JP4609009B2 - Image forming apparatus - Google Patents

Description

  The present invention relates to an image forming apparatus for forming an image on an image forming medium, and more particularly to a thermal printer that forms an image using a thermal head while conveying the image forming medium.

  As such a printer, for example, a color thermal printer described in Patent Document 1 described below includes three thermal heads capable of individually developing colors of yellow, magenta, and cyan, and is a long printer fed from a paper roll. A color image can be formed while conveying paper (corresponding to an image forming medium). However, when the three thermal heads are pressed against the paper in order from the one where the paper reaches the image forming position, the image may deteriorate due to load fluctuations during paper transport. The printer starts image formation with all three thermal heads pressed against the paper.

  However, in this printer, since image formation is started with the vicinity of the leading edge of the paper being pressed by the most downstream thermal head, it is hung between the most upstream thermal head and the most downstream thermal head. There is a problem in that an image is not formed in the passed portion, and a large amount of blank space is generated, which wastes paper.

  On the other hand, the color thermal printer described in Patent Document 2 below forms a yellow image while pulling back the paper after the thermal paper having a length of one frame is sent out from the paper roll. Are alternately carried out to form a magenta image at the second pull-back and a cyan image at the third pull-back. The color thermal printer described in Patent Document 3 below includes three thermal heads of yellow, magenta, and cyan, and after feeding a predetermined amount of paper from a paper roll, forms an image while pulling back the paper. To do.

  FIG. 9 is a diagram showing a configuration of an image forming unit of a conventional color thermal printer that forms an image while pulling back the paper once sent out as described above. In the image forming unit, three head units 101 to 103 that respectively form images corresponding to cyan, magenta, and yellow are sequentially arranged along the paper conveyance path. Each of the head units 101 to 103 includes thermal heads 101a to 103a and platen rollers 101b to 103b, respectively, and is arranged between the guide plates 105 constituting the paper transport path.

  In image formation, after a predetermined amount of paper is conveyed downstream of the head unit 103 along the delivery direction A by a pair of conveyance rollers (not shown), the paper is conveyed along the pull-back direction B while the head unit is conveyed. 103 are performed in order from the yellow image. According to such a configuration, an image is formed by pressing the thermal head while pulling back the paper once sent out, thereby avoiding deterioration of the image due to load fluctuation during paper conveyance and generating a large margin. Without wasting paper.

However, in the above-described printer, in order to perform paper feeding for preparing image formation and paper withdrawal for image formation, a retracted position where the thermal heads 101a to 103a are not pressed against the paper when the paper is fed. In addition, when the paper is pulled back, the thermal heads 101a to 103a need to be positioned at the image forming positions where the thermal heads 101a to 103a are pressed against the paper to form images. As a result, a gap is formed between each of the thermal heads 101a to 103a located at the retracted position and the guide plate 105, and when the paper is fed out, the leading end portion of the paper whose traveling direction is unstable is easily clogged with the gap. There was a problem.
Japanese Patent Application Laid-Open No. 8-174476 JP-A-9-99572 JP 2001-246769 A

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an image forming apparatus capable of preventing clogging of an image forming medium when an image is formed while the image forming medium is once sent out and then pulled back. Is to provide.

In order to solve the above problems, an image forming apparatus according to the present invention includes a medium storage unit that stores a long image forming medium, and a transport mechanism that transports the image forming medium stored in the medium storage unit along a transport path. And at least one head unit provided in the middle of the transport path and capable of forming an image on an image forming medium; and an image formed in pressure contact with the image forming medium provided in the head unit and transported by the transport mechanism. An image forming head configured to be displaceable between a formable image forming position and a retracted position not pressed against the image forming medium transported by the transport mechanism, and a predetermined amount of image forming pulled out from the medium accommodating portion After the medium is conveyed in the first direction from the medium accommodating portion toward the head unit, the image forming medium is conveyed in the second direction opposite to the first direction. And a transport control means for controlling the transport mechanism, and when the image forming medium is transported in the first direction, the image forming head is disposed in the retracted position, and the image forming medium is disposed in the second position. An image for controlling the head unit so that an image is formed on the image forming medium conveyed in the second direction by disposing the image forming head at the image forming position when conveyed in the direction. And a guide plate disposed so as to face a surface to be formed of the image forming medium conveyed to the head unit by the conveying mechanism when the image forming medium is conveyed in the first direction. when provided in the gap between the guide plate and the image forming head, when the imaging head is in said retracted position, in the vicinity of the first direction upstream side of the image forming head, An image forming medium conveyed in serial first direction and a guide portion inducible along the transport path.

