Paper kind identification device and image forming device including paper kind identification device

Abstract

To provide a paper kind identification device for performing identification of the kind of a sheet with high accuracy.SOLUTION: A paper kind identification device 100 includes: a surface property measuring part 103 for measuring the surface property of a sheet from the sheet which moves by being inserted in a groove part; an upstream sheet sensor 104 provided on the upstream side in the insertion direction of the sheet with respect to the surface property measuring part 103, and for detecting the sheet; a downstream sheet sensor 105 provided on the downstream side in the insertion direction of the sheet with respect to the surface property measuring part 103, and for detecting the sheet; a machine physical property measuring part 102 for measuring the physical property of the sheet; and an information processing part 160. The information processing part 160 acquires a first measurement result by the surface property measuring part 103 and a second measurement result by the machine physical property measuring part 102, and acquires a parameter for identifying the kind of the sheet, based on the first measurement result and the second measurement result selected according to the detection result of the sheet by the upstream sheet sensor 104 and the detection result of the sheet by the downstream sheet sensor 105.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a paper type identification device capable of identifying the type of a sheet and an image forming apparatus provided with such a paper type identification device.

Background Art

[0002] In image forming apparatuses such as copiers, printers, facsimiles, and multifunction peripherals, the types of sheets that can be used for image formation are expanding. Image forming apparatuses are required to handle various types of sheets, such as papers with various thicknesses and stiffnesses, and synthetic papers using resin instead of pulp as raw materials.

[0003] An electrophotographic image forming apparatus generally forms an image on a sheet conveyed through a conveyance path by means of charging, exposure, development, transfer, and fixing processes. The optimal operating conditions in each process vary depending on the physical properties (stiffness, basis weight, surface properties, etc.) of the sheet used. Therefore, the image forming apparatus performs each process under operating conditions corresponding to the type of sheet whose type is registered in advance. The setting of the type of sheet to be used is performed by a user operation. If the user fails to correctly set the type of sheet, an image will not be formed under appropriate operating conditions. In this case, a normal image will not be formed on the sheet.

[0004] The image forming apparatus disclosed in Patent Document 1 includes an optical sensor for automatically identifying the type of a sheet. The image forming apparatus selects candidates for the sheet to be used from the types of sheets registered in advance based on the detection result of the optical sensor. The user can accurately set the type of sheet to be used for printing by selecting a sheet from the selected candidates.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

[0006] In the Print-on-Demand (POD) field, image forming machines are designed to handle high-mix, low-volume production, requiring frequent changes to the type of sheet used during image formation. Furthermore, the types of sheets used by image forming machines are diverse. To accommodate this wide variety of sheet settings and frequent changes, image forming machines are equipped with a paper type identification device that includes an optical sensor for identifying the sheet type. Ideally, the paper type identification device should be able to identify a wide range of sheet types and have high detection accuracy.

[0007] To improve detection accuracy, it is effective to use a line sensor with a larger sheet reading range as the optical sensor. The line sensor performs a continuous reading, reading the sheet to be identified while it is being transported. The sheet is inserted into the paper type identification device manually by the user. The transport speed of the sheet differs at the start of insertion, just before it hits the back, and after it hits the back. As a result, the line sensor will have variations in the reading results (reading data) of the sheet at these positions. When identifying the type of sheet using such varied reading data, the identification accuracy decreases. If the type of sheet is not accurately identified, the image forming apparatus may not be able to form an image under optimal operating conditions.

[0008] In view of the above-mentioned problems, the primary objective of the present invention is to provide a paper type identification device for highly accurate identification of sheet types. [Means for solving the problem]

[0009] The paper type identification device of the present invention is characterized by comprising: a groove into which a sheet to be identified is inserted; a first measuring means for measuring a first characteristic of the sheet from the sheet inserted into the groove and moving; a first detection means provided upstream of the first measuring means in the insertion direction of the sheet and for detecting the sheet inserted into the groove; a second detection means provided downstream of the first measuring means in the insertion direction of the sheet and for detecting the sheet inserted into the groove; a second measuring means for measuring a second characteristic of the sheet; and an information processing means that acquires a first measurement result from the first measuring means and a second measurement result from the second measuring means, selects the first measurement result according to the detection result of the sheet from the first detection means and the detection result of the sheet from the second detection means, and acquires parameters for identifying the type of sheet based on the selected first measurement result and second measurement result. [Effects of the Invention]

[0010] According to the present invention, the type of sheet can be identified with high accuracy. [Brief explanation of the drawing]

[0011] [Figure 1] Diagram showing the configuration of an image forming apparatus. [Figure 2] (a) and (b) are enlarged views of the fuser unit 201. [Figure 3] Diagram illustrating the control unit. [Figure 4] (a) and (b) are explanatory diagrams of the paper type identification device. [Figure 5] (a) and (b) are explanatory diagrams of the paper type identification device. [Figure 6] Diagram illustrating the paper type identification device. [Figure 7] (a) and (b) are diagrams showing the relationship between the surface properties of the sheet and the detected values ​​of the optical sensor. [Figure 8] A diagram illustrating areas that can be understood by skimming. [Figure 9] A timing chart for determining the region in which to calculate the cumulative difference value. [Figure 10]Exemplary diagram of memory space and data stored at each address of the memory. [Figure 11] Flowchart representing parameter acquisition process for identifying paper type. [Figure 12] Exemplary diagram of selection screen for paper type identification process. [Figure 13] Explanation diagram of relationship between ultrasonic transmission rate and basis weight. [Figure 14] Flowchart representing paper type identification process. [Figure 15] Explanation diagram of classification of surface properties. [Figure 16] Exemplary diagram of paper selection screen after paper type identification. [Figure 17] Exemplary diagram of paper selection screen after paper type identification. [Figure 18] Exemplary diagram of paper type database. [Figure 19] Exemplary diagram of paper type database. [Figure 20] Timing chart when measurement is performed during extraction. [[Embodiments of the Invention]]

[0012] Hereinafter, exemplary preferred embodiments of this invention will be described in detail with reference to the drawings.

[0013] (Image forming apparatus) FIG. 1 is a configuration diagram of the image forming apparatus of the present embodiment. The image forming apparatus 201 of the present embodiment is a tandem type - intermediate transfer type laser beam printer using an electrophotographic process. The image forming apparatus 201 forms and outputs a full - color or monochromatic image on a sheet P, which is a recording medium, based on image data acquired from an external device such as a personal computer via a network or image data acquired from an image reading device 300.

