JP6103361B2 - Sheet material feeding apparatus, and image forming apparatus and image reading apparatus provided with the same - Google Patents

Description

  The present invention relates to a sheet material feeding apparatus that separates and feeds sheet materials one by one from a sheet material stacking unit that stacks a plurality of sheet materials, and an image forming apparatus and an image reading apparatus including the sheet material feeding apparatus. is there.

  Patent Document 1 discloses a paper feeding device that feeds paper from a paper feeding cassette (sheet material stacking unit) having a bottom plate that can be stacked and stacked up and down. This sheet feeding device employs a so-called FRR system configuration including a pickup roller (sheet feeding rotating body) and a sheet separating means including a feed roller (feed rotating body) and a retard roller (return rotating body). ing. In this paper feeding device, after the paper fed from the paper feeding cassette by the pickup roller enters the feed roller, the bottom plate is lowered, and the paper stacked on this is separated from the pickup roller. Thereafter, the bottom plate is raised again at the timing when the trailing edge of the paper being fed comes out of the pickup roller, and the paper loaded thereon is brought into contact with the pickup roller again so that the next feeding can be performed.

  In the image forming apparatus described in Patent Document 1, such a series of paper feeding operations is selectively performed according to the type of paper. Specifically, for paper with a low coefficient of friction between sheets, the pickup roller is kept in contact with the stacked paper, but for special paper such as gloss coated paper with a high coefficient of friction between sheets, The above series of paper feeding operations is performed. As a result, for such special paper, after the paper is fed out by the pickup roller, the load caused by the pickup roller pressing down the rear end portion of the paper from the top is eliminated. As a result, the frictional force between the sheets is reduced, and the occurrence of double feeding in the special paper having a high coefficient of friction between the sheets is suppressed.

  Patent Document 2 also discloses a paper feeding device similar to the paper feeding device described in Patent Document 1. In the paper feeding device described in Patent Document 2, the paper fed by the pickup roller (sheet feeding rotating body) is fed to the feed roller (feed rotation) when feeding high friction paper for feeding paper having a high coefficient of friction between the papers. The pickup roller is pressed against the sheet bundle until it is held between the roller pair of the body and the separation roller (return rotating body), and the pickup roller is depressurized or separated from the sheet bundle during separation conveyance by the roller pair. . On the other hand, when feeding low-friction paper, the pickup roller is always pressed against the upper surface of the paper bundle.

  However, the contact / separation operation between the pickup roller and the paper is a failure such as vibration or noise due to collision between the paper and the pickup roller, vibration or noise due to the operation sound of the contact / separation mechanism, or an increase in power consumption. Accompanied by. Therefore, it is preferable to keep such contact / separation operation to the minimum necessary.

  Here, in the paper feeding devices described in Patent Document 1 and Patent Document 2, when a paper having a high coefficient of friction between the papers is fed, between each pickup paper and the paper, the paper is fed. Separation and contact are performed. However, when feeding a sheet having a high coefficient of friction between the sheets, even if the pickup roller and the sheet are kept in contact with each other, double feeding may not occur. On the other hand, in the paper feeding device described in Patent Document 1 and Patent Document 2, the separation and contact between the pickup roller and the paper are repeated uniformly, including the case where the double feed does not actually occur. It is. For this reason, there has been a problem that unnecessary contact / separation operations are performed, causing problems such as vibration, noise, and increased power consumption due to the contact / separation operations.

  The present invention has been made in view of the above problems, and the object of the present invention is to reduce unnecessary contact and separation operations between the sheet delivery rotating body and the sheet material, while suppressing double feeding. It is an object of the present invention to provide a sheet material feeding device that can reduce problems caused by a separation operation, and an image forming apparatus and an image reading apparatus including the sheet material feeding device.

  In order to achieve the above object, the present invention provides a sheet material stacking unit that stacks a plurality of sheet materials in a stacked manner, and a topmost sheet that is rotationally driven by a drive input from a drive source and is stacked on the sheet material stacking unit. A sheet delivery rotator for feeding the sheet material in contact with the material; contact / separation means for contacting and separating the uppermost sheet material and the sheet delivery rotator; and the sheet material sent by the sheet delivery rotator In a sheet material feeding apparatus having a separating and feeding unit that separates and feeds the upper sheet material, whether or not a duplicate feeding in which a plurality of sheet materials are fed to the separating and feeding unit by the sheet feeding rotating body has occurred. The duplicate delivery detection means for detecting whether or not the duplicate delivery is detected during the continuous feeding of feeding a plurality of sheet materials continuously and during the feeding of one sheet material. Detect When the sheet feeding rotating body starts feeding the next sheet material, the sheet feeding rotating body and the uppermost sheet material of the sheet material stacking section are kept in contact with each other to feed one sheet material. When the duplicate delivery detection means detects that duplicate delivery has occurred, the sheet delivery rotator is separated from the uppermost sheet material of the sheet material stacking section. Contact / separation control means for performing contact / separation control for controlling the contact / separation means so that the sheet delivery rotating body and the uppermost sheet material are brought into contact with each other before starting the feeding of the sheet material. And

  The double feed in which the plurality of sheet materials are fed in an overlapping manner occurs at least when the overlap feeding in which the plurality of sheet materials are fed to the separation feeding unit by the sheet feed rotating body occurs. Therefore, when duplicate transmission has not occurred, double feeding does not occur. In the present invention, it is possible to detect the occurrence of duplicate transmission, which is a necessary condition for occurrence of double feeding, by the duplicate transmission detecting means. Thereby, it can be known in advance that no double feed occurs from the detection result that the duplicate send by the duplicate send detection means does not occur.

  Therefore, in the present invention, when the duplicate delivery detection unit detects that duplicate delivery has not occurred during feeding of one sheet material, the sheet delivery rotating body starts feeding the next sheet material. Until then, the contact state between the sheet delivery rotating body and the uppermost sheet material of the sheet material stacking unit is maintained. In this case, since double feeding does not occur even if the contact state is maintained, unnecessary contact / separation operation between the sheet delivery rotating body and the uppermost sheet material can be avoided.

  On the other hand, if the duplicate delivery detection means detects that duplicate delivery has occurred during feeding of one sheet material, there is a possibility that double feed will occur when the one sheet material is fed. In this case, in the present invention, the contact / separation control is executed to separate the sheet delivery rotating body from the uppermost sheet material, and the sheet delivery rotating body presses the plurality of sheet materials related to the overlapping delivery from above. Release the load caused by. Thereby, the frictional force between the plurality of sheet materials is reduced, and the separation and feeding means can appropriately separate and feed the uppermost sheet material, thereby suppressing the occurrence of double feeding.

As described above, in the present invention, it is possible to appropriately grasp in advance that double feeding does not occur, and when the double feeding does not occur, it is possible to avoid the contact / separation operation between the sheet feeding rotating body and the uppermost sheet material, Unnecessary contact / separation operations are reduced, and problems caused by contact / separation operations can be reduced. In addition, when there is a possibility of occurrence of double feed, the occurrence of double feed can be suppressed by performing a contact / separation operation.
Therefore, according to the present invention, it is possible to reduce the trouble caused by the contact / separation operation while reducing the unnecessary contact / separation operation between the sheet feeding rotating body and the sheet material and suppressing the multifeed. It is done.

1 is a schematic configuration diagram illustrating a copying machine according to an embodiment. FIG. 2 is a partial configuration diagram illustrating an enlarged part of an image forming unit in the copier. FIG. 3 is a partially enlarged view showing a part of a tandem part including four process units in the image forming part. 2 is an explanatory perspective view of an image reading unit of the copier. FIG. FIG. 3 is an enlarged view of a pickup unit in a state where a pickup roller of a recording paper feeding device of the copier is in contact with the upper surface of the recording paper. FIG. 3 is an enlarged view of the pickup unit in a state where the pickup roller is separated from the upper surface of the recording paper. FIG. 3 is a schematic diagram when the pickup unit is viewed from the recording paper conveyance direction. FIG. 3 is a schematic diagram illustrating a configuration of a detection unit that detects a rotation operation of a reverse roller of the recording paper feeding device. It is a graph which shows an example of the output signal of the encoder sensor which detects the rotation operation of the reverse roller. 6 is a flowchart illustrating control of a paper feeding operation in the embodiment. It is a schematic diagram which shows the structure of the detection means which detects the rotation operation of the reverse roller in the modification 1. It is a graph which shows an example of each output signal of two encoder sensors which detect rotation operation of the reverse roller. 10 is a flowchart illustrating control of a paper feeding operation in Modification 2. 10 is a flowchart illustrating control of a paper feeding operation in Modification 3.

