JP2012152919A - Image recording apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image recording apparatus in which a sheet is unlikely to get stuck in a resupply conveyance path.SOLUTION: A printer section 11 includes: a conveyance path 65 for guiding the sheet in a first conveyance direction; a recording section 24 for recording an image in the sheet; an inverse conveyance path 67 which is formed inside the conveyance path 65, conveys the sheet, on one side of which the image is recorded, in a second conveyance direction, and guides the sheet to the recording section 24 again; and a pair of first rollers 44 which convey the sheet in the first conveyance direction or the second conveyance direction by normally rotating or reversely rotating. A pair of conveyance rollers 70 for conveying the sheet in the second conveyance direction are provided in the inverse conveyance path 67. The inverse conveyance path 67 includes: a straight line path 67A formed along a straight line for mutually connecting lip positions of the pair of first rollers 44 and the pair of conveyance rollers 70; and a second curved path 67B which are bent upward from the downstream of the straight line path 67A so as join the conveyance path 65.

Description

  The present invention relates to an image recording apparatus that records an image on a sheet, and more particularly to an image recording apparatus capable of recording an image on both sides of a sheet.

  2. Description of the Related Art Conventionally, an image recording apparatus that can record images on both sides of a sheet is known. In such an image recording apparatus, the sheet sent out from the paper feed tray is conveyed to the recording unit, and an image is recorded on the surface of the sheet in the recording unit. The sheet with the image recorded on the surface is switched back by the first roller pair on the downstream side of the recording unit. The switched-back sheet is conveyed to a refeed conveyance path provided below the recording unit and above the paper feed tray. The sheet conveyed to the resupply conveyance path is sent again from the resupply conveyance path to the recording unit by the second roller pair provided in the resupply conveyance path. The sheet that has reached the recording unit records an image on the back side by the recording unit in the same manner as when an image is formed on the front side. Thereafter, the sheet on which images are recorded on both sides is discharged to the discharge tray by the first roller pair.

  Patent Document 1 discloses an image forming apparatus in which a release arm and a roller arm are attached to rollers constituting a roller pair. In the image forming apparatus, when a jam occurs in the state where the sheet is held between the roller pair, the roller is moved via the roller arm in conjunction with the pulling operation of the sheet feeding tray from the apparatus. As a result, the nipping state of the sheet by the roller pair is released.

Japanese Patent No. 3423409

  In the image recording apparatus (image forming apparatus) as described above, at least a part of the path from the refeed conveyance path to the recording unit is often formed in a curved shape. When the curvature of the curved path is large in the image recording apparatus, the area occupied by the curved path becomes small inside the image recording apparatus. Therefore, in order to reduce the size of the image recording apparatus, it is desirable that the curvature of the resupply conveyance path is large, that is, the radius of curvature is small.

  However, when the sheet is conveyed along a curved path, the smaller the radius of curvature of the path, the greater the sheet conveyance resistance, that is, the force opposite to the sheet conveyance direction. The conveyance direction force transmitted from the roller and the force opposite to the conveyance direction transmitted from the curved path act as stresses, and the center periphery of the sheet is bent upward or downward to convey the sheet. It may not be possible. Further, the curved sheet may be clogged in the refeed conveyance path.

  Since the refeed conveyance path is configured with a minimum necessary space for conveying the sheet, it is difficult to visually recognize the sheet jammed inside from the outside. For example, when a sheet is torn inside the refeed conveyance path, it is difficult to find and take out a piece of the torn sheet.

  The sheet conveyed through the refeed conveyance path is in a state where an image has already been printed on one side. For this reason, the rigidity of the sheet is lowered by the moisture of the ink, and the possibility of the sheet becoming clogged is further increased.

  In general, small sheets such as postcards are thick and often have high rigidity. Since such a sheet is difficult to bend, the above-mentioned problem often does not occur, but a large conveying force is required instead. On the other hand, large sheets represented by A4 size and the like are often thinner than small sheets and are easy to bend. Therefore, the above-described problem is particularly serious in conveying a large sheet.

  The present invention has been made in view of the above problems, and an object thereof is to provide an image recording apparatus in which a sheet is not easily jammed in a refeed conveyance path, and an image recording apparatus capable of conveying any sheet. There is.

  (1) In the image recording apparatus of the present invention, a sheet can pass through, a first curved portion that makes a U-turn from below to the top, and a first curved portion that extends linearly from the first curved portion and extends in the first conveying direction. A first conveyance path having one straight line section, a recording section for recording an image on a sheet in the first straight line section of the first conveyance path, and the first conveyance path at a branch position downstream of the recording section in the first conveyance direction. Branching from the first straight line portion of the one conveyance path, and extending so as to merge with the first curved portion of the first conveyance path at the merging position on the upstream side in the first conveyance direction from the recording unit, A second conveyance path that guides in a second conveyance direction from the branch position toward the merging position, and a downstream side in the first conveyance direction from the branch position in the first linear portion of the first conveyance path; By rotating forward or reverse, the sheet is A first roller pair that conveys in one conveying direction or the second conveying direction and a pair of a driving roller and a driven roller that are opposed to each other in the second conveying path are provided to convey the sheet in the second conveying direction. The drive roller is centered on a second roller pair and a support shaft that is provided in the second conveyance path and is attached to the tip of the second roller, and that is disposed upstream of the drive roller in the second conveyance direction. Includes an arm that is rotatable between a first posture in contact with the driven roller and a second posture in which the driving roller is separated from the driven roller. The second conveyance path includes a second straight line portion formed along a direction connecting a first position where the first roller pair holds the sheet and a second position where the second roller pair holds the sheet; A second curved portion that is formed on the downstream side in the second transport direction from the second roller pair, and is curved from below to above inside the first curved portion and reaches the merging position.

