JP2006315775A - Image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a means for preventing reduction of the nip pressure in a central part in the roller axial direction due to bend of a pushing roller and for preventing reduction of the nip pressure due to engagement of gears of a feeding roller with gears of the pushing roller in a resist roller pair formed of the feeding roller and the pushing roller. <P>SOLUTION: In this image forming device 1, the feeding roller 17 and the pushing roller 18 are structured so that both ends of the feeding roller 17 in the roller axial direction are energized toward the pushing roller 18 to work as a resist roller pair 5 brought in pressure-contact with each other, and this resist roller pair 5 feeds the recording papers P to an image transferring position 10 by correcting bias feed of the recording papers P. The pushing roller 18 is formed into a crown-shape, of which diameter is reduced as it comes from a central part in the roller axial direction toward both ends in the roller axial direction, and one end of the feeding roller 17 in the roller axial direction on a driving gear 21 side is strongly energized toward the pushing roller 18 by the other end thereof in the roller axial direction. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus for transferring a toner image on a photosensitive drum onto a recording sheet by nipping the recording sheet conveyed on a conveying path between the photosensitive drum and a transfer roller, and more particularly to an upstream side of the photosensitive drum. The present invention also relates to an image forming apparatus provided with a registration roller pair that corrects the skew of the recording paper and sends the recording paper in time with image formation on a photosensitive drum.

  Many copiers, facsimile machines, and the like function as image forming apparatuses that form images on recording paper based on image data read from a document or image data received by facsimile. FIG. 5 is a block diagram illustrating an example of a conventional image forming apparatus. In this image forming apparatus 70, when a print command is issued from the user, the surface of the photosensitive drum 71 on which the photosensitive layer is formed is uniformly charged by the charging device 72, and light corresponding to the image data to be recorded is exposed. An electrostatic latent image is formed on the photosensitive drum 71 by irradiation from the device 73, and a toner image is formed by supplying toner from the developing device 74 to the electrostatic latent image. On the other hand, with the start of the image forming operation, the recording paper P set in the paper feed cassette 75 is sequentially fed into the transport path 77 by the pickup roller 76. The recording paper P is skewed by correcting the leading edge of the recording paper P against the registration roller pair 78, and the registration roller pair 78 rotates in synchronization with the image formation on the photosensitive drum 71. Sent to the side. The toner image on the photosensitive drum 71 is transferred to the recording paper P when the recording paper P passes through the transfer nip position 80 where the transfer roller 79 is pressed against the photosensitive drum 71. Further, the recording paper P is transported to the downstream side of the transport path 77 and is heated and pressurized by the fixing device 81 to fix the toner image on the recording paper P, and then to the most downstream portion of the transport path 77. The paper is discharged to a paper discharge tray 83 by a paper discharge roller 82 provided.

  FIG. 6 is a schematic plan view showing the configuration of the registration roller pair 78. The registration roller pair 78 includes a feed roller 84 having a roller surface formed of a member having a large friction coefficient with respect to the recording paper, and a pressing roller 85 having a roller surface formed of a member having a small friction coefficient with respect to the recording paper. It is. Both ends of the feed roller 84 are rotatably held by a pair of left and right bearings 86, and the left and right bearings 86 are urged by an urging spring 87 with an equal force F1, so that they are pressed against the pressing roller 85. ing. The feed roller 84 is driven to rotate by transmitting a driving force of a motor (not shown) to a driving gear 88 provided on one end side. On the other hand, the pressing roller 85 is rotatably mounted between the frame members 89 forming the image forming apparatus 70, and the interlocking gear 90 provided on one end side is engaged with the driving gear 88 of the feeding roller 84 to thereby feed the pressing roller 85. It rotates in conjunction with the roller 84. Thus, the registration roller pair 78 nips the recording paper P between the feeding roller 84 and the pressing roller 85 and conveys the recording paper P by the frictional force generated between the recording paper P and the feeding roller 84. Yes.

  However, in this registration roller pair 78, the long pressing roller 85 supported at both ends is pressed in a direction substantially perpendicular to the roller axial direction by the feed roller 84, so the pressing roller 85 is indicated by a dotted line in FIG. As shown, both ends are bent as fulcrums, and the nip pressure is reduced at the center in the axial direction of the roller. For this reason, the pulling force of the recording paper P is weaker at the central portion in the roller axial direction of the registration roller pair 78 than at both ends in the roller axial direction, and the conveying force for the narrow recording paper P is larger than that for the wide recording paper P. It becomes weaker than the conveying force. As a result, there is a problem in that there is a difference in the image expansion / contraction ratio in the sub-scanning direction between the recording sheets P having different width sizes, and the leading edge writing position varies.

