JP2005262877A - Printer and recording paper cutting method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a printer which can suppress occurring of a wide line at which the concentration of ink is high due to stopping of feeding of long recording paper and cutting the same, and to provide a recording paper cutting method. <P>SOLUTION: In the printer, a tension roller 47 carries the recording paper 11 on which an image is recorded by a print head, while applying a predetermined tension to the same. When a cut line on the recording paper 11 reaches a cutter location and rotation of a paper ejecting roller 51 is terminated, curl is formed between the tension roller 47 and the paper ejecting roller 51. The curl generates a reaction Fr for pressing the recording paper 11 toward the tension roller 47 by elastic force, and therefore the tension of the paper is decreased. Thus during termination of the paper ejecting roller 51, the torque of the tension roller 47 is increased and the recording paper 11 is pressed in a direction that increases the curl by a dancer roller 68, which compensates for decrease of the tension, to thereby maintain the tension at an almost constant value irrespective of rotation or termination of the paper ejecting roller 51. Thus the occurrence of the wide line causing nonuniform concentration can be prevented. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a printer and a recording paper cutting method for cutting a long recording paper into sheets during image printing.

  An image is recorded line by line by the print head to the recording area while conveying a long recording sheet, and the recorded recording area is sent to the cutter by a paper discharge roller disposed on the downstream side of the print head. A line printer that sequentially cuts for each recording area is known (for example, see Patent Document 1 below). In this line printer, a tension roller is disposed on the downstream side of the print head, and recording is performed while applying front tension to the recording paper.

  Further, when cutting the recording paper, it is preferable to stop the conveyance of the recording paper so that the cutting line does not deviate from the original position. However, if the conveyance of the entire recording paper is stopped at the time of cutting, the printing time becomes long. Therefore, in the line printer of the above-described prior art, only the conveyance of the recording paper at the cutter position is stopped while the conveyance of the recording paper at the recording position is continued, and cutting is performed. This prevents the recording position from being shifted without interrupting the recording.

However, even if cutting is performed in a state where the conveyance of the recording paper is stopped, the impact at the time of cutting is transmitted to the recording paper being recorded located on the upstream side of the cutter. Since this impact acts in the direction opposite to the transport direction, the front tension is reduced, and a thin line (line with increased density) is recorded. In order to prevent the impact at the time of cutting from being transmitted to the upstream recording paper, the line printer increases the clamping pressure at which the paper discharge roller pinches the recording paper or the tension between the paper discharge roller and the tension when cutting By deliberately curling the recording paper with the roller, the impact at the time of cutting is absorbed.
JP 2001-121863 A

  However, the above-described cutting method can prevent fine lines that occur during cutting, but cannot suppress the generation of wide lines with high density due to the stop of the paper discharge roller.

  An object of the present invention is to provide a printer with a cutter and a recording paper cutting method capable of suppressing the generation of a wide line having a high density due to stopping and cutting a long recording paper.

  A printer according to the present invention includes at least one print head that continuously records a plurality of images on a long recording paper being conveyed, and a cutter that cuts the recording paper for each image. A tension roller that is disposed downstream of the print head and conveys the recording paper while applying a front tension while the print head records an image on the recording paper, and between the tension roller and the cutter. And the recording paper that has passed through the tension roller is transported toward the cutter, and while the cutter is cutting the recording paper, the rotation is stopped and between the tension roller and A paper discharge roller that forms the curl of the recording paper, and a large torque is applied to the tension roller while the paper discharge roller is stopped, The front tension, characterized in that a torque control means for substantially the same as that during rotation of the discharge roller.

  Preferably, the torque control means increases the torque of the tension roller during a period from when the paper discharge roller is stopped or immediately before it until the curl disappears due to re-rotation of the paper discharge roller.

  The torque control unit includes, for example, a motor that drives the tension roller, and a motor controller that controls the torque of the tension roller by controlling the rotational force of the motor.

  The rotation speed of the paper discharge roller is preferably faster than that of the tension roller.

  Furthermore, it is preferable to provide a reaction force absorbing device that is disposed between the tension roller and the paper discharge roller and absorbs a reaction force acting on the recording paper so as to reduce the front tension by the curl.

