Sheet discrimination apparatus and image forming apparatus

Abstract

To provide a sheet discrimination apparatus and an image forming apparatus that can prevent the influence of paper powder from a sheet to accurately discriminate the characteristics of the sheet.SOLUTION: A sheet discrimination apparatus 2 comprises: a light emitting device for reflection 211 that causes a light receiving device 220 to receive light reflected on a sheet; and a reflecting member 23 that is provided opposite to the light emitting device for reflection 211, reflects light radiated by the light emitting device for reflection 211 when the sheet is not conveyed by a conveying member 24, and makes the light incident on the light receiving device 20 provided opposite thereto. The light emitting device for reflection 211 includes a first light emitting device for reflection 211a that radiates light with a first wavelength, a second light emitting device for reflection 211b that radiates light with a second wavelength, and a third light emitting device for reflection 211c that radiates light with a third wavelength. The light with the first wavelength and the light with the second wavelength are near infrared light and violet visible light, respectively. The reflecting member 23 is provided so that, of the rays of light radiated by the light emitting devices 21, the reflectance of the light with the second wavelength becomes closest to the reflectance of the light with the first wavelength.SELECTED DRAWING: Figure 3A

Description

[Technical Field]

[0001] The present invention relates to a paper discrimination device and an image forming apparatus. [Background technology]

[0002] Conventionally, there has been known a paper discrimination device that automatically discriminates characteristics such as the paper type of the paper being conveyed using a sensor. Another known paper discrimination device is one that automatically discriminates the paper type by using a sensor to receive light reflected from a paper that has been irradiated from a light source.

[0003] In such a paper discrimination device, as disclosed in Patent Document 1, for example, a reflecting member is provided to determine the reference amount of light received by the sensor. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent application No. 2022-132537 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the paper discrimination device of Patent Document 1, there is a risk that paper dust from paper may adhere to the reflective member or the optical path. When paper dust adheres to the reflective member or the optical path, the paper dust changes the light reflection characteristics. As a result, the amount of light received by the sensor, which serves as the reference for detection when no paper is passing through, changes, and there is a risk that the accuracy of paper type discrimination, etc., will decrease.

[0006] The present invention has been made in view of the above circumstances, and has as its object to provide a paper discrimination device and an image forming apparatus that can discriminate paper characteristics with high accuracy by suppressing the influence of paper dust from the paper. [Means for solving the problem]

[0007] In order to solve the above problems, the invention described in claim 1 is as follows: A paper discrimination device including a discrimination unit that discriminates characteristics of a paper sheet conveyed along a predetermined conveying member by receiving light emitted from a light-emitting element and received by a light-receiving element, the light-emitting element includes a reflective light-emitting element that causes the light-receiving element to receive light reflected by the paper; a reflecting member that is provided opposite the reflective light emitting element, and that reflects light emitted by the reflective light emitting element when the paper is not being transported on the transport member, causing the light to be incident on the light receiving element that is provided opposite the reflective light emitting element; the reflective light-emitting element includes a first reflective light-emitting element that irradiates light of a first wavelength, a second reflective light-emitting element that irradiates light of a second wavelength, and a third reflective light-emitting element that irradiates light of a third wavelength; the first wavelength is a wavelength in the range of 750 nm to 1100 nm; the second wavelength is in the range of 390 nm to 440 nm; The reflecting member is provided so that the reflectance of the light having the second wavelength among the light emitted by the light emitting element is closest to the reflectance of the light having the first wavelength.

[0008] The invention described in claim 2 is the paper discrimination device described in claim 1, The reflecting member is provided so that the reflectance of the light of the first wavelength is the same as the reflectance of the light of the second wavelength.

[0009] The invention described in claim 3 is the paper discrimination device described in claim 1, The light emitting element includes a transmission light emitting element that is provided at a position facing the reflection light emitting element and causes the light receiving element to receive light that has passed through the paper.

[0010] The invention described in claim 4 is the paper discrimination device described in claim 1, The carrying member has an opening in a range including a portion facing the light emitting element.

[0011] The invention described in claim 5 is the paper discrimination device described in claim 4, The transport member includes a transparent protective material having light-transmitting properties so as to cover the opening.

[0012] The invention described in claim 6 is the paper discrimination device described in claim 4, The reflecting member is provided on the outside of the transport member.

[0013] The invention described in claim 7 is the paper discrimination device described in claim 6, The transport member includes a transparent protective material having light-transmitting properties so as to cover the openings on the light receiving element side and the reflecting member side.