Hereinafter, an embodiment in which the present invention is applied to an electrophotographic copying machine 500 as an image forming apparatus will be described.
First, a basic configuration of the copier 500 according to the present embodiment will be described.
FIG. 1 is a schematic configuration diagram showing a copying machine 500.
The copying machine 500 includes an image forming unit 1 as an image forming unit, a recording paper feeding device 40 as a sheet material feeding device, and an image reading unit 50. An image reading unit 50 as an image reading device includes a scanner 150 fixed on the image forming unit 1 and an automatic document feeder (hereinafter referred to as “ADF”) 51 as a sheet material feeding device supported by the scanner 150. And have.

  The recording paper feeding device 40 includes two paper feeding cassettes 42 serving as sheet material stacking units arranged in multiple stages in a paper bank 41, and a sheet sending rotating body that feeds recording paper P as a sheet material from the paper feeding cassette 42. A pick-up roller 43, and a separating and feeding means 45 for separating the fed recording paper P and feeding it to the recording paper feed path 44. The detailed configuration and operation of the recording paper feeding device 40 will be described later. Further, a plurality of conveyance roller pairs 46 that convey the recording paper P to the main body side recording paper feeding path 37 as a conveyance path of the image forming unit 1 are also provided. Then, the recording sheet P in the sheet feeding cassette 42 is fed into the main body side recording sheet feeding path 37 in the image forming unit 1.

  The image forming unit 1 includes an optical writing device 2 as a latent image forming unit and four process units 3K, Y, and M that form black, yellow, magenta, and cyan (K, Y, M, and C) toner images. , C, transfer unit 24, paper transport unit 28, registration roller pair 33, fixing device 34, switchback device 36, main body side recording paper feed path 37, and the like. Then, a light source such as a laser diode or LED (not shown) disposed in the optical writing device 2 is driven to irradiate the four drum-shaped photosensitive members 4K, Y, M, and C with the laser light L. . By this irradiation, electrostatic latent images are formed on the surfaces of the photoreceptors 4K, Y, M, and C, and the latent images are developed into toner images via a predetermined development process.

  FIG. 2 is an enlarged partial configuration diagram illustrating a part of the internal configuration of the image forming unit 1. FIG. 3 is a partially enlarged view showing a part of a tandem part composed of four process units 3K, Y, M, and C. The four process units 3K, Y, M, and C have substantially the same configuration except that the colors of the toners to be used are different. Therefore, the subscripts K, Y, M, and C attached to the respective reference numerals in FIG. Is omitted.

  The process units 3K, Y, M, and C support the photoconductor 4 and various devices disposed around it as a single unit on a common support, and image forming of the copying machine 500 main body. It can be attached to and detached from the part 1. One process unit 3 includes a charging device 5, a developing device 6, a drum cleaning device 15, a charge removal lamp 22, and the like around the photoconductor 4. The copying machine 500 has a so-called tandem type configuration in which four process units 3K, Y, M, and C are arranged so as to face an intermediate transfer belt 25 described later along the endless movement direction. Yes.

  As the photoreceptor 4, a drum-shaped member is used in which a photosensitive layer is formed by applying a photosensitive organic photosensitive material to a base tube made of aluminum or the like. However, an endless belt may be used.

  The developing device 6 develops the latent image using a two-component developer containing a magnetic carrier and a nonmagnetic toner (not shown). In order to transfer the toner in the two-component developer carried on the developing sleeve 12 to the photosensitive member 4, the agitating unit 7 that conveys the two-component developer accommodated in the inside and supplies the developing sleeve 12 with stirring. Development section 11.

  The stirring unit 7 is provided at a position lower than the developing unit 11, and includes two conveying screws 8 arranged in parallel to each other, a partition plate provided between the two conveying screws 8, and the developing case 9. A toner density sensor 10 provided on the bottom surface is provided.

  The developing unit 11 includes a developing sleeve 12 that faces the photosensitive member 4 through the opening of the developing case 9, a magnet roller 13 that is non-rotatably provided inside the developing sleeve 12, a doctor blade 14 that approaches the developing sleeve 12, and the like. ing. The developing sleeve 12 has a non-magnetic rotatable cylindrical shape. The magnet roller 13 has a plurality of magnetic poles that are sequentially arranged from the position facing the doctor blade 14 toward the rotation direction of the developing sleeve 12. Each of these magnetic poles applies a magnetic force to the two-component developer on the developing sleeve 12 at a predetermined position in the rotational direction. As a result, the two-component developer sent from the stirring unit 7 is attracted and carried on the surface of the developing sleeve 12 and a magnetic brush is formed on the surface of the developing sleeve 12 along the lines of magnetic force.

  The magnetic brush is regulated to an appropriate layer thickness when passing through the position facing the doctor blade 14 as the developing sleeve 12 rotates, and then conveyed to the developing region facing the photoconductor 4. Then, the toner is transferred onto the electrostatic latent image by the potential difference between the developing bias applied to the developing sleeve 12 and the electrostatic latent image on the photosensitive member 4, thereby contributing to development. Further, the two-component developer that forms a magnetic brush and is carried by the developing sleeve 12 and passes through the developing region returns to the developing unit 11 again as the developing sleeve 12 rotates, and is formed between the magnetic poles of the magnet roller 13. After being separated from the sleeve surface due to the influence of the repulsive magnetic field, the magnetic field is returned to the stirring unit 7. An appropriate amount of toner is supplied to the two-component developer in the stirring unit 7 based on the detection result of the toner density sensor 10. As the developing device 6, a device using a one-component developer not containing a magnetic carrier may be adopted instead of a device using a two-component developer.

  As the drum cleaning device 15, a system in which the cleaning blade 16 made of an elastic body is pressed against the photoconductor 4 is used, but another system may be used. For the purpose of enhancing the cleaning property, this example employs a system having a contact conductive fur brush 17 whose outer peripheral surface is in contact with the photoreceptor 4 so as to be rotatable in the direction of the arrow in the figure. The fur brush 17 also serves to apply the lubricant to the surface of the photosensitive member 4 while scraping the lubricant from a solid lubricant (not shown) into a fine powder. A metal electric field roller 18 for applying a bias to the fur brush 17 is rotatably provided in the direction of the arrow in the figure, and the tip of the scraper 19 is pressed against it. The toner attached to the fur brush 17 is transferred to the electric field roller 18 to which a bias is applied while rotating in contact with the fur brush 17 in the counter direction. Then, after being scraped from the electric field roller 18 by the scraper 19, it falls onto the recovery screw 20. The collection screw 20 conveys the collected toner toward the end of the drum cleaning device 15 in the direction orthogonal to the drawing surface, and delivers it to the external recycling conveyance device 21. The recycle conveyance device 21 sends the collected toner that has been delivered to the developing device 6 for recycling.

  The neutralization lamp 22 neutralizes the surface of the photoreceptor 4 by light irradiation. The surface of the photoreceptor 4 that has been neutralized is uniformly charged by the charging device 5 and then subjected to optical writing processing by the optical writing device 2. In the copying machine 500, the charging device 5 is a device in which a charging roller to which a charging bias is applied is rotated while being in contact with the photoconductor 4, but a scorotron that performs a charging process on the photoconductor 4 in a non-contact manner. A charger or the like may be used.

  In FIG. 2 described above, K, Y, M, and C toner images are formed on the photoreceptors 4K, Y, M, and C of the four process units 3K, Y, M, and C by the processes described above. Is done.

