JP2018158783A - Paper feeder, document reader, image forming unit, and post-processing unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper feeder which can inhibit fluctuation of a conveyance amount of paper.SOLUTION: A paper feeder comprises a pair of conveyance rollers which can be rotatably driven to convey paper, a pair of loop forming rollers which are located on the upstream side of a conveyance route compared with the pair of conveyance rollers, and can be rotatably driven so that the loop of a predetermined amount is formed between the pair of conveyance rollers and the pair of loop forming rollers, a first detection unit of plural pieces of paper which is located near the pair of loop forming rollers, and detects whether the plural pieces of paper are present or not on a nip of the pair of loop forming rollers, and a control unit which controls the pair of loop forming rollers. The pair of loop forming rollers include a paper feed roller which is rotatably driven so as to send out the paper in the conveyance direction, and a separation roller which comes in pressure contact with the paper feed roller, and has a torque limiter that acts so as to enable following driven rotation in the conveyance direction when a predetermined power amount adds in the conveyance direction. The control unit adjusts a rotation driven amount of the paper feed roller on the basis of detection results from the first detection unit of plural pieces of paper.SELECTED DRAWING: Figure 3

Description

  The present disclosure relates to a paper feeding device that transports paper.

  An MFP (Multifunction Peripheral) has a scanner function, a copying function, a function as a printer, a facsimile function, a data communication function, and a server function.

  An image forming apparatus (image recording apparatus) such as an MFP, a printer, a copier, or a facsimile, an image reading apparatus, and the like are equipped with a paper feeding device. The image forming apparatus is required to have reproducibility of the input image, and the image reading apparatus is required to be reproducible for the original image. In order to improve the reproducibility of an input image or a document image, a paper feeding device capable of accurately transporting paper is required.

  When the image forming apparatus prints an image on a sheet, the conventional sheet feeding apparatus conveys the sheet by the following operation.

  The sheet feeding device is a separation unit configured by a sheet feeding roller and a separating unit, separates one sheet from a plurality of sheets stacked on a sheet feeding tray, and introduces the sheet into the sheet feeding device. The paper feeding device abuts the leading end of the introduced paper against the nip of the stopped pair of registration rollers.

  Next, the paper feeding device continuously rotates the loop forming roller set on the upstream side of the registration roller pair, thereby forming a loop of a predetermined loop amount on the paper between the registration roller pair and the loop forming roller. Form. As a result, the inclination generated in the sheet during conveyance on the upstream side in the conveyance direction with respect to the registration roller pair is corrected.

  Thereafter, the paper feeding device stops the paper feeding roller and transports the paper by the registration roller pair and the reading roller. An image is formed when the sheet passes through an image forming position provided on the downstream side of the pair of registration rollers.

  When the image reading apparatus reads an image of a document, the paper feeding device conveys the document by the same operation as described above, and reads the image when the document passes through the image reading position.

  Each of the conveyance units that convey the paper, such as a paper feed roller, a separation unit, a registration roller, or a reading roller, is connected to another conveyance unit that is adjacent on the upstream side or the downstream side as the conveyance of the paper or the document proceeds. Deliver paper between. When the paper or document is transferred between the two transport units, the load torque received by the paper from the transport unit varies, and the transport speed of the paper or document temporarily varies. If the paper transport speed fluctuates during image formation on the paper, the quality of the image will be degraded. Further, if the document transport speed fluctuates during the reading of the document image, the quality of the scanned image is degraded. Therefore, it is important to suppress fluctuations in the conveyance speed when the paper or document is transferred between the conveyance units, and various methods have been proposed (see Patent Documents 1 and 2).

  Here, when the transport unit has a role of merely transporting paper, such as a pair of registration rollers and a pair of reading rollers, the transport speed can be adjusted by adjusting the pressure contact force such as separation of the transport roller pair. Variation can be suppressed relatively easily. On the other hand, when the conveyance unit is a separation unit that separates a single sheet or document from a plurality of sheets or documents, it is difficult to suppress variations in conveyance speed in the same manner as other conveyance units. is there. The feeding roller and the separation unit that constitute the separation unit are appropriately set with the frictional force between the feeding roller and the separation unit, the frictional force between each of the feeding roller and the separation unit and the paper or the document, etc. This is because it is necessary to

  In recent years, a torque limiter system is being adopted as a paper or document separation system in a paper feeder from the viewpoint of reliability and cost performance. This method is a method in which a winding roller with a torque limiter using a torsion coil spring and a magnet is used as the winding portion. In the torque limiter method, when only one sheet or document enters the nip of the separation unit, the torque limiter is loosened and the rolling roller follows the sheet or document and rotates forward. On the other hand, when two or more sheets or originals enter the nip of the separation unit, the slip torque of the torque limiter overcomes the frictional force between the sheets or between the originals, and the second or subsequent sheets or originals are caused by the torque of the torque limiter. Remains in the nip of the separator.