  According to such a configuration, after the image forming medium is conveyed in the first direction from the medium accommodating portion toward the head unit, an image can be formed while the image forming medium is conveyed in the second direction. Therefore, it is possible to avoid the deterioration of the image due to the load fluctuation during the conveyance of the image forming medium, and it is possible to prevent the waste of the image forming medium without generating a large blank portion. When the image forming medium is transported in the first direction, the image forming head is disposed in the retracted position, so that a gap is formed near the upstream side in the first direction of the image forming head. In the image forming apparatus according to the present invention, when the image forming head is in the retracted position, the image forming head has a guide portion that can guide the image forming medium along the transport path in the vicinity of the upstream side in the first direction. It is possible to prevent the leading end portion of the image forming medium conveyed in the first direction from clogging the gap.

  In the above, it is preferable that the guide unit is provided in the head unit and configured to be contactable over the entire width of the image forming medium conveyed by the conveyance mechanism.

  According to such a configuration, the leading end of the image forming medium conveyed in the first direction is reliably guided along the conveying path, and the gap formed by the image forming head disposed at the retracted position is The clogging of the image forming medium can be effectively prevented.

  In the above, it is preferable that the guide unit is fixed to a portion of the head unit that is not displaced by the displacement of the image forming head.

  According to such a configuration, the guide unit is not displaced by the displacement of the image forming head between the image forming position and the retracted position. Therefore, when the image forming head is arranged at the image forming position, the guide unit conveys the image forming medium without excessively pressing the image forming medium conveyed in the second direction or obstructing the conveyance. It can be smoothly transported along the route.

In the above, it protrudes from the guide plate to said image forming medium side, by the guide portion upstream of the said first direction upstream vicinity of the imaging head, to the formation surface of the imaging medium It is preferable to provide a guide roller that can be contacted.

By providing a guide roller which projects the image forming medium side than the guide plate opposite to the formation surface of the images forming medium, even when conveying the image forming medium with a curl (curl habit), guide rollers times The surface on which the image forming medium is formed can be pressed while moving, and the contact between the surface to be formed and the guide plate can be suppressed to prevent the surface to be formed from being damaged. In addition, the guide roller can contact the surface on which the image forming medium is formed in the vicinity of the upstream side of the image forming head in the first direction, so that the leading end of the image forming medium conveyed in the first direction is conveyed. It is possible to prevent clogging of the image forming medium in the gap formed by guiding along the path and disposing the image forming head at the retracted position.

  In the above, it is preferable that the conveyance path is configured along an arc.

  By configuring the transport path along an arc, the image forming apparatus can be configured compactly. In such a case, the leading end of the image forming medium transported by the transport mechanism faces the outer peripheral side of the arc. The above-described configuration of the present invention can be particularly useful because the gap formed by the image forming head disposed at the retracted position is easily clogged.

  In the above, when the plurality of head units are arranged in series along the conveyance path, and all of the image forming heads of the plurality of head units are conveyed in the first direction. What is arrange | positioned at the said save position is preferable.

  By arranging a plurality of head units in series along the conveyance path, for example, even when a plurality of color images are formed, it is only necessary to reciprocate the image forming medium once, and the conveyance loss can be reduced. In such a case, since the traveling direction of the leading end of the image forming medium is likely to become unstable due to an increase in the conveyance distance, and clogging is likely to occur in the gap formed by the image forming head being disposed at the retracted position. The configuration of the present invention described above can be particularly useful.

  A preferred embodiment of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is an external perspective view of the image forming apparatus according to the present embodiment. This image forming apparatus is a thermal sublimation thermal printer (hereinafter, simply referred to as a printer). FIG. 2 is a schematic diagram showing the internal configuration of the printer of FIG. 3 to 5 are schematic views showing a schematic configuration of the head unit.

<Schematic configuration of print section>
As shown in FIG. 1, the thermal printer 1 according to the present embodiment includes an operation unit 10, a control device 20, and a printing unit 30. The operation unit 10 is for an operator to operate the printer 1 and has a display 11 for displaying various information about the printer 1 and notifying the operator. The operation unit 10 of the present embodiment employs a touch panel method, and an operator can perform an operation on the printer 1 by touching an operation screen displayed on the display 11.

  The control device 20 receives input from the operation unit 10 and controls various operations in the printer 1. The control device 20 has a data input unit 20a for acquiring print data from a storage medium such as a card slot or a disk drive. Examples of the storage medium include a CD-ROM and a memory card.

  As shown in FIG. 2, the print unit 30 includes a paper storage unit 40 (the medium storage unit) that stores a long paper (corresponding to the image forming medium) wound in a roll shape in a housing 30 a. And a paper take-up unit 80 that winds up the paper fed from the paper storage unit 40, and the paper is conveyed along a conveyance path between the paper storage unit 40 and the paper take-up unit 80. A transport mechanism. A cutting unit 50, an overcoat unit 60, and an image forming unit 70 are arranged along the conveyance path from the upstream side toward the downstream side. A discharge unit 95 is provided in the vicinity of the transport path between the paper storage unit 40 and the cutting unit 50.

