Paper detection device, image forming device

Abstract

To provide a paper detection device that suppresses an effect of temperature change on a measurement result of a media sensor.SOLUTION: A paper detection device includes a media sensor 100 that measures paper, and a power supply voltage control unit 170 that controls a supply of power supply voltage to the media sensor 100. When the power supply voltage control unit 170 receives a notification indicating that a mode for measuring paper is to be set, the power supply voltage control unit 170 starts supplying power supply voltage to the media sensor 100.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a paper detection device equipped with a media sensor for determining the type (paper grade) of paper, and to an image forming apparatus equipped with such a paper detection device. [Background technology]

[0002] Image forming devices such as copiers, printers, and multifunction devices are able to use a wider variety of paper. For example, image forming devices can print images on various types of paper, such as paper of various thicknesses and stiffness, and synthetic paper using resin instead of pulp as a raw material. Generally, electrophotographic image forming devices print images on paper through the processes of charging, exposing, developing, transferring, and fixing. The optimal operating conditions (image forming conditions) for each process vary depending on the physical properties (stiffness, basis weight, surface properties, etc.) of the paper to be printed. For this reason, image forming devices need to execute printing processes under image forming conditions appropriate for the paper.

[0003] The paper type is often set manually by the user, for example. However, manual setting may result in an inaccurate setting of the paper type due to operational errors or other reasons. In this case, printing may not be performed under appropriate image formation conditions, and a normal image may not be formed. Patent Document 1 discloses an image forming device that automatically determines the paper type using a media sensor and forms an image. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2009-29622 A Summary of the Invention [Problem to be solved by the invention]

[0005] When determining the type of paper, the media sensor measures the physical properties of the paper as characteristic quantities. The measurement results by the media sensor have temperature characteristics. In other words, the measurement results of the media sensor fluctuate due to temperature changes in the media sensor itself. This leads to a decrease in the accuracy of determining the type of paper, making it difficult to set appropriate image formation conditions. In view of the above-mentioned problems, the main object of the present invention is to provide a paper detection device that suppresses the effects of temperature changes on the measurement results of the media sensor. [Means for solving the problem]

[0006] The paper detection device of the present invention comprises a measuring means for measuring paper and a power supply voltage control means for controlling the supply of power supply voltage to the measuring means, and is characterized in that the power supply voltage control means starts supplying the power supply voltage to the measuring means when it receives a notification indicating that a mode for measuring paper is set. Another paper detection device of the present invention comprises a transport means for transporting paper, a measurement means for measuring the paper transported by the transport means, a detection means for detecting the paper transported by the transport means, and a power supply voltage control means for controlling the supply of power supply voltage to the measurement means, wherein the power supply voltage control means starts supplying the power supply voltage to the measurement means when the detection means detects the paper. Another paper detection device of the present invention comprises a measuring means for measuring paper and a power supply voltage control means for controlling the supply of power supply voltage to the measuring means, and is characterized in that the power supply voltage control means starts supplying the power supply voltage to the measuring means when it receives an instruction to start a job. Effect of the Invention

[0007] According to the present invention, the effect of temperature changes on the measurement results of the media sensor can be suppressed, and the accuracy of determining the type of paper is improved. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image forming apparatus. [Diagram 2](a) and (b) are enlarged views of the fixing unit. [Diagram 3] FIG. [Figure 4] FIG. 4 is a diagram illustrating the configuration of a media sensor. [Diagram 5] FIG. 4 is a diagram illustrating the configuration of a media sensor. [Figure 6] 5 is a graph showing temperature characteristics of an output value of an ultrasonic sensor. [Figure 7] 4 is a flowchart showing an image forming process. [Figure 8] FIG. 4 is a graph showing the relationship between transmittance and basis weight. [Figure 9] Paper type classification table. [Figure 10] Paper type classification table. [Figure 11] Paper type classification table. [Figure 12] FIG. 13 is a diagram showing an example of a setting screen for an automatic detection mode. [Figure 13] FIG. [Figure 14] 4 is a flowchart showing an image forming process. [Figure 15] 4 is a flowchart showing an image forming process. [Figure 16] 4 is a flowchart showing an image forming process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, "basis weight" refers to the mass per unit area of ​​a sheet and is expressed in units of [gsm].

[0010] (Image forming device) 1 is a configuration diagram of an image forming apparatus according to this embodiment. The image forming apparatus 201 according to this embodiment is a tandem type intermediate transfer type laser beam printer that utilizes an electrophotographic process. The image forming apparatus 201 prints and outputs a full-color or monochrome image on a recording medium, that is, paper S, based on image data acquired via a network from an external device such as a personal computer, or image data acquired from an image reading device 202 provided on the upper portion.

[0011] The image forming apparatus 201 has components for forming an image inside a main body 201A, and is provided with an image reading device 202 and an operation unit 502 on the upper part of the main body 201A. Between the main body 201A and the image reading device 202 of the image forming apparatus 201, a discharge space D is provided having a stacking unit 223 onto which paper S after image formation is discharged.

[0012] The image reading device 202 is a scanner that reads an image from an original and generates image data. The image reading device 202 is used, for example, during copying of an original. The image reading device 202 of this embodiment is configured as a part of the image forming device 201. However, the image reading device 202 may be configured to be electrically connected to the image forming device 201 as a device separate from the image forming device 201.

[0013] The operation unit 502 is a user interface having 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. A user can input various instructions to the image forming apparatus 201 through the operation unit 502. The image forming apparatus 201 notifies the user of various information by displaying various screens on the display of the operation unit 502. The operation unit 502 of this embodiment is configured as a part of the image forming apparatus 201. However, the operation unit 502 may be electrically connected to the image forming apparatus 201 as a device different from the image forming apparatus 201.

[0014] The image forming apparatus 201 includes, in a main body 201A, an image forming section 201B, an intermediate transfer section 201C, a secondary transfer section 201D, a fixing device 201E, and a cassette paper feed section 230. The main body 201 is also provided with a manual paper feed section 235.

