Medium conveying device and printing apparatus

Abstract

The invention provides a medium conveying device and a printing device which can reduce variation of tension applied to a medium. A medium transport device (100) is provided with: a medium support unit (101) that supports a medium (M) to be transported; a winding unit (109) that winds the medium (M); a tension rod (103) that applies tension to the medium (M) between the medium support section (101) and the winding section (109); an arm part (105) which supports the tension rod (103) at one end; a rotating part (107) that rotatably supports the other end of the arm part (105); and a power source (106) for applying a force for rotating the arm section (105), the power source (106) applying a force to the arm section (105) so as to have a change amount opposite to the sign of the change amount of the moment (Wm) formed by the weight of the tension bar (103) and the arm section (105).

Description

Technical Field

[0001] The present invention relates to a medium conveying device and a printing device. Background Art

[0002] Conventionally, a medium conveying device that winds a continuous document-like medium such as a web into a cylindrical body has been known. In such a device, there is a device provided with a tension bar in order to improve the winding accuracy of the medium. For example, in Patent Document 1, a printing device that applies tension to a medium by swinging an arm is disclosed.

[0003] However, in the device described in Patent Document 1, there is a problem that the tension applied to the medium easily fluctuates. Specifically, the arm swings by its own weight, and thus the web as the medium is bent like a "く" character and tension is applied. That is, the strength of the applied tension depends on the masses of the arm and the tension bar. Therefore, according to the position of the arm during the swinging process, the degree of bending of the web changes, and thus the tension easily fluctuates. When the tension fluctuates, sometimes the winding accuracy decreases, and there may be defective conditions such as winding misalignment. That is, there is a need for a medium conveying device that reduces fluctuations in the tension applied to the medium.

[0004] Patent Document 1: Japanese Patent Application Laid-Open No. 2007-268824 Summary of the Invention

[0005] The medium conveying device is characterized by including: a medium support portion that supports the conveyed medium; a winding portion that winds the medium; a tension bar that applies tension to the medium between the medium support portion and the winding portion; an arm portion that supports the tension bar at one end; a rotating portion that rotatably supports the other end of the arm portion; and a power source that applies a force for rotating the arm portion, and the power source applies the force in such a manner that a change amount becomes a change amount having a sign opposite to that of a change amount of a moment formed by the self-weights of the tension bar and the arm portion.

[0006] The printing device is characterized by including: a printing portion that performs printing on a medium; a medium support portion that supports the conveyed medium; a winding portion that winds the medium; a tension bar that applies tension to the medium between the medium support portion and the winding portion; an arm portion that supports the tension bar at one end; a rotating portion that rotatably supports the other end of the arm portion; and a power source that applies a force for rotating the arm portion, and the power source applies the force in such a manner that a change amount becomes a change amount having a sign opposite to that of a change amount of a moment formed by the self-weights of the tension bar and the arm portion. Brief Description of the Drawings

[0007] Figure 1 It is a schematic diagram showing the structure of the printing apparatus according to the first embodiment.

[0008] Figure 2 It is a perspective view showing the appearance of the printing apparatus.

[0009] Figure 3 It is a side view showing the structure of the power source, the rotating part, the arm part, etc.

[0010] Figure 4 It is a perspective view showing the arrangement of the power source, the rotating part, the arm part, etc.

[0011] Figure 5 It is a graph showing the relationship between the operating angle of the arm part and various torques.

[0012] Figure 6 It is a schematic diagram showing the structure of the rotating part, the power source, etc. according to the second embodiment.

[0013] Figure 7 It is a graph showing the relationship between the operating angle of the arm part and various torques. Detailed Embodiment

[0014] In the following-described embodiments, a medium conveyance device and a printing apparatus including the medium conveyance device are illustrated and described with reference to the drawings. The printing apparatus of the following embodiments is a large-format printer that prints on a continuous sheet-like thin film. In addition, the medium conveyance device of the present invention is not limited to being provided in the printing apparatus, and the printing apparatus of the present invention is not limited to the following structure.

[0015] In the following figures, the XYZ axes are marked as mutually orthogonal coordinate axes, the direction indicated by each arrow mark is set as the + direction, and the direction opposite to the + direction is set as the - direction. When the printing apparatus is disposed on a horizontal plane, the -Z direction is the vertical direction. In the following description, the +Z direction is set as the upper side and the -Z direction is set as the lower side. In the following figures, for ease of illustration, the sizes of the respective components are different from the actual ones.