  In the present embodiment, the expressions “upstream side” and “downstream side” are directions from the paper storage unit 40 toward the paper take-up unit 80 along the transport path (corresponding to a first direction to be described later). Concerning. In addition, “the leading edge of the paper” and “the leading edge of the image” mean the downstream end of the paper or the image, and “the trailing edge of the paper” and “the trailing edge of the image” It shall mean the upstream edge of the paper or image.

  The paper container 40 is provided with a magazine case 41 and a rotating shaft 43. The rotating shaft 43 is loaded with a wound body 45 in which a long paper is wound with the surface to be formed outside. When the paper is unwound from the wound body 45 and conveyed toward the downstream side, the rotary shaft 43 is driven to rotate counterclockwise in FIG. 2 by a motor 43a (not shown in FIG. 2). On the other hand, when winding the unwound paper around the wound body 45, the rotating shaft 43 is driven to rotate clockwise in FIG.

  The transport mechanism is arranged in order from the upstream side, the paper feed roller pair 31 that feeds the paper unwound from the wound body 45 along the transport path, and the paper transport direction arranged upstream of the cutting unit 50. Are disposed downstream of the image forming unit 70, the turn roller pair 32 that changes the pressure, the pressure roller pair 33 that conveys the paper between the cutting unit 50 and the overcoat unit 60, and the conveyance roller pair 34. And a pair of feeding rollers 35 for feeding the paper into the paper winding unit 80. In the present embodiment, the paper transport path is configured along an arc, and each of the roller pairs 31 to 35 is disposed along the arc.

  The paper feed roller pair 31, the transport roller pair 34, and the feed roller pair 35 are individually controlled by a transport control unit 27a described later. As a result, the paper fed out from the paper storage unit 40 can be transported toward the downstream side and taken up by the paper take-up unit 80, and the paper once taken up in the paper take-up unit 80 is again The paper can be unwound and fed back upstream.

  Further, the conveying roller pair 34 is configured such that the rotation number (pulse number) can be detected by the encoder 36. As will be described later, the conveyance roller pair 34 can take a state of being driven and rotated by a motor 34a to convey the paper and a state of being driven and rotated along with the paper conveyed by the feed roller pair 35. The encoder 36 can detect the number of rotations of the transport roller pair 34 even when the transport roller pair 34 is in any of the above states.

  The cutting part 50 is disposed between the turn roller pair 32 and the pressure roller pair 33. The cutting unit 50 includes a rolling cutter 51 disposed above the conveyance path, a fixed blade 52 disposed below the conveyance path, and a chip box 53. The rolling cutter 51 is a disk-shaped member having a blade formed over the entire circumference of the circumferential portion and having a central portion held by a shaft 51a, and transports paper while being rotated by a drive mechanism 55 (not shown in FIG. 2). It is configured to be able to reciprocate along a direction orthogonal to the path. The fixed blade 52 is a rectangular blade that is longer than the entire width of the paper transport path, and is disposed so as to be orthogonal to the paper transport path. The chip box 53 is disposed below the rolling cutter 51 and the fixed blade 52.

  In a state where the paper is arranged at the cutting position of the cutting unit 50, when the rolling cutter 51 is rotated and moved along the width direction of the paper, the paper is cut by the interaction between the rolling cutter 51 and the fixed blade 52. Can do. At this time, chips generated by the cutting are dropped and stored in the chip box. In the present embodiment, as will be described later, the cutting unit 50 cuts the paper at the leading end and the trailing end of each image.

  In the vicinity of the upstream side of the cutting unit 50, an image detection sensor 90 capable of detecting the end of the image formed on the paper (mainly the rear end of the image) is provided. Further, a paper detection sensor 91 capable of detecting the end of the paper is provided in the vicinity of the upstream side of the overcoat unit 60. In the present embodiment, the upstream end portion of the overcoat portion 60 and the detection position by the paper detection sensor 91 substantially coincide with each other.

  The overcoat unit 60 is disposed on the downstream side of the conveyance roller pair 34 and has one head unit 61. The head unit 61 has a function of performing a colorless and transparent overcoat (OC) on the surface of the paper on which the image is formed. Thereby, while improving the light resistance of the formed image, the paper surface can be protected. Further, by selecting the material of the overcoat, the gloss of the print can be improved and a high-quality print can be provided.

  The image forming unit 70 includes three head units 71 to 73 (corresponding to the head unit), and in order from the upstream side, a head unit 71 that forms an image corresponding to cyan (C), magenta ( A head portion 72 for forming an image corresponding to M) and a head portion 73 for forming an image corresponding to yellow (Y) are arranged.

  In the printer 1 of the present embodiment, when the paper is transported from the paper storage unit 40 toward the downstream side, overcoat and image formation are not performed, and the paper is transported from the image forming unit 70 toward the upstream side from the downstream side. On the other hand, image formation in the image forming unit 70 and overcoat in the overcoat unit 60 are performed. Accordingly, a color image can be formed on the paper surface in the order of yellow, magenta, and cyan, and overcoating can be performed on the paper surface on which the color image is formed.

