JP2010116228A - Sheet conveying device, and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continuously and smoothly feed highly flexible recording sheets such as a cardboard without a jam when the recording sheets are loaded on a manual feed tray in a stacked state. <P>SOLUTION: A recording sheet loaded on a manual feed tray 14b is formed in a curved state by a manual feed side first lower guide 14h and a manual feed side second lower guide 14k on a manual feed side conveying path 14s, and its fore end is guided by a flexible guide 12k so as to be directed to a conveying nip of a first conveying unit 13. When flexibility of the recording sheet is increased, the flexible guide 12k is bent along the conveying direction by the manual feed side conveying path, and a fore end of the recording sheet is abutted on an outer circumferential surface of a first conveying driving roller 13a, and introduced in the conveying nip by the rotation of the first conveying driving roller 13a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sheet conveying mechanism that supplies an image processing unit that forms an image on a recording sheet such as recording paper, and an image forming apparatus including the sheet conveying mechanism.

  In an image forming apparatus such as a copying machine, a printer, a facsimile machine, or a combination of these, a toner image corresponding to image data is transferred to a recording sheet such as recording paper supplied from a sheet supply apparatus in an image processing unit. It is configured to fix. A sheet conveying mechanism of such an image forming apparatus is usually provided with a plurality of types of paper feed cassettes each containing recording sheets of different sizes, and a recording sheet of any size selected by the user A manual feed unit is also provided so that the image can be manually fed to the image processing section. Each sheet feeding cassette provided in the sheet conveying mechanism is disposed below the image processing unit in order to reduce the installation space of the image forming apparatus. It can be pulled out. The recording sheets in each sheet cassette are conveyed one by one to the upper image process unit by a sheet feeding unit on the image forming apparatus main body side including sheet feeding rollers.

  In such a sheet conveying mechanism, in order to convey a recording sheet in a paper feeding cassette disposed below the image processing unit to an upper image processing unit, the sheet is fed obliquely upward from the paper feeding cassette. The recording sheet needs to be greatly curved so as to go further upward. In Patent Documents 1 to 3, the leading end portion of a recording sheet fed from a paper feed tray (paper feed cassette) is brought into contact with a transport belt that circulates upward, whereby the guide direction is sequentially raised upward. A configuration to be directed is disclosed. With such a configuration, the recording sheet can be smoothly curved and conveyed upward. However, in the configuration in which the leading end portion of the recording sheet is guided upward by the conveyor belt that moves around, a large installation space is required for installing the conveyor belt, which may increase the size of the entire image forming apparatus. In addition, many parts are required to move the conveyor belt around, which may impair economic efficiency.

In Patent Document 4, a first paper feeding unit that transports a recording sheet stored in a paper feeding cassette and a manual feeding unit that manually feeds a recording sheet selected by a user are disposed opposite to each other in the horizontal direction. In the image forming apparatus provided with the transport unit for transporting the recording sheet transported from the first paper feed unit and the manual feed unit to the upper image process unit, a second paper feed unit is further provided below the first paper feed unit. A configuration is disclosed in which a recording sheet that is arranged and transported from the second paper feed unit is transported to the transport unit via a vertical transport path formed between the first paper feed unit and the manual feed unit. With this configuration, the first paper feed unit and the manual feed unit, the transport unit and the second paper feed unit can be arranged in close proximity to each other, and the image forming apparatus can be downsized. There is an advantage that can be.
JP 2008-24497 A JP 2008-120560 A JP 2008-110875 A JP 2008-137748 A

  In the image forming apparatus disclosed in Patent Document 4, the side opposite to the paper feeding side (the paper feeding cassette side) becomes higher in order to prevent the recording sheet placed on the manual feeding tray from dropping from the manual feeding tray. An inclined sheet placement table is provided, and adjacent to the lower end of the sheet feeding side of the sheet placement table, an end of the recording sheet on the feeding side is provided on a pickup roller provided above. A manual sheet feed table that biases the sheet so as to come into pressure contact is provided. The recording sheet placed on the manual feed stand and the sheet placement stand is fed to the feed nip between the feed roller and the separation roller pressed against each other by the rotation of the pickup roller. One separated recording sheet is conveyed obliquely upward by a paper feed guide. The recording sheet guided by the paper feed guide is guided further upward by the guide film. Above the guide film, a conveyance path formed in the vertical direction by a pair of left and right guide members is provided, and a recording sheet is formed in a conveyance nip between the pair of left and right conveyance rollers pressed against each other by the conveyance path Will be guided.

The recording sheet fed from the manual feed tray is curved from the guide film to the sheet placement table of the manual feed tray. In this case, the front end portion of the recording sheet is in a substantially vertical state by the guide film and the pair of left and right guide members, whereas the rear end portion is inclined along the sheet mounting table inclined obliquely upward. The recording sheet is in a curved state with a small curvature radius. In such a curved state, when the trailing edge of the recording sheet passes between the manual feed table and the manual pickup roller, the stiffness of the recording sheet (resistance when a bending force is applied to the recording sheet) Therefore, the rear end portion of the recording sheet may strongly push down the manual sheet feeding table biased upward. When the force acting on the manual sheet feeding table by the trailing edge of the recording sheet is large, the manual sheet feeding table is largely pushed downward, so that the next of the first recording sheet among the stacked recording sheets is The end of the second recording sheet conveyed to the sheet feeding direction is not pressed against the pickup roller, and the second recording sheet may not be fed out by the pickup roller. If the recording sheet placed on the manual feed tray is thin paper that is relatively weak, the second recording sheet is Although the probability of not being fed out is low, for example, in the case of thick paper having a weight per unit area (basis weight) of 256 g / m ² or more, there is a possibility that the manual paper feeding table may be pushed down greatly depending on the strength of the waist. The second recording sheet cannot be fed out, and as a result, there is a high possibility of a paper jam (JAM).

  The present invention has been made in view of such a conventional problem, and the object thereof is to record each recording sheet even when a stiff recording sheet such as cardboard is placed in a stacked state on a manual feed tray. An object of the present invention is to provide a sheet conveying mechanism capable of conveying a sheet continuously and smoothly without causing a paper jam and an image forming apparatus including the sheet conveying mechanism.

  In order to achieve the above object, a sheet transport mechanism according to the present invention feeds a recording sheet from a paper feeding cassette and transports the fed recording sheet while curving it so as to face obliquely upward, A manual feed tray that is arranged so as to face the paper feed cassette and is inclined so that the paper feed direction side is lowered, and a paper feed direction side of the recording sheet placed on the manual feed tray A manual sheet feeding table that urges the end of the recording sheet upward, and a pressure-contacting end of the recording sheet placed on the manual sheet feeding table on the sheet feeding direction side so that the recording sheet is placed in the manual sheet feeding table. A manual feed side conveying means for conveying the recording sheet fed by the pickup roller in a curved state so as to face obliquely upward, and the cassette side carrying And a flexible guide for guiding each recording sheet conveyed obliquely upward by the manual-feed-side conveying means and a pair of left and right conveying rollers that are in pressure contact with each other. Each recording sheet conveyed upward by the sexual guide has a conveyance unit disposed so as to pass through a conveyance nip between the pair of conveyance rollers, and is stiff by the manual-side conveyance means. When the recording sheet is conveyed, the flexible guide is bent by the recording sheet, and the curved state of the recording sheet is reduced as compared with the case where the recording sheet having a low waist is conveyed.

