmission gear 80 is a gear that can mesh with the reverse planetary gear 76, and is disposed at a position facing the reverse planetary gear 76. The torque limiter 79 slips when the transmission torque exceeds a certain value, and limits torque transmission at a value greater than that.

  In the tractor-side power transmission mechanism 62 having this configuration, the forward power transmission mechanism 64 includes, from the timing belt 67, the rotating shaft 70, the forward sun gear 72, the planet carrier 74, the forward planetary gear 75, and the forward transmission gear 78. And a transmission mechanism portion that reaches the tractor shaft 36 via the one-way clutch 77 in sequence. The reverse power transmission mechanism 65 sequentially passes the rotating shaft 70, the reverse sun gear 73, the planetary carrier 74, the reverse planetary gear 76, the reverse transmission gear 80, and the torque clutch 79 from the timing belt 67 to the tractor shaft. 36 is a transmission mechanism portion.

  FIG. 5 is a schematic side view showing the roller side power transmission mechanism 61 and the forward power transmission mechanism 64, and a side view showing a part of the forward power transmission mechanism 64. FIG. 6 is a schematic side view showing the roller side power transmission mechanism 61 and the reverse power transmission mechanism 65, and a side view showing a part of the reverse power transmission mechanism 65.

  When the forward rotation is transmitted, the rotary shaft 70 rotates in the direction of the arrow CCW in FIG. 4 by the forward rotation from the transport motor 60. By this rotation, the planet carrier 74 also turns in the same direction. As a result, the forward planetary gear 75 meshes with the forward transmission gear 78. The other reverse planetary gear 76 is separated from the reverse transmission gear 80. As a result, the tractor side power transmission mechanism 62 is in the state shown in FIG. In this state, the forward rotation from the transport motor 60 is transmitted to the transport rollers 41 and 46 via the roller-side power transmission mechanism 61. Further, the forward rotation is transmitted to the tractor 31 via the tractor side power transmission mechanism 62. As a result, the sheet 2 is transported forward in the transport direction X1.

  When the reverse rotation is transmitted, the rotary shaft 70 rotates in the direction of the arrow CW in FIG. 4 by the reverse rotation from the transport motor 60. By this rotation, the planet carrier 74 also turns in the same direction. Accordingly, the forward planetary gear 75 is separated from the forward transmission gear 78 and the meshing is released (the power transmission path is interrupted). The other reverse planetary gear 76 approaches the reverse transmission gear 80 and switches to an engaged state (a power transmission path is formed). As a result, the tractor side power transmission mechanism 62 is in the state shown in FIG. In this state, the reverse rotation from the transport motor 60 is transmitted to the transport rollers 41 and 46 via the roller-side power transmission mechanism 61. Further, the reverse rotation is transmitted to the tractor 31 via the tractor side power transmission mechanism 62. As a result, the paper 2 is conveyed backward (reversely conveyed), which is the reverse direction X2 of the conveying direction.

  Next, FIGS. 7A and 7B are explanatory views showing an example of a print medium (paper 2) used in the ink jet printer 1, and FIG. 7C is a fanfold that is a typical example of the print medium. It is explanatory drawing which shows paper.

  FIG. 7A shows one medicine bag paper 90 which is an example of a print medium. The medicine bag paper 90 is a bag-like paper that accommodates a medicine prescribed in a hospital or a pharmacy and provides the patient with the name of the patient, the kind of medicine, the method of taking, etc. on the surface.

  The medicine bag paper 90 has a two-layer structure of a transparent synthetic resin film sheet 91 and a paper sheet 92. The medicine bag paper 90 has a bag shape, and its three edges (both side edges 91a and 90b in the Y direction and the lower edge 90c in the X direction) are bonded by an adhesive, and the upper edge 90d in the X direction opens. ing. On the medicine bag paper 90, necessary items such as a patient name are printed on the paper sheet 92 by the ink jet printer 1. Moreover, the chemical | medical agent accommodated in the inside can be visually recognized through the transparent synthetic resin film sheet 91. FIG.