  In the present embodiment, the overcoat unit 60 and the image forming unit 70 are disposed between the transport roller pair 34 and the feed roller pair 35 along the transport path. And between each head part 61 and 71-73, a pair of guide plate 75 is each arrange | positioned. Each of the pair of guide plates 75 includes two plate-like members facing each other with an interval of about several millimeters, and is conveyed between the head portions 61 and 71 to 73 across the paper conveyance path. Paper (mainly the leading edge of the paper).

  Next, a schematic configuration of the head units 61 and 71 to 73 will be described. However, since all the head parts have the same configuration, the head part 73 will be described as a representative. As shown in FIG. 3, the head unit 73 includes a thermal head 73a (corresponding to the image forming head) having a large number of heating elements arranged in a line in the width direction of the conveyed paper, and the thermal head 73a. Platen roller 73b facing the leading end of the paper (the portion near the paper transport path where the heating element is disposed), a tape-like ribbon 73c having an ink area to which ink corresponding to yellow is attached, and unused A ribbon supply roller 73d around which the ribbon 73c is wound and a ribbon winding roller 73e that winds up the used ribbon 73c are provided.

  Further, an elevating mechanism 73f for moving the thermal head 73a up and down is provided above the thermal head 73a. The elevating mechanism 73f includes a shaft 74a having a circular cross section that is fixed to the thermal head 73a and extends in the width direction, a fixed shaft 74b that is fixed to a predetermined height and connected to the shaft 74a via a spring 76, and a shaft 74a. And a cam member 78 that is arranged between the fixed shaft 74 b and is rotatable about a shaft 77.

  Since the elevating mechanism 73f is provided in the head portion 73, the thermal head 73a is pulled upward by the urging force of the spring 76 and separated from the platen roller 73b as shown in FIG. obtain. On the other hand, when the cam member 78 rotates clockwise in FIG. 3 about the shaft 77, the cam member 78 pushes down the shaft 74a against the urging force of the spring 76, as shown in FIG. Accordingly, the thermal head 73a pushed down can be brought into pressure contact with the platen roller 73b. That is, the thermal head 73a can move forward and backward with respect to the paper transport path, and can be pressed against the paper that is transported along the transport path by pressing the ribbon 73c to form an image. It is configured to be displaceable between the retracted position.

  The thermal head 73a shown in FIG. 3 is provided with a guide portion 79a capable of guiding the paper to be conveyed along the conveyance path in the vicinity of the upstream side of the thermal head 73a. As shown in FIG. 4, the guide portion 79a of the present embodiment is configured by a rod-like or plate-like member configured to be able to contact over the entire width of the paper. When the thermal head 73a is at the retracted position, the guide portion 79a is disposed at a height that is reasonably close to the paper transport path, and the leading end of the paper transported from the upstream side deviates from the transport path. In addition, it is configured to be able to contact the paper and guide the paper along the transport path. Thereby, it can prevent that the front-end | tip part of paper jams in the clearance gap between the thermal head 73a and the guide plate 75. FIG.

  Of the pair of guide plates 75, a guide plate 75a disposed so as to face the paper forming surface is provided with a guide roller 79b protruding from the guide plate 75a to the paper side. The guide roller 79b of the present embodiment is configured by a driven roller that can contact the paper in the width direction. As a result, even when the paper with curled wrinkles (curl wrinkles) is conveyed between the pair of guide plates 75, the paper forming surface of the paper can be pressed while the guide roller 79b rotates. Can be prevented from being damaged. The guide roller 79b is provided in the vicinity of the upstream side of the thermal head 73a (in the vicinity of the downstream end of the guide plate 75a), and guides the paper effectively along the transport path in the vicinity of the upstream side of the thermal head 73a. Can do.

  3 and 4 show an example in which the guide portion is provided on the thermal head 73a. However, the present invention is not limited to this example. For example, the guide portion 79c shown in FIG. 5 is fixed to the fixed shaft 74b. It may be done. Thus, even when the thermal head 73a is displaced between the image forming position and the retracted position by providing the guide portion 79c in the portion of the head portion 73 that is not displaced by the displacement of the thermal head 73a, the guide is provided. The portion 79c is not displaced. Therefore, the paper can be smoothly conveyed along the conveyance path without excessively pressing the paper by the guide portion 79c or preventing the conveyance.

  When the paper is transported between the thermal head 73a and the platen roller 73b in a state where the thermal head 73a is disposed at the image forming position, the head unit 73 uses the ink of the ribbon 73c heated by the thermal head 73a. A color image corresponding to yellow can be formed on the surface of the paper to be formed. When the paper is transported between the thermal head 73a and the platen roller 73b, the ribbon 73c is also fed from the ribbon supply roller 73d toward the ribbon take-up roller 73e as the paper is transported.