  An image forming apparatus according to the present invention includes the sheet conveying mechanism and an image processing unit that forms a toner image on a recording sheet conveyed by the sheet conveying mechanism.

  In the sheet transport mechanism of the present invention, the recording sheet placed on the manual feed tray is transported in a curved state by the manual feed side transport means, and is guided by the flexible guide so that the leading end is directed to the transport nip. However, in the case of a recording sheet with a strong waist, the flexible guide is bent so as to be in a state along the conveyance direction by the manual-side conveyance means, so that it is conveyed in a curved state as compared with a recording sheet with a low waist. It is alleviated that the recording sheet to be printed is further curved by the flexible guide. As a result, it is possible to prevent the trailing edge of the recording sheet having a strong stiffness from pushing down the manual sheet feeding base strongly downward, and it is possible to prevent the occurrence of a paper jam in which the recording sheet is not fed.

  Preferably, the pair of conveyance rollers includes a first conveyance roller disposed in front of the recording sheet conveyance direction by the manual-side conveyance unit, and a second conveyance roller disposed in front of the recording sheet conveyance direction by the cassette-side conveyance unit. A conveyance roller, wherein a conveyance direction of the recording sheet by the manual-side conveyance unit is substantially parallel to a diameter direction of the first conveyance roller.

Preferably, the first conveying roller is disposed on both sides in the width direction of the recording sheet with respect to a recording sheet having a maximum length in the width direction orthogonal to the conveying direction in the recording sheet that can pass through the conveying nip. The recording sheet is characterized in that it is slightly shorter than the length in the width direction of the recording sheet so as to abut over the vicinity of each side edge.
Preferably, the second conveying roller has an axial length shorter than that of the first roller, and is in pressure contact with a central portion in the axial direction of the first roller.

Preferably, the friction coefficient of the outer peripheral surface of the first transport roller is higher than the friction coefficient of the outer peripheral surface of the second transport roller.
Preferably, the recording sheet conveyed toward the first conveyance roller is restricted from entering the opposite side of the conveyance nip with respect to the first conveyance roller below the first conveyance roller. In addition, a restriction guide is provided for guiding toward the outer peripheral surface of the first conveying roller.

Preferably, the cassette-side transporting unit and the cassette-side separating member are pressed against each other in the vertical direction so as to separate and transport the recording sheets fed from the sheet feeding cassette one by one. Is provided.
Preferably, the regulation guide is opposite to the conveyance path with respect to a common tangent line between the cassette-side sheet feeding roller and the first conveyance roller located on the recording sheet conveyance path side by the cassette-side sheet feeding roller. It is arranged on the side.

Preferably, a second sheet feeding cassette is provided below the sheet feeding cassette, and a recording sheet fed from the second sheet feeding cassette is fed between the cassette side conveying unit and the manual sheet conveying unit. The sheet is guided by the flexible guide through the vertical conveyance path provided in the vertical direction therebetween, and is conveyed toward the conveyance nip.
Preferably, the waist of the recording sheet becomes stronger as the weight per unit area of the recording sheet increases.

  FIG. 1 is a schematic front view showing an internal configuration of a tandem type color digital copying machine as an example of an image forming apparatus provided with a sheet conveying mechanism according to the present invention. As shown in FIG. 1, the copying machine includes a sheet conveying mechanism A provided at the lowermost part, an image processing unit B provided on the sheet conveying mechanism A, and an image reading unit provided on the image processing unit B. When a print execution instruction (print job) is received from a terminal device connected to a network (for example, an in-house LAN) or an operation panel, the image data from the terminal device is converted according to the instruction. Based on the image data of the original read by the image reading unit C, a toner image is formed on the recording sheet supplied from the sheet conveying mechanism A in the image processing unit B.

  The image processing unit B is arranged in order from the upstream side along the circumferential movement direction of the intermediate transfer belt 51 under the intermediate transfer belt 51, and the intermediate transfer belt 51 that rotates in the direction indicated by the arrow N. The image forming units 52Y, 52M, 52C, and 52K and the image forming units 52Y, 52M, 52C, and 52K are disposed below the image forming units 52Y, 52M, 52C, and 52K to irradiate the laser beams L, respectively. The exposure apparatus 53 is provided. The intermediate transfer belt 51 is wound around a driven roller 54 disposed close to the image forming unit 52Y and a driving roller 55 disposed close to the image forming unit 52K. The driving roller 55 is not shown. By being rotationally driven by the motor, it moves around in the direction indicated by the arrow N. The intermediate transfer belt 51 has conductivity.

  The image forming unit 52Y disposed on the upstream side in the moving direction of the intermediate transfer belt 51 includes a photosensitive drum 56Y, and forms a toner image on the photosensitive drum 56Y by a known electrophotographic method. That is, an electrostatic latent image is formed on the surface of the photosensitive drum 56Y by irradiating the photosensitive drum 56Y charged by the charger with the laser beam L from the exposure device 53, and the electrostatic latent image is formed. Is developed with yellow (Y) toner by the developing device, thereby forming a Y toner image.

The other image forming units 56M, 56C, and 56K have the same configuration as that of the image forming unit 56Y. Magenta (M) is formed on the photosensitive drums 56M, 56C, and 56K through charging, exposure, and development processes. , Cyan (C), and black (K) toner images are formed.
In the copying machine according to the present embodiment, a monochrome mode in which a monochrome image is formed using toner of one color (for example, K color), and a color in which a color image is formed using toners of four colors Y, M, C, and K. It is possible to switch between modes. In the image forming operation in the color mode, the image forming units 52Y, 52M, 52C, and 52K are formed on the outer peripheral surfaces of the photosensitive drums 56Y, 56M, 56C, and 56K that are rotationally driven at a predetermined peripheral speed. The Y, M, C, and K color toner images are transferred onto the same area of the intermediate transfer belt 51 in an overlapping manner. In the case of an image forming operation in the monochrome mode, a toner image formed by one selected image forming unit is transferred onto a predetermined area on the intermediate transfer belt 51. A secondary transfer roller 58 is disposed so as to face the drive roller 55 that drives the intermediate transfer belt 51 so that the intermediate transfer belt 51 is interposed between the secondary transfer roller 58 and the drive roller 55. A transfer nip N1 that forms a secondary transfer portion that transfers a toner image onto a recording sheet is formed between the circumferential transfer area of the intermediate transfer belt 51 along.

Above the intermediate transfer belt 51, hoppers 57Y, 57M, 57C, and 57K that store toner of each color of Y, M, C, and K are provided, and are accommodated in the hoppers 57Y, 57M, 57C, and 57K, respectively. The toner of each color is supplied to the developing devices of the image forming units 52Y, 52M, 52C, and 52K.
A sheet conveying mechanism A provided below the image processing unit B includes a first paper feeding unit 10 disposed below the exposure device 53 and a second paper feeding disposed below the first paper feeding unit 10. The paper feeding unit 20 includes a third paper feeding unit 30 and a fourth paper feeding unit 40 that are arranged further below the second paper feeding unit 20. From each of the first to fourth paper feeding units 10 to 40, recording sheets are conveyed one by one toward the image processing unit B, and intermediate transfer in the image processing unit B is performed at a predetermined timing by a pair of registration rollers 66. It is conveyed to a transfer nip N1 between the belt 51 and the secondary transfer roller 58. Then, while the recording sheet passes through the transfer nip N1, the toner image transferred onto the intermediate transfer belt 51 is secondarily transferred to the recording sheet by the secondary transfer roller 58. The recording sheet that has passed through the transfer nip N1 is supplied to a fixing unit 59 provided above the transfer nip N1.

