JP2006290525A - Sheet material feeding mechanism and image forming apparatus equipped with it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet material feeding mechanism capable of preventing roller tracks from being left on a surface of a sheet material and of more securely obtaining carrying amount in accordance with design. <P>SOLUTION: The sheet material feeding mechanism which is a paper discharging mechanism 53 of an image forming apparatus 21 is provided with a drive roller 69 rotated by a drive means; a driven roller 71 opposing to the drive roller 69 via a paper carrying path and rotated by force transmitted by paper; and support bodies supporting these rollers 69, 71, respectively. The driven roller 71 has a hollow part between the driven roller 71 and the support body, and the drive roller 69 has no hollow part or has a hollow part narrower than the driven roller 71, between the drive roller 69 and the support body. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a mechanism for conveying a sheet material by a roller and an image forming apparatus including the mechanism.

  2. Description of the Related Art Conventionally, in image forming apparatuses such as printers, copiers, and facsimiles, a sheet material such as paper is moved within an apparatus housing using a plurality of pairs of rollers. The image forming apparatus is provided with an image forming unit. A paper feed mechanism for conveying the sheet material toward the image forming unit is provided on the upstream side of the image forming unit, and the image-formed sheet material is discharged to the outside of the housing on the downstream side of the image forming unit. A paper discharge mechanism that conveys the paper toward the camera is provided.

Further, as a roller constituting the sheet feeding mechanism, a roller made of a hollow elastic body (hereinafter referred to as “hollow roller”) is used instead of a roller made of a solid elastic body (hereinafter referred to as “solid roller”). (See Patent Document 1).
JP 2004-175488 A

  However, in the conventional image forming apparatus, when the sheet material after image formation is conveyed while being sandwiched between a pair of solid rollers, a contact mark with the solid roller, that is, a roller mark may remain on the surface of the sheet material. According to the present applicant, since the toner for image formation adheres to the surface of the sheet material after image formation, it can be considered as one of the factors that leave a roller trace.

  On the other hand, in order to cope with the problem of the roller trace, a mode in which the sheet material after image formation is conveyed using a hollow roller is also conceivable. However, when the sheet material is conveyed using the hollow roller, the relationship between the rotation amount of the hollow roller and the sheet material conveyance distance is always caused by the deformation degree of the hollow roller being larger than that of the solid roller. There is a problem that does not match. That is, even if the roller is rotated as specified, the sheet material does not advance as specified, and there is a possibility that the sheet material that realizes the moving amount cannot be conveyed as designed. In particular, such a problem is important when performing double-sided printing or the like that involves reversing the front and back of a sheet material, and a roller that performs a reversing operation is required to have a stricter conveyance result as designed.

  The present invention has been made in view of the above, and it is possible to prevent roller traces from remaining on the surface of a sheet material, and to more reliably obtain a transport amount as designed. An object of the present invention is to provide a sheet material feeding mechanism and an image forming apparatus including the sheet material feeding mechanism.

  In order to solve the above-described problems, a sheet material feeding mechanism according to the present invention opposes a driving roller rotated by driving means, and faces the driving roller via a sheet material conveyance path, and transmits from the sheet material. An elastic cylindrical body that includes a driven roller that is rotated by the applied force and a support that supports the driving roller and the driven roller, respectively, and the driving roller and the driven roller are fitted to the outer periphery of the support, respectively. And the driven roller has a hollow portion between the support body and the drive roller has no hollow portion between the support body or a hollow space narrower than the driven roller. It has the part.

  Preferably, the support for supporting the driven roller includes a base portion and a slit, and the base portion has at least two or more ring-shaped concave grooves facing each other with a gap therebetween. The slit is provided so as to cross the inside of the concave groove and open to the outer peripheral surface of the base portion, and the air inside the hollow portion can be ventilated from the slit, and the driven The said elastic cylindrical body which comprises a roller is combined with the said support body so that the both-ends edge may be engage | inserted by the said corresponding groove.

  The present invention also provides an image forming apparatus for solving the same problem.

  The image forming apparatus includes an image forming unit, a paper feeding mechanism provided on the upstream side of the image forming unit, and a paper discharging mechanism provided on the downstream side of the image forming unit. The sheet discharge roller pair in the sheet discharge mechanism includes the driving roller and the driven roller.

