JP2021020760A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus comprising a plurality of pairs of transfer rollers having rollers capable of stably point-contacting a recording medium.SOLUTION: An image forming apparatus comprises: a plurality of pairs of transfer rollers for transferring a recording medium. One of the pair of transfer rollers comprises: a rotating shaft; and a rotating body that rotates about the rotating shaft. The rotating body comprises a thin piece formed with a plurality of triangular teeth 67 radially arranged at a predetermined interval along an outer periphery. An inclination angle α of a side edge part 67a of each tooth 67 with respect to a tangent line T passing through a top part 67b of the tooth 67 is 70°≤α≤80°.SELECTED DRAWING: Figure 3

Description

The present invention relates to an image forming apparatus including a pair of transport rollers for transporting a recording medium.

The transport roller pair is generally provided with a drive roller that is driven by a motor or the like to rotate, and a driven roller that is pressed by the drive roller by a spring to rotate driven by a spring, and is sandwiched between the rollers by the rotation of both rollers. The recorded recording medium is transported.

A transport roller pair that conveys a recording medium on which an image is formed by an inkjet method includes a surface on which an image is formed and a roller in order to prevent ink from adhering to each roller and contamination of the recording medium by the ink adhering to the roller. It is preferable that the contact area of the ink is as small as possible.

For example, the transport roller of Patent Document 1 is adapted to form fine irregularities by adhering powder to the surface so that the convex portions are in point contact with the recording medium.

JP-A-4-223948

However, in the transport roller pair of Patent Document 1, it is difficult to uniformly process the unevenness. If the height of the unevenness is not stable, the contact state between the convex portion and the recording medium becomes unstable, and there is a risk that point contact with the recording medium does not necessarily occur.

In consideration of the above circumstances, it is an object of the present invention to provide an image forming apparatus including a transport roller pair having rollers capable of stably making point contact with a recording medium.

In order to solve the above problems, the image forming apparatus of the present invention is an image forming apparatus including a transfer roller pair for conveying a recording medium, and one of the transfer rollers of the transfer roller pair has a rotating shaft and the rotating shaft. The rotating body includes a rotating body in which a plurality of triangular teeth are formed radially at predetermined intervals along the outer circumference and passes through the top of the teeth. The inclination angle α of the side edge portion of the tooth with respect to the tangent line is 70 ° ≦ α ≦ 80 °.

In the image forming apparatus of the present invention, the top of the tooth may be characterized by having an arc shape having a radius of curvature of 0.3 mm or less.

In the image forming apparatus of the present invention, the rotating body is a pair of a thin piece having a plurality of teeth formed along the outer circumference and the thin piece sandwiched from both sides in the thickness direction of the thin piece and fixed to each other. The support plate may be characterized in that the outer diameter of the support plate substantially coincides with the outer diameter of a circle passing through the bottom between the adjacent teeth.

According to the present invention, since the inclination angle of the tooth is made as large as possible, the contact area between the tooth and the recording medium can be made as small as possible. Therefore, the amount of ink adhering to the teeth is reduced, and the diameter of the points generated on the recording medium due to the transfer of the ink adhering to the teeth can be reduced.

It is a front view which shows typically the internal structure of the image forming apparatus which concerns on one Embodiment of this invention. It is a front view which shows typically the transfer roller pair in the image forming apparatus which concerns on one Embodiment of this invention. It is a front view which shows the tooth of the individual roller in the image forming apparatus which concerns on one Embodiment of this invention. It is a table which shows the experimental result which carried out about the relationship between the dirt | dirt of an image, and the inclination angle of a tooth in the image forming apparatus which concerns on one Embodiment of this invention.

Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the accompanying drawings.

The image forming apparatus 1 will be described with reference to FIG. FIG. 1 is a front view schematically showing an internal configuration of an image forming apparatus (at the time of image forming). The front side of the paper surface in FIG. 1 is the front side (front side) of the image forming apparatus. L and R in each figure indicate the left side and the right side of the image forming apparatus 1, respectively.