[0016] 1. First Embodiment

[0017] As Figure 1 shown, the printing apparatus 1 according to the present embodiment includes a structural component 10, an unwinding unit 20, medium support members 30, 50, a conveyance unit 40, a printing unit 60, a blowing unit 80, a medium conveyance device 100, and a housing (not shown). In addition, the printing apparatus 1 also includes a control unit (not shown). The control unit comprehensively controls the operation of each structure of the printing apparatus 1 including the medium conveyance device 100. The medium conveyance device 100 is an example of the medium conveyance device of the present invention.

[0018] In Figure 1 , the housing for accommodating the printing unit 60 and the like is omitted for the sake of illustration. In the following description of Figure 1 , unless otherwise specified, the state observed from the -X direction is described.

[0019] The printing apparatus 1 manufactures a printed matter by attaching ink to a continuous sheet-like medium M, which is a form of document. In the printing apparatus 1, the medium M is unwound from a roll body R1 serving as an original roll and becomes a printed matter, and the printed matter is wound up to become a roll body R2.

[0020] The control unit includes hardware such as a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The control unit controls the printing apparatus 1 by the CPU executing a predetermined control program. The ROM is a non-volatile storage device and stores the control program executed by the CPU and the data processed by the control program. The RAM constitutes the working area of the CPU. The CPU controls the printing apparatus 1 by expanding the control program read from the ROM and the like in the RAM and executing the expanded control program.

[0021] The movement path of the medium M from when it is unwound from the roll body R1 until it is wound up as the roll body R2 is defined as the conveyance path. In Figure 1 , the conveyance path is indicated by a single-dot chain line. In the conveyance path, the original roll side of the medium M is referred to as the upstream, and the advancing side of the medium M and the printed matter is referred to as the downstream. On the conveyance path, in the direction from the upstream to the downstream, the unwinding unit 20, the medium support member 30, the conveyance unit 40, the medium support member 50, the printing unit 60, the medium conveyance device 100, and the air supply unit 80 are arranged in the above order. In addition, the direction in which the medium M advances from the upstream to the downstream on the conveyance path is referred to as the conveyance direction.

[0022] The structural member 10 is a frame that supports the above-described respective structures of the printing apparatus 1. The structural member 10 is assembled from a plurality of metal plate members, tubular members, and the like. In the structural member 10, casters or setting members may also be arranged at the portion in contact with the floor below.

[0023] The unwinding unit 20 is provided with a reel body holding unit 21. The unwinding unit 20 is arranged in the -Y direction below the printing device 1. The reel body holding unit 21 supports the reel body R1 in a rotatable manner about an axis along the X-axis. The medium M is pulled by the conveying unit 40 and unwound and supplied downstream from the reel body R1. The reel body R1 is detachable from the printing device 1. The medium M is conveyed by the conveying unit 40 from the reel body holding unit 21 substantially upward and advances toward the medium support member 30.

[0024] The medium M is appropriately selected according to the type of ink attached to the medium M, the use of the printed matter, etc. In the printing device 1, since so-called soft solvent ink is used as the ink, a thin sheet made of polyvinyl chloride or the like can be applied as the medium M.

[0025] The medium support member 30 has a substantially arc-shaped curved surface and supports the conveyed medium M. The conveying direction of the medium M is changed from substantially upward to substantially the +Y direction through the above-mentioned curved surface of the medium support member 30. The medium M contacts and slides on the above-mentioned curved surface of the medium support member 30 and is conveyed. The medium M advances from the medium support member 30 toward the conveying unit 40.

[0026] Although not shown in the figure, the medium support member 30 is internally provided with an electric heater for heating the medium M. This electric heater preheats the medium M before the ink is attached. Thereby, the fixing property, solubility, etc. of the ink with respect to the medium M are improved.

[0027] The conveying unit 40 is provided with conveying rollers 41 and 42. The conveying rollers 41 and 42 are paired and their sides are in contact with each other. The conveying roller 41 is arranged below the conveying path, and the conveying roller 42 is provided above the conveying path. The conveying rollers 41 and 42 rotate about axes along the X-axis respectively.

