Image forming device

Abstract

To reduce an occurrence risk of an image mark while suppressing an increase of conveyance resistance, in a curved conveyance passage between a separation roller and a pull-up conveyance roller.SOLUTION: An image forming apparatus 201 comprises: a separation conveyance roller pair 10 for separating and conveying paper sheets one by one; a pull-up conveyance roller pair 9 for conveying the paper sheets delivered from the separation conveyance roller pair 10 toward an image forming part 201B; and an inner guide 6 and an outer guide 7 for forming a curved conveyance passage between the separation conveyance roller pair 10 and the pull-up conveyance roller pair 9. The inner guide 6 has an inner guide extension part 8 that extends to the outer guide 7 side than a common external tangent L1 of a feed roller 2 and a pull-up drive roller 91. The inner guide extension part 8 has a face guide part 81 formed so as to straddle inter-roller end part lines L21, L22, L23 and L24, and rib guide parts 82 and 83 provided outward in a thrust direction of the face guide part 81.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus that forms an image on a sheet of paper. [Background technology]

[0002] In image forming devices such as copiers, printers, and facsimiles, multiple pairs of conveying rollers are arranged on a conveying path from a storage cabinet that stores paper to an image forming unit. In the image forming device disclosed in Patent Document 1, paper is supplied to the conveying path from the storage cabinet by a pickup roller, and is conveyed toward the image forming unit by multiple pairs of conveying rollers, such as a separation conveying roller pair, a pull-out conveying roller pair, and a registration roller pair.

[0003] However, due to the structure of the image forming apparatus, the conveying path between the separation conveying roller pair and the pull-out conveying roller is often curved rather than straight. When paper is conveyed along such a curved conveying path, the paper conveying resistance tends to be greater than when conveyed along a straight conveying path. Therefore, various measures have been taken to reduce the conveying resistance.

[0004] In the image forming device of Patent Document 1, the inner guide of the curved conveyance path is positioned closer to the inner periphery of the curved conveyance path than the common external tangent line L1 of the separation conveyance roller and the pull-out conveyance roller, preventing the paper from contacting the inner guide when the paper is conveyed by the pull-out conveyance roller, thereby suppressing an increase in conveyance resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-183309 Summary of the Invention [Problem to be solved by the invention]

[0006] In the configuration of Patent Document 1, when transporting thin paper with low stiffness, the paper does not travel along the outer guide of the curved transport path, resulting in changes in paper posture and deterioration of the paper's geometric characteristics. Therefore, it is preferable to narrow the guide gap between the inner and outer guides in the curved transport path as much as possible, but narrowing the guide gap between the inner and outer guides tends to increase transport resistance. Therefore, a method is generally adopted in which the guide gap of the transport guide is narrowed while ribs are formed on the surface of the transport guide to reduce the contact area between the transport guide and the paper, thereby suppressing changes in paper posture and reducing transport resistance.

[0007] However, when ribs are formed on the surface of the conveying guide, the following problems arise, particularly in the curved conveying path provided between the separating conveying roller and the drawing conveying roller.

[0008] The paper conveyed by the separation conveyance roller pair and the pull-off conveyance roller pair is pulled by the pull-off conveyance roller pair while being conveyed. This is due to factors such as the fact that the separation conveyance roller pair is subjected to conveyance resistance due to the action of a torque limiter, and that the driving force to the separation conveyance roller pair is cut off after the paper reaches the pull-off conveyance roller pair. When the paper is pulled by the pull-off conveyance roller, the paper rubs against a specific portion of the inner guide of the curved conveyance path with great contact pressure. If the above-mentioned ribs are formed in the portion where the paper contacts this inner guide with high contact pressure, the friction between the ribs and the paper will cause dents and scratches on the paper surface. These dents and scratches on the paper surface will cause image marks when an image is formed on the paper in the image forming unit.

