JPH0723553U - Paper transport mechanism for color printer - Google Patents

Abstract

(57) [Summary] [Purpose] To prevent "slippage" when printing paper is rewound and to prevent deterioration of print quality. [Configuration] Conveyance rollers 9 and 4 mainly perform the conveyance of printing paper 2 in the f direction, while performing the conveyance in the b direction, respectively. Transport roller 4
For the printing paper 2 conveyed from the f direction,
While being wound and conveyed at a predetermined winding angle, the printing paper conveyed in the b direction is wound and conveyed at an angle smaller than the predetermined winding angle.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a paper transporting mechanism of a color printer for sequentially performing color printing by sequentially transferring color inks on the basis of print data corresponding to print dots.

[0002]

[Prior art]

 The configuration of a conventional color printer, in particular, the configuration of a transport mechanism that feeds printing paper will be described with reference to FIG. In this figure, reference numeral 1 is a paper cassette in which a large number of standard (for example, A4) printing papers 2 are stored. The printing paper 2 is taken out one by one by a sheet feeder (not shown), guided by the guide 3a, and supplied between the conveying roller 4 and the pinch roller 5.

Further, the printing paper 2 is wound around the conveying roller 4 at an angle of more than 90 degrees by passing between the conveying roller 4 and the pinch roller 6 under the guide of the guide 3b, and then the thermal head. The heat is transferred by the heat urging force of 7 and the pressing of the platen roller 8, and then passes between the conveying roller 9 and the pinch roller 10. Finally, the printing paper 2 is designed to be ejected in the direction opposite to the take-out direction from the paper cassette 1 in order to downsize the apparatus.

Here, a drive motor (not shown) is connected to the conveying rollers 4, 9, and when the printing paper 2 is conveyed in the direction b in the figure, the conveying rollers 4, 9 are shown in the figure. While being driven counterclockwise, when the printing paper 2 is conveyed in the direction f in the figure, the conveying roller 9 is driven clockwise in the figure. The printing paper 2 is thus conveyed from the f direction to the b direction or from the b direction to the f direction in order to perform color printing described later.

Further, the carrying roller 4 has a built-in electromagnetic clutch, and when carrying in the f direction in the drawing, its drive transmission is controlled so as to be subordinate to the carrying roller 9. Controlled by the department. For this reason, since the feeding accuracy of the printing paper 2 in the f direction is determined by the rotation accuracy of the conveying roller 9, a rubber material is used for the outer peripheral surface of the conveying roller 9 and the pinch roller is applied with an appropriate pressure. It is pressed by la and raises its friction coefficient. Further, the counterclockwise peripheral velocity of the transport roller 4 is set to be higher than that of the transport roller 9 in order to slacken the printing paper 2.

On the other hand, the thermal head 7 has a plurality of heating elements in the vertical direction in the figure, and performs thermal transfer for each color of the ink ribbon based on the supplied character data, image data and the like. This ink ribbon (not shown) is supplied between the heating element and the printing paper 2, and its surface has three colors (yellow, magenta, cyan) or four for each predetermined area. Ink of each color (black in addition to the above three colors) is applied.

Next, the operation of color printing with this configuration will be described. First, while the thermal head 7 moves in the u direction in the figure and separates from the platen roller 8, the printing paper 2 is taken out by the above-mentioned sheet feeder, and the conveying rollers 4 and 9 are rotated clockwise. , And is conveyed in the f direction until the leading end passes between the conveying roller 9 and the pinch roller 10 for a predetermined length. Next, in order to find the leading edge of the printing paper 2 and remove the slack, the transport roller 4 rotates counterclockwise, the printing paper 2 is transported in the b direction, and the leading edge of the printing paper 2 is conveyed. The part stops when the transport roller 9 and the pinch roller 10 mesh with each other. As a result, the slack of the printing paper 2 is removed. The position of the printing paper 2 is detected by a sensor (not shown).

Next, after the thermal head 7 moves in the direction d in the figure and is pressed by the platen roller 8, the conveying roller 9 is rotationally driven in the clockwise direction to convey the printing paper 2 in the f direction. On the other hand, the heating element 4a of the thermal head 7 is energized according to the print data corresponding to the print dots in synchronization with the conveyance speed of the print paper 2. As a result, one color ink (for example, yellow) is thermally transferred to the printing paper 2 to the rear end of the printing paper 2 by heat and pressing force.

Next, another color ink (for example, magenta) is superposed on the printing paper 2 for thermal transfer. Therefore, as a preparatory step, first, the thermal head is moved in the u direction, and the transport roller 4, 9 is driven to rotate counterclockwise, and the printing paper 2 is conveyed in the b direction and returned. The conveyance in the b direction is stopped when the leading end portion of the printing paper 2 meshes between the conveyance roller 9 and the pinch roller 10. At this time, the trailing edge of the printing paper 2 is returned to the vicinity of the paper cassette 1 via the transport roller 4 and the pinch rollers 6 and 5. As a result, the printing paper 2 is returned to the place where the thermal transfer of the next color ink (magenta in this case) should be started, and the slack of the printing paper 2 is removed. Then, similarly to the thermal transfer of the previous color ink (yellow), the thermal transfer of the next color ink (magenta) is performed. Finally, the same operation is performed with respect to color inks of three colors or four colors, and as a result, color printing of characters, images, etc. is performed on one sheet of printing paper 2.

