JP2016104659A - Sheet conveyance device, auto document feeder, and image formation apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sheet conveyance device which can achieve correct discrimination of paper kinds and shortening of paper intervals.SOLUTION: When a pickup roller (11A) draws a first sheet (SH1) out from a bundle (DC0), a light-emitting element (210) irradiates the sheet with light, and light reception elements (211, 212) detect the reflection light quantity/transmission light quantity from the sheet. When a discrimination part (231) discriminates the paper kind of the sheet on the basis of those, a paper kind information generation part (233) generates information indicating the paper kind. When a feeding roller (11B) moves a second sheet (SH2) forward with the second sheet overlapped on the first sheet (SH1), the light-emitting element (210) irradiates the two sheets with light, and the second light reception element (212) detects the light transmission quantity from the sheets. When an estimation part (232) estimates that the two sheets of the paper kind discriminated by the discrimination part are overlapped with each other on the basis of that, the paper kind information generation part (233) generates information indicating the paper kind.SELECTED DRAWING: Figure 7

Description

  The present invention relates to an apparatus for conveying sheets such as printing paper and originals from a bundle thereof.

In recent years, the conditions that can be set have been diversified along with the improvement of image forming techniques such as printing and copying, and the types of printing paper suitable for those conditions (hereinafter referred to as “paper types”) are also abundant. . For example, paper types suitable for photography include glossy film, photographic paper, and glossy paper, and paper types suitable for documents include matte paper, fine paper, and plain paper.
Along with such diversification of paper types, it is becoming common when one copy of an original to be copied or bound includes two or more paper types. In this case, it is not preferable for the image forming apparatus such as a copier or a printer to prevent the improvement in operability for the user to manually set the paper type of the printing paper according to the paper type of the document.

  In order to improve the operability of the image forming apparatus, it is desirable to use a technique that allows the conveying device to automatically determine the sheet type of the sheet. For example, in the technique disclosed in Patent Literature 1, the light reflectance of the printing paper is measured by the transport device, and the paper type is discriminated from the measured value. In the technique disclosed in Patent Document 2, an RF tag storing its own paper type is embedded in print paper in advance, and the printer is caused to read the RF tag in the paper feed cassette to determine the paper type.

JP 2003-137457 A JP 2006-110842 A

  In order for the image forming apparatus to copy or bind a document, it is desirable that the following conditions be satisfied in order for the transport device to automatically select the paper type of the printing paper according to the paper type of the document. First, an electromagnetic wave such as light or a sound wave is used to determine the paper type of the document. Thereby, it is possible to prevent the original from being damaged due to the paper type discrimination process. Next, the paper type is discriminated immediately after the document is fed to the scanner. Thereby, in addition to the processing for selecting the paper type of the printing paper, it is possible to quickly advance the condition setting for the subsequent processing such as the condition setting when the scanner captures the image of the document.

  However, meeting these conditions has the following disadvantages. First, in order to accurately discriminate paper types using electromagnetic waves or sound waves, it is necessary to accurately measure the reflectance or transmittance of the sheet with respect to those waves. In order to execute this accurate measurement immediately after feeding to the scanner, the sheet to be measured must be surely separated from other sheets immediately after feeding. As a result, it is difficult to shorten the document conveyance interval, that is, the sheet interval, below a certain limit. On the other hand, there are actually few cases where the paper type frequently changes in one copy. Therefore, it is expected that the case where the interval between the sheets cannot be shortened even though the same sheet type is continuous is more general. That is, satisfying the above conditions is disadvantageous in that it is difficult to increase the document conveyance speed and increase the productivity.

  An object of the present invention is to solve the above-described problems, and in particular, to provide a transport device capable of making accurate discrimination between paper types compatible with shortening between papers.

  A sheet conveying apparatus according to one aspect of the present invention includes an accommodating portion that accommodates a bundle of sheets, and first feeds the leading end of the first sheet toward the conveying path from the bundle, and then the leading end of the second sheet. The first sheet is fed out from the bundle in a state where it is overlapped with the first sheet, and then the first sheet is separated from the second sheet and sent to the conveying path, and a portion of the first sheet that does not overlap with the second sheet is predetermined. A determination unit that detects at least one of reflectance or transmittance with respect to the electromagnetic wave or the sound wave, and determines a paper type of the first sheet from the detected value; and a predetermined electromagnetic wave or the like from an overlapping portion of the first sheet and the second sheet An estimation unit that detects the transmittance with respect to the sound wave and estimates that the second sheet is the same paper type as the first sheet based on the detected value, and the paper type determined by the determination unit for the first sheet Indicate A paper type information generation unit that generates information indicating the paper type when the estimation unit estimates that the second sheet is the same paper type as the first sheet. ing.

  When the estimation unit estimates that the second sheet is the same paper type as the first sheet, the determination unit may not determine the paper type of the second sheet. On the other hand, when the estimation unit does not estimate that the second sheet is the same paper type as the first sheet, the determination is made after the conveyance unit separates the first sheet from the second sheet and sends it to the conveyance path. The unit detects at least one of the reflectance or transmittance of the tip of the second sheet with respect to a predetermined electromagnetic wave or sound wave, determines the paper type of the second sheet from the detected value, and the paper type information generation unit Information indicating the paper type may be generated.

The estimation unit compares the transmittance of the overlapping portion of the first sheet and the second sheet with the transmittance when two sheets of the same paper type as the first sheet are stacked, and between the transmittances of both. If the difference is less than or equal to the threshold value, the second sheet may be estimated to be the same paper type as the first sheet.
The discriminating unit detects the transmittance of the leading end of the first sheet with respect to a predetermined electromagnetic wave or sound wave and uses it to discriminate the paper type of the first sheet, and the estimating unit calculates the transmittance and thickness of the sheet with respect to the electromagnetic wave or sound wave. A storage unit that stores the relational expression between the first and second paper types, reads the relational expression for the paper type of the first sheet from the storage part, and substitutes the transmittance detected by the determination unit into the relational expression. The transmittance when two sheets of the same sheet type as the first sheet are stacked may be estimated by calculating the thickness of the sheet and substituting twice the thickness into the relational expression.

  The accommodating portion includes a lift portion that applies an upward force to the bundle, and the conveying portion is installed between the accommodating portion and the conveying path, and is inclined with respect to the conveying direction, and the inclination of the plate-like member A shelf-like member that includes a flat part that spreads horizontally from the upper end of the sheet and a wall part that rises near the entrance of the conveyance path, and can be moved up and down above the bundle, rotating while applying downward force to the top surface of the bundle The pickup roller that feeds the sheets from the bundle to the shelf-like member in order from the top, and the vicinity of the entrance of the conveyance path or downstream of the entrance, contact the upper surface of the sheet over the shelf-like member by the pickup roller The sheet feeding roller that separates the sheet from the bundle and feeds it to the conveyance path, and is installed at the boundary between the storage unit and the flat part of the shelf-like member, and reaches the boundary along the inclination of the plate-like member Climb By rotating in contact with the lower surface of the leading edge of the sheet, the driving force is applied to the feeding roller, the pickup roller, the paper feeding roller, and the feeding roller that advance the leading edge toward the wall of the shelf-like member. A power source and a control unit that controls a driving force of the power source, a downward force applied by the pickup roller to the bundle, and an upward force applied by the lift unit may be included. In this case, the tip of the second sheet is positioned below the upper end of the inclination of the plate-like member while the tip of the first sheet advances from the bundle to the wall of the shelf-like member under the control of the control unit, After the time when the leading edge of the first sheet gets over the wall, it may rise to the upper end of the inclination of the plate-like member and come into contact with the feed roller, and may remain stationary after the time when it contacts the wall.

An automatic document feeder according to one aspect of the present invention accommodates a bundle of documents as a bundle of sheets, separates the document from the bundle, and moves the document to an image reading device. The sheet conveying apparatus for conveying is provided.
An image forming apparatus according to one aspect of the present invention includes the above-described sheet conveying device that separates and feeds a sheet from a bundle of sheets, and an image forming unit that forms an image on the sheet fed by the sheet conveying device. Yes.

  As described above, the sheet conveying apparatus according to one aspect of the present invention generates information indicating the determined paper type for the first sheet, while the second sheet is the same paper type as the first sheet for the second sheet. When it is estimated that, the information indicating the paper type is generated. As a result, this transport device can achieve both the accurate discrimination of the paper type and the shortening between the papers.