[0009] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to suppress an increase in transport resistance and reduce the risk of image marks occurring. [Means for solving the problem]

[0010] In order to achieve the above object, an image forming apparatus according to the present invention is an image forming apparatus comprising: an image forming unit that forms an image on paper; a pair of separation and feeding rollers that separate and feed a plurality of sheets of paper stored in a storage case one by one; a pair of transport rollers that transport the paper handed over from the pair of separation and feeding rollers toward the image forming unit; and a pair of transport guides that are provided between the pair of separation and feeding rollers and the pair of transport rollers in the paper transport direction and form a curved transport path that guides the paper, wherein the pair of transport guides have an inner guide that is arranged on the inner side of the curved transport path and an outer guide that is arranged on the outer side of the curved transport path, and the pair of separation and feeding rollers are arranged on the inner guide side of the curved transport path, a feed roller that feeds paper, and a separation roller that is arranged on the outer guide side of the curved conveying path so as to abut against the feed roller and separates the paper sheets one by one, the conveying roller pair having a drive roller that is arranged on the inner guide side of the curved conveying path and driven by a drive source, and a driven roller that is arranged on the outer guide side of the curved conveying path so as to abut against the drive roller and is driven by the rotation of the drive roller, when viewed from the width direction of the paper which is perpendicular to the conveying direction of the paper, a part of the guide surface of the inner guide protrudes from a common circumferential line of the drive roller and the feed roller towards the outer guide, and an intersection of the common circumferential line with the feed roller when viewed from the width direction of the paper is referred to as a first intersection, and a second intersection of the common circumferential line with the feed roller when viewed from the width direction of the paper is referred to as a third intersection. through circumscription When the intersection of the line with the drive roller is defined as the second intersection, and when viewed from the conveying direction of the paper, both ends of the paper in the width direction at the first intersection of the feed roller and both ends of the paper in the width direction at the second intersection of the drive roller are defined as vertices, in the inner region of the guide surface of the inner guide formed by connecting the vertices, the guide surface of the inner guide is formed linearly and continuously in the width direction of the paper, and when viewed from the conveying direction of the paper, the outer region of the inner guide that is not the inner region has rib-shaped rib guide portions that are spaced apart in the width direction of the paper and extend in the conveying direction of the paper and protrude toward the outer guide. [Effects of the Invention]

[0011] According to the present invention, it is possible to suppress an increase in transport resistance and reduce the risk of image marks occurring. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 10 is a side view showing the surface guide and rib configuration in the first embodiment. [Figure 2] FIG. 1 is a front cross-sectional view showing an inner guide, a common circumferential tangent, and an inner guide protrusion in the first embodiment. [Figure 3] FIG. 1 is a side view showing the roller end line and the inner guide in the first embodiment. [Figure 4] FIG. 10 is a side view showing the surface guide and rib configuration in the second embodiment. [Figure 5] FIG. 10 is a front cross-sectional view showing a common outer guide tangent and an inner guide protrusion in a second embodiment. [Figure 6] Image forming device DETAILED DESCRIPTION OF THE INVENTION

[0013] The configuration of the embodiment of the present invention will be described with reference to FIGS. 6, 1 and 2. FIG.

[0014] [Image forming device] Fig. 6 is a diagram showing a schematic configuration of an image forming apparatus 201 according to an embodiment of the present invention. In Fig. 6, image forming apparatus 201 is a full-color laser beam copier, and is composed of printer main body 201A, which is the image forming apparatus main body, and image forming section 201B and fixing section 220 housed in printer main body 201A. Also, image reading device 202 is installed approximately horizontally above printer main body 201A, and an ejection space for ejecting paper on which an image has been formed is formed between image reading device 202 and printer main body 201A. A paper feeding device constituting paper feeding section 101 is disposed below the printer main body.

[0015] Image forming section 201B is a four-drum full-color type and includes a laser scanner 210 and four process cartridges 211 that form toner images in four colors: yellow (Y), magenta (M), cyan (C), and black (K). Each process cartridge 211 includes a photosensitive drum 212, a charger 213 as charging means, a developer 214 as developing means, and a cleaner as cleaning means (not shown). Image forming section 201B also includes an intermediate transfer unit 201C disposed above the process cartridges 211.

