Image forming device

Abstract

To provide an image forming device capable of being controlled according to a state of a media sensor.SOLUTION: An image forming device 201A comprises a manual sheet feeding part 235 on which sheets are stacked, a media sensor 100 for measuring a feature amount of a sheet fed by the manual sheet feeding part 235, sheet pressing rollers (260 and 261) disposed to face the media sensor 100, a roller attaching / detaching part 250 for moving the sheet pressing rollers (260 and 261), and a system control part 401 for prohibiting the sheet feed from being done by the manual sheet feeding part 235 when the sheet pressing rollers (260 and 261) cannot be moved due to a failure of the roller attaching / detaching part 250.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an image forming apparatus equipped with a paper type identification device capable of acquiring physical property values ​​of paper. [Background technology]

[0002] Some image forming apparatuses are equipped with a media sensor as a paper type identification device for identifying the type of paper, which is the recording medium on which an image is printed. The media sensor measures feature quantities that represent the physical properties of the paper using a detection device such as an optical sensor or an ultrasonic sensor. The feature quantities are, for example, physical property values ​​such as the paper's basis weight and surface properties. The image forming apparatus identifies the type of paper based on the measurement results from the media sensor and pre-registered paper information including physical property values ​​for each paper type. Image formation conditions are set according to the identified paper type.

[0003] Paper may experience positional fluctuations (fluttering) in the surface direction during transport. Paper fluttering affects the measurement of physical properties by the optical sensor and can reduce the accuracy of paper type identification. Patent Document 1 proposes a configuration in which rollers are placed across the paper transport path to press the paper against the media sensor. By pressing the paper against the light receiving surface of the optical sensor with the rollers, paper fluttering during transport is suppressed, preventing a decrease in the accuracy of paper type identification. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2018-200478 Summary of the Invention [Problem to be solved by the invention]

[0005] If a malfunction occurs in the media sensor, it is necessary to control the image forming apparatus according to the state of the media sensor. In view of the above-mentioned problems, the main object of the present invention is to control the image forming apparatus according to the state of the media sensor. [Means for solving the problem]

[0006] The image forming apparatus of the present invention comprises a loading means for loading paper, an image forming means for forming an image on the paper fed from the loading means, a measuring means arranged on one side of a transport path along which the paper is transported from the loading means to the image forming means and for measuring the characteristics of the paper, an opposing member arranged on the other side opposite the measuring means via the transport path, a moving means for moving the opposing member to a first position and a second position, and a control means for controlling the moving means, wherein the first position is a position where the paper is clamped and transported at a nip portion between the measuring means and the opposing member, and the second position is a position where the distance between the measuring means and the opposing member is farther than the first position, and the control means prohibits the paper from being fed from the loading means when the moving means is unable to move the opposing member to the first position and the second position. [Effects of the Invention]

[0007] According to the present invention, it is possible to control the image forming apparatus in accordance with the state of the media sensor. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating the configuration of an image forming system. [Figure 2] FIG. [Figure 3] FIG. 2 is a diagram illustrating the configuration of a media sensor 100. [Figure 4] 2A and 2B are diagrams illustrating the configuration of a media sensor 100. [Figure 5] (a) and (b) are explanatory diagrams of the paper type database. [Figure 6]10(a) and 10(b) are explanatory diagrams of a line sensor. [Figure 7] FIG. 4 is an explanatory diagram of a mechanism for suppressing positional fluctuations between an optical sensor and a sheet. [Figure 8] 10A and 10B are explanatory diagrams of data calculation pixel regions. [Figure 9] 10 is a flowchart showing a paper type determination process. [Figure 10] 10 is a flowchart showing a paper measurement process. [Figure 11] 10 is a flowchart showing a paper type determination process. [Figure 12] 10 is a flowchart showing a paper measurement process. [Figure 13] 10A and 10B are diagrams illustrating abnormality determination by an optical sensor. [Figure 14] 10 is a flowchart showing a media sensor abnormality determination process. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

[0010] 1 is a diagram showing the configuration of an image forming system having a paper type identification device according to this embodiment. The image forming system 201 according to this embodiment uses the paper type identification device to identify the paper type, prompts the user to select a print mode, and then forms an image under the optimal image formation conditions for the identified paper type. The image formation conditions include, for example, secondary transfer voltage, fixing temperature, and fixing speed.

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

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

[0013] The operation unit 502 is a user interface that includes an input interface and an output interface. The input interface is, for example, various key buttons, a touch panel, etc. The output interface is, for example, a display, a speaker, etc. A user can input various instructions to the image forming system 201 using the operation unit 502. The image forming system 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 system 201. However, the operation unit 502 may also be electrically connected to the image forming system 201 as a device separate from the image forming system 201.

[0014] The image forming apparatus 201A of this embodiment is a tandem-intermediate transfer laser beam printer that uses electrophotography, but the image forming method is not limited to this as long as it is equipped with a paper type identification device. The image forming apparatus 201A internally includes an image forming unit 201B, an intermediate transfer unit 201C, a secondary transfer unit 201D, a fixing unit 201E, and a cassette paper feed unit 230. The image forming apparatus 201A is also provided with a manual paper feed unit 235.

[0015] The cassette paper feed unit 230 feeds paper S from a paper feed cassette 1 that stores paper S. The cassette paper feed unit 230 includes a pickup roller 2 and a separation unit 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 unit. In this embodiment, a configuration in which multiple cassette paper feed units 230 (four in this example) are provided is described, but the number of cassette paper feed units 230 may be any number. The paper S fed from the cassette paper feed unit 230 is transported to a pair of registration rollers 240.

[0016] In addition to cassette paper feed unit 230, paper sheets S can also be fed from manual paper feed unit 235. Manual paper feed unit 235 includes a manual tray 5 on which a user loads paper sheets S. Like cassette paper feed unit 230, manual paper feed unit 235 includes a pickup roller and a separator, and feeds paper sheets S one sheet at a time from manual tray 5. Paper sheets S fed from manual paper feed unit 235 are transported to registration roller pair 240 via transport roller pair 280, 290. Transport roller pair 280, 290 are provided on the transport path for paper sheets fed from manual paper feed unit 235, before the transport path for paper sheets fed from cassette paper feed unit 230 and the transport path for paper sheets fed from manual paper feed unit 235 join.

[0017] A media sensor 100 is provided on the transport path between the transport roller pair 280 and the transport roller pair 290 as a paper type identification device for measuring characteristic quantities of the paper S. The media sensor 100 measures the physical property values ​​of the paper S as characteristic quantities of the paper S fed from the manual paper feed unit 235. In this embodiment, the measured physical property values ​​of the paper S include basis weight and surface properties. The media sensor 100 outputs basis weight data and surface properties data that represent the measured basis weight and surface properties. The media sensor 100 is provided at a position on the transport path where transport defects are unlikely to occur, and is not provided at a position where the transport capacity is low. For example, the media sensor is not provided in a portion of the transport path with a large curvature. The configuration of the media sensor 100 will be described in detail below.

