JP2002114399A - Paper transport mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper transport mechanism capable of making a clear and high quality print on printing paper. SOLUTION: In this paper transport mechanism, printing paper 1 is clamped between a pressure roller 12 and a transport roller 13, and with the pressure roller 12 pressurized, the printing paper 11 is transported by rotary drive of the transport roller 13. In the paper transport mechanism, the pressure roller 12 and the transport roller 13 are formed as one roller structure having a length projected from both ends in the cross direction of the printing paper 11, and gripping parts 15 coming into contact with the respective end parts 11A, 11B in the cross direction of the printing paper 11 are respectively formed on both end parts 13A, 13B of the transport roller 13. The respective gripping parts 15 are formed by plural small projections projected from the outer periphery 13a of the transport roller toward the respective end parts 11A, 11B of the printing paper 11, and a valley side 16a of the small projection 16 is made substantially flush with the outer periphery 13a of the transport roller 13 without a step.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a sheet transport mechanism suitable for use in a transfer type printer or the like.

[0002]

2. Description of the Related Art As a paper transport mechanism used in a printer or the like, those shown in FIGS. 5 and 7 have been proposed.

[0005] The paper transport mechanism shown in FIG. 5 includes a pressing roller 51 and a transport roller 52, and has fine projections 53 formed on the entire outer periphery of the transport roller. The paper transport mechanism sandwiches the print paper 54 between the pressure roller 51 and the transport roller 52, and transports the print paper 54 by driving the transport roller 52 while applying a pressing force F to both shaft ends of the pressure roller 51. I do. The printing paper 54 is conveyed while being held by the minute projections 53 by the pressing force F of the pressing roller 51. In this paper transport mechanism, when the pressing force F acts on both shaft ends of the pressing roller 51, the pressing roller 51 bends and deforms in an arcuate shape as shown in FIG. The force for pressing the paper 54 or the diameter (d
1, d2, d3) are non-uniform. Therefore, the grip state of the printing paper 54 by the minute projection 53 is different between each end and the center of the transport roller 52, and the transport amount of the printing paper 54 is also different from each end and the center of the transport roller 52. And it will be different. That is, due to the bow-shaped bending deformation of the pressing roller 51, the diameter of the printing paper 54 in the width direction becomes
As the distance from each end of the conveying roller 52 toward the center increases, d1 <d2 <d3.
4 also increases from each end toward the center, 2 × d1 × π × n <2 × d2 × π × n <2 × d3 ×
π × n (n: number of rotations of the transport roller 52). If the transport amount of the printing paper 54 is different, the printing paper 54 will be deformed or misaligned, which will adversely affect printing.

In order to reduce the difference in the transport amount of the printing paper 54, the paper transport mechanism shown in FIG. 7 divides the pressing roller 51 into two parts, and is provided at each end of the printing paper 54 in the width direction.
The minute projections 53 are formed on the entire outer periphery of the transport roller 52. In this paper transport mechanism, the printing paper 54 is transported by applying a pressing force F to each of the pressure contact rollers 51 and gripping each end of the printing paper 54 in the width direction by the minute projections 53. According to this paper transport mechanism, only the respective ends of the printing paper 54 are gripped and transported by the pressing rollers 51 and the minute projections 53, and therefore, as shown in FIG. The diameters d4 and d5 can be made substantially uniform, so that the difference in the transport amount of the printing paper 54 can be reduced, and the deformation and displacement of the printing paper 11 can be eliminated.

[0005]

However, in the paper transport mechanism shown in FIG. 7, since each pressing roller 51 is pressed only at each end of the printing paper 54, as shown in FIG. A groove-shaped press contact mark 56 is formed at each end. As shown in FIG. 9, the presence of the press contact mark 56 forms a gap 58 between the print head 57 and the printing paper 54.
In the width direction, a difference is generated in the heat transfer from the print head 57. For example, in color printing, when the printing paper 54 is reciprocated with the print head 57 to transfer various inks (yellow, magenta, and cyan inks) in color printing, the printing is performed on the printing paper 54. The difference in density results in print degradation.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a printing paper that is sharp,
An object of the present invention is to provide a sheet transport mechanism that enables high-quality printing.

