JP2019094166A - Sheet feed device and image formation apparatus - Google Patents

Abstract

To suppress slipping on a sheet with time and jamming due to variation in roller diameter from being caused through stable sheet separating operation even when high calcium carbide paper is used.SOLUTION: The present invention relates to a sheet feed device having separating conveyance means for separating and conveying sheets, fed from a loading part, one by one. The separating conveyance means has a feed roller 220 which rotates in a feed direction of sheets, and a separating roller 230 which can be pressed against the feed roller with a sheet interposed. The feed roller 220 and separating roller 230 are made different in apparent hardness so as to make a nip shape of a press-contact part where both the rollers are pressed against each other concave to the feed roller side.SELECTED DRAWING: Figure 3

Description

The present invention relates to a sheet feeding device and an image forming apparatus provided with the sheet feeding device.

In an image forming apparatus such as a copying machine or a printer, separation and conveyance means such as FRR separation and FR separation are provided to separate and feed sheets one by one from a sheet bundle stacked in a sheet feeding tray. . In FRR separation, a separation roller (return roller) to which a fixed amount of torque is applied in the reverse sheet feeding direction via a torque limiter is brought into pressure contact with the feed roller, and the sheet is separated at the nip between the rollers. In FR separation, a separation roller (friction roller) supported on a fixed shaft is brought into pressure contact with a feed roller via a torque limiter to separate sheets at a nip between the rollers.

By the way, in recent years, the tendency to change the paper, which is a recording medium used in the image forming apparatus, to calcium carbonate paper (hereinafter referred to as "carbonized paper") is intensified for cost reduction and environmental resistance. Although this charcoal kar paper is a paper in which a large amount of calcium carbonate (hereinafter referred to as "charcoal kar") is blended instead of pulp, when this high charcoal kar paper is used, the coal karl which falls off from the paper on the roller of the separation conveyance means Easily adheres and deposits. As a result, the frictional force of the roller decreases over time, and jamming due to paper feeding failure (non-feeding) or double feeding tends to occur.

In order to solve such problems, it has been proposed to make the hardness of the rubber of the feed roller different from the hardness of the rubber of the separation roller (return roller, friction roller) in pressure contact with the feed roller. For example, in the invention of Patent Document 1 (Japanese Patent No. 3633658), it is proposed to make the rubber hardness of the separation roller harder than the rubber hardness of the feeding roller. In this way, the slippage of the separation roller is suppressed to prevent the scattering and adhesion of carbon dust, and the jamming is prevented by facilitating the rotation with the feed roller.

However, in the invention of Patent Document 1 (Japanese Patent No. 3633658), the rubber hardness is made different by making the rubber material of the feed roller and the rubber material of the separation roller different in material value. For this reason, when the rubber hardness changes due to environmental factors such as temperature and humidity and the roller wear amount changes with time, there is a possibility that the occurrence of jam can not be effectively prevented.

In addition, with the passage of time, the liquid component of rubber may move from the feed roller to the separation roller or from the separation roller to the feed roller, and the volume of the roller on the side to which the liquid component is moved may increase. There is also. When this swelling occurs, a change in the roller diameter causes a change in the sheet conveyance amount, or a change in the inter-roller gap, and thus the jamming tends to occur.

The present invention has been made in view of such a situation, and even when using high charcoal kar paper due to a stable paper separating action, a slip occurs with the paper over time, and a jam occurs due to a change in roller diameter. It is an object of the present invention to provide a sheet feeding apparatus which suppresses the occurrence of

In order to solve the above-mentioned problems, a sheet feeding apparatus according to the present invention has a sheet feeding apparatus having separating and conveying means for separating and conveying the sheet materials fed from the loading unit on which the sheet materials are loaded one by one. The separating and conveying means includes a feeding roller which rotates in the feeding direction of the sheet material, and a separating roller which can be in pressure contact with the feeding roller with the sheet material interposed therebetween, the feeding roller The nip shape of the press-contact portion where the feed roller and the separation roller are in pressure contact with each other is made concave toward the feed roller side by making the apparent hardness of the separation roller different. .

According to the present invention, by making the apparent hardness of the feeding roller and the separating roller different, the nip shape is made concave toward the feeding roller side, so a stable paper separating action can be obtained, and the passage of time It is possible to suppress the occurrence of a slip with a sheet and the occurrence of a jam due to a change in roller diameter.

FIG. 1 is a schematic view of an image forming apparatus according to an embodiment of the present invention. FIG. 1 is a perspective view of a sheet feeding device according to an embodiment of the present invention. FIG. 2 is a side view of the sheet feeding device according to the embodiment of the present invention. (A) of the roller pair used for the sheet feeding apparatus according to the first embodiment of the present invention is a non-pressurized state, and (b) is a side view of a pressurized state. (A) of the feed roller of the roller pair used in the sheet feeding apparatus according to the second embodiment of the present invention is an assembled perspective view, (b) is an exploded perspective view, (c) and (d) are the feed rollers. It is a side view of a used roller pair. (A) of the feed roller of the roller pair used in the sheet feeding apparatus according to the third embodiment of the present invention is an assembled perspective view, (b) is an exploded perspective view, (c) and (d) are the feed rollers. It is a side view of a used roller pair. (A) of the feed roller of the roller pair used in the sheet feeding apparatus according to the fourth embodiment of the present invention is an assembled perspective view, (b) is an exploded perspective view, (c) and (d) are the feed rollers. It is a side view of a used roller pair.