[0015] The cassette paper feed section 230 feeds the paper S from a paper feed cassette 1 that stores the paper S. The cassette paper feed section 230 includes a pickup roller 2 and a separation section that includes a feed roller 3 and a retard roller 4 for separating the paper S sent out from the pickup roller 2. The paper S is fed one sheet at a time from the paper feed cassette 1 by the pickup roller 2 and the separation section. In this embodiment, a configuration in which a plurality of cassette paper feed sections 230 (four in this example) are provided will be described, but the number of cassette paper feed sections 230 may be any number. The paper S fed from the cassette paper feed section 230 is transported to the registration roller pair 240 via the transport roller pairs 280 and 290.

[0016] In addition to the cassette paper feed section 230, the paper S can also be fed from the manual paper feed section 235. The manual paper feed section 235 includes a manual tray 5 on which the user places the paper S. Like the cassette paper feed section 230, the manual paper feed section 235 includes a pickup roller and a separation section, and feeds the paper S from the manual tray 5 one sheet at a time. The paper S fed from the manual paper feed section 235 is also transported to the registration roller pair 240 via the transport roller pair 280, 290. The transport roller pair 280, 290 are rotating members for transporting the paper S.

[0017] A media sensor 100 for measuring a characteristic amount of the paper S is provided on the conveying path between the conveying roller pair 280 and the conveying roller pair 290. The conveying roller pair 280 is provided upstream of the media sensor 100 in the conveying direction of the paper S, and the conveying roller pair 290 is provided downstream of the media sensor 100 in the conveying direction of the paper S. The media sensor 100 outputs information corresponding to the basis weight (basis weight information) and information corresponding to the surface property (surface property information) as characteristic amounts of the paper S conveyed from the cassette paper feed unit 230 or the manual paper feed unit 235. The media sensor 100 may be configured to be provided at least one of a position where the paper S fed from the cassette paper feed unit 230 can be measured and a position where the paper S fed from the manual paper feed unit 235 can be measured, or both. The configuration of the media sensor 100 will be described in detail later.

[0018] The image forming unit 201B is a four-drum full-color type, 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 disposed above the process cartridge 211. The toner cartridge 215 supplies toner to the developer 214.

[0019] The intermediate transfer unit 201C includes an intermediate transfer belt 216 wound around a drive roller 216a and a tension roller 216b. Four primary transfer rollers 219 are provided on the inner side of the intermediate transfer belt 216, and contact the intermediate transfer belt 216 at positions facing the respective photosensitive drums 212. The intermediate transfer belt 216 is rotated in the direction of the arrow by a drive roller 216a driven by a drive unit (not shown).

[0020] The secondary transfer section 201D includes a secondary transfer roller 217 disposed opposite the drive roller 216a with the intermediate transfer belt 216 interposed therebetween. The fixing device 201E is disposed downstream of the secondary transfer roller 217 in the transport direction of the paper S, and includes a pressure roller 220a and a heating roller 220b. A first discharge roller pair 225a, a second discharge roller pair 225b, and a double-sided reversing section 201F are disposed downstream of the fixing device 201E in the transport direction of the paper S. The double-sided reversing section 201F includes a reversible roller pair 222 and a re-transport path R that transports the paper S having an image formed on one side thereof to the image forming section 201B.

[0021] The image forming apparatus 201 configured as above operates as follows. The image forming apparatus 201 acquires image data from the image reading apparatus 202 or an external device together with an instruction to start a print job, and forms an image on the paper S according to the image data. At this time, the image forming apparatus 201 performs each step of the image formation under image formation conditions according to the characteristics of the paper S. Note that a print job refers to a series of operations from conveying the paper S and forming an image based on a print signal instructing image formation on the paper S, to discharging the paper S onto the stacking unit 223 after the image formation operation is completed. The image forming apparatus 201 acquires an instruction to start a print job from the operation unit 502 or an external device.

[0022] In the image forming unit 201B, the surface of the photosensitive drum 212 is uniformly charged to a potential of a predetermined polarity by the charger 213. The laser scanner 210 irradiates the uniformly charged surface of the photosensitive drum 212 with laser light modulated based on image data. As a result, an electrostatic latent image corresponding to the corresponding color (yellow, magenta, cyan, black) is formed on the surface of each photosensitive drum 212.

[0023] The image forming unit 201B develops the electrostatic latent image formed on the photosensitive drum 212 by the developing unit 214. On each photosensitive drum 212, the electrostatic latent image is developed with toner of the corresponding color, thereby forming a toner image of the corresponding color. The toner images are transferred in sequence from the photosensitive drum 212 to the rotating intermediate transfer belt 216 in a superimposed state by the primary transfer roller 219. As a result, a full-color toner image is formed on the intermediate transfer belt 216. The intermediate transfer belt 216 conveys the toner image to the secondary transfer unit 201D by rotating.

[0024] In parallel with such a toner image forming operation, the paper S is conveyed one sheet at a time to the pair of registration rollers 240 by the cassette paper feeder 230 or the manual paper feeder 235. Before the paper S reaches the pair of registration rollers 240, the media sensor 100 measures the characteristic amount of the paper S. The image forming apparatus 201 sets the image forming conditions based on the measured characteristic amount, and performs subsequent image formation based on the set image forming conditions. The set image forming conditions are, for example, the voltage value of the secondary transfer bias applied to the secondary transfer roller 217 when the toner image is transferred to the paper S, the fixing temperature when the image is fixed by the fixing device 201E, the conveying speed of the paper S during fixing, and the like.

[0025] The pair of registration rollers 240 corrects skew of the conveyed paper S. After the skew correction, the paper S is conveyed to the secondary transfer unit 201D by the pair of registration rollers 240 in accordance with the timing at which the toner image carried by the intermediate transfer belt 216 is conveyed 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 paper S by a secondary transfer bias applied to the secondary transfer roller 217.