  A transfer unit 24 is disposed below the four process units 3K, Y, M, and C. The transfer unit 24 moves the intermediate transfer belt 25 stretched by a plurality of rollers endlessly in the clockwise direction in the drawing while contacting the photoreceptors 4K, Y, M, and C. As a result, primary transfer nips for K, Y, M, and C in which the photoreceptors 4K, Y, M, and C contact the intermediate transfer belt 25 are formed. In the vicinity of the primary transfer nips for K, Y, M, and C, the intermediate transfer belt 25 is moved to the photoreceptors 4K, Y, M, and C by primary transfer rollers 26K, Y, M, and C disposed inside the belt loop. It is pushing toward. A primary transfer bias is applied to the primary transfer rollers 26K, Y, M, and C by a power source (not shown). As a result, a primary transfer electric field for electrostatically moving the toner images on the photoconductors 4K, Y, M, and C toward the intermediate transfer belt 25 is formed in the primary transfer nips for K, Y, M, and C. Yes. In the drawing, toner images are sequentially transferred from the primary transfer nips to the front surface of the intermediate transfer belt 25 that sequentially passes through the primary transfer nips for K, Y, M, and C along with the endless movement in the clockwise direction. Overlaid and primary transferred. By this primary transfer of superposition, a four-color superposed toner image (hereinafter referred to as “four-color toner image”) is formed on the front surface of the intermediate transfer belt 25.

  Below the transfer unit 24 in the figure, a paper transport unit 28 is provided between the drive roller 30 and the secondary transfer roller 31 to endlessly move the endless paper transport belt 29. The intermediate transfer belt 25 and the paper transport belt 29 are sandwiched between the secondary transfer roller 31 and the lower stretching roller 27 of the transfer unit 24. As a result, a secondary transfer nip is formed in which the front surface of the intermediate transfer belt 25 and the front surface of the paper transport belt 29 abut. A secondary transfer bias is applied to the secondary transfer roller 31 by a power source (not shown). On the other hand, the lower stretching roller 27 of the transfer unit 24 is grounded. Thereby, a secondary transfer electric field is formed in the secondary transfer nip.

  A registration roller pair 33 is disposed on the right side of the secondary transfer nip in the drawing. A registration roller sensor (not shown) is disposed near the entrance of the registration nip of the registration roller pair 33. The recording paper P conveyed from the recording paper feeding device 40 toward the registration roller pair 33 is temporarily stopped after a predetermined time when the leading edge of the recording paper P is detected by a registration roller sensor (not shown). The tip is brought into contact with the resist nip of the roller pair 33. As a result, the posture of the recording paper P is corrected, and preparations for synchronization with image formation are completed.

  When the leading edge of the recording paper P hits the registration nip, the registration roller pair 33 resumes roller rotation driving at a timing at which the recording paper P can be synchronized with the four-color toner image on the intermediate transfer belt 25, and the recording paper P is removed. Send to the secondary transfer nip. In the secondary transfer nip, the four-color toner images on the intermediate transfer belt 25 are collectively transferred to the recording paper P due to the influence of the secondary transfer electric field and the nip pressure, and combined with the white color of the recording paper P to form a full-color image. The recording paper P that has passed through the secondary transfer nip is separated from the intermediate transfer belt 25 and is conveyed to the fixing device 34 along with its endless movement while being held on the front surface of the paper conveyance belt 29.

  The transfer residual toner that has not been transferred to the recording paper P at the secondary transfer nip is attached to the front surface of the intermediate transfer belt 25 that has passed through the secondary transfer nip. The transfer residual toner is scraped and removed by the belt cleaning device 32 in which the cleaning member contacts the intermediate transfer belt 25.

  The recording paper P conveyed to the fixing device 34 is fixed with a full-color image by pressurization or heating in the fixing device 34, and then sent from the fixing device 34 to the paper discharge roller pair 35. The paper is discharged to a paper discharge tray 501.

  In FIG. 1 described above, a switchback device 36 that is a recording paper reversing device is disposed under the paper transport unit 28 and the fixing device 34. Thus, when performing double-sided printing, the conveyance path of the recording paper P that has undergone image fixing processing on one side is switched to the switchback device 36 side by the switching claw, where the recording paper P is reversed and re-secondary. Enter the transfer nip. Then, the second transfer process and the fixing process of the image are also performed on the other side of the recording sheet P, and then the sheet is discharged onto the discharge tray 501.

  The image reading unit 50 including the scanner 150 fixed on the image forming unit 1 and the ADF 51 fixed on the image forming unit 1 includes two fixed reading units and a moving reading unit 152 described later. The movable reading unit 152 is disposed directly below the second contact glass 155 fixed to the upper wall of the casing of the scanner 150 so as to come into contact with the document MS, and shows an optical system including a light source, a reflection mirror, and the like. It can be moved in the left-right direction. Then, in the process of moving the optical system from the left side to the right side in the figure, after the light emitted from the light source is reflected by the lower surface of the document MS placed on the second contact glass 155, a plurality of reflecting mirrors are Then, the light is received by the image reading sensor 153 fixed to the scanner 150.

  On the other hand, the image reading unit 50 includes, as fixed reading units, a first fixed reading unit 151 disposed in the scanner 150 and a second fixed reading unit 95 described later disposed in the ADF 51. . A first fixed reading unit 151 including a light source, a reflection mirror, an image reading sensor such as a CCD, and the like is disposed directly below a first contact glass 154 fixed to the upper wall of the casing of the scanner 150 so as to contact the document MS. ing. Then, when the document MS conveyed by the ADF 51 passes over the first contact glass 154, image reading is performed via a plurality of reflecting mirrors while sequentially reflecting the light emitted from the light source on the first surface of the document MS. The sensor 153 receives light. Accordingly, the first surface of the document MS is scanned without moving the optical system including the light source and the reflection mirror. The second fixed reading unit 95 scans the second surface of the document MS after passing through the first fixed reading unit 151.

  An ADF 51 disposed on the scanner 150 includes a document placing table 53 for placing a document MS before reading on a main body cover 52, a document transporting unit 54 for transporting a document MS as a sheet material, and a reading. A document stacking table 55 for stacking the subsequent document MS is held.

FIG. 4 is a perspective explanatory view of the image reading unit 50.
As shown in FIG. 4, it is supported by a hinge 159 fixed to the scanner 150 so as to be swingable in the vertical direction. Then, by swinging, it moves like an open / close door, and the first contact glass 154 and the second contact glass 155 on the upper surface of the scanner 150 are exposed in the opened state. In the case of a single-bound document such as a book in which one corner of a document bundle is bound, the documents cannot be separated one by one, and therefore cannot be transported by the ADF 51. Therefore, in the case of a single-sided original, the ADF 51 is opened as shown in FIG. 4, and then the single-sided original with the page to be read open facing down is placed on the second contact glass 155 and then the ADF 51 is placed. close up. Then, the image of the page is read by the moving reading unit 152 shown in FIG.

  On the other hand, in the case of a document bundle in which a plurality of documents MS, which are independent sheet materials, are simply stacked, the documents MS are automatically conveyed one by one by the ADF 51, while the first fixed reading unit 151 and the ADF 51 in the scanner 150 are conveyed. The second fixed reading unit 95 can sequentially read. In this case, after the original bundle is set on the original placement table 53, the copy start button 158 of the operation unit 108 is pressed. Then, the ADF 51 sends the document MS of the bundle of documents placed on the document placement table 53 in order from the top into the document conveyance unit 54 and conveys the document MS toward the document stacking table 55 while inverting it. In the course of this conveyance, immediately after the original MS is reversed, it passes through the first fixed reading unit 151 of the scanner 150. At this time, the image on the first surface of the document MS is read by the first fixed reading unit 151 of the scanner 150.

Next, the configuration and operation of the recording paper feeding device 40 will be described.
5 and 6 are enlarged schematic views of the pickup section of the recording paper feeding device 40 in the present embodiment.
FIG. 7 is a schematic diagram of the pickup unit as viewed from the recording paper conveyance direction.
In the present embodiment, a pickup roller 61 as a sheet feeding rotating body is supported rotatably with respect to the pickup arm 62. The pickup arm 62 is rotatably attached to a rotation shaft (feed roller shaft 64) of a feed roller 63 that constitutes the separation feeding means 45. The pickup arm 62 is swingable about the feed roller shaft 64 as a rotation center, and the pickup roller 61 can be brought into contact with and separated from the upper surface of the uppermost recording paper P1 by the swing.

  The pickup arm 62 is rotated in a direction in which the pickup roller 61 is brought into contact with the upper surface of the recording paper P at a portion of the pickup arm 62 opposite to the support portion of the pickup roller 61 across the rotation center of the pickup arm 62. A paper feed pressure spring 65 is attached as a biasing means for biasing in the direction. The pickup roller 61 comes into contact with the upper surface of the recording paper P at a desired contact pressure (paper feeding pressure) by the force that rotates the pickup arm 62 by the biasing force of the paper feeding pressure spring 65.