  As shown in FIG. 7B, a plurality of medicine bag paper 90 is provided as a continuous medicine bag paper 90A formed continuously. That is, the synthetic resin film sheet 91 and the paper sheet 92 are one continuous long sheet 91a and 92a, respectively, and both side edges 90a and 90b are bonded with an adhesive. Sprocket holes 2a with which the tractor pins 32 can be engaged are formed along the X direction at both side edges 90a and 90b at a predetermined pitch.

  These long sheets 91a and 92a can be separated one by one along the perforations 94 formed at predetermined intervals in the longitudinal direction (X direction). When separated, a medicine bag paper 90 shown in FIG. 7A is obtained. In the long sheets 91a and 92a, a portion on one side across each perforation is bonded with an adhesive along the width direction (Y direction). This adhesion portion corresponds to the lower edge 90c.

  The continuous medicine bag paper 90 </ b> A is alternately folded at the perforation 94 and has a fanfold shape. By taking such a form, the continuous medicine bag paper 90A is transported by the transport device 20 having the tractor 31 while being unfolded and subjected to continuous printing.

  The paper shown in FIG. 7C is a normal fanfold paper 96, and the sprocket holes 2a are formed at predetermined pitches along the X direction on both side edges 90a, 90b in the Y direction. The fanfold paper 96 is separable along a perforation 94 formed at a predetermined interval in the longitudinal direction (X direction). Can be separated and used as cut paper.

  The operation of the inkjet printer 1, particularly the operation of transporting the paper 2 by the transport device 20 will be described.

  First, the sprocket holes 2 a formed on both side edges 90 a and 90 b of the paper 2 are engaged with the tractor pins 32 formed on the tractor 31. Next, the transport motor 60 is driven in the forward rotation direction. The tractor side power transmission mechanism 62 is in the state shown in FIG. 5, the tractor 31 and the transport roller 41 are rotationally driven in the forward rotation direction, and the paper 2 is transported toward the transport roller 41 along the transport path 21. The sheet 2 conveyed by the tractor 31 is sandwiched between the rotating conveyance roller 41 and the pressing roller 42 and further conveyed to a predetermined cueing position (starting position of the printing operation).

  As described above, the transport speed in the forward direction by the transport roller 41 is set larger than the transport speed in the forward direction of the tractor 31. The paper holding force by the transport roller 41 is increased by the friction layer 45, but is smaller than the paper holding force of the tractor 31 that engages the tractor 31 with the sprocket hole 2a. Accordingly, the sheet 2 is conveyed while being pulled with a constant tension toward the conveying roller 41. As a result, even when the fanfold paper 96 that is unfolded and supplied from the folded form is used as the paper 2, the paper can reach the cueing position in a state in which bending, slack, and the like are appropriately removed. .

  Thereafter, the printing operation by the print head 7 is performed while the sheet 2 is conveyed along the conveyance path 21 by the conveyance roller 41. Since the friction layer 45 has a very high coefficient of friction, the sheet 2 is held by the conveying roller 41 and the pressing roller 42 with almost no slip, and the sheet 2 is conveyed with high accuracy. The tractor 31 side feeds the paper 2 in the forward direction at a transport speed slower than the transport roller 41. Accordingly, the sheet 2 can be conveyed in a state where a predetermined tension is always applied.

  Further, the rotational force for forward rotation to the tractor 31 is transmitted via the one-way clutch 77. When the tension applied to the sheet 2 exceeds a certain value, the tractor 31 is forcibly pulled in the forward rotation direction by the transport roller 41. In this state, since the one-way clutch 77 runs idle, the tension applied to the paper 2 does not increase. Therefore, the paper 2 is always conveyed in the forward direction in an appropriate tension state, and high-quality printing can be realized.

  The paper 2 transported by the transport roller 41 passes between the printing position A of the printing unit 5 and is printed by the print head 7, and then sandwiched between the rotating discharge roller 46 and the pressing roller 47. . The sheet 2 further transported along the transport path 21 by the discharge roller 46 is discharged along the discharge tray 16 from the discharge port 6.