  2. Description of the Related Art Conventionally, an image forming apparatus that solves the problem of a decrease in nip pressure at the center in the axial direction of a pair of registration rollers has been proposed (see, for example, Patent Document 1). In this image forming apparatus, a pair of conveying rollers facing each other across the conveying path is provided at a position immediately upstream of the pair of registration rollers. The parts are pressed against each other with a weak spring. As a result, the nip pressure at the central portion in the roller axial direction is reduced by the registration roller pair, so that a high nip pressure is applied to the central portion in the roller axial direction by the pair of transport rollers, thereby conveying the recording paper uniformly in the width direction. It is possible to give power.

Japanese Patent Laid-Open No. 7-76436

  However, according to the image forming apparatus according to Patent Document 1, it is necessary to separately provide a pair of conveying rollers in addition to the pair of registration rollers, which increases the number of parts, leading to an increase in manufacturing cost and an increase in the size of the apparatus. is there. In the image forming apparatus 70, since the feed roller 84 and the pressing roller 85 receive the reaction force F2 at the meshing portion of the driving gear 88 and the interlocking gear 90, the nip pressure on the gear meshing side in the roller axial direction is reduced. It becomes lower than the nip pressure on the opposite side. Accordingly, there is a problem that the recording paper P is transported obliquely, which causes deterioration of image quality and paper jam.

  The present invention has been made in view of such a problem, and prevents a decrease in the nip pressure at the central portion in the roller axial direction due to the bending of the registration roller pair without increasing the number of components, and Means are provided for preventing a decrease in nip pressure at the end in the axial direction of the roller due to the meshing of the gear of the pressing roller and the gear of the conveying roller.

  The image forming apparatus according to claim 1, wherein a drive gear is provided at one end in the roller axial direction and a feed roller feeds recording paper to the downstream side of the conveyance path, and the drive gear at one end in the roller axial direction. A registration roller provided with an interlocking gear that meshes with the pressure roller and presses the recording paper against the feed roller, and is pressed against each other by urging both end portions in the roller axial direction of the feed roller toward the pressure roller. In the image forming apparatus in which the pair corrects the skew of the recording paper and sends it to the image transfer position, the pressing roller has a crown shape in which the diameter gradually decreases from the central portion in the roller axial direction toward both ends in the roller axial direction. In addition, one end in the roller axial direction on the drive gear side of the feed roller is more strongly biased toward the pressing roller than the other end in the roller axial direction.

  3. The image forming apparatus according to claim 2, wherein a driving gear is provided at one end portion in the roller axial direction and a feed roller for feeding the recording paper to the downstream side of the conveying path and an interlocking gear meshing with the driving gear at one end portion in the roller axial direction are provided. The registration roller pair formed by pressing the recording sheet against the feeding roller and the pressure roller is pressed against each other by urging both end portions of the pressing roller in the axial direction toward the feeding roller. In the image forming apparatus that corrects the line and feeds it to the image transfer position, the pressure roller has a crown shape that gradually decreases in diameter from the central part in the roller axial direction toward both ends in the roller axial direction, and the pressure roller The one end of the interlocking gear in the roller axial direction is urged stronger toward the feed roller than the other end in the roller axial direction.

  The image forming apparatus according to claim 3, wherein a driving gear is provided at one end portion in the roller axial direction and a feed roller that feeds recording paper to the downstream side of the conveyance path, and an interlocking gear that meshes with the driving gear at one end portion in the roller axial direction. The registration roller pair formed by pressing the recording paper against the feeding roller and the pressure roller is pressed against each other by urging both end portions of the feeding roller in the roller axial direction toward the pressing roller. In the image forming apparatus that corrects a row and feeds it to an image transfer position, the feed roller includes a roller shaft and a plurality of roller bodies arranged along the roller shaft, and is located at a central portion in the roller axial direction. Is larger in diameter than the roller body located at both ends in the roller axial direction, and one end in the roller axial direction on the drive gear side of the feed roller is stronger than the other end in the roller axial direction. Those that are biased to the pressing roller.

  5. The image forming apparatus according to claim 4, wherein a driving gear is provided at one end portion in the roller axial direction and a feed roller for feeding the recording paper to the downstream side of the conveyance path and an interlocking gear meshing with the driving gear at one end portion in the roller axial direction are provided. The registration roller pair formed by pressing the recording sheet against the feeding roller and the pressure roller is pressed against each other by urging both end portions of the pressing roller in the axial direction toward the feeding roller. In the image forming apparatus that corrects a row and feeds it to an image transfer position, the feed roller includes a roller shaft and a plurality of roller bodies arranged along the roller shaft, and is located at a central portion in the roller axial direction. Is larger in diameter than the roller body located at both ends in the roller axial direction, and one end in the roller axial direction on the interlocking gear side of the pressing roller is stronger than the other end in the roller axial direction. Those that are biased to the feed roller side.

