JP2020183309A - Paper conveying device and image forming device - Google Patents

Abstract

To provide a paper conveying device capable of reducing conveyance resistance of a curved conveying path with a simple structure, and an image forming device.SOLUTION: A paper conveying device 10 has an upstream side conveyance roller pair 110, a downstream side conveyance roller pair 120, and a conveyance guide pair 130. The conveyance guide pair 130 forms a curved conveying path between the upstream side conveyance roller pair 110 and the downstream side conveyance roller pair 120. The upstream side conveyance roller pair 110 comprises an inner peripheral side upstream roller 111 arranged on a curved inner peripheral side, and an outer peripheral side upstream roller 112 arranged on a curved outer peripheral side. Similarly, the downstream side conveyance roller pair 120 comprises an inner peripheral side downstream roller 121 and an outer peripheral side downstream roller 122, and the conveyance guide pair 130 comprises an inner peripheral side guide member 131 and an outer peripheral side guide member 132. The inner peripheral side guide member 131 does not have a portion projected to the outer peripheral side of a common circumscribing line L1 of the inner peripheral side upstream roller 111 and the inner peripheral side downstream roller 121.SELECTED DRAWING: Figure 2

Description

The present invention relates to a paper transport device that transports paper on a curved transport path, and an image forming apparatus including the same.

The image forming apparatus needs to convey the paper in the conveying path in the image forming process, and the image forming apparatus includes the paper conveying device inside the conveying path. The paper transport device includes a transport guide for forming a transport path and a transport roller arranged along the transport path.

Usually, the transport path in the image forming apparatus includes at least a partially curved transport path (hereinafter, curved transport path) (Patent Document 1 or 2). FIG. 8 is a cross-sectional view showing a schematic configuration of a conventional paper transport device 50 that transports paper on a curved transport path.

The paper transport device 50 has an upstream transport roller pair 510, a downstream transport roller pair 520, and a transport guide pair 530, and the transport guide pair 530 includes an upstream transport roller pair 510 and a downstream transport roller pair 520. It forms a curved transport path between them. The upstream side transport roller pair 510 includes an inner peripheral side upstream roller 511 arranged on the curved inner peripheral side and an outer peripheral side upstream roller 512 arranged on the curved outer peripheral side. Similarly, the downstream side transport roller pair 520 includes an inner peripheral side downstream roller 521 and an outer peripheral side downstream roller 522, and the transport guide pair 530 includes an inner peripheral side guide member 531 and an outer peripheral side guide member 532. ..

The transport guide pair 530 forms a curved transport path, and both the inner peripheral side guide member 531 and the outer peripheral side guide member 532 have a curved shape along the transport direction Y. Therefore, in the paper transport device 50, the inner peripheral side guide member 531 has a portion protruding toward the curved outer peripheral side from the common circumscribed line L of the inner peripheral side upstream roller 511 and the inner peripheral side downstream roller 521. The common circumscribed line refers to a common tangent line that touches both of the two circles and does not intersect the line segment connecting the centers of these two circles.

JP 2015-147672 Japanese Unexamined Patent Publication No. 2010-1127

When plain paper is transported by the conventional paper transport device 50 shown in FIG. 8, the plain paper having a weak stiffness easily bends along the curved transport path, so that it is not subject to a particularly large transport resistance even in the curved transport path. There is no. However, when a strong paper such as thick paper is conveyed, a large transfer resistance may be received in the curved transfer path.

When a strong thick paper is conveyed by the paper transfer device 50, the tip of the thick paper entering the curved transfer path from the upstream side transfer roller pair 510 is attached to the outer peripheral side guide member 532 as shown in FIG. 9A. They come into contact with each other and are conveyed while rubbing the tip against the outer peripheral side guide member 532. Further, the thick paper with strong elasticity does not bend significantly even in the curved transport path, and approaches the inner peripheral side guide member 531 as it is transported, and eventually comes into contact with the inner peripheral side guide member 531 as shown in FIG. 9B. To do. At this time, the thick paper comes into contact with the inner peripheral side guide member 531 at a portion protruding toward the curved outer peripheral side from the common circumscribed line L. The thick paper in contact with the inner peripheral side guide member 531 in this way receives a large transfer resistance due to friction with the inner peripheral side guide member 531.
If the circles are on the same side when viewed from the straight line, it is a circumscribed line.
When the paper transport resistance is increased in this way, a transport slip may be caused and a transport jam may occur. Conventionally, measures have been taken such as arranging another pair of transport rollers in the curved transport path or providing a rotating roller on the inner peripheral side guide member 531 to reduce the transport resistance. However, these measures have problems such as cost increase due to an increase in the number of parts and difficulty in securing a space for arranging parts.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a paper transport device and an image forming device capable of reducing the transport resistance of a curved transport path with a simple configuration.