  When it is necessary to reversely transport the sheet 2 in the backward direction, the transport motor 60 is rotationally driven in the backward rotation direction. The rotation in the reverse rotation direction is transmitted to the transport roller 41 via the transport roller side power transmission mechanism 61 and transmitted to the tractor 31 via the tractor side power transmission mechanism 62. In the tractor side power transmission mechanism 62, the path of the forward power transmission mechanism 64 is cut off, and the reverse power transmission mechanism 65 is switched to the connected state as shown in FIG.

  As described above, at the time of reverse conveyance, the conveyance speed of the sheet 2 by the tractor 31 is higher than the conveyance speed of the sheet 2 by the conveyance roller 41. Accordingly, the paper 2 is conveyed in reverse in a predetermined tension state, and paper jamming due to slack, bending, etc. is prevented. Further, the reverse rotation is transmitted to the tractor shaft 36 via the torque limiter 79. The torque limiter 79 becomes idle when the transmission torque exceeds a certain value (slip occurs), and the transmission torque is limited to a predetermined value or less. When excessive tension is generated on the sheet 2, the torque limiter 79 rotates idly and the tension of the sheet 2 is limited to a certain value or less. Therefore, it is possible to prevent such an adverse effect that excessive tension is applied and the tractor pin 32 comes out of the sprocket hole 2a of the paper 2.

  In the above-described embodiment, the forward power transmission mechanism 64 and the reverse power transmission mechanism 65 are used in the tractor side power transmission mechanism 62 using the planetary gear mechanism according to the direction of the rotational force transmitted. I am trying to switch alternatively. It is also possible to configure a switching mechanism that switches between these power transmission mechanisms 64 and 65 using an electromagnetic solenoid.

DESCRIPTION OF SYMBOLS 1 Inkjet printer, 2 sheets, 3 printer housings, 4 supply port, 5 printing part, 6 discharge port, 7 print head, 7a nozzle, 8 carriage, 9 carriage moving mechanism, 11 carriage shaft, 12 carriage motor, 13 timing belt , 16 discharge tray, 20 transport device, 21 transport path, 22 first transport mechanism, 23 second transport mechanism, 24 third transport mechanism, 25 power transmission mechanism, 31 tractor, 32 tractor pin, 33 tractor belt, 34 Drive sprocket, 35 Driven sprocket, 36 Tractor shaft, 41 Conveyor roller, 42 Holding roller, 43 Roller body, 44 Roller shaft, 45 Friction layer, 46 Discharge roller, 47 Pressing roller, 48 roller body, 49 Roller shaft, 60 Conveyance Mo -, 60a Drive sprocket, 61 Roller side power transmission mechanism, 62 Tractor side power transmission mechanism, 63 Gear train (wheel train), 64 Forward power transmission mechanism, 65 Reverse power transmission mechanism, 66 Drive gear, 67 Timing belt, 70 rotating shaft, 71 transmission gear, 72 forward sun gear, 73 backward sun gear, 74 planet carrier, 74a, 74b arm, 75 forward planet gear, 76 reverse planet gear, 77 one-way clutch, 78 forward transmission Gear, 79 Torque limiter, 80 Reverse transmission gear, 90 Medicine bag paper, 90A Continuous medicine bag paper, 90a, 90b Edge, 90c Lower edge, 91 Synthetic resin film sheet, 92 Paper sheet, 96 Fanfold paper, X In the conveyance path Direction along, X1 transport direction (forward direction), reverse direction of X2 transport direction (rear) Direction), a width direction, Z direction of the Y print medium, A printing position, CCW, CW rotation direction

Claims (7)