  Further, the recording paper feeding device 40 is provided with a lift arm 66 configured to be rotatable about a rotation shaft 66b. When the lift arm 66 rotates about the rotation shaft 66b, the abutting end portion 66a of the lift arm 66 is located on the opposite side of the pickup arm 62 from the support position of the pickup roller 61 with the rotation center of the pickup arm 62 interposed therebetween. It approaches and separates from the 62 part. When the contact end portion 66 a of the lift arm 66 contacts the pickup arm 62, the pickup arm 62 rotates in a direction against the urging force of the paper feed pressure spring 65. Accordingly, the pickup roller 61 can be separated from the upper surface of the recording paper P as shown in FIG. On the other hand, when the contact end portion 66a of the lift arm 66 is separated from the pickup arm 62, the pickup arm 62 is rotated by the urging force of the paper feed pressure spring 65, and the pickup roller 61 is moved to the recording paper P as shown in FIG. Can be brought into contact with the upper surface of the sheet at a desired sheet feeding pressure.

  The lift arm 66 is urged by a lift arm return spring 67 as an urging means for urging the lift arm 66 in a direction in which the abutment end portion 66 a abuts the pickup arm 62. Further, a pickup solenoid 68 is connected to the lift arm 66, and when the pickup solenoid 68 is in a suction state, the lift arm 66 rotates in a direction against the urging force of the lift arm return spring 67, and the lift arm 66. The abutting end portion 66 a is separated from the pickup arm 62. On the contrary, when the pickup solenoid 68 is released from the suction state, the lift arm 66 is rotated by the urging force of the lift arm return spring 67, and the contact end portion 66 a of the lift arm 66 contacts the pickup arm 62. With such a configuration, by controlling the pickup solenoid 68, the contact / separation operation of the pickup roller 61 with respect to the upper surface of the recording paper P can be controlled.

  Further, the recording paper feeding device 40 in the present embodiment is provided with a reverse roller 69 as a return rotating body that is in contact with the feed roller 63 and is given a rotational torque in the sheet returning direction (recording paper returning direction). Yes. The reverse roller 69 and the feed roller 63 constitute a separating / feeding means 45. The feed roller 63 is rotationally driven in the sheet feeding direction (recording paper feeding direction) by rotating the feed roller shaft 64 in the direction indicated by reference numeral F in FIG. 7 by a driving force from a driving source (not shown). The uppermost recording paper P1 is fed in contact with the uppermost recording paper P1 sent out by.

  On the other hand, the rotating shaft (reverse roller shaft) 70 of the reverse roller 69 is also rotationally driven in the direction indicated by the symbol R in FIG. 7 by a driving force from a driving source (not shown). However, the reverse roller 69 is attached to the reverse roller shaft 70 via the torque limiter 71. The torque limiter 71 is attached so that its inner ring 71a rotates integrally with the reverse roller shaft 70, and its outer ring 71b rotates so as to rotate integrally with the reverse roller 69. When the torque generated between the inner ring 71a and the outer ring 71b is less than a specified value, the inner ring 71a and the outer ring 71b rotate together. However, when torque exceeding the specified value is generated, the inner ring 71a and the outer ring 71b Rotates relative to each other.

  With such a configuration, when the reverse roller 69 is in direct contact with the feed roller 63 and when the reverse roller 69 is in contact with the feed roller 63 through only one sheet of recording paper P, the inner ring 71a Torque exceeding the specified value is generated between the outer ring 71 b and the reverse roller 69 rotates along with the feed roller 63. On the other hand, when the reverse roller 69 is in contact with the feed roller 63 via two or more recording sheets P, the torque generated between the inner ring 71a and the outer ring 71b is specified because the frictional force between the recording sheets is small. The reverse roller 69 rotates together with the reverse roller shaft 70 and rotates in the recording paper returning direction.

  By such an operation of the reverse roller 69, even when multiple sheets of recording paper enter the separation nip between the feed roller 63 and the reverse roller 69, the uppermost layer in contact with the feed roller 63 is generated. The recording paper other than the recording paper P1 is returned to the paper feed cassette 42 by the rotation operation of the reverse roller 69 in the recording paper returning direction. As a result, the recording paper P passing through the separation nip between the feed roller 63 and the reverse roller 69 can be limited to one sheet, and the occurrence of double feed is suppressed. The recording sheet returned by the reverse roller 69 is returned until it hits the end fence 42b of the sheet feeding cassette 42 at the maximum.

  The feed roller 63 is attached to the feed roller shaft 64 via a one-way clutch that is rotatable in the recording paper feed direction. Thus, even if the recording paper P fed through the separation nip is given a conveying force by the conveying roller pair 46, the registration roller pair 33, etc. on the downstream side in the recording sheet conveying direction, the feed roller 63 is conveyed. The transport load is reduced.

Next, the feeding operation of the recording paper P by the recording paper feeding device 40 will be described.
After the recording paper P to be used for image formation is loaded on the paper feed tray 42a constituting the bottom of the paper feed cassette 42, when the copy start button 158 of the operation unit 108 in the copying machine 500 is pressed, the pickup solenoid 68 is sucked. It becomes a state. As a result, the pickup arm 62 swings around the feed roller shaft 64 in a direction in which the pickup roller 61 is brought into contact with the upper surface of the recording paper P. However, the pickup arm 62 swings only to a predetermined lower limit position by a stopper (not shown). Specifically, the pickup arm 62 swings to a position where the shielding plate 62a provided in a part of the pickup arm 62 shields the detection unit of the upper limit sensor 72, and is positioned at that position (lower limit position). At this time, the pickup roller 61 has not yet contacted the upper surface of the recording paper P.

  Thereafter, the paper feed table 42a on which the recording paper P is stacked is started to rise by a paper feed table lifting mechanism (not shown). In the middle of this ascent, the upper surface of the recording paper P comes into contact with the pickup roller 61. When the pickup roller 61 is pushed up by contact with the upper surface of the recording paper P that is being raised, the shielding plate 62a of the pickup arm 62 is removed from the detection unit of the upper limit sensor 72. When the upper limit sensor 72 detects this, the ascending drive by the paper feed table elevating mechanism stops.

  By such an operation, the upper surface of the recording paper P (upper surface of the uppermost recording paper P1) stacked on the paper feed tray 42a is positioned at a predetermined height optimum for feeding and the pickup roller 61 is supplied. The abutting force of the paper pressure spring 65 makes contact with a desired paper feed pressure.

  After that, when the feed roller shaft 64 is rotationally driven in the direction of reference F in FIG. 7, the feed roller 63 is rotationally driven, and the reverse roller 69 that is in contact with the feed roller 63 rotates along with the feed roller 63. A feed roller gear 73 is fixed to the feed roller 63, and an idler gear 75 is engaged with the feed roller gear 73. The idler gear 75 meshes with a pickup roller gear 74 fixed to the pickup roller 61. Therefore, when the feed roller shaft 64 is rotationally driven in the direction indicated by the symbol F in FIG. 7, the pickup roller 61 is also rotationally driven.

  When the pickup roller 61 is rotationally driven in this way, the uppermost recording paper P1 on the paper feed table 42a in contact with the pickup roller 61 is sent out to the feed roller 63 and the reverse roller 69 side. Then, when there is no command for feeding the next recording paper P2, as shown in FIG. 6, the feeding (not shown) as the contact / separation control means is performed at the timing when the uppermost recording paper P1 is completely held in the separation nip. Energization to the pickup solenoid 68 is stopped by a command from the paper control unit. As a result, the lift arm 66 is rotated by the urging force of the lift arm return spring 67, and the pickup arm 62 swings against the urging force of the paper feed pressure spring 65 in conjunction with this. It is separated from the upper surface of the uppermost recording paper P1 being fed.

  When the pickup roller 61 is separated from the upper surface of the uppermost recording paper P1 being fed, the force by which the pickup roller 61 presses the uppermost recording paper P1 against the lower recording paper P2 is released. Therefore, the frictional force between the uppermost recording paper P1 and the recording paper P2 is reduced, and the possibility that the recording paper P2 is sent out as the uppermost recording paper P1 is fed is reduced. As a result, the occurrence of double feeding is suppressed. The recording paper P is continuously fed by the feed roller 63 until at least the recording paper P is conveyed by the first conveyance roller pair 46 on the downstream side in the recording paper conveyance direction.

