JP6150144B2 - Sheet feeding roller, sheet feeding and conveying apparatus, and image forming apparatus - Google Patents

Description

  The present invention relates to a sheet feeding roller, a sheet feeding and conveying apparatus, and an image forming apparatus.

  2. Description of the Related Art Conventionally, an image forming apparatus provided with a manual paper feed mechanism having a half-moon-shaped paper feed roller for transporting paper (a printing medium) and a retard roller that rotates passively and spreads paper over a certain torque. It has been known. In the manual paper feed mechanism, the two rollers use a rubber material such as EPDM, and feed paper one by one while rolling the paper with its surface friction and pressure.

  FIG. 7 is a cross-sectional view showing a knurled shape of a conventional paper feed roller. FIG. 8 is a cross-sectional view showing another knurled shape of a conventional paper feed roller. The paper feed roller has a large change in friction coefficient and wear resistance depending on the knurled shape of the roller surface. In general, as shown in FIG. 7, when the knurl 60 is trapezoidal and has a large mountain, or the rigidity of the mountain is high, the wear resistance is excellent, but the conveying force is small. On the other hand, as shown in FIG. 8, when the knurl 61 has a mountain shape and a small mountain, or the rigidity of the mountain portion is low, the tip portion presses against the paper and is crushed to increase the pressure at the tip portion. As the deformation of the sheet increases, the degree of adhesion to the sheet increases and the conveying force increases. However, it is easy to wear and the coefficient of friction tends to decrease.

  By the way, the conveyance force required when conveying a sheet is not always constant. When the paper starts to move, a large transport force is required due to the suction and cutting burr between the papers. However, after the motion starts, it is sufficient that the transport force is such that the surface of the paper feed roller and the paper do not slip.

  Therefore, in order to ensure sheet feeding performance, for example, in Patent Document 1, one end of a continuous end of a linear outer peripheral surface and an arc outer peripheral surface constitutes a pickup portion and the other end is a conveyance end position. In the D-shaped paper feeding roller whose arc-shaped outer peripheral surface is the transport portion, the material or / and the pattern of the transport end portion and the other main transport portion applied from the transport end position to the transport portion of the arc-shaped outer peripheral surface are different, Techniques have been proposed for making the material and pattern at the end of conveyance excellent in wear resistance.

JP 2001-199569 A

  However, the above-described prior art has a problem in that when the material in a portion that comes into contact with the sheet is worn when the sheet starts to move, the sheet feeding roller reaches the end of its life and needs to be replaced.

  Accordingly, an object of the present invention is to extend the substantial component life of the paper feed roller.

  A paper feed roller according to the present invention has an arcuate outer peripheral surface, and feeds the print medium in a predetermined direction by rotating in a state where the arc-shaped outer peripheral surface is in contact with the print medium. When the arc-shaped outer peripheral surface is divided into a first area, a second area, and a third area in order from the conveyance upstream side, the roller is provided in the first area and The first member having a predetermined coefficient of friction and the second region are provided in the second region, and the friction coefficient with respect to the printing medium is smaller than the predetermined value, but the wear resistance is superior to the first member. A second member provided in the third region and having a friction coefficient with respect to the print medium of the predetermined size, and the supply shaft is connected to the drive shaft of the mounting target device. The paper roller can be mounted with the direction of the drive shaft changed. Configured, characterized in that.

  The sheet feeding / conveying device according to the present invention has an arcuate outer circumferential surface, and feeds the printing medium in a predetermined direction by rotating in a state where the arcuate outer circumferential surface is in contact with the printing medium. A paper roller, a retard roller that passes the print medium passively to the paper feed roller, and when the print medium is sent out, the paper feed roller rises in accordance with the timing of starting to rotate the print medium. And a lifter that lifts the medium and makes the leading end of the printing medium abut against the paper feed roller. The paper feed roller has a first region, When the first region is divided into the third region, the first member is provided in the first region, and the first member having a predetermined friction coefficient with respect to the print medium is provided in the second region. The coefficient of friction against the printing medium is A second member that is smaller than a predetermined size but has better wear resistance than the first member, and a third member that is provided in the third region and that has a predetermined friction coefficient with respect to the print medium. And is configured to be mountable on the drive shaft of the mounting target device by changing the direction of the paper feed roller with respect to the axial direction of the drive shaft.