JP2015-196594A JP-A-2006-124142

  As described above, the torque limiter method is excellent in curling properties, but the torque limiter originally acts as a braking force for conveying paper downstream, so that only one sheet is used as the curling unit. When a sheet enters and when a plurality of sheets enter, the braking force acting on one sheet that should be sent out is different, and the slip amount between the sheet feeding roller and the sheet to be sent out is different ( A difference in the conveyance speed of the paper occurs).

  As a result, the amount of loop formed between the pair of registration rollers varies, and if the amount of loop decreases, the nip of the registration roller pair at the front end of the paper cannot be reliably matched, and in order to eliminate this, the loop amount If the setting is increased, the loop will be excessively formed, resulting in a distorted loop shape, an impact sound hitting the guide of the nip of the registration roller pair will be generated, and when the paper is fed from the nip of the registration roller pair, bending, wrinkles, etc. There is a problem that damage occurs.

  The present disclosure is for solving the above-described problems, and an object of the present disclosure is to provide a paper feeding device, a document reading device, an image forming device, and a post-processing device capable of suppressing fluctuations in the transport amount of paper. It is.

  A sheet feeding device according to an aspect is disposed between a pair of conveyance rollers that can be driven to rotate to convey a sheet and a conveyance roller pair upstream of the conveyance roller pair, and a predetermined amount of loop is formed between the conveyance roller pair. A loop forming roller pair that can be driven to rotate, and a first plurality of sheets that are arranged in the vicinity of the loop forming roller pair and detect whether there are a plurality of sheets on the nip of the loop forming roller pair A paper detection unit and a control unit that controls the loop forming roller pair are provided. The pair of loop forming rollers is pressed against the paper feed roller that is rotationally driven so as to feed the paper in the transport direction, and can be driven to rotate in the transport direction when a predetermined amount of force is applied in the transport direction. And a rolling roller having a torque limiter acting as described above. The control unit adjusts the rotational driving amount of the paper feed roller based on the detection result from the first multiple sheet detection unit.

  Preferably, the control unit detects a plurality of sheets by the first plurality of sheet detection unit when the first plurality of sheet detection unit detects a rotation driving amount of the sheet feeding roller when the first plurality of sheet detection unit detects the plurality of sheets. It is adjusted so as to be smaller than the rotational driving amount of the paper feed roller when there is no sheet.

Preferably, the control unit adjusts the rotational driving amount of the paper feed roller for each paper type.
Preferably, a sheet thickness determining unit that can determine the thickness of the conveyed sheet is further provided. The control unit adjusts the rotational driving amount of the paper feed roller based on the determination result of the paper thickness determination unit and the detection result of the first multiple sheet detection unit.

  Preferably, an input operation unit that can set the thickness of the paper according to the operation is further provided. The paper thickness determining unit determines the thickness of the paper according to the operation of the input operation unit.

  Preferably, a paper leading edge detection unit that detects the leading edge of the paper conveyed from the pair of loop forming rollers is further provided. The sheet thickness determining unit is provided between the sheet leading end detecting unit and the loop forming roller pair.

  Preferably, a paper leading edge detection unit that detects the leading edge of the paper conveyed from the pair of loop forming rollers is further provided. The paper leading edge detection unit includes a movable member that is provided on the conveyance path and is movable according to the feeding of the paper, and a detection member that detects the state of the movable member.

  Preferably, the image forming apparatus further includes a second multiple sheet detection unit provided between the conveyance roller pair and the loop forming roller pair.

  Preferably, the control unit stops the paper feed roller when the second plurality of sheets detection unit detects a plurality of sheets.

  A document reading device according to a certain aspect includes the above-described sheet feeding device and a document reading unit that reads an image on a sheet fed by the sheet feeding device.

  An image forming apparatus according to an aspect includes the above-described sheet feeding device and an image forming unit that forms an image on a sheet fed by the sheet feeding device.

  A post-processing device according to a certain aspect includes the above-described paper feeding device and a post-processing unit that performs predetermined processing on the paper fed by the paper feeding device.

  The above and other objects, features, aspects and advantages of the present invention will become apparent from the following detailed description of the present invention taken in conjunction with the accompanying drawings.

  The present invention can suppress fluctuations in the amount of paper transport.