[0026] The paper S onto which the toner image has been transferred is transported to the fixing device 201E. The fixing device 201E sandwiches and transports the paper S with a roller nip formed by the pressure roller 220a and the heating roller 220b. When sandwiching and transporting the paper S, the fixing device 201E heats the paper S with the heating roller 220b, thereby melting and mixing the toners of the various colors on the paper S. The fixing device 201E also fixes the melted and mixed toners to the paper S by applying pressure to the paper S with the pressure roller 220a. At this time, the adhesive force of the melted toner causes the paper S to stick to the heating roller 220b.

[0027] 2 is an enlarged view of the fixing unit 201E. If the stiffness (rigidity) of the paper S is weak, the paper S may be taken up by the rotating heating roller 220b due to the adhesion force generated in the paper S to the heating roller 220b (FIG. 2(b)). For this reason, a separation plate 221 for separating the paper S is provided downstream of the heating roller 220b in the conveying direction of the paper S (FIG. 2(a)).

[0028] The image forming apparatus 201 may determine the state of the separation plate 221 according to the type and basis weight of the paper S determined from the measurement results of the media sensor 100. For example, when forming an image on a type of paper S with low stiffness, the separation plate 221 is arranged so that its leading edge comes into contact with the surface of the heating roller 220b as shown in FIG. 2(a), and separates the paper S from the heating roller 220b. When forming an image on a type of paper S with high stiffness, the paper S is not taken up by the heating roller 220b. For this reason, the separation plate 221 is arranged so that its leading edge does not come into contact with the surface of the heating roller 220b. This makes it possible to prevent the surface of the heating roller 220b from being worn down by the separation plate 221.

[0029] The paper S with the fixed image is discharged to the discharge space D by either the first discharge roller pair 225a or the second discharge roller pair 225b. The paper S is stacked on a stacking section 223 provided to protrude from the bottom surface of the discharge space D. When images are formed on both sides of the paper S, the paper S with the image fixed on one side is transported to a re-conveyance path R by the reversing roller pair 222 and transported again to the image forming section 201B where an image is formed on the inverted side. The re-conveyance path R is configured to transport the paper S to a transport path between the transport roller pair 290 and the registration roller pair 240.

[0030] Image formation conditions (conveyance speed during fixing, target fixing temperature, transfer voltage during secondary transfer, etc.) vary depending on the physical properties (basis weight, stiffness, surface properties, material, etc.) of the paper S on which the image is formed. Therefore, when forming an image, it is necessary to set image formation conditions in advance according to the characteristics of the paper S to be used.

[0031] Depending on the type of paper S, restrictions may be placed on the way it can be set in the paper feed slot (paper feed cassette 1, manual feed tray 5). For example, some types of thick paper with high stiffness can only be fed from the manual feed tray 5, where the curvature of the transport path is small. Coated paper, which has a smooth surface and strong adhesion between sheets, needs to be fed one sheet at a time from the manual feed tray 5 to prevent multiple sheets from being fed overlapping. Paper made from pulp generally has different bending stiffness depending on the length and width due to the bias in the orientation direction (grain direction) of the pulp fibers that occurs due to manufacturing reasons. Therefore, there are some types of paper that have recommended length and width directions when being set in the paper feed slot so that the bending stiffness against the bending of the transport path is low. In addition, for single-sided coated paper, which is coated only on one side of plain paper, the top and bottom directions are specified when setting the paper, in order to print on the coated side.

[0032] There are some types of paper that cannot be used in the image forming apparatus 201. For example, thick paper with too high stiffness may stop being conveyed due to the resistance when conveyed along a curved conveying path. Thin paper with too low stiffness may be strongly influenced by the adhesive force between the molten toner and the heating roller 220b when passing through the fixing device 201E, and may not be able to be peeled off from the heating roller 220b by the separation plate 221 and may wind up as it is (FIG. 2(b)). Synthetic paper made of synthetic resin instead of pulp as a raw material may melt when heated by the fixing device 201E, and may contaminate the heating roller 220b.

[0033] From the above, in order to perform appropriate image formation, it is important to identify the type of paper S from the characteristic amounts of the paper S to be used before image formation. For this reason, the media sensor 100 needs to measure the characteristic amounts of the paper S before the paper S is transported to the secondary transfer unit 201D.

[0034] (Control unit) 3 is an explanatory diagram of a controller that controls the operation of such an image forming apparatus 201. The controller 200 is an information processing apparatus equipped with, for example, a CPU (Central Processing Unit). The controller 200 may be realized by an MPU (Micro Processor Unit) or an ASIC (Application Specific Integrated Circuit), etc. The controller 200 controls the image forming operation (printing operation) by the image forming apparatus 201.

[0035] The controller 200 includes a control unit 400 and a memory 401. The memory 401 stores a control program for the image forming operation, initial values ​​of various setting values, various data necessary for the image forming operation, and the like. The memory 401 also has a storage area for storing a paper type database 402. The paper type database 402 is a database in which correspondence between paper characteristics, paper types, and image forming conditions is set in advance. The control unit 400 is connected to an operation unit 502, a host device 501 which is an external device, and a media sensor 100.

[0036] The host device 501 is a personal computer, an image scanner, a facsimile, etc. The operation unit 502 inputs instructions, settings, etc. received via an input interface to the control unit 400. The operation unit 502 outputs various information via an output interface under the control of the control unit 400. As described above, the operation unit 502 has a display as an output interface, and displays various information on the display.

[0037] The control unit 400 starts a print job by receiving an instruction to start the print job from the host device 501 or the operation unit 502. The control unit 400 receives image data from the host device 501 or the image reading device 202, and processes the received image data. The control unit 400 causes the image forming unit 201B to form a toner image based on the image data after the image processing, and feeds the paper S, thereby executing the print job.

[0038] The media sensor 100 includes an information processing unit 160, a power supply voltage control unit 170, an ultrasonic sensor 120, and an optical sensor 150. In this embodiment, the ultrasonic sensor 120 and the optical sensor 150 form a paper measurement unit. In addition to the ultrasonic sensor 120 and the optical sensor 150, a paper detection sensor 270 is connected to the information processing unit 160. The information processing unit 160 is an information processing device realized by, for example, a CPU, an MPU, or an ASIC. The information processing unit 160 controls the measurement operation of the media sensor 100 and processes the measurement results.

