JP2018115052A - Paper tension control mechanism, and printer - Google Patents

Abstract

[Problem] To control the tension applied to paper between multiple transport rollers. [Solution] An auxiliary transport roller R3 transports paper P1 toward a main transport roller R1. The main transport roller R1 transports paper P1 transported from the auxiliary transport roller R3. A detection roller R5 is provided in a position on the transport path between the main transport roller R1 and the auxiliary transport roller R3. The detection roller R5 is configured to be movable in a direction Dr2 that intersects with the main surface of the paper P1 while in contact with the paper P1 being transported. The auxiliary transport roller R3 controls the transport speed of the paper P1 based on changes in the position of the detection roller R5. [Selected Figure] Figure 7

Description

  The present invention relates to a paper tension control mechanism and a printer having a function of controlling tension applied to paper.

  An ink sheet and roll paper are used in a thermal transfer printer that is a kind of printing apparatus. The roll paper is configured by winding a recording paper (paper) in a roll shape. The ink sheet is a sheet coated with a plurality of types of ink dyes and OP (overcoat) material. The plurality of types of ink dyes are Y (yellow), M (magenta), and C (cyan) dyes. The OP material is a material for protecting the stamp screen.

  The thermal transfer type printer includes a thermal head. The thermal head is provided with a plurality of heating resistors arranged along the main scanning direction orthogonal to the ink sheet and recording paper conveyance direction.

  The thermal transfer type printer selectively heats a plurality of heating resistors in the thermal head to sublimate the dye applied to the ink sheet. Thereby, the dye is transferred to the recording paper having the image receiving layer. The recording paper is, for example, photographic paper or sticker paper. Note that the thermal transfer printer transfers the plurality of types of ink dyes onto the recording paper so that the plurality of types of ink dyes overlap in a predetermined order. Thereby, a desired color is printed on the recording paper.

  The thermal transfer type printer transfers the dye by the thermal head while conveying the ink sheet and the recording paper at a constant speed during printing. Thereby, it is possible to create a printed matter having a desired length.

  Thermal transfer printers include double-sided printers that use roll paper. Patent Document 1 discloses a technique (hereinafter, also referred to as “Related Art A”) for performing double-sided printing by a thermal printer (double-sided printer) having a simple configuration. The thermal printer having the related technology A includes a switching guide. The switching guide is configured so that the recording paper passes through a first path for printing on the main surface of the recording paper or a second path for printing on the back surface of the recording paper. Yes.

  In a thermal transfer printer, a main transport roller called a grip roller for transporting recording paper is used. In order to generate a high conveyance force and to accurately convey the recording paper, for example, a protrusion is provided on the surface of the main conveyance roller.

  Further, the recording paper conveyance path in the double-sided printer is complicated and long. Therefore, in the double-sided printer, in addition to the main transport roller, an auxiliary transport roller for assisting the transport of the recording paper is provided. The auxiliary transport roller assists the transport of the recording paper in, for example, a paper feeding operation, a printing operation, and a recording paper discharging operation. Unlike the main transport roller, the auxiliary transport roller is generally composed of rubber or the like. Therefore, the auxiliary conveyance roller is not used for accurately conveying the recording paper.

  As described above, when the recording paper is conveyed using a plurality of rollers at the same time, the relationship between the rotation speeds of the plurality of rollers is important. In the following, the rotation speed of the main transport roller is also referred to as “Vr1”. In the following, the rotation speed of the auxiliary transport roller is also referred to as “Vr2”.

  For example, when Vr2 is smaller than Vr1, a speed difference is generated between Vr1 and Vr2. In this case, tension (tension) is applied to the recording paper existing between the main conveyance roller and the auxiliary conveyance roller. The conveyance force (crimping force) of the auxiliary conveyance roller is smaller than the conveyance force of the main conveyance roller. Therefore, a situation occurs in which the recording paper slides on the surface of the auxiliary conveyance roller.

  Further, when Vr2 is smaller than Vr1, a large tension is applied to the main transport roller. Therefore, when the tension applied to the main transport roller during printing is larger than the transport force (crimping force) of the main transport roller, for example, the recording paper is displaced. In this case, the recording paper cannot be accurately conveyed. As a result, the area of the recording paper where the dyes of each color are transferred is shifted, and a phenomenon called color misregistration occurs.

  Further, when Vr2 is larger than Vr1, the recording paper is slack based on the difference between Vr2 and Vr1. When the amount of slack in the recording paper increases, the recording paper comes into strong contact with components such as a guide and a thermal head. In this case, scratches are generated on the surface of the recording paper.

  Patent Document 2 discloses a technique for controlling the tension applied to a medium (recording paper) (hereinafter also referred to as “Related Art B”). In Related Art B, the amount of slack in the medium is detected, and the transport amount of the medium is controlled.

  Also, Patent Document 3 discloses a technique for controlling the tension applied to the recording paper (hereinafter also referred to as “Related Technology C”). In Related Art C, a tension lever for controlling the tension applied to the recording paper is used. The tension lever is configured to be movable in an arc shape. In Related Art C, processing for controlling the tension applied to the recording paper is performed based on the amount of fluctuation of the tension lever.

Japanese Patent Laying-Open No. 2015-136696 (FIG. 2) Japanese Patent Laying-Open No. 2012-082024 (FIG. 9) Japanese Patent Laid-Open No. 2015-218033

  In recent years, methods for conveying paper such as recording paper have been diversified. Therefore, there is a printer having a long paper conveyance path. In general, the printer has a configuration in which a plurality of conveyance rollers cooperate to convey paper. In this configuration, the state of the paper existing between the plurality of transport rollers may change, and the tension applied to the paper may change. In this case, it is required to control the tension applied to the paper existing between the plurality of transport rollers.