[0007]

According to a first aspect of the present invention, there is provided a sheet conveying mechanism for holding a printing sheet between a pressing roller and a conveying roller, and driving the conveying roller while pressing the pressing roller. Is transported. In the paper transport mechanism of the present invention, the pressing roller and the transport roller
It has a single structure with a length protruding from both ends in the width direction of the printing paper, and gripping portions are formed at both ends of the transport roller in contact with each end in the width direction of the printing paper. Each gripping portion is constituted by a number of minute projections projecting from the outer periphery of the transport roller to each end of the printing paper, and the valley side of each minute projection is made substantially coincident with the outer periphery of the transport roller. Pressing roller
With a single structure having a length protruding from both ends in the width direction of the printing paper, it is possible to eliminate a pressing contact mark generated on the printing paper due to pressure of the pressing roller. Further, when the gripping portions are formed at both ends of the transport roller, even if the pressing roller bends and deforms in an arcuate shape, only the respective ends of the printing paper remain in the same state without gripping the central portion of the printing paper. By gripping with, the difference in the transport amount of the printing paper can be reduced, and the deformation and displacement of the printing paper due to the transport can be eliminated. Further, since the valley side of the minute projection is substantially coincident with the outer periphery of the conveying roller, the minute projection can be formed without a step with respect to the outer periphery of the conveying roller. It is possible to eliminate a deformation such as an indentation mark.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A paper transport mechanism according to the present invention will be described.
This will be described with reference to FIGS. Note that an example in which the paper transport mechanism of the present invention is applied to the thermal transfer printer P shown in FIG. 1 will be described.

The thermal transfer printer P shown in FIG.
1 and convey the ink of the ink ribbon 4 to the printing paper 11
By performing thermal transfer to the printer, monochrome printing or color printing is performed. The thermal transfer printer P includes a print head 2, a platen roller 3, an ink ribbon 4, paper transport mechanisms 5, 6, and the like.

The print head 2 thermally transfers the ink of the ink ribbon 4 to the printing paper 11 by applying pulsed heat to the ink ribbon 4 according to the image signal. The print head 2 is moved so as to be able to approach and separate from the platen roller 3. The printing paper 2 and the ink ribbon 4 are pressed against the platen roller 3 by the movement of the print head 2.

[0011] The ink ribbon 4 is wound as a feeding roll R1 on the paper feeding side M, and is fed between the print head 2 and the platen roller 3 through the guide roller 7. Further, the ink ribbon 4 is fed out from the space between the print head 2 and the platen roller 3 to the paper discharge side N through the guide roller 8, and is taken up as a take-up roll R2. As the ink ribbon 4, one coated with black ink used for monochrome printing, or one coated with yellow, magenta, and cyan inks used for color printing is used.

The paper transport mechanisms 5 and 6 are arranged on the paper feed side M and the paper discharge side N on both sides of the print head 2 and the platen roller 3, respectively. Each of the paper transport mechanisms 5 and 6 includes a pressing roller 12 and a transport roller 13.
The printing paper 11 fed from the paper cassette 10 is sandwiched between the printing heads 2 and 13 and is conveyed between the printing head 2 and the platen roller 3.

Next, each roller 1 of the paper transport mechanisms 5 and 6
The specific structures 2 and 13 will be described with reference to FIGS.

The pressing roller 12 has a single roller structure having a length protruding from both ends of the printing paper 11 in the width direction H. The pressing roller 12 is configured by mounting a rubber roller 12B on the outer periphery of a roller shaft 12A.
Is a length protruding from both ends in the width direction H of the printing paper 11. The press roller 12 transports the printing paper 11 by the pressing force F applied to the roller shaft 12A.
3 (see FIG. 2).

The transport roller 13 has a single roller structure having a length protruding from both ends in the width direction H of the printing paper 11. The transport roller 13 is driven to rotate by a driving unit, and transports the printing paper 11 nipped by the pressing roller 12. The transport roller 13 is formed of a hard material that can be etched. A metal such as stainless steel is used as the hard material. Also, the transport roller 13 has 2
Two grips 15 are formed (see FIG. 2).