[0028] The conveying roller 41 is driven to rotate by a driving motor (not shown). The conveying roller 42 is a driven roller and rotates in the direction opposite to that of the conveying roller 41 by the rotation of the conveying roller 41. When the conveying roller 41 rotates counterclockwise, the conveying roller 42 rotates clockwise. Thereby, the medium M is sandwiched between the conveying rollers 41 and 42 and conveyed downstream. Moreover, the medium M advances toward the medium support member 50.

[0029] The medium support member 50 is a member constituting a so-called impression plate. The upper surface of the medium support member 50 supports the medium M along the XY plane. In the medium support member 50, the conveying direction of the medium M is the +Y direction. The upward-facing surface of the medium M is the printing surface.

[0030] Although not shown in the drawings, the medium support member 50 incorporates an electrothermal heater for heating the medium M. This electrothermal heater heats the medium M when the ink adheres thereto. Thereby, the fixing property, solubility, etc. of the ink with respect to the medium M are improved, and volatile components such as solvents contained in the ink are made easier to volatilize.

[0031] The printing unit 60 performs printing on the medium M. The printing unit 60 includes a head 61 and a carriage 62. The printing unit 60 is disposed above the medium support member 50. The carriage 62 is supported above the structural member 10 so as to be reciprocally movable along the X-axis. The above-described reciprocal movement is driven by a carriage motor (not shown). The carriage 62 supports the head 61 above the medium support member 50.

[0032] The head 61 causes the ink to adhere to the printing surface of the medium M supported on the upper surface of the medium support member 50. The head 61 reciprocally moves along the X-axis together with the carriage 62 within a range including a region that faces the medium support member 50 in the vertical direction.

[0033] Although not shown in the drawings, a nozzle surface is disposed on the downward-facing surface of the head 61. A plurality of nozzle rows are provided on the nozzle surface. Each nozzle row is composed of a plurality of nozzles that eject ink. For each nozzle row, inks of various colors such as black, blue-green, yellow, magenta, etc. are separately supplied from an ink storage container (not shown). Inks of various colors are ejected from each nozzle row toward the printing surface of the medium M.

[0034] As described above, the ink applied in the printing apparatus 1 is a soft solvent ink. The soft solvent ink is a solvent ink that contains, for example, an alcohol ether solvent or a lactone solvent as a main solvent without intentionally added water. In addition, the ink ejected from the head 61 may also contain a treatment liquid and a transparent ink without a color material, etc.

[0035] At the medium support member 50, while conveying the medium M in the +Y direction, the head 61 and the carriage 62 reciprocally move along the X-axis together. At this time, by causing the ink to adhere to the printing surface of the medium M at an arbitrary timing, an image such as a painting, a photograph, text, a pattern, etc. is printed on the medium M. The medium M after printing is pulled by the medium conveying device 100 and advances toward the downstream medium conveying device 100 and the air supply unit 80.

[0036] The medium conveying device 100 includes a medium support portion 101, a heating portion 102, a tension rod 103, an arm portion 105, a rotating portion 107, a winding portion 109, and a power source 106 (described later).

[0037] Each structure of the medium conveyance device 100 is supported by the structural member 10 and is arranged in the +Y direction of the printing device 1. In the medium conveyance device 100, the medium support portion 101, the tension bar 103, and the winding portion 109 are arranged in this order toward the conveyance direction.

[0038] The medium support portion 101 has a curved surface that is a surface for supporting the medium M, and supports the conveyed medium M. The curved surface of the medium support portion 101 faces substantially upward in the medium support portion 101. The medium M contacts and slides on the curved surface of the medium support portion 101 and is conveyed. In the direction along the X axis, the length of the curved surface of the medium support portion 101 is longer than the length of the medium M. The conveyance direction of the medium M changes from the +Y direction to the +Y direction and slightly downward through the curved surface of the medium support portion 101.

[0039] The medium support portion 101 has a pair of side walls 101p. The side walls 101p are respectively arranged at the end portions in the +X direction and the -X direction of the medium support portion 101. Each side wall 101p is a substantially plate-like member, for example, formed of a metal plate. Each side wall 101p includes a surface that intersects the curved surface of the medium support portion 101 along the YZ plane.