  The fixing unit 59 includes, for example, a heating roller 59a and a pressure roller 59b that are pressed against each other, and a fixing nip N2 is formed therebetween. The toner image transferred to the recording sheet is heat-fixed on the recording sheet by being heated and pressurized while the recording sheet passes through the fixing nip N2. A paper discharge tray 61 is provided on each of the hoppers 57Y, 57M, 57C, and 57K provided in the image processing section B, and an appropriate space is provided above the paper discharge tray 61. The heat-fixed recording sheet is discharged onto the paper discharge tray 61 by the paper discharge roller pair 62.

  Note that, above the paper discharge tray 61, the recording sheet is switched back during double-sided copying in which a toner image is formed on the other side (back side) of the recording sheet on which one side (front side) is formed. A guide 64 is provided for use as an auxiliary. At the time of double-sided copying, the recording sheet on which the toner image is thermally fixed in the fixing unit 59 is conveyed to a reversing roller pair 65 provided above the paper discharge roller pair 62 and is sent onto the guide 64 by the reversing roller pair 65. Then, the leading end of the recording sheet is guided on the guide 64. The reverse roller pair 65 is switched to reverse rotation immediately before the trailing edge of the recording sheet passes. As a result, the seat is switched back and sent to the circulation path 63. The circulation path 63 is a path for circulating the switched back recording sheet to the transfer nip N1 so as to reverse the front and back, and is provided so as to pass the side of the fixing unit 59 along the vertical direction. Yes. The recording sheet sent to the guide 64 is conveyed to the pair of registration rollers 66 with the front and back being reversed.

  The first paper feed unit 10 provided on the upper part of the sheet transport mechanism A includes a first paper feed cassette 11 mounted in a substantially horizontal state in the apparatus main body on the lower side of the exposure device 53, and a first paper feed cassette. A first sheet feeding unit 12 that feeds recording sheets stored in the sheet 11 one by one, and a first sheet that conveys a recording sheet fed from the first sheet feeding unit 12 toward the upper image processing unit B. A transport unit 13 and a manual feed unit 14 for manually feeding a recording sheet to the first transport unit 13 from the outside of the apparatus main body are provided. The first paper feed cassette 11 is pulled out from the front side (front side) of the apparatus main body toward the front, thereby being removed from the apparatus main body in which the image processing unit B and the image reading unit C are provided, and removed from the apparatus main body. The first paper feeding cassette 11 is inserted from the front side to the back side (back side) of the apparatus main body so as to be attached to the apparatus main body. The other paper feed cassettes have the same configuration. In the following, the right side and the left side of the first paper feed cassette 11 in the direction of insertion with respect to the apparatus main body are simply referred to as “right side” and “left side”, respectively.

In the apparatus main body, a first paper supply unit 12 is arranged from above the right end of the first paper supply cassette 11 mounted on the apparatus main body to the right side, and recording in the first paper supply cassette 11 is performed. The sheets are conveyed one by one by the first sheet feeding unit 12 toward the first conveying unit 13 disposed obliquely above and to the right of the first sheet feeding unit 12.
The second paper feed unit 20 provided below the first paper feed unit 10 includes a second paper feed cassette 21 mounted in the apparatus main body below the first paper feed cassette 11 and a second paper feed. In order to feed the recording sheets stored in the cassette 21 one by one, a second paper feed unit 22 provided from the upper right end of the second paper feed cassette 21 to the right side, and a second paper feed unit 22 is provided with a second transport unit 23 that transports the recording sheet fed out from the head 22 toward the first transport unit 13 in the upper first paper feed unit 10.

  Below the second paper feed unit 20, a third paper feed unit 30 and a fourth paper feed unit 40 arranged side by side on the right side and the left side are provided. The third paper feeding unit 30 arranged on the right side is accommodated in the third paper feeding cassette 31 and the third paper feeding cassette 31 detachably arranged on the right side below the second paper feeding cassette 21. In order to feed the recording sheets one by one, a third paper feeding unit 32 provided on the upper right side of the third paper feeding cassette 31 and a recording sheet fed from the third paper feeding unit 32 are fed to the upper second paper feeding. And a third transport unit 33 that transports toward the second transport unit 23 in the unit 20. The fourth paper feed unit 40 disposed on the left side of the third paper feed cassette 31 includes a fourth paper feed cassette 41 disposed on the left side of the third paper feed cassette 31 in the apparatus main body, and a fourth paper feed cassette 41. In order to feed out the recording sheets stored in the sheet one by one, the fourth sheet feeding unit 42 provided on the upper right side of the fourth sheet feeding cassette 41 and the recording sheet fed out from the fourth sheet feeding unit 42 A fourth conveying unit 43 that conveys the upper area of the three sheet feeding cassettes 31 toward the right side; and a second conveying unit 23 in the upper second sheet feeding unit 20 that conveys the recording sheet conveyed by the fourth conveying unit 43. And a fifth transport unit 44 for transporting toward the head.

  FIG. 2 is a cross-sectional view illustrating a specific configuration of the first sheet feeding unit 10 disposed on the upper portion of the sheet conveying mechanism A. Inside the first paper feed cassette 11, there is provided a cassette paper feed base 11a on which recording sheets of a predetermined size are stacked. In the cassette sheet feed stand 11a, the right end (the end on the sheet feed side) of the first sheet feed cassette 11 is biased upward, and therefore the right end on the right sheet feed side is positioned upward. It is in an inclined state.

  The first paper feed unit 12 has a cassette side pickup roller 12a with which the end of the uppermost recording sheet placed on the cassette paper feed base 11a is pressed against, and the cassette side pickup roller 12a. Is rotated, the recording sheet pressed against the cassette-side pickup roller 12a is fed out from the first paper feed cassette 11 and supplied to the cassette-side conveyance path 12m. In the cassette-side transport path 12m, there are a cassette-side sheet feed roller 12b disposed on the right side of the cassette-side pickup roller 12a, and a cassette-side separation roller 12c that comes into pressure contact with the cassette-side sheet feed roller 12b from below. A cassette-side paper feed nip is formed between the cassette-side paper feed roller 12b and the cassette-side separation roller 12c. The cassette side pickup roller 12a, the cassette side paper feed roller 12b, and the cassette side separation roller 12c are attached to the apparatus main body. The recording sheet fed from the first paper feed cassette 11 by the cassette side pickup roller 12a is introduced into the cassette side conveyance path 12m, and the cassette side paper feed between the cassette side paper feed roller 12b and the cassette side separation roller 12c. One recording sheet separated at the nip is conveyed to the conveyance unit 13 through the cassette-side conveyance path 12m.