  The head unit 61 and the head units 71 and 72 have the same configuration as the head unit 73, respectively. However, instead of the tape-like ribbon 73c having an ink area to which ink corresponding to yellow is attached, the tape-like ribbon having ink areas to which ink corresponding to colorless and transparent, cyan and magenta are attached respectively. 61c, 71c, 72c are used.

  A storage case 81 included in the paper take-up unit 80 has a substantially cylindrical shape, and a part thereof is opened as a paper insertion opening 82. Here, the feed roller pair 35 is disposed in the vicinity of the upper side of the storage case 81, and the paper conveyed by the feed roller pair 35 is inserted into the storage case 81 from the insertion port 82. The inserted paper comes into contact with the inner peripheral surface of the storage case 81 and is guided by four winding rollers 83 that are rotatably provided, and is wound so that the surface to be formed is on the outer peripheral side according to the curl. .

  The discharge unit 95 has a function of discharging the paper cut by the cutting unit 50 after image formation and overcoat are performed. The paper cut after image formation is stored in a box 96 which is a box-like member having an upper end opened. The lower end portion of the box 96 is rotatably supported by a support shaft 97, and the stored paper is taken out by pulling out the upper end portion of the box 96 from the front surface (right side in FIG. 2) of the housing 30a. Can do.

<Control block configuration>
FIG. 6 is a block configuration diagram showing a control block configuration of the printer according to the present embodiment. The control device 20 includes a motor 43a that drives the rotating shaft 43 of the paper storage unit 40, motors 31a, 34a, and 35a that respectively drive the paper feed roller pair 31, the transport roller pair 34, and the feed roller pair 35, and the transport roller. Encoder 36 that detects the number of rotations of pair 34, drive mechanism 55 of rolling cutter 51 of cutting part 50, and elevating mechanisms 61f and 71f to 73f of thermal heads 61a and 71a to 73a of head parts 61 and 71 to 73a. And the drivers 61g and 71g-73g, the image detection sensor 90, the paper detection sensor 91, and the operation part 10 are each connected.

  Here, the control device 20 includes a CPU, ROM, RAM, and the like controlled by software. The maximum winding amount storage unit 21 sets the maximum winding length of paper that can be transported downstream from the image forming unit 70 when the paper is transported from the paper storage unit 40 toward the paper winding unit 80. It is memorized as the amount taken. This maximum winding amount is calculated by adding the length of the conveyance path between the head unit 73 and the insertion port 82 of the paper winding unit 80 and the length of the paper that can be wound around the paper winding unit 80. Is done. This maximum winding amount is input by the operator.

  The print information storage unit 22 stores various setting values for forming a color image. Here, the set values include the print length of one frame for each print type (the length in the transport direction), the number of prints (the number of frames), the length of the margin formed between adjacent images, and the head heat dissipation. Includes additional length. As the print length of one frame for each print type, for example, a plurality of values are stored for each of a plurality of print types such as a standard size and a panorama size. As the number of prints, a value input for each order by the operator before the start of printing is stored. In addition, values set in advance at the stage of device configuration are stored as the length of the margin between images and the additional length for heat radiation of the head.

  The necessary winding amount calculation unit 23 calculates the length of paper necessary for forming all of a plurality of color images included in one order as the necessary winding amount. That is, in order to form all of a plurality of color images included in one order, before forming a color image by the image forming unit 70, paper having a length capable of printing these color images is used. It is necessary to convey it downstream. Therefore, when the paper is transported from the paper storage unit 40 toward the paper take-up unit 80, it exceeds the head unit 73 of the image forming unit 70 in order to print all of a plurality of color images included in one order. Thus, the length of the paper to be conveyed is calculated as the required winding amount.

  The comparison unit 24 compares the required winding amount calculated by the required winding amount calculation unit 23 with the maximum winding amount stored in the maximum winding amount storage unit 21. Then, the comparison unit 24 obtains a comparison result regarding the magnitude relationship between the necessary winding amount and the maximum winding amount.

  The winding amount determination unit 25 determines the winding amount based on the comparison result by the comparison unit 24. That is, when the comparison unit 24 obtains a comparison result indicating that the required winding amount is equal to or less than the maximum winding amount, the winding amount determination unit 25 determines the actual winding amount as the necessary winding amount. On the other hand, if the comparison unit 24 obtains a comparison result indicating that the required winding amount is longer than the maximum winding amount, the actual winding amount is determined as the maximum winding amount.

