JP4661537B2 - Sheet conveying apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to control when conveying so-called roll paper.

  There is an image forming apparatus that forms an image by using a wound long sheet as a recording material. This type of recording material is generally called roll paper (or web). Roll paper has an advantage that it can cope with an arbitrary image size by cutting at a position corresponding to the image size, in addition to lower cost than a regular cut paper.

  Here, FIG. 7 is a diagram illustrating a part of a conventional image forming apparatus using roll paper. The image forming apparatus 900 is a so-called sublimation color printer, and includes a supply shaft 11, a feed roller 21, a pinch roller 22, a thermal head 31, and a platen roller 32. The roll paper R is accommodated while being wound around the supply shaft 11, and is sent out in the direction of the thermal head 31 by the feed roller 21 and the pinch roller 22 facing each other. The thermal head 31 has a plurality of heating elements, and heats an ink ribbon film interposed between the thermal head 31 and the roll paper R to sublimate the dye or the like, and transfers it to the surface of the roll paper. The image forming apparatus 900 forms an image using four types of ink ribbon films of Y (yellow), M (magenta), C (cyan), and overcoat.

  In order to form a color image in the image forming apparatus 900, it is necessary to transfer a plurality of color dyes in the thermal head 31. Therefore, the image forming apparatus 900 transfers the dye while reciprocating the roll paper R by the same number as the number of colors according to the size of the image. That is, the image forming apparatus 900 performs the fixing process by reciprocating the roll paper R four times to form one color image. At this time, the roll paper R sent out by the feed roller 21 is taken up by the feed roller 21 and the supply shaft 11. However, the roll paper R is not fed between the feed roller 21 and the supply shaft 11, so that the roll paper R is not bent. The speed at which the shaft 11 winds the roll paper R is set to be faster than the speed at which the feed roller 21 transports the roll paper R.

  The thermal head 31 performs a transfer process when the roll paper R is wound up by the feed roller 21 and the supply shaft 11. After that, the image forming apparatus 900 sends the roll paper R that has been wound up again to the feed roller 21 to prepare for the next fixing process. When the roll paper R is fed by the feed roller 21 and stops, the supply shaft 11 rotates slightly due to inertia. For this reason, the roll paper R is bent (or loosened) between the feed roller 21 and the supply shaft 11, but in the next transfer process, the supply shaft 11 is faster than the speed at which the feed roller 21 transports the roll paper R. Since the roll paper R is taken up at a higher speed, the bending that has occurred in the roll paper R will eventually be eliminated.

At the moment when this bending is eliminated, a strong tension is applied to the roll paper R being conveyed. When the impact due to this tension is transmitted to the thermal head 31, unnecessary dye may be transferred in a streak pattern on the surface of the roll paper R, which may deteriorate the image quality. In order to prevent such deterioration in image quality, the roll paper R is appropriately bent between the feed roller 21 and the supply shaft 11 so that the tension applied to the roll paper R is maintained in an appropriate state. It is necessary to suppress the impact. For this purpose, it is necessary to appropriately adjust the speed ratio between the feed roller 21 and the supply shaft 11 and the torque when the supply shaft 11 is wound.
JP-A-2005-60017 JP 2005-88266 A

  However, since the roll paper R is wound around the supply shaft 11, its outer diameter changes according to the amount of use. The roll paper R in a state of being wound around the supply shaft 11 has a large outer diameter in a new state, that is, a state where the amount of use is small (for example, the state of FIG. 7), and the outer diameter becomes smaller as it is consumed. (For example, the state of FIG. 8). Therefore, even if the supply shaft 11 rotates at the same angular velocity, the amount of roll paper R to be wound is not always constant, and changes according to the outer diameter. That is, in the conventional image forming apparatus 900, even if the reduction ratio and the torque are adjusted so that the tension applied to the roll paper R is appropriate, the appropriate tension cannot be maintained when the amount of the roll paper R changes. There is a problem.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a technique that makes it possible to appropriately maintain a bending amount when winding a roll paper.