[0018] Image forming unit 201B is a four-drum full-color system and includes a laser scanner 210 and four process cartridges 211 for forming 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 developing unit 214. A toner cartridge 215 is disposed above the process cartridge 211. The toner cartridge 215 supplies toner to the developing unit 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 inside 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] Secondary transfer unit 201D includes a secondary transfer roller 217 located opposite drive roller 216a with intermediate transfer belt 216 sandwiched therebetween. Fixing unit 201E is located downstream of secondary transfer roller 217 in the transport direction of sheet S, and includes pressure roller 220a and heating roller 220b. Downstream of fixation unit 201E in the transport direction of sheet S are arranged first discharge roller pair 225a, second discharge roller pair 225b, and duplex reversing unit 201F. Duplex reversing unit 201F includes a reversing roller pair 222 that can rotate forward and backward, and a re-conveying path R that transports sheet S with an image formed on one side to image forming unit 201B.

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

[0022] In the image forming unit 201B, the charger 213 uniformly charges the surface of the photosensitive drum 212 to a potential of a predetermined polarity. 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, or black) is formed on the surface of each photosensitive drum 212.

[0023] Image forming unit 201B develops the electrostatic latent images formed on photosensitive drums 212 by developing devices 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 sequentially transferred by primary transfer rollers 219 from the photosensitive drums 212 to the rotating intermediate transfer belt 216 in a superimposed state. As a result, a full-color toner image is formed on the intermediate transfer belt 216. As the intermediate transfer belt 216 rotates, it transports the toner image to secondary transfer unit 201D.

[0024] In parallel with this toner image formation operation, paper sheets S are conveyed one by one to the pair of registration rollers 240 by the cassette paper feed unit 230 or the manual paper feed unit 235. The characteristic amounts of the paper sheets S fed from the manual paper feed unit 235 are measured by the media sensor 100 before they reach the pair of registration rollers 240. The image forming system 201 determines the type of paper sheet S based on the measured characteristic amounts and sets image forming conditions according to the determined type of paper sheet S. The image forming system 201 performs subsequent image formation based on the set image forming conditions. The image forming conditions set according to the type of paper sheet S include, for example, the secondary transfer voltage applied to the secondary transfer roller 217 when the toner image is transferred to the paper sheet S, the fixing temperature when the image is fixed by the fixing unit 201E, and the conveying speed (fixing speed) of the paper sheet S during fixing.

[0025] The pair of registration rollers 240 corrects skew of the conveyed sheet S. After the skew correction, the sheet 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 sheet S by a secondary transfer voltage applied to the secondary transfer roller 217.

[0026] The paper S onto which the toner image has been transferred is transported to the fuser 201E. The fuser 201E sandwiches and transports the paper S in a roller nip formed by the pressure roller 220a and the heating roller 220b. When sandwiching and transporting the paper S, the fuser 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 fuser 201E also applies pressure to the paper S with the pressure roller 220a, thereby fixing the melted and mixed toners to the paper S. In this way, an image is formed on the paper S. During the fixing process, the adhesive force of the melted toner causes the paper S to stick to the heating roller 220b.

[0027] In the case of single-sided printing, or in the case of double-sided printing with images formed on both sides, the sheet S is discharged from the fixing device 201E by the first discharge roller pair 225a or the second discharge roller pair 225b to the stacking section 223 in the discharge space D. In the case of double-sided printing with an image formed on one side, the sheet S with the image formed on one side is transported to the registration roller pair 240 via the double-sided reversing section 201F and the re-conveying path R, where the image is formed again. By passing the sheet S through the double-sided reversing section 201F, the printed side on which the image is formed is reversed.

[0028] (Type of paper used for image formation) Image formation conditions (secondary transfer voltage, fixing temperature, fixing speed, etc.) vary depending on the physical properties of the paper S on which the image is formed, such as basis weight, stiffness, surface properties, and material. Therefore, when printing, it is necessary to confirm the type of paper S to be used in advance. Also, image forming apparatus 201A may have restrictions on the type of paper that can be placed in the paper feed unit (cassette paper feed unit 230, manual paper feed unit 235).

[0029] For example, some types of thick paper with high stiffness can only be fed from the manual paper feed unit 235, where the curvature of the transport path is small. Coated paper, which has a smooth surface and strong adhesion between sheets of paper, must be fed one sheet at a time from the manual paper feed unit 235. Paper made from pulp generally has different bending stiffness depending on the length and width due to bias in the orientation direction of the pulp fibers (grain direction) that occurs during the manufacturing process. Therefore, some types of paper have a recommended length and width orientation when loaded into the paper feed unit so that bending stiffness against bending on the transport path is low. Unlike plain paper, single-sided coated paper, which is coated on only one side, requires a specified upside-down orientation when loaded, as printing is performed on the coated side.

[0030] Some types of paper cannot be used in image forming apparatus 201A. For example, thick paper with too much stiffness may stop due to the resistance when conveyed along a curved conveyance path. Thin paper with too little stiffness may be strongly affected by the adhesive force between molten toner and heating roller 220b when passing through fuser 201E, and may wind around heating roller 220b. Synthetic paper made from synthetic resin instead of pulp may melt when exposed to high heat in fuser 201E, contaminating heating roller 220b.

[0031] As described above, since there are paper types that are restricted or cannot be used with the image forming apparatus 201A, it is important to know the type of paper to be used before printing in order to perform printing appropriately.

[0032] (controller) 2 is an explanatory diagram of a controller that controls the operation of the image forming apparatus 201A. The image forming apparatus 201A is connected to a host device 501, and can receive print job start instructions and image data from the host device 501. The host device 501 is a personal computer, image scanner, facsimile machine, etc. The image forming apparatus 201A includes a media sensor 100, a device controller 300, and a system controller 400.

[0033] The system controller 400 includes a system control unit 401 and a memory 402. The memory 402 stores a paper type database 403. The system control unit 401 controls the overall operation of the image forming apparatus 201A. The system control unit 401 controls communication with a host device 501. The system control unit 401 controls communication with an operation unit 502, accepts instructions and the like from the operation unit 502, and displays images on a display of the operation unit 502. The system control unit 401 controls the operation of the media sensor 100 and the device controller 300.

[0034] The device controller 300 includes a device control unit 301, the cassette paper feed unit 230, the manual paper feed unit 235, the image forming unit 201B, the fixing unit 201E, etc. The device control unit 301 controls the image forming operation by controlling the operations of the cassette paper feed unit 230, the manual paper feed unit 235, the image forming unit 201B, the fixing unit 201E, etc. The device control unit 301 communicates with a system control unit 401 and controls the image forming operation in cooperation with the system control unit 401.

[0035] The media sensor 100 comprises a media sensor control unit 160, an ultrasonic sensor 120, an optical sensor 150, a roller attachment / detachment unit 250, and a memory 161. Under the control of a system control unit 401, the media sensor control unit 160 issues measurement instructions to the ultrasonic sensor 120 and the optical sensor 150 and processes the measurement results. The media sensor control unit 160 controls the attachment and detachment operation of the paper pressure roller, which will be described later, using the roller attachment / detachment unit 250.

[0036] The media sensor control unit 160 starts measuring the feature quantities of the paper S when it receives notification of the timing of paper arrival from the device control unit 301. Notification of the timing of paper arrival from the device control unit 301 to the media sensor control unit 160 is made via a communication interface such as serial communication, bus communication, wireless communication, or a hard signal. The device control unit 301 is equipped with a sensor that detects, for example, the start of paper feeding from the manual feed tray 5 and that paper S has been fed from the manual feed tray 5. The device control unit 301 notifies the media sensor 100 of the timing of paper arrival based on the detection result of this sensor.