  The image forming apparatus according to the present invention is an image forming apparatus that outputs a print on a printing medium sent out by a paper feeding / conveying device, the paper feeding / conveying device having an arcuate outer peripheral surface, and the printing medium A paper feed roller that feeds the print medium in a predetermined direction by rotating in a state where the arcuate outer peripheral surface is in contact with, and a retard roller that passes the print medium passively to the paper feed roller, A lifter that lifts the print medium by raising the feed roller when the feed medium starts to rotate, and lifts the print medium so that the leading edge of the print medium contacts the feed roller; The paper feed roller is provided in the first area when the arc-shaped outer peripheral surface is divided into a first area, a second area, and a third area in order from the upstream side of conveyance. For print media The conveying force is provided in the first member having a predetermined size and the second region, and the conveying force with respect to the printing medium is smaller than the predetermined size, but has higher wear resistance than the first member. A second member provided in the third region and having a predetermined conveying force with respect to the print medium, the drive shaft of the mounting target device including the second member. The paper roller is configured to be mountable by changing the direction with respect to the axial direction of the drive shaft.

  According to the present invention, the substantial component life of the paper feed roller can be extended.

1 is a cross-sectional view illustrating an internal configuration of an image forming apparatus 1 according to an embodiment of the present invention. 2 is a perspective view illustrating configurations of an image forming apparatus 1 and an MPF tray 40 according to the present embodiment. FIG. It is sectional drawing which shows the partial structure of the MPF tray 40 by this embodiment. It is sectional drawing which shows the knurled shape of the paper feed roller 43 by this embodiment. 6 is a timing chart for explaining a sheet feeding operation by a sheet feeding roller 43 according to the present embodiment. It is a conceptual diagram for demonstrating the paper supply operation | movement by the paper supply roller 43 by this embodiment. It is sectional drawing which shows the shape of the conventional paper feed roller. It is sectional drawing which shows the other shape of the conventional paper feed roller.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an internal configuration of an image forming apparatus 1 according to an embodiment of the present invention. In the figure, the image forming apparatus 1 according to the present embodiment is not a system that directly transfers a toner image onto a sheet (a printing medium), but temporarily transfers the toner image onto an intermediate transfer belt, and then vertically extends to a secondary transfer unit. The toner image is secondarily transferred onto the conveyed paper via an intermediate transfer belt.

  The image forming apparatus 1 includes an image forming unit 2, a duplex printing conveyance unit 3, a paper feeding unit 4, and a fixing unit 5. The image forming unit 2 has a configuration in which four image forming units 6 (6-1, 6-2, 6-3, 6-4) are arranged in a multistage manner. The three image forming units 6-1, 6-2, and 6-3 form a monocolor image using magenta (M), cyan (C), and yellow (Y) color toners that are subtractive three primary colors, respectively. To do. The fourth image forming unit 6-4 following the three image forming units 6-1, 6-2, 6-3 forms a black (K) monochrome image. These four color toner images are overlaid on the paper to form a full color image.

  Each of the image forming units 6-1 to 6-4 has the same configuration except for the color and type of the developer stored in the developing unit. Therefore, the configuration of the image forming unit 6-4 will be described below as an example.

  The image forming unit 6 includes a photosensitive drum 7 at the bottom. The peripheral surface of the photosensitive drum 7 is made of, for example, an organic photoconductive material. A cleaner 8, a charging roller 9, an optical writing head 10, and a developing roller 12 of the developing device 11 are disposed in contact with or around the periphery of the photosensitive drum 7.

  The developing unit 11 is arranged in the upper toner container, as shown by M, C, Y, and K in the drawing, and is one of magenta (M), cyan (C), yellow (Y), and black (K) toners. The intermediate portion is provided with a toner replenishing mechanism for the lower portion.

  Further, the developing roller 12 is provided in the lower side of the developing device 11 in the side opening, and a toner stirring member, a toner supply roller 13 for supplying toner to the developing roller 12, and a toner layer on the developing roller 12 are fixed. A doctor blade that regulates the layer thickness is provided. An optical writing head 10 on the main device side is disposed in the vicinity of the upper surface located between the charging roller 9 and the developing device 11 of the photosensitive drum 7.

  Further, an intermediate transfer belt 14 is disposed in the vicinity of the lower surface of the photosensitive drum 7. The primary transfer roller 15 is pressed toward the lower surface of the photosensitive drum 7 with the intermediate transfer belt 14 interposed therebetween.