  FIG. 3 is an enlarged cross-sectional view showing the cassette-side transport path 12m and its peripheral portion. As shown in FIG. 3, on the downstream side (right side) of the cassette side paper feed path 12m in the cassette side paper feed nip in the recording sheet conveyance direction, one recording sheet passing between them is guided obliquely upward to the right. A cassette-side first paper feed guide 12f is provided. The cassette-side first paper feed guide 12f is in contact with the leading edge of one recording sheet that has passed through the cassette-side paper feeding nip, so that the leading edge is guided obliquely upward to the right. In contrast, a guide surface of the recording sheet inclined at an inclination angle of about 26 ° is provided. On the right side of the cassette-side first paper feed guide 12f, a first vertical transport path 15 is formed through which a recording sheet transported upward from the second paper feed section 20 disposed on the lower side passes. A cassette-side transport guide 12d is provided in a substantially vertical state. On the right side of the cassette-side conveyance guide 12d, a manual feed unit 14 is provided in the horizontal direction facing the first paper feed unit 12, and this manual-feed unit 14 faces the cassette-side conveyance guide 12d. By doing so, the manual feed side conveyance guide 14c forming the first vertical conveyance path 15 is provided in a substantially vertical state. The lower end portions of the cassette-side conveyance guide 12d and the manual-side conveyance guide 14c are sequentially separated toward the lower side so that the recording sheet conveyed from the lower side can be easily introduced into the first vertical conveyance path 15. Are inclined in opposite directions.

  At the upper end of the cassette-side conveyance guide 12d, a cassette-side second paper feed guide that guides the recording sheet guided by the cassette-side first paper feed guide 12f through the cassette-side paper feed nip further upward. 12h is formed integrally with the cassette-side transport guide 12d. The cassette-side second paper feed guide 12h has a recording sheet guide surface inclined from the upper end of the cassette-side transport guide 12d at an angle of about 30 ° (40 ° with respect to the horizontal line) with respect to the cassette-side transport guide 12d. Is provided. The guide surface of the recording sheet of the cassette-side second sheet feeding guide 12h is guided further upward by contacting the leading end of the recording sheet guided by the cassette-side first sheet feeding guide 12f. Thus, the inclination angle with respect to the horizontal line is larger than the guide surface of the recording sheet of the cassette-side first paper feed guide 12f.

  A film-shaped flexible guide 12k is attached to the upper end portion of the cassette side conveyance guide 12d, which is the upper end portion of the cassette side conveyance path 12m, so as to extend upward along the cassette side conveyance guide 12d. . The flexible guide 12k is made of, for example, a flexible PET film (trade name “Mylar”, manufactured by Teijin DuPont Films Ltd.), and the width direction (perpendicular to the paper surface) perpendicular to the recording sheet conveyance direction. And is attached in a state of being slightly inclined to the upper right with respect to the vertical direction.

  The cassette-side conveyance guide 12d having the flexible guide 12k attached to the upper end thereof is rotated at an upper end thereof obliquely downward to the right by a first support pin 12e provided at a lower portion of the first paper feed unit 12. As will be described later, with the manual feed unit 14 turned away from the first paper feed unit 12, the upper end is rotated obliquely downward to the right. By being moved, as shown in FIG. 4, the cassette-side paper feed roller 12b and the cassette-side separation roller 12c are opened to the outside of the apparatus main body. As a result, the cassette-side sheet feeding nip between the cassette-side sheet feeding roller 12b and the cassette-side separating roller 12c is opened to the outside, and the recording sheet is jammed in the cassette-side sheet feeding nip (JAM). The recording sheet can be easily removed.

  As shown in FIG. 3, above the cassette side conveyance guide 12d, the recording sheet conveyed upward in the cassette side conveyance path 12m and the first vertical conveyance path 15 are conveyed upward. And a recording sheet manually fed from the manual feeding unit 14 are further provided with a first transport unit 13 for transporting the recording sheet to the upper image processing section B. The first transport unit 13 includes a first transport drive roller 13a disposed on the left side above the first vertical transport path 15 and a first transport driven roller 13b disposed on the right side of the first transport drive roller 13a. ing. The first transport driving roller 13a and the first transport driven roller 13b are pressed against each other to form a transport nip therebetween. The outer peripheral surfaces of the first transport driving roller 13a and the first transport driven roller 13b have different friction coefficients, and the friction coefficient of the outer peripheral surface of the first transport driving roller 13a is the friction coefficient of the outer peripheral surface of the first transport driven roller 13b. Higher than. As shown in FIG. 5, when the length in the width direction orthogonal to the passing direction of the recording sheet passing through the transport nip is maximum, the first transport driving roller 13a is on both sides in the width direction of the recording sheet. It is slightly shorter than the length in the width direction of the recording sheet so as to be in contact with substantially the entire length in the width direction except for the edge portion. On the other hand, as shown in FIG. 6, the first transport driven roller 13b has an axial length shorter than that of the first transport drive roller 13a and over a predetermined length facing the central portion in the axial direction. It is in pressure contact only with the central portion of the first conveyance drive roller 13a so as to contact the recording sheet.

  As shown in FIG. 3, the 1st conveyance driven roller 13b is integrally attached with the said casing 13g in the casing 13g which covers the upper direction and the right side. The casing 13g is rotatably supported with respect to the apparatus main body by a third support pin 13c provided on the upper right side of the first transport driven roller 13b. The lower part of the side surface that is substantially vertical on the right side of the casing 13g is pressed leftward by a pressing member 14n provided in the manual feed unit 14, and the casing 13g is pressed by the pressing member 14n. Thus, the first conveyance driven roller 13b is pressed against the first conveyance driving roller 13a, and a conveyance nip is formed between them. The first transport driving roller 13a is rotationally driven by a motor (not shown), and the first transport driven roller 13b is pressed against the first transport driving roller 13a to rotate following the first transport driving roller 13a. When the pressing state of the casing 13g by the pressing member 14n of the manual feed unit 14 is released, the casing 13g causes the first transport driven roller 13b to contact the first transport driving roller 13a around the third support pin 13c by its own weight. The lower end is rotated to the left so as to release the pressure contact state. Thereby, the pressure contact state in the conveyance nip between the first conveyance driving roller 13a and the first conveyance driven roller 13b is released, and the recording sheet jammed in the conveyance nip can be easily removed from the lower side.

  The first transport driving roller 13a is disposed diagonally to the upper right of the upper cassette-side paper feed roller 12b provided in the cassette-side transport path 12m, and is provided at the upper end of the cassette-side transport path 12m. The second side paper feed guide 12h guides the recording sheet conveyed along the cassette side conveyance path 12m toward the first conveyance driven roller 13b. Below the first conveyance drive roller 13a, the left side (the cassette-side conveyance path 12m and the cassette-side conveyance path 12m) is located on the right side (the cassette-side conveyance path 12m side) of the first conveyance drive roller 13a and the cassette-side paper feed roller 12b. On the opposite side, a regulation guide 13e is provided that extends obliquely downward to the left at an inclination angle of 54 ° with respect to the horizontal line, for example, from a position immediately below the outer peripheral surface of the first transport driving roller 13a. ing. The lower end of the regulation guide 13e is separated from the common tangent L by about 4.3 mm, for example. The restriction guide 13e restricts the leading end of the recording sheet guided to the conveyance nip by the flexible guide 12k from entering the left side opposite to the conveyance nip with respect to the first conveyance drive roller 13a. In addition, the guide is directed toward the first transport drive roller 13a, and the high friction coefficient of the first transport drive roller 13a is obtained when the leading edge of the recording sheet comes into contact with the outer peripheral surface of the first transport drive roller 13a. It moves together with the outer peripheral surface, and is introduced into the conveyance nip.