[0037] After controlling the paper pressure rollers to the attached state, the media sensor control unit 160 measures the paper S using the ultrasonic sensor 120 and the optical sensor 150. The ultrasonic sensor 120 is used to measure the basis weight of the paper S using ultrasonic waves. The media sensor control unit 160 calculates the transmittance of the paper S based on the measurement results from the ultrasonic sensor 120 and stores the magnetic permeability as basis weight data in memory 161. The optical sensor 150 is used to measure the surface properties of the paper S using light. The media sensor control unit 160 stores surface property data representing the surface properties of the paper S (adjacent pixel difference integrated value, brightness value, PP (Peak-to-Peak) value) in memory 161 based on the measurement results from the optical sensor 150.

[0038] The media sensor control unit 160 transmits the basis weight data and surface property data stored in memory 161 to the system control unit 401. The system control unit 401 determines the type of paper from a paper type database 403 in memory 402 based on the acquired basis weight data and surface property data, and displays the print mode corresponding to that paper type on the operation unit 502. The print mode controls predetermined image formation conditions and is given names such as "Thin Paper 1," "Thin Paper 2," "Plain Paper 1," etc.

[0039] 3 and 4 are explanatory diagrams of the configuration of the media sensor 100. Fig. 3 is a schematic diagram of the transport path on which the media sensor 100 is arranged. Fig. 4 is a diagram of the media sensor 100 as seen from the paper transport direction.

[0040] 3, media sensor 100 is installed between a pair of transport rollers 280 and a pair of transport rollers 290 provided on the transport path of image forming apparatus 201A. Media sensor 100 includes a lower block 109 located on one side of the transport path and an upper block 110 located on the other side. Paper pressure rollers 260 and 261 are provided in upper block 110 side by side in a direction intersecting the transport direction of paper S.

[0041] 4(a), the ultrasonic sensor 120 is composed of an ultrasonic transmitter 130 provided in the upper block 110 and an ultrasonic receiver 131 provided in the lower block 109. The optical sensor 150 is provided in the lower block 109. The optical sensor 150 is configured as a CIS (Contact Image Sensor) including a light source 1501 and a line sensor 1502. Note that the optical sensor 150 may be configured using other imaging elements other than a CIS, such as a CCD (Charge-Coupled Device) or a CMOS (Complementary Metal Oxide Semiconductor) sensor.

[0042] When measuring the surface properties of the sheet S using the optical sensor 150, it is necessary to hold the sheet S at the optical focal position. When measuring the basis weight of the sheet S using the ultrasonic sensor 120, it is necessary to reduce the effect of flapping of the sheet S due to transport during ultrasonic measurement. For this reason, paper pressure rollers 260 and 261 are provided to stabilize the posture of the sheet S. The paper pressure roller 260 is an opposing member provided at a position opposite the optical sensor 150 across the transport path, and presses the sheet S against the optical sensor 150. The paper pressure roller 261 is an opposing member provided at a position opposite the paper pressure roller 260 with the ultrasonic sensor 120 in between. The paper pressure rollers 260 and 261 transport the sheet S while pulling it with a predetermined tension at the measurement position of the ultrasonic sensor 120, thereby reducing flapping during transport.

[0043] A roller attachment / detachment unit 250 is attached to the upper block 110. The roller attachment / detachment unit 250 includes a roller attachment / detachment sensor 2501, a roller attachment / detachment motor 2502, and a roller attachment / detachment shaft 2503. The roller attachment / detachment sensor 2501 includes a photointerrupter 2501a and a light-shielding flag 2501b. The light-shielding flag 2501b is provided coaxially with the roller attachment / detachment shaft 2503.

[0044] The roller attachment / detachment unit 250 controls the attachment / detachment operation of the paper pressure roller 260 and the paper pressure roller 261 between an attachment position (paper pressure position, first position: Figure 4(b)) and a detachment position (separated position, second position: Figure 4(a)). The roller attachment / detachment motor 2502 is a drive source for attaching and detaching the paper pressure roller 260 and the paper pressure roller 261. The roller attachment / detachment motor 2502 is controlled by the media sensor control unit 160, and drives the roller attachment / detachment shaft 2503 to rotate. The roller attachment / detachment shaft 2503 attaches and detaches the paper pressure roller 260 and the paper pressure roller 261 by moving the upper block 110 up and down via a cam mechanism (not shown).

[0045] When the paper pressure rollers 260 and 261 are in the attached state, the paper sheet S is pressed against the ultrasonic sensor 120 and the optical sensor 150. In the attached state (attached position), the paper sheet S is sandwiched and transported in the nip between the paper pressure rollers 260 and 261 and the ultrasonic sensor 120 and the optical sensor 150. When the paper pressure rollers 260 and 261 are in the released state (released position), the distance between the paper pressure rollers 260 and 261 and the ultrasonic sensor 120 and the optical sensor 150 becomes greater than in the attached state.

[0046] The roller attachment / detachment sensor 2501 detects the attachment and detachment of the paper pressure roller 260 and the paper pressure roller 261. Figure 4(a) shows the detached state. The light-shielding flag 2501b is in a position that does not block the photointerrupter 2501a. Figure 4(b) shows the attached state. The light-shielding flag 2501b is in a position that blocks the photointerrupter 2501a. In this way, by detecting the positions of the paper pressure roller 260 and the paper pressure roller 261 with the roller attachment / detachment sensor 2501, the attached and detached states can be accurately controlled.

[0047] The media sensor 100 as described above reduces variations in the position and orientation of the paper S when measuring the physical property values ​​of the paper S. This allows for stable measurement of the physical property values. FIG. 5 is an explanatory diagram of the paper type database 403. The physical property values ​​of the paper S measured by the media sensor 100 are used to determine the type of the paper S based on the paper type database 403. Note that, although a configuration in which the paper type database 403 is stored in the memory 402 of the system controller 400 is described in this embodiment, the paper type database 403 may also be stored in the memory 161 of the media sensor 100. In this case, the process of determining the type of paper S performed by the system control unit 401 will be performed by the media sensor control unit 160.

[0048] (Basis weight data) The ultrasonic sensor 120 measures the basis weight of the paper S by receiving ultrasonic waves transmitted from the ultrasonic transmitter 130 via the transport path with the ultrasonic receiver 131. The basis weight here is the mass per unit area of ​​the paper S and is expressed in [gsm].

[0049] 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 that converts mechanical displacement into an electrical signal, and an electrode terminal. When a pulse voltage of a predetermined frequency is applied to the electrode terminal of the ultrasonic transmitter 130, the piezoelectric element oscillates and generates ultrasonic waves. The ultrasonic transmitter 130 transmits ultrasonic waves in the direction of the ultrasonic receiver 131. When the ultrasonic waves reach the paper S, the paper S vibrates due to the ultrasonic waves. The ultrasonic waves pass through the paper S and are received by the ultrasonic receiver 131. In this way, the ultrasonic waves are transmitted from the ultrasonic transmitter 130, attenuated by the paper S, and propagate to the ultrasonic receiver 131.