[0016] The intermediate transfer unit 201C includes an intermediate transfer belt 216 wound around a drive roller 216a and a tension roller 216b. The intermediate transfer belt 216 is disposed in contact with each photosensitive drum 212 and rotates in the direction of the arrow by a drive roller 216a driven by a drive unit (not shown). The intermediate transfer unit 201C also includes a primary transfer roller 219 disposed inside the intermediate transfer belt 216 and abutting against the intermediate transfer belt 216 at a position facing the photosensitive drum 212. A secondary transfer roller 217, which constitutes a secondary transfer unit that transfers a color image formed on the intermediate transfer belt 216 onto paper, is disposed opposite the drive roller 216a of the intermediate transfer unit 201C. Toner cartridges 215 containing toners of each color are disposed above the intermediate transfer unit 201C.

[0017] By applying a transfer bias of positive polarity to the intermediate transfer belt 216 by the primary transfer roller 219, the negative color toner images on the photosensitive drum 212 are transferred in succession to the intermediate transfer belt 216 in multiple layers.

[0018] The paper fed by the paper feed device is transported to the pair of registration rollers 240, and any skew is corrected by the pair of registration rollers 240. The paper is then transported by the pair of registration rollers 240 to the secondary transfer section at a timing when the color image formed on the intermediate transfer belt 216 and the leading edge of the paper are aligned, and the toner image on the intermediate transfer belt 216 is transferred onto the paper.

[0019] The paper sheet onto which the toner image has been transferred is subjected to heat and pressure in fixing section 220, where the color image is fixed to the paper sheet. The paper sheet P with the fixed image is discharged to a discharge space by a pair of paper discharge rollers 225 and stacked. When forming images on both sides of the paper sheet, after the images have been fixed, the paper sheet P is transported to a re-conveyance path R by a pair of reversible reversing rollers 222 provided in double-sided reversing section 201D, and then transported again to image forming section 201B.

[0020] [Paper feeding section] The paper feed unit 101 for feeding paper will be described. It includes a pickup roller 1 that picks up paper S stored in paper storage 5, a feed roller 2 that transports the picked-up paper, and a retard roller 3 that faces the feed roller 3 and separates and transports multiple sheets of paper one by one. In the following description, the roller pair consisting of the feed roller 3 and the retard roller may be referred to as the "separation and transport roller pair."

[0021] Paper storage 5 is equipped with side regulation plates and rear end regulation plates for regulating the side and rear end positions of the set paper, and a middle plate for raising the set paper stack to a position where it can be fed by paper feed unit 101. Pickup roller 1 is pressed against the top surface of paper S stored in paper storage 5, and is rotated by the transmission of driving force from a paper feed motor (not shown). As pick roller 1 rotates, paper S is sent toward the separation nip formed by feed roller 3 and retard roller 2.

[0022] The drive transmission force (limit value) of the torque limiter 4 is set to be greater than the friction force generated between sheets of paper due to the friction coefficient of the paper being used. The drive transmission force (limit value) of the torque limiter 4 is also set to be smaller than the friction force due to the friction coefficient between the paper and the feed roller 2. Therefore, when only one sheet of paper S enters the separation nip between the feed roller 2 and the retard roller 3, or when no sheet of paper S is present, the retard roller 3 rotates along with the feed roller 2. When two or more sheets of paper S enter the nip, the retard roller 3 rotates in the opposite direction to the paper transport direction 8, separating the sheets of paper S one by one. The feed roller 2 rotates by receiving drive force from a paper feed motor (not shown).

[0023] The paper fed by the feed rollers 2 is transported along a curved transport path, which will be described later, and is handed over to the pull-out transport roller pair 9. The paper handed over to the pull-out transport roller pair 9 is then transported further to the registration roller pair 240, which is further downstream in the transport direction.