The upper end portion of the flexible guide 12k extending upward from the upper end portion of the cassette-side conveyance guide 12d reaches a position close to the conveyance nip between the first conveyance driving roller 13a and the first conveyance driven roller 13b. It extends, and is bent toward the first conveyance driven roller 13b side when a recording sheet conveyed through the cassette-side conveyance path 12m contacts.
Below the first transport driven roller 13b, a third paper feed guide for guiding the recording sheet transported from the manual feed unit 14 to the transport nip between the first transport drive roller 13a and the first transport driven roller 13b. 13d is provided. The third paper feed guide 13d is formed in a U-shaped cross section that is open upward, and the left side surface portion extends in an inclined state from the lower side of the transport nip toward the lower right side, The left side surface part is connected to the bottom part in a substantially horizontal state via an arcuate curved part. The side surface portion on the right side of the third paper feed guide 13d extends upward from the bottom surface portion that is substantially horizontal, and the upper end portion thereof is close to the outer peripheral surface of the first transport driven roller 13b. The upper end portion of the flexible guide 12k described above is close to the upper end portion of the left side surface portion of the third paper feed guide 13d.

  As shown in FIG. 2, the manual feed unit 14 provided facing the right side of the cassette-side transport guide 12 d in the first paper feed unit 12 faces the first paper feed unit 12 with the first vertical transport path 15 interposed therebetween. A manual feed unit main body 14a, and a manual feed tray 14b supported by the manual feed unit main body 14a so as to extend rightward from the manual feed unit main body 14a. As shown in FIG. 7, the manual feed unit main body 14 a is arranged in a horizontal state from the front side to the back side of the apparatus main body, and a rear side housing frame ( (Not shown) so as to be able to rotate while maintaining a horizontal state around the vertical axis VL. The manual feed unit main body 14a is rotated about the vertical axis VL so as to be in a state of facing the first paper feed unit 12 and in a state of being separated from the first paper feed unit 12 in a horizontal state. By rotating the manual feed unit main body 14a away from the first paper feed unit 12, as shown in FIG. 7, a cassette-side transport guide 12d provided in a substantially vertical state on the first paper feed unit 12 is provided. Is exposed to the outside of the device body. As described above, the manual feed unit main body 14a has the first vertical transport path 15 between the manual feed unit main body 14a and the cassette-side transport guide 12d when the manual feed unit main body 14a faces the first paper feed unit 12. The manual-feed-side conveyance guide 14c that forms the shape is provided in a substantially vertical state.

  The manual feed tray 14b is provided to manually feed a recording sheet of an arbitrary size selected by the user to the image processing unit B, and has a right side position close to the manual feed separation roller 14g as a fulcrum ( (Not shown) is supported so as to be rotatable in a substantially horizontal state and a substantially vertical state (see FIG. 7) along the right side surface of the apparatus main body. As shown in FIG. 2, at the end of the manual feed tray 14b on the paper feed side (left side), the end (front end) on the paper feed cassette side (paper feed side) of the loaded recording sheet faces upward. A manual sheet feed table 14d is provided, and a sheet placement unit 14j is provided adjacent to the right side of the manual sheet feed table 14d. The sheet placing portion 14j is inclined at an angle of about 10 ° obliquely upward to the right with respect to the horizontal state, with the manual feed table 14d side as the lower side so that the placed recording sheet does not fall. A manual pick-up roller 14e is disposed above the manual sheet feed table 14d, and the leading end of the recording sheet placed on the manual sheet feed sheet 14d and biased upward is placed on the manual feed unit main body 14a. It is brought into pressure contact with the provided manual pickup roller 14e. The manual pick-up roller 14e is adapted to feed the pressure-contacted recording sheet from the manual feed base paper feed 14d by its rotation.

  The manual feed unit main body 14 a is provided with a manual feed path 14 s for carrying the recording sheet fed from the manual feed tray 14 b toward the first transport unit 13. The manual feed path 14s is provided with an upper and lower manual feed roller 14f and a manual separation roller 14g that form a manual feed nip by being pressed against each other.

  When the recording sheet is placed on the manual feed tray 14d and the sheet placement portion 14j in the manual feed tray 14b, the recording sheet is opposite to the feeding side from the manual feed tray 14b due to the inclination of the sheet placement portion 14j. The end of the sheet feeding side is pressed against the manual pickup roller 14e by the manual sheet feeding stand 14d. When the manual pick-up roller 14e is rotated in such a state, the recording sheet pressed against the manual pick-up roller 14e is fed out to a manual-side conveyance path 14s provided with a manual paper feed roller 14f and a manual separation roller 14g. The recording sheet fed by the manual pickup roller 14e is supplied to the manual feed roller nip between the manual feed roller 14f and the manual separation roller 14g provided in the manual feed path 14s. One recording sheet separated by the rotation of the manual separation roller 14g passes through the manual-side paper feed nip, and is conveyed to the conveyance unit 13 through the manual-side conveyance path 14s.

  As shown in FIG. 3, the manual-feed-side transport path 14s includes a manual-feed side on the downstream side (left side) in the recording sheet transport direction with respect to the manual-feed-side feed nip between the manual feed roller 14f and the manual separation roller 14g. A manual-side first lower guide 14h is provided for guiding the lower surface of the recording sheet that has passed through the sheet feeding nip obliquely upward to the left. The manual feed-side first lower guide 14h is inclined at an angle of about 38 ° with respect to the horizontal line from the obliquely upper left position of the manual separation roller 14g adjacent to the manual feed nip to the obliquely upper left side. A sheet guide surface is provided. A manual side second lower guide 14k is provided further downstream (left side) in the recording sheet conveyance direction of the manual side first lower guide 14h. The manual feed-side second lower guide 14k has an inclination angle of about 40 ° (50 ° with respect to the horizontal line) with respect to the manual-feed conveyance guide 14c that is substantially vertical from the upper end of the manual-feed conveyance guide 14c, that is, The guide surface of the recording sheet extending toward the left side of the front end portion of the manual feed side first lower guide 14h at an inclination angle steeper than that of the manual feed side first lower guide 14h is integrated with the manual feed side conveyance guide 14c. Is provided. The leading end portion of the recording sheet guided by the manual side first lower guide 14h is guided further upward by the manual side second lower guide 14k. The direction in which the recording sheet is guided by the guide surface (upper surface) of the manual feed side second lower guide 14k is equal to the direction of the upward extension along the guide surface (upper surface) of the manual feed side second lower guide 14k. The direction is slightly lower than the center of the first transport driving roller 13a, and therefore intersects with the substantially intermediate position in the vertical direction of the flexible guide 12k and intersects with the outer peripheral surface of the first transport unit 13. ing.