[0014] The invention described in claim 8 is the paper discrimination device described in claim 6, the reflective light emitting element is provided below the transport member in the up-down direction, The reflecting member is provided above the conveying member in the up-down direction.

[0015] The invention described in claim 9 is the paper discrimination device described in claim 1, the third wavelength is a wavelength in the range of 200 nm to 400 nm; The reflecting member is provided so that the reflectance of the light having the third wavelength is less than the reflectance of the light having the first wavelength.

[0016] The invention described in claim 10 is the paper discrimination device described in claim 1, The discrimination unit discriminates whether the paper type is plain paper, recycled paper, or colored paper.

[0017] The invention described in claim 11 is an image forming apparatus, a paper discrimination device according to any one of claims 1 to 10; and an image forming unit that forms an image on the paper. [Effects of the Invention]

[0018] According to the present invention, the influence of paper dust on the paper can be suppressed and the characteristics of the paper can be determined with high accuracy. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 2 is a schematic cross-sectional side view of the image forming apparatus. [Figure 2] FIG. 1 is a block diagram of an image forming apparatus. [Figure 3A] FIG. 2 is a schematic side view of a paper inspection unit according to the first embodiment. [Figure 3B] FIG. 2 is a schematic top view of a paper inspection unit according to the first embodiment. [Figure 4] 10 is a flowchart of a paper type determination process. [Figure 5A] 10A and 10B are diagrams for explaining one aspect of discrimination of recording materials using wavelength dependency of optical characteristics of first and third wavelengths. [Figure 5B] 10A and 10B are diagrams for explaining one aspect of discrimination of recording materials using wavelength dependency of optical characteristics of first and second wavelengths. [Figure 6] FIG. 10 is a diagram for explaining the reflectance spectrum of plain paper. [Figure 7] FIG. 10 is a schematic side view of a paper inspection unit according to the second embodiment. [Figure 8A] 10A and 10B are diagrams for explaining one aspect of discrimination of recording materials using wavelength dependency of optical characteristics of first, third, and fourth wavelengths. [Figure 8B] 10A and 10B are diagrams for explaining one aspect of discrimination of recording materials using wavelength dependency of optical characteristics of first, second, and fourth wavelengths. [Figure 8C] 10A and 10B are diagrams for explaining one aspect of discrimination of recording materials using wavelength dependency of optical characteristics of first, fourth, and fifth wavelengths. [Figure 9A] FIG. 10 is a schematic diagram of a paper inspection unit according to a modified example. [Figure 9B] FIG. 10 is a schematic diagram of a paper inspection unit according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, a paper type discrimination device according to an embodiment of the present invention will be described with reference to the drawings. However, the scope of the present invention is not limited to the illustrated examples. In the following description, components having the same functions and configurations will be given the same reference numerals, and their description may be omitted.

[0021] [Overall configuration of image forming device] 1 is a diagram showing a schematic configuration of an image forming apparatus 1 according to an embodiment of the present invention, and FIG.

[0022] The image forming apparatus 1 is an MFP (Multifunction Peripheral) that forms an image on paper using an electrophotographic method. The image forming apparatus 1 includes a control unit 10, a paper inspection unit 20, an image forming unit 30, a fixing unit 40, a scanner 50, an operation display unit 60, a communication unit 70, a paper feed tray 81, a transport roller 82, a paper discharge tray 83, and a bus 90.

[0023] 2, a paper discrimination device 2 that discriminates the type of paper is configured by the control unit 10 and the paper inspection section 20. Furthermore, the various sections of the image forming apparatus 1 are connected by a bus 90.

[0024] (Control unit) The control unit 10 includes a CPU 11 (Central Processing Unit), a RAM 12 (Random Access Memory), and a storage unit 13.

[0025] {Storage section} The storage unit 13 is configured with a non-volatile storage device such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a flash memory. The storage unit 13 includes a program storage area and a data storage area. The program storage area stores data for various programs. The data storage area stores, for example, image data acquired by the scanner 50, image data input from the outside via the communication unit 70, and / or reference data referenced in the paper type discrimination operation described below.

[0026] {CPU} The CPU 11 reads and executes a program stored in a program storage area of the storage unit 13 (or a program stored in a storage device outside the image forming apparatus 1), and performs various arithmetic operations.

[0027] {RAM} The RAM 12 provides a working memory space for the CPU 11 and temporarily stores data.