[0024] Next, referring to FIGS. 1, 2, and 3, we will explain the curved conveyance path between the separation conveyance roller and the pull-out conveyance roller, which is a characteristic feature of this embodiment. As shown in FIG. 2, the curved conveyance path is provided between the separation conveyance roller pair 10 and the pull-out conveyance roller pair 9. The separation conveyance roller pair 10 is a roller pair consisting of the feed roller 2 and the retard roller 3 described above. The pull-out conveyance roller pair 9 is a roller pair consisting of the pull-out drive roller 91 and the pull-out driven roller 92. The curved conveyance path is a curved conveyance path formed by a pair of guide members, an inner guide 6 and an outer guide 7, and is a conveyance path for conveying paper fed from the paper storage cabinet 5 toward the image forming unit 201B. The inner guide 6 is a guide member located on the inner periphery of the curved conveyance path and has an inner guide protrusion 8, which will be described later with reference to FIG. 3. The outer guide 7 is a guide member facing the inner guide 6 and located on the outer periphery of the curved conveyance path. Here, the feed roller 2 is located on the inner guide side of the curved conveyance path and upstream in the conveyance direction. The pull-out drive roller 91 is located on the inner guide side of the curved conveying path and downstream in the conveying direction. The retard roller 3 is located on the outer guide side of the curved conveying path and upstream in the conveying direction. The pull-out driven roller 92 is located on the outer guide side of the curved conveying path and downstream in the conveying direction.

[0025] As described above, the inner guide 6 that forms the curved conveying path is provided with an inner guide protrusion 8. The inner guide protrusion 8 is a portion that protrudes toward the outer guide 7 from the straight line L1 (see FIG. 2), which is a common circumferential line between the feed roller 2 and the pull-out drive roller 91. The shape of this inner guide protrusion 8 will be described in detail with reference to FIGS. 3 and 4. The straight line L1 in FIG. 2 is called the common circumferential line between the feed roller 2 and the pull-out drive roller 91. Strictly speaking, two common circumferential lines can be drawn between the feed roller 2 and the pull-out drive roller 91, but in this embodiment, the term "common circumferential line L1" refers to the common circumferential line that is closer to the outer guide of the curved conveying path out of the two common circumferential lines.

[0026] The inner guide protrusion 8 is a portion formed on the inner guide 6 to ensure an appropriate guide gap across the entire width of the paper between it and the opposing outer guide 7. The inner guide protrusion 8 is formed on the inner guide 6 for the following reason: When the paper being transported is thin paper with low stiffness, the leading edge of the paper transported from the feed roller 2 to the pull-out transport roller pair 9 may not align with the outer guide 7. This is because thin paper has low stiffness, so the posture of the leading edge of the paper is unstable. If the posture of the leading edge of the paper is unstable, the leading edge of the paper will bend or deform within the guide gap between the inner guide 6 and outer guide 7, which can easily cause transport problems or rotation in the paper transport direction.

[0027] Therefore, in this embodiment, in order to appropriately narrow the guide gap, an inner guide protrusion 8 is formed across the entire paper width of the inner guide 6 (see Figures 2 and 3). This configuration makes it possible to transport paper along a curved transport path without causing deformation of the paper, such as folding or bending. Furthermore, to improve geometric characteristics, it is necessary to transport paper while suppressing changes in its posture. By appropriately narrowing the guide gap across the entire paper width, it is possible to transport paper while suppressing changes in its posture.

[0028] By providing the inner guide protrusion 8, it is possible to suppress changes in the posture of thin paper during transport and improve geometric characteristics. However, on the other hand, the paper S is more likely to come into contact with the guide, which increases transport resistance.

[0029] Therefore, in this embodiment, in order to narrow the guide gap and suppress an increase in conveyance resistance, the inner guide protrusion 8 has multiple ribs extending in the conveyance direction arranged at appropriate intervals in the paper width direction. By forming multiple ribs extending in the conveyance direction on the inner guide 6, the contact area with the paper is reduced.

[0030] When a sheet of paper is conveyed while being sandwiched between the separation conveying roller pair 10 and the pull-out conveying roller pair 9, the sheet is pulled by the pull-out conveying roller pair 9 relative to the separation conveying roller pair 10. This is because the separation conveying roller pair 10 is subjected to conveyance resistance from the retard roller 3 due to the action of the torque limiter 4, and the driving force is cut off before the pull-out conveying roller pair 9. The sheet of paper S is pulled by this downstream conveying roller pair 9, so that tension is applied to the sheet of paper S, and the sheet of paper S is conveyed while in contact with the inner guide 6 (strictly speaking, the inner guide protrusion 8).