1 is a perspective view illustrating an appearance of an image forming apparatus according to an embodiment of the present invention. It is sectional drawing along the straight line II-II of ADF and the scanner which are shown in FIG. FIG. 3 is an enlarged view of a paper feed unit of ADF surrounded by a broken line part in FIG. 2. FIG. 2 is a front view schematically showing an internal structure of the printer shown in FIG. 1. FIG. 2 is a block diagram illustrating a control system of the image forming apparatus illustrated in FIG. 1. (A) is a table | surface which shows the setting value of the main parameter in an image formation process for the paper classification of printing paper, (b) is a schematic diagram which shows the paper feed cassette with which the image forming apparatus shown in FIG. 1 was equipped. is there. (A)-(d) is a schematic diagram which shows in order the 1st-4th process of the paper supply process by the paper supply part shown in FIG. (A) is a table | surface which shows the reflectance and the transmittance | permeability per sheet for the paper classification of a sheet | seat, (b) is a graph which shows the relationship between the thickness of a plain paper, and the transmittance | permeability. (A) is a schematic diagram which shows the position of the sheet | seat of a 2 sheet | seat overlap in the case where the transmittance | permeability is detected in the 3rd process which (c) of FIG. 7 shows, (b) is (d) of FIG. FIG. 10 is a schematic diagram illustrating the position of the immediately preceding sheet when the sheet type of one sheet is determined in the fourth step shown in FIG. It is the first half of the flowchart of the paper feed process shown in FIG. It is the second half of the flowchart of the paper feed process shown in FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Appearance of image forming apparatus]
FIG. 1 is a perspective view showing an external appearance of an image forming apparatus according to an embodiment of the present invention. The image forming apparatus 100 is a multi-function peripheral (MFP), and includes a scanner 120 at the top of the casing and a printer 130 at the bottom. Using these, MFP 100 realizes image reading, copying, and printing functions.

  Referring to FIG. 1, an automatic document feeder (ADF) 110 is mounted on the upper surface of the casing of MFP 100 so as to be openable and closable. A scanner 120 is built in a housing portion directly below the ADF 110, and an operation panel 101 is embedded in the front surface thereof. A gap 102 is opened directly below the scanner 120, and a paper discharge port 131 is installed behind the gap 102. That is, the MFP 100 is an in-body discharge type, and this gap 102 is used as a discharge space. A printer 130 is built in the casing portion around the discharge space 102 and below, and a paper feed cassette 133 is attached to the bottom of the printer 130 so that it can be pulled out.

[ADF structure]
FIG. 2 is a cross-sectional view taken along line II-II between ADF 110 and scanner 120 shown in FIG. Referring to FIG. 2, the ADF 110 includes a paper feed port 111, a paper feed tray 112, a lift unit 113, a plurality of transport rollers 11A-11H, pressing members 114 and 115, a back scanner 116, a paper discharge port 117, and paper discharge. A tray 118 is included.

  The paper feed port 111 and the paper discharge port 117 are an entrance and an exit, respectively, of a document conveyance path provided inside the ADF 110. The paper feed tray 112 is installed on the upper surface portion of the ADF 110 facing the paper feed port 111, and is swingably connected to the casing of the ADF 110. On the paper feed tray 112, a document DC0 for feeding the ADF 110 is accommodated. The lift unit 113 is installed at a connection portion between the paper feed tray 112 and the housing of the ADF 110, and swings the paper feed tray 112 using a built-in motor (not shown in FIG. 2). As a result, the lift unit 113 raises the document DC0 to approach the paper feed port 111. The transport rollers 11A-11H are sequentially installed from the paper feed port 111 to the paper discharge port 117 along the document transport path. Each of the transport rollers 11A,..., 11G contacts the document moving on the transport path while rotating, and feeds the document to the next transport rollers 11B,. The last transport roller 11H is positioned at the paper discharge port 117, and discharges the document delivered from the previous transport roller 11G from the paper discharge port 117. A paper discharge tray 118 is installed below the paper feed tray 111, and a document DC2 discharged from the paper discharge port 117 is stacked thereon.

  The document conveyance path is exposed on the bottom surface of the ADF 110 and faces the top surface of the scanner 120, and passes directly below the back surface scanner 116 inside the ADF 110. While being transported along this path, the document passes through the vicinity of the scanner 120 and the back scanner 116 with the surfaces on the different sides facing each other. The first pressing member 114 is installed in a portion of the bottom surface of the ADF 110 where the document transport path is exposed, and the second pressing member 115 is installed so as to face the back scanner 116 with the document transport path in between. Yes. Each pressing member 114, 115 applies an appropriate force to the document passing over it, and keeps the distance between the document and the scanner 120 or the back scanner 116 appropriate. The back scanner 116 irradiates light on the surface of the document DC1 passing through the conveyance path directly below, reads an image from the light reflected by the surface, and converts it into an electrical signal. The back scanner 116 further transmits an electrical signal representing the read image to the scanner 120 to convert the electrical signal into digital image data.

−Structure of paper feed unit−
FIG. 3 is an enlarged view of the paper feeding unit of the ADF 110 surrounded by the broken line part 200 in FIG. Referring to FIG. 3, first, the paper feed unit 200 serves as a mechanism for sending a document from the paper feed tray 112 to the paper feed port 111, as a separation plate 201, a stop plate 202, a pickup roller 11 </ b> A, a paper feed roller 11 </ b> B, It includes a roller 12A and a rolling roller 12B.

  The separation plate 201 is a plate-like member installed between the paper feed port 111 and the paper feed tray 112, and is in the direction in which the document should be sent from the paper feed tray 112 to the paper feed port 111, that is, the “paper feed direction”. Is inclined. The stop plate 202 is a shelf-like member and is installed between the paper feed port 111 and the separation plate 201. The stop plate 202 includes a flat portion 221 that extends substantially horizontally from the upper end of the inclination of the separation plate 201, and a wall portion 222 that rises in the vicinity of the paper feed port 111.

  The pick-up roller 11A is the leading transport roller shown in FIG. 2, and is embedded in the upper surface of the paper feed port 111 in a region located above the bundle of documents DC0 stored in the paper feed tray 112, and is fed in a horizontal plane. It can rotate around an axis oriented perpendicular to the paper direction and can be raised and lowered in the vertical direction. The pickup roller 11A rotates while applying a downward force to the upper surface of the original bundle DC0, thereby feeding the originals SH1, SH2, SH3,...

  The paper feed roller 11B is the second transport roller shown in FIG. 2, and is embedded in a region on the upper surface of the paper feed port 111 above or downstream of the front end of the paper feed tray 112. , And can be rotated around an axis oriented perpendicular to the paper feeding direction. The paper feed roller 11B feeds the original document SH1 to the transport path by rotating the pickup roller 11A in contact with the upper surface of the original document SH1 fed from the bundle DC0.

  The delivery roller 12A is installed at the boundary between the separation plate 201 and the flat portion 221 of the stop plate 202, and is rotatable around an axis oriented perpendicular to the paper feeding direction in a horizontal plane. The feed roller 12A rotates while contacting the lower surface of the front end portion of the document SH2 pushed by the pickup roller 11A and climbing the inclination of the separation plate 201, thereby causing the front end portion to follow the flat portion 221 of the stop plate 202. And move forward toward the wall 222.

  The separating roller 12B is embedded in the lower surface of the sheet feeding port 111 at a position facing the sheet feeding roller 11B, and is rotatable around an axis oriented perpendicular to the sheet feeding direction in a horizontal plane. The separation roller 12B contacts the lower surface of the document SH1 fed out from the bundle DC0 by the pick-up roller 11A and rotates in the opposite direction to the paper feed roller 11B, so that the next document SH2 overlaps under the document SH1 and advances. If it does, the next document SH2 is prevented from moving forward.

  These elements 201, 202, 11A, 11B, 12A, and 12B constitute a document feeding mechanism. In this mechanism, first, the leading end of one original SH1 (hereinafter referred to as “first original”) is fed out from the original bundle DC0 and advanced to the wall 222 of the stop plate 202. Next, the front end of the first document SH1 is moved over the wall 222, and the bundle DC0 is placed with the front end of the next document SH2 (hereinafter referred to as “second document”) overlapped with the first document SH1. And is advanced to the wall 222 of the stop plate 202. Thereafter, the first document SH1 is separated from the second document SH2 and sent out to the conveyance path while the leading edge of the second document SH2 is kept on the stop plate 202. Thereafter, this mechanism repeats these operations.

The paper feeding unit 200 also includes a light emitting element 210, a first light receiving element 211, and a second light receiving element 212. These elements 210-212 are used to determine the paper type of the document.
The light emitting element 210 is, for example, a semiconductor laser or LED, and is embedded in a position facing the stop plate 202 on the upper surface of the paper feed port 111 and irradiates light such as infrared rays to the flat portion 221 of the stop plate 202. When the leading end of the document SH2 that has entered the area DTR above the flat portion 221 (hereinafter referred to as “discrimination area”) collides with the wall 222 and stops, a part of the irradiation light of the light emitting element 210 is It is reflected at its tip, and another part is transmitted through the tip.