  The sheet is conveyed on the straight portion of the second conveyance path (corresponding to the above-described refeed conveyance path) with the upstream side being nipped by the first roller pair and the downstream side being nipped by the second roller pair. The straight line portion is formed along a direction connecting the first position where the first roller pair holds the sheet and the second position where the second roller pair holds the sheet, so that the sheet follows the second transport direction. Then, the sheet is conveyed toward the second bending portion (corresponding to the above-described curved path) in a flat state. When the sheet is flat along the second conveyance direction, most of the conveyance force applied to the sheet from the first roller pair and the second roller pair is not converted into stress that curves the sheet. And efficiently transmitted to the downstream side of the sheet. Therefore, the sheet can be conveyed by a conveying force exceeding the force without being bent by receiving a force opposite to the conveying direction.

  When the second roller pair is attached to an arm having a fulcrum on the upstream side in the second conveyance direction as compared with the second roller pair, the conveyance amount of the first roller pair is larger than the conveyance amount of the second roller pair. Then, the arm rotates in a direction to separate the second roller pair by conveying the sheet. As a result, the force with which the second roller pair clamps the sheet decreases, so that the sheet is conveyed while sliding on the second roller pair. On the other hand, when the conveyance amount of the first roller pair is smaller than the conveyance amount of the second roller pair, the arm rotates in a direction in which the second roller pair is pressed by the rotation of the second roller pair. As a result, the force with which the second roller pair holds the sheet is increased, thereby preventing the conveyance force from being insufficient.

  (2) In a cross section orthogonal to the width direction of the second transport path, an imaginary straight line connecting the first position and the second position is a tangent to an arc along the second curved portion.

  When the first roller pair, the second roller pair, and the second bending portion are in such a positional relationship, the force in the direction opposite to the conveyance direction in the second bending portion is small, and the sheet can be obtained by a relatively small conveyance force. The curved portion can be conveyed.

  (3) The first roller pair is arranged in a plurality spaced apart along the width direction of the first transport path, and one of the pair of rollers is attached to the same shaft and rotated by the same drive source The plurality of second roller pairs are spaced apart from each other along the width direction of the second conveyance path, and one of the pair of rollers is attached to the same shaft and rotated by the same drive source. And the number of the first roller pairs is larger than the number of the second roller pairs.

  Depending on the number of roller pairs, the force with which the first roller pair and the second roller pair hold the sheet can be adjusted. Since the number of first roller pairs is larger than the number of second roller pairs, the force with which the first roller pair clamps the sheet can be made larger than the force with which the second roller pair clamps the sheet. By doing so, even if the conveyance amount of the first roller pair is larger than the conveyance amount of the second roller pair, the second roller pair slides the sheet in the conveyance direction, so the conveyance direction received by the sheet from the second roller pair The possibility of bending a large sheet is reduced by the force in the opposite direction. Here, the driving source in the present invention refers to a device that consumes energy such as electricity to generate a mechanical driving force, and includes a motor as an example.

  (4) The first roller pair and the second roller pair are rotated by different driving sources and have different sheet conveyance amounts per unit time.

  (5) The second bending portion includes at least one roller for guiding the sheet conveyed through the second bending portion to the downstream side in the second conveyance direction.

  By guiding the sheet by the roller, the frictional force generated on the sheet in the second bending portion is reduced, and the force in the direction opposite to the conveying direction can be reduced.

  (6) The distance from the first roller pair to the joining position in the second conveyance path is shorter than the length in the conveyance direction of the sheet having the longest conveyance direction in the second conveyance path, And the length of the conveyance direction conveyed in the said 2nd conveyance path is longer than the length of the conveyance direction of the shortest sheet | seat.

  In a general home or office image recording apparatus, an example of a sheet having the longest length in the conveyance direction is, for example, A4 size recording paper. An example of the sheet having the shortest length in the conveying direction is an L-size recording sheet used for printing a photograph, for example. The A4 size recording sheet is conveyed through the second curved portion with the upstream side and the downstream side being sandwiched between the first roller pair and the second roller pair until the leading end reaches the joining position. On the other hand, the L-size recording paper is in a state where the trailing edge of the recording paper has passed through the first roller pair at least downstream of the second curved portion, and the second curved portion is moved only by the conveying force of the second roller pair. Be transported. Since a small recording paper represented by L size is generally difficult to bend, the second curved portion can be stably conveyed by only one roller pair.

  (7) The sheet conveyance amount by the first roller pair per unit time is larger than the sheet conveyance amount by the second roller pair.

  The conveyance amount of the first roller pair can be made larger than the conveyance amount of the second roller pair, and the first roller pair can be used as the main conveyance means in the second conveyance path. Thereby, conveyance of a large sheet represented by A4 size can be stabilized.

  In the present invention, since the second conveyance path has the linear portion, the conveyance force of the first roller pair and the second roller pair is efficiently transmitted to the downstream side of the sheet, and the conveyance of the sheet is stabilized. Further, the possibility that the curved sheet is jammed in the second conveyance path can be reduced.