[0014] The image forming apparatus 201 has components for forming images inside the main body 201A, and an image reading device 300, an operation unit 502, and a paper type identification device 100 are provided on the upper part of the main body 201A. Between the main body 201A and the image reading device 300 of the image forming apparatus 201, there is an discharge space S through which the sheet P after image formation is discharged.

[0015] The image reading device 300 is a scanner that reads an image from a document and generates image data. The image reading device 300 is used during the document copying process. The operation unit 502 is a user interface equipped with an input interface and an output interface. The input interface is, for example, various key buttons, a touch panel, etc. The output interface is a display, a speaker, etc. The user can input various instructions to the image forming apparatus 201 using the operation unit 502. The paper type identification device 100 is a device for identifying the type of sheet P used for image formation (printing) by the image forming apparatus 201. Details of the paper type identification device 100 will be described later.

[0016] The image forming apparatus 201 includes an image forming unit 201B, an intermediate transfer unit 201C, a secondary transfer unit 201D, a fuser 201E, and a cassette paper feed unit 230 within the main body 201A.

[0017] The cassette paper feeding unit 230 feeds sheets P from the feed cassette 1 which stores the sheets P. The cassette paper feeding unit 230 includes a pickup roller 2 and a separation unit consisting of a feed roller 3 and a retard roller 4 for separating the sheets P fed out from the pickup roller 2. The sheets P are fed one by one from the feed cassette 1 by the pickup roller 2 and the separation unit. In this embodiment, a configuration in which multiple (four in this case) cassette paper feeding units 230 are provided is described, but there may be any number of cassette paper feeding units 230. The sheets P fed from the cassette paper feeding unit 230 are transported along the transport path to the register roller pair 240.

[0018] In addition to the cassette paper feed unit 230, the sheets P can also be fed from the manual feed unit 235. The manual feed unit 235 is equipped with a manual feed tray 5 on which the user places the sheets. Similar to the cassette paper feed unit 230, the manual feed unit 235 is equipped with a pickup roller and a separation unit, and the sheets P are fed one by one from the manual feed tray 5. The sheets P fed from the manual feed unit 235 are also transported along the transport path to the register roller pair 240.

[0019] The image forming unit 201B is a 4-drum full-color system and includes a laser scanner 210 and four process cartridges 211 that form toner images of four colors: yellow (Y), magenta (M), cyan (C), and black (K). Each process cartridge 211 includes a photosensitive drum 212, a charger 213, and a developer 214. A toner cartridge 215 is positioned above the process cartridges 211. The toner cartridge 215 supplies toner to the developer 214.

[0020] The intermediate transfer section 201C includes an intermediate transfer belt 216 wrapped around a drive roller 216a and a tension roller 216b. Inside the intermediate transfer belt 216 are four primary transfer rollers 219 that contact the intermediate transfer belt 216 at positions opposite each photosensitive drum 212. The intermediate transfer belt 216 rotates in the direction of the arrow by the drive roller 216a, which is driven by a drive unit (not shown).

[0021] The secondary transfer unit 201D includes a secondary transfer roller 217 positioned opposite the drive roller 216a, sandwiching the intermediate transfer belt 216. The fuser 201E is located downstream of the secondary transfer roller 217 in the sheet P transport direction and includes a pressure roller 220a and a heating roller 220b. Downstream of the fuser 201E in the sheet P transport direction, a first discharge roller pair 225a, a second discharge roller pair 225b, and a double-sided reversal unit 201F are arranged. The double-sided reversal unit 201F includes a reversible reversible roller pair 222 and a re-transport passage R for transporting the sheet P, on which an image has been formed on one side, to the image forming unit 201B.

[0022] The image forming apparatus 201, configured as described above, operates as follows: The image forming apparatus 201 acquires image data from the image reading device 300 or an external device and forms an image on the sheet P corresponding to the image data. In this process, the image forming apparatus 201 performs each image forming step under operating conditions corresponding to the type of sheet P.

[0023] The image forming unit 201B uniformly charges the surface of the photosensitive drum 212 to a predetermined polarity using the charger 213. The laser scanner 210 irradiates the uniformly charged surface of the photosensitive drum 212 with laser light modulated based on the image data. As a result, an electrostatic latent image corresponding to the color (yellow, magenta, cyan, black) is formed on the surface of each photosensitive drum 212.

[0024] The image forming unit 201B develops the electrostatic latent image formed on the photosensitive drum 212 by the developer unit 214. On each photosensitive drum 212, the electrostatic latent image is developed with toner of the corresponding color, forming a toner image of the corresponding color. The toner images are sequentially transferred from the photosensitive drum 212 to the rotating intermediate transfer belt 216 by the primary transfer roller 219. This forms a full-color toner image on the intermediate transfer belt 216. The intermediate transfer belt 216 rotates to transport the toner image to the secondary transfer unit 201D.

[0025] In parallel with this toner image formation operation, the sheets P are transported one by one to the register roller pair 240 by the cassette paper feed unit 230 or the manual paper feed unit 235. The register roller pair 240 corrects the skewness of the transported sheets P. After the skewness is corrected, the sheets P are transported by the register roller pair 240 to the secondary transfer unit 201D at the same time that the toner image carried by the intermediate transfer belt 216 is transported to the secondary transfer unit 201D. The secondary transfer unit 201D transfers the full-color toner image from the intermediate transfer belt 216 onto the sheets P using a secondary transfer bias applied to the secondary transfer roller 217.

[0026] The sheet P onto which the toner image has been transferred is transported to the fuser unit 201E. The fuser unit 201E grips and transports the sheet P using a roller nip section formed by a pressure roller 220a and a heating roller 220b. When gripping and transporting the sheet P, the fuser unit 201E heats the sheet P with the heating roller 220b, melting and mixing the toners of each color on the sheet P. The fuser unit 201E also pressurizes the sheet P with the pressure roller 220a, fixing the melted and mixed toners to the sheet P. At this time, the adhesive force of the melted toner generates a force that causes the sheet P to stick to the heating roller 220b.

[0027] Figure 2 is an enlarged view of the fuser unit 201E. If the rigidity (stiffness) of the sheet P is weak, the adhesive force generated on the sheet P against the heating roller 220b may cause the sheet P to be wound up by the rotating heating roller 220b (Figure 2(b)). For this reason, a separation plate 202 for separating the sheet P is provided downstream of the heating roller 220b in the direction of sheet P transport (Figure 2(a)).

[0028] The image forming apparatus 201 may determine the state of the separation plate 202 according to the type of sheet P. For example, when forming an image on a sheet P of low rigidity, the separation plate 202 is positioned so that its tip contacts the surface of the heating roller 220b, as shown in Figure 2(a), to separate the sheet P from the heating roller 220b. When forming an image on a sheet P of high rigidity, the sheet P is not wound onto the heating roller 220b. For this reason, the separation plate 202 is positioned so that its tip does not contact the surface of the heating roller 220b. This prevents the surface of the heating roller 220b from being worn down by the separation plate 202.