[0040] The medium support portion 101 has a heating portion 102. The heating portion 102 is an electric heater. The heating portion 102 heats the medium M supported on the curved surface of the medium support portion 101. The heating portion 102 is arranged inside the curved surface of the medium support portion 101. The heating portion 102 promotes the volatilization of the volatile components contained in the ink attached to the medium M by heating. Thereby, when the medium M is wound into a roll body R2 by the winding portion 109, it is possible to prevent the ink components from adhering to other portions.

[0041] The air supply portion 80 supplies air to the printing surface of the medium M to assist the volatilization of the above-mentioned volatile components. The air supply portion 80 is supported by the structural member 10 above the conveyance path of the medium support portion 101. The air supply portion 80 blows air over the entire range of the medium M along the X axis.

[0042] By the heating of the heating portion 102 and the air supply of the air supply portion 80, the drying of the ink attached to the medium M is promoted. Therefore, the medium M can be wound by the downstream winding portion 109. The medium M is traction-conveyed by the winding portion 109 and advances toward the tension bar 103.

[0043] The tension rod 103 applies tension to the medium M between the medium support portion 101 and the winding portion 109 in the conveying path. The tension rod 103 is a substantially cylindrical member, and the longitudinal direction of the cylinder is arranged along the X axis. The ends of the tension rod 103 in the -X direction and the ends in the +X direction are supported by the arm portions 105, respectively. The tension rod 103 is supported by a pair of arm portions 105, and protrudes slightly downward from the medium support portion 101 in the +Y direction.

[0044] In a configuration where the tension rod 103 is not provided, the medium M is conveyed from the end of the medium supporting portion 101 in the +Y direction to the winding portion 109 substantially below. In contrast, in the printing device 1, the tension rod 103 protrudes downward and slightly in the +Y direction from the medium supporting portion 101. Therefore, the medium M is conveyed while being pressed in the substantially +Y direction by the tension rod 103. Thus, the medium M is wound up by the winding portion 109 while tension is applied thereto.

[0045] The surface of the tension rod 103 corresponding to the side of the cylinder is formed to have low friction resistance and is smooth. Therefore, the medium M slides on the side of the tension rod 103 while being tensioned. The side of the cylinder of the tension rod 103 may be covered with a sheet-like member so as not to directly contact the medium M. In addition, the tension rod 103 does not rotate relative to the arm 105.

[0046] Each arm 105 is a substantially rod-shaped member and supports the tension rod 103 at one end substantially in the +Y direction when the tension rod 103 functions. The other end substantially in the -Y direction of each arm 105 is rotatably supported by the rotation unit 107 .

[0047] In a plan view from above, the distance between one end and the other end of each arm portion 105, that is, the length is shorter than the length along the conveyance direction of the medium supporting portion 101. Therefore, the arm portion 105 and the like are relatively small.

[0048] The rotating parts 107 are arranged corresponding to the respective arms 105. Specifically, the rotating parts 107 are provided on the side walls 101p in the +X direction and the side walls 101p in the -X direction in the medium support part 101. Therefore, the rotating parts 107 are unlikely to interfere with the medium M, and the medium conveying device 100 can be miniaturized.

[0049] Here, the rotating portion 107 is not limited to being arranged on the side wall 101p. The rotating portion 107 may also be arranged on the structural member 10. Specifically, for example, the rotating portion 107 may also be arranged at the lower part of the structural member 10. In such a case, in order to apply tension to the medium M between the medium support portion 101 and the winding portion 109, the arm portion 105 is extended.

[0050] Each rotating part 107 rotates clockwise and counterclockwise about the vicinity of the other end of the arm part 105 as the center of rotation by the force applied by the power source 106 described later. Moreover, one end of each arm part 105 rotates clockwise and counterclockwise while supporting the tension rod 103. Thereby, the position of the tension rod 103, particularly the protruding distance from the medium support part 101 in the +Y direction, changes, and thus the strength of the tension applied to the medium M is adjusted. Specifically, when the tension rod 103 rotates clockwise, the protruding distance of the tension rod 103 from the medium support part 101 in the +Y direction becomes longer, and the medium M is pushed in the +Y direction and a stronger tension is applied. In addition, when the tension rod 103 rotates counterclockwise, the protruding distance of the tension rod 103 from the medium support part 101 in the +Y direction becomes shorter, the force pushing the medium M in the +Y direction weakens, and the applied tension decreases.