  In Related Art B, the speed at which each of the two transport rollers transports the paper (medium) is the same. Therefore, the tension applied to the paper existing between the two transport rollers is always constant. That is, the related technology B is not a technology for the purpose of controlling the tension applied to the paper existing between the plurality of transport rollers. In other words, the related technique B cannot satisfy the above-described requirement. Further, the related techniques A and C cannot satisfy the above-described requirements.

  The present invention has been made to solve such a problem, and an object thereof is to provide a paper tension control mechanism or the like that can control the tension applied to the paper existing between a plurality of transport rollers. To do.

  In order to achieve the above object, a paper tension control mechanism according to an aspect of the present invention includes a main transport roller and an auxiliary transport roller provided at positions separated from each other in a transport path through which paper is transported, The auxiliary conveying roller conveys the paper toward the main conveying roller, the main conveying roller conveys the paper conveyed from the auxiliary conveying roller, and the paper tension control mechanism further includes the conveying Among the paths, a detection roller provided at a position between the main conveyance roller and the auxiliary conveyance roller is provided, and the detection roller is in a state where the detection roller is in contact with the paper being conveyed. The auxiliary conveyance roller is configured to be movable in a direction crossing the main surface of the paper, and the auxiliary conveyance roller Based on the change in position of the rollers, to control the transport speed of the paper.

  According to the present invention, the auxiliary transport roller transports the paper toward the main transport roller. The main transport roller transports the paper transported from the auxiliary transport roller. That is, the main transport roller and the auxiliary transport roller cooperate to transport the paper.

  The detection roller is provided at a position between the main conveyance roller and the auxiliary conveyance roller in the conveyance path. The detection roller is configured to be movable in a direction intersecting the main surface of the paper in a state where the detection roller is in contact with the paper being conveyed. The auxiliary transport roller controls the transport speed of the paper based on a change in the position of the detection roller.

  Thereby, the tension applied to the paper existing between the plurality of transport rollers can be controlled.

1 is a diagram simply illustrating a configuration of a printer according to a first embodiment of the present invention. FIG. It is a side view which shows the structure of the paper tension control mechanism which concerns on Embodiment 1 of this invention. FIG. 3 is a cross-sectional view of the paper tension control mechanism taken along line A1-A2 of FIG. It is a figure which shows the structure of the encoder which concerns on Embodiment 1 of this invention. It is a figure which shows a some pulse. It is a block diagram which shows the control structure in the paper tension control mechanism which concerns on Embodiment 1 of this invention. It is a figure which shows the state which the paper pushed down the detection roller. It is a one part enlarged view of an encoder. It is a figure which shows a part of printer in the modification 1 of this invention. It is a figure which shows a part of printer in the modification 2 of this invention. It is a block diagram which shows the characteristic function structure of a paper tension control mechanism.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following drawings, the same components are denoted by the same reference numerals. The names and functions of the components having the same reference numerals are the same. Therefore, a detailed description of some of the components having the same reference numerals may be omitted.

  Note that the dimensions, materials, shapes, and relative arrangements of the components exemplified in the embodiments may be appropriately changed depending on the configuration of the apparatus to which the present invention is applied, various conditions, and the like. Moreover, the dimension of each component in each figure may differ from an actual dimension.

<Embodiment 1>
FIG. 1 is a diagram simply illustrating a configuration of a printer 100 according to Embodiment 1 of the present invention. Note that FIG. 1 does not show a later-described auxiliary conveyance roller R3 and a later-described pressure-bonding roller R4. Also, the position of each component shown in FIG. 1 is not accurate.

  The printer 100 is, for example, a thermal transfer type printer. Referring to FIG. 1, the printer 100 has a function of performing printing using roll paper Pr1. The roll paper Pr1 is configured by winding a long paper P1 in a roll shape. The printer 100 has a function of transporting the paper P1. Hereinafter, the path along which the paper P1 is transported is also referred to as a “transport path”.

  The printer 100 includes a thermal head Sh1, a paper tension control mechanism 50 described later including a main transport roller R1 and a pressure roller R2, and a platen roller R6.

  The thermal head Sh1 generates heat when performing the printing process. The paper tension control mechanism 50 has a function of controlling the tension applied to the paper P1.

  FIG. 2 is a side view showing the configuration of the paper tension control mechanism 50 according to Embodiment 1 of the present invention.

  In FIG. 2, the X direction, the Y direction, and the Z direction are orthogonal to each other. Each of the X direction, the Y direction, and the Z direction shown in the following figures is also orthogonal to each other. Hereinafter, a direction including the X direction and the direction opposite to the X direction (−X direction) is also referred to as “X axis direction”. In the following, the direction including the Y direction and the direction opposite to the Y direction (−Y direction) is also referred to as “Y-axis direction”. Hereinafter, a direction including the Z direction and a direction opposite to the Z direction (−Z direction) is also referred to as a “Z-axis direction”.

  Hereinafter, a plane including the X-axis direction and the Y-axis direction is also referred to as an “XY plane”. Hereinafter, a plane including the X-axis direction and the Z-axis direction is also referred to as an “XZ plane”. Hereinafter, a plane including the Y-axis direction and the Z-axis direction is also referred to as a “YZ plane”.