  The reaction force absorbing device urges the dancer roller so that the dancer roller can move in a direction intersecting the conveyance direction of the recording paper and the dancer roller follows the curl and presses the recording paper. It is preferable to consist of a spring.

  The reaction force absorbing device further includes a guide plate that guides the leading edge of the recording paper toward the paper discharge roller, and the guide plate is opposed to the dancer roller and passes through the leading edge of the recording paper. After that, it is preferable to swing to a position away from the dancer roller.

  It is preferable that the dancer roller is held at a retracted position against the spring, and the holding is released in conjunction with the swing of the guide plate.

  A printer according to the present invention includes at least one print head that continuously records a plurality of images on a long recording paper being conveyed, and a cutter that cuts the recording paper for each image. A tension roller that is disposed downstream of the print head and conveys the recording paper while applying a front tension while the print head records the image on the recording paper, and the tension roller and the cutter. The recording paper disposed between and transporting the recording paper that has passed through the tension roller toward the cutter, and while the cutter is cutting the recording paper, the rotation is stopped so that the recording paper is not in contact with the tension roller. A paper discharge roller for forming a curl of the recording paper, and between the tension roller and the paper discharge roller. Te, characterized in that a reaction force absorbing device for absorbing the reaction force acting on the recording paper so as to reduce the front tension.

  The reaction force absorbing device includes, for example, a dancer roller that can move in a direction crossing a conveyance direction of the recording paper, and the dancer roller so that the dancer roller follows the curl and presses the recording paper. It consists of an energizing spring.

  The recording paper cutting method of the present invention is a recording paper cutting method for cutting a long recording paper on which a plurality of images are continuously recorded by at least one print head for each image with a cutter. A step of conveying the recording paper recorded by the print head while applying tension by a tension roller disposed downstream of the head, and a paper discharge roller disposed between the tension roller and the cutter. A step of conveying the recording sheet toward the cutter, and the tension roller and the discharge roller by stopping rotation of the discharge roller when a cutting line on the recording sheet reaches the position of the cutter. Forming a curl of the recording paper between the cutting line and operating the cutter to place the recording paper on the cutting line. A step of disconnection, characterized by comprising the step of compensating the reduction of the front tension by the curl.

  The step of compensating for the decrease in the front tension is preferably executed within a period from when the paper discharge roller stops or immediately before the curl disappears due to re-rotation of the paper discharge roller.

  The step of compensating for the decrease in front tension preferably increases the torque of the tension roller.

  In the step of compensating for the decrease in the front tension, it is preferable that the recording paper is pressed in a direction in which the curl is increased by a dancer roller disposed between the tension roller and the paper discharge roller.

  According to the present invention, at least when the paper discharge roller is stopped, the torque of the tension roller is increased and / or the recording paper is pushed in the direction in which the curl increases, so that the decrease in the front tension due to the curl is compensated. Therefore, the front tension is maintained almost constant regardless of the rotation or stop of the paper discharge roller. As a result, it is possible to prevent a wide line having density unevenness from occurring on the recording paper.

  In FIG. 1, a color thermal printer (hereinafter simply referred to as a printer) 10 is loaded with a recording paper roll 12 in which a long color thermal recording paper (hereinafter simply referred to as a recording paper) 11 is rolled. The paper feed roller 13 contacts the outer periphery of the recording paper roll 12 and rotates it to feed the recording paper 11 into the transport path from the paper feed unit to the paper discharge port. Further, after the printing is completed, the paper feed roller 13 reverses and the recording paper 11 is rewound onto the recording paper roll 12. The paper feed roller 13 is rotated by a stepping motor (STM) 14.

  As is well known, the recording paper 11 has a cyan thermosensitive coloring layer, a magenta thermosensitive coloring layer, and a yellow thermosensitive coloring layer sequentially provided on a support. The yellow thermosensitive coloring layer, which is the uppermost layer, has the highest thermal sensitivity and develops yellow with a small amount of heat energy. The cyan thermosensitive coloring layer, which is the lowermost layer, has the lowest thermal sensitivity and develops cyan with large heat energy. The yellow thermosensitive coloring layer loses its coloring ability when irradiated with near ultraviolet rays of 420 nm. The magenta thermosensitive coloring layer develops magenta with intermediate thermal energy between the yellow thermosensitive coloring layer and the cyan thermosensitive coloring layer and loses the coloring ability when irradiated with 365 nm ultraviolet rays. For example, a black thermosensitive coloring layer may be provided on the recording paper 11 to form a four-layer structure.