Hereinafter, a sheet feeding apparatus according to an embodiment of the present invention and an image forming apparatus (laser printer) including the sheet feeding apparatus will be described with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the redundant description thereof will be appropriately simplified or omitted. Further, dimensions, materials, shapes, relative arrangements and the like in the description of each component are only examples, and the scope of the present invention is not limited to them unless specifically described.

In the following embodiments, "sheet material" will be described as "paper". However, the "sheet material" is not limited to paper. The “sheet material” includes not only paper (paper) but also OHP sheets, fabrics, metal sheets, plastic films, or prepreg sheets in which a carbon fiber is impregnated with a resin in advance.

Media referred to as developer, ink, etc., recording media, recording paper, recording sheets, etc. are all included in the "sheet material". In addition to plain paper, "paper" also includes thick paper, postcards, envelopes, thin paper, coated paper (coated paper, art paper, etc.), tracing paper and the like.

In addition, “image formation” used in the following description means not only the addition of an image having a meaning such as characters and figures to a medium, but also the addition of an image having no meaning such as a pattern to a medium Also mean.

(Configuration of laser printer)
FIG. 1 is a block diagram schematically showing the configuration of a color laser printer as an embodiment of an image forming apparatus provided with the sheet feeding apparatus of the present invention. The color laser printer 100 includes four process units 1K, 1Y, 1M and 1C as image forming means. These process units form an image with developers of respective colors of black (K), yellow (Y), magenta (M) and cyan (C) corresponding to color separation components of a color image.

Each of the process units 1K, 1Y, 1M, and 1C has the same configuration except that it has toner bottles 6K, 6Y, 6M, and 6C containing different colors of unused toner. Therefore, the configuration of one process unit 1K will be described below, and description of the configuration of the other process units 1Y, 1M and 1C will be omitted.

The process unit 1K includes an image carrier 2K (for example, a photosensitive drum), a drum cleaning device 3K, and a charge removing device. The process unit 1K further includes a charging device 4K as charging means for uniformly charging the surface of the image carrier, and a developing device as a developing means for performing visible image processing of the electrostatic latent image formed on the image carrier. It has 5K and so on. The process unit 1K is detachably mounted to the main body of the laser printer 100, and consumable parts can be replaced simultaneously.

The exposure unit 7 is disposed above the process units 1K, 1Y, 1M, and 1C installed in the laser printer 100. The exposure unit 7 is configured to emit a laser beam from the laser diode based on the writing scan corresponding to the image information, that is, the image data.

The transfer device 15 is disposed below the process units 1K, 1Y, 1M, and 1C in this embodiment. The primary transfer rollers 19 K, 19 Y, 19 M, 19 C are disposed in contact with the intermediate transfer belt 16 so as to face the image carriers 2 K, 2 Y, 2 M, 2 C.

The intermediate transfer belt 16 circulates in a state of being wound around the respective primary transfer rollers 19 K, 19 Y, 19 M, 19 C, the driving roller 18 and the driven roller 17. The secondary transfer roller 20 is disposed opposite to the drive roller 18 and in contact with the intermediate transfer belt 16. When the image carriers 2K, 2Y, 2M, and 2C are the first image carriers of the respective colors, the intermediate transfer belt 16 is a second image carrier obtained by combining those images.

The belt cleaning device 21 is disposed downstream of the secondary transfer roller 20 in the traveling direction of the intermediate transfer belt 16. In addition, a cleaning backup roller is installed on the opposite side of the intermediate transfer belt 16 to the belt cleaning device 21.

A sheet feeding tray 50 having a stacking unit for stacking sheet materials is disposed below the laser printer 100, and can store a large number of sheets P in a bundle. The paper feed tray 50 is insertable into and removable from the main body of the laser printer 100 for the purpose of paper supply and the like. The sheet feeding roller 60 and the roller pair 210 as conveying means are disposed above the sheet feeding tray 50 in the state of being installed in the laser printer 100, and the uppermost sheet P of the sheet feeding tray 50 is fed from the sheet feeding tray 50. The paper is transported toward the paper path 32.

The pair of registration rollers 250 as separating and conveying means is disposed immediately upstream of the secondary transfer roller 20 in the conveying direction, and can temporarily stop the sheet P fed from the sheet feeding tray 50. A slack is formed on the leading end side of the sheet P by this temporary stop.

A registration sensor 31 is disposed immediately upstream of the registration roller pair 250 in the conveyance direction, and the registration sensor 31 detects passage of the leading end of the sheet. After the registration sensor 31 detects the passage of the leading end of the sheet, when a predetermined time elapses, the sheet is abutted against the pair of registration rollers 250 and is temporarily stopped.

The sheet feeding roller 60 and the roller pair 210 are disposed in the unitized sheet feeding apparatus 200 as shown in FIGS. 2A and 2B. At the downstream end of the sheet feeding apparatus 200, as shown in FIG. 2B, a conveyance roller 240 for conveying the sheet conveyed to the right from the roller pair 210 upward is disposed. As shown in FIG. 1, the conveyance roller 240 conveys the sheet toward the upper registration roller pair 250.