In order to solve the above problems, the paper transport device according to the first aspect of the present invention is a paper transport device that transports paper in a curved transport path in the image forming device, and is on the upstream side of the curved transport path. A curved transport path is provided between the upstream transport roller pair arranged in, the downstream transport roller pair arranged on the downstream side of the curved transport path, and the upstream transport roller pair and the downstream transport roller pair. It has a transport guide pair to be formed, and the upstream transport roller pair is arranged on the inner peripheral side upstream roller arranged on the inner peripheral side of the curved transport path and on the outer peripheral side of the curved transport path. The downstream side transport roller pair includes an outer peripheral side upstream roller, and the downstream side transport roller pair includes an inner peripheral side downstream roller arranged on the inner peripheral side of the curved transport path and an outer peripheral side arranged on the outer peripheral side of the curved transport path. The transport guide pair includes a downstream roller, and the transport guide pair includes an inner peripheral side guide member arranged on the inner peripheral side of the curved transport path and an outer peripheral side guide member arranged on the outer peripheral side of the curved transport path. The guide member on the inner peripheral side does not have a portion overhanging the outer peripheral side of the curved transport path from the common outer tangent line between the upstream roller on the inner peripheral side and the downstream roller on the inner peripheral side. It is a feature.

According to the above configuration, since the inner peripheral side guide member does not have a portion protruding to the outer peripheral side from the common outer tangent line of the inner peripheral side upstream roller and the inner peripheral side downstream roller, it is strong against thick paper or the like. When the paper is conveyed, it is possible to prevent the paper from coming into contact with the inner peripheral side guide member. As a result, it is possible to prevent the paper from coming into contact with the inner peripheral side guide member and receiving a large transfer resistance due to friction with the inner peripheral side guide member.

Further, in the paper transport device, the inner peripheral side guide member may be configured such that the entire guide surface thereof is a flat surface portion.

Further, in the paper transport device, the inner peripheral side guide member is composed of a curved region on the upstream side from the boundary point in the paper transport direction and a linear region on the downstream side from the boundary point in the paper transport direction, and the curved region. Has a curved surface portion at least in part, and the linear region can be configured such that the entire linear region is formed as a flat surface portion.

According to the above configuration, the paper entrance of the curved transport path is widened by the curved region of the inner peripheral side guide member to facilitate paper entry, so that even paper having wavy tips is smoothly curved. Can guide you to the transport route.

Further, in the paper transport device, the boundary point refers to an intersection where the tangent line intersects the guide surface of the outer peripheral side guide member when the tangent line passing through the nip portion of the upstream side transport roller pair is extended to the downstream side. The boundary point may be set to face the intersection.

Further, in the paper transport device, the curved region of the inner peripheral side guide member has a curved surface portion only near the center in the paper width direction, and both sides of the curved surface portion in the paper width direction are flat portions. The curved surface portion may be formed of a curved surface that is convex toward the inner peripheral side of the curved transport path.

According to the above configuration, the paper having waviness near the center of the tip can be smoothly guided to the curved transport path, and the fluttering of the paper is suppressed near both ends in the paper width direction. Paper can be smoothly conveyed to the transfer roller pair.

Further, in the paper transport device, the guide surface of the inner peripheral side guide member may have a shape without ribs.

Further, in the paper transport device, in the downstream transport roller pair, the diameter of the inner peripheral side downstream roller is set to be larger than the diameter of the outer peripheral side downstream roller, and the inner peripheral side downstream roller is set. The drive roller and the downstream roller on the outer peripheral side can be configured as a driven roller.

According to the above configuration, when a paper such as thick paper with strong stiffness is conveyed in the paper transfer device, the paper that reaches the downstream side transfer roller pair first contacts the inner peripheral side downstream roller and is a drive roller. It can receive the conveying force of the inner peripheral side downstream roller. As a result, it is possible to suppress poor transportation of thick paper and the like.