In order to achieve the above-mentioned object, the present invention provides a storage means for storing a long sheet wound around a shaft, and the shaft of the storage means in a direction of feeding the sheet from the storage means. A driving unit that rotates in a first direction or a second direction that is a winding direction of the sheet; and a conveying unit that is driven by the driving unit, and the shaft is driven by a speed at which the sheet is fed out. A conveying means for conveying the sheet at a slower speed and conveying the sheet at a speed slower than a speed at which the shaft winds the sheet; and an amount of the sheet wound around the shaft of the accommodating means. When the calculating unit and the driving unit wind the sheet around the shaft, and the amount of the sheet calculated by the calculating unit is large, the amount of the sheet calculated by the calculating unit is And a limiting means for reducing the amount of rotation of the shaft than when not, the limiting means comprises a clutch for transmitting or interrupting a driving force applied to said shaft by said driving means, calculated by the calculating means Provided is a sheet conveying device that, when the amount of sheets is large, makes the time for blocking the driving force applied to the shaft longer than when the amount of sheets calculated by the calculating means is small .
Further, when the driving unit causes the sheet to be fed to the shaft, the limiting unit has a larger amount of the sheet calculated by the calculating unit than a smaller amount of the sheet calculated by the calculating unit. The structure which reduces the rotation amount of the said axis | shaft may be sufficient .
According to this sheet conveying apparatus, for example, the amount of the sheet wound around the shaft is calculated from the outer diameter of the wound sheet, and the rotation amount of the shaft, that is, the sheet rotation is calculated from the calculated sheet amount. The winding amount and the feeding amount are determined. That is, according to this sheet conveying apparatus, the amount of sheet winding and the amount of feeding can be varied according to the outer diameter of the sheet.

Further, in the sheet conveying apparatus according to the present invention, the calculating means includes a sensor that detects a rotation angle of the shaft of the accommodating means, and the first distance of the sheet is determined by using the conveying means by a predetermined distance. The amount of the sheet wound around the shaft may be calculated based on the rotation angle detected by the sensor when the sheet is conveyed in the direction and the sheet is conveyed by the distance .

  The present invention can be specified not only as the above-described sheet conveying apparatus but also as an image forming apparatus in which a transfer unit and a cutting unit are further provided in the sheet conveying apparatus.

  As described above, according to the present invention, it is possible to appropriately maintain the amount of bending when the roll paper is wound.

  Hereinafter, preferred embodiments according to the present invention will be given and described with reference to the drawings. In this embodiment, an image forming apparatus which is a sublimation type color printer will be described as an example. For convenience of explanation, in the image forming apparatus shown below, the same components as those in the image forming apparatus 900 in FIG.

[1. Constitution]
FIG. 1 is a diagram showing an overall configuration of an image forming apparatus 100 according to an embodiment of the present invention. 2 and 3 are diagrams showing the drive unit 5 and the measurement unit 6 of the image forming apparatus 100, respectively. As shown in these drawings, the configuration of the image forming apparatus 100 includes a roll paper storage unit 1, a sheet conveyance unit 2, a transfer unit 3, a cutting unit 4, a drive unit 5, and a measurement unit 6. Broadly divided.

  The roll paper storage unit 1 includes a supply shaft 11 and a drive unit 5, and roll paper is stored on the supply shaft 11 in a wound state. The supply shaft 11 is rotatably supported by supporting both ends thereof. In addition, the supply shaft 11 is configured to be rotated in the direction of an arrow A or B in the drawing by the driving unit 5 so that the roll paper can be taken up.