[0051] Each rotating part 107 is arranged at a position closer to the downstream end in the +Y direction than the upstream end in the -Y direction of the medium support part 101 with respect to the conveyance direction of the medium M. Thereby, compared with the case where each rotating part 107 is arranged closer to the upstream end of the medium support part 101, the length of the arm part 105 can be shortened.

[0052] The conveyance direction of the medium M is changed from downward in the +Y direction to downward in the -Y direction by the tension rod 103. The medium M advances toward the winding part 109 via the tension rod 103.

[0053] The winding part 109 winds the medium M into a roll body R2. The winding part 109 includes a roll body holding part 109a. The winding part 109 is arranged at the +Y direction below the printing device 1. The roll body holding part 109a rotates counterclockwise by the rotational drive of a drive motor (not shown) and winds the medium M into a roll body R2. At this time, the roll body R2 rotates about the axis along the X axis.

[0054] When the medium M is wound into a roll body R2, the winding accuracy is improved by the tension applied by the tension rod 103. Therefore, the position deviation at both ends of the medium M along the X axis can be reduced, and the above-described roll body R2 with relatively neat both ends can be obtained. In addition, by the applied tension, the gap between the overlapping media M can be reduced, and a dense roll body R2 can be obtained. The strength of the tension applied to the medium M has an appropriate range. The above tension is appropriately set according to the type, size, etc. of the medium M.

[0055] In the above manner, the medium M as a printed matter becomes a roll body R2. The roll body R2 can be detached from the printing device 1 in the substantially +Y direction.

[0056] As Figure 2As shown, side walls 101p are respectively disposed at the -X direction end portion and the +X direction end portion of the medium support portion 101. A rotating portion 107, an arm portion 105, and a power source 106 (not shown) are disposed on each side wall 101p. Both ends of the tension rod 103 in the direction along the X-axis are supported by the arm portion 105. In addition, Figure 2 illustrations of other structures including the housing of the printing apparatus 1 and the printing portion 60 are omitted.

[0057] As Figure 3 shown, a power source 106 is attached to the rotating portion 107. The rotating portion 107 has gears 107a and 107b that serve as speed reducers. In addition, Figure 3 This is a view for observing the -X direction side wall 101p of the medium conveying device 100 from the -X direction. On the +X direction side wall 101p of the medium conveying device 100, each structure is arranged in a manner symmetric with respect to the plane along the YZ plane.

[0058] In the following description, the structure on the -X direction side described above is taken as a representative example for explanation, and the description of the structure on the +X direction side is omitted. In addition, in the following Figure 3 and Figure 4 description, unless otherwise specified, the state observed from the -X direction is described.

[0059] The power source 106 applies a force to rotate the arm portion 105. The power source 106 is disposed outside the -X direction side wall 101p, that is, on the -X direction side. Therefore, the medium M is not likely to interfere with the power source 106, and the medium conveying device 100 can be miniaturized. In addition, since the power source 106 is disposed outside the side wall 101p, the adjustment and replacement of the power source 106 can be easily performed.

[0060] The power source 106 is a spring. As the spring, a helical spring, a torsion spring, a leaf spring, etc. can be cited. In the present embodiment, a helical spring is applied as the spring of the power source 106. By using a spring as the power source 106, the elastic force of the spring is used to apply a force to rotate the arm portion 105. Therefore, a driving mechanism such as a motor is not required, and the power source 106 can be made into a simple and inexpensive structure.

[0061] One end portion of the power source 106 is mounted on the gear 107a through an opening (not shown) of the side wall 101p. The other end portion of the power source 106 is mounted on the side wall 101p through a support member 106a.

[0062] The power source 106 is not limited to a spring as long as it can apply a force to rotate the arm portion 105. For the power source 106, for example, a damper, a spring, a motor, etc. can be applied.

[0063] The gears 107a and 107b are arranged inside the side wall 101p on the -X direction side, that is, on the +X direction side. By arranging the gears 107a and 107b inside the side wall 101p, the components arranged outside the side wall 101p can be reduced, and the situation where the length of the medium conveying device 100 in the X direction becomes larger can be suppressed. The gears 107a and 107b are rotatably supported by the side wall 101p respectively on the axis along the X axis. The gears 107a and 107b are arranged adjacent to each other in the direction along the Y axis and mesh with each other.