The roller pair 210 is configured by a pair of upper and lower rollers. The roller pair 210 can be an FRR separation system or an FR separation system. In the FRR separation method, a separation roller (return roller) to which a fixed amount of torque is applied in the reverse sheet feeding direction via a torque limiter by a drive shaft is brought into pressure contact with the feeding roller to separate sheets at the nip between the rollers. In the FR separation method, a separation roller (friction roller) supported on a fixed shaft is brought into pressure contact with a feed roller via a torque limiter to separate sheets at a nip between the rollers.

In this embodiment, the roller pair 210 is configured in the FRR separation system. That is, the roller pair 210 includes an upper feed roller 220 for transporting the sheet into the machine, and a lower separation roller 230 to which driving force is applied by a drive shaft via a torque limiter in the opposite direction to the feed roller 220. It consists of

The separation roller 230 is biased toward the feed roller 220 by biasing means such as a spring. The sheet feeding roller 60 is configured to rotate leftward in FIG. 2B by transmitting the driving force of the sheet feeding roller 220 through the clutch means.

The sheet P abutted against the registration roller pair 250 and having a slack formed is matched with the timing at which the toner image formed on the intermediate transfer belt 16 is suitably transferred, and the secondary transfer roller 20 and the drive roller 18 The sheet is sent to the secondary transfer nip. Then, the fed sheet P is electrostatically transferred with high precision to the desired transfer position, with the toner image formed on the intermediate transfer belt 16 by the bias applied in the secondary transfer nip portion. It has become.

The post-transfer conveyance path 33 is disposed above the secondary transfer nip portion of the secondary transfer roller 20 and the drive roller 18. The fixing device 34 is installed near the upper end of the post-transfer conveyance path 33. The fixing device 34 includes a fixing roller 34a containing a heat source such as a halogen lamp, and a pressure roller 34b which rotates while being in contact with the fixing roller 34a with a predetermined pressure. The fixing device 34 may be of other configuration such as an endless rotary belt or an IH heating system.

The post-fixing conveying path 35 is disposed above the fixing device 34, and is branched into the paper discharge path 36 and the reverse conveying path 41 at the upper end of the post-fixing conveying path 35. The switching member 42 is disposed at this branch portion, and the switching member 42 is pivoted about the pivot shaft 42a. In the vicinity of the opening end of the paper discharge path 36, a paper discharge roller pair 37 is disposed.

The reverse conveying path 41 joins the sheet feeding path 32 at the other end opposite to the branching portion. Further, in the middle of the reverse conveyance path 41, a reverse conveyance roller pair 43 is disposed. The paper discharge tray 44 is installed on the top of the laser printer 100 so as to form a concave shape in the inward direction of the laser printer 100.

The powder container 10 (for example, a toner container) is disposed between the transfer device 15 and the paper feed tray 50. The powder container 10 is detachably attached to the main body of the laser printer 100.

The laser printer 100 according to the present embodiment requires a predetermined distance from the sheet feeding roller 60 to the secondary transfer roller 20 according to the relationship of transfer sheet conveyance. And the powder container 10 is installed in the dead space which arose in this distance, and the miniaturization of the whole laser printer is achieved.

The transfer cover 8 is disposed at the upper part of the sheet feeding tray 50 and in front of the sheet feeding tray in the pulling direction. Then, by opening the transfer cover 8, the inside of the laser printer 100 can be checked. The transfer cover 8 is provided with a manual paper feed roller 45 for manual paper feed and a manual paper feed tray 46 for manual paper feed.

Note that the laser printer of the present embodiment is an example of an image forming apparatus, and the image forming apparatus is not limited to the laser printer. That is, the image forming apparatus may be configured as a multifunction machine in which any one of a copying machine, a facsimile, a printer, a printing machine, and an ink jet recording apparatus, or at least two of them are combined.

(Operation of laser printer)
Next, the basic operation of the laser printer according to the present embodiment will be described below with reference to FIG. First, the case of single-sided printing will be described. The paper feed roller 60 is rotated by a paper feed signal from the control unit of the laser printer 100, as shown in FIG. Then, the sheet feeding roller 60 separates only the uppermost sheet of the bundle of sheets P stacked on the sheet feeding tray 50 and sends it to the sheet feeding path 32.

When the leading end of the sheet P fed by the sheet feed roller 60 and the roller pair 210 reaches the nip portion of the registration roller pair 250, the sheet P forms a slack and stands by in that state. Then, the optimum timing (synchronization) for transferring the toner image formed on the intermediate transfer belt 16 to the sheet P is achieved, and the leading edge skew of the sheet P is corrected.

In the case of manual feeding, a bundle of sheets stacked on the manual feed tray 46 passes a part of the reverse conveying path 41 by the manual feed roller 45 one by one from the uppermost sheet, and the nip of the registration roller pair 250 It is transported to the department. The subsequent operation is the same as the sheet feeding from the sheet feeding tray 50.

Here, with regard to the image forming operation, one process unit 1K will be described, and the description of the other process units 1Y, 1M, and 1C will be omitted. First, the charging device 4K uniformly charges the surface of the image carrier 2K to a high potential. Then, the exposure unit 7 irradiates the surface of the image carrier 2K with the laser beam L based on the image data.

