Image forming device

Abstract

To provide an image forming apparatus that can prevent a sheet jammed before fixation from entering an intermediate transfer unit.SOLUTION: An intermediate transfer unit 10 of an image forming apparatus includes: an intermediate transfer belt 16 that transfers toner images in a plurality of colors formed on a plurality of photoreceptor drums sequentially in an overlapping manner to form a toner image in multiple colors; a driving roller 14 that drives the intermediate transfer belt 16; and a secondary transfer roller 15 that is provided opposite to the driving roller 14. The driving roller 14 and the secondary transfer roller 15 form a nip part N, and a sheet is conveyed to the nip part N to transfer a color image to the sheet. A post-transfer PG 11 provided on the intermediate transfer belt 16, and a shield 12 provided between the post-transfer PG 11 and the intermediate transfer belt 16 are provided on a downstream side of sheet conveyance of the nip part N.SELECTED DRAWING: Figure 2A

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus. [Background technology]

[0002] A conventional image forming apparatus is disclosed, for example, in Japanese Patent Application Laid-Open No. 2013-186439 (Patent Document 1). According to Patent Document 1, a peeling claw is provided to prevent a sheet of paper adsorbed to the intermediate transfer belt from being transported downstream along with the intermediate transfer belt. FIG. 8A is a cross-sectional view of an intermediate transfer unit 101 of a conventional image forming apparatus, which differs in shape from that of Patent Document 1. FIG. 8B is a view taken along arrow 8B-8B in FIG. 8A and an enlarged view thereof. Referring to FIGS. 8A and 8B, the intermediate transfer unit 101 of the conventional image forming apparatus has a nip portion N formed by a drive roller 104 and a secondary transfer roller 105, and a sheet of paper is transported through the nip portion N in the direction indicated by the upward arrow in FIG. 8A. Downstream of the nip portion N, a peeling claw 103 is provided in the longitudinal (axial) center of the drive roller 104 to prevent the outer periphery of the drive roller 104 from pulling the sheet of paper toward the intermediate transfer belt 106. The peeling claw 103 is attached to a post-transfer PG (paper guide) 102 provided on the intermediate transfer belt 106. In Fig. 8A, the left-pointing arrow indicates the direction in which the intermediate transfer belt 106 moves. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-186439 Summary of the Invention [Problem to be solved by the invention]

[0004] The intermediate transfer unit 101 of a conventional image forming apparatus was configured as described above. In the conventional intermediate transfer unit 101, a peeling claw 103 was provided in the center of the post-transfer PG 102, which corresponds to the center in the longitudinal direction of the drive roller 104, to prevent paper from failing to peel. When paper jams before fixing, the paper strikes the peeling claw 103, which could damage the intermediate transfer belt 106. For this reason, a small-diameter drive roller 104 was adopted to prevent paper from failing to peel, and the peeling claw 103 was eliminated. However, there was a problem in that paper that jams before fixing could slip into the gap between the post-transfer PG 102 and the intermediate transfer belt 106 and enter a cleaner (not shown).

[0005] This invention has been made to solve the above-mentioned problems, and aims to provide an image forming apparatus that can prevent paper that has jammed before fixing from entering PG 102 after transfer. [Means for solving the problem]

[0006] The image forming device of this invention includes an intermediate transfer belt on which a multi-color toner image is formed by sequentially transferring and overlapping multiple color toner images formed on multiple photosensitive drums, a drive roller that drives the intermediate transfer belt, and a secondary transfer roller that is arranged opposite the drive roller, wherein a nip is formed between the drive roller and the secondary transfer roller, and a color image is transferred to the paper by transporting the paper through the nip, and further includes a post-transfer paper guide that is arranged on the intermediate transfer belt, and a paper intrusion prevention member that is arranged between the post-transfer paper guide and the intermediate transfer belt, downstream of the nip portion in the paper transport direction.

[0007] Preferably, the paper intrusion prevention member is provided at a position that covers the center of the intermediate transfer belt in the width direction.

[0008] More preferably, a gap equal to or greater than a first predetermined distance and equal to or less than a second predetermined distance is provided between the paper intrusion prevention member and the intermediate transfer belt.

[0009] The paper intrusion prevention member is preferably provided vertically above the drive roller of the intermediate transfer belt and downstream of the uppermost position of the drive roller.