  6. The image forming apparatus according to claim 5, wherein a driving gear is provided at one end portion in the roller axial direction and a feed roller that feeds the recording paper to the downstream side of the conveyance path and an interlocking gear that meshes with the driving gear at one end portion in the roller axial direction. The registration roller pair formed by pressing the recording paper against the feeding roller and the pressure roller is pressed against each other by urging both end portions of the feeding roller in the roller axial direction toward the pressing roller. In the image forming apparatus that corrects the line and feeds it to the image transfer position, the feed roller is made of a member having a larger coefficient of friction with respect to the recording paper than the both ends in the roller axis direction. One end in the roller axial direction on the drive gear side is urged toward the pressing roller more strongly than the other end in the roller axial direction.

  7. The image forming apparatus according to claim 6, wherein a driving gear is provided at one end portion in the roller axial direction and a feed roller that feeds recording paper to the downstream side of the conveying path and an interlocking gear that meshes with the driving gear at one end portion in the roller axial direction. The registration roller pair formed by pressing the recording sheet against the feeding roller and the pressure roller is pressed against each other by urging both end portions of the pressing roller in the axial direction toward the feeding roller. In the image forming apparatus that corrects the line and feeds it to the image transfer position, the feed roller is made of a member having a larger coefficient of friction with respect to the recording paper at the center in the roller axial direction than at both ends in the roller axial direction. One end portion in the roller axial direction on the interlocking gear side is urged toward the feed roller side more strongly than the other end portion in the roller axial direction.

  According to the image forming apparatus of the first aspect of the present invention, the deflection generated in the pressure roller is compensated for by previously forming the central portion in the roller axial direction to be thick, and the central portion in the roller axial direction is substantially different from other portions. The pressure roller and the feed roller can be brought into pressure contact with equal nip pressure. Also, the decrease in the nip pressure caused by the meshing of the drive gear of the feed roller and the interlocking gear of the pressure roller is compensated by strongly urging the end of the drive roller on the drive gear side in advance to the pressure roller side. The nip pressure on the side can be made substantially equal to the nip pressure on the non-driving side. As described above, the nip pressure of the registration roller pair can be kept uniform in the roller axial direction, and the image expansion rate and the leading edge writing position in the sub-scanning direction can be kept constant regardless of the width of the recording paper. it can. Further, since the number of parts does not increase, there is no increase in cost and size of the apparatus.

  According to the image forming apparatus of the second aspect of the present invention, the deflection generated in the pressing roller is compensated for by previously forming a thick central portion in the roller axial direction. Further, the decrease in the nip pressure due to the meshing of the drive gear and the interlocking gear is compensated for by strongly biasing the end portion of the pressing roller on the interlocking gear side in advance toward the feed roller. Thus, the same effect as that of the image forming apparatus according to the first aspect can be obtained.

  According to the image forming apparatus of the third aspect of the present invention, the deflection generated in the pressing roller is larger in diameter than the roller main body positioned at both ends in the roller axial direction at the roller main body in the central portion in the roller axial direction of the feed roller. It is compensated for that. Further, the decrease in the nip pressure caused by the meshing of the drive gear and the interlocking gear is compensated by strongly urging the end portion of the feed roller on the drive gear side in advance to the pressing roller side. Thus, the same effect as that of the image forming apparatus according to the first aspect can be obtained.

  According to the image forming apparatus of the fourth aspect of the present invention, the deflection generated in the pressing roller is larger in diameter than the roller main body positioned at both ends in the roller axial direction at the roller main body in the central portion in the roller axial direction of the feed roller. It is compensated for that. Further, the decrease in the nip pressure due to the meshing of the drive gear and the interlocking gear is compensated for by strongly biasing the end portion of the pressing roller on the interlocking gear side in advance toward the feed roller. Thus, the same effect as that of the image forming apparatus according to the first aspect can be obtained.

  According to the image forming apparatus of the fifth aspect of the present invention, the amount of deflection generated in the pressing roller is recorded from the roller main body located at the center in the roller axial direction of the feed roller from the roller main body located at both ends in the roller axial direction. It is compensated by forming from a member having a large coefficient of friction against paper. Further, the decrease in the nip pressure caused by the meshing of the drive gear and the interlocking gear is compensated by strongly urging the end portion of the feed roller on the drive gear side in advance to the pressing roller side. Thus, the same effect as that of the image forming apparatus according to the first aspect can be obtained.