  As described above, the upper end portion of the manual feed side transport path 14s joins the upper end portion of the cassette side transport path 12m, and the upper end portion of the first vertical transport path 15 also joins at the joining position. A flexible guide 12k is provided. The flexible guide 12k is bent toward the first conveyance drive roller 13a side of the first conveyance unit 13 when the recording sheet conveyed from the manual conveyance path 14s contacts.

  In addition, a manual feed side upper guide 14m is provided above the manual feed side second lower guide 14k and the manual feed side first lower guide 14h in the manual feed path 14s. The manual-feed-side upper guide 14m extends from the left side of the manual feed roller 14f obliquely upward to the left with an inclination angle smaller than that of the manual-feed-side second lower guide 14k.

  As shown in FIG. 1, the second paper feed unit 20 provided on the lower side of the first paper feed unit 10 has a configuration of a second paper feed unit 22 provided on the upper right side of the second paper feed cassette 21. The configuration of the first paper feed unit 12 in the first paper feed unit 10 is the same as that of the first transport unit 13, and the configuration of the second transport unit 23 is the same as the configuration of the first transport unit 13 in the first paper feed unit 10. It has become. Further, the second sheet feeding unit 20 is provided with a second vertical conveyance path 25 for conveying the recording sheet fed by the third sheet feeding unit 30 and the fourth sheet feeding unit 40 to the second conveyance unit 23. Yes. The second vertical conveyance path 25 is formed in a substantially vertical state below the first vertical conveyance path 15 in the first paper feeder 10. The recording sheet in the third paper feed cassette 31 in the third paper feed unit 30 is transported to the second transport unit 23 through the second vertical transport path 25 by the third paper feed unit 32 and the third transport unit 33. The The recording sheets in the fourth paper feed cassette 41 in the fourth paper feed unit 40 are secondly passed through the second vertical transport path 25 by the fourth paper feed unit 42, the fourth transport unit 43, and the fifth transport unit 44. It is transported to the transport unit 23. Each recording sheet conveyed to the second conveyance unit 23 is conveyed to the first conveyance unit 13 through the first vertical conveyance path 15, and is transferred by the first conveyance unit 13 to the transfer nip in the image processing unit B. Transported to N1.

  In the copying machine having such a configuration, a case where a recording sheet stored in the first paper feed cassette 11 in the first paper feed unit 10 is conveyed to the image processing unit B will be described. In this case, the uppermost recording sheet accommodated in the first paper feed cassette 11 is pressed against the cassette side pickup roller 12a of the first paper feed unit 12 by the urging force of the cassette paper feed base 11a. When the cassette-side pickup roller 12a is rotated in such a state, the uppermost recording sheet is a cassette between the cassette-side paper feed roller 12b and the cassette-side separation roller 12c provided in the cassette-side transport path 12m. The recording sheet is supplied to the side paper feeding nip, and one recording sheet is separated by the rotation of the cassette side paper feeding roller 12b and the cassette side separation roller 12c, and passes through the cassette side paper feeding nip obliquely upward to the right.

  The leading edge of the recording sheet that has passed through the cassette-side paper feed nip is in contact with the guide surface of the cassette-side first paper feed guide 12f disposed close to the upper portion of the cassette-side separation roller 12c on the downstream side in the transport direction. Slide toward As a result, the leading end of the recording sheet is guided to the guide surface of the cassette-side first paper feed guide 12f and conveyed obliquely upward to the right with the conveying direction directed further upward. When the leading edge of the recording sheet passes through the guide surface of the cassette-side first paper feed guide 12f, it contacts the guide surface of the cassette-side second paper feed guide 12h provided on the downstream side in the transport direction and faces upward. Slide. In this case, since the guide surface of the cassette-side second paper feed guide 12h is inclined at a steeper angle than the guide surface of the cassette-side first paper feed guide 12f, the leading edge of the recording sheet is the cassette-side first paper feed. The paper guide 12f is directed further upward than the guide direction by the guide surface of the paper guide 12f, and is guided upward by the guide surface of the cassette-side second paper feed guide 12h. Thereafter, the leading end of the recording sheet comes into contact with a flexible guide 12k provided continuously above the cassette-side second paper feed guide 12h at the upper end of the cassette-side conveyance path 12m.

  The flexible guide 12k is a third paper feed guide provided on the lower side of the first transport driven roller 13b in the first transport unit 13 when the upper end of the recording sheet 13 is bent in the right direction when the leading end of the recording sheet comes into contact. It will be in the state contact | abutted to 13d. The recording sheet is guided to a conveyance nip which is a pressure contact portion between the first conveyance driven roller 13b and the first conveyance driving roller 13a by a flexible guide 12k whose upper end is bent rightward. The recording sheet thus introduced into the transport nip passes through the transport nip and is transported to the image process section B above the first transport unit 13, and a toner image is formed in the image process section B.

In this case, the recording sheet accommodated in the first paper feed cassette 11 is fed out by the cassette paper feed stand 11a in an inclined state with the end on the paper feed direction side facing upward, When guided through the path 12m to the conveyance nip, which is a pressure contact portion between the first conveyance driven roller 13b and the first conveyance drive roller 13a, a relatively large curved state is formed in a direction perpendicular to the conveyance nip. Enter almost along. For this reason, even thick paper with a basis weight of about 256 g / mm ² can be smoothly fed to the transport nip.

  The recording sheet that has passed through the conveyance nip is conveyed to the registration roller 66 and is in a looped shape with the conveyance nip by coming into contact with the registration roller 66, but the first conveyance driving roller 13a. Is in contact with substantially the entire length in the width direction of the recording sheet to be conveyed, so that the front end portion and the rear end portion of the recording sheet are suppressed from being twisted. Thereby, generation | occurrence | production of the noise which arises when the recording sheet of the twisted state passes a conveyance nip can be suppressed.

Next, a case where thin paper having a basis weight of about 60 g / m ² is fed as a recording sheet from the manual feed unit 14 will be described. When such a recording sheet is placed on the manual feed tray 14b of the manual feed unit 14, the recording sheet is inclined along the sheet placing portion 14j, and the end of the recording sheet on the paper feeding side is manually fed. The table 14d is pressed against the manual pickup roller 14e. In this state, when the manual pickup roller 14e is rotated, the recording sheet is fed diagonally to the upper left direction between the manual paper supply roller 14f and the manual separation roller 14g in the manual conveyance path 14s. It is introduced into the manual feed side paper feed nip between the manual paper feed roller 14f and the manual separation roller 14g. The recording sheet introduced into the manual feed nip passes through the manual feed nip by the rotation of the manual feed roller 14f and the manual separation roller 14g.

  The leading edge of the recording sheet that has passed through the manual feed nip slides in contact with the guide surface of the manual first lower guide 14h on the downstream side in the transport direction of the manual feed nip, thereby further improving the transport direction. It is conveyed in a state of being directed upward. Thereafter, the leading end portion of the recording sheet comes into contact with the guide surface of the manual feed side second lower guide 14k and slides further upward than the direction guided by the guide surface of the manual feed side first lower guide 14h. In the directed state, the sheet is conveyed by sliding on the guide surface of the manual feed side second lower guide 14k. Although the recording sheet is a thin paper with low stiffness, the leading end may be curved upward away from the guide surface of the manual feed side second lower guide 14k. The upper surface of the recording sheet is surely guided toward the upper end of the manual second lower guide 14k (downstream in the recording sheet conveyance direction) by the upper manual feed side guide 14m provided above.