[0029] The sheet P on which the image has been fixed is discharged into the discharge space S by either the first discharge roller pair 225a or the second discharge roller pair 225b. The sheet P is then loaded onto the loading section 223, which is provided protruding from the bottom surface of the discharge space S. When forming an image on both sides of the sheet P, after the image has been fixed to one side, the sheet P is transported to the re-transport passage R by the reversing roller pair 222, and then transported again to the image forming section 201B, where an image is formed on the reversed side.

[0030] (Control Unit) Figure 3 is an explanatory diagram of the control unit that controls the operation of such an image forming apparatus 201. The control unit 400 is an information processing device equipped with, for example, a CPU (Central Processing Unit). The control unit 400 may also be implemented using an MPU (Micro Processor Unit) or an ASIC (Application Specific Integrated Circuit). The control unit 400 controls the image forming process performed by the image forming apparatus 201. In this embodiment, the control unit 400 is connected to the paper type identification device 100 and controls the paper type identification device 100. The control unit 400 is connected to a memory 401 and an operation unit 502. The memory 401 includes a paper type database 402. The paper type database 402 stores information such as the physical properties of various types of sheets, parameters for the operating conditions of each component during optimal image forming, whether paper can be fed into the image forming apparatus 201, and usable paper feed slots.

[0031] The paper type identification device 100 includes an information processing unit 160. The information processing unit 160 is an information processing device implemented by, for example, a CPU, MPU, or ASIC. The information processing unit 160 is communicatively connected to the control unit 400 and operates in cooperation with the control unit 400. The information processing unit 160 is connected to an upstream sheet sensor 104, a downstream sheet sensor 105, a mechanical property measurement unit 102, and a surface property measurement unit 103. The mechanical property measurement unit 102 includes an ultrasonic sensor 141 and a paper thickness sensor 140. The surface property measurement unit 103 includes an optical sensor 1031. The information processing unit 160 controls the operation of the upstream sheet sensor 104, the downstream sheet sensor 105, the mechanical property measurement unit 102, and the surface property measurement unit 103, and acquires the measurement results of each.

[0032] (Types of sheets used in image forming apparatus) The operating conditions of each component in each step of the image formation process (such as transport speed during fixing, fixing temperature, and transfer voltage during secondary transfer) vary depending on the physical properties of the sheet P on which the image is formed, including its basis weight, stiffness, surface properties, and material. Therefore, it is important to know in advance what type of sheet P will be used during image formation.

[0033] There may be restrictions on how sheets P can be loaded into the paper feed slot. The paper feed slots are paper cassette 1 and manual feed tray 5. For example, some thick paper with high rigidity can only be fed from manual feed tray 5, which has a small curvature in the transport path. Coated paper, which has a smooth surface and strong adhesion between sheets, must be fed one sheet at a time from manual feed tray 5. Paper made from pulp generally has different bending rigidity depending on the direction of the paper, due to the bias in the orientation direction (grain direction) of the pulp fibers that occurs due to the manufacturing process. For this reason, some pulp-based papers have recommended orientations for loading into the paper feed slot to reduce bending rigidity in the transport path. In addition, single-sided coated paper, which is coated on only one side compared to plain paper, has a specified up and down orientation when loading in order to form an image on the coated surface.

[0034] Some sheets cannot be used with the image forming apparatus 201. For example, thick paper with excessive stiffness may cause the paper to stop being transported due to the resistance when it is transported along the curved transport path. Thin paper with excessive stiffness is strongly affected by the adhesive force between the molten toner and the heating roller 220b as it passes through the fuser unit 201E, as described above. As a result, paper with excessive stiffness may not be peeled off the heating roller 220b by the separation plate 202 and may become wrapped around it (Figure 2(b)). In addition, synthetic paper made from synthetic resin instead of pulp may melt when heated in the fuser unit 201E, potentially contaminating the heating roller 220b.

[0035] (Paper type identification device) Figures 4, 5, and 6 are explanatory diagrams of the paper type identification device 100. Figure 4 shows the state before sheet P is inserted into the paper type identification device 100. Figure 5 shows the state after sheet P has been inserted into the paper type identification device 100. Figures 4(a) and 5(a) are views of the paper type identification device 100 from the side (the front direction of the image forming apparatus 201 in Figure 1). Figures 4(b) and 5(b) are views of the paper type identification device 100 from above. Figure 6 is a view of the paper type identification device 100 from the direction in which sheet P is inserted.

[0036] The paper type identification device 100 has a groove 101 into which the sheet P to be identified is inserted, and measures the physical properties of the sheet P inserted from the groove 101. The insertion of the sheet P is performed manually by the user. The groove 101 has an upper block 109 at the top and a lower block 110 at the bottom.

[0037] A sheet retaining member 106 is provided at the back of the groove in the lower block 110. The sheet retaining member 106 is biased toward the upper block 109 by a biasing member 107. The sheet P is inserted by pushing the sheet retaining member 106 downwards. The upper block 109 has a stopper portion 108 that protrudes toward the lower block 110 at the end of the sheet retaining member 106. Because the stopper portion 108 restricts the insertion of the inserted sheet P, the sheet P can be inserted up to the stopper portion 108. An information processing unit 160 is located behind the stopper portion 108.

[0038] The unit for measuring the physical properties of sheet P consists of a mechanical property measuring unit 102 and a surface property measuring unit 103. As sheet P passes through the measuring unit, physical properties such as basis weight, surface properties, and paper thickness of sheet P are acquired. An upstream sheet sensor 104 is positioned upstream of the surface property measuring unit 103 in the insertion direction of sheet P. A downstream sheet sensor 105 is positioned near the upstream side of the abutment unit 108 in the insertion direction of sheet P. In other words, the upstream sheet sensor 104 is positioned at the insertion start position of sheet P, and the downstream sheet sensor 105 is positioned at the insertion end position of sheet P. The upstream sheet sensor 104 and the downstream sheet sensor 105 each detect the inserted sheet P.

[0039] As shown in Figure 6, the mechanical property measurement unit 102 is configured such that the ultrasonic transmitter 130 is on the lower block 110 side and the ultrasonic receiver 131 is on the upper block 109 side, flanking the insertion passage through which the sheet P is inserted. The ultrasonic transmitter 130 and ultrasonic receiver 131 constitute an ultrasonic sensor 141. The mechanical property measurement unit 102 can detect the basis weight of the sheet P by transmitting and receiving ultrasonic waves through the insertion passage of the sheet P using the ultrasonic sensor 141. Basis weight is the mass per unit area of ​​the sheet P and is expressed in units of [gsm].