[0010] The paper intrusion prevention member may have a sloped lower end. [Effects of the Invention]

[0011] According to this invention, a paper intrusion prevention member is provided between the post-transfer PG on the intermediate transfer belt and the transfer belt on the downstream side of the paper transport at the nip portion, thereby providing an image forming device that can prevent paper that has jammed before fixing from entering the post-transfer PG.

[0012] The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the preferred embodiments, which proceeds with reference to the accompanying drawings. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a perspective view of an image forming apparatus according to an embodiment of the present invention; [Figure 2A] 2 is an enlarged cross-sectional view showing an intermediate transfer unit of the image forming apparatus shown in FIG. [Figure 2B] 2B is a view taken along the arrow 2B-2B in FIG. 2A. [Figure 3] FIG. 10 is a diagram illustrating the movement of toner adhering to a shielding object. [Figure 4A] FIG. 4 is a diagram illustrating the positional relationship between a shield and an intermediate transfer belt. [Figure 4B] 4B is a cross-sectional view of the portion indicated by arrow 4B-4B in FIG. 4A. [Figure 5] FIG. 2 is a plan view of the intermediate transfer belt as viewed from above. [Figure 6] FIG. 10 is a diagram showing another embodiment of the present invention. [Figure 7A] FIG. 10 is a diagram showing still another embodiment of the present invention. [Figure 7B] 7B is a cross-sectional view of the portion indicated by arrow 7B-7B in FIG. 7A. [Figure 8A] FIG. 10 is a cross-sectional view showing an intermediate transfer unit of a conventional image forming apparatus. [Figure 8B] 8B is a view taken along the arrow 8B-8B in FIG. 8A and an enlarged view thereof. DETAILED DESCRIPTION OF THE INVENTION

[0014] An embodiment of the present invention will be described in detail below with reference to the drawings. Fig. 1 is a perspective view of an image forming apparatus 30 according to an embodiment of the present invention. First, the basic configuration of the image forming apparatus 30 will be roughly described. In this specification, the front side (indicated by "Front" in the drawing) is the side facing the user's standing position, i.e., the side on which an operation unit (not shown) is provided, and the opposite side is defined as the rear side (indicated by "Rear" in the drawing) to define the front-to-rear direction (depth direction) of the image forming apparatus 30 and its components.

[0015] 1, in this embodiment, the image forming apparatus 30 is a multifunction peripheral (MFP) having a copying function, a printer function, a scanner function, a facsimile function, etc. The image forming apparatus 30 includes an apparatus main body 31 including an intermediate transfer belt 16 and an image forming unit 33 disposed thereunder, and an image reading device 32 disposed above the intermediate transfer belt 16.

[0016] The device main body 31 incorporates a control unit (not shown) including a CPU, RAM, HDD, etc., and an image forming unit 33. The control unit (specifically, the CPU) transmits control signals to each part of the image forming device 30 in response to input operations by a user to an operation unit, causing the image forming device 30 to perform various operations.

[0017] The image data handled in the image forming unit 33 corresponds to color images of four colors: black (K), cyan (C), magenta (M), and yellow (Y). For this reason, four developing devices, photosensitive drums, etc. are provided so as to form four types of latent images corresponding to each color, and these constitute four image stations.

[0018] The image forming unit 33 forms a multi-color toner image on the intermediate transfer belt 16 by sequentially transferring the toner images of each color formed on each photosensitive drum of the four image stations onto the intermediate transfer belt 16 in a superimposed manner.

[0019] [First embodiment] Next, the intermediate transfer unit 10 will be described. FIG. 2A is an enlarged cross-sectional view of the intermediate transfer unit 10 of the image forming apparatus 30 shown in FIG. 1, and FIG. 2B is a view taken along the arrow 2B-2B in FIG. 2A. Referring to FIGS. 2A and 2B, the intermediate transfer unit 10 includes an intermediate transfer belt 16, a drive roller 14, a driven roller (not shown), and four intermediate transfer rollers, and is disposed above a photosensitive drum (not shown). The intermediate transfer belt 16 is a flexible, endless belt that is stretched by multiple rollers, including the drive roller 14 and driven rollers, and rotates (moves in a circular motion) in the direction indicated by the left arrow in FIG. 2A as the drive roller 14 is rotated.