  The intermediate transfer belt 14 is made of a conductive sheet-like member made of resin containing conductive carbon or an ion conductive substance, and has a flat loop shape from substantially the left and right sides of the figure at the center of the main unit. This is an endless transfer belt that extends. It is stretched over the drive roller 16 and the driven roller 17 and is circulated and driven counterclockwise in the figure by the drive roller 16, and circulates in the counterclockwise direction indicated by arrows a, b, and c in the figure.

  The photosensitive drum 7 rotates in the clockwise direction in the figure. First, by applying charge from the charging roller 9, the peripheral surface of the photosensitive drum 7 is uniformly charged and initialized. Next, an electrostatic latent image is formed on the peripheral surface of the photosensitive drum 7 by optical writing from the optical writing head 10 based on the print information.

  The electrostatic latent image is converted into a toner image (development) by the toner stored in the developing device 11 by the developing process by the developing roller 12. The toner image developed on the peripheral surface of the photosensitive drum 7 is directly transferred (primary transfer) to the belt surface of the intermediate transfer belt 14 by the primary transfer roller 15 as the photosensitive drum 7 rotates. The intermediate transfer belt 14 conveys the toner image transferred (primary transfer) directly onto the belt surface to a transfer position to the sheet 22 for further transfer (secondary transfer) to the sheet 22.

  The belt position control mechanism 18 includes a primary transfer roller 15 made of a conductive foam sponge that presses against the lower peripheral surface of the photosensitive drum 7 via the intermediate transfer belt 14. The belt position control mechanism 18 includes three primary transfer rollers 15 corresponding to the three image forming units 6-1, 6-2, and 6-3 of magenta (M), cyan (C), and yellow (Y). Three cranks are simultaneously moved up and down synchronously by a crank and a slider-cam mechanism by rotation of a drive shaft (not shown). Then, the belt position control mechanism 18 causes the one primary transfer roller 15 corresponding to the black (K) image forming unit 6-4 to have the same cycle as the cycle of the three primary transfer rollers 15 but at different timings. The intermediate transfer belt 14 is moved up and down to be separated from the photosensitive drum 7.

  That is, the belt position control mechanism 18 corresponds to the position of the intermediate transfer belt 14 in the full color mode (all four primary transfer rollers 15 are in contact with the intermediate transfer belt 14) and the monochrome mode (image forming unit 6-4). Only the primary transfer roller 15 is in contact with the intermediate transfer belt 14) and all non-transfer modes (all four primary transfer rollers 15 are separated from the intermediate transfer belt 14).

  The paper feed unit 4 includes two paper feed cassettes 21 arranged in two upper and lower stages. A large number of cut sheets 22 are accommodated in one or both of the sheet feed cassettes 21 of the sheet feed unit 4. A paper feed roller 23, a retard roller 24, a feed roller 25, a separating roller 26, and a standby transport roller pair 27 are arranged near the paper feed port (right side of the drawing) of the two paper feed cassettes 21, respectively. .

  The paper 22 is unloaded from the paper feed cassette 21 one by one by the paper feed roller 23 and the retard roller 24 by one rotation of the half-moon-shaped paper feed roller 23, and passes through the feed roller 25 and the separating roller 26. It is fed to the standby conveyance roller pair 27. Alternatively, when the thickness or size of the paper 22 is unusual, the paper 22 is rotated from the MPF (Multi Paper Feeder) tray 40 mounted on the opened mounting portion by one rotation of the half-moon-shaped paper feeding roller 43. The sheet feeding roller 43 and the retard roller 44 feed to the standby conveyance roller pair 27 through a terminal return path 34c and a return roller pair 35a described later. On the left and right side surfaces of the MPF tray 40, side regulating plates 41 are provided that can move in the lateral direction according to the width of the paper 22 in order to prevent lateral displacement of the paper 22 accommodated therein.

  A secondary transfer roller 30 that is in pressure contact with the driven roller 17 via the intermediate transfer belt 14 is disposed in the paper conveyance direction (vertical upward direction in the drawing) of the standby conveyance roller pair 27. The intermediate transfer belt 14, the driven roller 17, and the secondary transfer roller 30 form a secondary transfer portion to the paper 22.

  A fixing unit 5 composed of a belt-type heat fixing unit is disposed downstream (upward in the drawing) of the secondary transfer unit. On the further downstream side of the fixing unit 5, a pair of discharge rollers 31 that discharges the fixed sheet from the fixing unit 5 and a pair of discharge rollers that discharge the discharged sheet to a discharge tray 32 formed on the upper surface of the apparatus. 33 is arranged.