[0040] Both the ultrasonic transmitter 130 and the ultrasonic receiver 131 consist of a piezoelectric element (also called a piezo element), which is an element that converts mechanical displacement and electrical signals, and electrode terminals. When a pulse voltage of a predetermined frequency is input to the electrode terminals of the ultrasonic transmitter 130, the piezoelectric element oscillates and generates ultrasonic waves. The generated ultrasonic waves propagate through the air. When the ultrasonic waves reach the sheet P, the sheet P vibrates due to the ultrasonic waves. The ultrasonic waves generated by the ultrasonic transmitter 130 propagate through the sheet P to the ultrasonic receiver 131. The piezoelectric element of the ultrasonic receiver 131 generates an output voltage at its electrode terminals corresponding to the amplitude of the received ultrasonic waves. The output voltage is a voltage value corresponding to the basis weight of the sheet P. The output voltage is transmitted to the information processing unit 160 as a measured value.

[0041] Compared to the case where there is no sheet P between the ultrasonic transmitter 130 and the ultrasonic receiver 131, the output voltage due to the ultrasound transmitted through sheet P is attenuated. The information processing unit 160 calculates the transmittance of sheet P based on the ratio of the output voltage with and without sheet P. Since the transmittance of ultrasound changes depending on the thickness of sheet P, the information processing unit 160 can estimate the basis weight of sheet P using the ultrasonic transmission coefficient-basis weight conversion formula. In this way, the basis weight of sheet P is detected using the ultrasonic sensor 141.

[0042] An upstream sheet sensor 104, located on the upper block 109 upstream of the surface quality measurement unit 103 in the insertion direction of sheet P, detects the insertion of sheet P into the paper type identification device 100. A downstream sheet sensor 105, located on the upper block 109 downstream of the surface quality measurement unit 103 in the insertion direction of sheet P, detects the arrival of sheet P at the stopper 108, which is located at the position where sheet P has been fully inserted into the paper type identification device 100.

[0043] The paper thickness sensor 140 is positioned near the abutment portion 108. The paper thickness sensor 140 is lever-type, and as the lever tilts according to the thickness of the sheet P, an encoder linked to the lever rotates according to the amount it has tilted. While the encoder is rotating, the paper thickness sensor 140 transmits a pulse signal as a measured value of the paper thickness to the information processing unit 160. The paper thickness sensor 140 is positioned slightly downstream of the downstream sheet sensor 105 in the insertion direction of the sheet P, so that the paper thickness can be measured when the downstream sheet sensor 105 detects the sheet P.

[0044] As described above, the surface quality measuring unit 103 includes an optical sensor 1031 for detecting the surface quality of sheet P. The optical sensor 1031 comprises a light-emitting unit 132, an optical system, and a line sensor 133. The light-emitting unit 132 is, for example, an LED (Light Emitted Diode). The optical system is composed of a combination of lenses, mirrors, etc. The line sensor 133 is composed of multiple light-receiving elements arranged in a row. For example, the line sensor 133 is a CMOS line sensor equipped with a CMOS sensor as a light-receiving element.

[0045] As shown in Figure 6, the surface quality measurement unit 103 is equipped with a light-emitting unit 132 and a line sensor 133 on the upper block 109 side. The light-emitting unit 132 and the line sensor 133 are arranged side by side in a direction perpendicular to the insertion direction of the sheet P of the paper type identification device 100. For this reason, the line sensor 133 detects the surface of the sheet P by considering the direction perpendicular to the insertion direction of the sheet P as one line. The line sensor 133 is capable of detecting the paper surface area with a resolution corresponding to the pixel size and the imaging magnification of the optical system. One pixel corresponds to one light-receiving element. In this embodiment, a line sensor 133 with 400 pixels is provided. The surface quality measurement unit 103 has a paper surface detection resolution of 300 [dpi]. The scan (accumulation) time for one line is 500 microseconds.

[0046] The surface quality measuring unit 103 needs to hold the sheet P at the optical focal position. To this end, the biasing member 107 biases the sheet P toward the surface quality measuring unit 103, and the sheet holding member 106 stabilizes the orientation of the sheet P. As a result, when the surface quality measuring unit 103 detects the surface of the sheet P, variations in the position and orientation of the sheet P are reduced, allowing for stable detection of surface quality. The biasing member 107 is set to press the inserted sheet P toward the surface quality measuring unit 103 with a force of approximately 100 gf.

[0047] The light-emitting unit 132 of the surface quality measurement unit 103 is configured such that the irradiated light is incident on the surface of the sheet P at a shallow angle of 10 to 30 degrees. The light irradiated by the light-emitting unit 132 generates a shadow corresponding to the surface irregularities of the sheet P. The line sensor 133 reads this shadow. The line sensor 133 transmits an electrical signal representing the reading result (detection result) to the information processing unit 160. The light-receiving element is, for example, a photoelectric conversion element, and can output an electrical signal corresponding to the reflected light from the received sheet P. The information processing unit 160 performs calculations on the electrical signal (detection value) for each pixel (each light-receiving element) to obtain parameters for determining the surface quality of the sheet P, such as the degree of irregularity and reflectivity.

[0048] The surface property measurement unit 103 can detect information for one line area using the line sensor 133. To this end, the information processing unit 160 processes the area information according to the purpose and extracts parameters for determining the surface properties of the sheet P. Thus, the surface property measurement unit 103 of this embodiment excels at acquiring information corresponding to the physical properties of the sheet P. This makes it possible to accurately obtain the characteristics of the sheet P compared to reading point information using a single light-receiving element.

[0049] Figure 7 is a diagram showing the relationship between the surface properties of sheet P and the detection values ​​of the optical sensor 1031. Figure 7(a) shows the detection values ​​when sheet P, which has high smoothness and a smooth surface, is read by the line sensor 133. Figure 7(b) shows the detection values ​​when sheet P, which has low smoothness and large surface irregularities, such as embossed paper, is read by the line sensor 133. Figures 7(a) and (b) show graphs connecting the detection values ​​for each pixel of the line sensor 133 with lines. In the graph of Figure 7(a), because the surface irregularities of sheet P are small, the difference in density of the shadows caused by the irradiation of light from the light-emitting part 132 is small, and the change in the detection value for each pixel is small. In the graph of Figure 7(b), because sheet P has large surface irregularities, such as embossed paper, the difference in density of the shadows is large, and the change in the detection value for each pixel is large.