[0039] The operation of the media sensor 100 is controlled by an information processing unit 160, and the measurement results of the ultrasonic sensor 120 and the optical sensor 150 are processed by the information processing unit 160. The information processing unit 160 operates under the control of the control unit 400, and transmits the feature amounts of the paper S obtained from the measurement results of the ultrasonic sensor 120 and the optical sensor 150 to the control unit 400.

[0040] The control unit 400 determines the paper type and sets image forming conditions according to the paper type based on the measurement results (feature values ​​of the paper) of the media sensor 100 processed by the information processing unit 160. The image forming conditions (conveying speed during fixing, target fixing temperature, transfer voltage during secondary transfer, etc.) vary depending on the physical properties (basis weight, stiffness, surface properties, material, etc.) of the paper S on which the image is formed. Therefore, when forming an image, it is necessary to set image forming conditions in advance according to the feature values ​​of the paper S to be used.

[0041] The paper detection sensor 270 is a sensor for detecting the paper S transported to the measurement position of the media sensor 100. When the paper detection sensor 270 detects the paper, the information processing unit 160 starts a measurement process of the characteristic amounts of the paper S by the paper measurement unit (ultrasonic sensor 120 and optical sensor 150).

[0042] The ultrasonic sensor 120 measures the paper S with ultrasonic waves and outputs a predetermined voltage value as the measurement result. The information processing unit 160 acquires the output value of the ultrasonic sensor 120 and derives the transmittance of the paper S from the output value when the paper S is present and the output value when the paper S is not present. The information processing unit 160 detects basis weight information from the transmittance of the paper S. The optical sensor 150 is, for example, a contact image sensor (CIS). The information processing unit 160 stores the luminance value of each pixel as the imaging result by the optical sensor 150. The information processing unit 160 converts the stored luminance value of each pixel into surface property information such as a difference integrated value obtained by integrating the difference between the luminance values ​​of adjacent pixels and a brightness integrated value obtained by integrating the luminance values ​​of each pixel.

[0043] The information processing unit 160 transmits the basis weight information and the surface property information to the control unit 400. The control unit 400 determines the paper type and basis weight of the paper S based on the acquired basis weight information and surface property information. The control unit 400 determines the paper type of the paper S based on a plurality of pieces of information stored in a paper type database 402, and determines the image forming conditions (e.g., secondary transfer bias value, target fixing temperature of the fixing unit 201E, conveying speed during fixing, etc.) corresponding to the paper type and basis weight. The control unit 400 displays the determined image forming conditions on the display of the operation unit 502. The control unit 400 also controls the image forming operation under the determined image forming conditions.

[0044] The power supply voltage control unit 170 is connected to the control unit 400. The power supply voltage control unit 170 controls the supply of power supply voltage for operating the media sensor 100 based on a command signal obtained from the control unit 400. In this embodiment, the power supply voltage control unit 170 controls the supply of power supply voltage to the ultrasonic sensor 120.

[0045] (Media sensor configuration) Figures 4 and 5 are explanatory diagrams of the configuration of the media sensor 100. Figure 4 is a diagram of the media sensor 100 as viewed from a direction perpendicular to the transport direction of the paper S. Figure 5 is a diagram of the media sensor 100 as viewed from the upstream side in the transport direction of the paper S.

[0046] 4, media sensor 100 is provided between conveying roller pair 280 and conveying roller pair 290, and acquires characteristic quantities (basis weight information and surface property information) of conveyed paper S. Paper detection sensor 270 is disposed upstream of media sensor 100 in the conveying direction of paper S (on the conveying roller pair 280 side).

[0047] 5, in the media sensor 100, an ultrasonic sensor 120 and an optical sensor 150 are arranged at the same position in the transport direction of the paper S, side by side in a direction perpendicular to the transport direction. The ultrasonic sensor 120 is composed of an ultrasonic transmitter 130 and an ultrasonic receiver 131. The optical sensor 150 is a CIS having a light source 1501 (e.g., an LED) and a line sensor 1502. The optical sensor 150 may be composed of a CCD image sensor or a CMOS image sensor.

[0048] The optical sensor 150 measures the luminance value of the received light in order to measure the surface properties of the paper S. For this reason, the paper S needs to be held at the optical focal position of the optical sensor 150. When measuring the paper S, the ultrasonic sensor 120 can improve the measurement accuracy if it is not affected by the flapping of the paper S being transported. For this reason, the paper S needs to be transported with a stable posture.

[0049] In this embodiment, in order to stabilize the posture of the paper S while transporting it, the paper pressure roller 260 and the paper pressure roller 261 are provided between the transport roller pair 280 and the transport roller pair 290. The paper pressure roller 260 and the paper pressure roller 261 are arranged at the same position in the transport direction of the paper S. The paper pressure roller 260 is arranged facing the optical sensor 150 across the transport path. The paper pressure rollers 260 and 261 are configured to move between a first position separated from the media sensor 100 and a second position close to the media sensor 100. Figures 4 and 5 exemplify a state in which the paper pressure rollers 260 and 261 are arranged at the second position. The paper pressure rollers 260 and 261 are configured to press the paper S toward the media sensor 100 (optical sensor 150) by being arranged at the second position.

[0050] The paper pressure rollers 260 and 261 are disposed at the second position and pressed against the paper S whose transport has been stopped. The paper S is pressed against the media sensor 100 by the paper pressure rollers 260 and 261. In other words, the paper pressure rollers 260 and 261 are pressing members that press the paper S to abut against the media sensor 100. The paper S abuts against the media sensor 100, reducing variation in position and posture. This allows the media sensor 100 to measure the characteristics of the paper S, such as the surface property and basis weight, in a stable state. The paper pressure rollers 260 and 261 move to the second position to press the paper S only when measuring the paper S, and retreat to the first position when not measuring. This allows the paper S to be transported to the measurement position without being impeded by the media sensor 100 (ultrasonic sensor 120 and optical sensor 150) entering the measurement position.