Each of the gripping portions 15 is provided at both ends 13 of the transport roller 13 with reference to the center a of the transport roller 13 in the axial direction.
A and 13B are formed symmetrically, and are opposed to both ends 11A and 11B in the width direction H of the printing paper 11. Each of these grips 15 is composed of a large number of minute projections 16. A large number of minute projections 16 are provided at both ends 13A, 13B of the transport roller 13.
And are formed over the outer periphery 13 a of the transport roller 13. The minute projections 16 protrude from the outer periphery of the transport roller 13 toward the respective ends 11A and 11B of the printing paper 11 by etching. In addition, minute projection 1
6, the protrusion height k is set to 30 to 100 μm (micrometer), and the valley side 16a of the minute projection 16 is made substantially coincident with the outer periphery 13a of the transport roller 13 so that the step δ = 0. [See FIG. 3]. That is, many small protrusions 1
6 is smoothly connected without the valley side 16 a having a step δ with respect to the outer periphery of the transport roller 13.
Note that each gripper 15 is provided at each end 13 of the transport roller 13.
The width h of A, 13B, the number of minute projections 16 formed, and the projection height k adjust the range of contact with each end 11A, 11B of the printing paper 11 and the gripping force due to friction with each end 11A, 11B. Is done.

The transport roller 13 presses each gripping portion 15 by pressing from the pressing roller 12 so that
1A and 11B by frictional contact with the printing paper 11 without gripping the central part of the printing paper 11 by the minute projections 16.
Of the printing paper 11 by gripping only the respective ends 11A and 11B of the printing paper 11
Is conveyed between the paper supply side M and the paper discharge side N. When the pressing roller 12 is pressed by setting the step δ between the valley side 16a of the minute projection 16 and the outer periphery 13a of the conveying roller 13 to δ = 0, the conveying roller 13 Only the ends 11A and 11B of the printing paper 11 are gripped without deformation such as partial pressing pressure.

Next, the operation of the paper transport mechanisms 5, 6 according to the present invention will be described in relation to printing by the thermal transfer printer P.

Printing by the thermal transfer printer P is started by feeding print paper 11 from the paper cassette 10 to the paper transport mechanism 5. The paper transport mechanism 5 includes the pressing roller 1
The fed printing paper 11 is pressed against the conveying roller 13 by the pressing force F applied to the second roller shaft 12A. Then, by rotating the transport roller 13, the printing paper 11 sandwiched between the pressing rollers 12 is transported from between the print head 2 and the platen roller 13 to the paper transport mechanism 6 (see FIG. 1).

At this time, the pressing roller 1 of the paper transport mechanism 5
4, as shown in FIG. 4, the pressing force F applied to the roller shaft 12 </ b> A bends and deforms in a bow shape symmetrical to both ends with respect to the center a in the axial direction of the pressing roller 12. You. Due to the bending deformation of the pressing roller 12, the printing paper 11 is pressed against the transport roller 13 by receiving substantially equal pressures at the respective ends 11A and 11B. In this state, the transport roller 13 holds the minute protrusion 16 of each gripper 15 and the printing paper 1.
Each end 11A, 1 of the printing paper 11 by frictional contact with
Only 1B is gripped, and each end 11A, 11B is gripped in an equivalent state. That is, as shown in FIG. 4, the printing paper 11 holds the holding portions 1 of the pressing roller 12 and the transport roller 13.
5 (micro projections 16), the printing paper 11 is gripped only at the ends 11A and 11B except for the center, so that the diameters d6 and d7 in the width direction of transporting the printing paper 11 are made substantially equal. You. In addition, the minute projections 16 of each grip portion 15 are
Formed only at each end 13A, 13B of the transport roller 13,
When the pressing roller 12 is pressurized by not being formed at the center portion or the like other than the end portions 13A and 13B, deformation and deviation of the printing paper 11 at the center portion of the transport roller 13 and bending deformation of the pressing roller 12 itself are performed. And reduce the printing paper 11
The diameters d6 and d7 in the width direction for transporting are substantially equal. Thereby, the transport rollers 13 of the paper transport mechanism 3
Reduces the difference in the transport amount between the ends 11A and 11B of the printing paper 11 and transports the printing paper 11 to the paper transport mechanism 6 without deformation or displacement. In addition, each gripper 15
Is formed by making the valley side 16a of the minute protrusion 16 substantially coincide with the outer periphery 13a of the transport roller 13 and eliminating the step δ. Therefore, when the pressing roller 12 is pressed, a portion Gripping without deformation such as typical pressure contact marks. Further, the rubber roller 1 of the pressing roller 12
2B is a single structure having a length protruding from each end 11A, 11B of the printing paper 11, so that the pressing roller 12
No pressure contact mark is formed on the printing paper 11 by the pressing force F acting on the printing paper 11.