[0028] The control unit 10 controls each unit of the image forming apparatus 1 by causing the CPU 11 to execute a program. For example, the control unit 10 operates each unit of the image forming unit 30 (particularly the transport roller 82 and the fixing unit 40) based on image data stored in the storage unit 13 to form an image on a sheet. Here, the CPU 11 changes the image formation-related operations of each unit of the image forming apparatus 1 according to the paper type discrimination result by the paper discrimination device 2. For example, the CPU 11 changes the transport speed and clamping pressure of the transport roller 82 according to the type of paper. The CPU 11 also changes the heating temperature and applied pressure of the fixing unit 40 according to the type of paper.

[0029] In addition, the control unit 10 may include a dedicated circuit (such as an ASIC (application specific integrated circuit) or FPGA (field-programmable gate array)) for realizing each function instead of or in addition to the CPU 11.

[0030] (Paper Inspection Department) The paper inspection unit 20 performs a paper type discrimination process. The paper inspection unit 20 is provided at a position along the paper transport path from the paper feed tray 81 to the paper output tray 83, upstream of the image forming unit 30. However, the position of the paper inspection unit 20 is not limited to this, and the paper inspection unit 20 can be placed at any position along the transport path.

[0031] The detailed configuration of the paper inspection unit 20 (paper discrimination device 2) will be described later.

[0032] (Image forming section) The image forming unit 30 forms an image by applying toner (color material) to paper supplied from the paper feed tray 81. The image forming unit 30 includes an intermediate transfer belt 31, an image forming unit 32, and a transfer roller 33. The intermediate transfer belt 31 is an endless belt-shaped member that is stretched around a plurality of rollers and moves in a circular motion.

[0033] {Image forming unit} The image forming units 32 are arranged along the intermediate transfer belt 31, and form toner images of the colors C (cyan), M (magenta), Y (yellow), and K (black) on the intermediate transfer belt 31 based on image data relating to the image to be printed. When a sheet of paper passes through the nip between the intermediate transfer belt 31 and the transfer roller 33, the toner images are transferred to the sheet of paper to form an image. Note that, although the image forming unit 30 capable of forming a color image has been exemplified in this embodiment, the present invention is not limited to this, and an image forming unit 30 capable of forming a monochrome image may also be used.

[0034] (fixing part) The fixing unit 40 applies heat and pressure to the paper onto which the toner image has been transferred, fixing the toner image to the paper. The fixing unit 40 includes a pair of rollers consisting of a heating roller and a pressure roller that sandwich the paper. The paper with the fixed toner image is transported by transport rollers 82 and sent to a paper output tray 83. The heating and pressure conditions used by the fixing unit 40 are controlled by the control unit 10 according to the type of paper, etc.

[0035] (scanner) The scanner 50 includes an optical system such as a light source and a reflecting mirror, and an imaging element, and reads an image of a sheet of paper being transported along a predetermined transport path or a sheet of paper placed on a platen glass, and generates image data in bitmap format for each of the colors R (red), G (green), and B (blue). The generated image data is stored in the storage unit 13. The scanned image can also be copied onto another sheet of paper by performing image formation by the image forming unit 30 based on this image data.

[0036] (Operation display) The operation display unit 60 includes a display device such as a liquid crystal display, a touch panel overlaid on the screen of the display device, and an input device such as operation keys. The operation display unit 60 displays various information such as the operation status and processing results of the image forming apparatus 1 on the display device, and converts user input operations on the input device into operation signals and outputs them to the control unit 10.

[0037] (Communications Department) The communication unit 70 is configured by a network card or the like. The communication unit 70 is connected to a communication network such as a LAN (Local Area Network) and transmits and receives information to and from external devices on the communication network. The control unit 10 communicates with the external devices on the communication network via the communication unit 70.

[0038] (Paper feed tray) Paper sheets before image formation are stored in the paper feed tray 81. The paper feed tray 81 may store a plurality of types of paper sheets.

[0039] The type of paper is characterized by at least one of the following characteristics: paper material (raw material), surface treatment state, presence and amount of fluorescent whitening agent, presence and color of bluing. Therefore, papers that differ from each other in at least one of these characteristics are different types of paper. Types of paper that can be stored in paper feed tray 81 include, for example, plain paper, colored paper, and recycled paper. However, the types of paper that can be stored in paper feed tray 81 are not limited to those mentioned above.