1 is a cross-sectional view illustrating a configuration of an image forming apparatus based on Embodiment 1. FIG. It is sectional drawing which shows the structure of ADF1 based on Embodiment 1. FIG. 1 is a block diagram illustrating a configuration of an image forming apparatus based on Embodiment 1. FIG. FIG. 3 is a diagram illustrating a configuration of peripheral portions of registration rollers 13 and 14, a sheet feeding roller 11, and a separating roller 12 based on the first embodiment. It is a figure explaining the torque limiter system in a paper feed roller and a separation roller based on an embodiment. FIG. 6 is a flowchart for explaining the operation of the image forming apparatus when transporting a sheet based on the first embodiment. FIG. 10 is a diagram illustrating detection by a leading edge detection unit according to the type of paper based on Embodiment 2. FIG. 10 is a flowchart for explaining the operation of the image forming apparatus when transporting a sheet based on Embodiment 2. FIG. 10 is a diagram illustrating a sheet thickness determination unit based on a modification of the second embodiment.

  Hereinafter, each embodiment will be described with reference to the drawings. In the following description, the same parts and components are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated. Each embodiment and each modified example described below may be selectively combined as appropriate.

  In the following embodiment, a case where a paper feeding device is mounted on an image forming apparatus will be described. Examples of the image forming apparatus include an MFP, a printer, a copier, and a facsimile. The paper feeding device may be mounted on a post-processing device having a post-processing unit that performs predetermined processing on the paper fed by the image reading device or the paper feeding device instead of the image forming device.

(Embodiment 1)
[Configuration of Image Forming Apparatus]
FIG. 1 is a cross-sectional view illustrating a configuration of an image forming apparatus based on the first embodiment.

  Referring to FIG. 1, an image forming apparatus (an example of a paper feeding device) according to the first embodiment includes an ADF 1, a toner image forming unit 210, a fixing device 220, a paper feeding cassette 230, a paper transport unit 240, and the like. , And scanner 250.

  The ADF 1 is provided in the upper part of the image forming apparatus. A detailed configuration of the ADF 1 will be described later.

  The toner image forming unit 210 combines four color images by a so-called tandem method, and forms a color image on a sheet. The toner image forming unit 210 includes a photoconductor 211 provided for each color of C (cyan), M (magenta), Y (yellow), and K (black), and a developing device 212 that forms a toner image on the photoconductor 211. The image forming apparatus includes an intermediate transfer belt 213 to which a toner image is transferred (primary transfer) from the photosensitive member 211, a transfer roller 214 for transferring an image from the intermediate transfer belt 213 to a sheet (secondary transfer) at the image forming position P1, and the like.

  The fixing device 220 includes a pressure roller 221 and a heating roller 222. The fixing device 220 conveys the sheet on which the toner image is formed with the pressure roller 221 and the heating roller 222, and heats and presses the sheet. As a result, the fixing device 220 melts the toner adhering to the paper and fixes it on the paper to form an image on the paper.

  The paper feed cassette 230 stores paper for forming an image. There may be a plurality of paper feed cassettes 230.

  The paper transport unit 240 includes a separation unit 241, a transport roller pair 242, a discharge roller pair 243, and the like. The separation unit 241 separates one sheet from a plurality of sheets stored in the sheet feeding cassette 230 and feeds the sheet to the transport path TR. The separation unit 241 includes a paper feed roller 241a and a separating roller 241b. The transport roller pair 242 transports the paper along the transport path TR. The discharge roller pair 243 discharges the sheet on which the image is formed to the discharge tray 261.

  The scanner 250 is disposed between the ADF 1 and the paper discharge tray 261. The scanner 250 includes an IR (Infrared) module 251 and the like. The IR module 251 includes a lamp 252 for irradiating the original with light and an image sensor 253 for receiving reflected light from the original. The IR module 251 reads an image of a document and acquires the image data.

FIG. 2 is a cross-sectional view showing a configuration of the ADF 1 based on the first embodiment.
Referring to FIG. 2, ADF 1 conveys a sheet (original) that is an object of image reading by scanner 250 to image reading position P0. The ADF 1 has a U-shaped transport path TR. The ADF 1 includes a liftable pick roller 10, a paper feed roller 11, a separating roller 12, registration rollers 13 and 14 (conveying roller pair), reading rollers 15 and 16, a discharge roller pair 17, and a paper feed tray. 31, a paper discharge tray 32, and a sensor SE. The paper feed roller 11 and the separating roller 12 function as a pair of loop forming rollers that form a predetermined amount of loop between the pair of transport rollers.