  FIG. 3 is a cross-sectional view of the paper tension control mechanism 50 taken along line A1-A2 of FIG. 2 and 3, the paper tension control mechanism 50 includes a main transport roller R1, a pressure roller R2, an auxiliary transport roller R3, a pressure roller R4, a detection roller R5, a spring 7, an encoder 8, a photo sensor 9, and paper. A guide 10 and motors 11 and 12 are provided.

  The paper guide 10 is a member for configuring a conveyance path (paper path). The main transport roller R1 and the auxiliary transport roller R3 are provided at positions separated from each other in the transport path.

  The main transport roller R1 is a grip roller. The motor 11 has a function of rotating the main transport roller R1. The motor 11 is, for example, a stepping motor. The main transport roller R <b> 1 rotates according to the driving of the motor 11. The pressure roller R2 is provided so as to transport the paper P1 in cooperation with the main transport roller R1. The pressure roller R2 is a pinch roller.

  The auxiliary transport roller R3 is a rubber roller. The motor 12 has a function of rotating the auxiliary transport roller R3. The motor 12 is, for example, a stepping motor. The auxiliary transport roller R <b> 3 rotates according to the driving of the motor 12. The pressure roller R4 is provided so as to transport the paper P1 in cooperation with the auxiliary transport roller R3. The pressure roller R4 is a pinch roller.

  The main transport roller R1 and the auxiliary transport roller R3 cooperate to transport the paper P1. Specifically, the auxiliary transport roller R3 transports the paper P1 toward the main transport roller R1. The main transport roller R1 transports the paper P1 transported from the auxiliary transport roller R3. In the following, the direction in which the paper P1 is transported is also referred to as “transport direction Dr1”. The transport direction Dr1 in FIG. 2 is the X direction.

  The detection roller R5 is provided at a position between the main transport roller R1 and the auxiliary transport roller R3 in the transport path. When the paper P1 being conveyed is in contact with the detection roller R5, the detection roller R5 rotates according to the conveyance speed of the paper P1. The shape of the detection roller R5 is a cylindrical shape.

  The shaft 6 holds the detection roller R5 so that the detection roller R5 is rotatable. The shaft 6 is a rotation axis of the detection roller R5. Shafts 6 are fixed to both ends in the longitudinal direction of the detection roller R5.

  In the following, the direction intersecting with the main surface P1a of the paper P1 is also referred to as “direction Dr2” or “Dr2”. In FIG. 2, when the main surface P1a is parallel to the XY plane, the direction Dr2 is, for example, the Z-axis direction or the substantially Z-axis direction. The substantially Z-axis direction is, for example, a direction along the Z-axis that is tilted within a range of 1 to 10 degrees.

  The direction Dr2 includes a direction Dr2a and a direction Dr2b. In FIG. 2, the direction Dr2a is the Z direction (upward direction). The direction Dr2b is the opposite direction to the direction Dr2a. In FIG. 2, the direction Dr2b is the −Z direction (downward).

  Moreover, in the following, the state in which the detection roller R5 is in contact with the conveyed paper P1 is also referred to as “contact state StC”. The detection roller 5 is configured to be movable in the direction Dr2 in the contact state StC.

  The spring 7 is provided on the shaft 6 so as to urge the shaft 6 in the direction Dr2a. Since the shaft 6 is fixed to the detection roller R5, the spring 7 biases the detection roller R5 in the direction Dr2a. As an example, the spring 7 is a torsion spring.

  FIG. 4 is a diagram showing the configuration of the encoder 8 according to Embodiment 1 of the present invention. FIG. 4 also shows a photo sensor 9. Hereinafter, the encoder 8 will be described with reference to FIG.

  The encoder 8 has a substantially disk shape. The encoder 8 is provided with a plurality of slits SL1 as shown in FIG. The plurality of slits SL1 are provided in the encoder 8 in a circular shape. Each slit SL1 has a long shape (rectangular shape).

  The encoder 8 is integrated with the detection roller R5. Specifically, the encoder 8 is fixed to a shaft 6 that is a rotation shaft of the detection roller R5. Therefore, the encoder 8 rotates in synchronization with the rotation of the detection roller R5. The method of fixing the encoder 8 to the shaft 6 (detection roller R5) is, for example, screwing, snap fitting, press fitting, or the like.

  The photo sensor 9 has a function of detecting the rotational speed of the encoder 8 as will be described later in detail.

  Referring to FIG. 2 again, the paper guide 10 is provided with a space for providing the detection roller R5. As described above, the detection roller R5 rotates according to the conveyance speed of the paper P1 when the paper P1 being conveyed is in contact with the detection roller R5. In this case, the encoder 8 rotates in synchronization with the rotation of the detection roller R5 according to the conveyance speed of the paper P1.

  In the paper tension control mechanism 50, the main transport roller R 1, the detection roller R 5, and the auxiliary transport roller R 3 are provided in a straight line in the transport path configured by the paper guide 10.

  Next, the photo sensor 9 will be described in detail. The photosensor 9 has a function of detecting the slit SL1. The photosensor 9 detects the slit SL1 using light or the like, for example. With reference to Fig.4 (a), the detection line L1a is a line which shows the position for the photosensor 9 to detect slit SL1. The shape of the detection line L1a is a circle.