FIG. 1 is a perspective view of a multifunction machine 10 as an example of an embodiment of the present invention. FIG. 2 is a longitudinal sectional view schematically showing the internal structure of the printer unit 11. FIG. 3 is a front view schematically showing the first roller pair 44 and the transport roller pair 70. FIG. 4 is a longitudinal sectional view schematically showing the relationship between the straight path 67A and the second curved path 67B. FIG. 5 is a diagram showing a part of the flow of double-sided image recording in the printer unit 11. FIG. 6 is a diagram showing a part of the flow of double-sided image recording in the printer unit 11. FIG. 7 is a diagram showing a part of the flow of double-sided image recording in the printer unit 11. FIG. 8 is a diagram illustrating a difference in the conveyance method depending on the size of the recording paper. FIG. 9 is a vertical cross-sectional view schematically showing a second curved path 67B according to a modification of the multifunction machine 10.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. The embodiment described below is merely an example of the present invention, and it is needless to say that the embodiment of the present invention can be changed as appropriate without departing from the gist of the present invention. In the following description, the vertical direction 7 is defined with reference to a state in which the multifunction machine 10 is installed (the state shown in FIG. 1), and the side where the opening 13 is provided is the front side (front side). 8 is defined, and a left-right direction 9 is defined when the multifunction machine 10 is viewed from the front side (front side).

  As shown in FIG. 1, the multifunction machine 10 is generally formed in a thin rectangular parallelepiped, and a printer unit 11 of an ink jet recording system is provided at the lower part. The multifunction machine 10 has various functions such as a facsimile function and a print function. The print function has a double-sided image recording function for recording images on both sides of the recording paper. The presence or absence of functions other than the print function is arbitrary. The printer unit 11 includes a casing (housing) 14 having an opening 13 formed in the front, and a tray 20 (see FIG. 2) on which recording papers of various sizes (an example of the sheet of the present invention) can be placed. It can be inserted and removed from the opening 13 in the front-rear direction 8. That is, the tray 20 can be attached to and removed from the multifunction machine 10.

[Configuration of Printer Unit 11]
As shown in FIG. 2, the printer unit 11 is provided above the tray 20 and picks up and feeds recording paper from the tray 20, and is fed by the paper feeding unit 15. An ink jet recording type recording unit 24 (an example of the recording unit of the present invention) that discharges ink droplets onto a recording sheet and records an image on the recording sheet, a path switching unit 41, and the like are provided. The recording unit 24 is not limited to the ink jet system, and various recording systems such as an electrophotographic system can be applied.

[Paper Feeder 15]
As shown in FIG. 2, the paper feeding unit 15 is provided above the tray 20 and below the recording unit 24. The paper feed unit 15 includes a paper feed roller 25, a paper feed arm 26, and a drive transmission mechanism 27. The paper feed roller 25 is pivotally supported at the tip of the paper feed arm 26. The paper feed arm 26 rotates in the direction of an arrow 29 around a support shaft 28 (an example of the same shaft of the present invention) provided at the base end. Thereby, the paper feed roller 25 can be brought into contact with and separated from the tray 20. That is, the paper feed roller 25 can come into contact with the recording paper placed on the tray 20. The sheet feeding roller 25 is rotated by a driving force transmitted from a sheet feeding motor (not shown) by a drive transmission mechanism 27 in which a plurality of gears are engaged. The paper feed roller 25 is in contact with the uppermost recording paper among the recording papers stacked on the tray 20, and separates the recording paper from the other recording papers to be described below. Supply to curved path 65A.

[Conveyance path 65]
As shown in FIG. 2, inside the printer unit 11, there is a conveyance path 65 (first conveyance of the present invention) from the front end (rear end) of the tray 20 through the recording unit 24 to the paper discharge holding unit 79. An example of a path) is formed. The conveyance path 65 includes a first curved path 65A (an example of the first curved section of the present invention) formed between the leading end of the tray 20 and the recording unit 24, and a period from the recording unit 24 to the paper discharge holding unit 79. The paper discharge path 65B (an example of the first straight line portion of the present invention) formed in the above.

  The first curved path 65 </ b> A is a curved path extending from the vicinity of the upper end of the separation inclined plate 22 provided on the tray 20 to the recording unit 24. The first curved path 65 </ b> A is generally formed in an arc shape centering on the inside of the printer unit 11. The recording paper fed from the tray 20 travels along the first curved path 65A in the first conveyance direction (the direction indicated by the one-dot chain line in FIG. 2) in the first conveyance direction (the direction of the arrow attached to the one-dot chain line in FIG. 2). , Corresponding to the first conveying direction of the present invention), is U-turned, and is guided directly below the recording unit 24. The first curved path 65A is partitioned by an outer guide member 18 and an intermediate guide member 17 facing each other with a predetermined interval. Note that the outer guide member 18 and the intermediate guide member 17 and guide members 19, 31, 32, 33, 82, and 83, which will be described later, all extend in the direction perpendicular to the plane of FIG. 2 (the left-right direction 9 in FIG. 1). Has been issued.

  The paper discharge path 65 </ b> B is a linear path extending from directly below the recording unit 24 to the paper discharge holding unit 79. The recording paper is guided through the paper discharge path 65B in the first transport direction. The paper discharge path 65B is formed by the recording unit 24 and the platen 42 facing each other at a predetermined interval at a location where the recording unit 24 is provided, and at a location where the recording unit 24 is not provided. The upper guide member 82 and the lower guide member 83 are opposed to each other at a predetermined interval.

  A branch position 36 (an example of a branch position according to the present invention) exists downstream of the recording unit 24 in the first transport direction. At the time of double-sided image recording, the recording paper conveyed through the paper discharge path 65B is switched back downstream of the branch position 36 and directed to a reverse conveyance path 67 (an example of the second conveyance path of the present invention) described later. Are transported.