  The conveyance amount detection unit 26 detects the conveyance amount of the paper based on the number of rotations of the conveyance roller pair 34 detected by the encoder 36 after the leading end portion of the paper is detected by the paper detection sensor 91. That is, the transport amount detection unit 26 detects the length of the paper transported downstream from the detection position by the paper detection sensor 91. Thereby, the length of the paper conveyed downstream from the image forming unit 70 can be detected. Here, after the leading edge of the paper reaches the feed roller pair 35, the paper is transported by the transport force by the feed roller pair 35 instead of the transport force by the transport roller pair 34. The carry amount detection unit 26 always detects the carry amount of the paper based on the number of rotations of the carry roller pair 34.

  The transport amount detection unit 26 can detect the transport amount of paper not only when the paper is transported toward the downstream side but also when the paper is transported toward the upstream side. Therefore, when the conveyance direction of the paper is changed from the first direction toward the downstream side to the second direction toward the upstream side, from the conveyance amount in the first direction before the conveyance direction is changed, By subtracting the transport amount in the second direction after the transport direction has been changed, the position of the leading end of the paper can be detected.

  The conveyance control unit 27a (corresponding to the conveyance control unit) controls the motors 43a, 31a, 34a, and 35a, thereby causing the paper to move in the first direction from the paper storage unit 40 to the paper winding unit 80. After the transport, the transport mechanism is controlled so that the paper is transported in the second direction from the paper take-up unit 80 toward the paper storage unit 40. The image formation control unit 27b (corresponding to the image formation control unit) controls the raising / lowering timing and image formation timing of the thermal head 61a of the overcoat unit 60 and the thermal heads 71a to 73a of the image forming unit 70. That is, when the paper is transported in the first direction, the thermal heads 61a, 71a to 73a are arranged at the retracted position, while when the paper is transported in the second direction, the thermal heads 61a, 71a to 73a are imaged. An image is formed on the transported paper by placing it at the forming position. The cutting control unit 27 c controls the cutting timing at the cutting unit 50.

<Image formation procedure>
Next, an operation procedure when an image is formed in the printer 1 will be described with reference to a flowchart shown in FIG.

  First, the rotation shaft 43 in the paper storage unit 40 is rotationally driven, whereby the leading end of the paper is pulled out by the conveying force of the paper feed roller pair 31 (# 01). When the leading end of the drawn paper passes through the transport roller pair 34, the leading end of the paper is detected by the paper detection sensor 91 (# 02), and a signal to that effect is transmitted to the control device 20. Then, when the leading edge of the paper reaches the paper detection sensor 91, the paper conveyance is stopped and a standby state is entered (# 03). At this time, if each of the thermal heads 61a, 71a to 73a is disposed at the image forming position, all of them are moved to the retracted position (# 04).

  When an order is received from the operator (# 05) and the color image print type and the number of prints included in one order are input, the print information storage unit 22 prepares to start transporting the paper. Based on the stored information, the necessary winding amount corresponding to the one order is calculated by the necessary winding amount calculation unit 23 (# 06). Then, the required winding amount is compared with the maximum winding amount stored in the maximum winding amount storage unit 21 by the comparison unit 24 (# 07). Based on the comparison result, the actual winding amount is determined by the winding amount determination unit 25 (# 08). After the preparation is completed, the paper is conveyed in the first direction toward the downstream side by the conveying force of the conveying roller pair 34 (# 09).

  At this time, as described above, the thermal heads 61a and 71a to 73a are disposed at the retracted positions separated from the transport path, and therefore the paper transported by the transport roller pair 34 is the overcoat unit 60 and the image forming unit 70. Can pass smoothly. In addition, the guide portion 79a and the guide roller 79b are provided near the upstream side of the thermal heads 61a and 71a to 73a, so that the paper is guided along the transport path and is prevented from being clogged at the tip portion. can do.

  When the leading end of the paper reaches the feed roller pair 35, the leading end is sandwiched between the feed roller pair 35, and thereafter, the paper is transported mainly by the transport force of the feed roller pair 35 (# 10). The paper conveyed by the pair of feed rollers 35 is sequentially fed from the leading end portion into the storage case 81 of the paper take-up unit 80 (# 11). The paper is wound around the paper take-up unit 80 according to the winding hook while the leading end of the paper is guided by the inner peripheral surface of the storage case 81 and the take-up roller 83. When the leading edge of the paper reaches the feed roller pair 35 and the main movement is switched, the transport roller pair 34 is accompanied by the paper transported by the feed roller pair 35 from a state in which the transport force is applied to the paper. It is switched to the state of driven rotation.

  When the paper having the length of the winding amount determined by the winding amount determination unit 25 is conveyed to the downstream side from the position where image formation is performed by the head unit 73, the winding of the paper is finished (#). 12). That is, in the transport amount detection unit 26, the paper transport amount detected based on the rotation speed of the transport roller pair 34 detected by the encoder 36 after the paper detection sensor 91 detects the leading end of the paper is the winding amount. When the winding amount determined by the amount determination unit 25 and the length of the conveyance path in the overcoat unit 60 and the image forming unit 70 are added, the conveyance control unit 27a takes up the paper. And the conveyance of the paper in the first direction is stopped. At this time, the end of the image to be formed first is arranged at the position where the image is formed by the head unit 73.