  Preferably, a fixing roller pair is provided on the upstream side of the paper discharge roller pair, and a reversing roller pair and a paper discharge port are provided on the downstream side of the paper discharge roller pair. The drive roller in the pair of paper discharge rollers can be rotated in the forward rotation direction so that the sheet material is completely discharged through the paper discharge port, and is reversed so that the sheet material can be sent back to the pair of reverse rollers. It can also rotate in the direction.

  According to the present invention, it is possible to prevent roller traces from remaining on the surface of the sheet material, and it is possible to more reliably acquire the transport amount as designed.

  The other features of the present invention and the operational effects thereof will be described in more detail with reference to the accompanying drawings.

  Hereinafter, an embodiment in which the image forming apparatus according to the present invention is implemented as a laser beam printer (LBP) will be described with reference to the accompanying drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

  FIG. 1 is a diagram schematically showing a configuration of an image forming apparatus according to the present embodiment. The image forming apparatus 21 includes a plurality of pairs of rollers, an image forming unit 27, and the like inside a housing 25 having a leg portion 23 on the bottom surface.

  A paper feeding mechanism 29 is provided on the upstream side of the image forming unit 27. The paper feed mechanism 29 includes a paper feed roller 31. A paper stacking tray 33 is provided on the upstream side of the paper feed roller 31 in the paper transport direction and slightly below. On the upper surface of the paper stacking tray 33, a plurality of sheets of paper 35 as sheet materials are stacked. A spring 37 is installed on the bottom wall of the paper stacking tray 33, and the paper stacking tray 33 positions the uppermost paper 35 on the paper transport path (sheet material transport path) by the elastic force of the spring 37. It is so energized.

  A separation pad 39 is movably provided at a position below the paper feed roller 31, that is, a position facing the paper feed roller 31 across the paper transport path. Further, the end of a spring 41 as an urging means is connected to the surface of the separation pad 39 opposite to the paper feed roller 31. As a result, the separation pad 39 is always biased toward the paper feed roller 31 by the elastic force (biasing force) of the spring 41.

  A paper feed roller pair 43 is provided on the downstream side of the paper feed roller 31. That is, the paper feed roller pair 43 is composed of a pair of rollers facing each other across the paper transport path. In the case of a roller pair, a pair of rollers facing each other across a paper conveyance path (sheet material conveyance path) is shown.

  The image forming unit 27 includes a cartridge 45, an optical unit 47, and a transfer roller 49. The cartridge 45 is disposed above the paper conveyance path, and its operation is controlled by the optical unit 49. The transfer roller 49 is disposed at a position facing the cartridge 47 across the paper conveyance path.

  A paper discharge mechanism (sheet material feeding mechanism) 53 is provided on the downstream side of the image forming unit 27 with the fixing unit 51 interposed therebetween. The paper discharge mechanism 53 according to the present embodiment includes a paper discharge roller pair 55, a conveyance guide 57, and a reverse roller pair 59. The paper discharge roller pair 55 receives the paper sent from the fixing unit 51. A paper discharge port 61 is provided on one downstream side of the paper discharge roller pair 55. A reverse roller pair 59 is disposed on the other downstream side of the paper discharge roller pair 55 via a conveyance guide 57. Further, a paper return roller pair 63 is provided so that the paper fed out of the reverse roller pair 59 is returned to the image forming unit 27.

  In addition, a power supply unit 65, an internal cooling fan 67, and the like are disposed in the housing 25 of the image forming apparatus 21.

  FIG. 2 schematically shows the paper discharge roller pair. The paper discharge roller pair 55 has three pairs of driving rollers 69 and driven rollers 71 in the present embodiment. The driving roller 69 and the driven roller 71 are disposed so as to face each other across a paper conveyance path (sheet material conveyance path) P indicated by a dotted line.

  The driving roller 69 and the driven roller 71 are supported by the supports 73 and 75 and are rotatably provided. The driving roller 69 is rotationally driven by driving means 76 such as a motor to which one end of the support 73 is connected. The driving roller 69 can be rotated in the forward rotation direction so that the paper is completely discharged through the paper discharge port 61, and can also be rotated in the reverse direction so that the paper can be sent back to the reverse roller pair 59. ing. That is, it is configured so that double-sided printing can be performed.