[0064] The gear 107b penetrates the side wall 101p and is directly connected to the other end in the substantially -Y direction of the arm portion 105 in a state where the tension rod 103 functions. The gear 107b is driven to rotate by the rotation of the gear 107a and rotates around the central axis AR along the X axis. The arm portion 105 rotates in conjunction with the rotation of the gear 107b and rotates with the central axis AR as a fulcrum. By the rotation of the arm portion 105, the tension rod 103 is displaced like a pendulum with the central axis AR as a fulcrum.

[0065] On the outside of the side wall 101p on the -X direction side, that is, on the -X direction side, a locking member 101s and stoppers 108a and 108b are provided. The locking member 101s is arranged corresponding to one end of the power source 106. The stoppers 108a and 108b are arranged corresponding to the arm portion 105. In addition, components such as the power source 106 arranged outside the side wall 101p can also be covered with a cover.

[0066] When the gear 107a rotates counterclockwise, the locking member 101s abuts against one end of the power source 106. Thereby, further counterclockwise rotation in the gear 107a is restricted.

[0067] The stoppers 108a and 108b restrict the rotation of the arm portion 105 exceeding a certain range. Specifically, when the arm portion 105 rotates counterclockwise significantly and the arm portion 105 is received under the medium support portion 101, etc., the stopper 108a abuts against the arm portion 105. Thereby, further counterclockwise rotation in the arm portion 105 is restricted. For example, the above-mentioned receiving operation of the arm portion 105 is performed when disassembling a non-illustrated winding cylinder R2 from the printing apparatus 1, etc.

[0068] The stopper 108b restricts the clockwise rotation of the arm portion 105. When the arm portion 105 rotates clockwise, the arm portion 105 abuts against the stopper 108b. Thereby, further clockwise rotation in the arm portion 105 is restricted. In addition, in Figure 3 the state where the arm portion 105 abuts against the stopper 108b is shown.

[0069] As Figure 4As shown, when the tension rod 103 is functioning, the power source 106 tends to contract in the direction marked by the blank arrow. Thus, the gear 107a is forced to rotate counterclockwise. Since the gear 107a meshes with the gear 107b, the rotational driving force of the gear 107a is transmitted to the gear 107b, and the gear 107b rotates clockwise. In conjunction with the rotation of the gear 107b, the arm 105 rotates clockwise with the central axis AR as the fulcrum. That is, the power source 106 applies a rotational force to the arm 105 via the gears 107a and 107b which act as a speed reducer.

[0070] In addition, in Figure 4 , the arm 105 is in a state of being substantially in contact with the stopper 108b. For the purpose of explaining the actions of each structure, the rotational directions of the gears 107a, 107b, and the arm 105 are shown by arrow marks for convenience, but the arm 105 will not rotate clockwise from the Figure 4 state.

[0071] When the tension rod 103 is functioning, as the arm 105 rotates clockwise, one end of the arm 105 in the approximate +Y direction is lifted upward. Therefore, a medium M (not shown) is pushed in the approximate +Y direction by the tension rod 103 to apply tension.

[0072] The strength of the tension applied to the medium M is adjusted by the elastic coefficient of the power source 106, the reduction ratio of the gears 107a and 107b, the length of the arm 105, the masses of the arm 105 and the tension rod 103, etc.

[0073] Here, with reference to Figure 5 , the tension applied to the medium M will be described. Figure 5 The relationship between the rotation angle of the arm 105 and various torques is shown. In Figure 5 , the horizontal axis is set as the rotation angle of the arm 105, i.e., the action angle [deg (degree)], and the vertical axis is set as the magnitude of the torque [Nmm]. The M on the vertical axis is a positive value and is the same value as that of the Figure 7 described later.

[0074] The torque Wm is the torque formed by the self-weights of the tension rod 103 and the arm 105. The torque Pm is the torque of the force applied by the power source 106. The torque Sm is the combined torque obtained by adding the torque Wm and the torque Pm.

[0075] In addition, the rotation angle of the arm 105 refers to the rotation angle of the arm 105 with the central axis AR as the fulcrum. In the rotation angle of the arm 105, when observing the medium conveying device 100 from the -X direction, the position corresponding to 9 o'clock is set as the reference 0 degree, the clockwise direction is set as the positive rotation angle, and the counterclockwise direction is set as the negative rotation angle.