On the surface of the image carrier 2K irradiated with the laser beam L, the potential of the irradiated portion decreases to form an electrostatic latent image. The developing device 5K has a developer carrier that carries a developer containing toner, and an electrostatic latent image is formed on the unused black toner supplied from the toner bottle 6K through the developer carrier. It is transferred to the surface portion of the image carrier 2K. The image carrier 2K to which the toner is transferred forms (develops) a black toner image on the surface thereof. Then, the toner image formed on the image carrier 2 K is transferred to the intermediate transfer belt 16.

The drum cleaning device 3K removes residual toner adhering to the surface of the image carrier 2K after the intermediate transfer process. The removed residual toner is sent to and collected by the waste toner storage unit in the process unit 1K by the waste toner conveyance means. Further, the charge removing device removes the residual charge of the image carrier 2K from which the residual toner has been removed by the cleaning device 3K.

Similarly, in the process units 1Y, 1M, and 1C of the respective colors, toner images are formed on the image carriers 2Y, 2M, and 2C, and transferred onto the intermediate transfer belt 16 so that the respective color toner images overlap.

The intermediate transfer belt 16 on which the toner images of the respective colors are transferred so as to overlap with each other travels to a secondary transfer nip portion of the secondary transfer roller 20 and the driving roller 18. On the other hand, the registration roller pair 250 nips and rotates the sheet abutted thereto at a predetermined timing, and in accordance with the timing at which the toner image formed by overlapping transfer on the intermediate transfer belt 16 is suitably transferred. The sheet is conveyed to the secondary transfer nip portion of the secondary transfer roller 20. Thus, the toner image on the intermediate transfer belt 16 is transferred onto the sheet P fed by the registration roller pair 250.

After transfer, the sheet P on which the toner image has been transferred is conveyed to the fixing device 34 through the conveyance path 33. Then, the sheet P conveyed to the fixing device 34 is sandwiched between the fixing roller 34 a and the pressure roller 34 b, and the unfixed toner image is fixed to the sheet P by heating and pressing. The sheet P on which the toner image is fixed is fed from the fixing device 34 to the conveyance path 35 after being fixed.

The switching member 42 is at a position where the vicinity of the upper end of the post-fixing conveyance path 35 is open as shown by the solid line in FIG. 1 at the timing when the sheet P is fed from the fixing device 34. Then, the sheet P fed from the fixing device 34 is fed to the sheet discharge path 36 via the conveyance path 35 after fixing. The sheet discharge roller pair 37 nips the sheet P fed to the sheet discharge path 36 and discharges the sheet P to the sheet discharge tray 44 by being rotationally driven, thereby completing single-sided printing.

Next, the case of performing double-sided printing will be described. As in the case of single-sided printing, the fixing device 34 sends the sheet P to the sheet discharge path 36. Then, when performing duplex printing, the discharge roller pair 37 conveys a part of the sheet P to the outside of the laser printer 100 by rotational driving.

Then, when the rear end of the sheet P passes through the paper discharge path 36, the switching member 42 pivots about the pivot shaft 42a as shown by the dotted line in FIG. 1 and closes the upper end of the transport path 35 after fixing. Do. Almost simultaneously with the closing of the upper end of the conveyance path 35 after fixing, the discharge roller pair 37 rotates in the direction opposite to the direction in which the sheet P is conveyed out of the laser printer 100 and delivers the sheet P to the reverse conveyance path 41.

The sheet P fed to the reverse conveyance path 41 passes through the reverse conveyance roller pair 43 and reaches the registration roller pair 250. Then, the registration roller pair 250 delivers the sheet P to the secondary transfer nip portion at an optimal timing (synchronization) for transferring the toner image formed on the intermediate transfer belt 16 to the toner image non-transferred surface of the sheet P. .

Then, the secondary transfer roller 20 and the driving roller 18 transfer the toner image to the toner image non-transferred surface (rear surface) of the sheet P when the sheet P passes through the secondary transfer nip portion. Then, the sheet P on which the toner image has been transferred is transported to the fixing device 34 through the transport path 33 after transfer.

The fixing device 34 fixes the unfixed toner image on the back surface of the sheet P by holding the sheet P conveyed by the fixing roller 34 a and the pressure roller 34 b and heating and pressing. Thus, the sheet P on which the toner image is fixed on both the front and back sides is fed from the fixing device 34 to the conveyance path 35 after fixing.

The switching member 42 is at a position where the vicinity of the upper end of the post-fixing conveyance path 35 is open as shown by the solid line in FIG. Then, the sheet P delivered from the fixing device 34 is delivered to the paper discharge path 36 via the fixing transport path. The sheet discharge roller pair 37 nips the sheet P fed to the sheet discharge path 36, rotationally drives the sheet P, and discharges the sheet P to the sheet discharge tray 44, thereby completing double-sided printing.

After the toner image on the intermediate transfer belt 16 is transferred to the sheet P, residual toner adheres on the intermediate transfer belt 16. The belt cleaning device 21 removes the residual toner from the intermediate transfer belt 16. Further, the toner removed from the intermediate transfer belt 16 is conveyed to the powder container 10 by the waste toner conveyance means, and is collected in the powder container 10.

(Rollers of roller pair)
Next, the rollers used for the roller pair 210 of the sheet feeding device 200 according to the embodiment of the present invention will be described with reference to FIGS. 3 to 6 show different embodiments 1 to 4, respectively.