FIG. 8 is a schematic diagram illustrating a configuration of a detection unit that detects the rotation operation of the reverse roller 69.
In the present embodiment, an encoder 76 is attached to the outer ring 71 b of the torque limiter 71 so as to have a coaxial positional relationship with the reverse roller 69. For example, as shown in FIG. 8, four slits 76 a are formed on the disk surface of the encoder 76 at equal intervals in the circumferential direction. The encoder sensor 77 is arranged so that its detection part is located in a part of the circular orbit through which the slit 76a passes when the encoder 76 rotates. Here, an example in which the rotation operation of the reverse roller 69 is detected by detecting the slit 76a of the encoder 76 with the encoder sensor 77, but any detection means capable of detecting the rotation operation of the reverse roller 69 is possible. Not limited to.

Next, control of the contact / separation operation of the pickup roller 61 with respect to the upper surface of the recording paper P, which is a characteristic part of the present invention, will be described.
In the present embodiment, a plurality of sheets of recording paper P are fed to a separation nip between the feed roller 63 and the reverse roller 69 during continuous feeding for continuously feeding a plurality of recording papers P or during feeding of one recording paper P1. As long as there is no overlap sending in which the recording paper P enters, until the next recording paper P2 starts to be fed, as shown in FIG. 5, the recording paper P loaded on the paper feed table 42a is loaded with the pickup roller 61. Keep in contact with the top surface of the. On the other hand, in the case where duplicate feeding occurs during feeding of one recording paper P1, as shown in FIG. 6, the pickup roller 61 is separated from the upper surface of the recording paper P stacked on the paper feed table 42a. Then, the pickup roller 61 is brought into contact with the upper surface of the recording paper P (upper surface of the recording paper P2) at a predetermined timing before starting the next recording paper P2, and the paper feeding operation for the recording paper P2 is executed. .

  In the present embodiment, it is detected from the output result of the encoder sensor 77 described above whether or not the duplicate delivery has occurred during the feeding of one recording paper P1. More specifically, by detecting that the reverse roller 69 rotates (reversely rotates) in the recording paper return direction during feeding of one recording sheet P1, it is detected that duplicate feeding has occurred. The reverse roller 69 rotates reversely when a plurality of recording sheets P enter the separation nip and the torque limiter 71 is activated. Therefore, it is possible to detect whether or not duplicate sending has occurred by detecting whether or not the reverse rotation of the reverse roller 69 is detected.

  Here, the rotation direction of the reverse roller 69 cannot be directly detected from the output result of the encoder sensor 77 of the present embodiment. Therefore, the rotation direction of the reverse roller 69 in the present embodiment is detected as follows. That is, in the present embodiment, the rotation speed of the reverse roller shaft 70 is set to approximately ½ of the rotation speed of the feed roller shaft 64. Therefore, if only one sheet of recording paper P is sandwiched in the separation nip between the feed roller 63 and the reverse roller 69, the reverse roller 69 moves along with the recording paper P fed by the feed roller 63. Since it rotates, it rotates at the same rotational speed as the rotational speed of the feed roller 63. On the other hand, when a plurality of recording sheets P are sandwiched in the separation nip, the reverse roller 69 rotates integrally with the reverse roller shaft 70, and thus rotates at a rotational speed that is approximately ½ of the rotational speed of the feed roller 63. . In the present embodiment, due to such a difference in the rotation speed of the reverse roller 69, the reverse roller 69 rotates in the forward direction (rotates in the recording paper feed direction) or reversely rotates (rotates in the recording paper return direction). Detect whether or not

FIG. 9 is a graph showing an example of the output signal S of the encoder sensor 77.
As shown in FIG. 9, the reverse roller 69 immediately after the start of paper feeding rotates forward with the feed roller 63 because the recording paper P has not reached the separation nip. At this time, the rotation speed of the reverse roller 69 is the same as that of the feed roller 63, and the output signal S of the encoder sensor 77 has a signal interval ΔT1. For example, when the two recording papers P are sent out by the pickup roller 61 and then the two recording papers P enter the separation nip, the reverse roller 69 is rotated at a rotational speed that is approximately ½ of the rotational speed of the feed roller 63. , Reverse rotation. The output signal S of the encoder sensor 77 at this time has a signal interval ΔT2 that is approximately twice the signal interval ΔT1 during forward rotation. Thereafter, when only the uppermost recording paper P1 remains in the separation nip, the reverse roller 69 rotates forward with the uppermost recording paper P1. Also at this time, the rotation speed of the reverse roller 69 is the same as that of the feed roller 63, and the output signal S of the encoder sensor 77 has a signal interval ΔT1.

  The paper feed control unit of the present embodiment observes the signal interval of the output signal S of the encoder sensor 77, and when the signal interval is detected to have changed from ΔT1 to ΔT2, the reverse roller 69 reversely rotates. That is, it is detected that duplicate transmission has occurred. When the sheet feeding control unit detects the occurrence of duplicate sending in this manner, the feeding to the pickup solenoid 68 is stopped, the suction state of the pickup solenoid 68 is released, and the pickup roller 61 is placed on the sheet feeding table 42a. It is separated from the upper surface of the stacked recording paper P (the upper surface of the uppermost recording paper P1 currently fed). As a result, the force with which the pickup roller 61 presses the uppermost recording paper P1 against the lower recording paper P2 is released, the frictional force between the uppermost recording paper P1 and the recording paper P2 is reduced, and the uppermost recording paper P1 is fed. The possibility of the recording paper P2 being sent out along with the paper is reduced. Therefore, the occurrence of double feeding accompanying the feeding of the uppermost recording paper P1 is suppressed.

  On the other hand, during the continuous feeding, the paper feed control unit of the present embodiment does not change the signal interval of the output signal S of the encoder sensor 77 from ΔT1 to ΔT2, but is kept in the suction state of the pickup solenoid 68 while it is maintained at ΔT1. To maintain. Accordingly, as long as the signal interval is maintained at ΔT1 (as long as the reverse roller 69 is rotating forward), the pickup roller 61 remains in contact with the upper surface of the recording paper P stacked on the paper feed table 42a. In this case, no redundant feeding occurs and no double feeding occurs, so that the unnecessary contact / separation operation of the pickup roller 61 can be omitted. Therefore, vibration, noise, or power consumption due to the contact / separation operation of the pickup roller 61 can be suppressed.

  In addition, due to the contact and separation operation of the pickup roller 61, the pickup roller 61 is likely to run idle due to the bounce when the pickup roller 61 collides with the recording paper P during the high-speed separation and conveyance operation. There is also a problem that a minute transport loss that is a factor is likely to occur. According to the present embodiment, an unnecessary contact / separation operation of the pickup roller 61 can be omitted, so that this problem can also be suppressed.

FIG. 10 is a flowchart showing control of the paper feeding operation in the present embodiment.
When the copy start button 158 of the operation unit 108 in the copying machine 500 is pressed, the pickup solenoid 68 is energized to be in a suction state, and the pickup roller 61 is lowered to the lower limit position (S1). Further, a sheet feeding table raising / lowering motor (not shown) for raising and lowering the sheet feeding table 42a loaded with recording paper (paper) is turned on (S2). When the upper limit sensor 72 detects that the pickup roller 61 is pushed up onto the upper surface of the recording paper P that has been raised by the ascent of the paper feed table 42a and reaches the upper limit position (Y in S3), the paper feed table lifting motor is moved. It is turned off (S4), and the ascent of the paper feed table 42a is stopped.

  Next, driving of the feed roller shaft 64 and the reverse roller shaft 70 is started, and rotation driving of the feed roller 63 and the pickup roller 61 is started (S5). At this time, the reverse roller 69 rotates along with the feed roller 63. Thereafter, the uppermost recording paper P1 is sent out by the rotation of the pickup roller 61, and the uppermost recording paper P1 enters the separation nip between the feed roller 63 and the reverse roller 69. At this time, the output signal of the encoder sensor 77 is observed to detect whether or not the reverse roller 69 has rotated backward (S6).