Further, in order to solve the above-mentioned problems, the image forming apparatus according to the second aspect of the present invention is characterized in that the above-described paper conveying apparatus is mounted.

The paper transporting device and the image forming apparatus of the present invention can prevent the paper from coming into contact with the inner peripheral side guide member when transporting strong paper such as thick paper, and as a result, the paper is brought to the inner peripheral side guide member. It has the effect of suppressing the contact and receiving a large transfer resistance due to the friction with the inner peripheral side guide member.

It shows an embodiment of the present invention, and is a schematic cross-sectional view of an image forming apparatus. It is a figure which shows the schematic structure of the paper transporting apparatus which concerns on Embodiment 1, (a) is the sectional view of the paper transporting apparatus, (b) is the plan view seen from the guide surface of the inner peripheral side guide member. (A) and (b) are cross-sectional views showing a paper transport mode in the case of transporting strong paper by the paper transport device of FIG. It is sectional drawing which shows the schematic structure of the paper transporting apparatus which concerns on Embodiment 2. FIG. It is sectional drawing which shows the schematic structure of the paper transporting apparatus which is the modification of Embodiment 2. 5A and 5B are views showing the arrangement relationship between the inner peripheral side guide member and the paper feed roller pair in the paper transport device of FIG. 5, where FIG. 5A is a perspective view seen from the guide surface of the inner peripheral side guide member, and FIG. It is a top view seen from the guide surface of the peripheral side guide member. It is sectional drawing which shows the schematic structure of the paper transporting apparatus which concerns on Embodiment 3. It is sectional drawing which shows the schematic structure of the conventional paper transfer apparatus. (A) and (b) are cross-sectional views showing a paper transport form in the case of transporting strong paper by the paper transport device of FIG.

[Embodiment 1]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an example of an image forming apparatus 100 to which the present invention is applied. The image forming apparatus 100 shown in FIG. 1 is a color image forming apparatus having a plurality of process units, but the present invention is not limited to this, and is a monochrome image forming apparatus having a single process unit. It can also be applied.

As shown in FIG. 1, the image forming apparatus 100 includes a main body portion 101, a document reading unit 102, a document conveying device 103, and a paper feeding device 104. The main body 101 has an image forming portion inside for printing an image on recording paper. The document scanning unit 102 is arranged above the main body section 101, and scans the document when copying the document. In the automatic scanning mode, the document transporting device 103 sequentially transports the documents placed on the document set tray toward the document loading table of the document scanning unit 102. The paper feed device 104 includes at least one paper feed cassette 104a for stocking the recording paper, and the recording paper is separated one by one by the pickup roller 104b provided in the selected paper feed cassette 104a and picked up. The recording paper is conveyed toward the main body 101 by the transfer roller pair 104c. In the main body 101, the recording paper sent from the paper feeding device 104 is first conveyed by the transfer roller pair 101c.

As the image data handled by the image forming apparatus 100, one corresponding to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y), or a single color (for example, black) is used. It corresponds to the monochrome image that was there. Therefore, the image forming apparatus 100 has four process units (image forming units) Pa to Pd associated with black, cyan, magenta, and yellow. Each process unit Pa to Pd forms a toner image according to the image data by using electrophotographic technology.

Each toner image formed by each process unit Pa to Pd is sequentially transferred and superposed on the intermediate transfer belt 61. As a result, a color toner image is formed on the intermediate transfer belt 61. The color toner image on the intermediate transfer belt 61 is transferred onto the recording paper, and the recording paper is heated and pressurized by the fixing device 10 to fix the color toner image on the recording paper.

Each process unit Pa to Pd has a configuration in which a charging unit, an exposure unit, a developing unit, a transfer unit, a cleaning unit, and a static elimination unit are arranged around the photoconductor drum 60 along the rotation direction of the photoconductor drum 60. Since each process unit Pa to Pd uses image formation using a known electrophotographic method, detailed description thereof will be omitted.