[0031] The smaller the contact area, the higher the contact pressure per unit area at the point of contact with the inner guide 6. Depending on the type of paper, the high contact pressure on the paper surface may cause dents, scratches, or changes in surface roughness (changes in paper surface properties) on the paper surface in the conveyance direction due to friction.

[0032] This change in paper surface properties can cause image defects such as image marks in the image forming unit. Image defects caused by changes in paper surface properties can occur, for example, when a sheet of paper S rubs against the surface of the curved conveyance path with high contact pressure, pushing out fillers, which are particles contained within the sheet, onto the sheet's surface, changing the electrical resistance of the sheet's surface at the rubbed position. As a result, when a sheet of paper is conveyed to the image forming unit downstream of the conveyance path, the transferability of the sheet decreases at the secondary transfer unit (intermediate transfer belt 216 and secondary transfer roller 217). This phenomenon occurs when excessive current flows, causing discharge, which reduces the toner charge or reverses the charge polarity, resulting in a decrease in transferability. When this phenomenon occurs, there are areas on the sheet surface where the transferability has decreased due to the rub and areas where the transferability has not decreased, resulting in differences in density in the image, and these differences are recognized as image marks.

[0033] The contact pressure per unit area of the inner guide 6 is higher for a ribbed guide, which has a guide shape with ribs, than for a surface guide that makes surface contact (the guide shape that produces higher contact pressure is a ribbed guide rather than a surface contact guide). While using a ribbed guide can reduce transport resistance, it can also be a cause of image defects in the image forming section. Conversely, to reduce contact pressure, it is preferable to use a surface-shaped guide rather than a ribbed guide.

[0034] One of the factors that increases the contact pressure against the inner guide 6 is the tension on the transported paper S. As described above, tension is applied to the paper S by the pulling of the pull-out transport roller pair 9, but the area where a particularly large tension is applied is the area surrounded by the inter-roller end line L2 (including the area on the line) shown in FIG.

[0035] FIG. 3 is a diagram illustrating the curved conveying path portion as viewed from the side of FIG. 2. In this embodiment, two pairs of pull-out conveying rollers 9 (pull-out driving roller 91 and pull-out driven roller 92) are provided in the thrust direction (axial direction). That is, two pull-out driving rollers 91 are attached to the shaft with a gap between them in the thrust direction. Similarly, two pull-out driven rollers 92 are attached to the shaft with a gap between them in the thrust direction. In addition, there is one pair of separation conveying rollers 10 (feed roller 2 and retard roller 3). One feed roller 2 is provided in the center in the thrust direction.

[0036] In this embodiment, the point of contact of the feed roller 2 at the common external tangent L1 at the end in the thrust direction is referred to as the "upstream roller end tangent P1," and the tangent at the end in the thrust direction of the pull-out drive roller 9 is referred to as the "downstream roller end tangent P2." The line connecting the upstream roller end tangent P1 and the downstream conveying roller end tangent P2 is referred to as the roller end line L2 (L21, L22, L23, L24).

[0037] The tension on the sheet S is particularly high in the area surrounded by the roller end line L2 (including the area above the line) of each roller pair. That is, the area with high tension is between roller end line L21 and roller end line L24. Furthermore, the tension is even higher between roller end lines L21 and L22 and between roller end lines L23 and L24.

[0038] In this high tension range, it becomes necessary to reduce the contact pressure per unit area at the contact point in order to reduce changes in the paper surface properties.To reduce the contact pressure per unit area at the contact point, it is effective to use a flat guide rather than a ribbed guide to increase the contact area.

[0039] As described above, the area surrounded by the roller end line L2 (including the area on the line) has high contact pressure when the downstream transport roller pair 9 pulls the paper.

[0040] Therefore, in this embodiment, as shown in FIG. 3, a surface guide portion 81 having a surface guide shape is disposed in the inner guide protrusion portion so as to straddle the roller end line L2.