  On the other hand, the driven roller 71 is in contact with the paper that is moved by the driving force of the driving roller 69 during paper conveyance, and is rotated by the moving force transmitted from the paper. In the present embodiment, the driven roller 71 has a smaller diameter than the driving roller 69.

  Next, details of the driven roller 71 and its support 73 will be described with reference to FIGS. Each driven roller 71 has an elastic cylindrical body 77 fitted to the outer periphery of the support 73. The illustrated follower roller 71 includes a paper contact portion 111, a first support piece 112, a second support piece 113, and a through hole 115.

  The paper contact portion 111 and the first and second support pieces 112 and 113 are configured by members having elasticity. For the elastic member, a resin material such as natural rubber, synthetic rubber, low-hardness rubber, soft plastic, thermoplastic elastomer (TPE), or the like is preferably used.

  In the driven roller (hollow roller) 71, the paper contact portion 111 and the first and second support pieces 112 and 113 are formed of an elastic cylindrical body (hollow elastic body) 77 having a cavity 116 that is a hollow portion inside. Constitute.

  The paper contact portion 111 constitutes a cylindrical outer peripheral surface serving as a paper contact surface, and a tread pattern may be formed on the outer peripheral surface. For example, examples of the tread pattern include a wavy line shape, a lattice shape, a protrusion shape, and a shot blast pattern. Further, it may not be necessarily provided as long as an appropriate frictional force can be obtained by selecting a material for the paper contact portion 111.

  The first and second support pieces 112 and 113 are formed in a ring shape continuous in the circumferential direction on both sides of the paper contact portion 111 in the axial direction.

  More specifically, the first and second support pieces 112 and 113 are provided so as to face each other on opposite sides of the paper contact portion 111 with a distance D14 therebetween. The edges of the first and second support pieces 112, 113 have an arcuate cross section, and are provided continuously over the inner periphery of the through hole 115 that opens on both sides of the paper contact portion 111 in the axial direction. . The end edges of the first and second support pieces 112 and 113 having an arcuate cross section are increased in thickness so as to bulge inward toward the cavity 116. The edge of the first support piece 112 has a maximum thickness D12 having an arcuate cross section. The edge of the second support piece 113 has a maximum thickness D13 having an arcuate cross section.

  In the present specification, the “arc shape” having an arc shape in cross section is not necessarily limited to a part of the circumference of a perfect circle having a certain point.

  The through hole 115 passes through the axial centers of the first and second support pieces 112 and 113. The through hole 115 is continuous with the cavity 116. The through hole 115 has a maximum inner diameter dimension D15. D11 indicates the maximum outer diameter of the driven roller 71. Although not necessarily clear from the drawing, the maximum outer diameter D11 of the driven roller 71 is preferably about twice the maximum inner diameter D15 of the through hole 15.

  According to the above-described structure, the paper contact portion 111, the first support piece 112, and the second support piece 113 are configured by elastic members, so that they are deformed according to the pressing force from the paper and are wide It can be in pressure contact with the paper contact area.

  In addition, since the paper contact portion 111 and the first and second support pieces 112 and 113 have the cavities 116, by setting the dimensions of the cavities 116, the paper contact portion 111 and the first and second support pieces 112 and 113 are set. The thickness of the support pieces 112 and 113 is set. Therefore, the elasticity of the driven roller 71 can also be adjusted by setting the wall thickness, so that the paper contact area and the paper conveying force that are pressed against the paper can be adjusted as appropriate, and the paper can be fed reliably. Further, if the paper conveying force can be adjusted by setting the dimensions of the cavity 116, the driven roller 71 having various performances can be provided quickly and inexpensively.

  Since the paper contact portion 111 has a tread pattern for obtaining an appropriate friction force for paper feeding, when the driven roller 71 is pressed against the paper, the paper contact portion 111 can acquire an appropriate friction force and reliably carry the paper. .