[0050] If the detected values ​​of each pixel are S1, S2...S400, then the difference integral value E is calculated as a parameter corresponding to the smoothness by summing the differences in the detected values ​​of adjacent pixels, as shown in Equation 1 below. (S2-S1)+(S3-S2)+(S4-S3)+(S5-S4)...+(S400-S399)=Integrated difference value E ...(Equation 1)

[0051] When reading a sheet P with high smoothness and a smooth surface, the difference between detected values ​​between adjacent pixels is small, so the cumulative difference value E is small. When reading a sheet P with high surface irregularities and low smoothness, the difference between detected values ​​between adjacent pixels is large, so the cumulative difference value E is large. In this way, a parameter representing the surface properties can be obtained according to the degree of surface irregularity of the sheet P.

[0052] The surface irregularities of sheet P vary from position to position within the plane of a single sheet P. Therefore, in order to accurately detect the degree of irregularity of a single sheet P, the optical sensor 1031 needs to read an area larger than a predetermined size. For example, when reading with sheet P stationary, the surface irregularities of sheet P can only be read in an area equivalent to one line of the line sensor 133 (84 μm in the insertion direction due to 300 dpi). In this case, the influence of local irregularities on sheet P becomes significant, and the deviation of the detected value for each reading position becomes large. Therefore, the cumulative difference value based on the detected value of one line becomes unsuitable for detecting surface properties.

[0053] In this embodiment, in order to read a predetermined area or larger of the surface of the sheet P, the optical sensor 1031 continuously reads a predetermined number of lines (in this case, several hundred lines) while the sheet P is moving as the user inserts the sheet P. This reading while the sheet P is moving is called "swift reading". By swift reading, a predetermined area of ​​the surface of the sheet P is read. Figure 8 is an explanatory diagram of the area read by swift reading. In order to obtain highly accurate detection values ​​by swift reading, the paper type identification device 100 of this embodiment is provided with an upstream sheet sensor 104 on the upstream side of the surface quality measurement unit 103 in the insertion direction of the sheet P, and a downstream sheet sensor 105 on the downstream side.

[0054] In Figure 8, as the user inserts the sheet P, the optical sensor 1031 reads a predetermined area of ​​the sheet P by a continuous reading while the sheet P moves. This allows for the acquisition of surface detection values ​​for a wide area of ​​the sheet P corresponding to its movement during insertion. At this time, the average of the differential integrated values ​​E for each line is used as the surface roughness detection value. The surface roughness detection value R is calculated by the following equation 2. The surface roughness detection value R reduces the influence of variations in surface roughness at each position within the sheet P's plane and becomes a parameter that stably corresponds to the physical properties of smoothness. In Figure 8, measurements are taken for 1600 lines from the time the user inserts the sheet P. (E1+E2+...EN) / N=R...(Formula 2) E: Sum of differences E1: Difference accumulation value of the first line N: Number of measurement lines R: Surface texture detection value

[0055] When a user manually inserts a sheet P, the speed at which the inserted sheet P moves is not constant. When the movement speed of the sheet P varies, the area of ​​the sheet P being read expands and contracts while reading one line, causing variations in the cumulative difference value E for one line. In particular, when the user starts inserting a sheet P into the paper type identification device 100, the retention of the sheet P near the entrance (near the groove 101) is unstable, and the insertion speed varies significantly, resulting in an unstable cumulative difference value E. Also, before the sheet P hits the innermost stopper 108, the resistance felt by the paper thickness sensor 140 as the paper passes through causes the movement speed of the sheet P to change. Furthermore, the cumulative difference value E for one line when the sheet P has hit the stopper 108 and stopped differs from when the sheet P is inserted smoothly because the width of the reading area is different from when the sheet P is inserted manually.

[0056] As a result, as shown in Figure 8, the reading area expands and contracts in the tip region where the tip of sheet P is located near the input, the region just before sheet P abuts against the abutment portion 108, and the rear end region where sheet P abuts against the abutment portion 108 and comes to a stop. For this reason, these regions are unsuitable for obtaining the differential integrated value E. In Figure 8, sections T1 and T2 represent these regions unsuitable for obtaining the differential integrated value E.

[0057] (First embodiment) In this embodiment, the differential cumulative value E is calculated using the values ​​detected by the line sensor 133 in the area read while the user smoothly inserts the sheet P manually. The information processing unit 160 determines the area where the movement speed (insertion speed) of the sheet P is most stable, based on the timing at which the upstream sheet sensor 104 and the downstream sheet sensor 105 detect the sheet P. The information processing unit 160 determines this area as the area for calculating the differential cumulative value E. In Figure 8, section A is the area suitable for obtaining such a differential cumulative value E. Figure 9 is a timing chart for determining the area suitable for obtaining such a differential cumulative value E.

[0058] The timing for starting reading by the optical sensor 1031 is determined based on the detection of sheet P by the upstream sheet sensor 104. The optical sensor 1031 starts reading after a time corresponding to interval T1 has elapsed since the upstream sheet sensor 104 detected sheet P. The time corresponding to interval T1 is determined by the shape of the paper type identification device 100. The time corresponding to interval T1 is determined based on repeated insertion tests of sheet P and the time considered optimal for the differential cumulative value E to stabilize. The optical sensor 1031 reads sheet P based on an accumulation time of 500 microseconds per line.

[0059] When the user inserts the sheet P, the leading edge of the sheet P reaches the detection position of the downstream sheet sensor 105, and the downstream sheet sensor 105 detects the sheet P, the optical sensor 1031 ends reading the sheet P. At this time, the information processing unit 160 processes the detection value for one line every 500 microseconds for each pixel, converts it into a differential integrated value E, and stores it sequentially in the internal memory for each line. In this case, the differential integrated value E for each line for 1400 lines is stored. The number of lines stored (1400 lines in this case) varies depending on the user's insertion speed of the sheet P. Since the number of lines stored depends on the user's insertion speed of the sheet P, the number of lines stored changes each time automatic paper type identification is performed.

[0060] The detected value obtained by reading section A, where the user can insert sheet P at the closest possible constant speed, is optimal for calculating the differential integrated value E. To this end, the surface quality of a single sheet P is determined by excluding the detected values ​​of the number of lines corresponding to section T2 from the timing D when the downstream sheet sensor 105 detects sheet P. The time corresponding to section T2 is determined by repeatedly performing sheet P insertion tests and based on the time when the insertion speed of sheet P becomes unstable near the abutment section 108.