The apparatus main body 3 of the image forming apparatus 1 is provided with a paper feeding unit 5, an inkjet type image forming unit 7, and a paper ejection tray 9.

The paper feed unit 5 is provided at the lower part of the apparatus main body 3, and includes a plurality of paper feed cassettes 11 for accommodating paper (an example of a recording medium), and a paper feed device 13 for feeding paper from each of the paper feed cassettes 11. , Is equipped. The recording medium is not limited to paper, but includes films, fabrics, labels, and the like.

The image forming unit 7 is provided on the upper part of the apparatus main body 3, and includes a head unit 15 and a transport unit 17. The transport unit 17 is provided with four line heads 19. The four line heads 19 are arranged in the left-right direction and connected to an ink tank (not shown) containing the corresponding ink. The transport unit 17 includes a transport belt 21 that circulates and travels. The transport belt 21 is arranged at a predetermined interval from the four line heads 19. The section between the four line heads 19 and the transport belt 21 is defined as the image forming path 23.

The output tray 9 is provided on the upper part of the right side surface of the apparatus main body 3. The apparatus main body 3 is formed with a transport path 25 in which paper is conveyed from the paper feed unit 5 through the image forming path 23 of the image forming unit 7 toward the output tray 9. The transport path 25 is provided with a plurality of transport roller pairs 27.

When an image forming job is input to the image forming apparatus 1, paper of a specified size is sent from the paper feed cassette 11 to the conveying path 25 by the feeding device 13, and is conveyed to the image forming path 23 of the image forming unit 7. To. In the image forming path 23, ink is ejected from the line head 19 according to the image forming job to form an image on the paper. The paper on which the image is formed is conveyed along the transfer path 25 by the transfer roller pair 27 and discharged to the output tray 9.

Next, the transport roller pair 27 will be described with reference to FIG. FIG. 2 is a front view showing a pair of transport rollers. The transport roller pair 27 includes a drive roller 31 and a driven roller 33.

The drive roller 31 includes a rotating shaft 41 and a rotating body 43 that rotates integrally with the rotating shaft 41. The rotating body 43 is, for example, a rubber roller. The drive rollers 31 are arranged along the width direction (front-back direction) orthogonal to the paper transport direction, and both ends of the rotation shaft 41 are rotatably supported by the frame 45 of the apparatus main body 3. The rotating shaft 41 is connected to a motor (not shown). When the rotating shaft 41 is driven by the motor, the rotating body 43 rotates together with the rotating shaft 41 in the paper transport direction.

The driven roller 33 is composed of a plurality of (7 in one example) individual rollers 51. Each individual roller 51 includes a rotating shaft 53, a rotating body 55 rotatably supported by the rotating shaft 53, and a holder 57 on which the rotating shaft 53 is supported.

The rotating body 55 of the individual roller 51 has a disk-shaped thin piece 61 and a pair of disk-shaped support plates 63. The thin section 61 has a shuriken shape (star shape), and a plurality of teeth 67 are formed radially at regular intervals along the outer circumference.

The teeth 67 of the rotating body 55 of the individual roller 51 will be described with reference to FIG. FIG. 3 is a front view showing the teeth.

The tooth 67 has a tapered isosceles triangle shape, and has a pair of linear side edge portions 67a, a convex top portion 67b between the tips of the pair of side edge portions 67a, and a side edge portion of an adjacent tooth 67. It has a concave bottom 67c between the base ends of 67a. The inclination angle α (hereinafter referred to as the inclination angle of the teeth) of the extension line L of the side edge portion 67a with respect to the tangent line T of the top portion 67b is preferably 70 ° ≦ α ≦ 80 °, and is 74 ° in one example. The top portion 67b has an arc shape, and the radius of curvature is 0.3 mm as an example. The bottom portion 67c has an arcuate shape, and the radius of curvature is larger than the radius of curvature of the top portion 67b. The slice 61 is made of metal as an example, and the thickness of the slice 61 (teeth 67) is 50 μm. The thinner the thickness, the smaller the contact area with the printed surface, which is effective. However, considering the ease of processing and the strength, the thickness is preferably 50 μm, which does not affect the resolution of the image. The outer diameter of the individual rollers 51, the pitch between the teeth 67, the height of the teeth 67, and the like are appropriately selected according to the specifications of the image forming apparatus 1.