[0041] The surface guide shape of the surface guide portion 81 that straddles the roller end line L2 varies depending on the curvature of the curved conveyance path, the type of paper being conveyed, and the degree of tension between the separation conveyance roller pair 10 and the pull-out conveyance roller pair 9. In this embodiment, the surface guide shape is a shape that straddles a width of about 3 mm or more in the conveyance direction and thrust direction. This allows the surface guide to cover the range where the contact pressure with the paper during pull-out is high, thereby suppressing changes in the paper surface properties due to friction with the guide portion and reducing image defects.

[0042] In this embodiment, the inner guide 6 has a surface guide portion 81 only in the area including the inter-roller edge line where contact pressure is high, and rib-shaped rib guide portions 82 and 83 with a small contact area are provided on the outer side of the surface guide portion 81 in the thrust direction. This configuration makes it possible to suppress changes in posture and increases in conveyance resistance when the sheet is conveyed to the pull-out conveyance roller pair 9.

[0043] The width of the rib guide portions 82 and 83 in the thrust direction is 2 mm or less. It is preferable that the amount of protrusion of the rib guide portions 82 and 83 from the common external tangent line L1 to the outer guide be equal to or less than the amount of protrusion of the surface guide portion 81.

[0044] (Effects of this embodiment) As described above, in this embodiment, the posture of the paper can be stabilized and the geometric characteristics can be improved by narrowing the guide gap of the curved conveying path between the separation conveying roller pair 10 and the pull-out conveying roller pair 9. In addition, the increase in friction resistance caused by narrowing the guide gap of the curved conveying path can be suppressed by forming rib-shaped guides 82, 83 on the surface of the inner guide 6.

[0045] Furthermore, in this embodiment, the area (surrounded by the roller end line) where the contact pressure (friction pressure) between the paper and the inner guide 6 when the paper is conveyed by the pull-out conveying roller pair 9 is particularly high is designated as the surface guide 81, which is a guide portion having a surface shape. This makes it possible to suppress changes in the paper surface properties due to the friction pressure between the paper and the conveying guide. As a result, the risk of image marks caused by changes in the paper surface properties is reduced, and image defects are suppressed.

[0046] (Second embodiment) The second embodiment will be described with reference to Figures 4 and 5. As mentioned above, tension is applied to the paper S by the pair of pull-out conveying rollers 9 pulling the paper. Here, particularly large tension is applied in the range between roller end lines L21 and L24. Furthermore, within the above range of the inner guide protrusion 8, the part that protrudes further outward generates a higher contact pressure with the conveyed paper S.

[0047] On the other hand, within the inner guide extension 8, the contact pressure is relatively low in the range inside the common external guide tangent line L3 between the inner guide extension 8 and the inner downstream roller 91 and the inner upstream roller 2.

[0048] As a measure against changes in the paper surface properties, the area of the inner guide extension of the surface guide shape needs to be large enough to provide a pressure that does not cause changes in the paper surface properties, so only the area with the higher contact pressure may be made into a surface.

[0049] For example, in order to make only the area with higher contact pressure a surface guide, the area on the inner side of the downstream guide common circumferential tangent L32 (Figure 5) between the pull-out conveying roller pair 9 and the inner guide extension portion may be made into a rib shape 83 rather than a surface guide shape, and the upstream side may be made into a surface guide shape.

[0050] (Example of effect shape similar to above) The same may be applied to the area on the inner circumferential side of the upstream guide common circumferential tangent line L31 between the upstream conveying roller pair and the inner guide protrusion portion.

