JP3758015B2 - Paper feed roller - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a paper feed roller provided in an image forming apparatus such as a printer and used for transporting paper.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, a printer is provided with a paper transport device on a paper transport path so that paper sent from a paper supply source is sent out toward a print head. This paper transport device is provided with a paper feed roller. The paper feed roller is composed of a driving roller and a driven roller. These rollers are arranged opposite to each other across the conveyance path, and a driven roller is elastically pressed against the driving roller on the fixed side via a spring means. In this way, the driven roller is rotated along with the rotation of the driving roller, and the supplied paper is conveyed while being sandwiched between the two rollers.
[0003]
In order to improve the paper conveyance accuracy, a metal roller with high outer diameter accuracy is generally used as the driving roller, and ceramic powder is attached to the surface to ensure a sufficient coefficient of friction against the paper, forming irregularities is doing. The driven roller uses rubber or elastomer on the roller surface in order to suppress the influence on the driving roller and to reduce the coefficient of friction against the paper.
[0004]
[Problems to be solved by the invention]
However, since the conventional paper feed roller uses rubber or elastomer for the driven roller, there is a problem that these materials themselves are worn quickly, and the initial paper feed accuracy cannot be maintained for a long time due to a decrease in the pressing function for the paper. In addition, when rubber is used, the friction coefficient against the paper increases, so it is necessary to inject an additive such as fluorine into the rubber to keep the friction coefficient low, which increases the cost. There's a problem.
[0005]
The present invention solves such a conventional problem, and in this type of paper feed roller, particularly by setting the friction coefficient for the paper to the driven roller as low as possible and improving the durability of the driven roller, The object is to maintain the initial sheet conveyance accuracy for a long time.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, a paper feed roller according to a first aspect of the present invention includes a drive roller and a driven roller that is arranged to face the drive roller and is elastically pressed against the drive roller, and the drive roller is made of a highly rigid material. In a paper feed roller that is formed and formed uneven by attaching ceramic powder to the surface, the paper feed roller is integrally formed of a plastic material in which the friction coefficient of the driven roller with respect to the paper is set to 0.5 or less. is there.
[0008]
The paper feed roller according to the second aspect of the present invention is characterized in that, in the first aspect, the plastic material of the driven roller is selected from polyacetal, polypropylene, polystyrene, polycarbonate, ABS resin and the like.
[0009]
From each of the above configurations, the paper sandwiched between the driving roller and the driven roller is brought into contact with the driving roller with a sufficient friction coefficient due to the unevenness of the ceramic powder, and this does not affect the paper. Since the sheet is pressed by the coefficient driven roller, the sheet can be conveyed with high accuracy. In addition, the unevenness of the drive roller due to ceramic powder is highly resistant to plastic deformation, and the plastic driven roller has high hardness and excellent durability. Can be maintained for a long time.
[0010]
Further, since the driven roller is integrally formed from a plastic material, the cost can be reduced as compared with the conventional product.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a paper feed roller, which includes a drive roller 11 and a driven roller 12.
[0012]
The drive roller 11 is formed using a metal material as a high-rigidity material, and ceramic powder 11S is attached to the surface to form irregularities. Here, the ceramic powder 11S is directly fixed by spraying a paint mainly composed of an acrylic resin mixed with ceramic powder onto the surface of the metal roller body, and then drying and fixing. In addition, the adhesion method of this ceramic powder 11S is changed variously, and the optimal adhesion state is taken. Further, as the ceramic powder 11S, here, alumina (Al ₂ O ₃ ) or silicon carbide (SiC) powder is used. The size of the ceramic powder 11S is 20 μm to 70 μm in terms of average particle diameter, and the distribution density of the ceramic powder 11S with respect to the surface area is 20% to 80%.
[0013]
The driven roller 12 is integrally formed of a plastic material. The overall shape is shown in FIG. Here, the friction coefficient of the driven roller 12 with respect to the paper S is set to 0.5 or less. Polyacetal and polypropylene are selected as the plastic material, and the following friction coefficient against paper is obtained.