  Here, the drive unit 5 that transmits the drive force to the supply shaft 11 will be described. As shown in FIG. 2, the drive unit 5 includes gears 51, 53, 54 and an electromagnetic clutch 52. The gear 51 is connected to a feed roller 21 described later, and transmits the rotational force of the feed roller 21. The electromagnetic clutch 52 transmits or blocks the rotational force from the gear 51. When the electromagnetic clutch 52 is in the on state, the rotational force from the gear 51 is transmitted to the gear 53, and when the electromagnetic clutch 52 is in the off state, the rotational force from the gear 51 is interrupted. The gear 53 transmits the rotational force from the electromagnetic clutch 52 to a gear 54 that is fixed to the supply shaft 11.

  Note that when the roll paper is wound around the supply shaft 11, the driving unit 5 rolls the supply shaft 11 around the unit time rather than the amount of roll paper conveyed by the feed roller 21 per unit time. The gear ratio is adjusted so that the amount of is larger. With such a configuration, it is possible to prevent the roll paper from being bent more than necessary between the supply shaft 11 and the feed roller 21 when the supply shaft 11 winds the roll paper. Similarly, when the roll paper is sent out from the supply shaft 11, the amount of roll paper that the supply shaft 11 sends out per unit time is larger than the amount of roll paper that the feed roller 21 carries per unit time. .

  The sheet conveying unit 2 includes a feed roller 21 and a pinch roller 22. The feed roller 21 is a roller that is rotated in the direction of an arrow C or D in the drawing by a driving device (not shown). The pinch roller 22 is a rotatable roller that faces the feed roller 21 via the roll paper, and is driven by the rotation of the feed roller 21. The feed roller 21 and the pinch roller 22 are pressed against each other with an appropriate nip pressure, and the roll paper is conveyed by the frictional force of the roller surface.

  The transfer unit 3 includes a thermal head 31 and a platen roller 32. The thermal head 31 includes a plurality of heating elements and heats an ink ribbon film (not shown) interposed between the thermal paper 31 and the roll paper. There are four types of ink ribbon films, each of which is coated with Y, M, C dyes or overcoats (hereinafter collectively referred to as “dyes etc.”). Here, the overcoat is for forming a protective layer on the surface of the roll paper. The dye is sublimated by heating and transferred to the surface of the roll paper. The platen roller 32 is a roller that is arranged with an appropriate distance from the thermal head 31 and improves the adhesion between the thermal head 31 and the roll paper during transfer.

  The cutting unit 4 includes cutters 41 and 42. The cutters 41 and 42 are provided at positions that mesh with each other, and at least one of them moves up and down to cut the roll paper that passes through this position. The cut roll paper is discharged to the outside of the image forming apparatus 100. In addition, although the cutting part 4 of this embodiment cuts roll paper in the direction orthogonal to the conveyance direction, the structure further provided with the cutter which cuts roll paper along the conveyance direction may be sufficient. .

  As shown in FIG. 3, the measurement unit 6 includes gears 61, 62, 63, a slit plate 64, and a sensor 65. The gear 61 is attached in a state of being fixed to the supply shaft 11 of the roll paper storage unit 1, and transmits the rotational force of the supply shaft 11 to the gear 62. The gears 62 and 63 transmit the rotational force from the supply shaft 11 to the slit plate 64. The slit plate 64 is a circular plate member having a gear to which the rotational force of the gear 63 is transmitted, and has an optical pattern formed by a plurality of slits arranged at equal intervals. The sensor 65 includes a light emitting element and a light receiving element, and optically reads an optical pattern formed on the slit plate 64. That is, the slit plate 64 and the sensor 65 realize a so-called rotary encoder function. The measuring unit 6 calculates the rotation angle θ (rad) of the supply shaft 11 from the number of slits read by the sensor 65 when the roll paper is conveyed by a predetermined distance d (m). The measuring unit 6 supplies the calculated value of the rotation angle θ to the control unit 7 described later.

  In addition to the above-described units, the image forming apparatus 100 includes a control unit 7 that controls the operations of these units. The control unit 7 includes a calculation device such as a CPU (Central Processing Unit) and a storage device such as a ROM (Read Only Memory) and a RAM (Random Access Memory), and executes the program stored in the storage device to execute the above-described operation. Control each part. The control system of the image forming apparatus 100 is as shown in the block diagram of FIG.