  Both the first light receiving element 211 and the second light receiving element 212 are light quantity sensors such as photodiodes. The first light receiving element 211 is embedded in a position facing the stop plate 202 on the upper surface of the sheet feeding port 111, and detects the amount of light of the light emitting element 210 reflected by the leading ends of the documents SH1 and SH2 that have entered the discrimination region DTR. To do. The second light receiving element 212 is embedded in the bottom of the stop plate 202 and detects the amount of light emitted from the light emitting element 210 that has passed through the leading ends of the documents SH1 and SH2 that have entered the discrimination region DTR.

[Scanner structure]
Referring back to FIG. 2, the scanner 120 includes a contact glass 121, a platen glass 122, a slider 123, optical systems 124 and 125, a line sensor 126, and an image processing unit 127. Using these, the scanner 120 reads an image from a document transported inside the ADF 110 or a document placed on the platen glass 122.

  The contact glass 121 closes a slit opened on the upper surface of the scanner 120, and faces the portion of the document conveyance path exposed on the bottom surface of the ADF 110 directly above the contact glass 121. The contact glass 121 is in the form of an elongated plate, the surface of which is parallel to the surface of the document passing through the portion of the conveying path that faces and the longitudinal direction of which is perpendicular to that portion of the conveying path (in FIG. (Hereinafter, referred to as “main scanning direction”). The contact glass 121 is made of transparent glass or translucent resin.

The platen glass 122 closes an opening formed on the upper surface of the scanner 120 at a location different from the position of the contact glass 121. Since the platen glass 122 is exposed when the ADF 110 is opened, a document can be placed thereon. The platen glass 122 has a rectangular plate shape and is made of transparent glass or translucent resin.
The slider 123 is installed inside the scanner 120 and can reciprocate along the ceiling surface from directly below the contact glass 121 to the end of the platen glass 122 opposite to the contact glass 121. . The slider 123 includes a light source 128 and a mirror 129. The light source 128 is a linear light source parallel to the main scanning direction, and irradiates light from the upper surface of the slider 123 through the contact glass 121 or the platen glass 122 to the surface of the document placed thereon. The mirror 129 reflects the light reflected from the surface of the original and incident from above the slider 123 toward the optical systems 124 and 125. The optical system includes a pair of mirrors 124 and a lens 125, and uses them to focus the light sent from the slider 123. The pair of mirrors 124 can reciprocate in the same direction as the slider 123 at half speed in the same direction. Thereby, even when the slider 123 irradiates any part of the document placed on the platen glass 122, the optical path length of the reflected light from the document is kept constant.

  The line sensor 126 includes an array of solid-state imaging devices such as charge coupled devices (CCDs) juxtaposed in parallel with the main scanning direction, detects the light focused by the optical systems 124 and 125, and converts it into an electrical signal. The image processing unit 127 processes electrical signals output from the back scanner 116 and the line sensor 126, converts them into digital image data, and outputs the digital image data to the printer 130 or an external electronic device. Since each of the back scanner 116 and the line sensor 126 reads images on different surfaces of the same document DC1, the image data output from the image processing unit 127 represents both front and back images of the document DC1.

[Printer structure]
FIG. 4 is a front view schematically showing the structure of the built-in part of the printer 130 in the MFP 100. In FIG. 4, the elements of the printer 130 are depicted as if the front surface of the housing is seen through. The printer 130 is an electrophotographic color printer, and includes a feeding unit 10, an image forming unit 20, a fixing unit 30, and a paper discharge unit 40.

  The feeding unit 10 feeds printing sheets SHT (hereinafter referred to as “sheets”) from the sheet feeding cassette 11 to the image forming unit 20 one by one using the roller groups 12, 13, and 14. The material of the sheet SHT that can be stored in the paper feed cassette 11 is paper or resin, the paper type is plain paper, high-quality paper, color paper, or coated paper (ML, GL, GO), and the size is A3. , A4, A5, or B4.

  The image forming unit 20 forms a toner image on the sheet SH2 sent from the feeding unit 10. Specifically, each of the four image forming units 21Y, 21M, 21C, and 21K first uses the laser light from the exposure unit 26 to base the surface of the photosensitive drums 25Y, 25M, 25C, and 25K on the basis of image data. Then, an electrostatic latent image is formed on the surface. Each image forming unit 21Y,... Then develops the electrostatic latent image with yellow (Y), magenta (M), cyan (C), and black (K) toners. The obtained four-color toner images are formed on the surface of the intermediate transfer belt 23 in order from the surface of the photosensitive drums 25Y,... By the electric field between the primary transfer rollers 22Y, 22M, 22C, 22K and the photosensitive drums 25Y,. Transferred to the same position above. Thus, one color toner image is formed at that position. This color toner image is further transferred onto the surface of the sheet SH2 fed from the feeding section 10 to the nip between the intermediate transfer belt 23 and the secondary transfer roller 24 by the electric field between the intermediate transfer belt 23 and the secondary transfer roller 24. Thereafter, when a separation voltage is applied to the sheet SH2, the sheet SH2 is peeled off from the secondary transfer roller 24 and sent to the fixing unit 30.

  The fixing unit 30 heat-fixes the toner image on the sheet SH2 sent out from the image forming unit 20. Specifically, when the sheet SH2 is passed through the nip between the fixing roller 31 and the pressure roller 32, the fixing roller 31 applies heat of a built-in heater to the surface of the sheet SH2, and the pressure roller No. 32 applies pressure to the heated portion of the sheet SH <b> 2 and presses it against the fixing roller 31. The toner image is fixed on the surface of the sheet SH <b> 2 by the heat from the fixing roller 31 and the pressure from the pressure roller 32.

The paper discharge unit 40 discharges the sheet on which the toner image is fixed to the paper discharge space 130. Specifically, the sheet SH2 conveyed from the upper part of the fixing unit 30 along the guide plate 41 to the paper discharge port 42 is rotated from the paper discharge port 42 to the paper discharge space 130 on the side thereof while the paper discharge roller 43 rotates. Send to the bottom.
[Electronic control system of image forming apparatus]
FIG. 5 is a block diagram showing the configuration of the electronic control system of MFP 100. Referring to FIG. 5, in addition to the ADF 110, the scanner 120, and the printer 130, an operation unit 50 and a main control unit 60 are connected to each other through a bus 90 so as to communicate with each other.

-Operation part-
The operation unit 50 receives a print job request and image data to be printed through a user operation or communication with an external electronic device, and transmits them to the main control unit 60. Referring to FIG. 3, the operation unit 50 includes an operation panel 101 and an external interface (I / F) 52. As illustrated in FIG. 1A, the operation panel 101 includes a push button, a touch panel, and a display. The operation panel 101 displays a GUI screen such as an operation screen and an input screen for various parameters on a display. The operation panel 101 also identifies the position of the push button or touch panel operated by the user, and transmits information related to the identification to the main control unit 60 as operation information. The external I / F 52 includes a memory interface such as a USB port or a memory card slot, or a network interface connected to an external network by wire or wireless. Through these, the external I / F 52 directly captures image data to be printed from an external storage device such as a USB memory or a hard disk drive (HDD), or communicates with other electronic devices connected to the network for printing. The target image data is received from those electronic devices. The external I / F 52 also writes the image data of the document processed by the image processing unit 127 of the scanner 120 to an external storage device or transmits it to other electronic devices on the network.

−Main control unit−
Main controller 60 is an electronic circuit mounted on a single board installed inside MFP 100. Referring to FIG. 3, the main control unit 60 includes a CPU 61, a RAM 62, and a ROM 63. The CPU 61 controls the other elements 50, 110, 120, and 130 according to the firmware. The RAM 62 provides a work area for the CPU 61 to execute the firmware to the CPU 61 and stores image data to be printed received by the operation unit 50. The ROM 63 includes a non-writable semiconductor memory device and a rewritable semiconductor memory device such as an EEPROM or an HDD. The former stores firmware, and the latter provides the CPU 61 with a storage area for environment variables and the like.

  As the CPU 61 executes various types of firmware, the main control unit 60 controls the other elements 50 based on operation information from the operation unit 50. Specifically, the main control unit 60 displays an operation screen on the operation unit 50 to accept an operation by the user. In response to this operation, the main control unit 60 determines an operation mode such as an operation mode, a standby mode, or a sleep mode, notifies the operation mode to the other elements 50,. Causes each element to execute the process.