  While the reverse rotation of the reverse roller 69 is not detected (N in S6), the leading edge of the recording paper (paper) is detected from the detection result of the registration roller sensor (not shown) disposed near the entrance of the registration roller pair 33. It is determined whether or not the roller pair 33 has been reached (S11). If it is determined that the reverse end of the reverse roller 69 has not been detected and the leading edge of the recording paper has reached the registration roller pair 33 (Y in S11), the drive of the feed roller shaft 64 and the reverse roller shaft 70 is stopped. (S12). If the set number of prints has not yet been reached (N in S12), the feed table 42a is adjusted to the upper limit position as necessary (S2 to S4), and the feed roller 63 and the pickup roller 61 are rotated again. Driving is started (S5), and feeding of the next recording sheet is started. Accordingly, the pickup roller 61 starts the feeding operation of the next recording paper while being in contact with the upper surface of the recording paper stacked on the paper feed tray 42a. If the set number of prints has been reached (Y in S12), the paper feeding operation is terminated.

  On the other hand, when it is detected that the reverse roller 69 has been rotated reversely (Y in S6), the energization to the pickup solenoid 68 is turned off to cancel the suction state (S7). Accordingly, the pickup roller 61 is separated from the upper surface of the recording paper stacked on the paper feed table 42a, and the occurrence of double feeding is suppressed. Thereafter, it is determined whether or not the leading edge of the recording paper (paper) has reached the registration roller pair 33 from the detection result of a registration roller sensor (not shown) disposed near the entrance of the registration roller pair 33 (S8). . When it is determined that the leading edge of the recording paper has reached the registration roller pair 33 (Y in S8), the drive of the feed roller shaft 64 and the reverse roller shaft 70 is stopped (S9). If the set number of prints has not yet been reached (N in S10), the pickup solenoid 68 is turned on to return to the suction state, and the pickup roller 61 is lowered (S1). Then, if necessary, after adjusting the paper feed table 42a to the upper limit position (S2 to S4), the rotation of the feed roller 63 and the pickup roller 61 is started again (S5), and the next recording paper is fed. To start. If the set number of prints has been reached (Y in S10), the paper feeding operation is terminated.

[Modification 1]
Next, another example of detection means for detecting the rotation operation of the reverse roller 69 (hereinafter referred to as “Modification 1”) will be described.
FIG. 11 is a schematic diagram illustrating a configuration of a detection unit that detects the rotation operation of the reverse roller 69 in the first modification.
The detection means of the first modification is different from the above-described embodiment in which there is one encoder sensor in that two encoder sensors for detecting the slit 76a of the encoder 76 are used. In addition, the encoder 76 uses the thing by which the four slits 76a are formed in the circumferential direction at equal intervals similarly to the thing of the said embodiment. The two encoder sensors 77A and 77B in the first modification are disposed at a rotational position interval narrower than the rotational position interval (90 °) of the slit 76a on the encoder 76.

FIG. 12 is a graph showing an example of the output signals S1 and S2 of the two encoder sensors 77A and 77B.
In the first modification, the signal interval between the output signals S1 and S2 of the encoder sensors 77A and 77B when the reverse roller 69 is rotating forward is T1, and each encoder sensor when the reverse roller 69 is rotating reversely is T1. Let T2 be the signal interval between the output signals S1 and S2 of 77A and 77B. The signal interval T2 has a signal interval that is approximately twice the signal interval T1.

  The reverse roller 69 immediately after the start of paper feeding rotates forward with the feed roller 63 because the recording paper P has not reached the separation nip. At this time, the rotation speed of the reverse roller 69 is the same as that of the feed roller 63. At this time, as shown in FIG. 12, the signal based on the output signal S2 of the second encoder sensor 77B is delayed by ΔT3 from the signal based on the output signal S1 of the first encoder sensor 77A. Further, while the reverse roller 69 is rotating forward, the time from when the signal by the output signal S2 of the second encoder sensor 77B is generated until the signal by the output signal S1 of the first encoder sensor 77A is generated is shown in FIG. As shown in FIG. 12, ΔT4. In the first modification, since the interval between the rotational positions of the two encoder sensors 77A and 77B is narrower than the slit 76a on the encoder 76, the relationship ΔT3 <ΔT4 is obtained while the reverse roller 69 is rotating forward. Further, when the reverse roller 69 is rotating forward, the signal interval T1 of the output signal S2 of the second encoder sensor 77B is the signal interval T2 when the reverse roller 69 is rotating reversely, as in the above embodiment. Narrower than.

  On the other hand, in the case where an overlap feeding in which a plurality of recording sheets enter the separation nip occurs, the reverse roller 69 rotates in the reverse direction, so that a signal based on the output signal S1 of the first encoder sensor 77A is shown in FIG. Thus, it is delayed by ΔT5 from the signal by the output signal S2 of the second encoder sensor 77B. Further, while the reverse roller 69 is rotating in the reverse direction, the time from when the signal based on the output signal S1 of the first encoder sensor 77A is generated until the signal based on the output signal S2 of the second encoder sensor 77B is generated is shown in FIG. As shown in FIG. 12, ΔT6. Therefore, the relationship of ΔT5 <ΔT6 is obtained while the reverse roller 69 is rotating in the reverse direction. Further, when the reverse roller 69 is rotating in the reverse direction, the signal interval T2 of the output signal S2 of the second encoder sensor 77B is the signal interval T1 when the reverse roller 69 is rotating forward as in the case of the above embodiment. Wider than.

  Therefore, in the first modification, for example, when both the relationship of ΔT5 <ΔT6 and the relationship of T2≈2 × T1 are satisfied, it can be determined that the reverse roller 69 is rotating in the reverse direction.

[Modification 2]
Next, a modified example (hereinafter referred to as “modified example 2”) relating to control of the paper feeding operation will be described.
In the second modification, there are two types of image forming operation modes: a high speed mode in which the image forming speed (process speed) is high speed and a low speed mode in which the image forming speed is low. Since the recording paper feed speed and transport speed need to be changed according to the image forming speed, the transport speed is set to high in the high-speed mode, and the transport speed is low in the low-speed mode. Set to In the second modification, different sheet feeding operations are executed depending on whether the conveyance speed is set to high speed or low speed. Hereinafter, a description will be given focusing on differences from the control of the sheet feeding operation in the embodiment.

FIG. 13 is a flowchart showing control of the sheet feeding operation in the second modification.
After the sheet feed table 42a is raised to the upper limit position and the sheet feed table raising / lowering motor is turned off (ST1 to ST4), the sheet feed control unit determines whether the conveyance speed is set to high speed or low speed. Confirm (ST5). At this time, when the conveyance speed is set to a high speed (Y in ST5), as in the case of the above embodiment, if it is not detected that the reverse roller 69 is reversely rotated (N in ST12), the pickup roller No. 61 starts the feeding operation of the next recording paper while being in contact with the upper surface of the recording paper loaded on the paper feed tray 42a. That is, only when it is detected that the reverse roller 69 is rotated in the reverse direction (Y in ST12), the pickup solenoid 68 is controlled to separate the pickup roller 61 from the upper surface of the recording paper loaded on the paper feed table 42a. When the next recording paper is fed, the pickup roller 61 is again brought into contact with and separated from the top surface of the recording paper loaded on the paper feed table 42a. The rotation speed of the feed roller 63 and the pickup roller 61 is driven at a high speed corresponding to a high transport speed (ST11).

  On the other hand, when the conveyance speed is set to a low speed (N in ST5), in the second modification, the feed roller 63 and the pickup roller 61 are started to rotate regardless of whether or not the reverse roller 69 has rotated in the reverse direction. Then (ST6), after a predetermined time has elapsed, the energization to the pickup solenoid 68 is turned off to cancel the suction state (ST7). As a result, the pickup roller 61 is separated from the upper surface of the recording paper loaded on the paper feed table 42a. Thereafter, when it is determined that the leading edge of the recording paper (paper) has reached the registration roller pair 33 (Y in ST8), the driving of the feed roller shaft 64 and the reverse roller shaft 70 is stopped (ST9). The rotation speed of the feed roller 63 and the pickup roller 61 is driven at a low speed corresponding to the low transport speed (ST6).

  In the second modification, the pickup roller 61 is kept in contact with the upper surface of the recording paper loaded on the paper feed table 42a unless the reverse roller 69 is reversely rotated during high-speed conveyance. Only when it is detected that the reverse rotation has occurred, the contact / separation operation of the pickup roller 61 is executed. On the other hand, at the time of low speed conveyance, the contact operation of the pickup roller 61 is executed for each recording sheet regardless of whether or not the reverse roller 69 is reversely rotated.