In the case of polyacetal 0.44
0.48 for polypropylene
These plastic materials also have excellent properties such as excellent hardness and wear resistance, fatigue life and repeated strength. In addition, polystyrene, polycarbonate, ABS resin and the like can be used.
[0014]
FIG. 3 shows a schematic configuration of an ink jet color printer provided with the paper feed roller 1. In FIG. 3, reference numeral 20 denotes a paper supply device that supplies the paper S. The paper S is supplied between the supply roller 21, a hopper (not shown) that urges the paper S toward the supply roller 21, and the supply roller 21. And a separation pad 22 for nipping and separating the paper. A plurality of sheets S are set in the hopper, and when the sheets S are supplied, the sheets S are pressed by the hopper toward the supply roller 21 that rotates once, and separated by the separation pad 22. Only the sheet S is supplied toward the sheet conveying apparatus 10.
[0015]
Reference numeral 10 denotes a paper transport device using the paper feed roller 1. The drive roller 11 is supported on the leading end side of the lower guide 40 that forms the sheet conveyance path, and is driven to rotate by a drive mechanism (not shown).
[0016]
The driven roller 12 is rotatably supported at the tip of the upper guide 50. As shown in FIG. 4, the upper guide 50 is generally formed in a plate shape, and shaft insertion portions 51 are formed in a reverse U-shaped groove on both sides of the tip portion, and further project in the center of the tip portion. A piece 52 is formed. The driven roller 12 forms a pair of driven rollers 12 and 12 that are mounted on a single shaft 60 symmetrically and spaced apart from each other with respect to the central portion 60c in the axial direction of the shaft 60. Both ends 60b and 60b of the shaft 60 are supported by the shaft insertion portions 51 of the upper guide 50 so as to be movable only in the direction of the driving roller 11, and the central portion 60c of the shaft 60 abuts against the protruding piece 52 of the upper guide 50. Is done. A support shaft 70 is attached to the base end portion 53 of the upper guide 50. As shown in FIG. 5, the support shaft 70 is sandwiched from above and below by hook portions 82 and 83 that are bent at the lower end of the main frame 81 inside the printer, and is arranged parallel to the axial direction of the drive roller 11. A torsion spring 90 is attached to the support shaft 70. As shown in FIG. 3, one end 91 is hooked to the hook portion 84 of the main frame 81, and the other end 92 is brought into contact with the protruding piece 53 of the upper guide 50 as shown in FIG. The driven roller 12 is pressed against the driving roller 11 by the force.
[0017]
In this way, the shaft 60 is swingably mounted independently of the support shaft 70, and the driven roller pair 12, 12 is pressed against the drive roller 11 along the drive roller 11.
[0018]
Since the shaft insertion portions 51 and 51 for supporting both ends 60b and 60b of the shaft 60 of the upper guide 50 are provided at an equal distance from the support shaft 70, the shaft 60 and the support shaft 70 are parallel to each other. Since the support shaft 70 is pressed against the back surface of the main frame 81 by the torsion spring 90, the parallelism between the support shaft 70 and the driving roller 11 is maintained with high accuracy. The parallelism between the shaft 60 and the axis of the drive roller 11 is maintained with high accuracy. In particular, since the shaft 60 of the driven roller 12 can swing around the central portion 60c independently of the support shaft 70, the parallelism is maintained with extremely high accuracy. In this way, the driven roller 12 is disposed opposite to the drive roller 11 and is uniformly pressed against it.
[0019]
In FIG. 3, reference numeral 30 denotes a print head that forms an image by ejecting ink onto the surface of the conveyed paper S, and is attached to a carriage 32 on which an ink tank 31 is mounted. The carriage 32 is arranged to be movable in a direction perpendicular to the paper surface by the upper end of the main frame 81 and the carriage guide shaft 33.
[0020]
Reference numeral 37 denotes a discharge roller pair for discharging printed paper, and includes a drive roller 38 and a driven star wheel 39 biased toward the drive roller 38.