Subsequently, when the printing paper 11 is transported to the paper transport mechanism 6, the paper transport mechanism 6 is pressed by the pressing force F applied to the roller shaft 12 A of the pressing roller 12.
1 is pressed against the transport roller 13. In the paper transport mechanism 6, similarly to the paper transport mechanism 5, the pressing roller 1
2 is bowed and deformed. The transport roller 13 has the same structure as the paper transport mechanism 5 due to the bending deformation of the pressing roller 12.
1 and only the ends 11A and 11B are gripped, and the ends 11A and 11B are gripped in a similar state. In addition, each gripping portion 15 grips the printing paper 11 without causing deformation such as partial pressure contact marks caused by the step δ. Further, the pressing force F applied to the pressing roller 12 does not cause a pressing mark on the printing paper 11. As a result, the printing paper 11 can be set between the printing head 2 and the platen roller 3 by sandwiching the printing paper 11 between the paper transport mechanisms 5 and 6 without causing deformation or pressure contact marks on the printing paper 11.

When the printing paper 11 is set between the printing head 2 and the platen roller 3, the printing paper 11 and the ink ribbon 4 are pressed against the platen roller 3 by moving the printing head 2 toward the platen roller 3. . In this state, the printing paper 11 is conveyed to the paper discharge side N while applying tension toward the paper discharge side N by rotating the conveyance roller 13 of the paper conveyance mechanism 6. In synchronization with this, pulse-shaped heat corresponding to the image signal is generated by the print head 2 and the ink ribbon 4.
, The ink (black ink or yellow ink) of the ink ribbon 4 is thermally transferred to the printing paper 11. At this time, as described above, the printing paper 11 does not form a pressure contact mark due to the difference in the transport amount or the pressing of the pressing roller 12, so that no gap is formed in the width direction of the printing paper 11,
It is brought into close contact with the print head 2. Thereby, the print head 2
Prints on the printing paper 11 without deformation and displacement, and transmits heat uniformly in the width direction H of the printing paper 11 without causing a difference in printing sensitivity in the width direction H of the printing paper 11. Perform clear, high quality printing.

In monochrome printing, the printing paper 11
After the completion of the thermal transfer of the black ink to the printer P, the printing paper 11 is discharged from the discharge side N to the outside of the printer P. Also in this monochrome printing, the printing paper 11 is transported to the discharge side N by reducing the difference in the transport amount between the ends 11A and 11B of the printing paper 11 by the paper transport mechanisms 5 and 6. In addition, deformation such as partial pressure contact marks of the printing paper 11 caused by the step δ does not occur. Further, no trace of the pressure contact roller 12B due to the rubber roller 12B is generated on the printing paper 11. As a result, in monochrome printing, the printing paper 11 can be transported without causing deformation, displacement, and pressure contact marks on the printing paper 11, so that clear, high-quality printing can be performed.

In the color printing, when the thermal transfer of the yellow ink to the printing paper 11 is completed, the paper transport mechanism 5
Of the printing paper 11 by rotating the transport rollers 13 of the printing paper 11.
To the paper supply side M. Then, again, the paper transport mechanism 6
Of the printing paper 11 by rotating the transport rollers 13 of the printing paper 11.
Is conveyed to the paper discharge side N, and the magenta ink of the ink ribbon 4 is superimposed on the printing paper 11 and thermally transferred by the print head 2. As described above, in the color printing, the printing paper 11 is reciprocated between the paper discharge side N and the paper feeding side M, so that the yellow, magenta,
Cyan ink is sequentially thermally transferred. When the thermal transfer of each ink to the printing paper 11 is completed, the printing paper 11
From the paper discharge side N to the outside of the printer P. In this color printing as well, the difference in the transport amount between the ends 11A and 11B of the printing paper 11 is reduced by the paper transport mechanisms 5 and 6 so that the printing paper 11 is moved between the paper discharging side N and the paper feeding side M. Can be transported. In addition, deformation such as partial pressure contact marks of the printing paper 11 caused by the step δ does not occur. Further, no trace of the pressing roller 12 due to the rubber roller 12B is formed on the printing paper 11. Thus, in color printing, the printing paper 11 can be transported without causing deformation, displacement, and pressure contact marks on the printing paper 11, so that clear and high-quality printing can be performed.