[0020] The secondary transfer roller 15 is disposed opposite the drive roller 14 with the intermediate transfer belt 16 sandwiched therebetween. When a sheet of paper (not shown) passes through a nip N between the secondary transfer roller 15 and the intermediate transfer belt 16 in the direction of the arrow pointing to the upper right in FIG. 2A, the toner image formed on the intermediate transfer belt 16 is transferred to the sheet. On the downstream side of the nip N in the paper transport direction, near the uppermost position of the drive roller 14, a shield 12 is provided attached to the post-transfer PG 11 in the center of the drive roller 14 in the longitudinal direction (axial direction). The shield 12 is a rectangular flat plate with a recess in the center, and acts as a paper intrusion prevention member.

[0021] The central recess does not necessarily have to be provided. The shield 12, which acts as a paper intrusion prevention member, can prevent a paper jammed before fixing from entering the gap between the post-transfer PG 11 and the intermediate transfer belt 16.

[0022] Here, the diameter of the drive roller 14 is smaller than that of a conventional drive roller, so that the paper is not drawn along the outer periphery of the drive roller 14 in the direction of travel of the intermediate transfer belt 16 .

[0023] Also, here, the intermediate transfer belt 16 is illustrated so that the uppermost position of the drive roller 14 can be seen, but in reality, the intermediate transfer belt 16 is stretched by the drive roller 14 and a driven roller (not shown) and is linear.

[0024] Next, a further function of the shield 12 will be described. Figure 3 is a diagram showing the movement of toner 17 adhering to the shield 12 on the drive roller 14. Referring to the left diagram of Figure 3, toner 17 adheres to the shield 12 when a toner image is transferred to paper. As shown in the right diagram of Figure 3, this toner 17 falls from the shield 12 and is transported to the intermediate transfer belt 16, where it is collected by a cleaner (not shown).

[0025] Here, the uppermost position of the drive roller 14 is indicated by 14a. As shown in the figure, the shield 12 is located vertically above the drive roller 14 of the intermediate transfer belt 16 and downstream of the drive roller 14, i.e., downstream of the uppermost position 14a. Therefore, the toner 17 is transported to the intermediate transfer belt 16 and does not fall to the right of the uppermost position 14a of the drive roller 14 and adhere to the secondary transfer roller 15 or the paper.

[0026] Next, the positional relationship between the shield 12 and the intermediate transfer belt 16 will be described. FIG. 4A is a diagram showing the positional relationship between the shield 12 and the intermediate transfer belt 16, and is a view taken along the arrow 4A-4A in FIG. 3, and FIG. 4B is a cross-sectional view of the portion indicated by the arrow 4B-4B in FIG. 4A. Referring to FIGS. 4A and 4B, a gap 19 having a predetermined dimension is provided between the shield 12 and the intermediate transfer belt 16, and the dimension of the gap 19 is equal to or greater than a first predetermined distance and equal to or less than a second predetermined distance. Specifically, the first predetermined distance is 1 mm, and the second predetermined distance is 2 mm. That is, the dimension of the gap 19 is equal to or greater than 1 mm and equal to or less than 2 mm.

[0027] In this way, the gap 19 having a predetermined dimension is provided between the shield 12 and the intermediate transfer belt 16, so that the intrusion of paper can be further prevented.

[0028] Next, a specific mounting position of the shield 12 will be described. Fig. 5 is a plan view of the intermediate transfer unit 10 as seen from above. Referring to Fig. 5, the intermediate transfer unit 10 is provided with an intermediate transfer belt 16 whose right end is wound around a drive roller (not shown) and whose left end is wound around a driven roller (not shown), and the intermediate transfer belt 16 moves from right to left as indicated by the arrow in the figure. A bridge member 22 is provided at the right end of the intermediate transfer unit 10 so as to cover the entire width of the intermediate transfer belt 16, and the shield 12 is provided in the center of the bridge member 22.

[0029] The shield 12 is provided in a position that covers the vicinity of the center in the width direction perpendicular to the rotation direction of the intermediate transfer belt 16. Because the shield 12 is provided in a position that covers the vicinity of the center in the width direction of the intermediate transfer belt 16, it is possible to prevent the intrusion of paper of all sizes through the nip portion N.