As shown in FIG. 2, each of the pair of support plates 63 has a disk shape having a diameter shorter than the diameter of the flakes 61. Specifically, the diameter of the support plate 63 is approximately equal to the diameter of the circle passing through the bottom 67c between the adjacent teeth 67 of the flakes 61. Alternatively, it is slightly larger than the diameter of this circle. The pair of support plates 63 are arranged coaxially with the thin section 61, and the thin section 61 is sandwiched from both sides in the thickness direction and fixed to each other. When the flakes 61 are sandwiched between the pair of support plates 63 in this way, as shown in FIG. 2, only the teeth 67 of the flakes 61 project radially from the pair of support plates 63. As an example, the pair of support plates 63 are made of resin, and the thickness is selected so that the thickness of the individual rollers 51 is 3 mm.

The holder 57 is urged by an urging member (not shown) so that the teeth 67 of each rotating body 55 come into contact with the rotating body 43 of the drive roller 31 at a predetermined pressure.

The plurality of individual rollers 51 are arranged at predetermined intervals along the width direction intersecting the transport direction. Further, the plurality of individual rollers 51 are arranged so that the positions along the transport direction X are alternately displaced. By arranging in this way, it is possible to reduce the resistance when the paper enters the nip between the rollers. As shown in FIG. 2, the individual roller 51 on the back side of the paper surface is shifted to the downstream side in the transport direction X from the individual roller 51 on the front side.

In the transport roller pair 27, the driven roller 33 faces the transport path 25 on the downstream side of the image forming path 23 in the transport direction, and the driven roller 31 faces the surface on which the image is not formed. Arranged to face each other.

The paper transporting action of the transport roller pair 27 having the above configuration will be described. In the non-paper-passing state, the driven roller 33 (the top 67b of the tooth 67 of the individual roller 51) comes into contact with the rotating body 43 of the driving roller 31 at a predetermined pressure, and a nip N is formed between the two. When the paper is conveyed to the nip N, the paper is sandwiched between the rollers 31 and 33 and conveyed. At this time, the top 67b of the teeth 67 of the individual rollers 51 of the driven roller 33 comes into contact with the image forming surface of the paper.

When the top 67b of the tooth 67 comes into contact with the image forming surface, ink may adhere to the top 67b. Since the individual rollers 51 rotate as the paper is conveyed, the ink adhering to the teeth 67 is transferred to the paper in the form of continuous dots, and the paper becomes dirty.

Here, the results of an experiment conducted on the relationship between how the image is stained by the ink adhering to the top 67b and the inclination angle α of the teeth 67 will be described with reference to the table of FIG.

In the image forming apparatus 1 described above, when the inclination angles α of the teeth 67 of the individual rollers 51 are 50 °, 60 °, 65 °, 70 °, 80 °, and 85 °, how the image is stained is visually evaluated. .. The radius of curvature of the top 67b of each tooth 67 is 0.3 mm. After printing a certain number of sheets, an image is formed using the judgment sample image as a manuscript, and the formed image and the judgment sample image are visually compared to stain the image in three stages (○, △, ×). Evaluated in. As an example, when the diameter of the point where the ink is transferred from the tooth 67 to the paper is larger than 42.3 μm and the ink is continuously transferred, it is unacceptably noticeable as an image stain. Therefore, when the diameter is about 42.3 μm. Is determined to be x.

As shown in the table of FIG. 4, when the inclination angle α of the tooth 67 was 60 ° or less, it was determined to be ×, when it was 65 °, it was determined to be Δ, and when it was 70 ° and 80 °, it was determined to be 〇. At 85 °, image formation was impossible due to insufficient strength of the teeth 67.