[0021]
With this structure, when the paper S supplied from the paper supply device 20 is guided toward the paper transport device 10 by the lower guide 40 and the upper guide 50, the paper S is fed by a predetermined pitch by the paper transport device 10. It is sent out toward the print head 30. The carriage 32 is moved in a direction orthogonal to the paper surface, ink is ejected from the print head 30 and one line is printed. Each time printing for one line is completed, the paper S is fed at a predetermined pitch by the paper transport device 10. These operations are repeated. When printing on the sheet S is completed, the sheet S is discharged out of the printer by the discharge roller pair 37.
[0022]
In the paper feed roller 1, the driving roller 10 is formed of a metal material, and ceramic powder 11S is attached to the surface thereof to form irregularities, and the driven roller 12 is slippery such as polyacetal (coefficient of friction with respect to the paper of 0. 1). Since the sheet S sandwiched between the driving roller 11 and the driven roller 12 is formed of a plastic material (5 or less), the lower surface side of the sheet S has a sufficient friction coefficient due to the unevenness of the ceramic powder 11S on the driving roller 11. Is secured and contacted (bite), and is pressed by the driven roller 12 having a low coefficient of friction that does not affect the sheet S from the upper surface side of the sheet S, so that the sheet S can be conveyed with high accuracy. Further, the unevenness due to the ceramic powder 11S of the driving roller 11 is not easily subjected to plastic deformation, so that it is excellent in durability, and the plastic driven roller 12 is high in hardness and excellent in durability. Performance can be maintained for a long time. Furthermore, since the driven roller 12 is integrally formed of polyacetal or the like with good workability, the cost can be greatly reduced as compared with the conventional case where the rigid roller body is covered with rubber or elastomer injected with fluorine. .
[0023]
【The invention's effect】
As described above, according to the paper feed roller of the present invention, the friction coefficient (0) with respect to the paper is low with respect to the drive roller in which the ceramic powder is attached to the surface of the roller body made of a highly rigid material to form irregularities. .5 or less), a driven roller made of a plastic material is pressed into contact, and the drive roller is in contact with the paper while ensuring a sufficient friction coefficient due to the unevenness, and this does not affect the paper. Therefore, the sheet can be conveyed with high accuracy. In addition, the unevenness caused by ceramic powder on the drive roller is less susceptible to plastic deformation, so it is superior in durability, and the plastic driven roller has high hardness and durability, so the initial conveyance accuracy and conveyance performance are extended. Can be maintained. Furthermore, since the driven roller is integrally formed from a plastic material, the cost can be reduced as compared with the conventional product.
[Brief description of the drawings]
FIG. 1 is a schematic side sectional view of a paper feed roller according to an embodiment of the present invention.
FIG. 2 is a side view showing a molded product of a driven roller of the paper feed roller.
FIG. 3 is a partial side view showing the inside of an ink-jet color printer provided with the paper feed roller.
FIG. 4 is a perspective view showing a mounting structure of the paper feed roller in a color printer.
FIG. 5 is a partially enlarged side view showing the inside of an ink-jet color printer provided with the paper feed roller.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Paper feed roller 11 Drive roller 11S Ceramic powder 12 Driven roller 10 Paper conveyance apparatus 20 Paper supply apparatus 21 Supply roller 22 Separation pad 30 Print head 31 Ink tank 32 Carriage 33 Carriage guide shaft 37 Discharge roller pair 38 Drive roller 39 Driven star wheel 40 Lower guide 50 Upper guide 51 Shaft insertion portion 52 Projection piece 53 Base end portion 60 Shaft 60b One end 60c Axial center portion 70 Support shaft 81 Main frame 82, 83, 84 Hook portion 90 Torsion spring 91 One end 92 Other end

Claims (2)

  A paper feed roller having a driving roller and a driven roller that is disposed opposite to the driving roller and is elastically pressed against the driving roller. A paper feed roller, wherein the driven roller is integrally formed of a plastic material having a friction coefficient of 0.5 or less.   The paper feed roller according to claim 1, wherein the plastic material of the driven roller is selected from polyacetal, polypropylene, polystyrene, polycarbonate, ABS resin, and the like.

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