  The control unit 7 has a function of calculating the outer diameter of the roll paper wound around the supply shaft 11. Here, the “outer diameter” is a diameter when the outer peripheral surface of the roll paper wound around the supply shaft 11 is regarded as a perfect circle. The control unit 7 calculates the outer diameter φ (m) by performing the calculation shown in the following equation 1 based on the roll paper transport distance d stored in advance and the rotation angle θ supplied by the measurement unit 6. In Equation 1, π means the circumference.

  φ = d × (1 / π) × (2π / θ) = 2d / θ (Expression 1)

  The equation 1 is derived from the fact that d = π × φ × (θ / 2π) holds when the length of the arc at the rotation angle θ is d (that is, the distance d). It is.

  As apparent from Equation 1, the larger the rotation angle θ, the smaller the outer diameter φ. Therefore, the larger the value of the rotation angle θ, the smaller the amount of roll paper wound around the supply shaft 11. Conversely, the smaller the value of the rotation angle θ, the larger the outer diameter φ, which means that the amount of roll paper wound around the supply shaft 11 is large.

[2. Operation]
With the above configuration, the image forming apparatus 100 forms an image on roll paper based on image data supplied from the outside, cuts the roll paper into an appropriate size, and discharges the roll paper. Hereinafter, the operations performed when the image forming apparatus 100 forms an image will be specifically described with two examples.

[2-1. Operation example 1]
When the image forming apparatus 100 forms an image, first, the sheet conveying unit 2 supplies roll paper to the transfer unit 3. At this time, the sheet conveying section 2 rotates the feed roller 21 in the direction of arrow C in FIG. When the feed roller 21 is rotating in the direction of arrow C, the electromagnetic clutch 52 of the drive unit 5 is in a state where this rotational force is cut off, that is, in an off state.

  Subsequently, when the transfer unit 3 transfers dye or the like to the roll paper, the sheet conveying unit 2 performs transfer while moving the roll paper in the reverse direction. In other words, when viewed from the transfer unit 3, when the direction of the sheet conveying unit 2 is the upstream side and the direction of the cutting unit 4 is the downstream side, the image forming apparatus 100 performs the transfer while moving the roll paper to the upstream side. is there. At this time, the feed roller 21 rotates in the direction of the arrow D in FIG. 1, but the electromagnetic clutch 52 of the drive unit 5 remains off even when the feed roller 21 starts to rotate in this direction. Therefore, the roll paper between the feed roller 21 and the supply shaft 11 is gradually bent.

  When the feed roller 21 rotates in the direction of arrow D for a predetermined time, the electromagnetic clutch 52 is switched to a state in which a rotational force is transmitted, that is, an on state. As a result, the supply shaft 11 is rotated in the direction of arrow A in FIG. 1, and winding of the roll paper is started. As described above, the gear ratio of the drive unit 5 is adjusted so that the amount of roll paper that the supply shaft 11 takes up per unit time is larger than the amount of roll paper that the feed roller 21 sends out per unit time. Therefore, after the electromagnetic clutch 52 is switched to the on state, the bending of the roll paper is gradually eliminated.

  The on / off switching timing of the electromagnetic clutch 52 is determined based on the measurement result of the measurement unit 6. Specifically, the control unit 7 calculates the outer diameter φ from the rotation angle θ measured by the measuring unit 6, and determines the time for which the electromagnetic clutch 52 is turned on based on the value of the outer diameter φ. Yes.

FIG. 5 is a timing chart showing the control timing of the feed roller 21 and the electromagnetic clutch 52 by the control unit 7. In the drawing, FIG. 5 (a) is a timing chart of when the outside diameter phi is phi _a, FIG. 5 (b) is a timing chart of when the outside diameter phi is phi _b. Here, it is assumed that φ _a > φ _b . Time t ₁ is a time when the image forming apparatus 100 starts the transfer process, and time t ₂ is a time when the image forming apparatus 100 finishes the transfer process.