[Modification 3]
Next, another modified example (hereinafter referred to as “modified example 3”) relating to control of the sheet feeding operation will be described.
In the above embodiment, when the reverse roller 69 is detected to rotate in reverse, the pickup roller 61 is contacted / separated. An operation of separating 61 from the upper surface of the recording sheet is executed. However, it is roughly divided into the following two cases that it is desired to suppress the double feed by separating the pickup roller 61 from the upper surface of the recording paper.

In the first case, the second and subsequent recording sheets are continuously returned to the paper feed cassette 42 until a large number of recording sheets enter the separation nip at the same time and the remaining one (the top recording sheet only) is reached. Case. In this first case, double feed is likely to occur. Therefore, it is desirable that the pickup roller 61 be separated from the upper surface of the recording paper to suppress double feed.
The second case is a case where the leading edge of the second recording sheet repeatedly enters the separation nip while feeding one recording sheet. In this second case, double feed is likely to occur, so it is desirable to suppress the double feed by separating the pickup roller 61 from the upper surface of the recording paper.

  Except for the first and second cases, there is a low possibility of double feeding without separating the pickup roller 61 from the upper surface of the recording paper. Rather, the pickup roller 61 is not separated and the pickup roller 61 is contacted and separated. In some cases, it may be preferable to reduce defects caused by operation. Therefore, in the third modification, it is detected whether or not the first and second cases have occurred, and the feeding operation is controlled according to the detection result. Hereinafter, a description will be given focusing on differences from the sheet feeding operation control in the second modification.

FIG. 14 is a flowchart showing control of the sheet feeding operation in the third modification.
In the third modification, it is detected as follows whether or not the first and second cases have occurred. That is, in the first and second cases, the reverse rotation amount of the reverse roller 69 during feeding of one recording sheet is a considerable rotation amount when the total is added. Therefore, in the third modification, the number of pulses of the output signal S of the encoder sensor 77 when the reverse roller 69 rotates in the reverse direction (the number of times the slit 76a of the encoder 76 passes through the detection area of the encoder sensor 77) is counted. .

  In the third modification, when it is detected that the reverse roller 69 is rotating in the reverse direction, the energization to the pickup solenoid 68 is not turned off, and the count value becomes a specified value or more (STP12). Then, the power supply to the pickup solenoid 68 is turned off (STP13). As a result, even if it is detected that the reverse roller 69 is rotating in reverse during feeding of one recording paper, if the reverse rotation is less than the specified amount, the pickup roller 61 is brought into contact with the upper surface of the recording paper. The next recording paper feeding operation is carried out without any change. On the other hand, if the total amount of reverse rotation of the reverse roller 69 becomes equal to or more than a specified amount during feeding of one recording sheet, the pickup roller 61 is separated from the upper surface of the recording sheet to suppress the occurrence of double feeding.

  When it is desired to suppress double feeding only in the first case where a large number of recording sheets enter the separation nip at the same time, it is not the total reverse rotation amount of the reverse roller 69 during the feeding of one recording sheet. The continuous reverse rotation amount when the reverse roller 69 continuously reversely rotates during feeding of one recording sheet may be observed. In this case, when the continuous reverse rotation amount exceeds a specified amount, the pickup roller 61 may be separated from the upper surface of the recording paper to suppress the occurrence of double feeding.

  As described above, in the present embodiment (including the above-described modifications, the same applies hereinafter), the sheet material feeding device according to the present invention is applied to the recording paper feeding device 40 that feeds the recording paper of the copying machine 500. Although the case has been described, for example, the present invention can also be applied as an apparatus that separates and conveys originals one by one from the original bundle in the ADF 51 of the copying machine 500.

What has been described above is merely an example, and the present invention has a specific effect for each of the following modes.
(Aspect A)
A sheet material stacking unit such as a paper feed cassette 42 on which a plurality of sheet materials such as the recording material P are stacked and stacked, and the uppermost recording paper loaded on the sheet material stacking unit by being rotationally driven by a drive input from a drive source A sheet feeding rotary body such as a pickup roller 61 that feeds the sheet material in contact with the uppermost sheet material such as P1, and the like; a pickup solenoid 68 that contacts and separates the uppermost sheet material and the sheet feeding rotary body; A recording paper feeding device 40 having contact / separation means such as a pickup arm 62 and separation feeding means 45 for separating and feeding the uppermost sheet material from the sheet material fed by the sheet feeding rotating body In the sheet material feeding apparatus, an encoder for detecting whether or not a duplicate feeding in which a plurality of sheet materials are fed to the separation feeding means by the sheet feeding rotating body has occurred. It is confirmed that duplicate feeding is not generated during feeding of a single sheet material during duplicate feeding detection means such as an encoder 76 and an encoder sensor 77 and continuous feeding of a plurality of sheet materials continuously. When the duplicate delivery detection means detects, the contact state between the sheet delivery rotator and the uppermost sheet material of the sheet material stacking unit is maintained until the sheet delivery rotator starts delivering the next sheet material. When the duplicate delivery detection means detects that duplicate delivery has occurred during feeding of one sheet material, the sheet delivery rotating body and the uppermost sheet material of the sheet material stacking unit are separated, and then Feeding that performs contact / separation control for controlling the contacting / separating means so that the sheet delivery rotating body and the uppermost sheet material are brought into contact with each other before the sheet delivery rotating body starts delivery of the next sheet material. Contact / separation of the control unit, etc. And having a means.
According to this, when there is no occurrence of overlapping feeding, which is a necessary condition for occurrence of double feeding, the contact state between the sheet feeding rotating body and the uppermost sheet material of the sheet material stacking section is maintained, and unnecessary contact and separation operations are performed. To avoid. On the other hand, when duplicate feeding, which is a necessary condition for occurrence of double feeding, occurs, the sheet feeding rotating body can be separated from the uppermost sheet material of the sheet material stacking unit to suppress double feeding.

(Aspect B)
In the above aspect A, the separation feeding unit rotates in the sheet feeding direction, contacts the uppermost sheet material fed by the sheet feeding rotating body, and feeds the uppermost sheet material, etc. And a return rotator such as a reverse roller 69 which is in contact with the feed rotator and is given a rotational torque in the sheet return direction. The uppermost sheet material is separated and fed by rotating in the sheet return direction by the rotational torque and returning the sheet material in contact with the return rotating body to the sheet material stacking section. The duplicate delivery detection means detects whether or not the duplicate delivery has occurred by detecting the rotational operation of the return rotating body.
According to this, it is possible to easily detect whether or not duplicate transmission has occurred.

(Aspect C)
In the aspect B, there is provided a rotation amount detection means for detecting a rotation amount of the return rotating body in the sheet return direction, and the contact / separation control means is configured to perform repeated feeding during continuous feeding and feeding of one sheet material. Even when the overlap sending detection means detects that the sheet has occurred, if the sheet return direction rotation amount detected by the return rotation amount detection means is not more than a specified amount, the contact control is not performed and the sheet is not executed. The contact state between the sheet feeding rotating body and the uppermost sheet material of the sheet material stacking unit is maintained until the feeding rotating body starts feeding the next sheet material.
According to this, it is possible to more appropriately grasp the case where it is desired to suppress the double feed by separating the sheet delivery rotating body from the uppermost sheet material of the sheet material stacking unit, and further reduce unnecessary contact / separation operations. However, occurrence of double feeding can be suppressed appropriately.

(Aspect D)
In the above aspect C, the contact / separation control unit is configured to supply the one sheet material even when the duplicate feeding detection unit detects that the duplicate feeding has occurred during the continuous feeding or feeding of the one sheet material. When the total amount of rotation in the sheet return direction detected by the return rotation amount detection means during feeding is equal to or less than a specified amount, the contact / separation control is not performed, and the sheet feeding rotating body feeds the next sheet material. The contact state between the sheet delivery rotating body and the uppermost sheet material of the sheet material stacking unit is maintained until the operation is started.
According to this, not only the first case in which a large number of recording sheets enter the separation nip at the same time, but also the leading edge of the second recording sheet repeatedly repeats the separation nip during the feeding of one recording sheet. As for the second case that enters, the occurrence can be properly grasped and the occurrence of double feed can be suppressed.