[0050] The piezoelectric element of the ultrasonic receiver 131 generates an output voltage at the electrode terminal that corresponds to the amplitude of the received ultrasonic waves. Compared to when there is no paper S between the ultrasonic transmitter 130 and the ultrasonic receiver 131, the ultrasonic waves propagated through the paper S are attenuated by the amount of the paper S. Therefore, the output voltage output from the ultrasonic receiver 131 is also attenuated when there is paper S compared to when there is no paper S.

[0051] The transmittance of the paper S is calculated from the ratio of the output voltage of the ultrasonic receiver 131 when there is no paper S to the output voltage of the ultrasonic receiver 131 when there is paper S. Because the ultrasonic transmittance of the paper S changes depending on the basis weight (area density), the basis weight of the paper S can be estimated by using the ultrasonic transmittance-basis weight conversion curve shown in FIG. 5(a). Here, the transmittance-basis weight conversion curve is experimentally obtained in advance and stored in the paper type database 403.

[0052] The media sensor control unit 160 notifies the system control unit 401 of the transmittance of the sheet S measured by the media sensor 100 (ultrasonic sensor 120) as basis weight data. The system control unit 401 converts the notified basis weight data (transmittance) into basis weight using the paper type database 403. Note that, in addition to using the paper type database 403, other methods for converting the transmittance of the sheet S into basis weight include calculation using an approximation formula that approximates a transmittance-basis weight conversion curve using the least squares method or the like.

[0053] (Surface data) The optical sensor 150 is used to measure the surface properties of the paper S. The light source 1501 of the optical sensor 150 is, for example, an LED (Light Emitting Diode), and light from the LED is refracted by a light guide and then irradiated onto the paper S at a predetermined angle. The light reflected from the paper is focused on the line sensor 1502 by the light guide and read as an image. FIG. 6 is an explanatory diagram of the line sensor 1502.

[0054] As shown in Fig. 6(a), the multiple image pickup elements of the line sensor 1502 are arranged in a direction intersecting the transport direction of the paper S. In this embodiment, the image pickup elements 1502a are provided for 400 pixels, and an image of 400 pixels can be read in a single image pickup in a direction intersecting the transport direction of the paper S. Note that light from the light source 1501 is irradiated linearly onto the paper S in a direction intersecting the transport direction.

[0055] In this embodiment, the line sensor 1502 has multiple image sensors 1502a arranged at a pitch of 300 dpi. The optical sensor 150 can only read one line of an image in one scan. In this case, the measurement results of the optical sensor 150 will detect localized unevenness on the paper S. Therefore, if the surface texture of the paper S is determined based on only one line of an image (measurement results), the deviation in the output results for each measurement position will be large. In this way, the measurement results for one line are not suitable for measuring the surface texture of the paper S. In other words, the one line of an image measured in one scan of the optical sensor 150 is insufficient to identify the surface texture of the paper S.

[0056] To solve this problem, the optical sensor 150 scans (measures) one line multiple times while the paper S is being transported, and then connects the images of one line obtained in the transport direction to measure the entire surface of the paper S. This makes it possible to grasp the tendency of the surface properties of the paper S over the entire surface of the paper S.

[0057] The image captured by the line sensor 1502 is digitally processed by the media sensor control unit 160 and then stored as pixel output values ​​for each pixel in memory 161 of the media sensor 100. From the pixel output values ​​of all pixels stored in memory 161, pixel output values ​​of a data calculation pixel area used to calculate surface property data are extracted. The method for extracting the data calculation pixel area will be described later.

[0058] The pixel output values ​​in the data calculation pixel area are processed by the media sensor control unit 160 to calculate the adjacent pixel difference integrated value, brightness value, and PP value, which are surface data. The calculated surface data (adjacent pixel difference integrated value, brightness value, and PP value) are stored in the memory 161 of the media sensor 100.

[0059] Adjacent pixel difference integrated value The adjacent pixel difference integrated value is a value obtained by integrating the difference (adjacent pixel difference value) between pixel output values ​​of adjacent pixels of the optical sensor 150 (line sensor 1502) and adding the result for the number of lines. The adjacent pixel difference integrated value is an index that expresses the unevenness of the paper S.

[0060] The adjacent pixel difference integrated value will be explained using Figure 6(b). In Figure 6(b), each pixel is numbered 1 to n, and the measurement lines are also named A to m in the order of the measurement lines. When the measurement value (pixel output value) of each pixel is the measurement line name + pixel number, the adjacent pixel difference integrated value Y is expressed by the following equation (1) using the adjacent pixel difference integrated value ki (A≦i≦m) of line i. kA= |A2-A1|+|A3-A2|+…+|An-A(n-1)| kB= |B2-B1|+|B3-B2|+…+|Bn-B(n-1)| · · · ki=|i2-i1|+|i3-i2|+…+|in-i(n-1)| · · · km=|m2-m1|+|m3-m2|+…+|mn-m(n-1)| Y = kA + kB + ... + ki + ... + km ... (1)

[0061] Brightness value The brightness value is a value obtained by adding the integrated values ​​of the luminance values ​​of each pixel measured by the line sensor 1502 for the number of measured lines. The brightness value represents the brightness of the paper S. The brightness value M is expressed by the following equation (2). M=A1+A2+…+B1+B2+…+mn…(2)

[0062] PP value The PP value is calculated by subtracting the minimum from the maximum pixel output value for one line and adding the result for the number of lines measured. By combining the PP value with the adjacent pixel difference integrated value, the type of paper S can be determined more accurately.

[0063] For example, transparent films made of resins such as PET (Polyethylene Terephthalate) reflect less light and are measured with low brightness. Paper with intentionally textured surfaces, such as embossed paper, has a larger difference in pixel output values ​​between adjacent pixels due to the texture, resulting in a larger adjacent pixel difference integrated value. Recycled paper also has an uneven grain direction, and the pulp fibers become shorter after multiple recycling processes, so the surface tends to be measured as rough. Coated paper appears less textured due to the coating layer on the surface, resulting in a smaller adjacent pixel difference integrated value. Because of this, the PP value is used because the adjacent pixel difference integrated value alone may not be enough to accurately determine the surface quality of paper S.

[0064] (Data calculation pixel area) Fig. 7 is an explanatory diagram of a mechanism for suppressing positional fluctuations between the optical sensor 150 and the paper S. Fig. 8 is an explanatory diagram of a data calculation pixel area.

[0065] 7 is an enlarged view of the optical sensor 150 and the paper pressure roller 260. A media position fixing unit 1503 fixes the position of the paper S between the optical sensor 150 and the paper pressure roller 260. In addition, a light receiving surface 1504 of the optical sensor 150 has a gap between the paper S and the light receiving surface 1504.

[0066] X0, Xa1, ..., XN below the line sensor 1502 represent addresses (pixel positions). The line sensor 1502 is made up of N pixels (image pickup elements), and the measurement results of each pixel are assigned addresses (described later as pixel addresses) numbered 0 to N, X0 to XN.

[0067] The area of ​​pixel addresses X0 to XN indicates the total pixel area of ​​line sensor 1502. Pixel address X0 indicates the pixel address of the start point of the total pixel area, and pixel address XN indicates the pixel address of the end point of the total pixel area. The area of ​​pixel addresses Xa1 to Xa2 indicates the effective pixel area. Pixel address Xa1 indicates the pixel address of the start point of the effective pixel area, and pixel address Xa2 indicates the pixel address of the end point of the effective pixel area.