  The main control unit 60 also receives information about the original from the paper feeding unit 200 of the ADF 110. This information indicates the size, orientation (separately between portrait and landscape), and the paper type of the document. Based on this information, the main control unit 60 designates an imaging condition to be set when the image of the original is captured in the scanner 120, and a paper feed to be selected when the image of the original is printed in the printer 130. Specify printing conditions such as cassette and parameter values to be set.

  FIG. 6A is a table showing setting values of main parameters in the image forming process for the sheet type of the sheet. This table is stored in advance in the ROM 63, for example. Referring to this table, the optimum values of the fixing temperature, the transfer current, and the separation voltage differ depending on the sheet type of the sheet. “Fixing temperature” represents the value of the surface temperature that should be maintained by the fixing roller 31 while the sheet SH2 is passed through the nip between the fixing roller 31 and the pressure roller 32. “Transfer current” represents the amount of current flowing between the sheets 23 and 24 through the sheet SH2 while the sheet SH2 is passed through the nip between the intermediate transfer belt 23 and the secondary transfer roller 24. The “separation voltage” is a voltage value applied to the sheet SH2 so that the sheet SH2 that has passed through the nip between the intermediate transfer belt 23 and the secondary transfer roller 24 is peeled off from the secondary transfer roller 24. Represent.

  FIG. 6B is a schematic diagram showing the four-stage paper feed cassettes CS1-CS4 provided in the MDF 100, and a table showing the paper types accommodated in each. When causing the MDF 100 to change the sheet type according to the paper type of the document, different paper types are stored in advance in different paper feed cassettes. For example, plain paper is stored in the uppermost cassette CS1, coated paper is stored in the second cassette CS2, color paper is stored in the third cassette CS3, and the lower cassette CS4 is stored in the lower cassette CS4. Contains high-quality paper. The correspondence table indicates which paper type is stored in which paper feed cassette, and is stored in the ROM 63, for example.

  When the operation unit 50 receives a copy job using, for example, the ADF 110 from the user, the main control unit 60 first causes the ADF 110 to transfer the image data of the document to the RAM 62. Next, the main control unit 60 designates parameter values to be set for each element based on the size, orientation, and paper type of the document indicated by the information from the ADF 110. Specifically, the feeding unit 10 designates one of the sheet feeding cassettes CS1 to CS4 that accommodates a sheet to be fed and the timing of feeding from the cassette, and the image forming unit 20 specifies a document. 6 is read out and specified from the table of FIG. 6A, the transfer current and the separation voltage corresponding to the paper type of the original are specified, and the fixing unit 30 is designated from the table of FIG. 6A. Read and specify the fixing temperature corresponding to the paper type of the document.

-ADF control system-
Referring back to FIG. 5, the ADF 110 includes a transport unit 300 in addition to the paper feed unit 200. The transport unit 300 is a functional unit that mainly controls the rotation of the transport rollers other than those included in the paper feed unit 200 among the transport rollers 11C-11H. The control system includes a drive unit 301 and a monitoring unit 302. The drive unit 301 controls a motor (not shown in FIG. 2) that applies a driving force to each of the transport rollers 11C,. The monitoring unit 302 monitors the document DC1 being conveyed through sensors (not shown in FIG. 2) installed at various points on the conveyance path.

The control system of the paper feed unit 200 includes a determination unit 231, an estimation unit 232, a paper type information generation unit 233, and a control unit 234. These functional units 231 to 234 are realized by executing firmware by a control circuit mounted on a single board built in the ADF 110.
When the operation unit 50 detects pressing of the start button among the push buttons on the operation panel 101, the determination unit 231 causes the light emitting element 210 to irradiate light accordingly and causes the second light receiving element 212 to detect the light. . It is determined from the amount of light detected at this time whether or not a document is stored in the paper feed tray 112.

  When the document feeding mechanism 201,..., 12B shown in FIG. 3 feeds one document from the sheet feed tray 112 to the sheet feed port 111, the determination unit 231 also determines that the document is a target of the sheet type. The reflectance and transmittance of the original with respect to the light from the light emitting element 210 are detected. Specifically, the determination unit 231 causes the light emitting element 210 to emit light to the determination region DTR in accordance with the timing when the leading edge of the first document SH1 enters the determination region DTR. The determination unit 231 further causes the first light receiving element 211 to detect the amount of light reflected by the determination region DTR, and causes the second light receiving element 212 to detect the amount of light transmitted through the determination region DTR. The determination unit 231 calculates the reflectance and transmittance of the first document SH1 from the detection result at this time, and determines the paper type of the first document SH1 based on these values.

  When the feeding mechanism 201,... Causes the leading edge of the second document SH2 to reach the determination area DTR with the first document SH1 overlapped with the first document SH1, the feeding mechanism 201,. The transmittance of the light emitting element 210 with respect to the overlapping portion of SH2 is detected. Specifically, the estimation unit 232 causes the light emitting element 210 to irradiate the determination region DTR with light in accordance with the time when the overlapping portion reaches the determination region DTR. The estimation unit 232 further causes the second light receiving element 212 to detect the amount of light transmitted through the discrimination region DTR. From the detection result, “two discs of the same paper type as the disc type of the manuscript discriminated by the discrimination unit 231 are determined in the discrimination region DTR”. It is estimated that they are overlapping.

  The paper type information generation unit 233 generates information indicating the paper type of the document according to the determination operation by the determination unit 231 or the estimation operation by the estimation unit 232, transmits the information to the main control unit 60, and sends the information to the determination unit 231. Next, specify the original for which the paper type is to be identified. Specifically, the paper type information generation unit 233 generates information indicating the paper type determined by the determination unit 231 for the first original SH1, and the second original SH2 is the first original SH1 for the second original SH2. When the estimation unit 232 estimates that the paper type is the same, the information indicating the paper type is generated. On the other hand, if the estimation unit 232 does not estimate that the second document SH2 is the same paper type as the first document SH1, the paper type information generation unit 233 sets the second document SH2 as the paper type for the determination unit 231. Specify as the target of discrimination.

  First, when the operation unit 50 detects that the start button of the operation panel 101 is pressed, the control unit 234 causes the determination unit 231 to detect the light amount of the light emitting element 210 in response to the second light receiving element 212 and supplies the light from the light amount. It is determined whether or not a document is stored in the paper tray 112. When it is determined that a document is stored in the paper feed tray 112, the control unit 234 starts a paper feed process for the document. In this process, the control unit 234 particularly has a motor (not shown in FIG. 3) that applies driving force to the four rollers 11A, 11B, 12A, and 12B included in the document feed mechanism, and a lift unit shown in FIG. 113 built-in motor is controlled. As a result, the control unit 234 adjusts the driving force of those motors, the downward force that the pickup roller 11A applies to the document DC0, and the upward force that the lift unit 113 applies to the document DC0 through the paper feed tray 112.

[Operation of feeding mechanism]
FIGS. 7A to 7D are schematic diagrams sequentially showing the first to fourth steps of the paper feed process by the paper feed unit 200 of the ADF 110. In this paper feed process, the originals are sent out one by one from the paper feed tray 112 to the paper feed port 111 by the operation of the feed mechanisms 201,.
-First step-
Referring to FIG. 7A, in the first step, the control unit 234 lowers the pickup roller 11A and presses the pickup roller 11A against the document bundle DC0, thereby increasing the downward force FC1 applied to the document bundle DC0 from the pickup roller 11A. . As a result, the frictional force associated with the rotation of the pickup roller 11A increases, so that the leading edge of the first document SH1 positioned at the top of the bundle of documents DC0 advances from the bundle DC0 in the paper feeding direction. The tip portion further contacts the feed roller 12A and is fed along the flat portion 221 of the stop plate 202 by the frictional force accompanying the rotation. On the other hand, the downward force FC1 from the pickup roller 11A prevents the second and subsequent originals SH2 and SH3 from rising, and in particular, the second original SH2 is at a position lower than the upper end of the separation plate 201 by a predetermined threshold THR or more. Be stagnated.

-Second step-
Referring to FIG. 7B, in the second step, the control unit 234 weakens the downward force FC2 applied to the bundle of documents DC0 from the pickup roller 11A. The second and subsequent originals SH2 and SH3 are raised by the force. As a result, the leading edge of the second document SH2 rises along the inclination of the separation plate 201 and its lower surface comes into contact with the feed roller 12A. Advance. However, since the upward movement of the document SH3 after the third sheet is blocked by the downward force FC2 from the pickup roller 11A, these documents SH3 remain at a position lower than the upper end of the separation plate 201 by a predetermined threshold THR or more.