Subsequently, the paper transport device 10 according to the first embodiment will be described in detail with reference to the drawings. 2A and 2B are views showing a schematic configuration of the paper transport device 10 according to the first embodiment, FIG. 2A is a cross-sectional view of the paper transport device 10, and FIG. 2B is a view from the guide surface of the inner peripheral side guide member 131. It is a plan view. The paper transport device 10 is mounted on the image forming device 100 and transports paper in a curved transport path in the image forming device 100. Here, a case where the paper transport device 10 is used for transporting paper from the transport roller pair 104c of the paper feed device 104 to the transport roller pair 101c of the main body 101 will be illustrated. However, the arrangement location of the paper transport device 10 in the image forming apparatus 100 is not particularly limited.

The paper transport device 10 has an upstream transport roller pair 110, a downstream transport roller pair 120, and a transport guide pair 130, and the transport guide pair 130 includes an upstream transport roller pair 110 and a downstream transport roller pair 120. It forms a curved transport path between them. The upstream side transport roller pair 110 includes an inner peripheral side upstream roller 111 arranged on the curved inner peripheral side and an outer peripheral side upstream roller 112 arranged on the curved outer peripheral side. Similarly, the downstream transport roller pair 120 includes an inner peripheral side downstream roller 121 and an outer peripheral side downstream roller 122, and the transport guide pair 130 includes an inner peripheral side guide member 131 and an outer peripheral side guide member 132. .. In this example, the upstream transfer roller pair 110 corresponds to the transfer roller pair 104c of the paper feeding device 104, and the downstream transfer roller pair 120 corresponds to the transfer roller pair 101c of the main body 101.

The transport guide pair 130 forms a curved transport path, and the outer peripheral side guide member 132 has a shape curved along the transport direction Y. On the other hand, the inner peripheral side guide member 131 has a linear shape along the transport direction Y. More specifically, the inner peripheral side guide member 131 has a guide surface substantially parallel to the common circumscribed line L1 between the inner peripheral side upstream roller 111 and the inner peripheral side downstream roller 121. In other words, in the inner peripheral side guide member 131 according to the first embodiment, the entire guide surface is a flat surface (flat surface portion). The inner peripheral side upstream roller 111 and the inner peripheral side downstream roller 121 have two common circumscribed lines, but the common circumscribed line L1 here is the inner peripheral side upstream roller 111 and the inner peripheral side downstream roller 121. Refers to a common circumscribed line existing on the outer peripheral side of the curved transport path.

Further, in the paper transport device 10, the inner peripheral side guide member 131 does not have a portion overhanging the outer peripheral side of the common circumscribed line L1. In FIG. 2, the guide surface of the inner peripheral side guide member 131 is arranged so as to be on the inner peripheral side of the common circumscribed line L1, but the guide surface of the inner peripheral side guide member 131 is the common circumscribed line L1. It may be arranged so as to match.

When plain paper is transported by the paper transport device 10 according to the first embodiment, the weak plain paper easily bends along the curved transport path, and therefore receives a particularly large transport resistance even in the curved transport path. There is no. Further, the paper transport device 10 can prevent the paper to be transported from receiving a large transfer resistance in the curved transport path even when the paper having a strong stiffness such as thick paper is transported.

When the paper P transported by the paper transport device 10 is a strong thick paper or the like, the tip of the paper P entering the curved transport path from the upstream side transport roller pair 110 is as shown in FIG. 3A. It comes into contact with the outer peripheral side guide member 132 and is conveyed while rubbing the tip end against the outer peripheral side guide member 132. Further, the paper P having a strong stiffness does not bend significantly even in the curved transport path, and approaches the inner peripheral side guide member 131 as it is transported.

However, in the paper transport device 10, since the inner peripheral side guide member 131 does not have a portion overhanging the outer peripheral side of the common circumscribed line L1, even if the paper P approaches the inner peripheral side guide member 131 as it is conveyed, It is possible to prevent the paper P from coming into contact with the inner peripheral side guide member 131. That is, as shown in FIG. 3B, the tip of the paper P transported by the upstream transport roller pair 110 reaches the downstream transport roller pair 120 before coming into contact with the inner peripheral side guide member 131. After the tip reaches the downstream transfer roller pair 120, the paper P to be conveyed by the upstream transfer roller pair 110 and the downstream transfer roller pair 120 does not enter the inner peripheral side of the common circumscribed line L1 and is the paper. P does not come into contact with the inner peripheral side guide member 131. As a result, it is possible to prevent the paper P from coming into contact with the inner peripheral side guide member 131 and receiving a large transfer resistance due to friction with the inner peripheral side guide member 131.