[0068] The effective pixel area indicates a pixel area in which a pixel output value equal to or greater than a predetermined value is obtained when a subject with uniform reflectance at a nominal position is irradiated with light from a light source 1501 and the light reflected from the subject is received by a line sensor 1502. The start pixel address Xa1 and end pixel address Xa2 of the effective pixel area are determined in advance from the results of such measurements.

[0069] The area of ​​pixel addresses Xb1 to Xb2 indicates the data calculation pixel area. Pixel address Xb1 indicates the pixel address of the start point of the data calculation pixel area, and pixel address Xb2 indicates the pixel address of the end point of the data calculation pixel area. The data calculation pixel area is an area obtained by extracting pixels from within the valid area that can more stably measure the paper.

[0070] The method for determining the data calculation pixel area will be explained using Figure 8. Figure 8(a) shows the pixel output values ​​of each pixel of the line sensor 1502 when measuring reference paper with uniform reflectance at a nominal position in the configuration of Figure 7. The horizontal axis represents the position of each pixel on one line of the line sensor 1502, and the vertical axis represents the pixel output value of each pixel. The pixel output value is stable between pixel address Xb1 and pixel address Xb2 (data calculation pixel area), but fluctuates greatly between pixel address Xa1 and pixel address Xb1 and between pixel address Xb2 and pixel address Xa2. In other words, the pixel output value fluctuates greatly near the media orientation fixing section 1503.

[0071] Figure 8(b) is a graph of adjacent pixel difference values ​​calculated from the pixel output values ​​of each pixel in Figure 8(a). The adjacent pixel difference value is the absolute value of the difference between adjacent pixel output values, and is calculated using equation (3) (measurement line A is used as an example, where j is the pixel number). The adjacent pixel difference values ​​calculated for all pixels in the data calculation area over the measurement lines are the adjacent pixel difference integrated value described above. Adjacent pixel difference value Sj=|Aj+1-Aj| ... (3)

[0072] As with FIG. 8(a), the horizontal axis in FIG. 8(b) indicates the pixel position on one line of the line sensor 1502. The vertical axis in FIG. 8(b) indicates the adjacent pixel difference value. Like the pixel output value, the adjacent pixel difference value also fluctuates significantly near the media orientation fixed portion 1503. A threshold value Th is set for the adjacent pixel difference value, and the area excluding areas where the adjacent pixel difference value is equal to or greater than the threshold Th becomes the data calculation pixel area.

[0073] The threshold value Th is experimentally determined in advance based on the results of measurements of multiple paper types to be measured under the environmental conditions of high temperature and high humidity (30°C, 80%), normal temperature and normal humidity (23°C, 50%), and low temperature and low humidity (15°C, 10%) using the optical sensor 150. The threshold value Th is changed based on the measurement results, and the value at which the difference in adjacent pixel integrated value Y between the above three different environmental conditions is equal to or less than the tolerance value PTh=10 as shown below is determined as the threshold value Th. |(YH / YN-1)|×100 < PTh |{(YL / YN)-1}|×100 < PTh

[0074] YH, YN, and YL are adjacent pixel integrated values ​​at high temperature and high humidity, normal temperature and normal humidity, and low temperature and low humidity, respectively. In this embodiment, the threshold value Th is set to 1550, and by narrowing the data calculation pixel area from pixel addresses Xa1-Xa2 in the effective pixel area to pixel addresses Xb1-Xb2, YH = 140000, YN = 127000, and YL = 116000. This makes it possible to reduce the amount of change in the adjacent pixel integrated value Y due to environmental influences to a maximum of approximately +10%. The threshold value Th and tolerance value PTh vary depending on the product configuration and must be determined for each product.

[0075] The region of pixel addresses Xb1 to Xb2, starting from and ending at pixel addresses Xb1 and Xb2 where the adjacent pixel difference value intersects with the threshold value Th determined in this way, becomes the data calculation pixel region. The pixel addresses Xb1 and Xb2 that indicate the data calculation pixel region are stored in advance in memory 161 of media sensor 100.

[0076] (Notification of basis weight data and surface property data) As described above, the media sensor control unit 160 notifies the system control unit 401 of the measurement results, that is, the basis weight data (transmittance) and surface property data (adjacent pixel difference integrated value, brightness value, PP value). The system control unit 401 determines the paper type by referring to the paper type database 403 based on the notified basis weight data (transmittance) and surface property data (adjacent pixel difference integrated value, brightness value, PP value). In the table shown in FIG. 5(b), a and b are the threshold values ​​for brightness value and adjacent pixel difference value, respectively, and c is the threshold value for ultrasonic transmittance. The system control unit 401 compares the basis weight data and surface property data with the respective threshold values. As a result of the comparison, the system control unit 401 determines that the paper type corresponding to the range of each threshold value is the paper type of the fed paper S.

[0077] (Paper type determination sequence) 9 is a flowchart showing the paper type determination process. This process is executed when the user places paper S on manual tray 5, sets automatic paper identification mode from operation unit 502, and inputs an instruction to execute a print job. The automatic paper identification mode is an operating mode for automatically identifying the type of paper S using media sensor 100 and setting image formation conditions.

[0078] When the system control unit 401 receives an instruction to execute a print job from the operation unit 502, it executes the print job (S901). Because the automatic paper identification mode is set, the system control unit 401 instructs the media sensor control unit 160 to measure the paper S (S902), causing the media sensor control unit 160 to perform paper measurement processing (S903). The system control unit 401 obtains the measurement results (basis weight data, surface property data) from the media sensor 100 through the paper measurement processing. The system control unit 401 determines the paper type of the paper S based on the measurement results from the paper measurement processing (S904).

[0079] 10 is a flowchart showing the paper measurement process of S903. As a result of the paper measurement process, the media sensor control unit 160 generates basis weight data (transmittance) and surface property data (adjacent pixel difference integrated value, brightness value, PP value) of the paper S.

[0080] When the media sensor control unit 160 starts the paper measurement process, it performs an initialization process of the ultrasonic sensor 120 and the optical sensor 150 to prepare for measuring the paper (S1001). In the initialization process, the media sensor control unit 160 sets the initial setting values ​​stored in the memory 161 in the ultrasonic sensor 120 and the optical sensor 150.

[0081] When the initialization process is complete, the media sensor control unit 160 controls the roller attachment / detachment unit 250 to switch the paper pressure roller 260 and paper pressure roller 261 to the attached position (paper pressure position: Figure 4(b)) (S1002). The media sensor control unit 160 controls the ultrasonic sensor 120 to perform ultrasonic measurement when no paper S is present (ultrasonic no-paper measurement) and saves the measurement results in memory 161 (S1003). When the ultrasonic no-paper measurement is complete, the media sensor control unit 160 controls the roller attachment / detachment unit 250 to switch the paper pressure roller 260 and paper pressure roller 261 to the detached position (separated position: Figure 4(a)) (S1004).

[0082] When the paper pressure rollers 260 and 261 are switched to the release position, the media sensor control unit 160 instructs the device control unit 301 to feed paper S. In response, the device control unit 301 feeds one sheet of paper S from the manual feed tray 5 and temporarily stops the fed paper S at the measurement position of the media sensor 100 (S1005). The media sensor control unit 160 acquires from the device control unit 301 the paper arrival timing indicating that the paper S has reached the measurement position (S1006). Upon acquiring the paper arrival timing from the device control unit 301, the media sensor control unit 160 controls the roller attach / detach unit 250 to switch the paper pressure rollers 260 and 261 to the attachment position (paper pressure position: FIG. 4(b)) (S1007).