[0051] If the paper pressure rollers 260, 261 are placed in the second position without stopping the transport of the paper S, the paper S may flutter during transport, causing the paper S to skew or jam. It is important that the longitudinal direction of the line sensor 1502 is perpendicular to the transport direction of the paper S. For this reason, the paper pressure rollers 260, 261 are pressed against the stopped paper S, enabling stable measurement of the feature amounts. The control unit 400 resumes the transport of the paper S with the attitude of the paper S stabilized, and at the same time instructs the information processing unit 160 to measure the feature amounts of the paper S using the media sensor 100. In response to this instruction, the information processing unit 160 starts measuring the feature amounts of the paper S using the media sensor 100.

[0052] (Basis weight measurement) 5, the ultrasonic sensor 120 has an ultrasonic transmitter 130 and an ultrasonic receiver 131 disposed at opposing positions across the transport path. The ultrasonic transmitter 130 is provided on the upper block 110 side of the media sensor 100. The ultrasonic receiver 131 is provided on the lower block 109 side of the media sensor 100. The ultrasonic sensor 120 receives ultrasonic waves output from the ultrasonic transmitter 130 by the ultrasonic receiver 131 via the transport path of the paper S. The ultrasonic receiver 131 outputs information (output value) for determining the basis weight of the paper S based on the received ultrasonic waves.

[0053] Both the ultrasonic transmitter 130 and the ultrasonic receiver 131 are composed of a piezoelectric element (also called a piezo element), which is an element for converting mechanical displacement into an electric signal, and an electrode terminal. When a pulse voltage of a predetermined frequency is input to the electrode terminal of the ultrasonic transmitter 130, the piezoelectric element oscillates and generates an ultrasonic wave. The generated ultrasonic wave propagates through the air. When the ultrasonic wave reaches the paper S, the paper S vibrates due to the ultrasonic wave. The ultrasonic wave generated by the ultrasonic transmitter 130 propagates through the paper S to the ultrasonic receiver 131. The piezoelectric element of the ultrasonic receiver 131 generates an output voltage at the electrode terminal according to the amplitude of the received ultrasonic wave. The output voltage has a voltage value according to the basis weight of the paper S. The output voltage is transmitted to the information processing unit 160 as an output value.

[0054] The amplitude of ultrasonic waves is attenuated when paper S is present compared to when no ultrasonic waves are present. Therefore, the output value (output voltage) output from ultrasonic receiver 131 differs depending on whether paper S is present or not. The ratio of the output voltage when no paper S is present between ultrasonic transmitter 130 and ultrasonic receiver 131 to the output voltage when paper S is present is the transmittance. The transmittance of ultrasonic waves changes depending on the basis weight (areal density) of paper S. Therefore, the basis weight of paper S can be estimated by using a conversion formula or conversion table between transmittance and basis weight. In this manner, the basis weight of paper S is measured by ultrasonic sensor 120.

[0055] (Surface quality measurement) The surface properties of the paper S are measured using an optical sensor 150. Light emitted from a light source 1501 is irradiated onto the paper S at a certain angle by a light guide (not shown). The paper S reflects the irradiated light. The light reflected by the paper S is imaged on the light receiving surface of a line sensor 1502 via a lens (not shown). In this way, the line sensor 1502 can read the light reflected from the paper S as an image.

[0056] The line sensor 1502 is configured with a plurality of light receiving elements arranged in a direction perpendicular to the transport direction of the paper S, and can read one line of image at a time in the direction perpendicular to the transport direction. In this embodiment, the line sensor 1502 can read an image of 400 pixels at a time.

[0057] In this embodiment, multiple light receiving elements are arranged so that the line sensor 1502 can read an image at a resolution of 300 dpi. The amount of information in a one-line image read by the line sensor 1502 at one time is insufficient to determine the surface properties of the paper S. This is because the deviation in the reading results for each reading position is large in a one-line image. For this reason, the optical sensor 150 performs multiple reading operations on the transported paper S to obtain the reading results of the image of multiple lines of the paper S. By stitching together the reading results for the multiple lines in the transport direction of the paper S, it becomes possible to determine the tendency of the surface properties of a specified area of ​​the paper S.

[0058] (Media sensor self-heating) When the image forming apparatus 201 is started up, a power supply voltage is supplied to each component to make it operable. When the image forming apparatus 201 is started up, the application of the power supply voltage to the media sensor 100 also begins, making it operable. When the power supply voltage is applied to the media sensor 100, its own temperature rises. The rise in temperature affects the output value (output voltage), and can cause different output values ​​to be output even when measuring the same type of paper, for example. This phenomenon is particularly noticeable with the ultrasonic sensor 120.

[0059] 6 is a graph showing the temperature characteristics of the output value of the ultrasonic sensor 120. As is clear from this graph, the rate of change of the output value of the ultrasonic sensor 120 increases as the time (elapsed time) that the power supply voltage is applied to the ultrasonic sensor 120 increases. In particular, the rate of change fluctuates greatly during the first hour after the start of application of the power supply voltage. When the power supply voltage is applied to the ultrasonic sensor 120, the ultrasonic sensor 120 generates heat and its own temperature rises. In this way, the rise in temperature of the media sensor 100 affects the measurement results and makes it difficult to accurately measure the characteristic amounts of the paper S. If the characteristic amounts are not measured accurately, it becomes difficult to accurately determine the type of paper S, which affects the setting of appropriate image formation conditions.

[0060] For this reason, in this embodiment, a configuration is described in which the effect of temperature rise is suppressed to measure the characteristic quantities of the paper S, the type of the paper S is accurately determined, and appropriate image forming conditions are set. FIG. 7 is a flowchart showing the image forming process including the process of determining the type of the paper S in this embodiment. The control unit 400 and the information processing unit 160 perform this process in cooperation. In this embodiment, in the initial state when the image forming apparatus 201 is started up, no power supply voltage is supplied to the ultrasonic sensor 120.