  Hereinafter, the rotational speed of the encoder 8 is also referred to as “rotational speed Ve” or “Ve”. In the following, the two adjacent slits SL1 are also referred to as a slit SL1a and a slit SL1b, respectively. In the following, the time from when the photosensor 9 detects the slit SL1a to when the photosensor 9 detects the slit SL1b is also referred to as “time Tv”.

  For example, the photosensor 9 detects (specifies) the rotational speed Ve by dividing the unit distance by the time Tv. The unit distance is 1 cm, for example. That is, the photo sensor 9 is a speed detection unit that detects the rotation speed Ve.

  Further, the photosensor 9 outputs a pulse when detecting the slit SL1. Specifically, the photo sensor 9 outputs a detection signal Sg. The photosensor 9 outputs an H level detection signal Sg in a state in which the slit SL1 is being detected. Further, the photo sensor 9 outputs an L level detection signal Sg in a state where the slit SL1 is not detected.

  Therefore, when the encoder 8 is rotating, the photosensor 9 sequentially outputs a plurality of pulses expressed by the detection signal Sg, for example, as shown in FIG. The pulse output from the photosensor 9 is a pulse having a width corresponding to the magnitude of the rotation speed Ve. Note that the pulse width output from the photosensor 9 is smaller as the rotational speed Ve is higher. Hereinafter, the width of the pulse is also referred to as “width Wp” or “Wp”.

  Next, description will be given for controlling the tension applied to the paper P1. FIG. 6 is a block diagram showing a control configuration in the paper tension control mechanism 50 according to Embodiment 1 of the present invention. The paper tension control mechanism 50 further includes a pulse counter 14, a pulse width detection unit 15, and a rotation control unit 13.

  The pulse counter 14 detects the pulses output from the photosensor 9 and counts the number of the pulses. Hereinafter, the number of pulses counted by the pulse counter 14 is also referred to as “pulse number Pn” or “Pn”.

  Each time the pulse width detector 15 detects a pulse, the pulse width detector 15 detects the width Wp of the pulse. Each time the pulse width detector 15 detects the pulse width Wp, the pulse width detector 15 notifies the pulse counter 14 of the pulse width Wp. Therefore, the pulse counter 14 always knows the width Wp (pulse width).

  Hereinafter, the rotation speed of the main transport roller R1 is also expressed as “rotation speed Vr1” or “Vr1”. In the following, the rotation speed of the auxiliary transport roller R3 is also expressed as “rotation speed Vr2” or “Vr2”.

  The rotation control unit 13 controls the motor 12 so that the rotation speed Vr2 of the auxiliary transport roller R3 changes. Further, the rotation control unit 13 controls the motor 11 so that the rotation speed Vr1 of the main transport roller R1 changes. Therefore, the rotation control unit 13 always knows the rotation speeds Vr1 and Vr2.

  The rotation control unit 13 may be configured not to control the motor 11. In this configuration, the rotation control unit 13 always receives the rotation speed Vr1 from another rotation control unit that controls the motor 11. Thereby, the rotation control unit 13 always knows the rotation speeds Vr1 and Vr2.

  Here, the following premise Pr1 is considered. In the premise Pr1, as an example, Vr1 <Vr2. Under the assumption Pr1, the paper P1 is slack so that the paper P1 does not come into contact with the detection roller R5, for example, as shown in FIG. Therefore, in the premise Pr1, even when the paper P1 is being conveyed in the direction Dr1, the detection roller R5 does not rotate. In this case, the number of pulses Pn obtained by the pulse counter 14 is zero.

  When the amount of slack in the paper P1 increases, the paper P1 may hit the paper guide 10 and the like, and the paper P1 may be scratched. Therefore, it is necessary to give a certain tension to the paper P1.

  Therefore, when the pulse number Pn is 0, the pulse counter 14 transmits (feeds back) non-rotation information to the rotation control unit 13. The non-rotation information is information indicating that the detection roller R5 is not rotating.

  In response to receiving the non-rotation information, the rotation control unit 13 controls the motor 12 so that the rotation speed Vr2 gradually decreases until Vr1> Vr2. That is, the rotation control unit 13 shifts the state of the paper P1 to a state in which the paper P1 is tensioned.

  When tension is applied to the paper P1, the paper P1 comes into contact with the detection roller R5. Thereby, the detection roller R5 and the encoder 8 start to rotate. As a result, pulses are generated, and the pulse counter 14 counts the pulses. That is, the pulse number Pn becomes 1 or more.

  When the pulse starts to be generated, the pulse counter 14 transmits (feeds back) the rotation information to the rotation control unit 13. The rotation information is information indicating that the detection roller R5 is rotating.

  The rotation control unit 13 controls the motor 12 so that a certain amount of tension is applied to the paper P1 in response to the reception of the rotation information. Specifically, the rotation control unit 13 repeatedly performs control such as control for maintaining the rotation speed Vr2 and control for increasing the rotation speed Vr2 on the motor 12, for example.

  As described above, the configuration in which the encoder 8 is fixed to the detection roller R5 makes it possible to quickly detect whether or not a tension is applied to the paper P1.

  As described above, the spring 7 biases the detection roller R5 (shaft 6) in the direction Dr2a. Hereinafter, the force that the spring 7 biases the detection roller R5 (shaft 6) in the direction Dr2a is also referred to as “force Pws”. The direction opposite to the direction in which the force Pws is applied is the direction Dr2b. In the following, the force applied by the paper P1 to the detection roller R5 in the direction Dr2b by the tension applied to the paper P1 is also referred to as “force Pwp”.