  Thereafter, the leading end portion of the recording sheet passes between the respective ends of the manual feed side second lower guide 14k and the manual feed side upper guide 14m, and is provided at the joining position of the manual feed side transport path 14s and the cassette transport path 12m. It abuts on the flexible guide 12k. In this case, since the recording sheet is thin paper, the pressure applied to the flexible guide 12k is small, and the flexible guide 12k is hardly bent to the left side (the first transport driving roller 13a side). The leading edge of the sheet is introduced into a gap formed between the third paper feed guide 13d and guided toward the transport nip between the upper first transport drive roller 13a and the first transport driven roller 13b. To do. The recording sheet introduced into the conveyance nip passes through the conveyance nip and is conveyed to the image processing unit B above the first conveyance unit 13, and a toner image is formed on the recording sheet in the image processing unit B.

FIG. 8 shows as P1 a state in which the recording sheet is conveyed from the manual conveyance path 14s to the conveyance nip when a thin sheet having a basis weight of about 64 g / m ² is fed from the manual feeding unit 14 as a recording sheet. The recording sheet (thin paper) is guided by the manual feed side first lower guide 14h and the manual feed side second lower guide 14k of the manual feed unit 14, and keeps a substantially constant curved state and comes into contact with the flexible guide 12k. Since the recording sheet (thin paper) is weak, the flexible guide 12k hardly bends. Therefore, the recording sheet is further curved and guided toward the upper conveyance nip, and the recording sheet is greatly curved. It becomes a state. However, since the recording sheet is thin paper, the rear end portion of the recording sheet in a largely curved state does not have a risk of greatly pushing down the manual sheet feeding base 14d.

Next, the operation in the case of feeding thick paper having a basis weight of 300 g / m ² from the manual feed unit 14 as a recording sheet will be described. As in the case of thin paper, such a recording sheet (thick paper) is conveyed by the manual pickup roller 14e through the manual conveyance path 14s and is brought into contact with the flexible guide 12k. In this case, since the recording sheet is a thick thick paper, the leading edge of the recording sheet is guided by the guide surface of the manual side first lower guide 14h and the manual side second lower guide 14k depending on the strength of the recording sheet itself. Therefore, a relatively large pressure is applied to the flexible guide 12k in order to slide in contact with the flexible guide 12k while being pressed strongly against the guide surface. As a result, the flexible guide 12k is greatly bent to the left side (the first conveyance drive roller 13a side), and the manual feed side second lower guide 14k is not obstructed by the traveling direction of the leading end portion of the recording sheet. Guide in the direction along. Therefore, the recording sheet is guided by the flexible guide 12k in the straight direction along the manual feed side second lower guide 14k without being bent so that the conveying direction is almost upward, and the leading end of the recording sheet is It abuts on the outer peripheral surface of the first transport driving roller 13a. The outer peripheral surface of the first transport driving roller 13a has a higher coefficient of friction than the outer peripheral surface of the first transport driven roller 13b, and is substantially the width direction orthogonal to the transport direction of the maximum size recording sheet to be transported. Since the recording sheet is configured to be able to contact the entire length, the leading edge of the recording sheet moves following the outer peripheral surface of the first transport driving roller 13a over the substantially entire length in the width direction, and the first transport driven roller 13b To the conveyance nip which is the pressure contact position. As a result, the leading edge of the recording sheet is reliably introduced into the conveyance nip according to the entire length in the width direction. In this way, the recording sheet introduced into the conveyance nip passes through the conveyance nip and is conveyed to the image processing unit B above the first conveyance unit 13, and the toner image is formed on the recording sheet in the image processing unit B. It is formed.

The regulation guide 13e provided below the first transport drive roller 13a is retracted 4.3 mm from the common tangent L on the right side (manual unit 14 side) of the first transport drive roller 13a and the cassette-side paper feed roller 12b. Since the recording sheet is positioned on the left side of the extension line in the conveyance direction of the recording sheet guided by the manual-side second lower guide 14k in the manual-side conveyance path 14s, the recording sheet has a basis weight of 300 g / m. ^Even with thick paper of ² or more, there is almost no possibility of coming into contact with the regulation guide 13e, and it can be reliably brought into contact with the outer peripheral surface of the first transport drive roller 13a.

FIG. 9 shows P2 as a state in which thick paper having a basis weight of 300 g / m ² is fed from the manual feed unit 14 as a recording sheet from the manual feed path 14s to the transport nip. The leading end of the cardboard is guided upward by the manual feed side first lower guide 14h and the manual feed side second lower guide 14k of the manual feed unit 14, but when coming into contact with the flexible guide 12k, the flexible guide 12k. Against this restoring force, it goes straight along the guiding direction of the manual feed side second lower guide 14k and comes into contact with the first conveyance drive roller 13a on the upper left side. As a result, the leading edge of the recording sheet moves smoothly following the rotation of the outer peripheral surface of the first conveyance driving roller 13a having a high friction coefficient, so that the leading edge of the recording sheet is smoothly introduced into the conveyance nip. In this case, the recording sheet follows the outer peripheral surface of the first conveyance driving roller 13a and moves toward the conveyance nip, so that the recording sheet is in a small curved state. Since the portion of the lower guide 14k that goes straight along the guiding direction is formed long in a relatively wide space, the stress generated by the bending is almost absorbed in the straight portion, and the rear end of the cardboard There is no risk of affecting parts. Accordingly, the cardboard is curved in the direction toward the conveyance nip between the flexible guide 12k and the first conveyance drive roller 13a, but the curved state hardly changes in the manual conveyance path 14s. As a result, when the rear end portion of the recording sheet passes between the manual paper feed table 14d and the manual pickup roller 14e, the force for pressing the manual paper feed table 14d downward is reduced. As a result, the end on the sheet feeding side is reliably pressed against the manual pickup roller 14e, and the manual sheet feed table 14d is pushed down by a large pressing force from the rear end of the thick paper as in the conventional case, so that the second recording sheet Can be prevented from coming into contact with the pickup roller 14e at a predetermined pressure, and even when thick paper is continuously fed from the manual feed tray 14b, a paper jam occurs due to the fact that any thick paper is not fed. Can be prevented.

The direction in which the recording sheet is guided by the flexible guide 12k is determined by the relationship between the waist strength of the recording sheet itself and the restoring force of the flexible guide 12k. Since the recording sheet becomes stronger as the basis weight increases, the amount of deflection of the flexible guide 12k increases proportionally as the strength of the waist increases, and the basis weight is 300 g / mm. ^{Even in the case of two} or more recording sheets, it can be made to go straight by bending of the flexible guide 12k. As a result, paper can be fed from the manual feed tray 14b without causing paper jams.

  In the above embodiment, the cassette side separation roller 12c is brought into pressure contact with the cassette side paper supply roller 12b in order to separate one recording sheet fed from the first paper supply cassette 11 by the cassette side pickup roller 12a. The configuration is not limited to the roller, but other separation members may be used as long as the configuration separates one recording sheet. Similarly, instead of the manual separation roller 14g, another separation member may be pressed against the manual paper feed roller 14f.