  According to the image forming apparatus of the sixth aspect of the present invention, the deflection generated in the pressing roller is recorded from the roller main body positioned at the center in the roller axial direction of the feed roller from the roller main body positioned at both ends in the roller axial direction. It is compensated by forming from a member having a large coefficient of friction against paper. Further, the decrease in the nip pressure due to the meshing of the drive gear and the interlocking gear is compensated for by strongly biasing the end portion of the pressing roller on the interlocking gear side in advance toward the feed roller. Thus, the same effect as that of the image forming apparatus according to the first aspect can be obtained.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings. The image forming apparatus is a copy / facsimile multifunction peripheral having a document copying function, a facsimile communication function, an Internet facsimile communication function, and the like. Is formed. Of course, the present image forming apparatus can be configured as a copy-only machine having only a copy function or a facsimile-only machine having only a facsimile communication function.

  FIG. 1 is a schematic longitudinal sectional view showing a configuration of an image forming apparatus 1 according to the present embodiment. The image forming apparatus 1 includes a paper feed cassette 2 for storing the recording paper P, a pickup roller 4 for feeding the recording paper P in the paper feed cassette 2 to the conveyance path 3, and a downstream side of the pickup roller 4. A pair of registration rollers 5 arranged, a photosensitive drum 6 having a photosensitive layer formed on its surface and driven to rotate, a charging device 7 for charging the surface of the photosensitive drum 6, and an exposure for irradiating the surface of the photosensitive drum 6 with light. A device 8; a developing device 9 that supplies toner to the surface of the photosensitive drum 6; a transfer roller 11 that is pressed against the photosensitive drum 6 to form an image transfer position 10; and a cleaning device 12 that cleans the surface of the photosensitive drum 6. The fixing device 13 that heats and presses the recording paper P, the transport roller pair 14 that is appropriately disposed in the transport path 3 and transports the recording paper P downstream, and the recording paper P that is disposed in the most downstream part of the transport path 3. A paper discharge roller pair 16 for discharging to the discharge tray 15, it comprises a are those characterized by the structure of the registration roller pair 5.

  In the image forming apparatus 1 configured as described above, when a printing command is issued from the user, the surface of the photosensitive drum 6 is uniformly charged by the charging device 7, and light corresponding to the image data to be recorded is emitted to the exposure device 8. The electrostatic latent image is formed by partially removing the charge on the photosensitive drum 6 by irradiation from the developing device 9, and the toner image is formed by supplying toner from the developing device 9 to the electrostatic latent image. On the other hand, along with the start of such an image forming operation, the recording paper P stored in the paper feed cassette 2 is picked up one by one from the uppermost paper by the pickup roller 4 and fed into the transport path 3. The recording paper P strikes the resist roller pair 5 in a stationary state and bends to correct skewing during conveyance, and the registration roller pair 5 rotates to form an image on the photosensitive drum 6. Are sent to the image transfer position 10 at the same timing. At the image transfer position 10, the recording paper P is pressed against the photosensitive drum 6 by the transfer roller 11. At this time, a voltage having a polarity opposite to that of the photosensitive drum 6 is applied to the transfer roller 11. The toner image is transferred to the recording paper P. Further, the recording paper P is conveyed downstream through the conveying path 3 and is heated and pressurized by the fixing device 13, whereby the toner image on the recording paper P is fixed. Thereafter, the recording paper P is discharged to the paper discharge tray 15 by the paper discharge roller. On the other hand, after the toner image is transferred, the surface of the photosensitive drum 6 is charged again by the charging device 7 after the toner or paper dust remaining on the surface is removed by the cleaning device 12.

  Hereinafter, the configuration of the registration roller pair 5 will be described. As shown in FIG. 1, the registration roller pair 5 is rotated by a feeding roller 17 and a pressing roller 18 disposed so as to face each other with the conveyance path 3 interposed therebetween, by nipping the recording paper P conveyed from the upstream side. By doing so, it is sent out toward the image transfer position 10 on the downstream side. In the present invention, as shown in FIG. 1, a feed roller 17 and a pressure roller 18 are arranged on the inside of the apparatus with the conveyance path 3 interposed therebetween. It is also possible to dispose the roller 18 inside the apparatus and the roller 17 respectively.