[Recording unit 24]
As shown in FIG. 2, the recording unit 24 is disposed above the tray 20. The recording unit 24 reciprocates in the left-right direction 9 (direction perpendicular to the paper surface in FIG. 2). A platen 42 for holding the recording paper horizontally is provided below the recording unit 24. In the process of reciprocating in the left-right direction 9, the recording unit 24 discharges ink supplied from an ink cartridge (not shown) from a nozzle 39 onto a recording sheet conveyed on the platen 42. As a result, an image is recorded on the recording paper in the conveyance path 65.

[Conveying rollers 45, 60, 62]
As shown in FIG. 2, a first transport roller 60 and a pinch roller 61 are provided between the downstream end of the outer guide member 18 and the intermediate guide member 17 in the first transport direction and the recording unit 24. The pinch roller 61 is disposed below the first transport roller 60 and is pressed against the roller surface of the first transport roller 60 by an elastic member such as a spring (not shown). The first conveyance roller 60 and the pinch roller 61 pinch the recording paper conveyed through the first curved path 65 </ b> A and send it onto the platen 42.

  A second transport roller 62 and a spur 63 are provided between the recording unit 24 and the upper guide member 82 and the lower guide member 83. The spur 63 is disposed above the second conveyance roller 62 and is pressed against the roller surface of the second conveyance roller 62 by an elastic member such as a spring (not shown). The second conveying roller 62 and the spur 63 pinch the recording sheet on which the image is recorded by the recording unit 24 and convey it to the downstream side in the first conveying direction.

  Each of the transport rollers 60 and 62 is rotated by a rotational driving force transmitted from a first transport motor (an example of a drive source of the present invention, not illustrated) via a drive transmission mechanism (not illustrated). The drive transmission mechanism is composed of a planetary gear or the like, and rotates each of the transport rollers 60 and 62 in one rotation direction regardless of whether the transport motor is rotated in the forward rotation direction or the reverse rotation direction. Thereby, the recording sheet is conveyed in the first conveying direction.

  Six third transport rollers 45 and spurs 46 are provided downstream of the branch position 36 in the first transport direction. As shown in FIG. 3A, the third transport roller 45 is mutually connected to a first drive shaft 58 (an example of the same shaft of the present invention) that extends in the left-right direction 9 (vertical direction in FIG. 2). Installed adjacent. The spurs 46 are attached to be adjacent to each other in parallel with the first drive shaft 58 above the third conveyance roller 45. The 3rd conveyance roller 45 and the spur 46 are arrange | positioned so that each may oppose the up-down direction 7, and may become a pair. A pair of a pair of third conveying rollers 45 and a spur 46 facing each other is referred to as a first roller pair 44 (an example of the first roller pair of the present invention). The spur 46 is urged downward in the vertical direction 9 by an elastic member such as a spring and is in pressure contact with the roller surface of the third transport roller 45. Each of the third conveying rollers 45, the spurs 46, and the first lip point 51 (an example of the first position of the present invention) with which they abut are shown as a single point in the direction perpendicular to the paper surface in FIG.

  The third conveyance roller 45 is driven to rotate in the normal rotation direction or the reverse rotation direction by receiving a driving force in the normal rotation direction from the first conveyance motor. For example, when single-sided recording is performed, the third transport roller 45 is rotated in the forward rotation direction. As a result, the recording sheet is nipped by the third conveying roller 45 and the spur 46 and conveyed downstream, and is discharged to the discharge holding unit 79. On the other hand, when double-sided recording is performed, the rotation direction of the third conveyance roller 45 is switched from the normal rotation direction to the reverse rotation direction with the third conveyance roller 45 and the spur 46 sandwiching the rear end portion of the recording paper. . Thereby, the recording sheet is conveyed in the direction opposite to the first conveyance direction, and is conveyed toward the reverse conveyance path 67 described later by the path switching unit 41 described below.

[Route switching unit 41]
As illustrated in FIG. 2, the path switching unit 41 is disposed downstream of the second transport roller 62 in the first transport direction and upstream of the branch position 36 in the first transport direction. The path switching unit 41 includes auxiliary rollers 47 and 48, a flap 49 and a support shaft 87.

  A support shaft 87 extending in the direction perpendicular to the plane of FIG. 2 (left and right direction 9 in FIG. 1) is provided on the frame of the printer unit 11 and the like. The flap 49 extends from the support shaft 87 to the downstream side in the first transport direction, and is rotatably supported by the support shaft 87. An auxiliary roller 47 and an auxiliary roller 48 are pivotally supported on the flap 49. Since the roller surfaces of the auxiliary rollers 47 and 48 are in contact with the recording surface of the recording paper, they are formed in a spur shape like the spur 63 and the spur 46.

  The flap 49 is configured such that its posture can be changed, and a discharge posture (posture indicated by a broken line in FIG. 2) positioned above the lower guide member 83 and an extended end portion 49 </ b> A below the branch position 36. It rotates between a reverse posture (posture indicated by a solid line in FIG. 2) entering the position. The recording paper that has passed through the recording unit 24 is further transported downstream in the first transport direction when the flap 49 is in the ejection posture, and is switched back and transported to the reverse transport path 67 when the flap 49 is in the reverse posture.