  The recording paper 11 drawn from the recording paper roll 12 passes between the capstan roller 18 and the pinch roller 19 of the back tension roller pair 17. When a sensor (not shown) arranged on the downstream side of the back tension roller pair 17 detects the leading edge of the recording paper 11, a shift mechanism (not shown) is activated to move the pinch roller 19 to the capstan roller 18. The recording paper 11 is sandwiched by pressing.

  The capstan roller 18 is rotated by a DC motor (not shown), and conveys the recording paper 11 toward the downstream alignment roller 21. The alignment roller 21 corrects the positional deviation of the recording paper 11 in the width direction.

  A conveyance roller pair 23 for controlling the conveyance speed of the recording paper 11 is disposed on the downstream side of the alignment roller 21. When the recording paper 11 passes between the capstan roller 24 and the pinch roller 25 of the transport roller pair 23 and the leading end thereof is detected by a sensor (not shown) disposed on the downstream side of the transport roller pair 23, A shift mechanism (not shown) is operated to bring the pinch roller 25 into pressure contact with the capstan roller 24. The capstan roller 24 is rotated by the stepping motor 14 and conveys the recording paper 11 toward the downstream side.

  A yellow printing unit 30 is disposed on the downstream side of the conveyance roller pair 23. The yellow printing unit 30 is in contact with the recording paper 11 to print a yellow thermal head 31 for printing a yellow image on the yellow thermosensitive coloring layer, a platen roller 32 for sandwiching the recording paper 11 between the thermal head 31, and the recording paper. 11 and a front tension roller pair 33 that conveys the paper 11 while sandwiching it.

  The recording paper 11 conveyed by the conveying roller pair 23 passes between the thermal head 31 and the platen roller 32 and between the capstan roller 33a and the pinch roller 33b of the front tension roller pair 33. When the leading edge of the recording paper 11 is detected by a sensor (not shown) disposed on the downstream side of the front tension roller pair 33, a shift mechanism (not shown) is activated and the pinch roller 33b is moved to the capstan roller. Press contact 33a. At the same time, the thermal head 31 is pressed against the recording paper 11.

  The front tension roller pair 33 applies tension (front tension) acting in the transport direction to the recording paper 11 at the recording position of the thermal head 31. The capstan roller 33a is driven by a DC motor 34. The rotational speed of the front tension roller pair 33 is set to be faster than the rotational speed of the transport roller pair 23, and the front tension is applied to the recording paper 11 by this speed difference. A back tension equivalent to the front tension is applied to the recording paper 11 by the back tension roller pair 17. For this reason, since the conveyance amount of the recording paper 11 is controlled by the conveyance roller pair 23, the conveyance speed of the recording paper 11 at the recording position of the thermal head 31 is kept at the conveyance speed by the conveyance roller pair 23.

  When the leading edge of the top recording area on the recording paper 11 reaches the thermal head 31, the thermal head 31 operates to print a yellow image line by line on the yellow thermosensitive coloring layer of the recording paper 11.

  A yellow fixing lamp 35 is disposed on the downstream side of the front tension roller pair 33. The yellow fixing lamp 35 emits near-ultraviolet light having an emission peak of 420 nm and fixes the yellow thermosensitive coloring layer of the recording paper 11 so as not to develop color even when heated.

  The color thermosensitive recording paper 11 on which the yellow thermosensitive coloring layer is fixed by the yellow fixing lamp 35 is conveyed to the magenta printing unit 37. Similar to the yellow printing unit 30, the magenta printing unit 37 presses the recording paper 11 between the thermal head 38 and the magenta thermal head 38 that presses the recording paper 11 and prints a magenta image on the magenta thermosensitive coloring layer. It comprises a platen roller 39 that sandwiches and a front tension roller pair 40 that sandwiches and conveys the recording paper 11. The front tension roller pair 40 is driven by a DC motor 41.