  The pick roller 10 rotates while pressing the upper surface of the paper stacked on the placement surface of the paper feed tray 31, and sends the uppermost paper to the downstream.

  The paper feed roller 11 and the separating roller 12 constitute a separation unit RA. The registration rollers 13 and 14 constitute a transport roller pair RB. The separation unit RA conveys the sheet upstream of the conveyance path TR with respect to the conveyance roller pair RB. At least one of the outer peripheral surfaces of the paper feed roller 11 and the separating roller 12 and the registration rollers 13 and 14 has a high coefficient of friction.

  The paper feed roller 11 and the separating roller 12 are opposed to each other across the transport path TR and are in contact with each other. Each of the paper feed roller 11 and the separating roller 12 is driven to rotate in the paper transport direction (forward rotation direction) to transport the paper. Each of the sheet feeding roller 11 and the separating roller 12 separates one sheet from a plurality of sheets stored in the sheet feeding tray 31, and rotates while being sandwiched, thereby conveying the separated sheet along the conveyance path TR. To do. The separating roller 12 is urged in a rotation direction (reverse direction) opposite to the paper transport direction, and applies a force in a direction opposite to the paper transport direction to the contacting paper. The rolling roller 12 has a torque limiter that acts so that driven rotation in the transport direction is possible when a predetermined amount of force is applied in the transport direction.

  The coefficient of friction between the surface of the paper feed roller 11 and the sheet is preferably higher than the coefficient of friction between the sheets. The friction coefficient between the surface of the roller 12 and the paper is preferably higher than the friction coefficient between the papers.

  The registration rollers 13 and 14 are opposed to each other across the transport path TR and are in contact with each other. Each of the registration rollers 13 and 14 is driven to rotate in the normal rotation direction to convey the paper. Each of the registration rollers 13 and 14 conveys the sheet in the conveyance direction along the conveyance path TR by rotating while sandwiching the sheet.

  The transport unit RB may be driven to rotate by rotating one of the registration rollers 13 and 14 and driving the other. The transport unit RB may be rotationally driven by rotationally driving both the registration rollers 13 and 14.

  The reading roller 15 is disposed between the transport roller pair RB and the image reading position P0. The reading roller 16 is disposed between the image reading position P0 and the discharge roller pair 17. Each of the reading rollers 15 and 16 conveys the sheet along the conveyance path TR by rotating while sandwiching the sheet with the wall portion 20. Each of the reading rollers 15 and 16 conveys the sheet so that the sheet passes through the image reading position P0 on each of the upstream side and the downstream side of the conveyance path TR of the image reading position P0.

  The discharge roller pair 17 is disposed on the most downstream side of the transport path TR. The discharge roller pair 17 discharges the paper to the paper discharge tray 32.

FIG. 3 is a block diagram illustrating a configuration of the image forming apparatus based on the first embodiment.
Referring to FIG. 3, the image forming apparatus includes a CPU (Central Processing Unit) 101, a ROM (Read Only Memory) 102, a RAM (Random Access Memory) 103, a network I / F 104, an image reading unit 105, and the like. , Operation panel 106, auxiliary storage device 107, image forming unit 108, first multiple sheet detection unit 109, conveyance control unit 110, paper feed motor 111, registration motor 112, conveyance motor 113, A second multi-sheet detecting unit 115 and a leading end detecting unit 116 for detecting the leading end of the sheet.

  CPU 101, ROM 102, RAM 103, network I / F 104, image reading unit 105, operation panel 106, auxiliary storage device 107, image forming unit 108, first multiple sheet detection unit 109, conveyance control unit 110, second Each of the plurality of sheet detection units is connected to each other by a bus or the like. The conveyance control unit 110 and each of the paper feed motor 111, the registration motor 112, and the conveyance motor 113 are connected to each other.

  The CPU 101 controls the operation of the entire image forming apparatus. The CPU 101 performs processing based on the control program.

  The ROM 102 stores a control program executed by the CPU 101 and various tables.

  A RAM 103 is a working memory for the CPU 101, and temporarily stores data relating to various jobs.

  The network I / F 104 transmits and receives various types of information to and from external devices through the network.

The image reading unit 105 reads an image of a document and creates image data thereof.
The operation panel 106 includes a display panel that displays various types of information and a detection unit that detects an input operation to the display panel.

The auxiliary storage device 107 stores various information such as image data.
The image forming unit 108 forms an image on a sheet.

  The first plurality of sheets detection unit 109 determines whether a sheet conveyed using a sensor is a plurality of sheets or a single sheet.