[0040] Plain paper is paper made primarily from wood-based pulp (i.e., pulp that is not recycled from waste paper, usually chemical pulp).

[0041] Colored paper is paper to which a certain percentage or more of dye has been added.

[0042] Recycled paper is paper that contains a specified or higher blending ratio of recycled paper pulp extracted from recycled paper.

[0043] (Transport roller) The transport rollers 82 rotate while holding a sheet of paper, thereby transporting the sheet along the transport path. The transport timing and transport speed of the transport rollers 82 are controlled by the control unit 10 according to the type of paper, etc.

[0044] (Output tray) The paper discharge tray 83 holds the paper on which the image has been formed until the user removes it.

[0045] [Paper inspection unit configuration] [First embodiment] Next, a detailed configuration of the paper inspection unit 20 according to the first embodiment will be described with reference to Fig. 3A. The paper inspection unit 20 includes a light emitting element 21, a sensor 22, a reflecting member 23, and a transport member 24.

[0046] (light-emitting element) The light emitting element 21 emits inspection light of a predetermined wavelength. The light emitting element 21 is, for example, an LED (Light Emitting Diode). The light emitting element 21 includes a reflective light emitting element 211 that causes the sensor 22 to receive light reflected by the paper during the paper type determination process described below.

[0047] As shown in FIG. 3A, the reflective light emitting element 211, the sensor 22, and the reflecting member 23 are provided at positions facing each other.

[0048] Fig. 3B shows a top perspective view of the paper inspection unit 20. As shown in Fig. 3B, the reflective light-emitting element 211 includes three elements, a first reflective light-emitting element 211a, a second reflective light-emitting element 211b, and a third reflective light-emitting element 211c, on the side of the sensor 22. It is preferable, but not limited to, that the reflective light-emitting elements 211 are provided at positions such that they are equally distant from the sensor 22.

[0049] {First Reflective Light-Emitting Element} In this embodiment, the first reflective light emitting element 211a irradiates infrared light (first inspection light) with a first wavelength having a peak wavelength of 750 nm or more and 1100 nm or less.

[0050] The reason for selecting wavelengths of 750 nm or more is to suppress the effects of paper bluing. Bluing is the process of adding a blue dye to paper to improve the whiteness of the paper. Bluing paper absorbs visible light of wavelengths outside the blue region, reducing the reflectance of the visible light (described later) compared to paper that is not bluing. Therefore, wavelengths of 750 nm or more that are not affected by such bluing are selected.

[0051] The reason for selecting wavelengths below 1100 nm is to suppress the effects of moisture contained in paper. The spectrum of light reflected by paper at wavelengths longer than 1100 nm changes depending on the moisture content of the paper. More specifically, moisture has a unique absorption band at 1450 nm and 1940 nm in the near-infrared region, which originates from the combined vibrations of the stretching and bending vibrations of hydrogen and oxygen atoms, reducing reflectance. For this reason, wavelengths below 1100 nm, which are not affected by the moisture content of paper, are selected.

[0052] In this way, light of a near-infrared wavelength, which is less likely to cause fluctuations in reflected light due to the material and raw material of the paper, is used as the first inspection light.

[0053] {Second Reflective Light-Emitting Element} In this embodiment, the second reflection light emitting element 211b emits purple light (second inspection light) with a second wavelength of 390 nm or more and 440 nm or less.

[0054] The wavelength of 390 nm or more and 440 nm or less is selected because it is a wavelength that is less absorbed by the fluorescent material and more absorbed by waste paper pulp, which means that irradiation with the second inspection light makes it possible to distinguish recycled paper that contains waste paper pulp.

[0055] {Third Reflective Light-Emitting Element} In this embodiment, the third reflection-emitting element 211c emits third inspection light of a third wavelength. As will be described later, the third reflection-emitting element 211c is used to determine whether the paper is colored paper. Colored paper absorbs light of a specific wavelength corresponding to the color of the dye. Therefore, the wavelength of the inspection light emitted by the third reflection-emitting element 211c may be set appropriately to a wavelength range in which absorption by the dye of the colored paper occurs.

[0056] The first to third inspection lights emitted from the reflective light emitting elements 211 are reflected by the surface of the paper and enter the sensor 22 .

[0057] (sensor) The sensor 22 receives the light emitted by the light-emitting element 21. The sensor 22 includes one light-receiving element 220. The light-receiving element 220 outputs a photocurrent corresponding to the amount of incident light. The sensor 22 converts the photocurrent into a voltage and then into digital data, which are then output to the control unit 10.