  The image forming apparatus to which the sheet conveying mechanism according to the present invention is applied is not limited to a tandem type color digital copying machine. For example, four developing devices are arranged around a rotating shaft, and these four developing devices are arranged. May be a so-called four-cycle image forming apparatus that forms a full-color image sequentially facing the electrostatic latent image carrier, a monochrome image forming apparatus that includes only one developing device, and the like. The sheet conveying mechanism of the present invention is not limited to a copying machine, but can be applied to a printer, a FAX, an MFP (Multiple Function Peripheral), and the like.

  In the present invention, even when stiff recording sheets such as cardboard are placed in a stacked state on a manual feed tray and fed, each recording sheet can be continuously and smoothly fed without causing paper jams. Paper can be fed.

1 is a schematic front view showing a schematic configuration of a tandem type color digital copying machine which is an example of an image forming apparatus according to the present invention. FIG. 3 is a cross-sectional view showing a specific configuration of a first paper feed unit provided in the copier. It is sectional drawing which expands and shows the right side part and its peripheral part of a 1st paper feed part. It is operation | movement explanatory drawing of the cassette side conveyance guide provided in the 1st paper feed part. It is a perspective view for demonstrating the structure of the 1st conveyance drive roller in a 1st conveyance unit. It is a perspective view for demonstrating the structure of the 1st conveyance driven roller in a 1st conveyance unit. FIG. 6 is a perspective view illustrating a state where the manual feed unit is rotated with respect to the apparatus main body. FIG. 10 is an explanatory diagram of a state in which thin paper is fed to a conveyance nip when thin paper is fed from a manual feed unit as a recording sheet. FIG. 6 is an explanatory diagram of a state in which thick paper is fed to a conveyance nip when thick paper is fed from a manual feed unit as a recording sheet.

Explanation of symbols

A sheet transport mechanism B image processing unit C image reading unit 10 first sheet feeding unit 11 first sheet feeding cassette 11a cassette sheet feeding table 12 first sheet feeding unit 12a cassette side pickup roller 12b cassette side sheet feeding roller 12c cassette side separation Roller 12d Cassette side transport guide 12e First support pin 12f Cassette side first paper feed guide 12h Cassette side second paper feed guide 12m Cassette side transport path 13 First transport unit 13a First transport drive roller 13b First transport driven roller 13c Third support pin 13d Third paper feed guide 13e Restriction guide 14 Manual feed unit 14a Manual feed unit main body 14b Manual feed tray 14c Manual feed side conveyance guide 14d Manual feed tray 14e Manual pickup roller 14f Manual feed roller 14g Manual feed separation b La 14h Manual feed side first lower guide 14j Sheet placement portion 14k Manual feed side second lower guide 14m Manual feed side upper guide 14s Manual feed side transport path 15 First vertical transport path 20 Second paper feed section 21 Second paper feed cassette 22 Second 2 paper feed unit 23 2nd transport unit 30 3rd paper feed unit 31 3rd paper feed cassette 32 3rd paper feed unit 33 3rd transport unit 40 4th paper feed unit 41 4th paper feed cassette 42 4th paper feed unit 43 Fourth transport unit 44 Fifth transport unit 51 Intermediate transfer belt 52Y, 52M, 52C, 52K Image forming unit 53 Exposure device 58 Secondary transfer roller 59 Fixing section

Claims (11)

Cassette-side conveying means for delivering the recording sheet from the paper feeding cassette and conveying the fed recording sheet while being curved so as to face obliquely upward;
A manual feed tray that is disposed so as to face the paper feed cassette and is inclined so that the paper feed direction side is lowered, and a paper feed direction of the recording sheet placed on the manual feed tray A manual sheet feeding table that urges the end on the side upward, and a sheet feeding direction end of the recording sheet placed on the manual sheet feeding table in pressure contact with the manual sheet feeding A manual feed side conveying means for conveying the recording sheet fed by the pickup roller in a curved state so as to face obliquely upward;
A flexible guide for guiding each recording sheet conveyed obliquely upward by the cassette-side conveying means and the manual-side conveying means, further upward;
A pair of left and right conveying rollers that are pressed against each other, and each recording sheet conveyed upward by the flexible guide is disposed so as to pass through a conveying nip between the pair of conveying rollers. A unit, and
When a strong recording sheet is conveyed by the manual feed side conveying means, the flexible guide is bent by the recording sheet, and the curved state of the recording sheet is reduced as compared with the case where a weak recording sheet is conveyed. A sheet conveying mechanism characterized by that.   The pair of transport rollers includes a first transport roller disposed in front of a recording sheet transported by the manual transporting unit, and a second transport roller disposed in front of the recording sheet transported by the cassette transporting unit. 2. The sheet conveying mechanism according to claim 1, wherein a conveying direction of the recording sheet by the manual-side conveying unit is substantially parallel to a diameter direction of the first conveying roller.   The first conveying roller has a recording sheet having a maximum length in the width direction orthogonal to the conveying direction in the recording sheet that can pass through the conveying nip. The sheet conveying mechanism according to claim 1, wherein the sheet conveying mechanism is slightly shorter than the length in the width direction of the recording sheet so as to contact the vicinity of the edge.   4. The sheet conveying mechanism according to claim 3, wherein the second conveying roller has an axial length shorter than that of the first roller, and is pressed against a central portion of the first roller in the axial direction.   5. The sheet conveying mechanism according to claim 3, wherein a friction coefficient of an outer peripheral surface of the first conveying roller is higher than a friction coefficient of an outer peripheral surface of the second conveying roller.   Under the first conveying roller, the recording sheet conveyed toward the first conveying roller is restricted from entering the opposite side of the conveying nip with respect to the first conveying roller, and the first conveying roller is restricted. The sheet conveying mechanism according to any one of claims 2 to 5, further comprising a regulation guide for guiding toward the outer peripheral surface of the one conveying roller.   The cassette-side conveying means is provided with a cassette-side sheet feeding roller and a cassette-side separating member that are pressed against each other in a vertical direction so as to separate and convey the recording sheets fed from the sheet feeding cassette one by one. The sheet conveying mechanism according to claim 6.   The regulation guide is disposed on a side opposite to the conveyance path with respect to a common tangent line between the cassette-side sheet feeding roller and the first conveyance roller, which is positioned on the recording sheet conveyance path side by the cassette-side sheet feeding roller. The sheet conveying mechanism according to claim 7, wherein the sheet conveying mechanism is provided. A second paper feed cassette is provided below the paper feed cassette;
A recording sheet fed from the second paper feeding cassette passes through a vertical conveyance path provided along the vertical direction between the cassette-side conveyance means and the manual conveyance means, and the flexible guide The sheet conveyance mechanism according to claim 1, wherein the sheet conveyance mechanism is conveyed toward the conveyance nip.   The sheet conveying mechanism according to claim 1, wherein the waist of the recording sheet becomes stronger as the weight per unit area of the recording sheet increases. A sheet conveying mechanism according to any one of claims 1 to 10,
An image processing unit for forming a toner image on a recording sheet conveyed by the sheet conveying mechanism;
An image forming apparatus comprising:

Images