  The second multiple sheet detection unit 115 determines whether the sheet conveyed using the sensor is a plurality of sheets or a single sheet.

  The conveyance control unit 110 controls the conveyance of the paper by controlling on / off of each of the paper feed motor 111, the registration motor 112, and the conveyance motor 113. The paper feed motor 111 rotates the paper feed roller 11. The registration motor 112 rotates the registration roller 13. The transport motor 113 rotationally drives other rollers (such as the reading rollers 15 and 16 and the discharge roller pair 17).

  FIG. 4 is a diagram illustrating the configuration of the peripheral portions of the registration rollers 13 and 14, the paper feed roller 11, and the separating roller 12 based on the first embodiment.

  As shown in FIG. 4, a first plural-sheet detecting unit 109 is provided in the vicinity of the paper feed roller 11 and the separating roller 12. The first plurality of sheets detection unit 109 detects whether or not the sheets sandwiched between the nips of the sheet feeding roller 11 and the separating roller 12 are a plurality of sheets or one sheet. The first multi-sheet detection unit 109 can use an ultrasonic sensor as an example, but is not limited to this, and a sensor based on another method may be used.

  A second multiple sheet detector 115 is provided on the transport path TR between the registration roller pair and the paper feed roller 11. The sensor detects whether a plurality of sheets or one sheet is intruding on the transport path TR.

  FIG. 5 is a diagram illustrating a torque limiter method in the paper feed roller and the separating roller based on the embodiment.

  As shown in FIG. 5, in the torque limiter method, when only one sheet or document enters the nip of the separation unit, the torque limiter is loosened and the rolling roller follows the sheet or document and rotates normally.

  On the other hand, when two or more sheets or originals (multiple sheets) enter the nip of the separating portion, the slip torque of the torque limiter overcomes the frictional force between the sheets or between the originals, and the second sheet due to the slip torque of the torque limiter. Subsequent sheets or originals stay in the nip of the separation unit.

  Accordingly, since the braking force for only one sheet is larger than that for two or more sheets or originals, the slip amount increases.

  Therefore, in the first embodiment, when a plurality of sheets are detected, the rotation driving amount of the sheet feeding roller is adjusted. Specifically, the rotational drive amount of the paper feed roller 11 when a plurality of sheets are detected is adjusted to be smaller than the rotational drive amount of the paper feed roller 11 for only one sheet. As a result, fluctuations in the conveyance amount due to fluctuations in the conveyance speed can be suppressed.

  FIG. 6 is a flowchart for explaining the operation of the image forming apparatus when transporting a sheet based on the first embodiment.

  In this flowchart, it is assumed that the paper feed motor 111 is configured by a stepping motor, and the drive of the paper feed motor 111 is controlled based on a pulse signal indicating the drive amount (rotation amount) of the stepping motor.

  As shown in FIG. 6, the CPU 101 of the image forming apparatus determines whether or not a request for driving the paper feed roller 11 has been received (step S2). The CPU 101 repeats the process of step S2 until it is determined that a request for driving the paper feed roller 11 has been received.

  If it is determined in step S2 that the drive request for the paper feed roller 11 is accepted (YES in step S2), the CPU 101 rotates the paper feed roller 11 and the pick roller 10 by driving the paper feed motor 111 to rotate forward. (Step S4).

  Next, the CPU 101 determines whether or not the first plurality of sheets detection unit 109 has detected one sheet (step S6).

  In step S6, when the CPU 101 determines that the first plurality of sheets detection unit 109 has detected one sheet (YES in step S6), the CPU 101 sets the loop forming pulse PB1 (step S8).

  On the other hand, in step S6, when the CPU 101 determines that the first plurality of sheets detection unit 109 does not detect one sheet (when it is determined that a plurality of sheets are detected) (NO in step S6), a loop is formed. The pulse PB2 is set (step S24).

  Next, the CPU 101 determines whether or not the leading edge detection unit 116 has detected (ON) the leading edge of the sheet (step S10).

  In step S10, when the CPU 101 determines that the leading edge detection unit 116 has detected the leading edge of the sheet (YES in step S10), the CPU 101 determines whether or not the second multiple sheet detection unit 115 has detected one sheet. Judgment is made (step S12).

  In step S12, when the CPU 101 determines that the second plurality of sheets detection unit 115 has detected one sheet (YES in step S12), the CPU 101 starts (starts) the loop formation pulse count (step S14). .

  Next, the CPU 101 determines whether or not the count of loop forming pulses has been counted up (step S16).