In all embodiments, the feed roller 220 and the separation roller 230 of the roller pair 210 have elastic layers 222, 232 made of rubber. The rubber materials of the elastic layers 222 and 232 are completely made of the same rubber material by the feed roller 220 and the separation roller 230 in order to prevent “swelling” described later.

The rubber material is a polymer substance or material having rubber elasticity at room temperature, and is natural rubber (NR), isoprene rubber (IR), styrene butadiene rubber (SBR), ethylene propylene rubber (EPDM), chloroprene rubber ( CR), acrylonitrile butadiene rubber (NBR), urethane rubber (U), epichlorohydrin rubber (CO, ECO), silicone rubber (Q), fluoro rubber (FKM), etc. can be adopted.

Also, in all the embodiments, the apparent hardness of the separation roller 230 is harder than the apparent hardness of the feed roller 220. The magnitude relationship of the apparent hardness is due to the difference in the geometrical structure of the roller, and therefore, the forward rotation of the separation roller 230 is not influenced by the environmental factors such as temperature and humidity or the time-dependent change of the roller wear amount. Performance and separation performance can be improved. The improvement of the forward rotation performance and the separation performance based on the magnitude relationship of hardness has already been verified in Table 1-19 of Patent Document 1.

Types of "hardness" include "standard hardness" and "apparent hardness". The “standard hardness” conforms to each test method, and the dimensions and shape of the test piece satisfy the requirements. The “apparent hardness” is one in which the dimensions and shape of the test piece do not satisfy the requirements even if the test methods are complied with (see JIS K 6253-2).

The present invention is characterized in that by making the “apparent hardness” of the feeding roller 220 and the separating roller 230 different from each other, the feeding roller 220 side has a nip shape in which the concave shape is formed. The "apparent hardness" of the elastic layers 222, 232 of the feed roller 220 and the separating roller 230 can be changed by the "rubber thickness" of the respective elastic layers 222, 232.

In the first to third embodiments described below, how to change the "thickness of rubber" is made different. In the fourth embodiment, the thickness itself of the rubber is not changed, and the "apparent hardness" is made different depending on the uneven portion on the outer peripheral surface of the hub portion 221.

First Embodiment
FIG. 3 shows the first embodiment, where (a) shows the pressureless state of the feed roller 220 and the separation roller 230, and FIG. 3 (b) shows the pressure state of the feed roller 220 and the separation roller 230. Indicates The lower separation roller 230 is urged toward the upper feed roller 220 by an elastic force of a spring or the like, so that the lower separation roller 230 can be pressed against the feed roller 220 with the sheet interposed therebetween. A nip N of a predetermined contact pressure is formed between the two rollers.

The feed roller 220 and the separation roller 230 respectively have hard cylindrical hub portions 221 and 231 fixed to the roller rotation shaft, and cylindrical elastic layers 222 fitted to the outer circumferences of the hub portions 221 and 231. , And 232. The hub portions 221 and 231 have an inner cylinder 221a and 231a fitted to the rotation shaft of the roller, an outer cylinder 221b and 231b, and a plurality of spokes 221c and 231c radially connecting these. The rotation shafts of the rollers are fitted into the holes 221d and 231d of the inner cylinders 221a and 231a.

The feed roller 220 and the separation roller 230 have substantially the same diameter. This facilitates separation and conveyance of the sheet between the two rollers. The two rollers most preferably have the same outer diameter, but may not have the same diameter. One roller may be within two times, within 1.5 times or within 1.2 times of the other roller, or the like.

The radial thickness of the elastic layer 222 of the feed roller 220 is larger than the radial thickness of the elastic layer 232 of the separation roller 230. In the first embodiment, by making the radial thickness of the elastic layers 222 and 232 different as described above, the apparent hardness of the separation roller 230 is made harder than the apparent hardness of the feed roller 220. That is, due to the difference in apparent hardness, as shown in FIG. 3B, the shape of the nip N between the feeding roller 220 and the separating roller 230 is a shape in which the separating roller 230 bites into the feeding roller 220, ie, the feeding roller The 220 side has a concave shape of concave shape.

In FIG. 3 (b), the shape or diameter of the separation roller 230 is hardly changed as compared with FIG. 3 (a). Since the elastic layer 232 of the separation roller 230 has elasticity in the same manner as the elastic layer 222 of the feed roller 220, the shape or diameter of the separation roller 230 is actually deformed although it is minute. However, by appropriately setting the difference in radial thickness of the elastic layers 222 and 232 described above to, for example, 2: 1, the amount of the small deformation exerted on the nip shape in which the feeding roller 220 side becomes concave is The effects can be virtually ignored.

The hysteresis friction force at the nip N is increased by the upward convex nip shape as shown in FIG. Hysteresis friction is the friction on the roller surface caused by the force that the deformed rubber tries to return to its original shape.

Further, the amount of radial deformation (pressing amount) of the separation roller 230 can be reduced by the upward convex nip shape. Thereby, a long distance from the outer peripheral surface of the elastic layer 232 to the rotation center of the hub portion 231 can be secured, and the rotation force for rotating the separation roller 230 can be reduced.

Then, the rotational force of the feed roller 220 can be applied to the upward convex nip N securing a long distance to the rotation center of the hub portion 231 under a high surface pressure. Forward rotation performance is improved. Therefore, when feeding a sheet of paper in the nip N, smooth feeding without slippage with the sheet is performed due to the high forward rotation performance and the increase of the hysteresis frictional force, and particularly high carbon content is obtained. When paper is used, since the separation roller 230 does not slip, it is possible to suppress the dropping of the carbon carbide.