  Even when the feedback control as described above is performed, the tension control may not be in time, and the force Pwp may be larger than the force Pws. This state is a state as shown in FIG.

  FIG. 7 shows a state where the paper P1 pushes down the detection roller R5 (encoder 8) in the direction Dr2b. Hereinafter, the state where the detection roller R5 (encoder 8) is pushed down in the direction Dr2b by the paper P1 is also referred to as a “push-down state”. Hereinafter, the state in which the detection roller R5 (encoder 8) is not pushed down in the direction Dr2b by the paper P1 is also referred to as a “non-pressed state”.

  Even in the depressed state, the pulse number Pn depends on the rotation speed Vr1 of the main transport roller R1, and therefore the pulse number Pn is constant. The rotation speed Vr1 corresponds to the transport speed of the paper P1.

  However, when shifting from the non-pressed state to the pressed state, the position of the encoder 8 with respect to the photosensor 9 moves from the position shown in FIG. 4A to the position shown in FIG. Therefore, the detection line L1a changes to the detection line L1b. The detection line L1b is a line indicating the position for the photosensor 9 to detect the slit SL1.

  Hereinafter, the rotational speed Ve of the outer peripheral portion of the encoder 8 is also referred to as “rotational speed Ve1” or “Ve1”. The rotational speed Ve1 is the rotational speed Ve in a non-pressed state. In the following, the rotational speed Ve of the inner periphery of the encoder 8 is also referred to as “rotational speed Ve2” or “Ve2”. The rotational speed Ve2 is the rotational speed Ve in the pushed down state.

  FIG. 5A shows a plurality of pulses in a non-pressed state. FIG. 5B shows a plurality of pulses in the depressed state. In the depressed state, the pulse number Pn is the same as in the non-depressed state. However, the closer the photosensor 9 is to the outer periphery of the encoder 8, the greater the rotational speed Ve. Therefore, Ve1 in the non-pressed state is larger than Ve2 in the pressed state. That is, the relational expression Ve1> Ve2 is established.

  When the position of the detection roller R5 (encoder 8) is changed by shifting from the non-pressed state to the pressed state, the rotational speed Ve of the encoder 8 changes from Ve1 to Ve2. That is, the encoder 8 is configured such that the rotational speed Ve of the encoder 8 changes according to the change in the position of the detection roller R5.

  Here, description will be made using the adjacent slit SL1a and slit SL1b shown in FIG. FIG. 8 is an enlarged view of a part of the encoder 8. The center line Lca is a line along the extending direction of the slit SL1a. The center line Lcb is a line along the extending direction of the slit SL1b. As an example, it is assumed that the angle formed by the center line Lca and the center line Lcb is 45 degrees.

  Hereinafter, the length of the detection line L1a between the center line Lca and the center line Lcb is also referred to as “length L1ax”. In the following description, the length of the detection line L1b between the center line Lca and the center line Lcb is also referred to as “length L1bx”. In the following, the half length of the width of the slit SL1 is expressed as “length t” or “t”. In the following, “2 × t” is also expressed as “length 2t” or “2t”. The length 2t is the width of the slit SL1.

  In the following, the time required for the outer peripheral portion of the encoder 8 to rotate by the length L1ax in the non-pressed state is also expressed as “time Txa” or “Txa”. In the following, the time required for the inner circumferential portion of the encoder 8 to rotate by the length L1bx in the depressed state is also expressed as “time Txb” or “Txb”.

  The width of the slit SL1 at the outer peripheral portion of the encoder 8 and the width of the slit SL1 at the inner peripheral portion of the encoder 8 are 2t. The time Txa is the same as the time Txb. Therefore, as described above, the rotational speed Ve1 of the outer peripheral portion of the encoder 8 is higher than the rotational speed Ve2 of the inner peripheral portion of the encoder 8.

  Hereinafter, the time required for the outer peripheral portion of the encoder 8 to rotate by a length of 2t in the non-pressed state is also expressed as “time Ta” or “Ta”. In the following, the time required for the inner peripheral portion of the encoder 8 to rotate by a length of 2t in the depressed state is also expressed as “time Tb” or “Tb”.

  The time Ta and the time Tb are expressed by the following equations 1 and 2, respectively.

  Note that a relationship of (2t / Ve1) <(2t / Ve2) is obtained from Ve1> Ve2. Therefore, the relational expression of Ta <Tb is established. The time Ta corresponds to the pulse width Wp shown in FIG. The time Tb corresponds to the pulse width Wp shown in FIG.

  Therefore, when the non-depressed state shifts to the depressed state, the state of the plurality of pulses changes from the state of FIG. 5A to the state of FIG. That is, when the position of the detection roller R5 (encoder 8) is changed by shifting from the non-pressed state to the pressed state, the pulse width Wp changes from Ta to Tb.

  As described above, the pulse counter 14 always knows the width Wp (pulse width). Therefore, the pulse counter 14 detects that the position of the detection roller R5 has changed based on the change in the pulse width Wp. That is, the pulse counter 14 is a detection unit that detects that the position of the detection roller R5 has changed.

  The process for detecting that the position of the detection roller R5 has changed may be configured by the pulse width detection unit 15 (hereinafter also referred to as “configuration Cta”). In the configuration Cta, the pulse width detection unit 15 detects that the position of the detection roller R5 has changed based on the change in the pulse width Wp. In the configuration Cta, the pulse width detection unit 15 is a detection unit that detects that the position of the detection roller R5 has changed.