[0061] The control unit 400 waits until it receives an instruction to start a print job from the operation unit 502 or the host device 501 (S101: N). When the control unit 400 receives an instruction to start a print job (S101: Y), it determines whether or not an automatic detection mode for the type of paper S is set (S102). Setting the automatic detection mode will be described later.

[0062] If the automatic detection mode is set (S102: Y), the control unit 400 transmits a command signal to the power supply voltage control unit 170 to instruct the supply of power supply voltage to the ultrasonic sensor 120, and applies the power supply voltage to the ultrasonic sensor 120 (S103). The application of the power supply voltage activates the ultrasonic sensor 120. The control unit 400 transmits a command to the information processing unit 160 to cause the ultrasonic sensor 120 to perform ultrasonic measurement in a state in which no paper S is present (S104). The information processing unit 160 stores the measurement result (output value) of the ultrasonic sensor 120 in a state in which no paper S is present in an internal memory.

[0063] The control unit 400 starts conveying the paper S (S105). The control unit 400 waits until the paper detection sensor 270 detects the paper S (S106: N). If the paper detection sensor 270 detects the paper S (S106: Y), the control unit 400 continues conveying the paper S and waits until a predetermined time has elapsed (S107). The predetermined time is the time that elapses from when the leading edge of the paper S is detected by the paper detection sensor 270 until it is pinched by the pair of conveying rollers 290. By waiting for the predetermined time, the paper S is conveyed to the measurement position of the media sensor 100.

[0064] After a predetermined time has elapsed, the control unit 400 transmits an instruction to the information processing unit 160 to perform a measurement process of the characteristic quantities of the paper S using the media sensor 100. As a result, the information processing unit 160 causes the ultrasonic sensor 120 to perform ultrasonic measurement in the presence of the paper S, and stores the measurement result (output value) in the internal memory (S108). When the measurement process of the ultrasonic sensor 120 is completed, the control unit 400 transmits a command signal to the power supply voltage control unit 170 to stop the supply of the power supply voltage to the ultrasonic sensor 120, and stops the application of the power supply voltage to the ultrasonic sensor 120 (S109). As a result, the ultrasonic sensor 120 stops operating. Next, the information processing unit 160 causes the optical sensor 150 to perform a measurement process of the paper S, and stores the measurement result (brightness value) in the internal memory (S110).

[0065] The information processing unit 160 obtains the transmittance from the measurement results when the sheet S is present and when it is not present, measured by the ultrasonic sensor 120, and converts the transmittance into basis weight (S111). FIG. 8 is an explanatory diagram of the relationship between transmittance and basis weight. The conversion of transmittance into basis weight is performed using a conversion formula or conversion table that expresses such a relationship. The information processing unit 160 determines the surface property of the sheet S from the luminance value of the sheet S measured by the optical sensor 150, and generates surface property information that expresses the surface property (S112). The surface property information includes, for example, a difference integrated value and a brightness integrated value. The information processing unit 160 transmits the basis weight information and surface property information that express the basis weight obtained in this manner to the control unit 400.

[0066] The control unit 400 determines the type of the paper S based on the basis weight information and surface property information acquired from the information processing unit 160, and forms an image on the paper S under image formation conditions according to the type of the paper S (S113). FIG. 9 is a classification table of paper types based on differential integrated value and brightness integrated value. FIG. 9 is a matrix in which the differential integrated value is on the vertical axis and the brightness integrated value is on the horizontal axis, and the paper surface property is measured in advance and the paper type is classified by machine learning. The threshold values ​​for classifying the paper type are a0 to a3 for the brightness integrated value and b0 to b4 for the differential integrated value. These threshold values ​​are stored in the paper type database 402 of the memory 401. The control unit 400 determines the paper type by comparing the surface property information with each threshold value.

[0067] 10 is a classification table of paper types according to basis weight. The paper type is determined based on which basis weight range the basis weight measured by the media sensor 100 falls within. Threshold values ​​indicating the basis weight ranges are indicated by C1 to C23 and are stored in a paper type database 402 in memory 401.

[0068] The control unit 400 determines the paper type based on the basis weight information acquired from the media sensor 100 and the basis weight range of the classification table shown in Fig. 10 of the paper type determined based on the surface property information and the classification table of Fig. 9. The control unit 400 determines the image formation conditions according to the determined paper type. Fig. 11 is a paper type classification table that combines the classification tables of Fig. 9 and Fig. 10. Such a classification table may be stored in a paper type database 402 in the memory 401, and the control unit 400 may determine the image formation conditions using such a classification table.

[0069] If the automatic detection mode is not set (S102: N), the control unit 400 forms an image on the paper S under image formation conditions according to the type of paper S set by the user (S114). As described above, the image forming apparatus 201 automatically determines the type of paper S when the automatic detection mode is set, determines the image formation conditions based on the determination result, and forms an image. After the start of conveyance of the paper S, a power supply voltage is applied to the ultrasonic sensor 120 before measurement of the paper S begins, and application of the power supply voltage is terminated after the measurement is completed. This suppresses the effect of temperature rise on the measurement result.

[0070] 12 is a diagram showing an example of a setting screen for the automatic detection mode. This setting screen is displayed on the display of the operation unit 502. On this setting screen, the type and basis weight of the paper contained in each paper feed cassette 1 and the paper placed on the manual feed tray 5 can be set. The names of each paper feed cassette 1 and the manual feed tray 5 are displayed in a display area 701. The type and basis weight of the paper contained in each paper feed cassette 1 and the paper placed on the manual feed tray 5 are displayed in a display area 702. The top of the display area 701 shows the manual feed tray 5, and below that the four paper feed cassettes 1 (cassettes 1, 2, 3, 4) are shown.

[0071] Regardless of which paper feed slot (manual feed tray 5, each paper feed cassette 1) the paper type and basis weight can be automatically determined by using media sensor 100. To use this automatic determination function, an automatic detection button 703 is displayed on the setting screen. When setting the automatic detection mode, the user selects (presses) the automatic detection button 703 via the input interface of operation unit 502. Pressing the automatic detection button 703 switches between setting and not setting the automatic detection mode.