  The recording paper 11 on which the magenta image is printed by the magenta printing unit 37 is irradiated with ultraviolet light having an emission peak of 365 nm by the magenta fixing lamp 42 disposed downstream, and the magenta thermosensitive coloring layer is fixed.

  The recording paper 11 on which the magenta thermosensitive coloring layer is fixed by the magenta fixing lamp 42 is conveyed to the cyan printing unit 44. Similar to the yellow printing unit 30 and the magenta printing unit 37, the cyan printing unit 44 includes a cyan thermal head 45, a platen roller 46, and a front tension roller pair 47. The front tension roller pair 47 is driven by a DC motor 48. The cyan printing unit 44 prints a cyan image on the cyan thermosensitive coloring layer of the recording paper 11. Then, the yellow, magenta, and cyan images are printed in one recording area so as to form a full-color image.

  Further, each time the front tension roller pair 33, 40, 47 of each printing unit is operated, the front tension on the downstream side of the transport roller pair 23 increases. However, since the back tension generated by the back tension roller pair 17 increases in accordance with the operation of each front tension roller pair 33, 40, 47, the transport speed of the transport roller pair 23 is always maintained constant.

  Each of the thermal heads 31, 38, and 45 records the images of the respective colors in the surface order in the respective recording areas of the recording paper 11. In this way, a plurality of recording areas are continuously recorded, and a plurality of images (frames) are formed on the recording paper 11. In this recording, a margin of the same length as the distance between each front tension roller pair and each thermal head is formed at the leading edge of each of the plurality of recording areas. This margin is cut by a cutter 57 described later.

  On the downstream side of the cyan printing unit 44, a paper discharge roller pair 51 for sending a recorded area in which a full-color image is recorded to the cutter 57 is disposed. The paper discharge roller pair 51 includes a capstan roller 51a and a pinch roller 51b. The capstan roller 51a is driven by a stepping motor 55.

  A cutter 57 that cuts the recording paper 11 at the edge of each recording area is disposed on the downstream side of the paper discharge roller pair 51. The cutter 57 moves in a rotating manner in a direction perpendicular to the conveyance direction of the recording paper 11 while being in sliding contact with the fixed blade 58 arranged in a direction orthogonal to the conveyance direction of the recording paper 11. It consists of a rotary blade 59. The rotary blade 59 is moved by a cutter moving mechanism (not shown) including a belt and a pulley.

  In the recording paper 11, first, the leading edge of the recorded area is sent to the cutting position of the cutter 57, and the blank portion generated at the top of the recording paper 11 is cut. Thereafter, the rear end of the recorded area is conveyed to the cutting position of the cutter 57, and the recorded area is cut into a sheet shape. Such a cutting operation is repeated for each recorded area.

  The cutting operation is performed in a state where the discharge roller pair 51 is stopped and the conveyance of the cut portion of the recording paper 11 is stopped so that the cutting line is not shifted. Even at the time of this cutting, the conveyance roller pair 23 continues to convey the recording paper 11, and recording is performed by the printing units 30, 37, and 44. In this way, the printing time is shortened.

  However, when the conveyance of a part of the recording paper 11 is stopped or the conveyance is restarted for cutting as described above, the tension applied to the recording paper 11 at the recording position fluctuates, and the next Such a high density line is generated on the image.

  First, when the paper discharge roller pair 51 is stopped, a reaction force (drag) that inhibits the conveyance by the front tension roller pair 47 is generated due to the rigidity of the recording paper. This reaction force at the time of stopping acts instantaneously and generates a relatively sharp and narrow line on the image.

  Second, when the conveyance by the paper discharge roller pair 51 is stopped, the recording paper 11 is curled between the front tension roller pair 47 and the paper discharge roller pair 51. Since the recording paper 11 is relatively thick, a restoring force is generated by an elastic force. This restoring force acts as a reaction force in the direction opposite to the front tension. Since this restoring force is generated during curling, a wide line is generated on the image. These reaction forces act so as to reduce the conveying speed of the recording paper 11, so that the density of the portion being recorded is higher than the surroundings, and a wide line is formed on the image.

  Therefore, the printer 10 is provided with a reaction force absorbing device 66 between the front tension roller pair 47 and the paper discharge roller pair 51 for suppressing the fluctuation of the tension on the recording paper 11 and preventing the two types of lines from occurring. Has been.