[0061] Figure 10 is an example diagram of the memory space of the information processing unit 160 and the data stored at each address in the memory. When reading of sheet P begins, the information processing unit 160 sequentially acquires detection values ​​from the line sensor 133 and calculates a differential integrated value E for each line. The information processing unit 160 sequentially stores the calculated differential integrated value E for each line in its internal memory. The insertion speed of sheet P is unstable before passing the detection position of the downstream sheet sensor 105. The number of lines corresponding to the time period corresponding to section T2, which corresponds to this section B where the insertion speed is unstable, is 400 lines. The information processing unit 160 does not use the rear 400 lines out of the 1400 detected lines, and uses the average value of the differential integrated value E for the front 1000 lines as the surface texture detection value of sheet P.

[0062] In other words, when the information processing unit 160 stores the differential integrated value E for 1400 lines, it excludes the data (differential integrated value E) from addresses 1001 to 1400 and uses the data (differential integrated value E) from addresses 1 to 1000 to calculate the surface roughness detection value R. In reality, the number of stored lines varies depending on the user's insertion speed. Therefore, the data (differential integrated value E) obtained by excluding the data (differential integrated value E) up to 400 lines back from the address of the last stored line is used to calculate the surface roughness detection value R. The surface roughness detection value R is calculated, for example, by the following formula. E[1]+E[2]+...+E[N-400] / (N-400)=R ...(Equation 3) N: Number of storage lines R: Detected value of uneven surface

[0063] The memory data area can store, for example, 10,000 data points. If more data (differential cumulative value E) is attempted to be stored, the information processing unit 160 determines that this data is invalid and prompts the user to reinsert sheet P. For example, if the upstream sheet sensor 104 detects sheet P and the downstream sheet sensor 105 does not detect sheet P, the information processing unit 160 determines that the data is invalid. The information processing unit 160 sends an instruction to the user to reinsert sheet P to the control unit 400 of the image forming apparatus 201. In response to this instruction, the control unit 400 displays an instruction to reinsert sheet P on the display of the operation unit 502. In this way, the information processing unit 160 prompts the user to reinsert sheet P.

[0064] By the method described above, the surface properties (unevenness information) of the sheet P manually inserted by the user can be detected with high accuracy using the optical sensor 1031. By reading a predetermined area of ​​the sheet P with the optical sensor 1031, it is possible to capture the surface characteristics even of sheets P with deep unevenness on the surface, such as embossed paper. The paper type identification device 100 performs a skimming scan to grasp the overall surface trend of the sheet P, and is capable of identifying a wide variety of sheets, including embossed paper, and can handle many types of paper.

[0065] Figure 11 is a flowchart showing the parameter acquisition process for identifying the paper type of sheet P. Figure 12 is an example of the selection screen for the paper type identification process of sheet P. The selection screen is displayed on the display of the operation unit 502. The selection screen includes a "Manual Sheet Selection" button for the user to manually input the type of sheet P, and an "Automatic Sheet Identification" button for the paper type identification device 100 to automatically select a candidate for the type of sheet P. In this embodiment, the user selects the "Automatic Sheet Identification" button from the selection screen using the operation unit 502, and the selection is input to the control unit 400.

[0066] When the control unit 400 receives information from the operation unit 502 indicating that the "Automatic Sheet Identification" button has been selected, the operation mode is set to the automatic sheet identification mode for sheet P (S1). Once set to automatic identification mode, the control unit 400 notifies the information processing unit 160 of the paper type identification device 100 that it has switched to the automatic sheet identification mode for sheet P by instructing it to measure sheet P (S2).

[0067] The information processing unit 160 initializes the mechanical property measurement unit 102 and the surface property measurement unit 103 in preparation for inserting the sheet P (S3). When the user starts inserting the sheet P into the groove 101 (S4), the information processing unit 160 waits until the upstream sheet sensor 104 detects the sheet P (S5:N). When the upstream sheet sensor 104 detects the sheet P (S5:Y), the information processing unit 160 starts measuring the surface properties of the sheet P using the surface property measurement unit 103 (optical sensor 1031) after a time corresponding to section T1 has elapsed (S6). The information processing unit 160 causes the optical sensor 1031 to read the sheet P and sequentially acquires the reading results (detected values). The information processing unit 160 sequentially converts the detected values ​​into differential integrated values ​​E for each line and stores them in the memory within the information processing unit 160. This memory is, for example, RAM (Random Access Memory). The information processing unit 160 calculates the brightness, which is the sum of the data for each pixel, based on the reading results (detected values) from the optical sensor 1031, and stores it in memory. In this way, the differential integrated value E and brightness for each line are accumulated in the memory of the information processing unit 160 through surface measurement.

[0068] The information processing unit 160 starts measuring the physical properties of sheet P using the mechanical property measurement unit 102 (S7). The information processing unit 160 measures the ultrasonic transmittance of sheet P using the ultrasonic sensor 141, converts the measured value into basis weight information, and stores the basis weight information in memory. Figure 13 is an explanatory diagram of the relationship between ultrasonic transmittance and basis weight. The information processing unit 160 maintains a conversion formula or conversion table that shows the relationship between ultrasonic transmittance and basis weight. The information processing unit 160 converts the measured value into basis weight using such a conversion formula or conversion table. In this way, the basis weight of sheet P is stored in the memory of the information processing unit 160 by measuring the physical properties.

[0069] The information processing unit 160 measures the elapsed time since the upstream sheet sensor 104 detected sheet P. If the elapsed time since the upstream sheet sensor 104 detected sheet P exceeds a predetermined time (S8:N), and the downstream sheet sensor 105 has not detected sheet P, the information processing unit 160 determines that the information stored in memory during that time is invalid data. In this case, the information processing unit 160 returns to the process in S4 and instructs the user to reinsert sheet P. In addition, the differential cumulative value E, brightness, and basis weight for each line stored in the memory of the information processing unit 160 are deleted.

[0070] If the elapsed time since the upstream sheet sensor 104 detected sheet P is within a predetermined time (S8:N), the information processing unit 160 checks whether the downstream sheet sensor 105 has detected sheet P (S9). The downstream sheet sensor 105 detects sheet P when it is inserted to the innermost abutment portion 108. If the downstream sheet sensor 105 has not detected sheet P (S9:N), the information processing unit 160 returns to the process in S8. In other words, the information processing unit 160 decides whether or not to delete the data stored in memory depending on whether or not the downstream sheet sensor 105 detects sheet P within a predetermined time after the upstream sheet sensor 104 detected sheet P. If the downstream sheet sensor 105 detects sheet P (S9:Y), the information processing unit 160 stops reading sheet P by the optical sensor 1031 of the surface quality measurement unit 103 (S10).

[0071] With the sheet P stationary, pressed against the abutment portion 108, the information processing unit 160 acquires a pulse signal, which is a measured value, from the paper thickness sensor 140. The information processing unit 160 measures the paper thickness of the sheet P based on the number of pulses acquired (S11). The paper thickness of the sheet P is stored in the memory of the information processing unit 160.