[Reverse conveying path 67]
As shown in FIG. 2, the reverse conveyance path 67 is branched from the paper discharge path 65 </ b> B at the branch position 36, passes through the lower side of the recording unit 24 and the upper side of the paper feeding arm 26, and is first than the recording unit 24. The first curved path 65A is merged at the upstream merging position 37 in the conveying direction (an example of the merging position of the present invention). The recording sheet is conveyed in the second conveyance direction (corresponding to the second conveyance direction of the present invention) on the reverse conveyance path 67. Here, the second conveyance direction is a direction from the branch position 36 toward the merging direction 37 in the reverse conveyance path 67 and indicates a direction indicated by a two-dot chain line with an arrow in FIG.

  The reverse conveyance path 67 is divided into a straight path 67A (an example of the second straight part of the present invention) and a second curved path 67B (an example of the second curved part of the present invention). The straight path 67A is a path linearly extending from the branch position 36. The straight path 67A is connected to a virtual straight line 53 (an example of a virtual straight line according to the present invention) connecting a first lip point 51 and a second lip point 52 where a fourth conveying roller 68 and a driven roller 69, which will be described later, come into contact. Are formed along. The straight path 67A is partitioned by the second guide member 32 on the upper side. The straight path 67 </ b> A is partitioned on the lower side by the first guide member 31 and the third guide member 33. The second guide member 32 and the first guide member 31 are provided with intermittent portions (not shown) for exposing a roller surface of a conveyance roller pair 70 described later to the straight path 67A.

  As shown in FIGS. 2 and 4, the second curved path 67B is a curved path that is continuous from the downstream end of the straight path 67A in the second conveyance direction, and is formed inside the first curved path 65A. Yes. The second curved path 67 </ b> B is curved upward from the lower side in the up-down direction 7 and reaches the joining position 37. The second curved path 67B is partitioned by the intermediate guide member 17 on the outer peripheral side. The second curved path 67 </ b> B is partitioned by the inner guide member 19 on the inner peripheral side.

  As shown in FIG. 4, in a plan view from the left-right direction 9, the surface on the second curved path 67 </ b> B side of the intermediate guide member 17 forms a virtual circle 54 along the second conveyance direction. The virtual straight line 53 forms a tangent to the virtual circle 54. Of the virtual circle 54, the overlapping portion with the intermediate guide member 17 is an example of the arc of the present invention.

  Of the recording sheets on which double-sided images are recorded, the longest sheet in the transport direction is an A4 size sheet, and the shortest sheet is a postcard size sheet. Both A4 size and postcard size recording sheets are conveyed through the conveyance path 65 and the reverse conveyance path 67 with the vertical direction as the conveyance direction. The distance from the first lip point 51 along the reverse conveyance path 67 to the joining position 37 is shorter than the length in the vertical direction (287 mm) of the A4 size and longer than the length in the vertical direction of the postcard size. However, the distance from the first lip point 51 to the joining position 37 along the reverse conveyance path 67 is appropriately changed based on the size of the recording paper corresponding to the printer unit 11.

[Fourth transport roller 68]
The reverse conveying path 67 is provided with two fourth conveying rollers 68 (an example of a driving roller of the present invention) and two driven rollers 69 (an example of a driven roller of the present invention). Each of the fourth conveying rollers 68 and the driven roller 69 are shown to be overlapped in the direction perpendicular to the paper surface in FIG. The driven rollers 69 are disposed below the recording unit 24 and above the fourth conveying roller 68, respectively. The driven roller 69 is pivotally supported by the second guide member 32 and is provided adjacent to the left-right direction 9.

  As shown in FIG. 3B, the two fourth transport rollers 68 are positioned below the driven roller 69 across the reverse transport path 67 and are attached adjacent to the left-right direction 9. Similar to the third transport roller 45, the fourth transport roller 68 is disposed at a position facing the driven roller 69. A pair of opposed pair of driven roller 69 and fourth transport roller 68 is referred to as a transport roller pair 70 (an example of a second roller pair of the present invention). The fourth transport roller 68 is pressed against the roller surface of the driven roller 69 by a coil spring (not shown) described later. The point where each driven roller 69 and the fourth conveying roller 68 come into contact is referred to as a second lip point 52 (an example of the second position of the present invention).

  As shown in FIGS. 3A and 3B, the number of conveyance roller pairs 70 is smaller than the number of first roller pairs 44. The lip force with which the conveying roller pair 70 holds the recording paper is set to be smaller than the lip force with which the first roller pair 44 holds the recording paper. The number of the conveyance roller pairs 70 and the first roller pairs 44 can be appropriately determined by those skilled in the art based on the optimum lip force for each roller pair.

  The fourth transport roller 68 receives a driving force in the forward / reverse rotation direction from the second transport motor (an example of a drive source of the present invention, not shown) through the second drive shaft 71, and is in the forward rotation direction or the reverse rotation direction. Is driven to rotate. In the present embodiment, the conveyance roller pair 70 has a reverse conveyance path by sandwiching a recording sheet between the fourth conveyance roller 68 and the driven roller 69 when the conveyance motor is rotated in the reverse direction. The recording sheet conveyed to 67 is conveyed in the second conveyance direction. The first transport motor and the fourth transport roller 68 are configured so that the amount of recording paper transported per unit time (hereinafter also referred to as transport speed) is faster than the transport speed of the third transport roller 45. The rotation of the second transport motor is controlled.

[Transfer arm 74]
As shown in FIG. 2, the transfer arm 74 (an example of the arm of the present invention) has a base end portion (front end portion) supported by the support shaft 28. As a result, the transfer arm 74 can rotate about the support shaft 28 as a rotation center axis (see FIG. 2). That is, in this embodiment, the rotation axis of the transport arm 74 is the same as the rotation axis of the paper feed arm 26. The rotation axes of the transport arm 74 and the paper feed arm 26 may be different.