  As shown in FIG. 2, the reaction force absorbing device 66 includes a guide plate 67, a dancer roller unit 68, a holding mechanism 69, and a spring 71. In the dancer roller unit 68, a dancer roller 68a and a guide roller 68b are connected by an arm 68c, and the arm 68c is provided so as to be swingable around a rotation shaft of the guide roller 68b. As shown by a two-dot chain line in the figure, the spring 71 urges the arm 68c so that the dancer roller 68a swings clockwise around the guide roller 68b. With this urging force, the dancer roller 68a presses the recording paper 11 from the back surface. If the recording paper 11 is curled when the paper discharge roller pair 51 is stopped, the dancer roller 68a swings so as to follow the curl.

  The guide plate 67 is disposed at a position facing the dancer roller unit 68 and guides the recording paper 11 fed from the front tension roller pair 47 to the paper discharge roller pair 51. The guide plate 67 is provided so as to be swingable about a shaft 67b. When the dancer roller 68a swings, the guide plate 67 swings up in a clockwise direction so that a space for the swing is secured.

  When the dancer roller unit 68 passes the leading edge of the recording paper 11, the holding mechanism 69 moves the leading end of the recording paper 11 conveyed from the front tension roller pair 47 to a predetermined position indicated by a solid line in the drawing. Retained. The holding mechanism 69 holds the dancer roller unit 68 at the predetermined position against the urging force of the spring 71.

  As the holding mechanism 69, for example, a solenoid that pushes the movable iron core (plunger) by passing an electric current through the electromagnetic coil is used. One end of the plunger is fixed to the guide plate 67, and the guide plate 67 swings as the plunger moves. The guide plate 67 is provided with a contact portion 67 a that contacts the arm 68 c of the dancer roller unit 68, and the dancer roller unit 68 is pressed against the contact portion 67 a by the bias of the spring 71. When the holding by the holding mechanism 69 is released and the guide plate 67 swings in the clockwise direction and jumps upward, the dancer roller 68a can also swing in the clockwise direction following this. Then, when printing is completed and the recording paper 11 is rewound onto the recording paper roll 12, the holding mechanism 69 operates to swing the guide plate 67 counterclockwise. At this time, the dancer roller unit 68 is pushed by the contact portion 67a and returns to a predetermined position.

  Further, during the cutting process (a period from the stop of the paper discharge roller pair 51 to the disappearance of the curl), the torque of the front tension roller pair 47 is increased in addition to the pressing of the dancer roller 68a. By doing so, the reaction force opposite to the front tension is absorbed, so that the front tension during printing and the cutting process period is kept substantially constant. Occurrence is more reliably prevented.

  The DC motor 48 is controlled by the controller 77 via the driver 76. The controller 77 is a microcomputer composed of a CPU and a memory, and comprehensively controls each unit of the printer 10. The controller 77 increases the drive voltage of the DC motor 48 to increase the torque of the front tension roller pair 47 immediately before stopping the rotation of the paper discharge roller pair 51, and after the cutting process period ends, the original drive voltage Return to.

  Further, the pinch roller 51b of the paper discharge roller pair 51 moves between a pressure contact position where the shift mechanism 79 is pressed against the recording paper 11 and a retreat position where the paper is retracted from the pressure contact position. The shift mechanism 79 is controlled by the controller 77. When the top of the recording paper 11 is detected by the photo sensor 81, the controller 77 operates the shift mechanism 79 to shift the pinch roller 51b to the press contact position.

  The controller 77 also controls a stepping motor 55 that drives the paper discharge roller pair 51 via a driver 78. The timing for stopping the pair of paper discharge rollers 51 is to measure the conveyance amount of the recording paper 11 by counting the drive pulses that the controller 77 gives to the stepping motor 55 after the leading edge of the recording paper 11 is detected by the photo sensor 81. Is done by doing. That is, the controller 77 starts counting drive pulses from the time when the leading edge of the recording paper 11 is detected, and stops the rotation of the paper discharge roller pair 51 when the cutting position reaches the position of the cutter 57.