  Next, each of the thermal heads 61a, 71a to 73a is moved from the retracted position to the image forming position (# 13). Thereafter, the paper is conveyed in the second direction toward the upstream side with the conveyance force by the conveyance roller pair 34 as a main drive (# 14). Accordingly, the conveying roller pair 34 that has been in the driven rotation state is rotationally driven so as to convey the paper in the second direction, and the feeding roller pair 35 is switched so as to be driven to rotate. Further, the rotation shaft 43 of the paper container 40 is rotationally driven in a direction in which the paper is rewound into the magazine case 41.

  Then, image formation corresponding to yellow is performed by the head unit 73 by the head unit 72 so that a color image included in one order is formed on the surface on which the paper is conveyed toward the second direction. Image formation corresponding to magenta is sequentially performed by the head unit 71 corresponding to cyan. A color image is completed by overlapping the images of the respective colors in this order (# 15). Subsequently, overcoating is performed on the surface of the paper on which the color image is formed by the head unit 61 (# 16).

  Here, as shown in FIG. 8, the plurality of color images included in one order are intermittently formed such that a margin portion W having a predetermined width is formed between the images. That is, in the paper, regions X corresponding to the additional length for heat dissipation of the head are arranged in the vicinity of the front end portion of the paper, and the images G and the blank portions W are alternately arranged. In the image forming unit 70, when there is an image region at the same timing at a position facing at least two of the three head units 71 to 73, an image is simultaneously formed by these head units. The overcoat by the head unit 61 is performed in parallel with the image formation by the head units 71 to 73.

  In FIG. 8, images are formed in order from the right side of FIG. 8, but when the rear end of the rightmost color image (the right end in FIG. 8) reaches the cutting position by the cutting unit 50, The end vicinity CU1 is cut (# 17). The timing at which the rear end of the image reaches the cutting position by the cutting unit 50 is detected based on the carry amount detected by the carry amount detection unit 26. After the paper is cut in this way, the paper upstream of the first formed color image (the image on the rightmost side in FIG. 8) is rewound into the paper storage unit 40.

  The paper is subsequently conveyed in the second direction, and when the leading end of the image (left end in FIG. 8) reaches the detection position by the image detection sensor 90, the image detection sensor 90 sends the image to the control device 20. A signal indicating that the tip has been detected is transmitted (# 18). The conveyance amount detection unit 26 detects the vicinity of the front end CU2 of the color image based on the number of rotations of the conveyance roller pair 34 detected by the encoder 36 after the image detection sensor 90 detects the front end of the image. Detects that the cutting position has been reached. At this time, the conveyance of the paper is stopped and the paper is cut at the leading end of the color image (# 19). Note that the positions CU1 and CU2 at which the paper is actually cut are set slightly inside the rear end or the front end of the image. Thereby, it is possible to prevent the blank portion W from being included in the print.

  Each time the paper is cut at the leading edge of the color image, it is determined whether the color image is the final image formed closest to the leading edge of the paper (# 20). If it is determined that the image is not the final image, the paper is conveyed again in the second direction. Then, after the paper is cut at the leading end of the color image, the carry amount detector 26 detects the color cut in step # 19 based on the number of rotations of the carry roller pair 34 detected by the encoder 36. It is detected that the rear end of the next color image adjacent to the image has reached the cutting position by the cutting unit 50. At this time, the conveyance of the paper is stopped and the paper is cut at the rear end of the color image (# 21). Then, it returns to step # 18 and the process similar to the above is repeated.

  On the other hand, if it is determined that the image is the final image, it is determined whether or not the formation of all color images included in one order has been completed (# 22). Here, if it is determined that the formation of all color images included in one order has not been completed, the process returns to step # 06 and the same processing as described above is repeated. On the other hand, if it is determined that all the color images included in one order have been formed, the process ends.

  Note that when it is determined in step # 22 that formation of all color images included in one order has not been completed, for example, the comparison unit 24 determines that the necessary winding amount is longer than the maximum winding amount. Thus, the winding amount determination unit 25 determines the maximum winding amount as the final winding amount. That is, in this case, the remaining color images that could not be formed to the maximum winding amount among the color images included in one order are subsequently formed. In this way, the same processing as described above is repeated until the formation of all the color images included in one order is completed.

<Another embodiment>
(1) In the above-described embodiment, an example of a thermal sublimation printer that evaporates the ink attached to the ribbon and transfers it to paper has been described, but the present invention is not limited to this. For example, it may be a thermal transfer printer that melts the ink adhering to the ribbon and transfers it to paper, or a thermal recording printer that uses thermal paper provided with a coloring layer.

  (2) In the above-described embodiment, an example of a printer in which the paper conveyance path is configured along an arc is shown, but the present invention is not limited to this. For example, the paper conveyance path may be horizontal or linearly inclined.