  Next, when CPU 101 determines in step S16 that the loop forming pulse count has been incremented (YES in step S16), CPU 101 stops the paper feed motor (step S18).

  Next, the CPU 101 determines whether or not there is a registration roller driving request (step S36). The CPU 101 maintains the state of step S36 until there is a registration roller driving request.

  If the CPU 101 determines in step S36 that there is a registration roller driving request (YES in step S36), the CPU 101 drives the registration motor (step S38).

Then, the process ends (END).
On the other hand, when the CPU 101 determines in step S12 that the second multiple sheet detection unit 115 does not detect one sheet (NO in step S12), the CPU 101 executes error processing (step S26). Specifically, it is determined that double feeding has occurred, and the drive of the paper feed motor is stopped. Then, an error display notification process may be executed on the operation panel 106.

Then, the process ends (END).
Based on the detection result of the first multiple sheet detection unit 109, the value of the loop forming pulse PB is changed. Specifically, the loop formation pulse count differs between when a single sheet is detected and when a plurality of sheets are detected.

  Specifically, the count of the loop formation pulse PB2 when a plurality of sheets is detected is set smaller than the count of the loop formation pulse PB1.

  By this processing, the rotational driving amount of the paper feed roller 11 is adjusted, and it is possible to suppress the variation in the conveyance amount due to the variation in the conveyance speed.

  As a result of suppressing fluctuations in the transport amount of the paper, in an image forming apparatus equipped with a paper feeding device, the inclination of the front end of the paper is corrected without damaging the front end of the paper, and the reproducibility of the input image is improved. Can do. In an image reading apparatus equipped with a paper feeding device, it is possible to suppress the deterioration of the quality of a read image and improve the reproducibility of a document image.

  In this example, in order to suppress fluctuations in the sheet conveyance amount, the rotation driving amount of the sheet feeding roller 11 when a plurality of sheets are detected is the rotation driving amount of the sheet feeding roller 11 for only one sheet. The case of adjusting the amount to be smaller than the amount has been described, but in order to suppress fluctuations in the amount of paper transport, the rotational driving amount of the paper feed roller 11 for only one paper sheet is detected for a plurality of paper sheets. In this case, adjustment may be made so as to be larger than the rotational driving amount of the paper feed roller 11.

(Embodiment 2)
FIG. 7 is a diagram illustrating detection in the leading edge detection unit 116 according to the type of paper based on the second embodiment.

  FIG. 7A is a diagram for describing detection by the leading edge detection unit 116 when a cardboard is conveyed.

  FIG. 7B is a diagram illustrating detection by the leading edge detection unit 116 when thin paper is conveyed.

  The tip detection unit 116 includes a detection lever 300 movably provided around the rotation shaft 301 and a sensor that detects movement of the detection lever (not shown).

  The sensor detects that the leading edge of the paper has arrived by detecting that the detection lever moves from the initial position.

  As shown in the figure, there is a difference in the loop shape of the paper when the detection lever is moved between when the thick paper is transported and when the thin paper is transported. This is because the paper is different between thick paper and thin paper.

  Therefore, in order to make the loop shape the same regardless of the type of paper, the transport amount for transporting thick paper is greater than the transport amount for transporting thin paper with respect to the transport amount when the leading edge detection unit 116 detects the leading edge of the paper. Also need to be long. That is, the rotational driving amount of the paper feed roller 11 is adjusted so as to be larger than that of thin paper when thick paper is used.

  In the second embodiment, the paper type (thick paper or thin paper) is set in advance according to the operation of the operation panel 106. The CPU 101 determines the thickness of the sheet using setting information according to the operation of the operation panel 106.

  FIG. 8 is a flowchart for explaining the operation of the image forming apparatus when transporting a sheet based on the second embodiment.

  In this flowchart, it is assumed that the paper feed motor 111 is configured by a stepping motor, and the drive of the paper feed motor 111 is controlled based on a pulse signal indicating the drive amount (rotation amount) of the stepping motor.

  As shown in FIG. 8, it is different from the flowchart of FIG. 6 in that steps S7, S9, S23, and S25 are further added.

  Specifically, in step S6, if the CPU 101 determines that the first plurality of sheets detection unit 109 has detected one sheet (YES in step S6), the CPU 101 determines whether the paper type setting is thin paper. (Step S7).

  In step S7, when the CPU 101 determines that the paper type setting is thin paper (YES in step S7), the CPU 101 sets the loop forming pulse PB1 (step S8).

  On the other hand, if the CPU 101 determines in step S7 that the paper type setting is not thin paper (NO in step S7), the CPU 101 sets the loop forming pulse PB3 (step S9).