-Third step-
Referring to FIG. 7C, the leading edge of the second document SH2 enters the flat portion 221 of the stop plate 202, and then reaches the determination area DTR while overlapping with the first document SH1. The third step is started in accordance with the arrival time. In this step, the control unit 234 again increases the downward force FC3 applied to the bundle of documents DC0 from the pickup roller 11A and stops (or reverses) the rotation of the feed roller 12A. As a result, the first document SH1 continues to advance in the paper feeding direction, while the leading end of the second document SH2 stops in a state where it collides with the wall 222 of the stop plate 202. On the other hand, the third and subsequent originals SH3 remain stagnant at a position lower than the upper end of the separation plate 201 by a predetermined threshold THR or more.

-Fourth step-
Referring to FIG. 7D, in the fourth step, similarly to the third step, the control unit 234 continues to convey the first document SH1 with the pickup roller 11A and keeps the feed roller 12A stationary (or reverse). Keep on). As a result, the leading edge of the second document SH2 is maintained on the stop plate 202, while the first document SH1 is separated from the second document SH2 and sent out to the document transport path. At this time, since the pickup roller 11A is in direct contact with the second document SH2, the control unit 234 increases the downward force FC1 applied to the bundle of documents DC0 from the pickup roller 11A as well as the first step, and at the same time the delivery roller 12A. Rotate again (or rotate forward). As a result, the leading end portion of the second document SH2 starts to advance again toward the wall portion 222 of the stop plate 202 and enters the determination region DTR.

Thereafter, the sending mechanisms 201,..., 12B repeat the operations from the second step to the fourth step until all the originals are sent to the paper feed port 111.
[Draft processing of original paper type]
With further reference to FIG. 7, in the first and fourth steps of the paper feed process, the discrimination unit 231 discriminates the paper type of the document that is the paper type discrimination target, and the paper type information generation unit 233 Information about the paper type is generated and transmitted to the main control unit 60. In the third step, when the estimation unit 232 estimates that “two documents of the same paper type as the preceding document overlap in the discrimination region DTR”, the paper type information generation unit 233 displays information on the paper type. When it is generated and transmitted to the main control unit 60 and is not estimated, the paper type information generation unit 233 designates the next document as a paper type discrimination target to the discrimination unit 231.

-Role of discriminator-
The determination unit 231 monitors a flag DTD set in the RAM 62, for example. This flag DTD indicates whether or not there is a paper type discriminating object by the discriminating unit 231 if there is a manuscript whose leading end is located in the discrimination area DTR at the present time. Specifically, for example, when the value of the flag DTD is “1”, the document is a determination target, and when it is “0”, the document is not a determination target. When the value of the flag DTD is “1”, the determination unit 231 causes the light emitting element 210 to irradiate the determination region DTR with light, and causes the first light receiving element 211 to detect the amount of light reflected by the determination region DTR. The second light receiving element 212 is made to detect the amount of light transmitted through the region DTR.

  Still referring to FIG. 7A, in the first step, the leading edge of the first document SH1 enters the flat portion 221 of the stop plate 202 and reaches the determination region DTR. Prior to this arrival, the discrimination unit 231 refers to the flag DTD, and when the value is “1”, the discrimination region DTR is irradiated with light in accordance with the timing when the leading edge of the first document SH1 reaches the discrimination region DTR. Then, the reflected light amount / transmitted light amount from the region DTR is detected.

  Further referring to FIG. 7 (d), in the fourth step, the first document SH1 is separated from the second document SH2 and sent out to the transport path, and the leading edge of the second document SH2 is again in the discrimination region DTR. To reach. Similar to the first step, prior to this arrival, the determination unit 231 refers to the flag DTD, and if the value is “1”, the determination is made in accordance with the timing when the leading edge of the second document SH2 reaches the determination region DTR. The region DTR is irradiated with light, and the reflected light amount / transmitted light amount from the region DTR is detected. On the other hand, if the value of the flag DTD is “0”, the determination unit 231 skips the detection of the reflected light amount / transmitted light amount from the second document SH2.

When the reflected light amount / transmitted light amount is detected from the original that is the object of paper type discrimination, the discriminating unit 231 further calculates the reflectance / transmittance of the original by dividing each by the amount of light emitted from the light emitting element 210, and calculates each of the calculations. The value is collated with the value indicated in the paper type table stored in the ROM 63, for example.
FIG. 8A shows an example of the paper type table. This table shows the reflectance and transmittance per sheet for each paper type of the document. The discriminating unit 231 discriminates the paper type of the document by collating the combination of calculated values of reflectance / transmittance with the combination of values shown in this table. For example, when the reflectance is 0 to 10%, if the transmittance is 30 to 40%, the paper type is determined to be fine paper, and if it is 40 to 50%, it is determined to be coated paper ML. If it is 60 to 80%, it is determined that it is plain paper. On the other hand, if the transmittance is 0 to 30%, the determination unit 231 determines that “the light detected by the second light receiving element 212 is transmitted through the print area of the document”, and if it is 80 to 100%, It is determined that the light deviates from the original and is not transmitted ”or“ the original is not stored in the paper feed tray 112 ”. Similarly, when the reflectance is another value, the paper type is determined based on the combination of the reflectance and the transmittance.

-Role of the estimation unit-
When the discriminating unit 231 discriminates the paper types of the preceding originals (first originals) SH1 and SH2 in the first and fourth steps, the estimating unit 232 determines the paper thickness from the transmittance of the first original detected at that time. And the transmittance of the paper thickness twice as large as the calculated value is estimated.
At this time, a certain relational expression based on the paper type of the first document is used for the calculation of the paper thickness and the estimation of the transmittance. This relational expression represents a relation established between the paper thickness and the light transmittance of the light emitting element 210 in the paper type, and is determined in advance by an experiment. For example, the ROM 63 stores relational expressions relating to various paper types.

  FIG. 8B is a graph showing the relational expression for plain paper. The measurement point SMP shown in this graph indicates a value when the transmittance of plain papers of various thicknesses or their bundles is actually measured. The straight line LNG shown in this graph represents the following relational expression between the paper thickness and the transmittance estimated from the measurement points SMP by the least square method: (transmittance [%]) = − 0.193 × (Paper thickness [μm]) +78.406. The slope “−0.193” and the intercept “78.406” of the straight line LNG are stored in the ROM 63 or the like as parameters defining this relational expression.

  Assume that the determination unit 231 calculates the transmittance TR1 of the first document as, for example, “61%” and determines the paper type of the document as “plain paper”. First, the estimation unit 232 reads parameters that define a relational expression relating to plain paper, that is, the slope “−0.193” and the intercept “78.406” of the straight line LNG shown in FIG. Next, using this relational expression, the estimation unit 232 obtains the paper thickness TH1 = 90 μm from the transmittance TR1 = 61% of the first document. The estimation unit 232 subsequently substitutes twice the paper thickness TH1 for the same relational expression TH2 = TH1 × 2 = 180 μm, and the obtained transmittance TR2 = 44% is obtained for a document of the same paper type as the first document. Estimated as the transmittance when the sheets overlap.

  The estimation unit 232 discriminates the leading end portion of the next original (second original) SH2 while overlapping with the previous original (first original) SH1, as shown in FIG. Each time the time to reach the region DTR arrives, the discrimination region DTR is irradiated with light to detect the amount of light transmitted from the region DTR. That is, unlike the determination unit 231, the estimation unit 232 detects the amount of transmitted light at the overlapping portion with the first document for all documents that can be the second document. The estimation unit 232 further divides this transmitted light amount by the irradiated light amount of the light emitting element 210 to calculate the transmittance of the two originals positioned in the discrimination region DTR.

The estimation unit 232 collates the transmittance value thus calculated with the value estimated as described above. As a result, when the error between the two values falls within the allowable range, the estimation unit 232 estimates that “the second document is the same paper type as the first document”.
-Role of paper type information generator-
In the first and fourth steps, the paper type information generation unit 233 generates information indicating the paper type of the first originals SH1 and SH2 determined by the determination unit 231 and transmits the information to the main control unit 60. On the other hand, in the third step, when the estimation unit 232 estimates that “the second original SH2 is the same paper type as the first original SH1”, information indicating the paper type is generated and transmitted to the main control unit 60. . In this case, the second original SH2 is not designated as the paper type discrimination target for the discrimination unit 231. That is, the flag DTD set in the RAM 62 is set to a value “0” indicating that the second document SH2 is not a discrimination target. Conversely, when the estimation unit 232 does not estimate that “the second document SH2 is the same paper type as the first document SH1,” the paper type information generation unit 233 displays information indicating the paper type of the second document SH2. In addition, the second original SH2 is designated as a paper type discrimination target for the discrimination unit 231. That is, the flag DTD is set to a value “1” indicating that the second document SH2 is a determination target.