  The second drive shaft 71 is rotatably attached to the tip of the transport arm 74. That is, the support shaft 28 is disposed in front of the fourth transport roller 68, in other words, on the upstream side in the second transport direction. The position of the support shaft 28 in the vertical direction 7 is below the reverse conveyance path 67. That is, the transport arm 74 extends rearward and obliquely upward from the support shaft 28 to the fourth transport roller 68. Two transport arms 74 are provided in the left-right direction 9 so as to be spaced apart from each other at a constant interval, and each transport arm 74 is provided with a second drive shaft 71.

  A coil spring (not shown) such as a double torsion spring is attached to the transfer arm 74. The transport arm 74 is urged to rotate in the direction of the arrow 30 in FIG. 2 by the elastic force of the coil spring. That is, the coil spring urges the transport arm 74 in the direction in which the fourth transport roller 68 contacts the driven roller 69. Thereby, the 4th conveyance roller 68 can press-contact with the driven roller 69 as mentioned above. From the above, the transport arm 74 takes the first posture in which the fourth transport roller 68 contacts the driven roller 69 (an example of the first posture of the present invention). Further, when the transport arm 74 is rotated downward, the fourth transport roller 68 takes a second posture (an example of the second posture of the present invention) in which the fourth transport roller 68 is separated from the driven roller 69.

  When the transport arm 74 is in the first posture, a part of the transport arm 74 and the fourth transport roller 68 is exposed to the straight path 67 </ b> A through the intermittent portion of the first guide member 31. The fourth transport roller 68 is pressed against the roller surface of the driven roller 69 as described above.

[Operation of Printer Unit 11]
As described above, at the time of double-sided image recording, the recording sheet is switched back to the reverse conveyance path 67 after being conveyed through the conveyance path 65. After the overall flow of double-sided image recording is described, more detailed operation in the reverse conveyance path 67 will be described. In each of the drawings to be referred to, the recording paper 90 is adjacent to a triangle and a rectangle each having “1” and “2” written therein. This means that the surface adjacent to the triangle in the recording paper 90 is distinguished as the first surface 93 and the surface adjacent to the quadrangle as the second surface 94.

[Flow of double-sided image recording]
First, the overall flow when images are recorded on both sides of a recording sheet will be described. The recording paper 90 set on the tray 20 is conveyed to the first curved path 65 </ b> A by the rotation of the paper supply roller 25. The recording sheet 90 having the first end 91, which is the leading end in the first transport direction, passes through the first curved path 65A, is sandwiched between the first transport roller 60 and the pinch roller 61, and the rotation of the first transport roller 60 causes the first transport roller 60 to rotate. The first surface 93 is sent to the platen 42 with the recording portion 24 facing (the state shown in FIG. 5A).

  An image is recorded by the recording unit 24 on the first surface 93 of the recording paper 90 that has passed through the platen 42. The downstream side of the recording sheet 90 that has passed through the platen 42 in the first conveyance direction is sandwiched between the second conveyance roller 62 and the spur 63. The downstream side of the recording sheet 90 in the first conveyance direction is conveyed by the rotation of the first conveyance roller 60 and the second conveyance roller 62.

  When the first end 91 of the recording paper 90 passes through the lower guide member 83, the downstream side of the recording paper 90 in the first transport direction pushes up the auxiliary roller 47, and the flap 49 is set in the discharging posture. The recording paper 90 is conveyed while maintaining the ejection posture of the flap 49 and is sandwiched between the first roller pair 44 (state (B) in FIG. 5). By the normal rotation of the first roller pair 44, the recording paper 90 is conveyed in the first conveyance direction to a position where the second end 92, which is the rear end in the first conveyance direction, passes through the auxiliary roller 47. That is, most of the recording paper 90 on the downstream side in the first conveyance direction is discharged to the paper discharge holding unit 79. When the second end 92 passes through the auxiliary roller 47, the force by which the recording paper 90 pushes up the flap 49 is weakened, and the flap 49 assumes a reverse posture. When the flap 49 is in the inverted posture, the recording paper 90 is pressed by the auxiliary roller 48, and the second end 92 faces the straight path 67A (state (A) in FIG. 6).

  When an image is printed on only one side of the recording paper 90, the first roller pair 44 maintains normal rotation until the second end 92, which is the rear end in the first transport direction, exceeds the first roller pair 44. The recording paper 90 on which the image is recorded on the first surface 93 is discharged to the paper discharge holding unit 79. On the other hand, at the time of double-sided image recording, the rotation of the first roller pair 44 is switched to reverse rotation, and the recording paper 90 is conveyed along the straight path 67A with the second end 92 being the leading end in the second conveying direction. . The recording paper 90 is sandwiched between the conveyance roller pair 70 and thereafter conveyed by the rotation of the first roller pair 44 and the conveyance roller pair 70 (state (B) in FIG. 6). The recording paper 90 enters the conveyance path 65 again after the second end 92 exceeds the joining position 37.

  The recording paper 90 is again sent onto the platen 42, but unlike the first conveyance, the second surface 94 of the recording paper 90 faces the recording unit 24 side, so an image is recorded on the second surface 94 ( The state of FIG.