When a plurality of sheets are nipped in the nip N, the increase in the hysteresis friction force provides a reliable conveyance without slip on the upper layer sheet, while the relative movement of the separation roller 230 to the lower layer sheet is obtained. A positive separation effect can be obtained by the separation performance improvement by the large apparent hardness and the upward convex nip N.

Further, since the rubber materials of the elastic layers 222 and 232 of the feeding roller 220 and the separating roller 230 are completely the same, the liquid component of rubber is from the feeding roller 220 to the separating roller 230 or from the separating roller 230 By moving to the feed roller 220, the occurrence of "swelling" can be prevented.

The liquid component of the rubber exudes from the compounding agents (vulcanizing agent, vulcanization accelerator, reinforcing agent, anti-aging agent, filler, plasticizer, coloring agent, etc.), and it is a mineral such as gasoline and lubricating oil It contains oil, various animal and vegetable oils, solvents, chemicals and so on. When the "swelling" occurs, the diameters of both the rollers change, and as a result, the sheet conveyance amount changes and the possibility of jamming increases. However, in the embodiment of the present invention, the occurrence of swelling is prevented by making the rubber materials of the feed roller 220 and the separation roller 230 completely the same, so that the generation of jam due to the swelling can be prevented.

Second Embodiment
FIG. 4 shows the feeding roller 220 of the second embodiment, in which (a) shows the assembled state of the roller, (b) shows the disassembled state, and (c) and (d) show the roller pair using the feeding roller 220. Indicates

The feeding roller 220 has an uneven portion formed on the outer peripheral surface of the elastic layer 222. The uneven portion is formed by alternately forming convex streaks 222 a and concave streaks 222 b extending in the axial direction of the feed roller 220 in the circumferential direction. The hub portion 221 is fitted to the inside of the elastic layer 222 in the direction of the arrow in FIG. 4B. This hub portion 221 is the same as that used in the first embodiment.

The cross-sectional shape of the uneven portion is a rectangular shape in the illustrated example, but the uneven portion may be any other shape such as a trapezoid or a triangle. Moreover, it is also possible to make it have a emboss (皺) pattern having a depth of, for example, less than 1 mm by mold transfer, or to make a polishing pattern by polishing.

By forming the concavo-convex portion on the outer peripheral surface of the elastic layer 222 in this manner, the apparent hardness of the elastic layer 222 can be softened. FIG. 4C shows a roller pair 210 using the feed roller 220 of FIG. The lower separation roller 230 uses the same one as in the first embodiment.

As shown in FIG. 4C, the uneven portion is formed on the outer peripheral surface of the elastic layer 222 of the feeding roller 220, and the elastic layer 222 of the separation roller 230 is an inner and outer peripheral surface without the uneven portion. The apparent hardness of can be made relatively hard. Therefore, even when the elastic layer 222 of the feeding roller 220 and the elastic layer 232 of the separating roller 230 have the same thickness, the apparent hardness of the separating roller 230 is relatively hardened, and the pressure contact portion The nip shape can be concave toward the feed roller 220 side.

Further, as shown in FIG. 4D, even when the uneven portion is formed by the ridges 232a and the grooves 232b not only on the feeding roller 220 but also on the outer peripheral surface of the elastic layer 232 of the separation roller 230, the height of the uneven portion By making the thickness smaller than the concavo-convex portion of the feeding roller 220, the apparent hardness of the separating roller 230 is relatively hardened as in the above embodiment, and the nip shape is made concave toward the feeding roller 220 side. be able to.

Third Embodiment
FIG. 5 shows the feeding roller 220 of the third embodiment, in which (a) shows the assembled state of the roller, (b) shows the disassembled state, and (c) and (d) show the roller pair using the feeding roller 220. Indicates

The feeding roller 220 has an uneven portion formed on the inner peripheral surface of the elastic layer 222. The uneven portion is formed by alternately forming convex streaks 222 a and concave streaks 222 b extending in the axial direction of the feed roller 220 in the circumferential direction. The hub portion 221 is fitted to the inside of the elastic layer 222 from the direction of the arrow in FIG. This hub portion 221 is the same as that used in the first embodiment.

The cross-sectional shape of the uneven portion is a rectangular shape in the illustrated example, but the uneven portion may be any other shape such as a trapezoid or a triangle. Moreover, it is also possible to make it have a emboss (皺) pattern having a depth of, for example, less than 1 mm by mold transfer, or to make a polishing pattern by polishing.

By forming the concavo-convex portion on the inner peripheral surface of the elastic layer 222 in this manner, the apparent hardness of the elastic layer 222 can be softened. FIG. 5C shows a roller pair 210 using the feed roller 220 of FIG. The lower separation roller 230 uses the same one as in the first embodiment.

As shown in FIG. 5C, the uneven portion is formed on the inner peripheral surface of the elastic layer 222 of the feeding roller 220, and the elastic layer 222 of the separation roller 230 is an inner and outer peripheral surface without the uneven portion. The apparent hardness of 230 can be made relatively hard. Therefore, even when the elastic layer 222 of the feeding roller 220 and the elastic layer 232 of the separating roller 230 have the same thickness, the apparent hardness of the separating roller 230 is relatively hardened as in the above embodiment, The nip shape of the press-contact portion where the rollers press-contact with each other can be concave toward the feeding roller 220 side.