[0072] The information processing unit 160 calculates the surface texture detection value R from the reading results (differential cumulative value E) of all lines stored in memory (S12). The information processing unit 160 excludes data for a number of lines that are a predetermined time prior to the detection timing of the sheet P by the downstream sheet sensor 105, calculates the average of the differential cumulative value E of the remaining lines, and performs calculation processing to convert it into the surface texture detection value R. The information processing unit 160 transmits to the control unit 400 of the image forming apparatus 201, along with completion information indicating that the processing has been completed, parameters such as basis weight, brightness, paper thickness, and the calculated surface texture detection value R stored in memory (S13). These parameters are information for identifying the type of sheet P.

[0073] The control unit 400 identifies the type of sheet P based on parameters obtained from the information processing unit 160. Figure 14 is a flowchart representing the paper type identification process.

[0074] The control unit 400 classifies the sheet P based on the measurement results of the surface properties of the sheet P (S21). Figure 15 is an explanatory diagram of the surface property classification. In Figure 15, a matrix is ​​used as an index of surface properties, with the vertical axis representing the surface texture detection value R and the horizontal axis representing brightness. The surface properties of sheets P with distinctive characteristics are measured in advance and classified. The control unit 400 refers to the matrix according to the surface texture detection value and brightness obtained from the detection values ​​acquired by the optical sensor 1031 to identify the type of sheet P.

[0075] Even sheets of the same brand have variations in their characteristics, so it is necessary to set a threshold for identifying sheet P while allowing for these variations. To improve identification accuracy, it is preferable that the variation in the detection value of the optical sensor 1031 obtained by reading sheets P of the same brand be small. The surface texture detection value R detected when the insertion speed of sheet P is unstable during quick reading will have large variations due to the fluttering of sheet P when the user inserts it, and is therefore not suitable for improving identification accuracy. As mentioned above, the surface texture detection value R detected when the insertion speed of sheet P is stable will have small variations and is therefore suitable for improving identification accuracy.

[0076] Brightness is the cumulative value (brightness) of the detection values ​​of each pixel of the line sensor 133, and is a parameter that correlates with the reflectance (brightness) of the sheet P. For example, transparent films made of resin such as PET are measured as having low brightness because they reflect little light. Sheet P with a geometric uneven surface, such as embossed paper, has a large difference in brightness between adjacent pixels due to the unevenness, so the uneven surface quality detection value R is large. Recycled paper tends to be measured as having a rough surface because the grain direction is uneven and the pulp fibers become shorter after going through several recycling processes. Coated paper tends to have a small uneven surface quality detection value R because the unevenness appears less due to the coating layer on the surface.

[0077] In this way, the control unit 400 can classify the surface properties of sheet P from the detected values ​​(luminance information) of each pixel of the line sensor 133, and classify sheet P according to the sheet classification used in the image forming apparatus 201. The control unit 400 classifies the type of sheet P based on its surface properties by determining which classification in the matrix of Figure 15 the uneven surface property detection value R and brightness belong to.

[0078] The control unit 400 determines the type of sheet P by adding basis weight to the classification by surface properties (S22). By adding basis weight to the parameters for identifying the paper type, the control unit 400 can further classify and identify the sheet P. Furthermore, the control unit 400 improves the accuracy of estimation based on basis weight by using paper thickness (S23). Coated paper is made by coating the surface of medium-grade paper or the like with a coating made by mixing a white pigment such as clay (kaolin) or calcium carbonate with an adhesive (binder) such as starch. Because coated paper has a higher density than plain printing paper, which is mainly composed of pulp, the error in basis weight conversion using the ultrasonic transmission coefficient-basis weight conversion formula becomes larger. Therefore, by simultaneously using paper thickness as a parameter for identifying the paper type, the accuracy of sheet P identification is improved. In particular, adding paper thickness information is useful for identifying the brand of sheet P. Based on these parameters, the control unit 400 determines candidate paper types for sheet P (S24).

[0079] Figures 16 and 17 are illustrative diagrams of the paper selection screen after paper type identification. The paper selection screen is displayed on the display of the operation unit 502. The paper selection screen displays the candidate paper types determined in the S24 process. The user can select the type of sheet P to be used for printing from the candidate paper types determined in the S24 process using the paper selection screen.

[0080] The paper selection screen in Figure 16 displays the types of sheet settings that can be selected for each sheet category pre-set in the image forming apparatus 201. Due to variations in basis weight, sheet P may be classified into a sheet category different from its nominal basis weight. Therefore, the paper selection screen also displays categories close to the detected sheet category. In addition, the word "Recommended" is displayed for candidates that are estimated to be paper types. The paper selection screen in Figure 17 allows the selection of the sheet brand. Sheet settings are made by specifying the sheet brand. The user assigns the sheet setting to the paper feed stage by selecting a sheet from these lists of sheet categories and sheet brands using the operation unit 502. This ensures that the type of sheet P is accurately identified and printing under the correct operating conditions is possible.

[0081] Figures 18 and 19 are illustrative diagrams of the paper type database stored in the memory 401 of the image forming apparatus 201. As described above, the paper type database 402 includes information such as the physical properties of various types of sheets, parameters for optimal operating conditions during image formation, whether paper can be fed into the image forming apparatus 201, and the available paper feed slots. The paper type database 402 stores reference values ​​for surface properties and paper thickness measured by the paper type identification device 100, as shown in Figure 19, linked to the paper type information. The control unit 400 refers to these values, determines the candidate with the highest similarity, and displays the paper selection screen shown in Figures 16 and 17 on the display of the operation unit 502. This allows the user to easily set the sheet.

[0082] The sheet type is determined, which also determines the sheet classification. This allows the operating conditions of each component of the image forming apparatus 201 to be determined using the paper type database shown in Figure 18. As a result, the sheet settings are made accurately, and the image forming apparatus 201 can form an image on the sheet P with optimal quality.

[0083] In this embodiment, the paper type identification device 100 is equipped with an information processing unit 160 that processes the measurement results from the mechanical property measurement unit 102 and the surface property measurement unit 103 and transmits them to the control unit 400 of the image forming apparatus 201. However, the processing of these measurement results may also be performed directly by the control unit 400. In this case, the functions of the information processing unit 160 would be included in the control unit 400. Alternatively, the paper type identification device 100 would transmit the measurement results from the mechanical property measurement unit 102 and the surface property measurement unit 103 directly to the control unit 400.