Many of the transport guides in the conventional paper transport device are provided with ribs extending along the paper transport direction on the guide surface in order to reduce friction with the paper to be transported and reduce the transfer resistance. .. Even in the paper transport device 10, it is preferable that the guide surface of the outer peripheral side guide member 132 is provided with ribs. On the other hand, the inner peripheral side guide member 131 may be provided with ribs on the guide surface, but it is more preferable that the ribs are not provided. This is because the inner peripheral side guide member 131 of the paper conveying device 10 is arranged on the inner peripheral side of the common circumscribed line L1 to reduce the conveying resistance, and it is necessary to further provide ribs to reduce the conveying resistance. Because it is low. If the inner peripheral side guide member 131 has no ribs, it is possible to prevent the paper P to be conveyed from having rib streaks.

[Embodiment 2]
In the paper transport device 10 according to the first embodiment, the inner peripheral side guide member 131 has a linear shape along the transport direction Y. That is, the guide surface of the inner peripheral side guide member 131 is an overall flat surface. However, in the paper transport device of the present invention, the guide surface shape of the inner peripheral side guide member is not limited to a flat surface, and may have a curved surface at least partially. In the second embodiment, a paper transport device including an inner peripheral side guide member having a curved surface in part will be described. FIG. 4 is a cross-sectional view showing a schematic configuration of the paper transport device 20 according to the second embodiment.

The paper transport device 20 has a configuration similar to that of the paper transport device 10 shown in FIG. 2, and includes a paper feed roller pair 210 instead of the upstream side transport roller pair 110 of the paper transport device 10, and the inner peripheral side guide member 131. Instead, it is configured to include an inner peripheral side guide member 231. Therefore, the paper transport device 20 has basically the same configuration as the paper transport device 10 with respect to the downstream side transport roller pair 120 (inner peripheral side downstream roller 121 and outer peripheral side downstream roller 122) and the outer peripheral side guide member 132. .. Hereinafter, only the portion different from the paper transport device 10 will be described.

The paper feed roller pair 210 includes a paper feed roller 211 arranged on the curved inner peripheral side and a separation roller 212 arranged on the curved outer peripheral side. The paper feed roller pair 210 feeds and transports the paper picked up one by one from the paper bundle stored in the paper feed unit in the paper feed unit of the image forming apparatus on which the paper transport device 20 is mounted. .. In the paper feed roller pair 210, the transport speed of the separation roller 212 is set to be lower than the transport speed of the paper feed roller 211 in order to prevent double feeding of paper. In the paper transport device 20, the paper feed roller pair 210 corresponds to the upstream side transport roller pair described in the claims, the paper feed roller 211 corresponds to the inner peripheral side upstream roller, and the separation roller 212 corresponds to the outer peripheral side. Corresponds to the upstream roller.

The inner peripheral side guide member 231 has a curved region 231a on the upstream side of the boundary point A and a linear region 231b on the downstream side of the boundary point A. In the curved region 231a, the guide surface of the inner peripheral side guide member 231 is curved in the same direction as the guide surface of the outer peripheral side guide member 132. In the linear region 231b, the guide surface of the inner peripheral side guide member 231 is a flat surface having a linear shape along the transport direction Y. In this configuration, the paper entrance (upstream opening) of the curved transport path formed by the inner peripheral side guide member 231 and the outer peripheral side guide member 132 is widened by the curved region 231a, so that the paper P can easily enter. ing.

The tip of the paper P that receives the transfer of the paper feed roller pair 210 and enters the curved transfer path is wavy in the paper width direction due to the difference in transfer speed between the paper feed roller 211 and the separation roller 212. In the paper transport device 20, since the paper entrance of the curved transport path is widened to facilitate the entry of the paper P, even the paper P having a wavy tip is smoothly guided to the curved transport path. ..