[0083] After a predetermined time has elapsed since the paper pressure rollers 260 and 261 were switched to the on position, the media sensor control unit 160 performs ultrasonic measurement using the ultrasonic sensor 120 (ultrasonic paper-present measurement) and stores the measurement results in memory 161 (S1008). The media sensor control unit 160 performs measurement using the optical sensor 150 and stores the pixel output values ​​in memory 161 (S1009). When the measurement by the optical sensor 150 is completed, the media sensor control unit 160 controls the roller attach / detach unit 250 to switch the paper pressure rollers 260 and 261 to the detached position (separated position: Figure 4(a)) (S1010).

[0084] The media sensor control unit 160 calculates basis weight data (transmittance) based on the measurement results of the ultrasonic paper-out measurement and the ultrasonic paper-present measurement stored in memory 161, and stores the data in memory 161 (S1011). The media sensor control unit 160 calculates surface property data (adjacent pixel difference integrated value, brightness value, PP value) based on the pixel output values ​​stored in memory 161, and stores the data in memory 161 (S1012). The media sensor control unit 160 transmits the calculated basis weight data and surface property data to the system control unit 401, and ends the paper measurement process (S1013).

[0085] (Media sensor failure) If the media sensor 100 malfunctions, the paper type determination described above will no longer be possible. In other words, the processes shown in Figures 9 and 10 will no longer be possible. Figure 11 is a flowchart showing the paper type determination process, including determining whether the media sensor 100 has malfunctioned. This process is executed when the user places paper S on the manual feed tray 5, sets the automatic paper identification mode on the operation unit 502, and inputs an instruction to execute a print job.

[0086] 9, the system control unit 401 executes the print job and instructs the media sensor control unit 160 to measure the paper S (S1101, S1102). The system control unit 401 waits for a predetermined time until it receives a normal response (Ack, Acknowledge) from the media sensor control unit 160 indicating that the media sensor 100 is operating normally (S1103).

[0087] If a normal response is obtained within a predetermined time (S1103: Y), the system control unit 401 causes the media sensor control unit 160 to perform paper measurement processing, which will be described later (S1104). The system control unit 401 obtains a notification from the media sensor control unit 160 indicating whether the paper measurement processing has ended normally (S1105). If the paper measurement processing has ended normally (S1105: Y), the system control unit 401 determines the paper type of the paper S based on the measurement results of the paper measurement processing (basis weight data, surface property data) obtained from the media sensor 100, similar to the processing of S904 in FIG. 9 (S1106). If the media sensor 100 is operating normally, the paper type determination processing is performed in this manner.

[0088] If the paper measurement process has not ended normally (S1105: N), the system control unit 401 acquires either a manual feed degraded notification or a media sensor degraded notification from the media sensor control unit 160 (S1107). If a manual feed degraded notification has been acquired (S1107: Y), the system control unit 401 transitions to manual feed degraded mode (S1108). If a media sensor degraded notification has been acquired (S1107: N), the system control unit 401 transitions to media sensor degraded mode (S1109). Note that "degraded" means that a function is stopped. For example, "manual feed degraded" means that paper feeding by the manual feed unit 235 is prohibited, and "media sensor degraded" means that the media sensor 100 is not allowed to measure paper S. In media sensor degraded mode, paper feeding by the manual feed unit 235 is permitted.

[0089] If a normal response is not obtained within the predetermined time in the processing of S1103 (S1103: N), the system control unit 401 also transitions to media sensor degenerate mode (S1109). In this embodiment, if a communication error occurs between the system controller 400 and the media sensor 100, the media sensor control unit 160 will be unable to send measurement results (basis weight data, surface property data) to the system control unit 401. This state is also media sensor degenerate.

[0090] The system control unit 401 stops the print job after switching to the degenerate mode (S1100). If the media sensor 100 does not operate normally, or if communication between the media sensor 100 and the system controller 400 cannot be performed normally, the paper type determination process is performed in this manner.

[0091] 12 is a flowchart showing the paper measurement process of S1104. In addition to generating basis weight data (transmittance) and surface property data (adjacent pixel difference integrated value, brightness value, PP value) for the paper S in the same manner as the process of FIG. 10, the media sensor control unit 160 also performs an abnormality determination for the media sensor 100. The abnormality determination for the media sensor 100 includes an abnormality determination for the media sensor 100 itself, as well as a malfunction determination for the operation of the paper pressure rollers 260 and 261. In other words, the abnormality determination for the media sensor 100 determines whether or not there is a malfunction in the parts used to determine the type of paper S.

[0092] The media sensor control unit 160 performs initialization processing similar to the processing of S1001 and S1002 in Fig. 10, and switches the paper pressure rollers 260 and 261 to the landing position (paper pressing position) (S1201, S1202). The media sensor control unit 160 performs processing to determine whether the paper pressure rollers 260 and 261 are in an abnormal landing position (S1203), which will be described later.

[0093] If the paper pressure rollers 260 and 261 have moved to the landing position normally (S1203: Y), the media sensor control unit 160 performs ultrasonic no-paper measurement, similar to the process of S1003 in FIG. 10, and stores the measurement results in memory 161 (S1204). The media sensor control unit 160 determines whether there is an abnormality in the ultrasonic sensor 120, which will be described later (S1205). If the ultrasonic sensor 120 is operating normally (S1205: Y), the media sensor control unit 160 controls the optical sensor 150 to perform optical measurement (optical no-paper measurement) when no paper S is present, and stores the measurement results in memory 161 (S1206). The media sensor control unit 160 determines whether there is an abnormality in the optical sensor 150, which will be described later (S1207).

[0094] If the optical sensor 150 is operating normally (S1207: Y), the media sensor control unit 160 controls the roller attaching / detaching unit 250 to switch the paper pressure roller 260 and the paper pressure roller 261 to the release position (separated position) (S1208). The media sensor control unit 160 performs a release position abnormality determination process for the paper pressure roller 260 and the paper pressure roller 261 (described later) (S1209).

[0095] If the paper pressure rollers 260 and 261 have moved normally to the release position (S1209: Y), the media sensor control unit 160 acquires the paper arrival timing from the device control unit 301 (S1210), similar to the processing of S1006 in Fig. 10. When the media sensor control unit 160 acquires the paper arrival timing, it controls the roller attach / detach unit 250 to switch the paper pressure rollers 260 and 261 to the landing position (paper pressing position) (S1211). The media sensor control unit 160 performs a landing position abnormality determination process for the paper pressure rollers 260 and 261, which will be described later (S1212).

[0096] If the paper pressure rollers 260 and 261 have moved to the landing position normally (S1212: Y), the media sensor control unit 160 performs ultrasonic paper presence measurement and measurement using the optical sensor 150, similar to the processes of S1008 and S1009 in Fig. 10. The media sensor control unit 160 saves the measurement results and pixel output values ​​of the ultrasonic paper presence measurement in memory 161 (S1213, S1214). The media sensor control unit 160 calculates basis weight data (transmittance) and surface property data (adjacent pixel difference integrated value, brightness value, PP value) and saves them in memory 161 (S1216, S1217), similar to the processes of S1011 and S1012 in Fig. 10.