  The through-hole 115 passes through the paper contact portion 111 and the axial centers of the first and second support pieces 112 and 113 and continues to the cavity 116. Accordingly, the support 73 can be guided into the driven roller 71 from the through hole 115.

  Subsequently, the support will be described. As shown mainly in FIG. 4, the support 73 includes a base portion 120. In the base portion 120, at least a pair of ring-shaped concave grooves facing each other with a space therebetween are formed, in this embodiment, three pairs (however, only the pair of concave grooves 121 and 122 are shown). A pair of concave grooves is assigned to one driven roller 71.

  Each of the concave grooves 121 and 122 has a circular arc shape in cross section and has an inner diameter dimension D21. The inner diameter dimension D21 is set in a range in which the first and second support pieces 112 and 113 can be fitted and held.

  The support 73 further includes a slit 126 formed on the outer peripheral surface of the base portion 120. At least one slit 126 is assigned to each driven roller 71. In the case where a plurality of slits are provided for one driven roller 71, it is preferable that the slits are arranged at equiangular intervals on the outer peripheral surface of the base portion 120. In FIG. 4, only one of the slits 126 is shown.

  Each slit 126 is provided so as to traverse the inside of the concave grooves 121 and 122 and the outer peripheral surface of the base portion 120 that defines the cavity 116, and to open to the outer peripheral surface of the base portion 120.

  Next, the structure which combined the driven roller 71 and the support body 73 is demonstrated. As shown mainly in FIG. 5, in the driven roller 71, the end edge of the first support piece 112 is combined so as to be fitted in close contact with the first concave groove 121, and the second support piece 113. These end edges are combined so as to be closely fitted in the second concave groove 122.

  Here, the inner diameter dimension D21 of the concave grooves 121 and 122 is preferably set to be equal to or smaller than the maximum thickness diameter dimensions D12 and D13 of the first and second support pieces 112 and 113. That is, as a preferable fitting relationship between them, the inner diameter dimension D21 of the female concave grooves 121, 122 is equal to or less than the maximum thickness D12, 13 of the first and second support pieces 112, 113 that are male. Is set to

  Further, the interval D22 between the adjacent concave grooves 121 and 122 is determined corresponding to the interval D14 between the first and second support pieces 112 and 113. That is, the interval D22 between the adjacent concave grooves 121 and 122 is preferably set to be approximately the same as the interval D14 between the first and second support pieces 112 and 113 that are adjacent to each other.

  A cavity 116 is widely formed between the driven roller 71 and the support 73. The inside of the cavity 116 communicates with the outside of the driven roller 71 through the slit 126.

  According to the structure described above, since the end edges of the first and second support pieces 112 and 113 and the concave grooves 121 and 122 are both arc-shaped in cross section, the first and second support pieces 112 and 113 have When each of the end edges and each of the concave grooves 121 and 122 are fitted in close contact with each other, a contact surface having an enlarged area is formed between them.

  The inner diameter D21 of the concave grooves 121, 122 is preferably set to be equal to or smaller than the maximum thickness diameter D12, D13 of the first and second support pieces 112, 113. Since the first and second support pieces 112 and 113 are made of elastic members, once they are fitted into the concave grooves 121 and 122, the first and second support pieces 112 and 113 have first elasticity due to the elasticity of the driven roller 71. And the end edges of the second support pieces 112 and 113 are elastically adhered to the inner contact surfaces of the concave grooves 121 and 122 in a compressed state. Therefore, the driven roller 71 and the support body 73 are well coupled, and it is possible to prevent the driven roller 71 from slipping in the rotational direction as well as preventing the positional deviation in the rotational axis direction.

  As described above, the driven roller 71 is stably attached to the support 73 using its elasticity. Therefore, the paper feeding device can be easily assembled without being fixed with an adhesive, screws or the like. In addition, since the driven roller 71 and the support body 73 do not have a complicated coupling structure, the manufacture is easy.

  Since the support 73 includes the slit 126, air inside the cavity 116 can be ventilated from the slit 126, so that the shape of the cavity 116 can be changed. Accordingly, it is possible to secure a wide contact area with respect to the paper and to obtain an appropriate pressure contact force and friction force corresponding to various thickness changes of the paper. That is, paper feeding can be performed reliably.