Further, as shown in FIG. 5D, even in the case where the uneven portion is formed not only by the feeding roller 220 but also by the inner circumferential surface of the elastic layer 232 of the separation roller 230, the uneven portion is formed by By making the height lower than the concavo-convex portion of the feed roller 220, the apparent hardness of the separation roller 230 is relatively hardened as in the embodiment described above, and the nip shape is concaved toward the feed roller 220. can do.
Fourth Embodiment
FIG. 6 shows the feeding roller 220 according to the fourth embodiment, in which (a) shows the assembled state of the roller, (b) shows the disassembled state, and (c) and (d) show the roller pair using the feeding roller 220. Indicates

The feeding roller 220 has an uneven portion formed on the outer peripheral surface of the hub portion 221. The uneven portion is formed by alternately forming convex streaks 221 e and concave streaks 221 f extending in the axial direction of the hub portion 221 in the circumferential direction. The hub portion 221 is fitted to the inside of the elastic layer 222 in the direction of the arrow in FIG. This hub portion 221 is the same as that used in the first embodiment.

The cross-sectional shape of the uneven portion is a rectangular shape in the illustrated example, but the uneven portion may be any other shape such as a trapezoid or a triangle. Moreover, it is also possible to make it have a emboss (皺) pattern having a depth of, for example, less than 1 mm by mold transfer, or to make a polishing pattern by polishing.

By forming the uneven portion on the outer peripheral surface of the hub portion 221 as described above, it is possible to soften the apparent hardness of the elastic layer 222 fitted to the outside. FIG. 6C shows a roller pair 210 using the feed roller 220 of FIG. The lower separation roller 230 uses the same one as in the first embodiment.

As shown in FIG. 6C, the uneven portion is formed on the outer peripheral surface of the hub portion 221 of the feeding roller 220, and the hub portion 231 of the separation roller 230 is an outer peripheral surface without the uneven portion. The apparent hardness can be made relatively hard. That is, while the inner peripheral surface of the elastic layer 222 of the feed roller 220 partially bites into the uneven portion of the outer peripheral surface of the hub portion 221 by the pressure acting on the nip N, the separation roller 230 is elastic because there is no uneven portion. There is no room for layer 232 to escape. Therefore, even when the elastic layer 222 of the feeding roller 220 and the elastic layer 232 of the separating roller 230 have the same thickness, the apparent hardness of the separating roller 230 is relatively hardened, and the pressure contact portion The nip shape can be concave toward the feed roller 220 side.

Further, as shown in FIG. 6D, even when the uneven portion is formed by the ridges 231e and the grooves 231f not only on the feeding roller 220 but also on the outer peripheral surface of the hub portion 231 of the separation roller 230, the height of the uneven portion is high. By making the thickness smaller than the concavo-convex portion of the feeding roller 220, the apparent hardness of the separation roller 230 is relatively hardened, and the nip shape is concaved toward the feeding roller 220 as in the above embodiment. can do.

As mentioned above, although this invention was concretely demonstrated based on embodiment, this invention is not limited to the said embodiment, It can change variously within the range of the technical idea as described in a claim. Needless to say. For example, the “concave / convex portion” may be formed by forming a plurality of ridges and grooves in the circumferential direction on the inner peripheral surface or outer peripheral surface of the elastic layer of the roller or the outer peripheral surface of the hub portion.

The "concave / convex portion" can also be constituted by a plurality of projections or depressions formed in a scattered manner, in which case by changing the height or depth of the projections or depressions, the formation density or the diameter, The apparent hardness of the separating roller can be varied. In addition, the apparent hardness of the feeding roller 220 and the separating roller 230 may be made different by combining two or more of the uneven portion, the protrusion or the recess, and the foamed elastic layer.

The apparent hardness of the feed roller and the separation roller may be made different by forming a foamed elastic layer on the elastic layer of the feed roller. As a raw material of a foaming elastic layer, the resin foam or rubber foam of a closed cell structure can be used, for example. When the foamed elastic layer is also formed on the elastic layer of the separation roller, the apparent hardness of both rollers is made different by making the foaming ratio of the foamed elastic layer of the feeding roller larger than the foaming ratio of the foamed elastic layer of the separation roller. Can.

1C, 1M, 1Y, 1K: Process unit 2C, 2M, 2Y, 2K: Image carrier
3C, 3M, 3Y, 3K: drum cleaning device 4C, 4M, 4Y, 4K: charging device
5C, 5M, 5Y, 5K: developing devices 6C, 6M, 6Y, 6K: toner bottles 7: exposure devices 8: transfer covers 10: powder containers 15: transfer devices 16: intermediate transfer belt 17: driven rollers 18: drive Rollers 19C, 19M, 19Y, 19K: primary transfer roller 20: secondary transfer roller 21: belt cleaning device 31: registration sensor 32: paper feed path 33: post-transfer conveyance path 34: fixing device 34a: fixing roller 34b: pressure Rollers 35: conveying path after fixing 36: sheet discharge path 37: sheet discharge roller pair 41: reverse sheet conveying path 42: switching member 42a: rocking shaft 43: sheet reverse conveying roller pair 44: sheet discharge tray 45: sheet feeding roller 46: Manual feeding tray 50: paper feeding tray 60: paper feeding roller 100: color laser printer 200: sheet feeding device 210: roller pair 220: feeding roller 221: hub portion 221e: convex line 221f: concave line 222: elastic layer 222a: convex line 222b: concave line 230: separation roller 231: hub section 232: elastic layer 240: conveyance roller 250: resist roller pair L: laser beam N: nip P: paper