  2 to 4 are schematic plan views showing the registration roller pair 5 according to the embodiment of the present invention. As shown in each drawing, the registration roller pair 5 includes a feeding roller 17 that actively rotates and feeds the recording paper P to the downstream side, and a pressing roller 18 that plays a role of pressing the recording paper P against the feeding roller 17. Consists of The feed roller 17 is generally called a registration roller, and is provided with a roller body 19 made of a member having a large friction coefficient against the recording paper P, such as rubber, around a roller shaft 19 made of metal or the like. . A driving gear 21 is fixed to one end of the roller shaft 19 of the feed roller 17, and the driving force of a motor (not shown) is transmitted to the driving gear 21 via the transmission gear 22 to be rotationally driven. Yes. On the other hand, the pressing roller 18 is generally called a pinch roller, and a roller body 24 made of a member having a small coefficient of friction with respect to the recording paper P, such as a resin or metal, is provided around a long roller shaft 23. Is. The pressing roller 18 is rotated in conjunction with the rotation of the feed roller 17 by fixing the interlocking gear 25 to one end of the roller shaft 23 and meshing with the driving gear 21 of the feeding roller 17. It is supposed to be. When the feed roller 17 and the pressure roller 18 configured as described above are brought into pressure contact with each other and the recording paper P is supplied to the pressure contact portion, a frictional force generated between the roller body 20 of the feed roller 17 and the recording paper P. Thus, the recording paper P is conveyed along with the rotation of the feed roller 17. In the present invention, the drive gear 21 is used as a gear for driving the feed roller 17 and a gear for interlocking with the pressing roller 18 by meshing with both the transmission gear 22 and the interlocking gear 25. Of course, the gear for driving the feed roller 17 and the gear for interlocking with the pressing roller 18 may be provided separately.

  FIG. 2 is a schematic plan view showing the registration roller pair 5 according to the first embodiment of the present invention. In this embodiment, in order to keep the nip pressure of the registration roller pair 5 constant throughout the roller axial direction, the roller main body 24 of the pressing roller 18 has a so-called crown shape, and the gear driving side of the registration roller pair 5 is It is characterized in that it is strongly pressed in advance from the non-driving side.

  In this embodiment, as shown in FIG. 2A, the pressing roller 18 is installed between the frame members 26 forming the image forming apparatus 1, and both end portions of the roller shaft 23 are rotated by a pair of left and right bearings 27. It is supported freely. Further, both ends of the roller shaft 19 of the feed roller 17 are rotatably supported by a pair of left and right bearings 28, and each bearing 28 is urged toward the pressing roller 18 by a pair of left and right urging springs 29 and 30, respectively. ing. In such a configuration, as described above, the long pressing roller 18 supported at both ends is bent as shown in FIG. 6 by being pressed in the direction perpendicular to the roller shaft 23 by the feed roller 17. Therefore, there is a problem that the nip pressure is lowered at the central portion of the registration roller pair 5 in the roller axial direction. In order to prevent this problem, in this embodiment, the roller body 24 of the pressure roller 18 is gradually reduced in diameter from the crown shape as shown in FIG. 2, that is, from the center in the roller axis direction toward both ends in the roller axis direction. It has a shape. The crown amount, that is, the reduced diameter when the outer diameter of the roller main body 24 at a predetermined position in the roller axial direction is compared with the outer diameter of the roller main body 24 at the center in the roller axial direction is set to a predetermined value in the roller axial direction of the pressing roller 18. The amount of bending that occurs at the position is approximately equal. In this way, the nip pressure between the feed roller 17 and the pressure roller 18 is compensated by compensating for the deflection generated in the pressure roller 18 by making the central portion in the roller axial direction of the roller body 24 thicker in advance than both ends in the roller axial direction. It is prevented from being lowered at the central part in the axial direction.

  Further, as described above, the registration roller pair 5 has a nip pressure on the gear driving side, that is, on the side where the driving gear 21 and the interlocking gear 25 are meshed with each other on the non-driving side, that is, the gear driving side. There is also a problem that it becomes lower than the nip pressure on the opposite side. In order to prevent this problem, in this embodiment, of the pair of left and right urging springs 29 and 30 that urge the feed roller 17 toward the pressing roller 18 side, the urging spring 30 on the gear driving side is urged on the non-driving side. A member having a stronger urging force than the urging spring 29 is used, whereby the gear driving side of the feed roller 17 is urged toward the pressing roller 18 with a force F2 larger than the urging force F1 on the non-driving side. In this manner, the nip pressure drop due to the engagement of the drive gear 21 and the interlocking gear 25 is compensated by strongly biasing the gear drive side, so that the nip pressure on the gear drive side becomes the nip pressure on the non-drive side. It is kept approximately equal.