-Role of control unit-
In the first step, the control unit 234 first determines the leading edge of the original document SH1 from the first time point when the pickup roller 11A contacts the first original document SH1 based on the conveyance speed of the original document by the pickup roller 11A and the delivery roller 12A. Predict the time to the second time point to reach the region DTR. Next, the control unit 234 measures the elapsed time from the first time point, and notifies the determination unit 231 that it is the light irradiation time for the determination region DTR when the measured value reaches the predicted value.

  In the second and third steps, the control unit 234 first reduces the downward force FC2 applied to the bundle of documents DC0 from the pickup roller 11A based on the conveyance speed of the documents by the pickup roller 11A and the delivery roller 12A. To the fourth time point when the leading edge of the second document SH2 reaches the determination area DTR while being overlapped with the first document SH1. Next, the control unit 234 measures the elapsed time from the third time point, and when the measured value reaches the predicted value, the estimation unit 232 irradiates the discrimination region DTR with light, and the pickup roller 11A has The downward force FC3 applied to the original bundle DC0 is increased again, and the rotation of the feed roller 12A is stopped (or reversed).

  In the fourth step, the control unit 234 first separates the first document SH1 from the second document SH2 from the fourth time point based on the document conveyance speed by the pickup roller 11A and the paper feed roller 11B, and the conveyance path. Accordingly, the time until the fifth time point at which the pickup roller 11A is in direct contact with the second document SH2 is predicted. Next, the control unit 234 measures the elapsed time from the fourth time point, and when the measured value reaches the predicted value, the downward force FC1 applied to the bundle of documents DC0 is applied to the pickup roller 11A in the same manner as in the first step. The feed roller 12A is rotated again (or rotated forward).

  Subsequently, the control unit 234 continues from the fifth time point to the sixth time point when the leading edge of the second document SH2 enters the determination region DTR again based on the document transport speed by the pickup roller 11A and the delivery roller 11B. Predict the time of. Next, the control unit 234 measures the elapsed time from the fifth time point, and notifies the determination unit 231 that it is the light irradiation time for the determination region DTR when the measured value reaches the predicted value.

[Advantages of the embodiment]
FIG. 9A is a schematic diagram showing the positions of the two-sheet originals SH1 and SH2 when the transmittance is detected in the third step, and FIG. 9B is the next original SH2 in the fourth step. FIG. 6 is a schematic diagram showing a position of a document SH1 immediately before the paper type is determined.
Referring to FIG. 9A, in the third step, the light of the light emitting element 210 is irradiated on the overlapping portion of the two originals SH1 and SH2 in the discrimination region DTR, and the amount of light transmitted through the overlapping portion is the first. Detected by two light receiving elements 212. At this time, the leading edge of the first document SH1 is advanced in the paper feeding direction by a distance ΔS1 from the leading edge of the second document SH2. This distance ΔS1 is the distance that the leading edge of the first document SH1 is advanced from the leading edge of the second document SH2 in the first step shown in FIG. 7A, that is, the wall 222 of the stop plate 202 from the top edge of the separation plate 201. Is equal to or greater than the distance in the paper feeding direction. Although the distance ΔS1 is short, it may be a value that allows the determination unit 231 to detect the reflected light amount / transmitted light amount from the original document SH1 without being obstructed by the second original document SH2 in the first or fourth step. It can be set to about mm to several tens of mm.

  Referring to FIG. 9B, in order for the determination unit 231 to accurately detect the reflected light amount / transmitted light amount from the second document SH2 in the fourth step, the first document SH1 is completely removed from the second document SH2. Must be separated. That is, at the time when the light emitting element 210 irradiates the leading edge of the second document SH2, the rear end of the first document SH1 has to advance slightly in the paper feeding direction from the leading edge of the second document SH2. . Therefore, the leading edge of the first document SH1 must be advanced by a distance ΔS2 or more equal to the size of the first document SH1 in the paper feeding direction than the leading edge of the second document SH2.

  As a specific example, the conveyance speed of the original by the paper supply unit 200 is 36 ppm = 126 mm / second, the size of the first original SH1 is A4, and its posture is horizontal (the short side is parallel to the paper feeding direction). Assuming that Furthermore, the distance ΔS1 shown in FIG. 9A is 10 mm, and the time required for detecting the amount of reflected light by the determination unit 231 and the estimation unit 232 is the same value α = 2 to 3 milliseconds.

  In this case, the time T1 from the time when the determination unit 231 detects the reflected light amount / the transmitted light amount from the first document SH1 to the time point when the estimation unit 232 detects the transmitted light amount from the overlapping portion of the two documents SH1 and SH2. Is equal to or longer than the time required to move the first document SH1 forward by the distance ΔS1 = 10 mm, that is, 10 mm / 126 mm / sec = 80 ms, and the detection times α of the determination unit 231 and the estimation unit 232. : T1 = 2α + 80 msec.

  On the other hand, the time T2 from the time when the determination unit 231 detects the reflected light amount / transmitted light amount from the first document SH1 to the time point when the determination unit 231 can detect the reflected light amount / transmitted light amount from the second document SH2 is the first time T2. 2 times the detection time α of the determination unit 231 is added to the time required to advance one document SH1 by a distance ΔS2 = 210 mm (the length of the short side of A4), that is, 210 mm / 126 mm / second = 1.7 seconds. Or more: T2 = 2α + 1.7 seconds.

  Therefore, when the estimation unit 232 estimates that “the two originals SH1 and SH2 are the same paper type”, the time difference T2−T1 = 1.7 seconds−80 milliseconds = 1.6 seconds, compared with the case where the estimation unit 232 does not estimate. Early, the paper type information generation unit 233 can notify the main control unit 60 of the paper type of the second document SH2. In response to this, the main control unit 60 designates the imaging condition for the scanner 120 and the paper feed to be selected for the printer 130, compared to the case where the above estimation is not performed. The cassette CS1,..., And the timing for designating the printing conditions such as the fixing temperature, transfer current, and separation voltage can all be advanced. As a result, both the document feed interval by the ADF 110 and the sheet conveyance interval by the feeding unit 10 of the printer 130 are averaged compared to the case where all the document types are determined as in the first step. Can also be shortened.

[ADF paper feed process flowchart]
FIG. 10 and FIG. 11 are flowcharts of paper feed processing by the paper feed unit 200 of the ADF 110. This process is started when the operation unit 50 detects pressing of the start button on the operation panel 101.
In step S100, the control unit 234 first causes the determination unit 231 to detect the light amount of the light emitting element 210 to the second light receiving element 212, and calculates the transmittance of the determination region DTR from the light amount. Next, the control unit 234 compares the calculated value with the value in the paper type table stored in the ROM 63 to determine whether or not a document is stored in the paper feed tray 112. If this calculated value is “80-100%” shown in (a) of FIG. 8 or the like indicating that “the document is not stored in the paper feed tray 112” in the paper type table, the process is terminated. If not, the process proceeds to step S101.

  In step S101, since the document is stored in the paper feed tray 112, the first process (or the fourth process) is started. As shown in FIG. 7A (or (d)), the control unit 234 presses the pickup roller 11A against the bundle of documents DC0, and the first document SH1 (or the second document) positioned at the top of the bundle DC0. The tip of SH2) is advanced from the bundle DC0 to the discrimination area DTR. The control unit 234 further controls the first time point when the pickup roller 11A is in direct contact with the first document SH1 (or the first document SH1 is separated from the second document and sent to the conveyance path, and the pickup roller 11A is A time from the fifth time point (which is in direct contact with the second document SH2) to the second time point (or sixth time point) when the leading edge of the first document SH1 (or the second document SH2) reaches the determination region DTR is predicted. . Thereafter, the process proceeds to step S102.

In step S102, the determination unit 231 refers to the flag DTD set in the RAM 62. If the value of the flag DTD is “1”, the process proceeds to step S103, and if it is “0”, the process proceeds to step S106. Note that the initial value of the flag DTD can be set to “1” or “0” by the user.
Since the value of the flag DTD is “1” in step S103, the document whose leading end is currently located in the determination area DTR is the target for determining the paper type. If it is the 1st process, the control part 234 will measure the elapsed time from the 1st time, and if it is the 4th process, it will measure the elapsed time from the 5th time. When each measured value reaches the predicted value obtained in step S101, the control unit 234 notifies the determination unit 231 that it is the light irradiation time for the determination region DTR. In response to the notification, the determination unit 231 causes the light emitting element 210 to emit light to the determination region DTR, causes the first light receiving element 211 to detect the amount of light reflected from the determination region DTR, and causes the second light receiving element 212 to Detects the amount of light transmitted from the region DTR. From the detection result at this time, the determination unit 231 reads the reflected light amount / transmitted light amount and calculates the reflectance / transmittance of the document. Thereafter, the process proceeds to step S104.