  The duplex printing conveyance unit 3 includes a return path that branches in the right lateral direction in the drawing from an intermediate conveyance path between the carry-out roller pair 31 and the paper discharge roller pair 33. This return path includes a start return path 34a, an intermediate return path 34b that bends downward, a terminal return path 34c that bends in the left lateral direction and finally reverses the return sheet, and four sets arranged in the middle of these return paths. A pair of return rollers 35a, 35b, 35c, and 35d is provided. The exit of the end return path 34 c communicates with a conveyance path to the pair of standby conveyance rollers 27 corresponding to the sheet feeding cassette 21 below the sheet feeding unit 4.

  FIG. 2 is a perspective view illustrating configurations of the image forming apparatus 1 and the MPF tray (manual paper feed mechanism) 40 according to the present embodiment. In the following, the paper feed roller 43 in the MPF tray 40 will be described, but the present invention is not limited to this, and can also be applied to the paper feed roller 23 of the paper feed cassette 21.

  Side restriction plates 41 are provided on the left and right side surfaces of the MPF tray 40. The side regulating plate 41 is movable in the horizontal direction in accordance with the width of the paper 22 in order to prevent the paper 22 placed on the MPF tray 40 from shifting in the horizontal direction. The paper feed roller 43 is installed at substantially the center of the MPF tray 40 and conveys the paper 22 placed on the MPF tray 40 into the image forming apparatus 1 so as to be sandwiched between the retard roller 44 (not shown).

  FIG. 3 is a sectional view showing a partial structure of the MPF tray 40 according to the present embodiment. FIG. 4 is a cross-sectional view showing the knurled shape of the paper feed roller 43 according to the present embodiment. In FIG. 3, parts corresponding to those in FIGS. 1 and 2 are denoted by the same reference numerals. The paper feed roller 43 has a half-moon shape (D shape) in cross section, and is detachably fixed to the drive shaft 46. In other words, the paper feed roller 43 is a hollow cylinder, and has a slit portion on the side surface so as to connect U-shaped cutout portions formed on both end surfaces, and is pressed against the drive shaft 46 by being pressed against the drive shaft 46. It can be fitted and fixed (fixed), and can be removed from the drive shaft 46 by being pulled out from the drive shaft 46. When the paper feed roller 43 is fitted to and attached to the drive shaft 46, the paper feed roller 43 is rotated integrally with the drive shaft 46 by a rotation stopper (not shown). Further, knurls 43 a to 43 c having irregularities are formed on the outer peripheral surface of the paper feed roller 43 (the outer peripheral curved surface corresponding to the curved portion in the half-moon shape).

  As described above, the transport force required when transporting the paper 22 is not always constant. When the sheet 22 starts to move, a large conveying force is required due to the adsorption and cutting burr between the sheets 22, but after the sheet 22 starts moving, a conveying force that does not cause the outer peripheral surface of the sheet feeding roller 43 and the sheet 22 to slip. I just need it. Therefore, in the present embodiment, the knurl 43a that is in contact with the paper when it starts to move, which requires a large conveying force, has a chevron shape with a predetermined coefficient of friction necessary for the movement of the paper. A trapezoidal knurl 43b having a friction coefficient is brought into contact after the paper starts moving. Further, a chevron-shaped knurl 43c having a predetermined coefficient of friction is also provided on the outer peripheral surface of the paper feed roller 43 on the side opposite to the knurl 43a. When the paper feed roller 43 is mounted as shown in the drawing, the knurl 43c does not wear even if it faces the lifter 45 side by rotation of the paper feed operation as will be described later, because the lifter 45 is lowered. Instead, once the paper feed roller 43 is removed, the direction of the drive shaft 46 is changed with respect to the axial direction, and the paper roller 43 is mounted again.

  In the present embodiment, when the knurl 43a is worn out and reaches the end of its life, the paper feed roller 43 is temporarily removed so that the unused knurl 43c comes into contact with the paper 22, and the direction is changed with respect to the axial direction of the drive shaft 46. It is possible to install. That is, the orientation of the paper feed roller 43 can be changed and mounted so that the knurl 43c is positioned in the region where the knurl 43a is provided. As described above, when the knurl 43a is worn, the D-shaped feed roller 43 can be immediately reused by mounting it in a horizontally reversed manner with respect to the feeding direction of the paper 22, and the substantial component life can be extended. it can.