[0097] The media sensor control unit 160 controls the roller attaching / detaching unit 250 to switch the paper pressure rollers 260 and 261 to the detached position (separated position), and transmits the calculated basis weight data and surface property data to the system control unit 401 (S1218). If the paper pressure rollers 260 and 261 have moved to the detached position normally (S1218: Y), the media sensor control unit 160 ends the paper measurement process.

[0098] If the paper pressure rollers 260 and 261 have not moved to the landing position (S1203: N or S1212: N), the media sensor control unit 160 sends a manual feed degraded notification to the system control unit 401 to transition to manual feed degraded mode (S1220). If the paper pressure rollers 260 and 261 have not moved to the removal position (S1209: N or S1218: N), the media sensor control unit 160 sends a manual feed degraded notification to the system control unit 401 to transition to manual feed degraded mode (S1220). If the ultrasonic sensor 120 is not operating normally (S1205: N), the media sensor control unit 160 sends a media sensor degraded notification to the system control unit 401 to transition to media sensor degraded mode (S1219). If the optical sensor 150 is not operating normally (S1207: N), the media sensor control unit 160 transmits a media sensor degeneration notification to the system control unit 401 to transition to the media sensor degeneration mode (S1219).

[0099] The abnormality determination process for the ultrasonic sensor 120 in S1205 will be described. The media sensor control unit 160 compares the measurement result (voltage value of the output voltage) of the ultrasonic paper-out measurement output from the ultrasonic sensor 120 in the process of S1204 with a predetermined reference value (threshold value), and determines an abnormality in the ultrasonic sensor 120 based on the comparison result. In the ultrasonic paper-out measurement, the voltage value of the output voltage is equal to or greater than the reference value because there is no attenuation of the ultrasonic waves by the paper S. However, if the ultrasonic sensor 120 is malfunctioning, the voltage value of the output voltage will be less than the reference value. In this embodiment, the reference value is set to, for example, 0.02 [V], but the reference value is a value that is set appropriately depending on the type of ultrasonic sensor 120, the impedance and tolerance of the peripheral circuitry of the ultrasonic sensor 120, etc., and is not limited to 0.02 [V].

[0100] For example, if the voltage value of the output voltage output from the ultrasonic sensor 120 during ultrasonic paper-out measurement is equal to or greater than the reference value, the media sensor control unit 160 determines that the ultrasonic sensor 120 is operating normally. If the voltage value of the output voltage output from the ultrasonic sensor 120 during ultrasonic paper-out measurement is less than the reference value, the media sensor control unit 160 determines that the ultrasonic sensor 120 is not operating normally. If the ultrasonic sensor 120 is not operating normally, the media sensor control unit 160 determines that the media sensor 100 is not operating normally, and sends a media sensor degeneration notification to the system control unit 401 in the processing of S1219.

[0101] The abnormality determination process of the optical sensor 150 in S1207 will now be described. The media sensor control unit 160 compares the measurement results (pixel output values) of the optical no-paper measurement output from the optical sensor 150 with a predetermined reference value (threshold value), and determines whether the optical sensor 150 is abnormal based on the comparison result. The comparison is performed on the pixel output values ​​of all pixels on one line. For example, in the optical no-paper measurement, since there is no light reflection by the paper S, the pixel output values ​​output from the optical sensor 150 are equal to or greater than the reference value, but if the optical sensor 150 is malfunctioning, the voltage value of the output pixel value will be less than the reference value.

[0102] For example, if all pixel output values ​​output from the optical sensor 150 during the paper-out measurement are equal to or greater than the reference value, the media sensor control unit 160 determines that the optical sensor 150 is operating normally. If any of the pixel output values ​​output from the optical sensor 150 during the paper-out measurement are less than the reference value, the media sensor control unit 160 determines that the optical sensor 150 is not operating normally. If the optical sensor 150 is not operating normally, the media sensor control unit 160 determines that the media sensor 150 is not operating normally, and sends a media sensor degeneration notification to the system control unit 401 in the processing of S1219.

[0103] FIG. 13 is an explanatory diagram of abnormality determination for the optical sensor 150. If even one pixel has a pixel output value below the reference value Th_g, the optical sensor 150 is determined to be faulty. FIG. 13(a) illustrates an example of a normal pixel output value, and FIG. 13(b) illustrates an example of a faulty pixel output value. In this embodiment, the reference value Th_g is set to 5, but the reference value is a value that is set appropriately depending on the type of optical sensor 150, the impedance and tolerance of the peripheral circuits of the optical sensor 150, etc., and is not limited to the reference value Th_g=5.

[0104] The following describes the process of determining whether the paper pressure roller 260 and the paper pressure roller 261 are in an abnormal landing position in S1203 and S1212. After controlling the paper pressure rollers 260 and 261 to move to the landing position (paper pressing position) by driving the roller attach / detach motor 2502, the media sensor control unit 160 determines whether the paper pressure roller 260 and the paper pressure roller 261 have moved to the landing position normally.

[0105] If the media sensor control unit 160 detects that the roller attachment / detachment sensor 2501 is on (at the landing position) within a predetermined time after the above control, it determines that the paper pressure roller 260 and the paper pressure roller 261 have moved to the landing position normally. If the media sensor control unit 160 does not detect that the roller attachment / detachment sensor 2501 is on (at the landing position) within the predetermined time, it determines that the paper pressure roller 260 and the paper pressure roller 261 have not moved to the landing position normally. If the paper pressure roller 260 and the paper pressure roller 261 have not moved to the landing position normally, the media sensor control unit 160 determines that the roller attachment / detachment unit 250 is not operating normally and sends a manual paper feed degeneration notification to the system control unit 401 in the processing of S1220. In this case, since the paper pressure roller 260 and the paper pressure roller 261 have not moved to the landing position, it is considered that they are in a position that does not obstruct the transport of the paper S. Therefore, the manual paper feed degeneration notification in this case allows paper feeding from the manual feed tray 5.

[0106] If the paper pressure rollers 260 and 261 do not switch to the attached position (paper pressing position), and remain in the detached position (separated position), there will be no disruption to the print job, so the media sensor may be degraded. However, because there is a possibility of the roller attachment / detachment sensor 2501 failing, in this embodiment, safety is prioritized and manual paper feed degraded. However, as described above, the media sensor may also be degraded, and the degrading method is not limited.

[0107] The following describes the process of determining whether the paper pressure roller 260 and the paper pressure roller 261 are in a removed position (displaced position) in steps S1209 and S1218. After controlling the roller attach / detach motor 2502 to switch the paper pressure rollers 260 and 261 to the removed position (separated position), the media sensor control unit 160 determines whether the paper pressure roller 260 and the paper pressure roller 261 have moved to the removed position normally.

[0108] If the media sensor control unit 160 detects that the roller attachment / detachment sensor 2501 is off (removed position) within a predetermined time after the above control, it determines that the paper pressure roller 260 and paper pressure roller 261 have moved to the removed position normally. If the media sensor control unit 160 cannot detect that the roller attachment / detachment sensor 2501 is off (removed position) within the predetermined time, it determines that the paper pressure roller 260 and paper pressure roller 261 have not moved to the removed position normally. If the paper pressure roller 260 and paper pressure roller 261 have not moved to the removed position normally, the media sensor control unit 160 determines that the roller attachment / detachment unit 250 is not operating normally, and sends a manual paper feed degeneration notification to the system control unit 401 in the processing of S1220.