A tractor that engages an engagement hole formed in the print medium and conveys the print medium along a conveyance path;
A transport roller for transporting the print medium along the transport path;
A motor for driving the tractor and the transport roller;
Roller side power for transmitting to the transport roller the forward rotation for transporting the print medium from the motor in the transport direction from the tractor toward the transport roller and the reverse rotation for transporting in the direction opposite to the transport direction. A transmission mechanism;
A forward power transmission mechanism for transmitting the forward rotation from the motor to the tractor via a one-way clutch;
A reverse power transmission mechanism for transmitting the reverse rotation from the motor to the tractor;
I have a,
The printing medium conveyance device, wherein the reverse power transmission mechanism includes a torque limiter that limits transmission torque of the reverse rotation transmitted to the tractor to a predetermined value or less . The reverse power transmission mechanism transmits the reverse rotation for conveying the print medium at a first conveyance speed to the tractor,
2. The printing medium conveying apparatus according to claim 1, wherein the roller-side power transmission mechanism transmits the reverse rotation for conveying the printing medium at a second conveying speed that is slower than the first conveying speed to the conveying roller. The reverse power transmission mechanism is:
A rotating shaft to which the reverse rotation is transmitted from the motor;
A tractor shaft disposed on the tractor;
A reverse sun gear fixed coaxially to the rotating shaft;
A planet carrier supported by the rotary shaft in a state of being rotatable about the rotary shaft;
A planetary gear for retraction supported by the planet carrier in a rotatable state and meshing with the sun gear for retraction;
A reverse transmission gear that is coaxially attached to the tractor shaft via the torque limiter and can mesh with the reverse planetary gear;
With
At the time of transmission of the reverse rotation, the reverse planetary gear meshes with the reverse transmission gear by the turning of the planet carrier,
Wherein when transmission of the forward rotation, conveying apparatus of the printing medium according to claim 1 or 2 wherein the retraction planetary gear by pivoting of the planetary carrier away from the retracted transfer gear. A rotating shaft to which the forward rotation and the backward rotation are transmitted from the motor;
A tractor shaft disposed on the tractor;
A forward sun gear and a backward sun gear fixed coaxially to the rotating shaft;
A planet carrier supported on the rotary shaft in a state of being rotatable around the rotary shaft;
A forward planetary gear supported rotatably by the planet carrier and meshing with the forward sun gear;
A reverse planetary gear that is supported by the planetary carrier at a predetermined angle with respect to the forward planetary gear about the rotation axis and meshes with the reverse sun gear;
A forward transmission gear that is coaxially attached to the tractor shaft via the one-way clutch, and can mesh with the forward planetary gear;
A reverse transmission gear that is coaxially attached to the tractor shaft via the torque limiter and can mesh with the reverse planetary gear;
With
When the forward rotation is transmitted, the forward planetary gear meshes with the forward transmission gear by the turning of the planet carrier, and the reverse planetary gear is separated from the reverse transmission gear,
Wherein when transmission of the reverse rotating, wherein the forward planetary gear by pivoting the planet carrier is separated from the forward transfer gear, printing according to claim 1 or 2 wherein the retraction planetary gear meshes with the backward transfer gear Medium transport device. The printing medium conveyance device according to any one of claims 1 to 4 , wherein the conveyance roller has a friction layer in which inorganic particles are dispersed formed on a surface thereof. A tractor that engages an engagement hole formed in the print medium and conveys the print medium along a conveyance path;
A transport roller for transporting the print medium along the transport path;
A motor for driving the tractor and the transport roller;
Roller side power for transmitting to the transport roller the forward rotation for transporting the print medium from the motor in the transport direction from the tractor toward the transport roller and the reverse rotation for transporting in the direction opposite to the transport direction. A transmission mechanism;
A forward power transmission mechanism for transmitting the forward rotation from the motor to the tractor via a one-way clutch;
A reverse power transmission mechanism for transmitting the reverse rotation from the motor to the tractor;
A printing unit for printing on the print medium;
Bei to give a,
The backward power transmission mechanism, the printing apparatus according to claim Rukoto includes a torque limiter for limiting the transmission torque of the rotating rearward to be transmitted to the tractor to a predetermined value or less. The printing apparatus according to claim 6 , wherein the printing unit includes a print head that ejects ink droplets onto the print medium.

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