[0084] In this embodiment, the image forming apparatus 201 is equipped with the paper type database 402, but the paper type identification device 100 may be equipped with the paper type database 402. In this case, the information processing unit 160 of the paper type identification device 100 will perform the task of identifying the brand name of the sheet P, which is performed by the control unit 400. Furthermore, although an example using the upstream sheet sensor 104 as a trigger has been described, it is also possible to use the downstream sheet sensor 105 as a trigger. In this case, surface quality measurement is performed when the sheet P is withdrawn from the paper type identification device 100. Instead of the downstream sheet sensor 105, the encoder rotation of the paper thickness sensor 140 may be detected, and the reading interval by the surface quality measurement unit 103 may be determined based on that timing.

[0085] The above describes an example in which the operating conditions (control parameters) of the image forming apparatus 201 are determined by selecting the sheet category and sheet brand from the features detected by the paper type identification device 100. The paper type identification device 100 may also be a paper physical property measuring device, and the control parameters may be determined directly from the measured sheet feature quantities (physical property values). In addition, the paper type database 402 and the control unit 400 may be located on the cloud. In that case, if the image forming apparatus 201 is connected to the cloud via a network, the latest paper type setting information and identification algorithm can always be selected.

[0086] (Second example) This section describes a method where the sheet P is pushed in to the innermost abutment 108, and then measurements are taken when the sheet is pulled out. This method is applied when the measurement results are more stable when the sheet is pulled out.

[0087] Figure 20 is a timing chart for when measurement is performed when sheet P is withdrawn. Since sheet P has already been inserted to the innermost stopper 108, the upstream sheet sensor 104 and the downstream sheet sensor 105 are in a state of detecting sheet P. When the user withdraws sheet P from this state, the paper type identification device 100 starts reading sheet P with the optical sensor 1031 after a time period corresponding to a predetermined interval T1, starting from timing A, when the detection result of the downstream sheet sensor 105 changes. After the user has finished withdrawing sheet P, the detection result of the upstream sheet sensor 104 changes. At this timing D, the paper type identification device 100 stops reading sheet P with the optical sensor 1031.

[0088] If the region where the measurement results are stable is section Y, then in a predetermined section Z just before the end of sheet P extraction, the sheet P extraction speed is unstable. For this reason, the data acquired in section Z must be excluded from the determination of the paper type of sheet P. When calculating the surface texture detection value, the data stored in memory is processed to average the difference accumulated values ​​between sections Y, excluding the lines corresponding to section Z (400 lines in this case), and the surface texture detection value is calculated.

[0089] As described above, in this embodiment, the paper type identification device 100 uses an information processing unit 160 to select measurement results from the surface properties measuring unit 103, which measures surface properties while the sheet P is moving, based on the detection results of the sheet P by the upstream sheet sensor 104 and the downstream sheet sensor 105. For example, the measurement results from the surface properties measuring unit 103 are selected based on the detection results of the upstream sheet sensor 104 and the downstream sheet sensor 105, which change at a slower timing. The detection result that changes at a slower timing is selected if it was acquired more than a predetermined time before the timing of the change, and the detection result acquired after the predetermined time is excluded. The information processing unit 160 calculates parameters representing surface properties based on the selected measurement results from the surface properties measuring unit 103. For this purpose, measurement results taken at times when the insertion speed of the sheet P is unstable are removed when calculating the parameters. As a result, the parameters representing surface properties are calculated with high accuracy, and the type of sheet P can be identified with high accuracy. Because the type of sheet P can be identified with high accuracy, the image forming apparatus 201 can appropriately determine the operating conditions during image formation.

Claims

1. A paper type identification device having, in an insertion / removal direction in which a sheet is inserted or removed, one end of which is an opening through which a sheet is inserted and the other end of which is an abutment portion against which the sheet abuts, A reading sensor that reads the surface of the sheet; and a control means for causing the reading sensor to read the reading area of ​​the sheet while the sheet is moving, and for determining the type of the sheet by using a second reading result obtained by excluding a first reading result read within a predetermined period from the reading timing at which the sheet was last read from the reading result read by the reading sensor. Paper type identification device.

2. A first detection unit that detects the presence or absence of a sheet; A second detection unit that detects the presence or absence of a sheet, When the abutting portion is viewed from the opening in the insertion / removal direction, the first detection portion, the reading sensor, and the second detection portion are arranged in this order. The paper type identification device according to claim 1.

3. When the surface of the sheet is read by the reading sensor when the sheet is inserted into the opening, the timing at which the sheet is last read is the timing at which the second detection unit detects the presence of the sheet. The paper type identification device according to claim 2.

4. When the surface of the sheet is read by the reading sensor when the sheet is pulled out from the opening, the timing at which the sheet is last read is the timing at which the first detection unit detects that the sheet is not present. The paper type identification device according to claim 2.

5. A third detection unit is provided which has a displacement member that contacts the sheet downstream of the reading position of the reading sensor in the insertion / removal direction and whose displacement amount changes depending on the thickness of the sheet, and detects the displacement amount of the displacement member; the displacement member has a lever whose angle changes when pressed by the sheet, and when the sheet is inserted, the displacement member is pressed by the sheet to change the angle, The third detection unit is configured to detect an amount of displacement of an angle of the lever. The paper type identification device according to claim 1.

6. The control means determines a plurality of candidates for the type of the sheet using the second reading result, The control means controls a predetermined display unit to display a plurality of candidates for the sheet type. The paper type identification device according to claim 1.

7. A third detection unit is provided which has a displacement member that contacts the sheet downstream of the reading position of the reading sensor in the insertion / removal direction and whose displacement amount changes depending on the thickness of the sheet, and detects the displacement amount of the displacement member; The control means determines the type of the sheet based on the second reading result and the thickness of the sheet. The paper type identification device according to claim 1.

8. A method for detecting a basis weight of a sheet, comprising: a basis weight sensor provided in a sheet conveying path and configured to detect a basis weight of the sheet; The control means determines the type of the sheet based on the second reading result and the detection result of the basis weight sensor. The paper type identification device according to claim 1.

9. A third detection unit that has a displacement member that contacts the sheet downstream of the reading position of the reading sensor in the insertion / removal direction and whose displacement amount changes depending on the thickness of the sheet, and detects the displacement amount of the displacement member; A basis weight sensor is provided in a sheet conveying path and detects the basis weight of the sheet, The control means determines the type of the sheet based on the second reading result, the thickness of the sheet, and the detection result of the basis weight sensor. The paper type identification device according to claim 1.

10. An image forming apparatus for forming an image on a sheet based on image forming conditions, comprising: A paper type identification device according to claim 1, The image forming conditions are controlled based on the type of sheet identified by the paper type identification device. Image forming device.

Images