  As described above, when the pulse width Wp changes from Ta to Tb due to a change in the position of the detection roller R5 (encoder 8), an extra tension greater than the force Pws is applied to the paper P1. Hereinafter, the tension applied to the paper P1 is also referred to as “paper tension”.

  Therefore, when the pulse width Wp changes from Ta to Tb, tension control processing is performed. That is, a tension control process is performed based on a change in the position of the detection roller R5 (encoder 8).

  In the tension control process performed based on the change in the position of the detection roller R5, the auxiliary transport roller R3 controls the transport speed of the paper P1 so that the paper tension becomes small. That is, the auxiliary transport roller R3 controls the transport speed of the paper P1 so that the paper tension becomes small based on the change in the position of the detection roller 5. In other words, when the position of the detection roller 5 changes, the auxiliary transport roller R3 transports the paper P1 so that the position after the change of the detection roller 5 becomes the position before the change of the detection roller 5. To control.

  Specifically, in the tension control process, the pulse counter 14 as a detection unit transmits a speed improvement instruction to the rotation control unit 13. The speed improvement instruction is an instruction for increasing the rotational speed Vr2 of the auxiliary transport roller R3 until Vr2> Vr1 is satisfied. In the configuration Cta described above, the pulse width detection unit 15 serving as a detection unit transmits a speed improvement instruction to the rotation control unit 13.

  The rotation control unit 13 controls the rotation speed Vr2 of the auxiliary transport roller R3 in response to receiving the speed improvement instruction. Specifically, the rotation control unit 13 controls the motor 12 in response to the reception of the speed improvement instruction so that the rotational speed Vr2 of the auxiliary transport roller R3 increases until Vr2> Vr1 is satisfied.

  The auxiliary conveyance roller R3 conveys the paper P1 by rotating the auxiliary conveyance roller R3. Therefore, the auxiliary conveyance roller R3 controls the conveyance speed of the paper P1 so that Vr2> Vr1 is established according to the rotation control unit 13 controlling the rotation speed Vr2 of the auxiliary conveyance roller R3. Thereby, the tension control process ends.

  As described above, when the position of the detection roller R5 (encoder 8) is changed by shifting from the non-pressed state to the pressed state, the rotational speed Ve of the encoder 8 changes from Ve1 to Ve2. That is, the rotation speed Ve changes according to the change in the position of the detection roller R5.

  When the rotation speed Ve changes from Ve1 to Ve2, the pulse width Wp changes from Ta to Tb, and the rotation control unit 13 controls the rotation speed Vr2 of the auxiliary transport roller R3 in response to receiving the speed improvement instruction. The auxiliary conveyance roller R3 conveys the paper P1 by rotating the auxiliary conveyance roller R3.

  Therefore, the auxiliary conveyance roller R3 controls the conveyance speed of the paper P1 according to the control of the rotation speed Vr2 of the auxiliary conveyance roller R3 by the rotation control unit 13. That is, the auxiliary transport roller R3 controls the transport speed of the paper P1 based on the rotation speed Ve of the encoder 8 that changes according to the change in the position of the detection roller R5.

  Note that the paper tension is reduced by performing the tension control process. Therefore, it is possible to prevent the main transport roller R1 from being loaded more than necessary. As a result, occurrence of color misregistration or the like can be prevented.

  As described above, according to the present embodiment, the auxiliary transport roller R3 transports the paper P1 toward the main transport roller R1. The main transport roller R1 transports the paper P1 transported from the auxiliary transport roller R3. That is, the main transport roller R1 and the auxiliary transport roller R3 cooperate to transport the paper P1.

  The detection roller R5 is provided at a position between the main transport roller R1 and the auxiliary transport roller R3 in the transport path. The detection roller R5 is configured to be movable in a direction Dr2 intersecting the main surface of the paper P1 in a state where the detection roller R5 is in contact with the paper P1 being conveyed. The auxiliary transport roller R3 controls the transport speed of the paper P1 based on the change in the position of the detection roller R5.

  Thereby, the tension applied to the paper existing between the plurality of transport rollers can be controlled.

  Further, in the present embodiment, the detection roller R5 that is movable in the direction intersecting the main surface of the paper P1 and the encoder 8 that rotates in synchronization with the rotation of the detection roller R5 are used. Such a change in tension can be quickly detected.

  Further, the paper tension control mechanism 50 according to the present embodiment has a function of detecting the width of a pulse obtained by the rotation of the encoder 8. As a result, even when a necessary tension is applied to the paper P1, the tension applied to the paper P1 can be detected within the range of the force Pws of the spring 7. Therefore, it is possible to accurately detect a change in tension applied to the conveyed paper P1.

  Further, the amount of movement of the detection roller R5 can also be known based on the amount of change in the pulse width Wp. Therefore, the magnitude of the tension applied to the paper can be grasped. Even when a sudden change in tension occurs, it is possible to prevent an excessive load from being applied to the main transport roller R1 within the range of the force Pws of the spring 7. As a result, occurrence of color misregistration or the like can be prevented.

  Moreover, in this Embodiment, even if the several roller which conveys paper P1 is arrange | positioned linearly or non-linearly, the paper tension control mechanism 50 can be comprised. Therefore, the freedom degree of arrangement | positioning of components, such as a some conveyance roller, in the paper tension control mechanism 50 can be improved. Further, it is possible to accurately detect a change in tension applied to the conveyed paper. Therefore, the tension control of the paper can be precisely performed at low cost and space saving. As a result, a print with high print quality can be obtained.