As is clear from the experimental results, when the inclination angle of the tooth 67 is 65 ° or less, the contact area between the tooth 67 and the paper becomes wide, so that the amount of ink adhered increases and the diameter of the point transferred to the paper increases. Becomes large and causes dirt. On the other hand, since the thickness of the tooth 67 is relatively thin, about 50 μm as described above, when the inclination angle is 85 ° or more, the strength of the tooth 67 is insufficient and the tooth 67 is deformed. appear.

Further, when the tip edge of the sheet conveyed to the nip N comes into contact with the side edge portion 67a of the tooth 67 of the individual roller 51, if the inclination angle α is small, the contact area between the paper and the side edge portion 67a becomes wide, and the ink Is likely to remain on the entire tooth 67. Therefore, it is preferable that the inclination angle α is as large as possible.

As described above, according to the image forming apparatus 1 of the present invention, the inclination angle α of the tooth 67 of the individual roller 51 is 70 ° to 80 °, and the radius of curvature of the top 67b of the tooth 67 is 0.3 mm or less. Therefore, the contact area between the teeth 67 and the paper can be made as small as possible. That is, in the nip N, when the paper is sandwiched between the rotating body 43 of the driving roller 31 and the teeth 67 of the rotating body 43 of the driven roller 33, the paper is curved along the top 67b of the teeth 67 and becomes the rotating body 43. Be pressed. When the paper is curved along the top 67b, the larger the inclination angle α of the teeth 67 and the smaller the radius of curvature of the top 67b, the smaller the contact area between the teeth 67 and the paper.

In the individual roller 51 of the present embodiment, the inclination angle α of the tooth 67 is made as large as possible, and the radius of curvature of the top 67b of the tooth 67 is made as small as possible, so that the contact area between the tooth 67 and the paper is made as small as possible. can do. Therefore, the amount of ink adhering to the teeth 67 is reduced, and the diameter of the points generated on the paper due to the transfer of the ink adhering to the teeth 67 can be reduced. Further, the contact area between the tip edge of the sheet conveyed to the nip N and the side edge portion 67a of the tooth 67 of the individual roller 54 can be narrowed, and ink is less likely to remain on the entire tooth 67. Therefore, it is possible to reduce the contamination of the paper due to the adhesion of ink to the teeth 67.

The radius of curvature of the top 67b of the tooth 67 is preferably as small as possible. However, if the top 67b has a sharp square shape, the top 67b may be caught on the sheet. Therefore, the top portion 67b is preferably in the shape of an arc having a radius of curvature of 0.3 mm or less in that stable machining is possible.

On the other hand, since the tooth 67 is as thin as about 50 μm, there is a problem that it is easily deformed or sufficient durability cannot be obtained. In the present embodiment, since the portion of the thin section 61 other than the teeth 67 is sandwiched between the support plates 63 from both sides in the thickness direction to reinforce the thin section 61, the strength of the individual roller 51 can be increased.

Although the present invention has been described for specific embodiments, the present invention is not limited to the above embodiments. Those skilled in the art can modify the above embodiment without departing from the scope and gist of the present invention.

1 Image forming device 25 Conveying rollers vs. 51 Individual rollers (conveying rollers)
53 Rotating shaft 55 Rotating body 61 Thin section 63 Support plate 67 teeth

Claims (3)

An image forming apparatus including a pair of transport rollers for transporting a recording medium.
One of the transport rollers of the transport roller pair is
It has a rotating shaft and a rotating body that rotates around the rotating shaft.
The rotating body includes flakes in which a plurality of triangular teeth are formed radially at predetermined intervals along the outer circumference.
An image forming apparatus characterized in that the inclination angle α of the side edge portion of the tooth with respect to the tangent line passing through the top of the tooth is 70 ° ≦ α ≦ 80 °. The image forming apparatus according to claim 1, wherein the top of the tooth has an arc shape having a radius of curvature of 0.3 mm or less. The rotating body is
It has a pair of support plates that sandwich and fix the flakes from both sides in the thickness direction of the flakes.
The image forming apparatus according to claim 1 or 2, wherein the outer diameter of the support plate substantially coincides with the outer diameter of a circle passing through the bottom between the adjacent teeth.

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