Patent No. 3633658

Claims (17)

It is a sheet feeding apparatus having a separating and conveying means for separating and conveying the sheet materials fed from the stacking unit on which the sheet materials are stacked one by one, the separation and conveying means comprising:
A feeding roller which rotates in the feeding direction of the sheet material;
And a separation roller pressable against the feeding roller with the sheet material interposed therebetween,
By making the apparent hardness of the feeding roller different from that of the separating roller, the nip shape of the pressure contact portion where the feeding roller and the separating roller are in pressure contact is made concave toward the feeding roller side. A sheet feeding device characterized by   The feeding roller and the separating roller have a cylindrical hub portion fixed to the rotation shaft of each roller, and a cylindrical elastic layer fitted on the outer periphery of the hub portion, and the feeding The sheet hardness according to claim 1, wherein the apparent hardness is made different by making the radial thickness of the elastic layer of the roller greater than the radial thickness of the elastic layer of the separation roller. Feeder.   The feeding roller and the separation roller are cylindrical hubs fixed to the rotation shafts of the respective rollers, and a cylindrical elastic layer fitted on the outer periphery of the hub and having an uneven portion on the outer peripheral surface The apparent hardness is made different by making the height of the uneven portion of the feeding roller higher than the height of the uneven portion of the separation roller. Sheet feeding device.   The feeding roller and the separating roller have a cylindrical hub portion fixed to the rotation shaft of each roller, and a cylindrical elastic layer fitted on the outer periphery of the hub portion, and the feeding 2. The sheet feeding device according to claim 1, wherein the roller has different in apparent hardness by having an uneven portion on the outer peripheral surface of the elastic layer.   The feeding roller and the separating roller are respectively a cylindrical hub fixed to the rotating shaft of the roller, and a cylindrical elastic layer fitted to the outer periphery of the hub and having an uneven portion on the inner peripheral surface The apparent hardness is made different by making the height of the uneven portion of the feeding roller higher than the height of the uneven portion of the separation roller. 1 sheet feeding device.   The feeding roller and the separating roller each have a cylindrical hub portion fixed to the rotating shaft of the roller, and a cylindrical elastic layer fitted to the outer periphery of the hub portion, and the feeding 2. A sheet feeding apparatus according to claim 1, wherein said roller has different concavo-convex hardness by having a concavo-convex portion on the inner peripheral surface of the elastic layer.   The feeding roller and the separating roller have a cylindrical hub portion fixed to the rotation shaft of each roller, and a cylindrical elastic layer fitted on the outer periphery of the hub portion, and the hub portion An uneven portion is formed on the outer peripheral surface of the sheet, and the apparent hardness is made different by making the height of the uneven portion of the feeding roller higher than the height of the uneven portion of the separation roller. The sheet feeding apparatus according to claim 1, characterized in that:   The feeding roller and the separating roller have a cylindrical hub portion fixed to the rotation shaft of each roller, and a cylindrical elastic layer fitted on the outer periphery of the hub portion, and the feeding 2. A sheet feeding apparatus according to claim 1, wherein said roller has different concavo-convex hardness by having a concavo-convex portion on the outer peripheral surface of its hub portion.   The feeding roller and the separating roller each have a cylindrical hub portion fixed to the rotating shaft of the roller, and a cylindrical elastic layer fitted to the outer periphery of the hub portion, and the feeding 2. The sheet feeding device according to claim 1, wherein the apparent hardness is made different by the elastic layer having a foamed elastic layer.   The feeding roller and the separating roller each have a cylindrical hub portion fixed to the rotation shaft of the roller, and a cylindrical foam elastic layer fitted to the outer periphery of the hub portion, The sheet hardness according to claim 1, wherein the apparent hardness is made different by setting the expansion ratio of the elastic foam layer of the feeding roller to be larger than the expansion ratio of the elastic foam layer of the separation roller. Feeder.   The sheet feeding device according to any one of claims 3 to 8, wherein the concavo-convex portion has a plurality of convex lines and concave lines formed in the axial direction of the roller.   The sheet feeding device according to any one of claims 3 to 8, wherein the uneven portion has a plurality of convex lines and concave lines formed in the circumferential direction of the roller.   The sheet feeding apparatus according to any one of claims 3 to 8, wherein the uneven portion has a plurality of protrusions formed in a scattered manner.   The sheet feeding apparatus according to any one of claims 3 to 8, wherein the uneven portion has a plurality of depressions formed in a scattered manner.   The sheet feeding apparatus according to any one of claims 1 to 14, wherein the feeding roller and the separation roller are formed of the same material.   The sheet feeding device according to any one of claims 1 to 15, wherein diameters of the feeding roller and the separation roller are formed to be substantially the same.   An image forming apparatus comprising: the sheet feeding device according to any one of claims 1 to 16; and an image forming unit for forming an image on a sheet material fed from the sheet feeding device.