  In Related Art B, the plurality of rollers are arranged linearly. Therefore, when performing tension control based on the detection of slack, it is possible to know the state of the paper while the paper is slack. However, there is a problem in that the tension applied to the paper cannot be detected in a state where the tension applied to the paper is more than necessary.

  In addition, when the plurality of rollers are non-linearly arranged, the slack shape of the paper is not uniform. In this case, in Related Technology B, the accuracy of looseness detection by the sensor tends to vary. Further, in the related art B, since the slack is used, the position for arranging the parts is limited to the lower side of the paper. Therefore, there is a problem that the degree of freedom of component placement is limited.

  In Related Art C, parts arranged at both ends of the paper need to be arranged in a non-linear manner. Even in this case, there is a problem that the degree of freedom of component placement is limited.

  In Related Art C, it is impossible to detect a change in tension until the tension lever starts to move. Therefore, there is a problem that a certain tension is applied to the paper during the period until the tension lever starts to move. In Related Technology C, the cost of parts for installing the tension lever, installation space, and the like are required.

  Therefore, the paper tension control mechanism 50 (printer 100) of the present embodiment is configured as described above. Therefore, the paper tension control mechanism 50 (printer 100) can solve the above problem.

<Modification 1>
The configuration of this modification is a configuration in which a plurality of rollers are provided in a non-linear manner (hereinafter also referred to as “configuration Ct1”).

  FIG. 9 is a diagram illustrating a part of the printer 100 to which the configuration Ct1 is applied according to the first modification of the present invention. The printer 100 to which the configuration Ct1 is applied is a double-sided printer. The printer 100 to which the configuration Ct1 is applied includes a paper tension control mechanism 50.

  In the configuration Ct1, the paper guide 10 is curved. Therefore, the conveyance path formed by the paper guide 10 is also curved. In the paper tension control mechanism 50 to which the configuration Ct1 is applied, the main transport roller R1 and the auxiliary transport roller R3 are provided at positions separated from each other in the transport path.

  In the paper tension control mechanism 50 to which the configuration Ct1 is applied, the detection roller R5 is provided at a position between the main conveyance roller R1 and the auxiliary conveyance roller R3 in the conveyance path. The encoder 8 is integrated with the detection roller R5.

  In the paper tension control mechanism 50 to which the configuration Ct1 is applied, the main transport roller R1, the detection roller R5, and the auxiliary transport roller R3 are provided in a non-linear manner in the transport path configured by the paper guide 10.

  Note that the paper tension control mechanism 50 to which the configuration Ct1 is applied performs the same processing as in the first embodiment.

  As described above, according to this modification, the same effects as those of the first embodiment can be obtained even in the configuration in which the main transport roller R1, the detection roller R5, and the auxiliary transport roller R3 are provided in a non-linear manner. It is done.

<Modification 2>
The configuration of this modification is a configuration using a spring of a different type from the spring 7 that is a torsion spring (hereinafter also referred to as “configuration Ct2”).

  FIG. 10 is a diagram illustrating a part of the printer 100 to which the configuration Ct2 is applied according to the second modification of the present invention. The printer 100 to which the configuration Ct2 is applied differs from the printer 100 to which the configuration Ct1 is applied only in that a spring 7A is provided instead of the spring 7.

  The spring 7A is a tension coil spring. That is, the spring 7A is an extended spring. In the configuration Ct2, the spring 7A biases the shaft 6 in the direction Dr2a. Therefore, in the configuration Ct2, the detection roller R5 is urged in the direction Dr2a by the spring 7A.

  As described above, according to this modification, the detection roller R5 is biased in the direction Dr2a by the spring 7A by the spring 7A that is a tension coil spring.

  The tension coil spring can obtain a higher initial tension than the torsion spring. Therefore, it is possible to take a wide tension range until the detection roller R5 and the encoder 8 move in the direction Dr2a.

  Thereby, even if it is a structure with bad responsiveness of the speed control from a motor to a roller, use of the paper tension control mechanism 50 becomes easy in the range which does not move detection roller R5. A configuration with poor responsiveness is a configuration in which, for example, parts such as a torque limiter and a gear train are sandwiched between a roller and a stepping motor, and play is large. The play is a range in which the driving of the stepping motor is not reflected in the operation of the roller.

  The configuration Ct2 may be applied to the paper tension control mechanism 50 according to the first embodiment. That is, in the paper tension control mechanism 50 shown in FIGS. 2 and 3, the spring 7 </ b> A may be used instead of the spring 7.

<Modification 3>
The configuration of this modification is a configuration in which the configuration for detecting the movement of the detection roller R5 is smaller than the configuration of the first embodiment (hereinafter also referred to as “configuration Ct3”).

  Hereinafter, the configuration used to detect the movement of the detection roller R5 is also referred to as a “movement detection configuration”. The movement detection configuration includes an encoder 8 and a photo sensor 9.

  The paper tension control mechanism 50 included in the printer 100 to which the configuration Ct3 is applied includes a detection component instead of the encoder 8 and the photosensor 9. The detection component is smaller in size than the encoder 8. The detection component has a function of detecting that the position of the detection roller R5 has changed. The detection component is, for example, a switch such as a micro switch or a push switch. The detection component may be a pressure sensor, for example. In the configuration Ct3, instead of the pulse counter 14 or the pulse width detection unit 15, the detection component detects that the position of the detection roller R5 has changed.