[0109] (Media sensor abnormality determination at image forming system 201 startup) The image forming system 201 may perform abnormality determination processing for the media sensor 100 when the image forming system 201 is powered on or when the image forming system 201 is moved, such as when the image forming system 201 returns from a sleep state. Fig. 14 is a flowchart showing the abnormality determination processing for the media sensor when the image forming system 201 is started up.

[0110] When the image forming system 201 is started by turning on the power or waking up from a sleep state, the system control unit 401 instructs the media sensor control unit 160 to perform initialization processing (S1301). The system control unit 401 waits for a predetermined time until it receives a normal response (Ack, Acknowledge) from the media sensor control unit 160 indicating that the media sensor 100 is operating normally (S1302).

[0111] If a normal response is not received within the predetermined time (S1302: N), the system control unit 401 transitions to the media sensor degenerate mode (S1319). If a normal response is received within the predetermined time (S1302: Y), the system control unit 401 causes the media sensor control unit 160 to perform the same processes as S1201 to S1209 in FIG. 12 (S1303 to S1311).

[0112] If the paper pressure roller 260 and paper pressure roller 261 have moved normally to the release position (S1311: Y), a communication check is performed between the media sensor control unit 160 and the device control unit 301. The media sensor control unit 160 acquires a communication check command from the device control unit 301 (S1312). After acquiring the communication check command, the media sensor control unit 160 sends a normal response (Ack, Acknowledge) to the device control unit 301 within a predetermined time (S1313). To achieve this, after sending the communication check command to the media sensor control unit 160, the device control unit 301 waits for a predetermined time until it acquires a normal response from the media sensor control unit 160.

[0113] If a normal response (Ack, Acknowledge) is not sent within the predetermined time (S1313: N), the media sensor control unit 160 sends a manual feed degenerate notification to the system control unit 401 to transition to manual feed degenerate mode (S1320). If a normal response (Ack, Acknowledge) is sent within the predetermined time (S1313: N), the media sensor control unit 160 can execute the process from S1211 onwards in FIG.

[0114] The manual feed degenerate mode will now be described. As described above, upon receiving the manual feed degenerate notification, the system control unit 401 transitions to the manual feed degenerate mode. The system control unit 401 saves information about the media sensor degenerate mode in the memory 402, and controls the user interface on the host device 501 and the operation unit 502 so that the automatic paper identification mode cannot be selected for subsequent print jobs. This prevents the image forming system 201 from setting automatic identification of paper S.

[0115] The media sensor degraded mode will now be described. As described above, upon receiving the media sensor degraded notification, the system control unit 401 transitions to the media sensor degraded mode. The system control unit 401 saves the media sensor degraded mode information in the memory 402, and controls the user interface on the host device 501 and the operation unit 502 so that the automatic paper identification mode cannot be selected in subsequent print jobs. This prevents the image forming system 201 from setting automatic identification of paper S.

[0116] The process shown in Fig. 14 is not performed during a print job, so there is no need to stop the print job. Therefore, there is no need for the user to perform complicated tasks such as removing the paper S. After the process shown in Fig. 14 is performed, the process shown in Fig. 9 or 10 may be performed in response to a user operation.

[0117] As described above, the image forming system 201 of this embodiment determines whether a failure in the media sensor 100 has occurred for each cause of the failure and performs degeneration processing according to the cause of the failure. As a result, if a failure occurs related to the paper pressure roller 260 or the paper pressure roller 261, paper feeding from the manual paper feed unit 235 is prohibited, eliminating paper transport abnormalities such as jams and skew. In this case, image formation can continue by feeding paper from the cassette paper feed unit 230. If a failure occurs in the media sensor 100 itself, the manual tray 5 can continue to be used. This allows appropriate measures to be taken depending on the cause of the failure, even if the component (media sensor 100) that determines the paper type fails. This allows the image forming apparatus 201A to continue forming images, thereby reducing downtime.

[0118] Media sensor 100 may be configured to be provided in a position where it can detect paper S fed from cassette paper feed unit 230. In this case, if media sensor 100 malfunctions, the paper feed function from cassette paper feed unit 230 will be stopped. Media sensor 100 may also be configured to be provided on a path where the transport path for paper fed from cassette paper feed unit 230 and the transport path for paper fed from manual paper feed unit 235 join. In this case, if media sensor 100 malfunctions, the paper feed functions from cassette paper feed unit 230 and manual paper feed unit 235 will be stopped.

Claims

1. a stacking means for stacking paper; an image forming means for forming an image on the paper fed from the stacking means; a measuring means for measuring a characteristic amount of the paper, the measuring means being disposed on one side of a transport path along which the paper is transported from the stacking means to the image forming means; an opposing member disposed on the other side of the conveying path opposite the measuring means; a moving means for moving the opposing member between a first position and a second position; a control means for controlling the moving means, the first position is a position where the paper is nipped and conveyed at a nip portion between the measuring means and the opposing member, and the second position is a position where the distance between the measuring means and the opposing member is farther than the first position; The control means prohibits the sheet from being fed from the stacking means when the moving means is unable to move the opposing member between the first position and the second position. Image forming device.

2. the control means prohibits the sheet from being fed from the stacking means when the opposing member cannot move from the first position, and allows the sheet to be fed from the stacking means when the opposing member cannot move from the second position.

2. The image forming apparatus according to claim 1.

3. the control means does not allow the measurement means to measure the characteristic amount of the paper when the opposing member cannot move from the second position.

3. The image forming apparatus according to claim 2.

4. the control means permits the paper to be fed from the stacking means and does not cause the measuring means to measure the characteristic quantities of the paper when the moving means is in a state where the opposing member can be moved between the first position and the second position and the measuring means is in a state where the characteristic quantities of the paper cannot be measured.

2. The image forming apparatus according to claim 1.

5. the control means determines that the moving means cannot move the opposing member between the first position and the second position if the opposing member does not move to the first position after controlling the moving means to move the opposing member from the second position to the first position.

2. The image forming apparatus according to claim 1.

6. the control means determines that the moving means cannot move the opposing member between the first position and the second position if the opposing member does not move to the second position after controlling the moving means to move the opposing member from the first position to the second position.

6. The image forming apparatus according to claim 5.

7. the moving means has a detecting means for detecting the position of the opposing member, The control means detects the movement of the opposing member to the first position and the movement of the opposing member to the second position by the detection means.

7. The image forming apparatus according to claim 5.

8. the measuring means includes an ultrasonic sensor; The control means determines whether the characteristic amount of the paper cannot be measured by the measurement means based on a result of the ultrasonic sensor performing measurement in a state where the paper is not present.

5. The image forming apparatus according to claim 4.

9. the measuring means includes an optical sensor; The control means determines whether the characteristic amount of the paper cannot be measured by the measurement means based on a result of the optical sensor performing measurement in a state where the paper is not present.

5. The image forming apparatus according to claim 4.

10. The control means determines the state of the moving means and the state of the measuring means when a print job is started.

5. The image forming apparatus according to claim 4.

11. The control means determines the state of the moving means and the state of the measuring means at the time of startup.

5. The image forming apparatus according to claim 4.

Images