  The lifter 45 is installed so that it can be raised / lowered in the direction of the arrow by a cam (not shown) in synchronization with the rotation of the paper feed roller 43. When the lifter 45 sends out the paper 22 placed on the MPF tray 40, the lifter 45 rises at the timing when the paper feed roller 43 starts to drive clockwise, lifts the paper 22, and feeds the leading end of the paper 22 The roller 43 is brought into contact. The lifted paper 22 is sandwiched between the paper feed roller 43 and the retard roller 44 and conveyed to the inside of the image forming apparatus 1 by the rotation of the paper feed roller 43. The lifter 45 holds the raised position until the paper 22 is transported by a predetermined amount by the paper feed roller 43. When the paper 22 is transported by a predetermined amount and delivered to the internal transport roller, the lifter 45 is lowered to the original position. It comes to return to the position.

  FIG. 5 is a timing chart for explaining the sheet feeding operation by the sheet feeding roller 43 according to the present embodiment. FIG. 6 is a conceptual diagram for explaining a sheet feeding operation by the sheet feeding roller 43 according to the present embodiment.

  First, when the paper feeding operation has not started, as shown in FIG. 6A, the paper feeding roller 43 is in an initial state where it is not rotating, and the lifter 45 is in the lowered initial position. When the paper feeding operation starts, the paper feeding roller 43 (paper feeding clutch) is turned on at time t1 in FIG. 5, and immediately thereafter, the lifter 45 is raised at time t2. At this time, as shown in FIG. 6B, the paper feed roller 43 starts to rotate clockwise, and the end of the paper 22 placed on the MPF tray 40 is lifted by the lifter 45 that has been lifted to feed the paper. A nip (contact) is formed between the roller 43 and the paper 22. At this time, since the sheet 22 starts moving, a chevron shape having a high conveying force is formed, that is, the knurled 43a having a predetermined coefficient of friction necessary for starting the sheet movement is in contact. The sheet 22 is conveyed into the image forming apparatus 1 by the knurling 43a. This corresponds to times t2 to t3 shown in FIG.

  Further, when the paper feed roller 43 rotates, as shown in FIG. 6C, a trapezoidal shape having a small conveying force is formed, that is, a knurl 43b having a friction coefficient smaller than that of the knurl 43a is in contact with the paper 22. At this time, since the sheet 22 has started to move, it is a stage where relatively little conveyance force is required. This corresponds to times t3 to t4 shown in FIG. The sheet 22 is further conveyed into the image forming apparatus 1.

  Then, when the end portion of the sheet 22 comes into contact with the conveying roller (return roller pair 35d in FIG. 1) inside the image forming apparatus 1 and is conveyed by the conveying roller, as shown in FIG. 6D. The lifter 45 is lowered. This corresponds to time t4 shown in FIG. At this time, the paper feed roller 43 continues to rotate, but the lifter 45 is lowered, so that the pressing force from the lifter 45 to the paper feed roller 43 is eliminated. For this reason, the knurled 43c formed with the chevron shape contacts the paper 22, but does not wear significantly. This corresponds to the times t4 to t5 shown in FIG.

  At time t5, the paper feed roller 43 (paper feed clutch) is turned off and stopped. The sheet 22 is transported by transport rollers (return roller pair 35d in FIG. 1) inside the image forming apparatus 1. This corresponds to the times t5 to t6 shown in FIG. Thereafter, in order to transport the next sheet 22, the times t6 to t11 are repeated similarly to the times t1 to t5 described above.

  According to the above-described embodiment, the outer peripheral surface of the paper feed roller 43 that contacts the paper 22 at the initial stage when the paper 22 starts to move has a high conveying force, that is, a chevron-shaped knurl having a predetermined friction coefficient necessary for the paper to start moving. 43a is provided, and the conveying force is small on the outer peripheral surface of the paper feed roller 43 that comes into contact with the paper 22 after the paper 22 starts to move, that is, the friction coefficient is smaller than that of the knurling 43a, but the wear resistance is excellent. A trapezoidal knurling 43b is provided, and a chevron-shaped knurling 43c is provided on the outer surface of the paper feed roller 43 on the opposite side of the knurling 43a as in the case of the knurling 43a. The paper roller 43 is reversed left and right with respect to the feeding direction of the paper 22, that is, it can be mounted by changing the direction with respect to the rotation axis direction. In, can be immediately becomes reusable, extending the substantial part life.