  In step S6, when the CPU 101 determines that the first plurality of sheets detection unit 109 does not detect one sheet (when it is determined that a plurality of sheets are detected) (NO in step S6), the paper type It is determined whether or not the setting is thin paper (step S23).

  In step S23, when the CPU 101 determines that the paper type setting is thin paper (YES in step S23), the CPU 101 sets the loop forming pulse PB2 (step S24).

  On the other hand, if the CPU 101 determines in step S23 that the paper type setting is not thin paper (NO in step S23), the CPU 101 sets the loop forming pulse PB4 (step S9).

The subsequent processing is the same as that described in the flowchart of FIG.
Based on the detection result of the first multiple sheet detection unit 109, the value of the loop forming pulse PB is changed. Specifically, the loop formation pulse count differs between when a single sheet is detected and when a plurality of sheets are detected.

  Specifically, the count of the loop formation pulse PB2 when a plurality of sheets is detected is set smaller than the count of the loop formation pulse PB1.

Furthermore, the value of the loop forming pulse PB is changed depending on whether the paper type is thick or thin.
Specifically, the count of the loop formation pulse PB3 when the thick paper is set is set larger than the count of the loop formation pulse PB1. Similarly, the count of the loop formation pulse PB4 when a thick sheet is set is set larger than the count of the loop formation pulse PB2.

  By this processing, the rotational driving amount of the paper feed roller 11 is adjusted according to the paper type setting, and it is possible to suppress the variation in the conveyance amount due to the variation in the conveyance speed.

  As a result of suppressing fluctuations in the transport amount of the paper, in an image forming apparatus equipped with a paper feeding device, the inclination of the front end of the paper is corrected without damaging the front end of the paper, and the reproducibility of the input image is improved. Can do. In an image reading apparatus equipped with a paper feeding device, it is possible to suppress the deterioration of the quality of a read image and improve the reproducibility of a document image.

(Modification)
In the second embodiment described above, the case has been described in which information that is set in advance according to the operation of the operation panel 106 is used as the information regarding the paper type.

In the modification, a method for automatically determining the paper type will be described.
FIG. 9 is a diagram illustrating a sheet thickness determination unit based on a modification of the second embodiment.

  As shown in FIG. 9, the sheet thickness determining unit is provided with a sheet thickness determining unit on the conveyance path TR between the registration roller pair and the sheet feeding roller 11. It is desirable to be provided on the upstream side of the tip detection unit 116.

  Specifically, the paper thickness determination unit includes a paper thickness detection roller 310 having a central shaft 311 provided to be movable up and down, a paper thickness detection lever 312 in contact with the paper thickness detection roller 310, and a paper thickness sensor. 313.

  The paper thickness detection roller 310 moves up and down according to the thickness of the conveyed paper. Specifically, in the case of thick paper, the central axis 311 of the paper thickness detection roller 310 rises more than in the case of thin paper. According to this operation, the rotation amount of the paper thickness detection lever 312 that is in contact with the paper thickness detection roller 310 changes. When the rotation amount of the paper thickness detection lever 312 increases, the light shielding amount of the paper thickness sensor 313 changes. Specifically, in the case of thick paper, the central axis 311 of the paper thickness detection roller 310 is raised. Accordingly, the amount of rotation of the paper thickness detection lever 312 becomes large. Accordingly, the light shielding amount of the paper thickness sensor 313 is larger for thick paper than for thin paper. As a result, the thickness of the conveyed paper can be detected.

  By providing the sheet thickness determining unit on the transport path TR, it is possible to automatically determine the sheet thickness and set the loop forming pulse corresponding to the sheet type described in FIG.

(Other)
The paper feeding device of the present invention conveys a sheet (original) to be imaged to the image reading position P0, and also conveys a sheet to be imaged to the image forming position P1. It may be. In this case, the operation of the paper supply roller 11 may be performed by the paper supply roller 241a, the operation of the separation roller 12 may be performed by the separation roller 241b, and the operation of the conveyance roller pair RB may be performed by the conveyance roller pair 242.

  In the above-described embodiment, the case where the loop forming roller is in contact with the winding portion has been described. However, the loop forming roller is arranged at a distance from the winding portion on the downstream side of the conveying path from the winding portion. May be. In this case, a roller different from the loop forming roller that contacts the winding portion may be provided.

  The separating section may be any one that applies a force in the direction opposite to the sheet conveyance direction to the sheet. In addition to the case where the winding portion is constituted by a roller as described above, the winding portion may be constituted by a stationary member (pad) having a high friction coefficient.