  Further, since the air inside the cavity 116 of the driven roller 71 can be ventilated from the slit 126, the cavity 116 is not sealed. Therefore, the air pressure applied from the cavity 116 to the driven roller 71 is maintained appropriately regardless of whether it is in contact with the sheet or not, and deterioration of the driven roller 71 due to long-time use can be minimized.

  Next, the drive roller will be described. As shown in FIG. 6, the drive roller (solid roller) 69 also has an elastic cylindrical body (solid elastic body) 79 fitted to the outer peripheral portion of the support body 75. The drive roller does not have a cavity as a hollow part between the support body 75 or a cavity as a hollow part narrower than the cavity 116 of the driven roller 71. In the illustrated embodiment, the drive roller 69 does not have a cavity between the support body 75.

  Next, the operation of the image forming apparatus configured as described above will be described mainly with reference to FIG. First, in a state of waiting for paper feeding, the paper feeding roller 31 is stopped, and the front end of several sheets of paper 35 is placed on the upstream side portion of the upper surface of the separation pad 39. At this time, since the upper surface of the separation pad 39 is inclined with respect to the stacking direction of the papers 35, the front end of the upper paper 35 is shifted to the front in the paper transport direction. Therefore, at the time of conveyance, there is a function of suppressing the multi-feeding in which a plurality of papers 35 are conveyed together in combination with the operation of a paper feed roller 31 described later.

  In the standby state, when a request for image formation is input from a customer, the driving force of a drive motor (not shown) is transmitted to the paper feed roller 31, and the paper feed roller 31 rotates as indicated by an arrow in the figure. . Further, the separation pad 39 is always biased toward the paper feed roller 31 by the elastic force of the spring 41. Therefore, the sheet 35 on the top of the separation pad 39 is fed by one sheet due to the interaction between the frictional force for conveying the paper by the rotation of the paper feed roller 31 and the frictional force functioning as the resistance of the separation pad 39. It is conveyed toward the roller pair 43.

  The conveyed paper 35 passes between the paper feed roller pair 43 and a desired image is formed in the image forming unit 27. Further, the image-formed paper 35 is sent to the paper discharge mechanism 53 through the fixing unit 51. More specifically, the paper 35 on which an image has been formed advances between the drive roller 69 and the driven roller 71 as the paper discharge roller pair 55 while being guided by the conveyance guide 57, and the drawing of the drive roller 69 and the driven roller 71 is shown in FIG. The sheet is discharged from the sheet discharge outlet 61 by the rotation in the direction of the solid solid arrow (forward rotation direction).

  When a request for double-sided printing is input from the customer, the paper 35 is partially exposed from the paper discharge port 61 by the rotation of the driving roller 69 and the driven roller 71 in the forward rotation direction, but is completely discharged. Instead, the drive means 76 reverses. That is, the drive roller 69 and the driven roller 71 rotate in the direction of the dotted line arrow (reverse direction) in the drawing, whereby the paper 35 is guided from the paper discharge port 61 to the backward conveyance guide 57 and reaches the reverse roller pair 59. .

  Further, the paper 35 passes between the reversing roller pair 59 and reaches the paper return roller pair 63, and is turned over so that the surface opposite to the image-formed surface faces as a surface for forming a new image. Then, it is conveyed to the entrance of the image forming unit 27. Thereafter, the paper is completely discharged from the paper discharge port 61 through image formation by the image forming unit 27, conveyance by the fixing unit 51, and rotation in the normal rotation direction of the driving roller 69 and the driven roller 71.

  Here, the following action is obtained in the driven roller 71 having the cavity 116. In the portion of the driven roller 71 opposite to the portion in contact with the paper, that is, the portion in which the internal space distance D of the cavity 116 is the maximum value, the paper contact surface 111 and the first and second support pieces 112 and 113 are provided. Since no pressing force is applied, the elastic shape of the driven roller 71 provides a stable shape.