  Further, according to the above-described embodiment, the knurls 43a and 43c have a chevron shape having a large conveying force with respect to the paper 22, that is, a predetermined friction coefficient, and the knurl 43b has a small conveying force with respect to the paper 22, that is, the knurl 43a. 43c, which has a friction coefficient smaller than that of 43c, but has a trapezoidal shape with excellent wear resistance. Therefore, when the knurl 43a is worn out and reaches the end of its life, the paper feed roller 43 is reversed left and right with respect to the feeding direction of the paper 22. In other words, by replacing the orientation with respect to the direction of the rotation axis, it can be reused immediately, and the substantial component life can be extended.

  Further, according to the above-described embodiment, the knurl 43c contacts the paper 22, but the pressing force from the lifter 45 does not work and does not wear significantly. Since the paper roller 43 is reversed left and right with respect to the feeding direction of the paper 22, that is, the orientation is changed with respect to the rotation axis direction, the paper roller 43 can be immediately reused, and the substantial component life can be extended. it can.

  In the above-described embodiment, the cross section of the knurls 43a and 43c has a mountain shape, and the cross section of the knurl 43b has a trapezoidal shape. (Diagonal, flat eye, iris eye, etc.) may be changed. As described above, even if the fineness of the protrusions and the direction of the protrusions (oblique, flat, eyelet, etc.) are changed, the substantial component life can be extended.

  In the above-described embodiment, the knurling 43a, 43b, and 43c having different shapes are provided on the outer peripheral surface of the paper feed roller 43 (the outer peripheral curved surface corresponding to the curved portion in the half-moon shape). Different materials (rubber, resin, etc.) may be provided. As described above, even if the paper feed roller 43 is made of materials having different rigidity, the substantial component life can be extended.

As mentioned above, although several embodiment of this invention was described, this invention is not limited to these, The invention described in the claim, and its equal range are included.
Below, the invention described in the claims of the present application is appended.

(Appendix 1)
The invention according to appendix 1 has a paper feed roller that has an arc-shaped outer peripheral surface and feeds the print medium in a predetermined direction by rotating in a state where the arc-shaped outer peripheral surface is in contact with the print medium. When the arc-shaped outer peripheral surface is divided into a first area, a second area, and a third area in order from the conveyance upstream side, the friction is provided on the print medium provided in the first area. The first member having a predetermined coefficient and the second region are provided in the second region, and the friction coefficient with respect to the printing medium is smaller than the predetermined size, but the wear resistance is superior to the first member. A second member provided in the third region, and a third member having a predetermined friction coefficient with respect to the print medium. The roller can be mounted with its orientation changed with respect to the axial direction of the drive shaft. It is a paper feed roller, characterized in that.

(Appendix 2)
According to the second aspect of the invention, the first member and the third member include a first knurl having a shape having a predetermined coefficient of friction with respect to the printing medium, and the second member. Additional member 1 is characterized in that it is composed of a second knurl having a shape that has a friction coefficient with respect to the printing medium smaller than the predetermined size, but has a better wear resistance than the first knurl. The sheet feeding roller described in 1.

(Appendix 3)
The invention according to appendix 3 is characterized in that the first knurl has a chevron shape in cross section, and the second knurl has a trapezoidal shape in cross section. It is a paper roller.

(Appendix 4)
In the invention according to attachment 4, the first member and the third member are made of the same material, and the second member is made of a material different from that of the first member and the third member. The paper feed roller according to any one of appendices 1 to 3, wherein

(Appendix 5)
According to the fifth aspect of the present invention, the first member contacts the printing medium when the printing medium starts to be fed, and the second member prints the printing medium when the printing medium is fed by a predetermined amount. The sheet feeding according to any one of appendices 1 to 4, wherein the sheet is in contact with a medium, and the third member is in contact with the medium to be printed after being sent out by the second member. Laura.

(Appendix 6)
The invention according to appendix 6 has an arc-shaped outer peripheral surface, and feeds the print medium in a predetermined direction by rotating in a state where the arc-shaped outer peripheral surface is in contact with the print medium. And a retard roller that passes the print medium passively to the paper feed roller, and when the print medium is sent out, the paper feed roller is raised in accordance with the timing of starting to rotate the print medium. And a lifter that lifts the front end of the printing medium into contact with the paper feed roller, and the paper feed roller has a first area and a second area in order from the upstream side of the arcuate outer circumferential surface. , When divided into the third region, the first member is provided in the first region, the first member having a predetermined coefficient of friction with respect to the print medium, and the second region, and the print target The coefficient of friction against the medium is the predetermined large value. A second member having a wear resistance superior to that of the first member, and a third member provided in the third region and having a predetermined coefficient of friction with respect to the printing medium. , And is configured to be mounted on the drive shaft of the apparatus to be mounted by changing the orientation of the paper feed roller with respect to the axial direction of the drive shaft.