(Aspect E)
In any one of the above aspects A to D, the first feeding control mode such as the high speed mode for feeding the sheet material at different feeding speeds (conveyance speeds) and the second feeding control mode such as the low speed mode are used. A feed speed control means provided, and the contact / separation control means, during continuous feeding, when the feed speed control means controls the feed speed of the sheet material in the first feed control mode, When the contact / separation control is executed and the feeding speed control means controls the feeding speed of the sheet material in the second feeding control mode, duplicate feeding occurs during feeding of one sheet material. Even when the duplicate delivery detecting means detects that there is no sheet, the sheet delivery rotator is separated from the uppermost sheet material of the sheet material stacking portion at a predetermined timing, and then the sheet delivery rotator is Before starting to feed the sheet material, And executes a separate contact and separation control for controlling the moving means so as to contact the rotating body and the outermost upper sheet material.
According to this, it is possible to appropriately perform the contact / separation operation in accordance with the feeding speed, and to achieve both appropriate avoidance of unnecessary contact / separation operation and suppression of double feed. That is, according to this aspect, in the first feeding control mode in which the feeding speed is high, the separation operation is not necessarily executed, so that the contact pressure when the sheet feeding rotating body contacts the sheet material remains unstable. There is no need to start conveying the sheet material. Further, in the second feeding control mode in which the feeding speed is slow, the friction load between the uppermost sheet material and the second sheet material is eliminated, so that power consumption during conveyance can be reliably reduced.

(Aspect F)
In the aspect E, the first feeding control mode is a control mode in which a feeding speed is higher than that of the second feeding control mode.
According to this, in the high-speed mode, by performing the contact / separation control, an unnecessary contact / separation operation is avoided, thereby suppressing the occurrence of paper feed delay due to the contact / separation operation. In addition, as a result of reducing the instability of the paper feed pressure due to the contact / separation operation, it is possible to improve the occurrence of non-feed and double feed in the high-speed mode.

(Aspect G)
In an image forming apparatus such as a copying machine 500 that forms an image on a sheet material fed by a sheet material feeding device such as the recording paper feeding device 40, any one of the above aspects A to F is used as the sheet material feeding device. The sheet material feeding device according to the above aspect is used.
According to this, while avoiding unnecessary contact / separation operation between the sheet delivery rotating body and the uppermost sheet material of the sheet material stacking unit, while suppressing problems such as noise, vibration and increase in power consumption due to the contact / separation operation, Image formation can be performed stably by appropriately suppressing double feeding.

(Aspect H)
In an image reading apparatus such as an image reading unit 50 that reads an image on a sheet material fed by a sheet material feeding apparatus such as an ADF 51, the sheet material feeding apparatus is any one of the above aspects A to F. Such a sheet material feeding device is used.
According to this, while avoiding unnecessary contact / separation operation between the sheet delivery rotating body and the uppermost sheet material of the sheet material stacking unit, while suppressing problems such as noise, vibration and increase in power consumption due to the contact / separation operation, It is possible to stably read an image by appropriately suppressing double feeding.

DESCRIPTION OF SYMBOLS 1 Image formation part 2 Optical writing device 3 Process unit 4 Photoconductor 5 Charging device 6 Developing device 24 Transfer unit 25 Intermediate transfer belt 26 Primary transfer roller 28 Paper transfer unit 29 Paper transfer belt 31 Secondary transfer roller 33 Registration roller pair 34 Fixing device 40 Recording paper feed device 41 Paper bank 42 Paper feed cassette 42a Paper feed tray 43 Pickup roller 44 Recording paper feed path 45 Separation feeding means 46 Conveying roller pair 50 Image reading unit 51 ADF
61 Pickup roller 62 Pickup arm 62a Shield plate 63 Feed roller 64 Feed roller shaft 65 Feed pressure spring 66 Lift arm 66a Abutting end 66b Rotating shaft 67 Lift arm return spring 68 Pickup solenoid 69 Reverse roller 70 Reverse roller shaft 71 Torque limiter 72 Upper limit sensor 76 Encoder 76a Slit 77 Encoder sensor 150 Scanner 500 Copying machine

JP 2009-40607 A Japanese Patent Publication No. 4-13264

Claims (7)

A sheet material stacking unit that stacks a plurality of sheet materials,
A sheet sending rotating body that rotates by a drive input from a drive source and sends out the sheet material in contact with the uppermost sheet material stacked on the sheet material stacking unit;
Contact / separation means for contacting / separating the uppermost sheet material and the sheet delivery rotating body;
In a sheet material feeding apparatus having separation feeding means for separating and feeding the uppermost sheet material from the sheet material fed by the sheet feeding rotating body,
A duplicate delivery detection means for detecting whether or not a duplicate delivery in which a plurality of sheet materials are sent to the separation feeding means by the sheet delivery rotating body;
During continuous feeding in which a plurality of sheet materials are continuously fed, when the duplicate feeding detection means detects that duplicate feeding has not occurred during feeding of one sheet material, the sheet feeding rotation The sheet feeding rotating body and the uppermost sheet material of the sheet material stacking section are kept in contact with each other until the body starts feeding the next sheet material, and duplicate feeding occurred during feeding of one sheet material. When the duplicate delivery detection means detects this, the sheet delivery rotator is separated from the uppermost sheet material of the sheet material stacking unit, and then the sheet delivery rotator starts delivery of the next sheet material. A sheet material feeding apparatus comprising contact / separation control means for performing contact / separation control for controlling the contact / separation means so that the sheet feeding rotating body and the uppermost sheet material are brought into contact with each other before . In the sheet material feeding device according to claim 1,
The separation feeding unit is configured to rotate in the sheet feeding direction and contact the uppermost sheet material fed by the sheet feeding rotating body to feed the uppermost sheet material, and the feeding rotating body And a return rotator to which a rotational torque in the sheet return direction is applied, and when the redundant feeding occurs, the return rotator is driven to rotate in the sheet return direction by the rotational torque, and the return By returning the sheet material that is in contact with the rotating body to the sheet material stacking unit, the uppermost sheet material is separated and fed,
The sheet feeding apparatus according to claim 1, wherein the duplicate delivery detection means detects whether or not the duplicate delivery has occurred by detecting a rotation operation of the return rotating body. In the sheet material feeding device according to claim 2,
Rotation amount detection means for detecting the amount of rotation of the return rotator in the sheet return direction,
The contact / separation control means detects the sheet return detected by the return rotation amount detection means even when the duplicate delivery detection means detects that duplicate delivery has occurred during continuous feeding or feeding of one sheet material. When the direction rotation amount is not more than a specified amount, the contact / separation control is not executed, and the sheet delivery rotating body and the sheet material stacking unit are not operated until the sheet delivery rotation body starts feeding the next sheet material. A sheet material feeding device characterized by maintaining a contact state with the uppermost sheet material. In the sheet material feeding device according to claim 3,
The contact / separation control means returns the return during the feeding of one sheet material even when the duplicate feeding detection means detects that the duplicate feeding has occurred during feeding of the one sheet material during continuous feeding. When the total amount of rotation in the sheet return direction detected by the rotation amount detection means is equal to or less than a specified amount, the contact / separation control is not executed, and the sheet delivery rotating body starts feeding the next sheet material. A sheet material feeding device that maintains a contact state between a sheet feeding rotating body and the uppermost sheet material of the sheet material stacking unit. In the sheet material feeding device according to any one of claims 1 to 4,
Have a feeding speed control means and a first feeding control mode and the second feeding control mode feeding speed is slower than the first feeding control mode for feeding the sheet material at a predetermined feed speed And
The contact / separation control means executes the contact / separation control when the feeding speed control means controls the feeding speed of the sheet material in the first feeding control mode during continuous feeding. When the speed control means controls the sheet material feeding speed in the second feeding control mode, the duplicate feeding detection means detects that no duplicate feeding has occurred during feeding of one sheet material. Even when the sheet feeding rotator is separated from the uppermost sheet material of the sheet material stacking unit at a predetermined timing, the sheet feeding rotator is then moved before the next sheet material starts to be fed. A sheet material feeding device that performs another contact / separation control for controlling the contact / separation means so that the sheet feeding rotating body and the uppermost sheet material are brought into contact with each other. In an image forming apparatus that forms an image on a sheet material fed by a sheet material feeding device,
An image forming apparatus using the sheet material feeding device according to any one of claims 1 to 5 as the sheet material feeding device. In an image reading device that reads an image on a sheet material fed by a sheet material feeding device,
An image reading apparatus using the sheet material feeding device according to any one of claims 1 to 5 as the sheet material feeding device.

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