  The recording paper 90 is transported along the transport path 65 in the same manner as the first transport, and is sandwiched between the first roller pair 44 (state (B) in FIG. 7). Unlike the first conveyance, the first roller pair 44 maintains normal rotation until the first end 91, which is the rear end in the first conveyance direction, exceeds the first roller pair 44. Accordingly, the recording paper 90 on which images are recorded on both sides is discharged to the discharge holding unit 79.

[Conveyance flow in reverse conveyance path 67]
Subsequently, a detailed flow from when the recording sheet switched back at the branch position 36 is conveyed through the reverse conveyance path 67 to the merge position 37 will be described below. A relatively large recording paper such as A4 size and a relatively small recording paper such as postcard size are different in the method of being conveyed in the reverse conveyance path 67. The flow of transporting each recording sheet will be described below.

  First, a flow in which a relatively large recording sheet such as A4 size is conveyed will be described. The recording sheet 90 having the second end 92 directed to the straight path 67A due to the reverse posture of the flap 49 is conveyed along the straight path 67A by the reverse rotation of the first roller pair 44. Since the straight path 67A is formed along the virtual straight line 53, the recording paper 90 is transported in a generally flat plane in the second transport direction. The recording sheet 90 is sandwiched between the conveyance roller pair 70 on the downstream side in the second conveyance direction and thereafter conveyed by the rotation of the first roller pair 44 and the conveyance roller pair 70. At this time, the conveyance speed of the first roller pair 44 is faster than the conveyance speed of the conveyance roller pair 70, and the force with which the first roller pair 44 clamps the recording paper is greater than the force with which the conveyance roller pair 70 clamps the recording paper 90. Is also strong. Accordingly, the recording paper 90 is transported by sliding the transport roller pair 70 in the second transport direction.

  The second end 92 of the recording paper 90 reaches the second curved path 67B. The intermediate guide member 17 converts a part of the force that the first roller pair 44 and the conveyance roller pair 70 convey the recording paper into a force directed upward of the second curved path 67B, and the recording paper 90 is curved upward. Then, it is conveyed to the merging position 37. Since the distance from the first lip point 51 to the merge position 37 along the reverse conveyance path 67 is shorter than the length in the vertical direction of the A4 size, the recording paper 90 has a second position until the second end 92 reaches the merge position 37. It is sandwiched and transported between the one roller pair 44 and the transport roller pair 70 (state (A) in FIG. 8).

  Subsequently, a flow of conveying a relatively small recording sheet such as a postcard size will be described. Even in a small recording sheet, the rough flow of conveyance is the same as that in a large recording sheet, but the following points are different. That is, since the distance from the first lip point 51 along the reverse conveyance path 67 to the merge position 37 is longer than the length in the vertical direction of the postcard size, the second end 92 of the recording paper 90 reaches the merge position 37. Until the first end 91 has passed the first roller pair 44. Therefore, while the second end 92 is conveyed at least on the downstream side of the second curved path 67B, the recording paper 90 is conveyed only by the conveying force of the conveying roller pair 70 (state (B) in FIG. 8).

[Operational effects of this embodiment]
The recording sheet is conveyed along the straight path 67A in a state of being flat along the second conveying direction. For this reason, most of the conveying force applied to the recording paper from the first roller pair 44 and the conveying roller pair 70 is efficiently converted to the downstream side in the second conveying direction without being converted into stress that causes the recording paper to bend. Is done. That is, the stiffness of the recording paper becomes stronger. Therefore, the recording paper can be transported by a transport force that exceeds the force in the direction opposite to the transport direction received from the intermediate guide member 17.

  Further, since the virtual straight line 53 forms a tangent to the virtual circle 54, it is possible to reduce the force in the direction opposite to the conveying direction that the recording sheet receives from the intermediate guide member 17.

  Further, since the number of the first roller pairs 44 is larger than the number of the conveyance roller pairs 70, the force with which the first roller pair 44 clamps the recording sheet is set larger than the force with which the conveyance roller pair 70 clamps the sheet. ing. Thereby, even if the conveyance speed of the first roller pair 44 is larger than the conveyance speed of the conveyance roller pair 70, the first roller pair 44 slides the sheet in the second conveyance direction, so that the sheet receives from the conveyance roller pair 70. The possibility that the recording paper is bent by the force in the direction opposite to the conveyance direction is reduced. By transporting the recording paper so as to slide with respect to the transport roller pair 70, the transport of the recording paper is stabilized.

  Further, the conveyance roller pair 70 is attached to the conveyance arm 74 with the upstream side in the second conveyance direction as a fulcrum with respect to the conveyance roller pair 70, so that the conveyance amount of the first roller pair 44 is the conveyance amount of the conveyance roller pair 70. In the case where the number is larger, the conveyance arm 74 is rotated in the direction opposite to the direction of the arrow 30 in FIG. As a result, the force with which the conveyance roller pair 70 clamps the recording paper is reduced, and the recording paper can easily slide on the first roller pair 44 pair. On the other hand, when the conveyance amount of the first roller pair 44 is smaller than the conveyance amount of the conveyance roller pair 70, the conveyance arm 74 rotates in the direction of the arrow 30 in FIG. As a result, the force with which the conveyance roller pair 70 holds the recording paper is increased, thereby preventing the conveyance force from being insufficient.

  A small recording sheet such as a postcard size is transported only by the transport force of the transport roller pair 70 while the leading end in the second transport direction is transported at least on the downstream side of the second curved path 67B. Smaller recording paper is strong and difficult to bend, so the conveying force of the roller is easily transmitted downstream. Therefore, the recording sheet is stably conveyed through the second curved portion only by the conveying force of the conveying roller pair 70.