[0076] When assuming a structure without a power source, in other words, in a structure where tension is applied to the medium only by the self-weight of the tension rod and the arm, the moment of the tension rod varies according to the rotation angle of the arm.

[0077] The tension applied to the medium M is determined by the moment of the tension rod. Therefore, when the moment of the tension rod varies, the tension applied to the medium also varies. The variation of the tension easily reduces the winding accuracy of the medium and causes winding misalignment or the like.

[0078] In contrast, the medium conveying device 100 reduces the variation of the moment of the tension rod 103 by the power source 106. Specifically, in Figure 5 where the moment Wm varies by more than M / 2 in the range where the operating angle of the arm 105 is from -150deg to -20deg. The power source 106 applies a force to rotate the arm 105 in such a way that the change amount is opposite in sign to the change amount of the moment Wm formed by the self-weight of the tension rod 103 and the arm 105. In Figure 5 where the operating angle of the arm 105 is from -150deg to -20deg, the moment Wm has a negative change amount and the moment Pm has a positive change amount. The moment Wm and the moment Pm have change amounts with opposite signs. At least the variation trends of the moment Wm and the moment Pm include line segments with opposite signs of change within the range of the operating angle of the arm 105 when the tension rod 103 swings. In the present embodiment, the moment Wm is negative, and a force is applied by the power source 106 to apply tension to the medium M. However, regardless of whether the moment Wm is positive or negative, the variation of the moment Sm is reduced by adding the moment Pm.

[0079] Specifically, in the medium conveying device 100, the combined moment of the moment Wm and the moment Pm, that is, the moment Sm, becomes the moment of the tension rod 103. The moment Pm is phase-shifted with respect to the moment Wm and has an opposite sign of change. The moment Pm functions to cancel the variation of the moment Wm. Therefore, the variation of the moment Sm becomes smaller than the variation of the moment Wm. Thus, the variation of the moment of the tension rod 103 can be reduced, and the variation of the tension applied to the medium M can be reduced.

[0080] In addition, since the rotating part 107 has gears 107a and 107b that serve as a speed reducer, the adjustment of the moment Pm corresponding to the variation of the moment Wm becomes easy. In addition, if the moment Wm and the moment Pm are adjusted to an anti-phase relationship, the moment Sm does not vary, and a fixed tension can be applied to the medium M. However, even if the moment Wm and the moment Pm cannot be made into a completely anti-phase relationship, by making the signs of change opposite, the variation of the moment Sm can be reduced, and the variation of the tension applied to the medium M can be reduced.

[0081] According to the present embodiment, the following effects can be obtained.

[0082] It is possible to reduce the variation in the tension applied to the medium M. Specifically, in the present embodiment, the tension applied to the medium M depends on the torque Sm synthesized by adding the torque Wm and the torque Pm. Since the torque Wm depends on the rotation angle of the arm portion 105, the torque Wm changes when the rotation angle changes. In contrast, the torque Pm has a sign opposite to the change in the torque Wm, so the change in the torque Wm can be suppressed. Therefore, the torque Sm does not change like the torque Wm, and even when the rotation angle of the arm portion 105 changes, the change in the torque Sm is suppressed. Thereby, even when the rotation angle of the arm portion 105 changes, the change in the tension applied to the medium M is reduced. Therefore, it is possible to provide the medium conveyance device 100 and the printing device 1 in which the change in the tension applied to the medium M is reduced.

[0083] 2. Second Embodiment

[0084] The printing device and the medium conveyance device of the present embodiment are devices in which the structure of the rotating portion 207 is changed with respect to the printing device 1 and the medium conveyance device 100 of the above-described embodiment. The same reference numerals are used for the same structures as those of the printing device 1 and the medium conveyance device 100, and redundant descriptions are omitted.

[0085] As Figure 6 shown, the medium conveyance device of the present embodiment includes a tension bar 103, an arm portion 105, a rotating portion 207, and a power source 106. In addition, although not shown in the drawings, the medium conveyance device of the present embodiment also includes a medium support portion 101 and a winding portion 109. Further, in the Figure 6 description, unless otherwise specified, the state observed from the -X direction is described.