As described above, the paper transport mechanisms 5 and 6 of the present invention
The printing paper 11 can be conveyed between the print head 2 and the platen roller 3 without causing deformation, displacement, and pressure contact marks on the printing paper 11. As a result, the thermal transfer printer P
Thus, clear and high quality printing can be performed.

In the paper transport mechanisms 5 and 6 of the present invention,
The present invention is not limited to those shown in FIGS. 1 to 3 and can take the following forms, for example. (1) The pressing roller 12 can be formed of a hard material such as stainless steel, hard plastic, or ceramic. This eliminates the bending deformation of the pressing roller 12,
The contact can be made over the width direction H of the printing paper 11, eliminating the heat transfer difference of the print head 2 to the printing paper 11, and enabling clear and high quality printing. (2) As the pressing roller 12, a roller in which the surface of a rubber roller 12A is coated or the like can be adopted. (3) The transport roller 13 can be formed of a hard material such as ceramics. Then, the minute projections 15 are formed by plastic working. (4) Examples of the application of the paper transport mechanisms 5 and 6 are not limited to the thermal transfer printer P, but include a printer that prints by sublimating the ink of the ink ribbon 4 and a facsimile machine, a copier, and the like. It can be applied to various devices. (5) If the step δ between the valley side 16a of the minute projection 16 and the outer periphery 13a of the transport roller 13 is δ = 0.1 mm or less, the valley side 16a of the minute projection 16 is slightly It is also possible to adopt a configuration having a step. If the step δ is equal to or less than 0.1 mm, even if each of the end portions 11A and 11B of the printing paper 11 is gripped by the gripping portions 15, the deformation such as partial pressure contact marks of the printing paper 11 affects printing. Not because it can be minimized.

[0027]

According to the paper transport mechanism of the present invention, the pressing roller has a single structure protruding from both ends in the width direction of the printing paper, and only the respective ends of the printing paper are controlled by the pressing roller and the minute projections of each holding portion. Because it was grasped, deformation and misalignment on the printing paper,
The printing paper can be conveyed without causing a press contact mark.
Further, the minute projections of each grip portion are constituted by a large number of minute projections projecting from the outer periphery of the conveying roller, and the valley side of the minute projections substantially coincides with the outer periphery of the conveying roller, so that the minute projections are formed on the outer periphery of the conveying roller. On the other hand, when the pressing roller is pressed, deformation such as partial press contact marks on the printing paper caused by the step is not caused. As a result, the printer can perform clear, high-quality printing on printing paper.

[Brief description of the drawings]

FIG. 1 is a schematic diagram illustrating a configuration of a thermal transfer printer to which a paper transport mechanism of the present invention is applied.

FIG. 2 is a cross-sectional view taken along the lines AA and BB of FIG. 1, and is a side view showing a configuration of a sheet transport mechanism.

FIG. 3 is an enlarged view of a main part of FIG. 2;

FIG. 4 is a side view showing a state where a pressure roller in FIG. 2 is pressed.

FIG. 5 is a side view showing a conventional paper transport mechanism.

FIG. 6 is a side view showing a state in which the pressing roller in FIG. 5 is pressed.

FIG. 7 is a side view showing another conventional paper transport mechanism.

FIG. 8 is a side view showing a state in which the pressing roller in FIG. 7 is pressed.

FIG. 9 is an enlarged view showing a contact state between a printing paper and a print head in FIG. 7;

[Explanation of symbols]

 Reference Signs List 2 Print head 3 Platen roller 5 Paper transport mechanism 6 Paper transport mechanism 11 Print paper 11A, 11B End of print paper 12 Pressure contact roller 13 Transport rollers 13A, 13B End of transport roller 13a Outer circumference of transport roller 14 Ring groove 15 Gripping section 16 Minute protrusion 16a Base end of minute protrusion

Claims (1)

[Claims] 1. A paper transport mechanism for nipping print paper between a pressure roller and a transport roller and transporting the print paper by driving the transport roller while pressing the pressure roller, wherein the pressure roller and the transport Each of the rollers has a single structure having a length protruding from both ends in the width direction of the printing paper, and gripping portions contacting each end of the printing paper in the width direction at both ends of the transport roller. Forming, each gripping portion is constituted by a number of minute projections projecting from the outer periphery of the transport roller to each end of the printing paper, and the valley side of each minute projection is substantially formed on the outer periphery of the transport roller. A paper transport mechanism characterized by matching.