  As described above, according to this modification, it is possible to configure the paper tension control mechanism 50 with a smaller space than in the first embodiment. That is, the paper tension control mechanism 50 can be reduced in size.

  Note that the configuration Ct3 may be applied to the configuration Ct1 or the configuration Ct2.

  At present, thermal transfer printers that have been developed in the past and print on one side of paper are already widely used. For this reason, the development of thermal transfer type double-sided printers capable of double-sided printing that can easily generate high added value is increasing.

  In double-sided printers, the state of the back side of paper, which was not a concern with single-sided printers, is also regarded as important. Therefore, when printing with a double-sided printer, it is necessary to be more careful about the state of paper transport.

  Further, in a printer using a roll paper and having a paper reversing mechanism, there is a problem that the paper tends to strongly hit a guide or the like because the paper is reversely warped. Therefore, it is required to appropriately control the state of the paper and appropriately transport the paper.

  Therefore, the paper tension control mechanism 50 (printer 100) of the present embodiment is configured as described above. Therefore, the paper tension control mechanism 50 (printer 100) can satisfy the above requirements.

(Function block diagram)
FIG. 11 is a block diagram showing a characteristic functional configuration of the paper tension control mechanism BL10. The paper tension control mechanism BL10 corresponds to the paper tension control mechanism 50 according to any one of the first embodiment, the first modification, the second modification, and the third modification. That is, FIG. 11 is a block diagram showing the main functions related to the present invention among the functions of the paper tension control mechanism BL10.

  The paper tension control mechanism BL10 includes a main transport roller BL1, an auxiliary transport roller BL3, and a detection roller BL5.

  The main transport roller BL1 and the auxiliary transport roller BL3 are provided at positions separated from each other in the transport path through which the paper is transported. The auxiliary transport roller BL3 transports the paper toward the main transport roller BL1. The main transport roller BL1 transports the paper transported from the auxiliary transport roller BL3. The detection roller BL5 is provided in a position between the main transport roller BL1 and the auxiliary transport roller BL3 in the transport path.

  The main transport roller BL1 corresponds to the main transport roller R1. The auxiliary transport roller BL3 corresponds to the auxiliary transport roller R3. The detection roller BL5 corresponds to the detection roller R5.

  The detection roller BL5 is configured to be movable in a direction intersecting with the main surface of the paper in a state where the detection roller is in contact with the paper being conveyed. The auxiliary transport roller BL3 controls the transport speed of the paper based on a change in the position of the detection roller BL5.

(Other variations)
The paper tension control mechanism and the printer according to the present invention have been described above based on the embodiment and each modification. However, the present invention is not limited to the embodiment and each modification. Within the scope of the present invention, modifications that are conceivable by those skilled in the art are applied to the embodiments and the respective modifications, and are also included in the present invention. That is, within the scope of the invention, the present invention can be freely combined with the embodiment and each modification, or can be appropriately modified and omitted with the embodiment and each modification.

  Further, the paper tension control mechanism 50 may not include all the components shown in the drawing. That is, the paper tension control mechanism 50 needs to include only the minimum components that can realize the effects of the present invention.

  In addition, the present invention may be realized as a paper tension control method in which the operation of the characteristic components included in the paper tension control mechanism 50 is a step.

  7, 7A Spring, 8 Encoder, 9 Photo sensor, 50, BL10 Paper tension control mechanism, 100 Printer, R1, BL1 main transport roller, R3, BL3 Auxiliary transport roller, R5, BL5 detection roller.

Claims (8)

A paper tension control mechanism,
Of the transport path through which the paper is transported, the main transport roller and the auxiliary transport roller provided at positions separated from each other,
The auxiliary conveyance roller conveys the paper toward the main conveyance roller,
The main transport roller transports the paper transported from the auxiliary transport roller,
The paper tension control mechanism further includes:
Of the transport path, provided with a detection roller provided at a position between the main transport roller and the auxiliary transport roller,
The detection roller is configured to be movable in a direction intersecting with the main surface of the paper in a state where the detection roller is in contact with the paper being conveyed.
The auxiliary transport roller controls the paper transport speed based on a change in the position of the detection roller. The paper tension control mechanism further includes:
An encoder that is fixed to the rotation shaft of the detection roller, has an encoder that rotates in synchronization with the rotation of the detection roller, and a function that detects the rotation speed of the encoder, and has a width corresponding to the magnitude of the rotation speed. A speed detector that outputs pulses;
The paper tension control mechanism according to claim 1, further comprising: a detection unit that detects that the position of the detection roller has changed based on the change in the width of the pulse. The encoder is configured such that the rotational speed of the encoder changes according to a change in the position of the detection roller,
The paper tension control mechanism according to claim 2, wherein the auxiliary transport roller controls the transport speed of the paper based on a rotation speed of the encoder that changes according to a change in a position of the detection roller. The paper tension control mechanism according to any one of claims 1 to 3, wherein the main conveyance roller, the detection roller, and the auxiliary conveyance roller are provided in a straight line in the conveyance path. The paper tension control mechanism according to any one of claims 1 to 3, wherein the main conveyance roller, the detection roller, and the auxiliary conveyance roller are provided in a non-linear manner in the conveyance path. The paper tension control mechanism according to any one of claims 1 to 5, wherein the detection roller is biased by an extended spring. The paper tension control mechanism further includes:
The paper tension control mechanism according to claim 1, further comprising a switch having a function of detecting that the position of the detection roller has changed. A printer comprising the paper tension control mechanism according to claim 1.

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