[0086] The difference in the medium conveyance device of the present embodiment is that instead of the pair of rotating portions 107 of the first embodiment, a pair of rotating portions 207 are provided. Each rotating portion 207 has a substantially rod-shaped branch portion 207a and does not have a speed reducer.

[0087] One end portion, which is the root portion of the branch portion 207a, can rotate about the central axis AR and is directly connected to the arm portion 105. The rotating portion 207 supports the arm portion 105 so as to be rotatable. When the branch portion 207a rotates, the arm portion 105 also rotates in conjunction. The angle formed by the branch portion 207a and the arm portion 105 is approximately 100 degrees, and this angle does not change. The power source 106 is mounted on the other end portion, which is the tip portion of the branch portion 207a.

[0088] In the power source 106, one end is mounted on the side wall 101p (not shown), and the other end is mounted on the top end of the branch portion 207a. In the power source 106, a contraction force acts from the other end toward one end, and this contraction force applies a force to the rotating portion 207 to cause it to rotate.

[0089] For the branch portion 207a, an applied force as shown by the blank arrow mark acts through the power source 106. By this force, the branch portion 207a and the arm portion 105 rotate in the clockwise direction. Then, the tension rod 103 is displaced so as to protrude from the medium support portion 101 toward the substantially +Y direction, and applies a tension to the medium M.

[0090] Figure 7 It is a graph showing the relationship between the rotation angle of the arm portion 105 and each torque in the medium conveyance device of the present embodiment. The horizontal axis and the vertical axis of this graph are the same variables as Figure 5 those. However, the numerical values and scales are different.

[0091] As Figure 7 shown, in the present embodiment, the torque of the tension rod 103 also becomes the combined torque of the torque Wm and the torque Pm, that is, the torque Sm. The torque formed by the self-weights of the tension rod 103 and the arm portion 105 is the torque Wm. In Figure 7 it, the torque Wm varies by approximately M / 4 in the range where the action angle of the arm portion 105 is from -70 deg to -30 deg.

[0092] In contrast, in the present embodiment, the torque Pm generated by the power source 106 is added. Since the torque Pm is a change amount with the opposite sign with respect to the change amount of the torque Wm, the variation of the torque Wm can be reduced by the torque Sm. In the present embodiment, the torque Wm is negative, and a force is applied through the power source 106 to apply a tension to the medium M. However, regardless of whether the torque Wm is positive or negative, the variation of the torque Sm is reduced by adding the torque Pm.

[0093] According to the present embodiment, the same effects as those of the above-described embodiment can be obtained. In addition, a simple structure without a speed reducer can be adopted.

[0094] Symbol Explanation

[0095] 1... printing device; 60... printing portion; 100... medium conveyance device; 101... medium support portion; 101p... side wall; 103... tension rod; 105... arm portion; 106... power source; 107... rotating portion; 107a, 107b... gears serving as speed reducers; 109... winding portion; M... medium; Wm... torque formed by self-weight.

Claims

1. A medium conveying device, characterized in that, Comprising: A medium support part for supporting the conveyed medium; A winding part for winding the medium; A tension rod for applying tension to the medium between the medium support part and the winding part; An arm part for supporting the tension rod at one end; A rotating part for rotatably supporting the other end of the arm part; A power source for applying a force to rotate the arm part, The power source applies the force to the arm part in such a way that the change amount has a sign opposite to that of the change amount of the torque formed by the self-weights of the tension rod and the arm part.

2. The medium conveying device according to claim 1, wherein, The power source is a spring.

3. The medium conveying device according to claim 1, wherein, The rotating part has a speed reducer, The power source applies the force to the arm part via the speed reducer.

4. The medium conveying device according to claim 1, wherein, The medium support part has a side wall including a surface intersecting the surface supporting the medium, The rotating part is provided on the side wall.

5. The medium conveying device according to claim 4, wherein, The power source is arranged outside the side wall.

6. A printing device, characterized in that, Comprising: A printing part for printing on a medium; A medium support part for supporting the conveyed medium; A winding part for winding the medium; A tension rod for applying tension to the medium between the medium support part and the winding part; An arm part for supporting the tension rod at one end; A rotating part for rotatably supporting the other end of the arm part; A power source for applying a force to rotate the arm part, The power source applies the force to the arm part in such a way that the change amount has a sign opposite to that of the change amount of the torque formed by the self-weights of the tension rod and the arm part.

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