  As shown in FIG. 2B, the feed roller 17 is installed between the frame members 26, and both ends of the roller shaft 19 are rotatably supported by a pair of left and right bearings 27, while the pressure roller 18 is supported. It is also possible to have a configuration in which both ends of the roller shaft 23 are rotatably supported by a pair of left and right bearings 28 and each bearing 28 is biased toward the feed roller 17 by a pair of left and right biasing springs 29 and 30. is there. Also in this case, by forming the roller body 24 of the pressing roller 18 into a crown shape, it is possible to prevent a decrease in the nip pressure at the central portion in the roller axial direction due to the bending of the pressing roller 18. Further, by urging the gear driving side of the pressing roller 18 toward the feeding roller 17 with a stronger force than the non-driving side, it is possible to prevent a decrease in nip pressure on the gear driving side.

  FIG. 3 is a schematic plan view showing the registration roller pair 5 according to the second embodiment of the present invention. In this embodiment, a plurality of roller main bodies 32 are arranged along the roller shaft 31 to form the feed roller 17, and the roller main body 32 at the center in the roller axial direction is made up of the roller main bodies 32 at both ends in the roller axial direction. It is characterized in that it has a large diameter and that the gear driving side of the registration roller pair 5 is strongly pressed in advance from the non-driving side. Since the point where the gear drive side is pressed more strongly than the non-drive side is the same as in the first embodiment, description thereof is omitted here.

  In this embodiment, as shown in FIG. 3A, the pressing roller 18 is installed between the frame members 26, and both end portions of the roller shaft 33 are rotatably supported by a pair of left and right bearings 34. . Further, both ends of the roller shaft 31 of the feed roller 17 are rotatably supported by a pair of left and right bearings 35, and each bearing 35 is biased toward the pressing roller 18 by a pair of left and right biasing springs 36 and 37, respectively. ing. In such a configuration, similarly to the first embodiment, there arises a problem that the nip pressure is lowered at the central portion in the roller axial direction due to the bending of the pressing roller 18. In order to prevent this problem, in this embodiment, three roller main bodies 32 are arranged along the roller shaft 31 to form the feed roller 17, and the middle roller main body 32 is slightly different from the left and right roller main bodies 32. Large diameter. The difference in outer diameter between the middle roller body 32 and the left and right roller bodies 32 is made substantially equal to the amount of bending that occurs at the center of the pressing roller 18 in the roller axial direction. In this way, the nip pressure between the feed roller 17 and the pressure roller 18 is compensated by compensating for the deflection generated in the pressure roller 18 by making the central portion in the roller axial direction of the feed roller 17 thicker than both ends in the roller axial direction. It is prevented from being lowered at the central part in the axial direction. Further, as compared with the first embodiment in which the pressing roller 18 has a crown shape, there is an advantage that labor and cost required for processing the roller can be reduced.

  As shown in FIG. 3B, the feed roller 17 is installed between the frame members 26, and both end portions of the roller shaft 31 are rotatably supported by a pair of left and right bearings 34, while the pressure roller 18 is provided. It is also possible to have a configuration in which both ends of the roller shaft 33 are rotatably supported by a pair of left and right bearings 35 and each bearing 35 is biased toward the feed roller 17 by a pair of left and right biasing springs 36 and 37. is there. Also in this case, three roller main bodies 32 are arranged in line along the roller shaft 31 to form the feed roller 17, and the middle roller main body 32 is slightly larger in diameter than the left and right roller main bodies 32, thereby It is possible to prevent a decrease in nip pressure at the central portion in the axial direction. Further, by urging the gear driving side of the pressing roller 18 toward the feeding roller 17 with a stronger force than the non-driving side, it is possible to prevent a decrease in nip pressure on the gear driving side.

  In this embodiment, the number of roller main bodies 32 of the feed roller 17 is not limited to three, and the design can be changed as appropriate. For example, six roller main bodies 32 are arranged in a row and two roller main bodies 32 in the center are arranged. Can be made larger in diameter than the other four roller bodies 32. Further, in accordance with the amount of bending that occurs at a predetermined position in the roller axial direction of the pressing roller 18, the roller body 32 at the central portion in the roller axial direction of the feed roller 17 is gradually removed from the roller main body 32 at both ends in the roller axial direction. If the diameter is reduced, the deflection of the pressure roller 18 can be compensated more accurately, and the pressure roller 18 and the feed roller 17 can be pressed more uniformly.

  FIG. 4 is a schematic plan view showing a registration roller pair 5 according to a third embodiment of the present invention. In this embodiment, a plurality of roller bodies 39 are arranged along the roller shaft 38 to form the feed roller 17, and the roller body 39 at the center in the roller axis direction is made up of the roller bodies 39 at both ends in the roller axis direction. It is characterized in that it is formed of a member having a large friction coefficient, and the gear driving side of the registration roller pair 5 is pressed more strongly in advance than the non-driving side. Since the point where the gear drive side is pressed more strongly than the non-drive side is the same as in the first embodiment, description thereof is omitted here.