[0072] When the control unit 400 receives a notification from the operation unit 502 indicating that the automatic detection mode is to be set, the control unit 400 stores the fact that the automatic detection mode is set in the memory 401. The memory 401 has, for example, a flag indicating the setting state of the automatic detection mode, and the state of this flag is changed by pressing an automatic detection button 703. Note that the setting screen for the automatic detection mode may be displayed on the host device 501. In this case, the automatic detection mode is set by an input device provided in the host device 501.

[0073] In the image forming apparatus 201 configured as described above, the power supply voltage is applied at the timing when the ultrasonic sensor 120 measures the paper S, so that the temperature rise of the ultrasonic sensor 120 during measurement can be suppressed. As a result, the effect of temperature changes on the measurement results of the ultrasonic sensor 120 is suppressed, the accuracy of distinguishing the type of paper S is improved, and appropriate image forming conditions are set.

[0074] (Variation 1) Fig. 13 is a diagram showing a modified example of the controller in Fig. 3. The difference from Fig. 3 is that the power supply voltage control unit 170 controls the application of power supply voltage to the ultrasonic receiver 131, rather than to the entire ultrasonic sensor 120. Fluctuations in the measurement result (output value) of the ultrasonic sensor 120 are significantly affected by temperature changes in the ultrasonic receiver 131 that outputs the output value. For this reason, by adjusting the supply of power supply voltage to the ultrasonic receiver 131, it is possible to suppress fluctuations in the output value.

[0075] Fig. 14 is a flowchart showing the image forming process including the process of determining the type of paper S in this case. The only difference from the flowchart in Fig. 7 is that the target for controlling the supply of power supply voltage in the processes of S203 and S209 is the ultrasonic receiver 131, and the other processes are the same. In this case as well, the power supply voltage is applied to the ultrasonic sensor 120 only when measuring the paper S, so that the effect of temperature changes on the measurement results of the ultrasonic sensor 120 is suppressed, the accuracy of determining the type of paper S is improved, and appropriate image forming conditions are set.

[0076] (Variation 2) 7, the application of the power supply voltage to the ultrasonic sensor 120 is stopped immediately after the measurement is completed. However, if the temperature of the media sensor 100 has dropped sufficiently by the time the next measurement is started and the temperature no longer has any effect on the measurement result, there is no need to stop the application of the power supply voltage.

[0077] FIG. 15 is a flowchart showing the image forming process including the process of determining the type of the paper S in this case. The process is the same as the flowchart in FIG. 7 up to the measurement process by the ultrasonic sensor 120 in S308. In FIG. 15, when the measurement process by the ultrasonic sensor 120 is completed, the processes of measurement by the optical sensor 150, basis weight determination, surface property determination, and image formation are performed (S309 to S312) similarly to the processes of S110 to S113 in FIG. 7. Thereafter, the control unit 400 transmits a command signal to the power supply voltage control unit 170 to stop the supply of the power supply voltage to the ultrasonic sensor 120, and stops the application of the power supply voltage to the ultrasonic sensor 120 (S113). This causes the ultrasonic sensor 120 to stop operating. After stopping the ultrasonic sensor 120, the control unit 400 outputs the paper S (printed matter) on which the image has been formed to the discharge space D (S315).

[0078] In this way, in Modification 2, the supply of power supply voltage to the ultrasonic sensor 120 is stopped before the printed material is discharged. If the supply of power supply voltage to the ultrasonic sensor 120 is stopped before the paper S is discharged, the temperature of the ultrasonic sensor 120 has dropped sufficiently so as not to affect the measurement results, even if the next print job requires the type of paper S to be determined immediately. This reduces the effect of temperature changes on the measurement results of the ultrasonic sensor 120, improves the accuracy of determining the type of paper S, and sets appropriate image formation conditions.

[0079] (Variation 3) In the process of Fig. 7, the ultrasonic sensor 120 is applied with a power supply voltage before the process of S104 in order to perform ultrasonic measurements in the processes of S104 and S108, and the application of the power supply voltage ends after the process of S108. The ultrasonic sensor 120 only needs to be applied with a power supply voltage at the timing of each ultrasonic process. Fig. 16 is a flowchart showing the image forming process including the process of determining the type of paper S in this case. The process is the same as the flowchart of Fig. 7 up to the measurement process by the ultrasonic sensor 120 in S404 in the absence of paper S.

[0080] When the measurement process by the ultrasonic sensor 120 without the paper S is completed, the control unit 400 transmits a command signal to the power supply voltage control unit 170 to stop the supply of power supply voltage to the ultrasonic sensor 120, and stops the application of the power supply voltage to the ultrasonic sensor 120 (S405). This causes the ultrasonic sensor 120 to stop operating. The control unit 400 starts conveying the paper S, similar to the processes of S105 to S107 in FIG. 7, and when the paper detection sensor 270 detects the paper S, it waits until a predetermined time has passed (S406 to S408).

[0081] When a predetermined time has elapsed, the control unit 400 transmits a command signal to the power supply voltage control unit 170 to instruct the supply of power supply voltage to the ultrasonic sensor 120, causing the ultrasonic sensor 120 to apply the power supply voltage (S409). The application of the power supply voltage activates the ultrasonic sensor 120. After the ultrasonic sensor 120 is activated, the control unit 400 transmits an instruction to the information processing unit 160 to perform measurement processing of the characteristic amounts of the paper S using the media sensor 100. As a result, the information processing unit 160 causes the ultrasonic sensor 120 to perform ultrasonic measurement in the presence of the paper S, and stores the measurement results (output values) in internal memory (S410).

[0082] When the measurement process of the ultrasonic sensor 120 is completed, the control unit 400 transmits a command signal to the power supply voltage control unit 170 to stop the supply of power supply voltage to the ultrasonic sensor 120, and stops the application of the power supply voltage to the ultrasonic sensor 120 (S411). This causes the ultrasonic sensor 120 to stop operating. Thereafter, the control unit 400 performs each process of measurement by the optical sensor 150, basis weight determination, surface property determination, and image formation, similar to the processes of S110 to S114 in FIG. 7 (S412 to S416).