5, the control unit 7, when the outer diameter φ is large, slower than the time t _a to the electromagnetic clutch 52 in the on state the outer diameter φ is small (the time t _b), the electromagnetic The switching timing is controlled so that the time during which the clutch 52 is on is shortened. By doing in this way, the time for which the electromagnetic clutch 52 is in the on state can be shortened as the outer diameter φ is larger, and the time for which the electromagnetic clutch 52 is in the on state can be lengthened as the outer diameter φ is smaller. In other words, the rotation amount of the supply shaft 11 decreases as the outer diameter φ increases, and the rotation amount of the supply shaft 11 increases as the outer diameter φ decreases. Therefore, according to this image forming apparatus 100, the supply shaft 11 winds up the roll paper more than necessary when the outer diameter φ is large, or the feed roller 21 and the supply shaft 11 when the outer diameter φ is small. It is possible to eliminate the inconvenience of causing the roll paper to bend more than necessary.

[2-2. Operation example 2]
In the operation example 1 described above, it has been described that when the feed roller 21 rotates in the direction of the arrow C, the electromagnetic clutch 52 of the drive unit 5 is in the OFF state. However, when such an operation is performed, the bending between the feed roller 21 and the supply shaft 11 disappears as the feed roller 21 rotates, and a strong tension is eventually applied to the roll paper. Therefore, also in this case, it is desirable to cause the roll paper between the feed roller 21 and the supply shaft 11 to bend appropriately by switching the electromagnetic clutch 52 on and off.

  Specifically, similarly to the above-described operation example 1, the time for turning on the electromagnetic clutch 52 may be changed according to the outer diameter of the roll paper. In this case, the difference from the above-described operation example 1 is that in the operation example 1, the time for turning on the electromagnetic clutch 52 is different and the time for turning it off is the same. 52 is turned on with the rotation of the feed roller 21, and the time for turning it off is different.

FIG. 6 is a timing chart showing the control timing of the feed roller 21 and the electromagnetic clutch 52 in this operation example. In the drawing, FIG. 6 (a) is a timing chart of when the outside diameter phi is phi _c, FIG. 6 (b) is a timing chart of when the outside diameter phi is phi _d. Here, it is assumed that φ _c > φ _d . Time t ₁ is a time when the image forming apparatus 100 starts the transfer process, and time t ₂ is a time when the image forming apparatus 100 finishes the transfer process.

As shown in FIG. 6, when the outer diameter φ is large, the control unit 7 sets the time t _c for turning off the electromagnetic clutch 52 to be faster than when the outer diameter φ is small (time t _d ). The switching timing is controlled so that the time during which the clutch 52 is on is shortened. By doing in this way, the time for which the electromagnetic clutch 52 is in the on state can be shortened as the outer diameter φ is larger, and the time for which the electromagnetic clutch 52 is in the on state can be lengthened as the outer diameter φ is smaller. The rotation amount of the supply shaft 11 can be changed according to φ. Therefore, according to this image forming apparatus 100, the feed roller 21 winds up the roll paper more than necessary when the outer diameter φ is large, or the feed roller 21 and the supply shaft 11 when the outer diameter φ is small. It is possible to eliminate the inconvenience of causing the roll paper to bend more than necessary.

[3. Modified example]
In addition, embodiment mentioned above is one aspect | mode of implementation of this invention, and this invention is not limited to this aspect. Since the present invention has a feature in the conveyance timing of the roll paper at the time of executing the transfer process, the configuration of the transfer unit and the cutting unit is not particularly limited. In addition, the sheet storage unit, the sheet conveyance unit, the drive unit, and the measurement unit may have different points as long as they have the same effects as the above-described embodiment. For example, in the above-described embodiment, the rotation angle is detected in order to calculate the outer diameter of the roll paper. However, the outer diameter itself is detected using a contact-type or optical sensor. May be. In the above-described embodiment, the drive of the supply shaft 11 is controlled by the electromagnetic clutch 52. However, a gear configured to freely transmit and shut off power may be used.