[0058] (reflective material) The reflective member 23 is a plate-like member that is provided to reflect the inspection light emitted by the reflective light-emitting element 211 and make it incident on the light-receiving element 220 when calibrating the light intensity of the reflective light-emitting element 211 when no paper is passing through.

[0059] The reflecting member 23 is provided so that the reflectance of the first inspection light and the reflectance of the second inspection light are substantially the same. For example, the reflectance of the inspection light at the reflecting member 23 can be adjusted by adjusting the color of the reflecting member 23.

[0060] The reflecting member 23 is not limited to one having substantially the same reflectance for the first and second inspection lights, but may be provided so that the reflectance for the second inspection light is closer to the reflectance for the first inspection light than the reflectance for the other inspection lights.

[0061] (Transportation member) The transport member 24 is a member that constitutes a transport path along which paper is transported to be subjected to paper type discrimination processing by the paper inspection unit 20. The transport member 24 includes an optical diaphragm 241 and a paper passage guide 242.

[0062] The optical diaphragm 241 is a plate-like member that is arranged on the side of the sensor 22 and the reflective light-emitting element 211 so that its main surface is perpendicular to the up-down direction. The optical diaphragm 241 has an opening H in a range that includes the portion facing the light-emitting element 21 and the sensor 22. The inspection light emitted by the light-emitting element 21 is incident on the paper through the opening H. The optical diaphragm 241 has light-blocking properties in the portions other than the opening H, and prevents light other than the inspection light from entering the paper.

[0063] The paper passing guide 242 is a plate-like member that is arranged on the side of the reflecting member 23 and the transmissive light emitting element 212 so as to support the paper being transported. In this embodiment, the reflecting member 23 is provided in a position of the paper passing guide 242 that faces the opening H of the optical diaphragm 241.

[0064] [Paper type detection process] As described above, the light receiving element 220 of the sensor 22 receives the reflected light that is the inspection light emitted by each reflective light emitting element 211 and reflected by the paper being transported on the transport member 24. At this time, the amount of reflected light received by the light receiving element 220 increases or decreases according to the absorption characteristics of light of each wavelength corresponding to the paper type. Therefore, the control unit 10 can determine the paper type of the paper from the reflection amount of the inspection light of each wavelength. In this way, in the paper type determination process, the control unit 10 functions as a determination unit that determines the characteristics of the paper, including the paper type.

[0065] The paper type discrimination process performed by the paper inspection unit 20 according to the first embodiment will be described in detail with reference to the flowchart in Fig. 4. First, the control unit 10 causes each of the reflective light-emitting elements 211 to emit inspection light toward the reflecting member 23, thereby calibrating the light intensity of each of the reflective light-emitting elements 211 (step S101).

[0066] Specifically, before the paper passes through the transport member 24, the control unit 10 causes each reflective light-emitting element 211 to emit inspection light, which is reflected by the reflecting member 23 and incident on the light-receiving element 220. The sensor 22 converts the incident inspection light into a voltage and outputs it to the control unit 10. The control unit 10 determines whether the voltage value of each light-emitting element 211 is within a predetermined range, and calibrates the light intensity of any reflective light-emitting element 211 that is outside the predetermined range.

[0067] Furthermore, the control unit 10 stores the voltage values generated in the sensor 22 by the irradiation of the test light from each of the calibrated reflective light emitting elements 211 as first to third reference voltages, respectively (step S102).

[0068] Next, the control unit 10 causes each of the reflective light emitting elements 211 to sequentially irradiate various types of inspection light onto the paper being transported through the gap between the optical diaphragm 241 and the paper passing guide 242 .

[0069] The first, second, and third inspection lights are reflected by the paper, generating first, second, and third reflected lights, which are incident on the light receiving element 220. The sensor 22 converts each of the incident reflected lights into a voltage (hereinafter referred to as first to third discrimination voltages), and outputs the voltages to the control unit 10. As described above, the amount of each reflected light is affected by the paper's absorption characteristics of the inspection light at each wavelength.

[0070] The control unit 10 acquires the reflectance of the test light of each light-emitting element 21 (hereinafter referred to as the first to third reflectances) using (the first to third discrimination voltages / the first to third reference voltages) (step S103). Then, the control unit 10 distinguishes the paper type from plain paper, colored paper, and recycled paper based on the acquired first to third reflectances.