[0083] In this way, in Modification 3, the ultrasonic sensor 120 is supplied with a power supply voltage at the timing of performing a measurement. That is, the power supply voltage is applied to the ultrasonic sensor 120 before the start of a measurement in a state where no paper S is present, and the application of the power supply voltage is terminated after the measurement is completed, and the power supply voltage is applied to the ultrasonic sensor 120 before the start of a measurement in a state where paper S is present, and the application of the power supply voltage is terminated after the measurement is completed. This reduces the effect of temperature changes on the measurement results of the ultrasonic sensor 120, improves the accuracy of identifying the type of paper S, and sets appropriate image formation conditions.

[0084] Although the above describes a case where the temperature change of the ultrasonic sensor 120 is handled, the same processing may be performed for all sensors of the media sensor 100. This embodiment is effective for any sensor in which heat generation due to application of a power supply voltage affects the measurement result. Also, the second and third modifications may be configured to control the application of a power supply voltage to the ultrasonic receiver 131, as in the first modification.

[0085] In the above description, the media sensor 100 is provided inside the image forming apparatus 201, but it may be provided outside the image forming apparatus 201 as long as it is upstream of the secondary transfer unit 201D in the paper transport direction. Furthermore, the processing by the information processing unit 160 in the media sensor 100 may be performed by the control unit 400. Conversely, the processing performed by the control unit 400 may be performed by the information processing unit 160. In this case, the paper type database 402 may be stored in a memory accessible from the information processing unit 160. In any case, the control unit 400 and the information processing unit 160 may cooperate to perform the above processing.

[0086] Furthermore, the image forming apparatus 201 determines control parameters such as image forming conditions by detecting the type and basis weight of the paper S from the characteristic quantities of the paper S measured by the media sensor 100, but the control parameters may be determined directly from the characteristic quantities. The media sensor 100 may be another paper physical property measuring device.

[0087] The media sensor 100 described above is one example, and is not limited to a configuration including the optical sensor 150 and the ultrasonic sensor 120, and may be equipped with another sensor capable of measuring the characteristic quantities of the paper S. Furthermore, the media sensor 100 may be configured to include either the optical sensor 150 or the ultrasonic sensor 120.

[0088] Although the configuration of the image forming apparatus 201 has been described above, the present invention is applicable to any apparatus having a paper detection device including the media sensor 100 and the controller 200. For example, such a paper detection device can also be used in an image reading device that reads an image printed on a sheet of paper while transporting the sheet of paper. The image reading device includes an automatic document feeder (ADF). By incorporating the paper detection device in the ADF, stable image reading and paper transport become possible.

Claims

1. A measuring means for measuring the paper; a power supply voltage control means for controlling the supply of a power supply voltage to the measuring means; the power supply voltage control means starts supplying the power supply voltage to the measurement means when a notification is received indicating that a mode for measuring paper is set. Paper detection device.

2. A conveying means for conveying the paper; a detection unit that detects the paper being transported by the transport unit, the power supply voltage control means supplies the power supply voltage to the measurement means in response to the detection of the paper by the detection means; The measuring means measures the paper conveyed by the conveying means.

2. The paper detection device according to claim 1.

3. the power supply voltage control means stops supplying the power supply voltage to the measurement means when the measurement means finishes measuring the paper.

3. The paper detection device according to claim 2.

4. The printer further includes a conveying means for conveying the paper, the measuring means performs a first measurement while the paper is not being transported by the transport means, and performs a second measurement while the paper is being transported by the transport means; the power supply voltage control means supplies the power supply voltage to the measurement means before the start of the first measurement, and stops supplying the power supply voltage to the measurement means after the end of the second measurement.

2. The paper detection device according to claim 1.

5. the power supply voltage control means supplies the power supply voltage to the measurement means before the start of the first measurement, stops the supply of the power supply voltage to the measurement means after the end of the first measurement, supplies the power supply voltage to the measurement means before the start of the second measurement, and stops the supply of the power supply voltage to the measurement means after the end of the second measurement.

5. The paper detection device according to claim 4.

6. The sheet conveying device further includes a detection unit that detects the sheet conveyed by the conveying unit, the power supply voltage control means supplies the power supply voltage to the measurement means before the start of the second measurement, when the detection means detects the paper.

6. The paper detection device according to claim 5.

7. The measuring means is an ultrasonic sensor.

6. The paper detection device according to claim 4 or 5.

8. The ultrasonic sensor includes an ultrasonic transmitter that outputs ultrasonic waves, and an ultrasonic receiver that receives the ultrasonic waves output from the ultrasonic transmitter and outputs an output value according to the received ultrasonic waves, The power supply voltage control means controls the power supply voltage supplied to the ultrasonic receiver.

8. The paper detection device according to claim 7.

9. A conveying means for conveying paper; a measuring means for measuring the paper conveyed by the conveying means; a detection means for detecting the paper conveyed by the conveying means; a power supply voltage control means for controlling the supply of a power supply voltage to the measuring means; The power supply voltage control means starts supplying the power supply voltage to the measuring means when the detection means detects the paper. Paper detection device.

10. A measuring means for measuring the paper; a power supply voltage control means for controlling the supply of a power supply voltage to the measuring means; the power supply voltage control means starts supplying the power supply voltage to the measurement means when a job start instruction is received. Paper detection device.

11. A paper detection device according to claim 1, 9 or 10; an image forming means for forming an image on the paper under image forming conditions based on the measurement result of the paper by the measurement means; and a discharge space into which the paper on which the image is formed is discharged. Image forming device.

12. the power supply voltage control means stops supplying the power supply voltage to the measuring means before the paper on which the image is formed is discharged to the discharge space. The image forming apparatus according to claim 11.

13. the power supply voltage control means supplies the power supply voltage to the measurement means when a print job start instruction is received. The image forming apparatus according to claim 11.

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