  The rotational speed of the paper discharge roller pair 51 is set to be faster than that of the front tension roller pair 47. Therefore, after the cutting operation by the cutter 57, the paper discharge roller pair 51 starts to rotate again, and the paper discharge roller When the conveyance of the recording paper 11 by the pair 51 is resumed, the bending of the recording paper 11 is gradually eliminated. Along with this, the dancer roller 68a is pushed down.

  FIG. 3 is an explanatory diagram for explaining the operation of the reaction force absorbing device 66 and the front tension roller pair 47 during the cutting process. The operation of the above configuration will be described with reference to this figure.

  The fed recording paper 11 is conveyed at a predetermined speed by the conveying roller pair 23. During this conveyance, thermal recording and optical fixing of images are performed by the respective printing units 30, 37, and 44. In each of the printing sections 30, 37, and 44, the recording paper 11 is subjected to thermal recording while being given a predetermined front tension by each front tension roller pair 33, 40, and 47.

  As shown in FIG. 3A, when the recording of the cyan image is completed, the head of the recording paper 11 is sent to the paper discharge roller pair 51 while being guided by the guide plate 67. At this time, the dancer roller unit 68 is held by the holding mechanism 69 at a predetermined position where the arm 68c is horizontal, and the pressure on the recording paper 11 by the dancer roller 68a is suppressed. When the leading edge of the recording paper 11 passes through the paper discharge roller pair 51 and is detected by the photo sensor 81, the pinch roller 51b is shifted to the press contact position as shown in FIG. Since the capstan roller 51a is rotating, when the paper discharge roller pair 51 nips the recording paper 11, the driving force Fd of the paper discharge roller pair 51 is applied to the recording paper 11.

  At this time, the guide plate 67 is swung clockwise by the holding mechanism 69 and is flipped upward. Thereby, the dancer roller 68a pressed by the contact portion 67a of the guide plate 67 can swing. The dancer roller 68 a presses the recording paper 11 from the back surface by the bias of the spring 71.

  At the same time, the controller 77 increases the driving voltage of the DC motor 48 and increases the torque of the front tension roller pair 47. As a result, the front tension Ft of the front tension roller pair 47 is increased to Ft ′. This torque increase of the front tension roller pair 47 is continued until the cutting operation is completed, and then the rotation of the paper discharge roller pair 51 is restarted until the curling of the recording paper generated during the stop is eliminated. .

  When the cutting position of the recording paper 11 reaches the position of the cutter 57, as shown in FIG. 3C, the rotation of the discharge roller pair 51 is stopped, and the recording paper 11 is conveyed at the position of the cutter 57. Stopped. At the moment when the rotation of the paper discharge roller pair 51 stops, the front tension decreases due to the drag of the recording paper 11, but immediately before this stop, the torque of the front tension roller pair 47 is increased, and the dancer roller Since the recording paper 11 is urged to curl by 68, the occurrence of a narrow line due to the stop of the paper discharge roller pair 51 is prevented.

  Even after the discharge roller pair 51 is stopped, since the recording paper 11 is continuously conveyed by the front tension roller 47, the recording paper 11 is bent. The dancer roller 68 a swings following the bending of the recording paper 11 and continues to press the recording paper 11. When the recording paper 11 is curled, a reaction force Fr due to the restoring force of the recording paper 11 is generated. Since this reaction force Fr hinders the conveyance of the recording paper 11, it acts to reduce the tension by the front tension roller pair 47. However, since the torque of the front tension roller pair 47 is increased and the pressing force Fs is generated by the dancer roller 68a, a decrease in tension due to the reaction force Fr is suppressed. In this state, the tension by the tension roller pair 47 is Ft ″. Since the tensions Ft ′ and Ft ″ are almost the same as the tension Ft, fluctuations in tension caused by the stop of the paper discharge roller pair 51 are suppressed. Thereby, the generation of a wide line due to the reaction force Fr is prevented.

  When the cutter 57 enters the cutting operation, an acting force is exerted on the recording paper 11 by the rotary blade 59. This acting force is blocked by the bending of the paper discharge roller pair 51 and the recording paper 11, and thus is caused by the cutting operation. No line is generated.