[0071] Specifically, the control unit 10 first determines whether the paper is colored paper, plain paper, or recycled paper (step S104). FIG. 5A is a diagram illustrating this determination method. In the graph shown in FIG. 5A, the horizontal axis represents the first reflectance, and the vertical axis represents the ratio between the first reflectance and the third reflectance. In this way, by using the ratio of reflectances at different wavelengths, it is possible to suppress the effects of changes over time in the light receiving element 220 and changes in the position of the paper.

[0072] The graph in FIG. 5A shows values for colored paper (triangular spots) and non-colored paper (i.e., regular paper or recycled paper) (circular spots). Also, line L1 shown in FIG. 5A is a line set to distinguish between colored paper and non-colored paper. Information identifying line L1 is stored as reference data in memory unit 13. Based on the first reflectance and the third reflectance, control unit 10 determines whether the paper is colored paper or non-colored paper depending on whether the coordinates of the paper are located above line L1 in the graph in FIG. 4.

[0073] If the paper is determined to be other than colored paper (step S104; No), the control unit 10 determines whether the paper is plain paper or recycled paper (step S105). FIG. 5B is a diagram illustrating this determination method. In the graph shown in FIG. 5B, the horizontal axis represents the first reflectance, and the vertical axis represents the ratio between the first reflectance and the second reflectance. The graph in FIG. 5B also shows the values for plain paper (circular spots) and recycled paper (triangular spots). The line L2 shown in FIG. 5B is a line set to distinguish plain paper from recycled paper. Information identifying the line L2 is stored in the memory unit 13 as reference data. Based on the first reflectance and the second reflectance, the control unit 10 determines whether the paper is plain paper or recycled paper depending on whether the coordinates of the paper are located above the line L2 in the graph in FIG. 5B.

[0074] In such a paper type discrimination process by the paper inspection unit 20, if paper dust generated from the paper adheres to the reflecting member 23 or on the optical path to the reflecting member 23, the reflective light emitting element 211 is calibrated with an incorrect light intensity in step S101. As a result, a deviation occurs in the light intensity of the reflective light emitting element 211, which may reduce the accuracy of discriminating the paper type.

[0075] 5B, even if a relatively small calibration error occurs in the first reflective light-emitting element 211a and the second reflective light-emitting element 211b, there is a risk of misidentifying plain paper and recycled paper in step S105. Furthermore, since the fixing conditions in the fixing unit 40 are also different for plain paper and recycled paper, it is preferable to suppress the influence of paper dust, especially in the calibration of the first reflective light-emitting element 211a and the second reflective light-emitting element 211b.

[0076] The change in the amount of light received by the light receiving element 220 due to paper dust is proportional to (reflectance of paper dust - reflectance of reflective member 23) x amount of paper dust. Generally, plain paper is mainly used as paper, and therefore the paper dust is also mainly plain paper.

[0077] Figure 6 shows the reflectance spectrum of plain paper. In Figure 6, the horizontal axis represents the wavelength of the irradiated light, and the vertical axis represents reflectance. The solid line represents plain paper with a relatively large amount of phosphor, while the dotted line represents plain paper with a relatively small amount of phosphor. As shown in Figure 6, in the wavelength range above visible light (360 nm or above), the reflectance of plain paper, i.e., the paper dust reflectance, is approximately constant regardless of wavelength.

[0078] Therefore, as described above, the reflecting member 23 is provided so that the reflectance of the light emitted by the first reflection light-emitting element 211a and the reflectance of the light emitted by the second reflection light-emitting element 211b are close to each other. Specifically, the reflecting member 23 is provided so that the light-emitting element 21 that emits light with a reflectance closest to the reflectance of the light emitted by the first reflection light-emitting element 211a is the second reflection light-emitting element 211b. With this configuration, the amount of change in the amount of light received by the light-receiving element 220 due to paper powder adhering to the reflecting member 23 becomes close between the first reflection light-emitting element 211a and the second reflection light-emitting element 211b. As a result, it is possible to suppress a decrease in the accuracy of identifying characteristics of paper, including the paper type.

[0079] More preferably, the reflecting member 23 is provided so that the reflectance of light emitted by the first reflection light emitting element 211a and the reflectance of light emitted by the second reflection light emitting element 211b are the same. With this configuration, even if paper powder adheres to the reflecting member 23, the amount of change in the first reflection light emitting element 211a and the second reflection light emitting element 211b is the same, so the accuracy of identifying characteristics including the paper type of paper does not decrease.