  On the other hand, in the portion of the driven roller 71 that is in contact with the paper, that is, the portion showing the minimum value of the internal space distance of the cavity 116, the driven roller 71 is rotated by the paper contact portion 111 coming into contact with the paper. Friction is applied. As a result, the paper contact portion 111 and the first and second support pieces 112 and 113 are deformed by receiving a pressing force from the paper, and the air inside the cavity 116 is compressed and released to the outside through the slit 126. The When the air inside the cavity 116 is released to the outside, the air pressure of the driven roller 71 decreases, and further, the driven roller 71 continues to be deformed according to the elasticity of the driven roller 71, and the contact area of the paper contact portion 111 with respect to the paper is further increased Become wider.

  As described above, the driven roller 71 is made of an elastic member, so that the paper contact portion 111 is crushed deeply, so that the area in contact with the paper increases. Accordingly, the paper feeding is reliably performed.

  Further, the area in contact with the paper increases, and the frictional force per unit area on the contact surface of the paper contact portion 111 with the paper decreases. For this reason, the wear of the driven roller 71 is reduced. Therefore, even if it is used for a long time, the frictional force due to wear of the driven roller 71 does not decrease, and it is possible to prevent a paper feed failure.

  Furthermore, since the paper contact portion 111 is deeply crushed, it is possible to mitigate the reduction in frictional force that the driven roller 71 receives from the paper. For this reason, even if the elasticity of the driven roller 71 deteriorates with the passage of time, it is possible to prevent paper feeding failure.

  As described above, in the driven roller 71, the paper contact portion 111 is crushed deeply, the area in contact with the paper is increased, and the frictional force per unit area on the contact surface of the paper contact portion 111 with the paper is reduced. The paper does not peel off due to force. For this reason, paper dust is not generated and the surroundings are not soiled by paper dust.

  Since the driven roller 71 is made of an elastic member, it is crushed according to the thickness of the paper. For this reason, paper feeding can be performed regardless of the thickness of the paper.

  On the other hand, when the driven roller 71 that continues to rotate is separated from the contact surface with the paper, a restoring force is applied to the driven roller 71 due to its elasticity. When the driven roller 71 is restored to the shape in which the internal space distance D of the cavity 116 becomes the maximum value, air is sucked from the slit 126, so that it is easily restored to the original shape. Therefore, the paper can always be brought into contact with the paper in an optimum state and the paper can be reliably fed.

  Further, when the paper on which the image is formed is sandwiched and conveyed between the pair of rollers, as described above, the contact trace with the roller, that is, the roller trace may remain on the paper surface.

  However, in the present embodiment, one of the pair of rollers is a driving roller, the other is a driven roller, the driving roller is a solid roller without a cavity, and the driven roller is a hollow roller having a cavity, It is possible to prevent roller marks from remaining on the paper surface.

  Furthermore, when the hollow roller is simply used, there is a problem that the relationship between the rotation amount of the hollow roller and the paper conveyance distance does not always match because the degree of deformation of the hollow roller is larger than that of the solid roller. .

  However, in the present embodiment, one of the pair of rollers is a driving roller and the other is a driven roller, and the hollow roller is used as a driven roller instead of a driving roller. Can be earned. In particular, when performing double-sided printing with paper reversal, there is a paper reversal movement, so that it is effective to more reliably acquire the transport amount as designed.

  As described above, according to the present embodiment, it is possible to prevent the roller traces from remaining on the surface of the paper, and it is possible to more reliably acquire the transport amount as designed.

  Although the contents of the present invention have been specifically described with reference to the preferred embodiments, various modifications can be made by those skilled in the art based on the basic technical idea and teachings of the present invention. It is self-explanatory.

  As a modified form of the elastic cylindrical body in the driven roller, the configuration shown in FIG. 7 can be exemplified. The driven roller 271 has an elastic cylindrical body 277 fitted to the outer peripheral portion of the support body 73. The illustrated driven roller 271 includes a paper contact portion 211, a first support piece 212, a second support piece 213, and a through hole 215. The paper contact portion 211 and the first and second support pieces 212 and 213 constitute an elastic cylindrical body 277 having a cavity 216 that is a hollow portion inside. The through hole 215 passes through the axial centers of the first and second support pieces 212 and 213. The through hole 215 is continuous with the cavity 216.