  When the cutting operation is completed, the discharge roller pair 51 starts to rotate again, and the conveyance of the recording paper 11 by the discharge roller pair 51 is resumed. Since the rotation speed of the discharge roller pair 51 is faster than that of the front tension roller pair 47, the curl of the recording paper 11 is gradually reduced. Along with this, the dancer roller 68a also returns to the predetermined position shown in FIG. When a sensor (not shown) detects that the dancer roller has returned to a predetermined position, the controller 77 reduces the torque of the front tension roller pair 47 to a predetermined value.

  When the next cutting position reaches the cutter 57, the paper discharge roller pair 51 is stopped again, and the recording paper 11 is cut. As described above, the controller 77 increases the front tension by increasing the torque of the front tension roller pair 47 immediately before the discharge roller pair 51 stops. Further, when the recording paper 11 is stopped, the dancer roller 68a curls the recording paper 11.

  In the above-described embodiment, fluctuations in the front tension are prevented by both pressing by the dancer roller and torque increase of the tension roller pair, but fluctuations in the front tension may be prevented by only one of them.

  However, by using both of the dancer roller and the torque up of the tension roller pair, it is possible to suppress the tension fluctuation that occurs when the rotation of the paper discharge roller pair is resumed after the cutting operation is completed.

  That is, in order to oppose the reaction force Fr due to curl only with the dancer roller 68a, it is necessary to increase the urging force of the spring 71 and increase the pressing force Fs. However, the pressing force Fs of the dancer roller 68a acts as a back tension on the paper discharge roller pair 51. Therefore, when the pressing force Fs is increased, the load on the paper discharge roller pair 51 is increased accordingly. End up. When the load of the paper discharge roller pair 51 increases, the recording paper 11 is not properly conveyed by the paper discharge roller pair 51, and the recording paper 11 may jam in the paper discharge path.

  As a measure for preventing this jamming, it is conceivable to increase the driving force Fd of the paper discharge roller pair 51. However, if the driving force Fd of the paper discharge roller pair 51 is increased too much, after the curl disappears, the pulling force of the recording paper 11 by the paper discharge roller pair 51 becomes too strong. This increases the front tension, which causes a reduction in image density.

  Taking this density reduction into consideration, the pressing force Fs of the dancer roller 68a cannot be made much larger than the driving force Fd of the paper discharge roller pair 51. For example, the pressing force Fs is about 1 / of the driving force Fd. It is suppressed to about 2. However, with this pressing force Fs, an increase in front tension sufficient to counteract the reaction force Fr cannot be obtained, and the shortage is compensated for by increasing the torque of the front tension roller pair 47. Even if the torque of the front tension roller pair 47 is increased, there is no load on the paper discharge roller pair 51, so there is no need to increase the driving force Fd of the paper discharge roller pair 51. For this reason, fluctuations in tension when the rotation of the discharge roller pair 51 is resumed are suppressed.

  In the above embodiment, considering the response delay of the DC motor 48, the torque of the front tension roller pair 47 is increased immediately before the rotation of the paper discharge roller pair 51 stops, but when there is no response delay, The torque may be increased simultaneously with the rotation of the paper discharge roller. Further, after the curling disappears due to the rotation of the paper discharge roller pair 51, the guide plate 67 may be returned to the position of FIG. 3A by the holding mechanism 69 to hold the dancer roller unit 68. In this case, simultaneously with the torque increase of the front tension roller pair 47, the holding mechanism 69 is operated as described above to make the guide plate 67 free.

  Although the above embodiment is an example applied to a color thermal printer, yellow, magenta, and cyan color ink sheets are used, and these ink sheets are heated with a thermal head to transfer the ink to the recording paper. The present invention can also be applied to a sublimation type recording image and a thermal melting type thermal transfer printer. Of course, the present invention can also be applied to a thermal transfer printer provided with an overcoat thermal head in addition to yellow, magenta, and cyan thermal heads.

  Further, the present invention is not limited to a thermal printer using a thermal head, and various types of recording an image on a plurality of recording areas while conveying a long recording paper and cutting a recorded portion during the recording. Applicable to printers. Furthermore, the present invention can also be applied to a printer that uses one print head and cuts a recorded portion that has already been recorded with a cutter during recording by the print head.