  In the above-described embodiment, the time for switching the electromagnetic clutch 52 from the on state to the off state (in the case of the operation example 1) and the time for switching the electromagnetic clutch 52 from the off state to the on state (in the case of the operation example 2) are fed. Although the operation is performed simultaneously with the on / off of the roller 21, it is not necessary to make the on / off switching of the electromagnetic clutch 52 coincide with that of the feed roller 21. This is because there is no change in the amount that the supply shaft 11 feeds (or winds) the roll paper as long as the electromagnetic clutch 52 is in the ON state.

1 is a diagram illustrating an overall configuration of an image forming apparatus according to an embodiment of the present invention. 2 is a diagram illustrating a drive unit of the image forming apparatus. FIG. It is the figure which showed the measurement part of the image forming apparatus. 2 is a block diagram showing a control system of the image forming apparatus. FIG. 3 is a timing chart showing control timings of a feed roller and an electromagnetic clutch in the image forming apparatus. 3 is a timing chart showing control timings of a feed roller and an electromagnetic clutch in the image forming apparatus. It is a figure showing an example of a conventional image forming apparatus using roll paper. It is a figure showing an example of a conventional image forming apparatus using roll paper.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100, 900 ... Image forming apparatus, 1 ... Roll paper accommodating part, 11 ... Supply axis | shaft, 2 ... Sheet conveyance part, 21 ... Feed roller, 22 ... Pinch roller, 3 ... Transfer part, 31 ... Thermal head, 32 ... Platen roller DESCRIPTION OF SYMBOLS 4 ... Cutting part, 41, 42 ... Cutter, 5 ... Drive part, 51, 53, 54 ... Gear, 52 ... Electromagnetic clutch, 6 ... Measuring part, 61, 62, 63 ... Gear, 64 ... Slit plate, 65 ... Sensor

Claims (4)

Storage means for storing a long sheet wound around a shaft;
A drive unit that rotates the shaft of the storage unit in a first direction that feeds the sheet from the storage unit or a second direction that winds the sheet;
Conveying means driven by driving by the driving means , wherein the shaft conveys the sheet at a speed slower than a speed at which the shaft feeds the sheet, and the sheet is conveyed at a speed slower than a speed at which the shaft takes up the sheet. Conveying means for conveying
Calculating means for calculating the amount of the sheet wound around the shaft of the accommodating means;
When the driving unit causes the shaft to wind the sheet, when the amount of the sheet calculated by the calculating unit is large, the rotation amount of the shaft is smaller than when the amount of the sheet calculated by the calculating unit is small. With limiting means to reduce ,
The limiting means includes a clutch that transmits or interrupts the driving force applied to the shaft by the driving means,
When the amount of the sheet calculated by the calculating unit is large, the time for cutting off the driving force applied to the shaft is made longer than when the amount of the sheet calculated by the calculating unit is small. apparatus. When the driving unit causes the sheet to be fed to the shaft, when the amount of the sheet calculated by the calculating unit is large , the limiting unit is less than when the amount of the sheet calculated by the calculating unit is small. The sheet conveying device according to claim 1, wherein the amount of rotation of the sheet is reduced. The calculating means includes
A sensor for detecting a rotation angle of the shaft of the housing means;
The sheet is conveyed in the first direction by a predetermined distance using the conveying means, and wound around the shaft based on a rotation angle detected by the sensor when the sheet is conveyed by the distance. The sheet conveying apparatus according to claim 1, wherein the amount of the sheet that has been calculated is calculated. An image forming apparatus comprising: a sheet conveying apparatus according to any one of claims 1 to 3.

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