  The first and second support pieces 212 and 213 are formed in a ring shape that is continuous in the circumferential direction on both sides of the paper contact portion 211 in the axial direction. Further, the end edges of the first and second support pieces 212 and 213 having an arcuate cross section are increased in thickness so as to bulge outward toward the opposite side of the cavity 216.

  According to the driven roller 271 having such a configuration, in addition to obtaining the effect of the driven roller 71 described above, the outer diameter of the cylindrical elastic body can be further reduced, and the driven roller itself can be reduced in size. . In addition, since heating is performed in the fixing unit 51 to fix the toner for image formation, a certain amount of space is usually provided between the fixing unit 51 and the discharge roller pair 55. Since the driven roller 271 can be downsized, the entire image forming apparatus 21 can be downsized.

  Further, the drive roller in the present invention is not limited to one having no hollow portion in a strict sense. In other words, if the driving roller has a hollow portion between the support and the hollow portion that is narrower than the driven roller, the driven hollow roller and the driving side are solid in a relative relationship. The combination with the roller is established, and the above-described operational effects can be obtained.

  Further, the sheet material feeding mechanism according to the present invention is not limited to the application to the paper discharge mechanism, but can also be applied to a paper feed mechanism or an intermediate transport mechanism that is not in the category of paper supply / discharge. is there.

  Moreover, the object conveyed by this invention should just be a sheet | seat material, and is not limited to paper. Furthermore, the image forming apparatus according to the present invention is not limited to a printer, and can be widely applied to apparatuses having a mechanism for conveying a sheet material so as to form a certain image on the sheet material, such as a copier or a FAX. Is possible.

1 is a diagram schematically illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing a pair of paper discharge rollers applied to the image forming apparatus of FIG. 1. It is a figure which shows the structure of the driven roller of the sheet | seat feed mechanism which concerns on this invention. It is a figure which shows the structure of the support body of the sheet material feeding mechanism which concerns on this invention. It is a figure which shows the combined state of a driven roller and a support body regarding the sheet material feeding mechanism which concerns on this invention. It is a figure which shows the structure of the drive roller of the sheet material feeding mechanism which concerns on this invention. It is a figure which shows the structure of a driven roller regarding another embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Image forming apparatus 27 Image forming part 29 Paper feed mechanism 53 Paper discharge mechanism 55 Paper discharge roller pair 61 Paper discharge port 69 Drive roller 71 Driven roller 73, 75 Support body 76 Drive means 116, 216 Cavity (hollow part)
120 Base part 121, 122 Concave groove 126 Slit

Claims (4)

A driving roller rotated by driving means;
A driven roller that opposes the drive roller via a sheet material conveyance path and is rotated by a force transmitted from the sheet material;
A support for supporting each of the driving roller and the driven roller,
Each of the driving roller and the driven roller has an elastic cylindrical body fitted to the outer periphery of the support,
The driven roller has a hollow portion between the support body,
The drive roller does not have a hollow portion between the support body or a hollow portion narrower than the driven roller,
A sheet material feeding mechanism characterized by that. The support that supports the driven roller includes a base portion and a slit,
The base portion has at least two or more ring-shaped concave grooves facing each other at an interval,
The slit is provided so as to traverse the inside of the concave groove and open to the outer peripheral surface of the base portion,
The air inside the hollow part can be ventilated from the slit,
The elastic cylindrical body constituting the driven roller is combined with the support body so that both side edges thereof are fitted into the corresponding concave grooves,
The sheet material feeding mechanism according to claim 1. An image forming unit;
A paper feed mechanism provided upstream thereof;
A paper discharge mechanism provided on the downstream side of the image forming unit,
The sheet discharge mechanism includes the sheet material feeding mechanism according to claim 1 or 2,
The paper discharge roller pair in the paper discharge mechanism is the drive roller and the driven roller.
An image forming apparatus. A fixing roller pair is provided on the upstream side of the paper discharge roller pair, and a reverse roller pair and a paper discharge port are provided on the downstream side of the paper discharge roller pair.
The drive roller in the paper discharge roller pair is rotatable in the forward rotation direction so that the sheet material is completely discharged through the paper discharge port, and is capable of sending the sheet material back to the reverse roller pair. It can also rotate in the reverse direction,
The image forming apparatus according to claim 3.

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