1 is a configuration diagram illustrating an outline of a color thermal printer. FIG. It is a block diagram of a reaction force absorption device. It is operation | movement explanatory drawing of a cutting process period.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Color thermal printer 11 Recording paper 47 Front tension roller pair 66 Reaction force absorption device 68 Dancer roller 51 Paper discharge roller pair 57 Cutter

Claims (14)

In a printer comprising at least one print head for continuously recording a plurality of images on a long recording paper being conveyed, and a cutter for cutting the recording paper for each image,
A tension roller that is arranged downstream of the print head and conveys the recording paper while applying a front tension while the print head records an image on the recording paper;
The recording paper, which is disposed between the tension roller and the cutter, conveys the recording paper that has passed through the tension roller toward the cutter, and stops rotating while the cutter is cutting the recording paper. A paper discharge roller for forming a curl of the recording paper between the tension roller,
Torque control means for applying a large torque to the tension roller while the paper discharge roller is stopped so that the front tension is substantially the same as that during rotation of the paper discharge roller. Printer.   The torque control means increases the torque of the tension roller during a period from when the paper discharge roller stops or immediately before it until the curl disappears due to re-rotation of the paper discharge roller. Item 1. The printer according to Item 1.   The said torque control means consists of a motor which drives the said tension roller, and a motor controller which controls the torque of the said tension roller by controlling the rotational force of this motor. Printer.   The printer according to claim 1, wherein a rotation speed of the paper discharge roller is faster than that of the tension roller.   And a reaction force absorbing device that is disposed between the tension roller and the paper discharge roller and absorbs a reaction force acting on the recording paper so as to reduce the front tension by the curl. The printer according to claim 1.   The reaction force absorbing device urges the dancer roller so that the dancer roller can move in a direction intersecting the conveyance direction of the recording paper and the dancer roller follows the curl and presses the recording paper. 6. The printer according to claim 5, comprising a spring.   The reaction force absorbing device further includes a guide plate that guides the leading edge of the recording paper toward the paper discharge roller, and the guide plate is opposed to the dancer roller and passes through the leading edge of the recording paper. 7. The printer according to claim 5, wherein the printer swings to a position away from the dancer roller.   8. The printer according to claim 6, wherein the dancer roller is held at a retracted position against the spring, and the holding is released in conjunction with a swing of the guide plate. In a printer comprising at least one print head for continuously recording a plurality of images on a long recording paper being conveyed, and a cutter for cutting the recording paper for each image,
A tension roller that is arranged downstream of the print head and conveys the recording paper while applying a front tension while the print head records the image on the recording paper;
The recording paper, which is disposed between the tension roller and the cutter, conveys the recording paper that has passed through the tension roller toward the cutter, and stops rotating while the cutter is cutting the recording paper. A paper discharge roller for forming a curl of the recording paper between the tension roller,
A reaction force absorbing device is provided between the tension roller and the paper discharge roller and absorbs a reaction force acting on the recording paper so as to reduce the front tension by the curl. Printer.   The reaction force absorbing device urges the dancer roller movable in a direction intersecting the recording paper conveyance direction and the dancer roller so that the dancer roller follows the curl and presses the recording paper. The printer according to claim 9, further comprising a spring. In a recording paper cutting method for cutting a long recording paper on which a plurality of images are continuously recorded by at least one print head, for each image with a cutter,
Transporting the recording paper recorded by the print head while applying tension by a tension roller disposed downstream of the print head; and
Conveying the recording paper toward the cutter by a paper discharge roller disposed between the tension roller and the cutter;
Forming a curl of the recording paper between the tension roller and the paper discharge roller by stopping the rotation of the paper discharge roller when the cutting line on the recording paper reaches the position of the cutter; When,
Activating the cutter to cut the recording paper on the cutting line;
And a step of compensating for a decrease in the front tension due to the curl.   The step of compensating for the decrease in the front tension is performed within a period from when the paper discharge roller stops or immediately before the curl disappears due to re-rotation of the paper discharge roller. Item 12. A recording paper cutting method according to Item 11.   13. The recording paper cutting method according to claim 11, wherein the step of compensating for the decrease in the front tension increases the torque of the tension roller. The step of compensating for the decrease in the front tension presses the recording paper in a direction in which the curl increases by a dancer roller disposed between the tension roller and the paper discharge roller. Item 14. The recording paper cutting method according to any one of Items 11 to 13.

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