  In this embodiment, as shown in FIG. 4A, the pressing roller 18 is installed between the frame members 26, and both end portions of the roller shaft 40 are rotatably supported by a pair of left and right bearings 41. . Further, both ends of the roller shaft 38 of the feed roller 17 are rotatably supported by a pair of left and right bearings 42, and each bearing 42 is biased toward the pressing roller 18 by a pair of left and right biasing springs 43 and 44, respectively. ing. In such a configuration, similarly to the first embodiment, there arises a problem that the nip pressure is lowered at the central portion in the roller axial direction due to the bending of the pressing roller 18. In order to prevent this problem, in this embodiment, three roller main bodies 39 having the same outer diameter are arranged along the roller shaft 38 to form the feed roller 17, and the middle roller main body 39 is moved to the friction body. The coefficient is larger than the left and right roller bodies 39. Thus, the amount of friction generated between the roller main body 39 and the recording paper P is increased and compensated for at the central portion in the roller axial direction as the nip pressure is reduced at the central portion in the roller axial direction. On the other hand, it is possible to apply a uniform conveying force in the width direction. Further, as compared with the first embodiment in which the pressing roller 18 has a crown shape, there is an advantage that labor and cost required for processing the roller can be reduced.

  As shown in FIG. 4B, the feed roller 17 is installed between the frame members 26, and both end portions of the roller shaft 38 are rotatably supported by a pair of left and right bearings 41, while the pressure roller 18 is supported. It is also possible to adopt a configuration in which both ends of the roller shaft 40 are rotatably supported by a pair of left and right bearings 42 and each bearing 42 is biased toward the feed roller 17 by a pair of left and right biasing springs 43 and 44. is there. Also in this case, the three roller main bodies 39 are arranged along the roller shaft 38 to form the feed roller 17, and the middle roller main body 39 is formed from a member having a larger friction coefficient than the left and right roller main bodies 39. By doing so, it is possible to prevent a decrease in the nip pressure at the central portion in the roller axial direction. Further, by urging the gear driving side of the pressing roller 18 toward the feeding roller 17 with a stronger force than the non-driving side, it is possible to prevent a decrease in nip pressure on the gear driving side.

  In this embodiment, the number of roller main bodies 39 of the feed roller 17 is not limited to three, and the design can be changed as appropriate. For example, six roller main bodies 39 are arranged in a row and two roller main bodies 39 in the center are arranged. Can be formed of a member having a friction coefficient larger than that of the other four roller bodies 39. Further, the friction coefficient is gradually increased from the roller main body 39 at the central portion in the roller axial direction of the feed roller 17 toward the roller main bodies 39 at both ends in the roller axial direction in accordance with the amount of deflection generated at a predetermined position in the roller axial direction of the pressing roller 18. If the distance is made smaller, the deflection of the pressing roller 18 can be compensated more accurately, and a uniform conveying force can be applied to the recording paper P in the width direction. Furthermore, it is not an essential requirement of the present invention that a plurality of roller main bodies 39 are arranged along the roller shaft 38. A single long roller main body 39 is provided, and the central portion in the roller axial direction is provided. It is also possible to form a member having a coefficient of friction larger than both ends in the roller axial direction.

  The present invention is also applicable to a copy-only machine having only a copying function and a facsimile-only machine having only a facsimile communication function.

1 is a schematic longitudinal sectional view showing a configuration of an image forming apparatus 1 according to an embodiment of the present invention. 1 is a schematic plan view showing a registration roller pair 5 according to a first embodiment of the present invention. FIG. 6 is a schematic plan view showing a registration roller pair 5 according to a second embodiment of the present invention. FIG. 10 is a schematic plan view showing a registration roller pair 5 according to a third embodiment of the present invention. FIG. 10 is a block diagram illustrating a configuration of an image forming apparatus according to a conventional example. FIG. 10 is a schematic plan view showing a registration roller pair 78 according to a conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 3 Conveyance path 5 Registration roller pair 10 Image transfer position 17 Feed roller 18 Press roller 19, 31, 38 Roller shaft 21 Drive gear 23 Roller shaft 25 Interlocking gear 32, 39 Roller body P Recording paper

Claims (6)