  In step S104, the discrimination unit 231 discriminates the paper type TYP of the original by comparing the reflectance / transmittance of the original measured in step S103 with the value indicated in the paper type table. Here, for example, the transmittance of the document indicates that “the light detected by the second light receiving element 212 is transmitted through the print region of the document” such as “0 to 30%” shown in FIG. If it is a value, the determining unit 231 determines that “the paper type has failed to be determined”, interrupts the processing, and notifies the user of the failure by displaying the operation panel 101 or the like. On the other hand, if the paper type is successfully determined, the process proceeds to step S105.

  In step S <b> 105, the control unit 234 embeds the paper type TYP determined by the determination unit 231 in step S <b> 104 and transmits the information to the main control unit 60. In response to this, the main control unit 60 reads the paper type TYP from the information, specifies the imaging condition to be set for the scanner 120 based on the paper type TYP, and specifies the paper feed cassette to be selected for the printer 130. Specify printing conditions such as parameter values to be set. Thereafter, the process proceeds to step S106.

  In step S106, the controller 234 first weakens the downward force FC2 applied to the document bundle DC0 from the pickup roller 11A. As a result, the leading edge of the first document SH1 further advances from the discrimination area DTR over the wall 222 of the stop plate 202, and the leading edge of the second document SH2 advances along the flat portion 221 of the stop plate 202. . At the same time, the control unit 234 reaches the determination region DTR from the third time point when the downward force FC2 is weakened to the pickup roller 11A while the front end portion of the second document SH2 overlaps the first document SH1. Predict the time to the point. Thereafter, the process proceeds to step S107.

  In step S107, the control unit 234 measures the elapsed time from the third time point, and when the measured value reaches the predicted value, the estimation unit 232 irradiates the discrimination region DTR with light, and the pickup roller 11A In this case, the downward force FC3 applied to the original bundle DC0 is increased again, and the rotation of the feed roller 12A is stopped (or reversed). The estimation unit 232 detects the amount of transmitted light from the discrimination region DTR, and calculates the transmittance TR3 of the two originals SH1 and SH2 overlapping in the discrimination region DTR from the detection result. Thereafter, the process proceeds to step S108.

  In step S108, the estimation unit 232 first substitutes the transmittance TR1 of the first document SH1 calculated by the determination unit 231 in step S103 into the relational expression related to the paper type TYP determined by the determination unit 231 in step S104. The paper thickness TH1 of the document SH1 is obtained. Next, the estimation unit 232 substitutes twice the paper thickness TH1 TH2 = TH1 × 2 into the same relational expression, and estimates the transmittance TR2 when two sheets of paper type TYP overlap. Thereafter, the process proceeds to step S109.

In step S109, the estimation unit 232 checks the transmittance TR3 measured in step S107 with the transmittance TR2 estimated in step S108. If both values TR3 and TR2 match except for an error within the allowable range, the process proceeds to step S110, and if the two values TR3 and TR2 are different beyond the error within the allowable range, the process proceeds to step S112.
In step S110, since the measured value TR3 of the transmittance matches the estimated value TR2 except for an error within an allowable range, it is estimated that “the two originals that overlap in the discrimination region DTR are the same paper type”. The part 232 estimates. In response to this, the paper type information generation unit 233 sets a value “0” indicating that the second original SH2 is not a paper type discrimination target in the flag DTD set in the RAM 62. Thereafter, the process proceeds to step S111.

  In step S111, the control unit 234 embeds the paper type TYP of the first document SH1 determined by the determination unit 231 in step S104 and transmits it to the main control unit 60. In response to this, the main control unit 60 reads the paper type TYP from the information, specifies the imaging condition to be set for the scanner 120 based on the paper type TYP, and specifies the paper feed cassette to be selected for the printer 130. Specify printing conditions such as parameter values to be set. Thereafter, the process proceeds to step S113.

  In step S112, since the measured value TR3 of the transmittance is different from the estimated value TR2 by an error within an allowable range, the estimation unit 232 determines that “the two originals overlapping in the discrimination region DTR are the same paper type. Is not estimated. In response to this, the paper type information generation unit 233 sets a value “1” indicating that the second original SH2 is a paper type discrimination target in the flag DTD. Thereafter, the process proceeds to step S113.

  In step S113, the control unit 234 separates the first document SH1 from the second document SH2 by the pickup roller 11A and the paper feed roller 11B and sends it to the conveyance path as shown in FIG. In parallel with this, the control unit 234 first sends the first document SH1 to the transport path from the fourth time point when the leading edge of the second document SH2 reaches the determination area DTR while overlapping the first document SH1. A time until the fifth time point at which the pickup roller 11A is in direct contact with the second document SH2 is predicted. Next, the control unit 234 measures the elapsed time from the fourth time point, and when the measured value reaches the predicted value, the pickup roller 11A causes the downward force FC1 applied to the document bundle DC0 to be increased, and the feed roller In 12A, the rotation is restarted (or rotated forward). Thereafter, the process is repeated from step S100.

[Summary]
As described above, the paper feed unit 200 of the ADF 110 according to the embodiment of the present invention keeps the leading end of the next document SH2 overlapping the preceding document SH1 each time the leading end of one document SH1 is sent out from the bundle of documents DC0. Advancing to the discrimination region DTR causes the estimation unit 232 to detect the amount of transmitted light from the overlapping portion of the two originals SH1 and SH2. Further, when the estimation unit 232 estimates that “two originals of the same paper type as the first original SH1 overlap in the discrimination region DTR” based on the transmitted light amount, the paper supply unit 200 determines the paper type information generation unit 233. Information on the paper type is generated and transmitted to the main control unit 60.

  As a result, the paper feed unit 200 sets the main paper type of the second original document SH2 earlier than the case where it is estimated that “the first original document SH1 and the second original document SH2 are the same paper type”. The control unit 60 can be notified. In response to this, the main control unit 60 designates the imaging conditions for the scanner 120 and the paper cassette to be selected for the printer 130, rather than when the estimation is performed. And the timing for specifying the printing conditions can be advanced. As a result, both the document feeding interval by the ADF 110 and the sheet conveyance interval by the feeding unit 10 of the printer 130 can be reduced on average. In this way, the paper feed unit 200 can achieve accurate determination of the paper type of the original document while shortening the paper interval.

[Modification]
(A) The paper feed unit 200 according to the above-described embodiment of the present invention is incorporated in the ADF 110 installed in the MFP 100 and is used to determine the paper type of the document. In addition, the sheet conveying apparatus according to the present invention may be incorporated in an ADF installed in an image forming apparatus specialized for any function such as a copier, a scanner, or a FAX.

  The sheet conveying apparatus according to the present invention may also be incorporated in a paper feed cassette such as an image forming apparatus or a post-processing apparatus and used for discriminating paper types such as printing paper. As a result, it is possible to omit the setting of the paper type by the user or to check for a mistake in the setting. Further, even if different paper types are stored in the same paper feed cassette, it is possible to cause the image forming apparatus or the like to automatically use these paper types properly.

(B) The determination unit 231 and the estimation unit 232 according to the above embodiment share the light emitting element 210, the first light receiving element 211, and the second light receiving element 212. In addition, the two functional units may separately include one or both of the light emitting element and the light receiving element.
The determination unit 231 and the estimation unit 232 according to the above embodiment also measure the reflectance / transmittance of the document with respect to light. In addition, these functional units may measure the reflectance or transmittance of the sheet with respect to electromagnetic waves or sound waves (including ultrasonic waves) having a wavelength different from that of light.

In the above-described embodiment, the determination unit 231 also checks whether or not there are documents stored in the paper feed tray 112. In addition, the presence or absence of the document may be confirmed by another sensor embedded in the paper feed tray 112.
(C) The discriminating unit 231 according to the above embodiment discriminates the paper type from both the reflectance and transmittance of the document. In addition, the determination unit may determine the paper type from only one of the reflectance and transmittance of the sheet.

  (D) The estimation unit 232 according to the above embodiment first obtains the paper thickness per original of the paper type determined by the determination unit 231 using the relational expression between the transmittance and thickness of the paper type, Next, the transmittance for twice the paper thickness is estimated. In addition, the transmittance of a two-ply sheet is stored in advance in a storage unit such as a ROM for each paper type, and the estimation unit stores the transmittance value corresponding to the paper type determined by the determination unit from the storage unit. You may read and compare with the measured value of the transmittance | permeability.