(Appendix 7)
According to the seventh aspect of the invention, at the start of sending out the printing medium, the lifter is lifted to lift the printing medium, and the first printing medium is in contact with the paper feeding roller. The member is brought into contact with the medium to be printed and the paper feed roller is rotationally driven. After the medium to be printed is sent out by a predetermined amount, the medium to be printed is brought into contact with the paper feed roller by the lifter. Then, the second member is brought into contact with the printing medium, the rotation of the paper feed roller is continued, and when the predetermined amount of feeding of the printing medium by the second member is completed, the lifter is 7. The sheet feeding / conveying device according to appendix 6, wherein the rotation driving of the sheet feeding roller is continued in a state where the pressure applied to the sheet feeding roller from the lifter is released.

(Appendix 8)
The invention according to appendix 8 is an image forming apparatus that prints out a printing medium sent out by a paper feeding / conveying device, wherein the paper feeding / conveying device has an arcuate outer peripheral surface, and the printing medium includes A paper feed roller that feeds the print medium in a predetermined direction by rotating in a state in which the arcuate outer peripheral surface is in contact; a retard roller that passes the print medium passively to the paper feed roller; A lifter that lifts the print medium when the print medium is sent out in accordance with the timing at which the paper feed roller starts to rotate, and lifts the print medium in contact with the paper feed roller; And the paper feeding roller is provided in the first area when the arcuate outer peripheral surface is divided into a first area, a second area, and a third area in order from the upstream side of conveyance. Conveying power for printing media The first member having a predetermined size and the second region are provided in the second region, and the conveying force to the print medium is smaller than the predetermined size, but the wear resistance is superior to the first member. 2 and a third member that is provided in the third region and has a predetermined conveying force with respect to the print medium, and the feed roller is provided on the drive shaft of the mounting target device. The image forming apparatus is configured to be mountable by changing a direction with respect to an axial direction of the drive shaft.

(Appendix 9)
According to the ninth aspect of the present invention, when the printing medium starts to be fed, the lifter is lifted to lift the printing medium, and the first medium is in contact with the paper feeding roller. In the state where the printing medium is brought into contact with the paper feeding roller by rotating the paper feeding roller and the printing medium is sent out, the lifter is brought into contact with the paper feeding roller. The second member is brought into contact with the printing medium, the rotation of the paper feed roller is continued, and the lifter is lowered when a predetermined amount of feeding of the printing medium by the second member is completed. The image forming apparatus according to appendix 8, further comprising control means for continuing the rotational drive of the paper feed roller in a state in which the pressing force from the lifter to the paper feed roller is eliminated. is there.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Image forming part 3 Duplex printing conveyance unit 4 Paper feed part 5 Fixing part 6 (6-1, 6-2, 6-3, 6-4) Image forming unit 7 Photosensitive drum 8 Cleaner 9 Charging Roller 10 Optical writing head 11 Developer 12 Developing roller 13 Toner supply roller 14 Intermediate transfer belt 15 Primary transfer roller 16 Drive roller 17 Driven roller 18 Belt position control mechanism 21 Paper feed cassette 22 Paper (printed medium)
23, 43, 43a Feed roller 24, 44 Retard roller 25 Feed roller 26 Rolling roller 27 Standby transport roller pair 30 Secondary transfer roller 31 Unload roller pair 32 Discharge tray 33 Discharge roller pair 34a Start return path 34b Intermediate return Road 34c Terminal return path 35a, 35b, 35c, 35d Return roller pair 40 MPF (Multi Paper Feeder) tray 41 Side regulating plate 43a, 43b, 43c Knurl 45 Lifter 46 Drive shaft

Claims (9)