A drive roller is provided at one end in the roller axial direction and a feed roller that feeds the recording paper to the downstream side of the conveyance path, and an interlocking gear that meshes with the drive gear is provided at one end in the roller axial direction to press the recording paper against the feed roller. A pair of registration rollers, which are pressed against each other by pressing both ends of the feed roller in the roller axial direction toward the pressure roller, correct the skew of the recording paper and feed it to the image transfer position. In the image forming apparatus,
The pressing roller has a crown shape that gradually decreases in diameter from the central portion in the roller axial direction toward both ends in the roller axial direction, and one end portion in the roller axial direction on the drive gear side of the feed roller is a roller shaft. An image forming apparatus, wherein the image forming apparatus is more strongly biased toward the pressing roller than the other end in the direction. A drive roller is provided at one end in the roller axial direction and a feed roller that feeds the recording paper to the downstream side of the conveyance path, and an interlocking gear that meshes with the drive gear is provided at one end in the roller axial direction to press the recording paper against the feed roller. A pair of registration rollers, in which both ends of the pressing roller in the axial direction of the pressing roller are pressed against the feeding roller by urging both sides in the axial direction of the pressing roller, correct the skew of the recording paper and feed it to the image transfer position. In the image forming apparatus,
The pressure roller has a crown shape that gradually decreases in diameter from a central portion in the roller axial direction toward both ends in the roller axial direction, and one end portion in the roller axial direction on the interlocking gear side of the pressure roller is a roller shaft. An image forming apparatus, wherein the image forming apparatus is more strongly biased toward the feeding roller than the other end in the direction. A drive roller is provided at one end in the roller axial direction and a feed roller that feeds the recording paper to the downstream side of the conveyance path, and an interlocking gear that meshes with the drive gear is provided at one end in the roller axial direction to press the recording paper against the feed roller. A pair of registration rollers, which are pressed against each other by pressing both ends of the feed roller in the roller axial direction toward the pressure roller, correct the skew of the recording paper and feed it to the image transfer position. In the image forming apparatus,
The feed roller includes a roller shaft and a plurality of roller main bodies arranged along the roller shaft, and the roller main body located at the center in the roller axial direction has a larger diameter than the roller main bodies located at both ends in the roller axial direction. An image forming apparatus, wherein one end portion in the roller axial direction on the drive gear side of the feed roller is urged more strongly toward the pressing roller than the other end portion in the roller axial direction. A drive roller is provided at one end in the roller axial direction and a feed roller that feeds the recording paper to the downstream side of the conveyance path, and an interlocking gear that meshes with the drive gear is provided at one end in the roller axial direction to press the recording paper against the feed roller. A pair of registration rollers, in which both ends of the pressing roller in the axial direction of the pressing roller are pressed against the feeding roller by urging both sides in the axial direction of the pressing roller, correct the skew of the recording paper and feed it to the image transfer position. In the image forming apparatus,
The feed roller includes a roller shaft and a plurality of roller main bodies arranged along the roller shaft, and the roller main body located at the center in the roller axial direction has a larger diameter than the roller main bodies located at both ends in the roller axial direction. In addition, the one end portion in the roller axial direction on the interlocking gear side of the pressing roller is more strongly biased toward the feed roller than the other end portion in the roller axial direction. A drive roller is provided at one end in the roller axial direction and a feed roller that feeds the recording paper to the downstream side of the conveyance path, and an interlocking gear that meshes with the drive gear is provided at one end in the roller axial direction to press the recording paper against the feed roller. A pair of registration rollers, which are pressed against each other by pressing both ends of the feed roller in the roller axial direction toward the pressure roller, correct the skew of the recording paper and feed it to the image transfer position. In the image forming apparatus,
The feed roller is made of a member having a larger central friction coefficient with respect to the recording paper than both ends in the roller axial direction, and one end of the feed roller in the roller axial direction on the drive gear side is in the roller axial direction. An image forming apparatus, wherein the image forming apparatus is more strongly biased toward the pressing roller than the other end. A drive roller is provided at one end in the roller axial direction and a feed roller that feeds the recording paper to the downstream side of the conveyance path, and an interlocking gear that meshes with the drive gear is provided at one end in the roller axial direction to press the recording paper against the feed roller. A pair of registration rollers, in which both ends of the pressing roller in the axial direction of the pressing roller are pressed against the feeding roller by urging both sides in the axial direction of the pressing roller, correct the skew of the recording paper and feed it to the image transfer position. In the image forming apparatus,
The feed roller is formed of a member having a roller axial center portion having a larger coefficient of friction with respect to the recording paper than both ends of the roller axial direction, and one end portion of the pressing roller on the interlocking gear side in the roller axial direction is in the roller axial direction. An image forming apparatus, wherein the image forming apparatus is more strongly biased toward the feed roller than the other end.

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