[0080] [Second embodiment] Next, a paper inspection unit 20 according to a second embodiment will be described with reference to Fig. 7. Note that the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted. As shown in Fig. 7, the paper inspection unit 20 of the second embodiment differs from the first embodiment in the configuration of the light-emitting element 21 and the conveying member 24.

[0081] In the transport member 24 according to the second embodiment, the paper passing guide 242 has an opening H similar to the optical diaphragm 241. The reflecting member 23 is located below the paper passing guide 242 and has an opening.

[0082] {Transmissive light emitting element) The light-emitting element 21 of the paper inspection unit 20 according to the second embodiment includes a transmissive light-emitting element 212 (first transmissive light-emitting element 212a) on the side facing the sensor 22 and below the reflecting member 23. The first transmissive light-emitting element 212a irradiates fourth inspection light of a fourth wavelength. The fourth wavelength is a wavelength in the range of 750 nm to 1100 nm, similar to the first wavelength, but is a wavelength different from the first wavelength. Like the other light-emitting elements 21 described above, the first transmissive light-emitting element 212a calibrates the light intensity by irradiating the sensor 22 with the fourth inspection light when the paper is not being conveyed by the conveying member 24.

[0083] In this embodiment, the control unit 10 determines the characteristics of the paper, including the paper type, based on the transmittance of the first transmitted light (voltage of the first transmitted light / fourth reference voltage) (first transmittance) generated when the fourth inspection light passes through the paper, as shown in Figures 8A and 8B.

[0084] Compared to reflectance, the amount of light received changes less with changes in the position of the paper. Also, the amount of change in transmittance due to paper dust is also small. Therefore, the paper inspection unit 20 according to this embodiment can more accurately identify characteristics of the paper, including the paper type.

[0085] However, in this configuration, part of the light emitted by the first transmissive light emitting element 212a is reflected by the paper and the reflecting member 23 and enters the sensor 22 as so-called ghost light. If the light receiving element 220 receives this ghost light, an error may occur in the paper type discrimination process.

[0086] Therefore, in this embodiment, the reflecting member 23 is provided so that the reflectance of the inspection light irradiated by the first transmissive light emitting element 212a is relatively lower than the reflectance of the inspection light irradiated by the other light emitting elements 21. With this configuration, it is possible to prevent the inspection light irradiated by the first transmissive light emitting element 212a from being reflected by the paper and then by the reflecting member 23, i.e., to prevent the occurrence of ghost light. As a result, it is possible to prevent a decrease in the accuracy of the paper type discrimination process.

[0087] In this configuration, a step of identifying the paper brand may be added. As shown in Figure 6, paper containing a large amount of phosphor has a high reflectance at ultraviolet wavelengths indicated by the double arrow. On the other hand, paper with a small amount of phosphor has a low reflectance at ultraviolet wavelengths.

[0088] Therefore, a third inspection light having a wavelength of 200 nm or more and 400 nm or less is irradiated from the third reflection-emitting element 211c. Then, as shown in Fig. 8C, a plot is taken with the horizontal axis representing the transmittance of the first transmitted light and the vertical axis representing the ratio of the reflectance of the first reflected light to the reflectance of the third reflected light, and by comparing this with data previously stored in the storage unit 13, the paper brand can be identified.

[0089] In this case, it is preferable to provide the reflecting member 23 so that the reflectance of the third inspection light is lower than the reflectance of the first inspection light. With this configuration, changes in the ratio of the reflectance of the first reflected light to the reflectance of the third reflected light due to paper dust are suppressed, thereby improving the accuracy of identifying the paper brand.

[0090] [Other configurations] Although the present invention has been specifically described above based on the embodiments thereof, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the invention as defined in the claims and their equivalents.

[0091] 3A and 7, the configuration in which the light emitting element 21 is provided above and the reflecting member 23 is provided below is illustrated, but the present invention is not limited to this. For example, as shown in FIG. 9A, the light emitting element 21 may be provided below and the reflecting member 23 above. In this configuration, gravity makes it difficult for paper dust from paper to adhere to the reflecting member 23. Therefore, the effect of paper dust adhering to the reflecting member 23 can be further reduced.