A paper feed roller that has an arcuate outer peripheral surface and feeds the print medium in a predetermined direction by rotating the arcuate outer peripheral surface in contact with the print medium;
When the arc-shaped outer peripheral surface is divided into a first region, a second region, and a third region in order from the conveyance upstream side,
A first member provided in the first region and having a predetermined coefficient of friction with respect to the printing medium;
A second member that is provided in the second region and has a friction coefficient with respect to the printing medium smaller than the predetermined size, but has better wear resistance than the first member;
A third member provided in the third region and having a predetermined coefficient of friction with respect to the print medium;
With
The paper feed roller is configured to be mountable on the drive shaft of the mounting target device by changing the direction with respect to the axial direction of the drive shaft.
A paper feed roller characterized by that. The first member and the third member include a first knurl having a shape having a predetermined coefficient of friction with respect to the printing medium,
The second member is composed of a second knurl having a shape with a friction coefficient with respect to the printing medium smaller than the predetermined size, but having a wear resistance superior to that of the first knurl.
The paper feed roller according to claim 1. The first knurl has a chevron shape in cross section;
The second knurl has a trapezoidal cross section.
The paper feed roller according to claim 2. The first member and the third member are made of the same material,
The second member is made of a material different from that of the first member and the third member.
The paper feed roller according to any one of claims 1 to 3, wherein the paper feed roller is provided. The first member contacts the printing medium at the start of sending out the printing medium;
The second member is in contact with the printing medium when the printing medium is fed a predetermined amount,
The third member contacts the printing medium after being sent out by the second member.
The sheet feeding roller according to claim 1, wherein the sheet feeding roller is a sheet feeding roller. A paper feed roller that has an arcuate outer peripheral surface and feeds the print medium in a predetermined direction by rotating the arcuate outer peripheral surface in contact with the print medium;
A retard roller for passing the print medium passively to the paper feed roller;
A lifter that lifts the print medium by raising the feed roller when the feed medium starts to rotate, and lifts the print medium so that the leading edge of the print medium contacts the feed roller; With
The paper feed roller is
When the arc-shaped outer peripheral surface is divided into a first region, a second region, and a third region in order from the conveyance upstream side,
A first member provided in the first region and having a predetermined coefficient of friction with respect to the printing medium;
A second member that is provided in the second region and has a friction coefficient with respect to the printing medium smaller than the predetermined size, but has better wear resistance than the first member;
A third member provided in the third region and having a predetermined coefficient of friction with respect to the printing medium;
With
The paper feed roller is configured to be mountable on the drive shaft of the mounting target device by changing the direction with respect to the axial direction of the drive shaft.
A sheet feeding and conveying apparatus characterized by that. At the start of sending out the printing medium, the lifter is lifted to lift the printing medium, and the first member is placed on the printing medium in a state where the printing medium is in contact with the paper feed roller. Drive the paper feed roller in contact with it,
After said print medium is Ri out feed, in a state where the printing medium is brought into contact with the paper feed roller by the lifter, the paper feed roller the second member in contact with the print medium Continue to drive,
When the feeding of the predetermined amount of the printing medium by the second member is completed, the lifter is lowered, and the pressing force from the lifter to the paper feed roller is eliminated, and the paper feed roller Further comprising control means for continuing the rotational drive,
The sheet feeding / conveying apparatus according to claim 6. An image forming apparatus for printing out on a printing medium sent out by a paper feeding and conveying device,
The paper feeding and conveying device is
A paper feed roller that has an arcuate outer peripheral surface and feeds the print medium in a predetermined direction by rotating the arcuate outer peripheral surface in contact with the print medium;
A retard roller for passing the print medium passively to the paper feed roller;
A lifter that lifts the print medium by raising the feed roller when the feed medium starts to rotate, and lifts the print medium so that the leading edge of the print medium contacts the feed roller; With
The paper feed roller is
When the arc-shaped outer peripheral surface is divided into a first region, a second region, and a third region in order from the conveyance upstream side,
A first member which is provided in the first region and has a predetermined magnitude of conveying force with respect to the printing medium;
A second member which is provided in the second region and has a transport force for the printing medium smaller than the predetermined size, but has better wear resistance than the first member;
A third member which is provided in the third region and has a predetermined conveying force with respect to the printing medium;
With
The paper feed roller is configured to be mountable on the drive shaft of the mounting target device by changing the direction with respect to the axial direction of the drive shaft.
An image forming apparatus. At the start of sending out the printing medium, the lifter is lifted to lift the printing medium, and the first member is placed on the printing medium in a state where the printing medium is in contact with the paper feed roller. Drive the paper feed roller in contact with it,
After the printing medium is sent out, the second member is brought into contact with the printing medium while the printing medium is brought into contact with the feeding roller by the lifter, and the feeding roller is rotated. Continue driving,
When the feeding of the predetermined amount of the printing medium by the second member is completed, the lifter is lowered, and the pressing force from the lifter to the paper feed roller is eliminated, and the paper feed roller Further comprising control means for continuing the rotational drive,
The image forming apparatus according to claim 8.

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