  (3) In the above-described embodiment, a one-pass three-head printer that forms a color image by passing paper through the three thermal heads arranged at the image forming position once (conveyed in the second direction). Although an example is shown, the present invention is not limited to this. For example, a thermal printer may be a three-pass one-head printer that forms a color image by passing paper three times through one thermal head arranged at an image forming position. Therefore, it is not always necessary to arrange a plurality of thermal heads in the image forming unit, and only one thermal head may be arranged.

  (4) Specific configurations such as a transport mechanism or transport method for transporting paper and an image forming area setting method for paper are not limited to those shown in the present embodiment. For example, when determining the actual winding amount of paper, the maximum winding amount may always be set as the actual winding amount without comparing the required winding amount and the maximum winding amount. Alternatively, the paper on which the image is formed may not have a region corresponding to the additional length for heat dissipation of the head or a blank portion between the images.

  (5) In the above-described embodiment, an example in which overcoating is performed on the formation surface of the paper on which the color image is formed by the head unit provided with the ribbon having the ink region to which the colorless and transparent ink is attached has been described. The configuration for performing the overcoat is not limited to this. For example, in the overcoat portion, a laminate layer may be formed on the surface of the paper on which the image is formed.

External perspective view of a printer according to this embodiment Schematic diagram showing the internal configuration of the printer according to the present embodiment Schematic diagram showing the schematic configuration of the head Schematic top view of thermal head The schematic diagram which shows schematic structure of the head part which concerns on another form of this invention. Block configuration diagram showing a control block configuration of the printer according to the present embodiment Flow chart showing operation procedure when forming an image Diagram showing the cutting position of paper Schematic diagram showing the schematic configuration of an image forming unit of a conventional printer

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Printer 27a Conveyance control part 27b Image formation control part 30 Printing part 31 Feed roller pair 34 Conveyance roller pair 35 Feeding roller pair 36 Encoder 40 Paper storage part 50 Cutting part 60 Overcoat part 61 Head part 61a Thermal head 70 Image formation part 71-73 Heads 71a-73a Thermal head 73b Platen roller 73c Ribbon 73d Ribbon supply roller 73e Ribbon take-up roller 73f Lifting mechanism 74a Shaft 74b Fixed shaft 75 Guide plate 75a Guide plate 76 facing the paper forming surface Spring 77 Shaft 78 Cam member 79a Guide part 79b Guide roller 79c Guide part 80 Paper winding part 90 Image detection sensor 91 Paper detection sensor 95 Discharge part

Claims (6)

A medium accommodating portion for accommodating a long image forming medium;
A transport mechanism for transporting the image forming medium stored in the medium storage section along a transport path;
At least one head unit which is provided in the middle of the conveyance path and can form an image on an image forming medium;
An image forming position provided in the head unit and capable of forming an image by being pressed against the image forming medium conveyed by the conveying mechanism, and a retracted position not being pressed by the image forming medium conveyed by the conveying mechanism. An image forming head configured to be displaceable;
After a predetermined amount of the image forming medium pulled out from the medium container is transported in the first direction from the medium container to the head unit, the image forming medium is secondly opposite to the first direction. Transport control means for controlling the transport mechanism so as to transport in the direction of
When the image forming medium is transported in the first direction, the image forming head is disposed at the retracted position, and when the image forming medium is transported in the second direction, the image forming head is Image forming control means for controlling the head unit so that an image is formed on the image forming medium conveyed in the second direction by being arranged at the image forming position;
A guide plate disposed so as to face a surface to be formed of the image forming medium conveyed to the head unit by the conveying mechanism when the image forming medium is conveyed in the first direction;
Provided in a gap between the image forming head and the guide plate, and when the image forming head is in the retracted position, the first direction near the upstream side in the first direction of the image forming head. An image forming apparatus comprising: a guide unit capable of guiding the image forming medium conveyed to the first side along the conveyance path.   The image forming apparatus according to claim 1, wherein the guide unit is provided in the head unit and configured to be able to contact over the entire width of the image forming medium conveyed by the conveyance mechanism.   The image forming apparatus according to claim 1, wherein the guide unit is fixed to a portion of the head unit that is not displaced by the displacement of the image forming head. It protrudes to the image forming medium side of the guide plate, in the guide portion upstream of the said first direction upstream vicinity of the imaging head, which can contact with the forming surface of the imaging medium the image forming apparatus according to any one of claims 1 to 3 comprising a guide roller.   The image forming apparatus according to claim 1, wherein the conveyance path is configured along an arc.   A plurality of the head units are arranged in series along the conveyance path, and all of the image forming heads of the plurality of head units are in the retracted position when the image forming medium is conveyed in the first direction. The image forming apparatus according to claim 1, wherein the image forming apparatus is disposed in the image forming apparatus.

Images