  Since the recording paper is stably conveyed through the reverse conveyance path 67, the possibility that the recording paper is jammed in the reverse conveyance path 67 is reduced.

[Modification]
Variations of the above-described embodiment will be described below. As shown in FIG. 9, in this modification, a plurality of guide rollers 81 are provided so as to be exposed on the surface of the intermediate guide member 17 on the second curved path 67B side. Other configurations of the multifunction machine 10 are the same as those in the above-described embodiment.

  The guide roller 81 is molded from, for example, resin. The guide roller 81 is attached to a plurality of fixed shafts (not shown) that extend in the left-right direction 9 and is attached to the fixed shaft with play. That is, the guide roller 81 can rotate with low friction with respect to the fixed shaft. Both ends of the fixed shaft are supported by the intermediate guide member 17. The guide roller 81 may be attached to the inner guide member 19 so as to be exposed from the surface of the inner guide member 19 on the second curved path 67B side. The size, arrangement, and number of the guide rollers 81 can be appropriately determined by those skilled in the art according to the shape of the second curved path 67B and the recording paper to be conveyed.

  A part of the surface of the recording sheet conveyed through the second curved path 67 </ b> B is in sliding contact with the guide roller 81. When the recording sheet receives a force in the second conveyance direction, the guide roller 81 rotates and guides the recording sheet in the second conveyance direction.

  The guide roller 81 can reduce the area where the recording paper contacts the intermediate guide member 17. Since the contact area between the recording paper and the intermediate guide member 17 is reduced, the frictional force that the recording paper receives from the intermediate guide member 17 is reduced. Accordingly, the recording paper is stably conveyed along the second curved path 67B even with a small conveying force.

10. Multifunction machine (image recording device)
24: Recording unit 28: Support shaft (same shaft)
36 ... Branch position 37 ... Merge position 44 ... First roller pair 51 ... First lip point (first position)
52 ... second lip point (second position)
53 ... Virtual straight line 54 ... Virtual circle (arc)
58 ... 1st drive shaft (same shaft)
65 ... transport path (first transport path)
65A ... 1st curved path (1st curved part)
65B: paper discharge path (first straight line portion)
67... Reverse conveyance path (second conveyance path)
67A ... Straight path (second straight section)
67B ... 2nd curved path (2nd curved part)
68: Fourth conveying roller (driving roller)
68 .. Followed roller 70... Conveying roller pair (second roller pair)
74 ... Transfer arm (arm)
81 ... Guide roller (roller)
90 ... Recording paper (sheet)

Claims (7)

A first conveyance path through which a sheet can pass and having a first curved portion that makes a U-turn from below to above, and a first straight portion that extends linearly from the first curved portion and extends in the first conveyance direction;
A recording unit for recording an image on a sheet in the first linear portion of the first conveyance path;
The first conveyance is branched from the first linear portion of the first conveyance path at the downstream branch position in the first conveyance direction from the recording unit, and the first conveyance at the merging position in the upstream in the first conveyance direction from the recording unit. A second conveyance path that extends to merge with the first curved portion of the path and guides the sheet from the branch position to the second conveyance direction toward the merge position;
The sheet is provided on the downstream side of the first conveyance direction from the branch position in the first straight portion of the first conveyance path, and the sheet is conveyed in the first conveyance direction or the second conveyance direction by rotating forward or reverse. A first pair of rollers transported to
A pair of a driving roller and a driven roller are provided facing each other in the second conveying path, and a second roller pair for conveying the sheet in the second conveying direction;
The drive roller is attached to the tip of the second conveyance path, and the drive roller contacts the driven roller around a support shaft disposed upstream of the drive roller in the second conveyance direction. An arm that is rotatable between a first posture in contact and a second posture in which the drive roller is separated from the driven roller;
With
The second transport path is
A second linear portion formed along a direction connecting a first position where the first roller pair holds the sheet and a second position where the second roller pair holds the sheet;
An image recording having a second curved portion that is formed downstream of the second roller pair in the second conveying direction and is curved from below to above inside the first curved portion and reaches the merging position. apparatus. In a cross section orthogonal to the width direction of the second conveyance path,
The image recording apparatus according to claim 1, wherein an imaginary straight line connecting the first position and the second position is a tangent to an arc along the second curved portion. The first roller pair is arranged in a plurality spaced apart along the width direction of the first transport path, one of the pair of rollers is attached to the same shaft and rotated by the same drive source,
The second roller pair is arranged in a plurality spaced apart along the width direction of the second transport path, one of the pair of rollers is attached to the same shaft and rotated by the same drive source,
The image recording apparatus according to claim 1, wherein the number of the first roller pairs is larger than the number of the second roller pairs.   4. The image recording apparatus according to claim 1, wherein the first roller pair and the second roller pair are rotated by different driving sources and have different sheet conveyance amounts per unit time. 5. .   5. The image recording apparatus according to claim 1, wherein the second bending portion includes at least one roller that guides a sheet conveyed through the second bending portion to a downstream side in the second conveyance direction. 6.   The distance from the first roller pair to the merging position in the second conveying path is shorter than the length in the conveying direction of the longest sheet in the conveying direction conveyed on the second conveying path, and the first 6. The image recording apparatus according to claim 1, wherein a length in a conveyance direction conveyed along the two conveyance paths is longer than a length in a conveyance direction of the shortest sheet.   The image recording apparatus according to claim 1, wherein a sheet conveyance amount by the first roller pair in a unit time is larger than a sheet conveyance amount by the second roller pair.

Images