In the inner peripheral side guide member 231 of the paper transport device 20, the position of the boundary point A, which is the boundary between the curved region 231a and the linear region 231b, is preferably set as follows. First, the tangent line (tangent line (common internal tangent line) L2 between the paper feed roller 211 and the separation roller 212) passing through the nip portion of the paper feed roller pair 210 is extended to the downstream side, and the tangent line L2 is with the guide surface of the outer peripheral side guide member 132. The intersection is defined as a point B, and the boundary point A is preferably a position facing the point B. Here, "the boundary point A faces the point B" means an outer peripheral side guide passing through the point B. It is assumed that the tangent line L3 with the guide surface of the member 132 is assumed to indicate a state in which the straight line connecting the boundary point A and the point B is substantially orthogonal to the tangent line L3. By setting the position of the boundary point A in this way, The upstream end of the curved region 231a of the inner peripheral side guide member 231 can be positioned higher than the central axis of the paper feed roller 211. As a result, the paper entrance of the curved transport path becomes wider, and the paper P Has an advantage that it can easily enter the curved transport path. Further, even if the paper edge portion in the direction orthogonal to the paper transport direction (paper edge portion in the paper width direction) is curled toward the inner circumference side, the paper P If the region until the tip of the paper reaches the point B is set as the curved region, it is possible to prevent the generation of noise due to the folding of the paper edge and the friction with the guide.

FIG. 5 is a cross-sectional view showing a schematic configuration of a paper transport device 21 which is a modification of the second embodiment. The paper transport device 21 has a configuration similar to that of the paper transport device 20 shown in FIG. 4, and includes an inner peripheral side guide member 233 instead of the inner peripheral side guide member 231 of the paper transport device 20. Hereinafter, only the parts different from the paper transport device 20 will be described.

FIG. 6 is a diagram showing the arrangement relationship between the inner peripheral side guide member 233 and the paper feed roller pair 210 (paper feed roller 211 and separation roller 212), and FIG. 6A is from the guide surface of the inner peripheral side guide member 233. The viewed perspective view (b) is a plan view seen from the guide surface of the inner peripheral side guide member 233.

Similar to the inner peripheral side guide member 231, the inner peripheral side guide member 233 has a curved region 233a on the upstream side of the boundary point A and a linear region 233b on the downstream side of the boundary point A. However, the curved region 233a does not have a curved surface as a whole, but has a curved surface portion 233c only near the center in the paper width direction, and both sides of the curved surface portion 233c in the paper width direction are flat surface portions 233d. ing. The curved surface portion 233c of the inner peripheral side guide member 233 is formed by a curved surface that is convex toward the inner peripheral side (that is, the outside of the transport path) of the curved transport path. It can be said that the entire linear region 233b is formed as a flat surface portion.

That is, the inner peripheral side guide member 233 has a curved surface portion 233c at a position facing the paper feed roller pair 210 in the paper transport direction Y, and at this position, the paper entrance of the curved transport path is widened by the curved surface portion 233c. Has been done. Therefore, even the paper P in which waviness is generated near the center of the tip by the paper feed roller pair 210 is smoothly guided to the curved transport path.

Further, in the paper P, there is little waviness near both ends in the paper width direction in which the paper feed roller pair 210 does not exist. For this reason, in the paper transport device 21, the vicinity of both ends of the inner peripheral side guide member 233 in the paper width direction is a flat surface portion 233d, and the paper entrance of the curved transport path is not widened at this location. As a result, the fluttering of the paper P is suppressed near both ends in the paper width direction, and the paper P can be smoothly conveyed to the downstream transfer roller pair 120.

In the inner peripheral side guide member 233, the width W1 at the upstream end of the curved surface portion 233c is preferably larger than the roller width W2 of the paper feed roller pair 210, and the width W1 is at least twice the roller width W2. Is more preferable.

[Embodiment 3]
FIG. 7 is a cross-sectional view showing a schematic configuration of the paper transport device 30 which is a modification of the third embodiment. The paper transport device 30 has a configuration similar to that of the paper transport device 10 shown in FIG. 2, and includes a downstream transport roller pair 320 instead of the downstream transport roller pair 120 of the paper transport device 10. Hereinafter, only the portion different from the paper transport device 10 will be described.

The downstream side transport roller pair 320 includes an inner peripheral side downstream roller 321 arranged on the curved inner peripheral side and an outer peripheral side downstream roller 322 arranged on the curved outer peripheral side. In the downstream side transport roller pair 320, the diameter of the inner peripheral side downstream roller 321 is set to be larger than the diameter of the outer peripheral side downstream roller 322. Further, in the downstream side transport roller pair 320, the inner peripheral side downstream roller 321 is a drive roller driven by a driving means such as a motor, and the outer peripheral side downstream roller 322 is a driven roller.