[0092] 9B, a transparent protective material W may be provided to separate the conveying member 24 and the reflecting member 23. The transparent protective material W is a transparent plate-like body that transmits light emitted by the light-emitting element 21, and is provided to cover the opening H of the conveying member 24. With this configuration, the transparent protective material W can prevent paper dust from adhering to the reflecting member 23. Furthermore, as shown in FIG. 9B, when the transparent protective material W and the conveying member 24 are close to each other, paper dust can be blown away when the paper is conveyed.

[0093] 9B illustrates a configuration in which the transparent protective material W is provided so as to cover both the upper opening H and the lower opening H of the conveying member 24, but the present invention is not limited to this. For example, the transparent protective material W may be provided so as to cover only the upper opening H of the conveying member 24. In this configuration, it is possible to prevent paper dust from adhering to the sensor 22.

[0094] In the above description, the reflectance of the reflecting member 23 is adjusted because paper dust adheres to the reflecting member 23. However, paper dust may also adhere to places other than the reflecting member 23, and inspection light reflected by paper dust adhered to places other than the reflecting member 23 may enter the sensor 22, reducing the accuracy of paper type identification. Therefore, the conveying member 24 and the transparent protective material W may also be adjusted to have substantially the same reflective characteristics as the reflecting member 23. With this configuration, the characteristics of the paper can be identified with higher accuracy.

[0095] Furthermore, in the above example, the paper inspection unit 20 is provided with only three or four light emitting elements 21, but it goes without saying that five or more light emitting elements may also be provided. [Explanation of symbols]

[0096] 1. Image forming device 10 Control unit (discrimination unit) 20 Paper Inspection Department 2 Paper type discrimination device 21 Light-emitting element 211 Reflective light emitting element 211a First reflective light-emitting element 211b Second reflective light-emitting element 211c Third reflective light-emitting element 212 Transmissive light emitting element 220 Photodetector 23 Reflective material 24 Transport member 30 Image forming unit W Transparent protective material H opening

Claims

1. A paper discrimination device including a discrimination unit that discriminates characteristics of a paper sheet conveyed along a predetermined conveying member by receiving light emitted from a light-emitting element and received by a light-receiving element, the light-emitting element includes a reflective light-emitting element that causes the light-receiving element to receive light reflected by the paper; a reflecting member that is provided opposite the reflective light-emitting element, and that reflects light emitted by the reflective light-emitting element when the paper is not being transported by the transport member, causing the light to be incident on the light-receiving element that is provided opposite the reflective light-emitting element; the reflective light-emitting element includes a first reflective light-emitting element that irradiates light of a first wavelength, a second reflective light-emitting element that irradiates light of a second wavelength, and a third reflective light-emitting element that irradiates light of a third wavelength; the first wavelength is a wavelength in the range of 750 nm to 1100 nm; the second wavelength is a wavelength in the range of 390 nm to 440 nm; The sheet discrimination device, wherein the reflecting member is provided so that the reflectance of the light of the second wavelength emitted by the light emitting element is closest to the reflectance of the light of the first wavelength.

2. 2. The paper discrimination device according to claim 1, wherein the reflecting member is provided so that the reflectance of the light of the first wavelength is equal to the reflectance of the light of the second wavelength.

3. 2. The paper discrimination device according to claim 1, wherein the light emitting element comprises a transmission light emitting element provided at a position opposite the reflection light emitting element, and causing the light receiving element to receive light transmitted through the paper.

4. The paper discrimination device according to claim 1 , wherein the transport member has an opening in a range including a portion facing the light emitting element.

5. 5. The paper discrimination device according to claim 4, wherein the transport member includes a transparent protective material that transmits light and covers the opening.

6. 5. The paper discrimination device according to claim 4, wherein the reflecting member is provided outside the transport member.

7. 7. The paper discrimination device according to claim 6, wherein the transport member includes a transparent protective material having light-transmitting properties that covers the opening on the light receiving element side and the opening on the reflecting member side.

8. the reflective light emitting element is provided below the transport member in the up-down direction, 7. The paper discrimination device according to claim 6, wherein the reflecting member is provided above the conveying member in the vertical direction.

9. the third wavelength is a wavelength in the range of 200 nm to 400 nm; 2. The paper type discrimination device according to claim 1, wherein the reflecting member is provided so that the reflectance of the light of the third wavelength is less than the reflectance of the light of the first wavelength.

10. 2. The paper discrimination device according to claim 1, wherein the discrimination unit discriminates whether the paper type of the paper is plain paper, recycled paper, or colored paper.

11. a paper discrimination device according to any one of claims 1 to 10; an image forming unit that forms an image on the paper.

Images