[0051] (Variation) To achieve the same effect as in the above-described embodiment, the material of the protruding portion of the inner guide may be different from that of the other guide portions. The protruding portion of the inner guide may be a separate component from the other guide portions. The surface guide shape of the protruding portion of the inner guide may be a continuous surface or a discontinuous surface. [Explanation of symbols]

[0052] 1 Pickup roller 2 Feed rollers 3 Retard roller 4 Torque limiter 5 Paper storage cabinet 6 Inner guide 7 Outer guide 8 Inner guide extension 81 Surface guide part 82, 83 Rib guide section 9 Pull-out conveying roller pair 91 Pull-out drive roller 92 Pull-out driven roller 10 Separation roller pair L1 common external tangent P1, P2 roller end contacts L2 (L21, L22, L23, L24) Roller end line L3 Guide Common Outer Tangent L31 Upstream guide common external tangent L32 Downstream guide common external tangent 101 Paper feeding section 201 Full color laser beam printer 201A printer body 201B Image forming section 201C Intermediate Transfer Unit 201D double-sided reversal unit 202 Image reader 210 Laser Scanner 211 Process cartridge 212 Photosensitive drum 213 Charger 214 Developer 215 Toner cartridge 216 Intermediate transfer belt 216a Drive roller 216b Tension roller 217 Secondary transfer roller 219 Primary transfer roller 220 Fixing unit 222 Reversing roller pair 225 Paper ejection roller pair 240 Registration Roller Pair

Claims

1. an image forming unit that forms an image on a sheet; a pair of separation and feeding rollers for separating and feeding the plurality of sheets stored in the storage case one by one; a pair of conveying rollers that convey the paper sheet passed from the pair of separation and feeding rollers toward the image forming unit; a pair of conveyance guides that are provided between the pair of separation and feeding rollers and the pair of conveyance rollers in the sheet conveyance direction and form a curved conveyance path that guides the sheet; An image forming apparatus having the pair of conveying guides includes an inner guide disposed on an inner circumferential side of the curved conveying path and an outer guide disposed on an outer circumferential side of the curved conveying path, the pair of separation and feeding rollers includes a feeding roller that is disposed on the inner guide side of the curved conveying path and feeds paper, and a separation roller that is disposed on the outer guide side of the curved conveying path so as to abut against the feeding roller and separates the paper sheets one by one; the conveying roller pair includes a drive roller that is disposed on the inner guide side of the curved conveying path and is driven by a drive source, and a driven roller that is disposed on the outer guide side of the curved conveying path so as to abut against the drive roller and is driven by the rotation of the drive roller, When viewed from a width direction of the paper that is perpendicular to the conveying direction of the paper, a part of the guide surface of the inner guide protrudes from a common circumferential line of the drive roller and the feed roller toward the outer guide, an intersection of the common circumferential line with the feed roller when viewed from the width direction of the paper sheet is defined as a first intersection, and an intersection of the common circumferential line with the drive roller is defined as a second intersection; When viewed from the conveyance direction of the paper, if both ends of the paper in the width direction at the first intersection of the feed roller and both ends of the paper in the width direction at the second intersection of the drive roller are taken as vertices, in an inner region of the guide surface of the inner guide formed by connecting the vertices, the guide surface of the inner guide is formed linearly and continuously in the width direction of the paper, When viewed from the paper transport direction, an outer region of the inner guide other than the inner region has rib-shaped rib guide portions that are spaced apart in the width direction of the paper, extend in the paper transport direction, and protrude toward the outer guide; An image forming apparatus comprising:

2. a torque limiter that applies a load to the rotation of the separation roller in the width direction of the paper; 2. The image forming apparatus according to claim 1, wherein:

3. The drive roller includes a first drive roller and a second drive roller that are spaced apart in the width direction of the paper and form a nip with the driven roller, a distance between both ends of the paper in the width direction at the first intersection of the feed roller is shorter than a distance between an outer side of the paper in the width direction at the second intersection of the first drive roller and an outer side of the paper in the width direction at the second intersection of the second drive roller; 2. The image forming apparatus according to claim 1, wherein:

4. While the sheet is being nipped and conveyed between the pair of separation and feeding rollers and the pair of conveying rollers, the driving force for the pair of separation and feeding rollers is cut off.

2. The image forming apparatus according to claim 1, wherein:

5. a protrusion amount of the guide surface of the inner guide from the common circumferential tangent line toward the outer guide is equal to the protrusion amount of the rib guide portion; 2. The image forming apparatus according to claim 1, wherein:

Images