  (E) In the third step, the document feeding mechanism 201 according to the above-described embodiment stops or reverses the rotation of the feeding roller 12A as shown in FIG. In addition, even if the feed roller 12A continues to rotate in the forward direction, the pickup roller 11A prevents the leading edge of the second document SH2 from getting over the wall 222 of the stop plate 202 while it overlaps the first document SH1. The downward force applied to the document bundle DC0, the size or rotational speed of the feed roller 12A, the height of the wall 222, or the like may be adjusted.

  The delivery mechanism may also include a retard roller instead of the pair of the rolling roller 11B and the delivery roller 12A. This retard roller is installed at the boundary between the separation plate 201 and the flat portion 221 of the stop plate 202, like the feed roller 12A. However, the direction in which the retard roller rotates with the driving force from the power source is opposite to that of the feed roller 12A. A clutch is provided between the retard roller and its power source. This clutch transmits the driving force from the power source to the retard roller while the magnitude of the torque received by the retard roller from the contact partner document is less than the threshold, and if the torque reaches the threshold, the driving force Block transmission. This threshold value is set within the following range, for example.

  As shown in FIG. 7B, the upper limit of this range is that the front end of the second document SH2 and the first document SH1 with which the pickup roller 11A is in direct contact are stacked with the two documents overlapped. This is less than the magnitude of the torque that the retard roller receives from the second document SH2 when it is advanced from DC0 in the paper feeding direction. As a result, as shown in FIG. 7B, while the pickup roller 11A advances the two documents SH1 and SH2 while overlapping each other, the clutch blocks the transmission of the driving force, so that the retard roller is the second roller. As the document SH2 moves forward, it rotates forward. Therefore, the leading end of the second document SH2 smoothly enters the determination area DTR.

  The lower limit of the above range is that the retard roller receives from the original SH2 when the leading edge of the second original SH2 is in contact with the wall 222 of the stop plate 202 and is stationary as shown in FIG. It is larger than the magnitude of the torque. Thus, as shown in FIG. 7B, the clutch transmits the driving force after the advance of the second document SH2 is blocked by the wall portion 222 of the stop plate 202, so that the retard roller reverses. Therefore, even if the leading end of the document SH3 following the second document SH2 climbs up to the upper end of the separation plate 201, it receives a frictional force in the direction opposite to the feeding direction from the retard roller. Entry to 221 is blocked.

  Thereafter, as shown in FIG. 7D, when the first document SH1 is separated from the second document SH2 and sent out to the conveyance path, the pickup roller 11A comes into direct contact with the second document SH2. At this time, since the friction force in the paper feeding direction received by the second original SH2 from the pickup roller 11A is increased, the magnitude of the torque received by the retard roller from the second original SH2 again exceeds the threshold value. As a result, the clutch blocks the transmission of the driving force, so that the retard roller rotates normally as the second document SH2 advances. Accordingly, the leading edge of the second document SH2 moves over the wall 222 of the stop plate 202 and further advances, and the leading edge of the subsequent document SH3 enters the flat portion 221 of the stop plate 202.

  As described above, the document feeding mechanism is not limited to the structure of the embodiment shown in FIG. 3, and other structures are possible.

  The present invention relates to a technique for discriminating a paper type when a sheet is sent out from a bundle of sheets, and the leading edge of the next sheet is overlapped on the leading edge each time one sheet is fed from the bundle as described above. The transmittance is detected while moving forward. Thus, the present invention is clearly industrially applicable.

100 MFP
101 Operation panel 102 Paper discharge space 110 ADF
DESCRIPTION OF SYMBOLS 111 Paper feed port 112 Paper feed tray 120 Scanner 130 Printer 131 Paper discharge port 133 Paper feed cassette 200 ADF paper feed part 11A Pickup roller 11B Paper feed roller 12A Feeding roller 12B Rolling roller 201 Separation plate 202 Stop plate 221 Stop plate flat Unit 222 wall of stop plate 210 light emitting element 221 first light receiving element 222 second light receiving element 231 discriminating unit 232 estimating unit 233 paper type information generating unit 234 control unit

Claims (8)

An accommodating portion for accommodating a bundle of sheets;
First, the leading end of the first sheet is fed out from the bundle toward the conveyance path, and then the leading end of the second sheet is fed out from the bundle in a state of being overlapped with the first sheet, and then the first sheet is A transport unit that separates the second sheet and sends it to the transport path;
Detecting at least one of reflectance or transmittance with respect to a predetermined electromagnetic wave or sound wave from a portion of the first sheet that does not overlap the second sheet, and discriminating the paper type of the first sheet from the detected value. A discriminator;
The transmittance for a predetermined electromagnetic wave or sound wave is detected from the overlapping portion of the first sheet and the second sheet, and the second sheet is the same paper type as the first sheet based on the detected value. An estimation unit for estimating
For the first sheet, information indicating the paper type determined by the determination unit is generated, and for the second sheet, the estimation unit determines that the second sheet is the same paper type as the first sheet. If estimated, a paper type information generation unit that generates information indicating the paper type,
A sheet conveying apparatus.   The said discrimination | determination part does not discriminate | determine the paper type of the said 2nd sheet, when the said estimation part estimates that the said 2nd sheet is the same paper type as the said 1st sheet. Sheet conveying device.   When the estimation unit does not estimate that the second sheet is the same paper type as the first sheet, the conveyance unit separates the first sheet from the second sheet and sends it to the conveyance path. After the time point, the determination unit detects at least one of the reflectance or transmittance of the tip of the second sheet with respect to a predetermined electromagnetic wave or sound wave, and determines the paper type of the second sheet from the detected value. The sheet conveying apparatus according to claim 1, wherein the paper type information generation unit generates information indicating the paper type.   The estimation unit compares the transmittance of the overlapping portion with the transmittance when two sheets of the same paper type as the first sheet are stacked, and the difference between the two transmittances is equal to or less than a threshold value. 4. The sheet conveying apparatus according to claim 1, wherein the second sheet is estimated to be the same paper type as the first sheet. 5. The discriminating unit detects the transmittance of the leading end of the first sheet with respect to a predetermined electromagnetic wave or sound wave and uses it to discriminate the paper type of the first sheet,
The estimation unit includes
Including a storage unit that stores a relational expression between the transmittance and the thickness of the sheet with respect to the electromagnetic wave or the sound wave in a paper type,
A relational expression for the paper type of the first sheet is read from the storage unit, and the thickness of the first sheet is calculated by substituting the transmittance detected by the determination unit into the relational expression. The transmittance when two sheets of the same paper type as the first sheet are stacked is estimated by substituting twice the thickness into the first sheet. The sheet conveying apparatus according to claim 1. The accommodating portion includes a lift portion that applies an upward force to the bundle,
The transport unit is
A plate-like member that is installed between the accommodating portion and the conveyance path and is inclined with respect to the conveyance direction;
A shelf-like member including a flat part extending horizontally from an upper end of the slope of the plate-like member, and a wall part rising near the entrance of the conveyance path;
A pickup roller that can be moved up and down above the bundle and that rotates while applying a downward force to the upper surface of the bundle, thereby feeding out the sheets from the bundle to the shelf member in order from the top;
The sheet is provided in the vicinity of the entrance of the transport path or downstream of the entrance, and the sheet is separated from the bundle by rotating by contacting the upper surface of the sheet over the shelf-like member by the pickup roller. A feed roller that feeds the road,
The front end is installed at the boundary between the storage portion and the flat portion of the shelf-like member and rotates in contact with the lower surface of the front end portion of the sheet that has climbed up to the boundary along the inclination of the plate-like member. A feed roller that advances the portion toward the wall of the shelf-like member;
A power source for applying a driving force to the pickup roller, the paper feed roller, and the delivery roller;
A control unit for controlling the driving force of the power source, the downward force applied by the pickup roller to the bundle, and the upward force applied by the lift unit;
Including
Under the control of the control unit, the leading end portion of the second sheet is lower than the upper end of the inclination of the plate-like member while the leading end portion of the first sheet advances from the bundle to the wall portion of the shelf-like member. And after the time when the leading edge of the first sheet gets over the wall, the plate rises to the upper end of the inclination of the plate-like member and comes into contact with the feed roller, and remains stationary after the time when it contacts the wall. The sheet conveying apparatus according to any one of claims 1 to 5, wherein the sheet conveying apparatus is configured as described above.   A bundle of documents is accommodated as the bundle of sheets, the document is separated from the bundle, and conveyed to a position where an image reading device can read an image of the document. An automatic document feeder provided with the sheet conveying device according to any one of the preceding claims. The sheet conveying device according to any one of claims 1 to 6, wherein the sheet is separated and sent out from a bundle of sheets;
An image forming unit that forms an image on the sheet fed by the sheet conveying device;
An image forming apparatus.

Images