[0030] Here, it is preferable that the width of the shield 12 is at least ¼ of the width of the intermediate transfer belt 16. This is because if the width of the shield 12 is at least ¼ of the width of the intermediate transfer belt 16, it is possible to prevent the intrusion of paper regardless of the width dimension of the paper.

[0031] [Second embodiment] Next, another embodiment of the present invention will be described. FIG. 6 is a diagram showing another embodiment of the present invention, and corresponds to FIG. 2B of the previous embodiment. Referring to FIG. 6, in this embodiment, unlike the previous embodiment, two shields 12a and 12b are provided (shown with hatching in the figure). Here, the two shields 12a and 12b are provided at equal intervals so as to divide the bridge member 22 of the transferred PG 11 into thirds. The two shields 12a and 12b provided here have a smaller width than the shield 12 in the previous embodiment. Furthermore, the two shields 12a and 12b provided here are rectangular flat plates and do not have a recess in the upper central portion.

[0032] [Third embodiment] Next, a further embodiment of the present invention will be described. Figure 7A is a view showing a further embodiment of the present invention, and corresponds to Figure 6 in the previous embodiment. Figure 7B is a cross-sectional view of the portion indicated by arrow 7B-7B in Figure 7A.

[0033] 7A and 7B, in this embodiment, a part of the lower end of the central portion of shield 12c (indicated by a dotted line in the figure) is inclined 45 degrees downward to the right (toward nip portion N). In this embodiment, shield 12c may have a smaller width than shield 12, as in the previous embodiment.

[0034] In this way, by providing the shield 12c with a part of the bottom end inclined downward to the right, the strength of the shield 12c is increased and the intrusion of paper can be further prevented.

[0035] Here, in the figure, the tilt angle to the lower right is set to 45 degrees, but this is not limiting and the tilt angle may be any angle greater than 0 degrees.

[0036] This inclined portion may be provided not only on a part of the shield 12c but also on the entire lower end portion.

[0037] As described above, in this invention, a paper intrusion prevention member is provided between the post-transfer PG provided on the intermediate transfer belt and the transfer belt on the downstream side of the paper transport from the nip portion N, thereby preventing paper that has jammed before fixing from entering the intermediate transfer unit.

[0038] The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-described embodiments are merely examples and should not be interpreted as being limiting. All modifications and variations within the scope of the claims of the present invention are within the scope of the present invention. [Industrial Applicability]

[0039] INDUSTRIAL APPLICABILITY According to the present invention, it is possible to prevent jammed paper from entering the intermediate transfer unit before fixing, and therefore it is useful as an intermediate transfer unit of an image forming apparatus. [Explanation of symbols]

[0040] 10 Intermediate transfer unit 11 Post-transcription PG (Paper Guide) 12 Shield 14 Drive roller 15 Secondary transfer roller 16 Intermediate transfer belt 17 Toner 19 Gap 22 Bridge members 30 Image forming device 31 Device body 32 Image reader 33 Image forming unit

Claims

1. an intermediate transfer belt onto which a multi-color toner image is formed by sequentially transferring and superimposing a plurality of color toner images formed on a plurality of photosensitive drums; a drive roller that drives the intermediate transfer belt; a secondary transfer roller disposed opposite the drive roller, a nip portion is formed between the drive roller and the secondary transfer roller; A color image is transferred onto the paper by conveying the paper to the nip portion, a post-transfer paper guide provided on the intermediate transfer belt downstream of the nip portion in the paper transport direction; a paper intrusion prevention member that is a rectangular flat plate that is long in the axial direction of the drive roller and is provided between the post-transfer paper guide and the intermediate transfer belt, In the image forming apparatus, a part of a lower end of the central portion of the paper intrusion prevention member is inclined toward the nip portion with respect to an upper portion of the central portion.

2. 2. The image forming apparatus according to claim 1, wherein the paper intrusion prevention member is provided at a position that covers the center of the intermediate transfer belt in the width direction.

3. 3. The image forming apparatus according to claim 1, wherein a gap of at least a first predetermined distance and not more than a second predetermined distance is provided between the paper intrusion prevention member and the intermediate transfer belt.

4. 2. The image forming apparatus according to claim 1, wherein the paper intrusion prevention member is provided vertically above the drive roller of the intermediate transfer belt and downstream of the uppermost position of the drive roller.

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