As described above, the leading edge of the printing paper 2 is fed forward (f direction transportation) → the leading edge of the printing paper 2 is indexed (b direction transportation) → thermal transfer of one color ink (f direction transportation) → printing paper 2 rewinding operation (conveyance in b direction) → thermal transfer of the next color ink (conveyance in f direction) → …… → thermal transfer of the last color ink (conveyance in f direction) → discharge However, it reciprocates from the f direction to the b direction for each thermal transfer operation of one color ink.

As described above, in the thermal transfer type color printer, the color inks of three colors or four colors are sequentially transferred onto one sheet of printing paper 2 by thermal transfer, so that the printing positions of the color inks are mutually different. If they are misaligned, the color tone of the print data will be different, and in the worst case, it will be impossible to even discriminate characters. Therefore, it is required that the printing dot of each color ink has high overlay accuracy. In the above configuration, the function of transporting the print sheet 2 is assigned to the transport rollers 4 and 9, and the function of pressing the print sheet 2 against the thermal head 7 is assigned to the platen roller 8 separately. It is nothing but high precision.

[0012]

[Problems to be solved by the device]

 However, in the above configuration, the wrapping angle of the print sheet 2 around the transport roller 4 is inevitably large in order to downsize and simplify the apparatus. As described above, in the conveyance in the b direction, not only the rewinding of the printing paper 2 but also the purpose of removing the slack of the printing paper 2, the counterclockwise peripheral speed of the transportation roller 4 is It is set to be higher than that of the transport roller 9. Therefore, depending on the quality of the paper, the pulling force in the b direction by the transport roller 4 exceeds the pulling force between the transport roller 9 and the pinch roller 10, and "slip" of the printing paper 2 occurs at the transport roller 9. As a result, there is a problem in that the print dots of the respective color inks are misaligned and the print quality is degraded. It should be noted that there is no problem even if "slip" occurs when the leading edge of the printing paper 2 is cued before the thermal transfer of the first color ink (because nothing has been thermally transferred before that). ).

The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to eliminate "slip" at the time of rewinding a printing paper, thereby preventing a decrease in print quality. It is to provide a paper transport mechanism for a printer.

[0014]

[Means for Solving the Problems]

 In order to solve the above-mentioned problem, the present invention relates to a case where the printing paper is conveyed in the forward direction as the master and the subordinate respectively, and the printing paper is conveyed in the reverse direction as the subordinate and the master respectively. The first and second transport rollers are provided, and the print sheet is transported in the forward direction to print one ink, and then the print sheet is transported in the reverse direction and returned, and then transported in the forward direction again and the other In a color printer that performs color printing by printing ink, the second transport roller is wound around a print sheet that has been transported from the forward direction at a predetermined winding angle and then transported. It is characterized in that it is a conveying roller that wraps and conveys the printing paper conveyed from the opposite direction at an angle smaller than the predetermined winding angle.

[0015]

[Action]

 According to the present invention, the printing paper is wound at the predetermined wrapping angle with respect to the transport in the forward direction and the predetermined wrapping angle with respect to the transport in the reverse direction at the second transport roller. Since it is wound at an angle smaller than that, the pulling force in the opposite direction by the second transport roller can be reduced. As a result, since the printing paper is conveyed in the reverse direction in cooperation with the main second conveyance roller and the subordinate first conveyance roller, slippage of the first conveyance roller is prevented. can do.

[0016]

【Example】

 An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing this embodiment. In this figure, parts corresponding to the parts in FIG. 4 are assigned the same reference numerals and explanations thereof are omitted.

Reference numeral 20 denotes a sheet guide, the shape of which reaches the lower portion of the paper cassette 1 in an arc having a curvature larger than that of the conveying roller 4 as shown in the figure. Reference numeral 21 denotes a guide, which guides the leading end of the printing paper 2 that has passed between the transport roller 4 and the pinch roller 5 between the transport roller 4 and the pinch roller 6 in the transport in the f direction. In the conveyance in the b direction, the trailing edge of the printing paper 2 that has passed between the conveyance roller 4 and the pinch roller 6 is guided to the sheet guide 20.

Next, the operation of the embodiment having such a configuration will be described. First, while the thermal head 7 moves in the u direction in the figure and separates from the platen roller 8, the printing paper 2 is taken out by the above-mentioned sheet feeder, and the conveyance roller 9 and the electromagnetic clutch are turned on. The roller 4 and the roller 4 are driven to rotate clockwise to convey the printing paper 2 in the f direction. This conveyance is stopped when the leading end of the printing paper 2 meshes between the conveyance roller 9 and the pinch roller 10.