The above-described embodiments can be combined as appropriate.
The processing in the above-described embodiment may be performed by software or by using a hardware circuit. It is also possible to provide a program for executing the processing in the above-described embodiment, and record the program on a recording medium such as a CD-ROM, a flexible disk, a hard disk, a ROM, a RAM, or a memory card and provide it to the user. You may decide to do it. The program is executed by a computer such as a CPU. The program may be downloaded to the apparatus via a communication line such as the Internet.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  DESCRIPTION OF SYMBOLS 1 Paper feed roller, 12 Rolling roller, 13, 14 Registration roller, 15, 16 Reading roller, 17,243 Discharge roller pair, 20 Wall part, 31 Paper feed tray, 32,261 Paper discharge tray, 101 CPU, 102 ROM, 103 RAM, 105 image reading unit, 106 operation panel, 107 auxiliary storage device, 108 image forming unit, 109 first plural sheet detecting unit, 115 second plural sheet detecting unit, 110 transport control unit, 111 sheet feeding motor, 112 Registration Motor, 113 Conveyance Motor, 116 Tip Detection Unit, 210 Toner Image Forming Unit, 211 Photoconductor, 212 Developing Device, 213 Intermediate Transfer Belt, 214 Transfer Roller, 220 Fixing Device, 221 Pressure Roller, 222 Heating Roller, 230 Paper cassette, 240 Paper transport section 250 Scanner.

Claims (12)

A pair of transport rollers that can be rotationally driven to transport the paper;
A loop forming roller pair that is disposed upstream of the transport roller pair in the transport path and can be rotationally driven so that a predetermined amount of loop is formed between the transport roller pair;
A first plurality of sheet detectors arranged in the vicinity of the loop forming roller pair and detecting whether or not a plurality of sheets are present on the nip of the loop forming roller pair;
A controller for controlling the loop forming roller pair,
The loop forming roller pair is:
A paper feed roller that is rotationally driven to feed the paper in the transport direction;
A rolling roller having a torque limiter that is in pressure contact with the paper feed roller and acts to enable driven rotation in the transport direction when a predetermined amount of force is applied in the transport direction;
The control unit is a sheet feeding device that adjusts a rotational driving amount of the sheet feeding roller based on a detection result from the first plurality of sheets detection unit.   The control unit determines the rotation driving amount of the paper feed roller when the first plurality of sheets detection unit detects the plurality of sheets, and the first plurality of sheets detection unit determines the plurality of sheets. The sheet feeding device according to claim 1, wherein the sheet feeding device is adjusted so as to be smaller than a rotational driving amount of the sheet feeding roller when no toner is detected.   The sheet feeding device according to claim 1, wherein the control unit adjusts a rotational driving amount of the sheet feeding roller for each type of the sheet. A paper thickness discriminating section capable of discriminating the thickness of the conveyed paper;
4. The control unit according to claim 1, wherein the control unit adjusts a rotational driving amount of the paper feed roller based on a determination result of the paper thickness determination unit and a detection result of the first plural-sheet detection unit. The paper feeder described in the section. An input operation unit that can set the paper thickness according to the operation is further provided.
The sheet feeding device according to claim 4, wherein the sheet thickness determining unit determines a sheet thickness in accordance with an operation of the input operation unit. A paper leading edge detector for detecting the leading edge of the paper conveyed from the loop forming roller pair;
The sheet feeding device according to claim 4, wherein the sheet thickness determining unit is provided between the sheet leading edge detecting unit and the loop forming roller pair. A paper leading edge detector for detecting the leading edge of the paper conveyed from the loop forming roller pair;
The paper leading edge detector is
A movable member provided on the transport path and movable according to the delivery of the paper;
The sheet feeding device according to claim 1, further comprising a detection member that detects a state of the movable member.   The sheet feeding device according to any one of claims 1 to 7, further comprising a second plural-sheet detecting unit provided between the pair of conveying rollers and the pair of loop forming rollers.   The sheet feeding device according to claim 8, wherein the control unit stops the sheet feeding roller when the second plurality of sheets detection unit detects the plurality of sheets. A paper feeding device according to any one of claims 1 to 9,
A document reading device comprising: a document reading unit that reads an image on a sheet fed by the sheet feeding device. A paper feeding device according to any one of claims 1 to 9,
An image forming apparatus comprising: an image forming unit that forms an image on a sheet fed by the sheet feeding device. A paper feeding device according to any one of claims 1 to 9,
And a post-processing unit that performs predetermined processing on the paper fed by the paper feeding device.

Images