When the paper P such as thick paper with strong stiffness is conveyed in the paper transfer device 30, the paper P guided by the outer peripheral side guide member 132 to reach the downstream side transfer roller pair 320 first reaches the inner peripheral side downstream roller 321. It becomes easier to contact. Then, the paper P in contact with the inner peripheral side downstream roller 321 can receive the conveying force of the inner peripheral side downstream roller 321 which is a drive roller. As a result, the paper transport device 30 can suppress transport defects such as thick paper.

The embodiments disclosed this time are exemplary in all respects and do not provide a basis for limited interpretation. Therefore, the technical scope of the present invention is not construed solely by the above-described embodiments, but is defined based on the description of the claims. It also includes all changes within the meaning and scope of the claims.

10, 20, 30 Paper transport device 110 Upstream transport roller pair 111 Inner peripheral upstream roller 112 Outer peripheral upstream roller 120,320 Downstream transport roller pair 121,321 Inner peripheral downstream roller 122,322 Outer peripheral downstream roller 130 Transport Guide pair 131,231,233 Inner peripheral side guide members 231a, 233a Curved area 231b, 233b Straight area 233c Curved surface part 233d Flat part 210 Feeding roller pair (upstream side transport roller pair)
211 Paper feed roller (upper roller on the inner circumference side)
212 Separation roller (upper peripheral roller)

Claims (8)

A paper transport device that transports paper in a curved transport path in an image forming device.
A pair of upstream transport rollers arranged on the upstream side of the curved transport path,
A pair of downstream transport rollers arranged on the downstream side of the curved transport path,
It has a transport guide pair that forms a curved transport path between the upstream transport roller pair and the downstream transport roller pair.
The upstream side transport roller pair includes an inner peripheral side upstream roller arranged on the inner peripheral side of the curved transport path and an outer peripheral side upstream roller arranged on the outer peripheral side of the curved transport path.
The downstream transport roller pair includes an inner peripheral downstream roller arranged on the inner peripheral side of the curved transport path and an outer peripheral downstream roller arranged on the outer peripheral side of the curved transport path.
The transport guide pair includes an inner peripheral side guide member arranged on the inner peripheral side of the curved transport path and an outer peripheral side guide member arranged on the outer peripheral side of the curved transport path.
The paper is characterized in that the inner peripheral side guide member does not have a portion overhanging the outer peripheral side of the curved transport path from the common circumscribed line between the inner peripheral side upstream roller and the inner peripheral side downstream roller. Conveyor device. The paper transport device according to claim 1.
The inner peripheral side guide member is a paper transport device characterized in that the entire guide surface thereof is a flat surface portion. The paper transport device according to claim 1.
The inner peripheral side guide member includes a curved region on the upstream side from the boundary point in the paper transport direction and a linear region on the downstream side from the boundary point in the paper transport direction.
A paper transport device characterized in that the curved region has a curved surface portion at least in part, and the linear region is formed as a flat surface portion as a whole. The paper transport device according to claim 3.
The boundary point faces the intersection with respect to the intersection where the tangent line intersects the guide surface of the outer peripheral side guide member when the tangent line passing through the nip portion of the upstream side transport roller pair is extended to the downstream side. A paper transfer device characterized in that it is set to perform. The paper transport device according to claim 3 or 4.
The curved region of the inner peripheral side guide member has a curved surface portion only near the center in the paper width direction, and both sides of the curved surface portion in the paper width direction are flat portions.
The paper transport device is characterized in that the curved surface portion is formed of a curved surface that is convex toward the inner peripheral side of the curved transport path. The paper transport device according to any one of claims 1 to 5.
A paper transport device characterized in that the guide surface of the inner peripheral side guide member has a shape without ribs. The paper transport device according to any one of claims 1 to 6.
In the downstream transport roller pair, the diameter of the inner peripheral downstream roller is set to be larger than the diameter of the outer peripheral downstream roller, and the inner peripheral downstream roller is the drive roller and the outer peripheral downstream roller is. A paper transport device characterized by being a driven roller. An image forming apparatus comprising the paper conveying apparatus according to any one of claims 1 to 7.

Images