Then, the electromagnetic clutch of the carrying roller 4 is turned off, the thermal head 7 moves in the direction d in the figure, is pressed by the platen roller 8, and only the carrying roller 9 is rotationally driven clockwise. While the printing paper 2 is conveyed in the f direction, the heating element 4a of the thermal head 7 is urged in synchronization with the conveyance speed of the printing paper 2 according to the print data corresponding to the print dots, and the ink of the ink ribbon is removed. The heat is transferred to the rear edge of the printing paper 2. At this time, since the carrying roller 4 is the load of the carrying roller 9, that is, the carrying rollers 9 and 4 are the main and the slave, respectively, the slack of the printing paper 2 is removed by carrying in the f direction. In this way, one color ink (for example, yellow) is thermally transferred onto the printing paper 2 by heat and pressing force.

Next, since another color ink (for example, magenta) is overlaid on this printing paper 2 for thermal transfer, the thermal head 7 first moves in the u direction as a preparatory step, and the transfer roller 9 and The conveyance roller 4 with the electromagnetic clutch turned on is driven to rotate counterclockwise, and conveys the printing paper 2 in the b direction. The conveyance in the b direction is stopped when the leading end of the printing paper 2 meshes between the conveyance roller 9 and the pinch roller 10. At this time, the print sheet 2 is conveyed along the inner peripheral surface of the sheet guide 20 by the guide guide 21, and is formed at an angle larger than the winding angle of the convey roller 4 and between the convey roller 4 and the pinch roller 6. Only one set conveys in the b direction. Therefore, in removing the slack caused by the conveyance in the b direction, the pulling force by the conveyance roller 4 is reduced, so that the conveyance roller 9 and the pinch roller 10 are unlikely to slip. In addition, since the counterclockwise peripheral speed of the transport roller 4 is set to be higher than that of the transport roller 9, the transport rollers 9 and 4 are subordinate and primary in the transport in the b direction. .

Then, after the thermal head 7 moves again in the direction d in the figure and is pressed by the platen roller 8, the transport rollers 4 and 9 are rotationally driven in the clockwise direction, and the previous color ink (yellow) Similar to the thermal transfer of, the next thermal transfer of the color ink (magenta) is performed. Thus, the operation of thermal transfer of one color ink from the leading edge of the printing paper 2 (f direction conveyance) → the thermal transfer of one color ink (f direction conveyance) → rewinding of the printing paper 2 to the sheet guide 20 (b Direction transfer) → thermal transfer of the next color ink (transfer in the f direction) → …… → thermal transfer of the last color ink (transfer in the f direction) → discharge is performed for three or four color inks. As a result, color printing of characters, images, etc. is performed on one sheet of printing paper 2.

According to this embodiment, printing is performed without performing the forward feed of the leading end of the printing paper 2 (conveyance in the f direction) and the cueing of the leading end of the printing paper 2 (conveyance in the b direction) in the conventional example. Since the slack of the paper 2 can be removed, the time required for printing can be shortened as compared with the conventional color printer described above.

In the above-described embodiment, the tension suitable for transporting the print sheet 2 in the f direction is generated by the transport roller 4 having the electromagnetic clutch, but this is used as a slip clutch, that is, a rotation resistance. It may be a clutch having. In this embodiment, the color transfer printer has been described as an example of the color printer, but the present application is not limited to this. That is, as long as the printing paper reciprocates in the f direction ← → b direction, for example, an ink jet type or a dot impact type may be used.

[0024]

[Effect of device]

 According to the present invention described above, in the second transport roller, the printing paper is wound at a predetermined winding angle with respect to the transport in the forward direction, while the predetermined paper is transported with respect to the transport in the reverse direction. Since the winding is performed at an angle smaller than the winding angle, it is possible to reduce the pulling force of the second transport roller in the opposite direction. As a result, since the printing paper is conveyed in the reverse direction in cooperation with the main second conveyance roller and the subordinate first conveyance roller, slippage of the first conveyance roller is prevented. can do. Therefore, it is possible to prevent deterioration of print quality.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration of an embodiment according to the present invention.

FIG. 2 is a schematic diagram showing a paper feeding structure in a conventional thermal transfer type color printer.

[Explanation of symbols]

 1 Paper Cassette 2 Printing Paper 3a, 3b Guide Guide 4 Conveyor Rollers 5, 6, 10 Pinch Roller 7 Thermal Head 8 Platen Roller 9 Conveyor Roller (First Conveyor Roller) 20 Sheet Guide 21 Guide Guide

Claims (1)

[Scope of utility model registration request] 1. A printing paper, comprising first and second carrying rollers for mainly and subordinately carrying the printing paper in the forward direction and respectively, respectively, subordinately carrying the printing paper in the opposite direction. Is printed in the forward direction and then printed with one ink, then the printing paper is transported in the reverse direction and returned, and then again transported in the forward direction to print another ink, thereby performing color printing. In the printer, the second transport roller wraps the print sheet transported from the forward direction at a predetermined wrapping angle and transports the print sheet while transporting the print sheet transported from the reverse direction. The paper transport mechanism of the color printer is characterized in that it is a transport roller that winds and transports at an angle smaller than the predetermined winding angle.