Image formation device

Abstract

To provide an image formation device which can print an image on a sheet in image formation conditions set according to a type of the sheet.SOLUTION: An image formation device 201 includes a control unit 400 which stops transport of a sheet when a sheet detection sensor 270 detects the sheet to press the sheet against a media sensor 100 with a sheet pressing roller 260 and then resumes transport of the sheet to cause the media sensor 100 to measure a feature amount of the sheet and determine image formation conditions based on the measured feature amount. The control unit 400 stops transport of the sheet by a transport roller pair 280 and sets the image formation conditions in an image formation unit 201B when the image formation conditions are determined and then resumes transport of the sheet by the transport roller pair 280.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] In recent years, image forming devices have been equipped with a media sensor for determining the type of paper, which is a recording medium. The media sensor measures the characteristics of the paper using an optical sensor, ultrasonic sensor, or the like. The image forming device extracts the relevant paper information from pre-registered paper information based on the measurement results of the paper characteristics by the media sensor, and determines the type (paper type) of the paper. The paper information is information including the characteristics of each paper type (basis weight, surface properties, etc.). The image forming device prints an image on the paper under image formation conditions according to the determined paper type. Patent Document 1 discloses an image forming device that determines the paper type and forms an image. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-29622 A Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional image forming devices of this type temporarily stop the paper at the measurement position of the media sensor and bring the paper into contact with the media sensor. The image forming device then resumes transport of the paper, measures the characteristics while transporting the paper, determines the paper type, and sets the image formation conditions. If the time required from measuring the characteristics of the paper to setting the image formation conditions is long, there is a possibility that an image will be printed on the paper before the image formation conditions are set. In this case, there is a risk that printing with image formation conditions set according to the paper type will not be possible.

[0005] SUMMARY OF THE PRESENT DISCLOSURE In view of the above-mentioned problems, a primary object of the present invention is to provide an image forming apparatus capable of printing an image on paper under image forming conditions that correspond to the type of paper. [Means for solving the problem]

[0006] The image forming apparatus of the present invention includes a conveying means for conveying paper, a measuring means for measuring a characteristic amount of the paper conveyed by the conveying means, a detecting means for detecting the paper conveyed by the conveying means, a pressing member movable between a first position away from the measuring means and a second position closer to the measuring means than the first position, a moving means for moving the pressing member, an image forming means for forming an image on the paper conveyed by the conveying means under predetermined image forming conditions, and a control means, wherein the control means stops conveying the paper by the conveying means when the detecting means detects the paper. the pressing member is moved from the first position to the second position by the moving means, and while the pressing member is disposed at the second position, the conveying means resumes conveying the paper and the measuring means measures a characteristic amount of the paper, the image formation conditions are determined based on the measured characteristic amount, the conveying means stops conveying the paper before an image is formed on the paper by the image forming means, the image formation conditions are set in the image forming means, the conveying means resumes conveying the paper and the image forming means forms an image according to the image formation conditions. Effect of the Invention

[0007] According to the present invention, an image can be printed on a sheet of paper under image forming conditions that correspond to the type of the sheet of paper. [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]4A and 4B are diagrams illustrating the configuration of a media sensor. [Diagram 5] 4A and 4B are diagrams illustrating the configuration of a media sensor. [Figure 6] Illustrative diagram of the relationship between transmittance and basis weight [Figure 7] 13A and 13B are diagrams illustrating the results of reading by an optical sensor. [Figure 8] FIG. [Figure 9] FIG. [Figure 10] FIG. [Figure 11] 4 is a process flow diagram showing an image forming process. [Figure 12] 4 is another process flow diagram illustrating the image formation process. [Figure 13] FIG. 4 is a diagram illustrating the configuration of a media sensor. 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 operating conditions according to the characteristics of the paper S. Note that a print job is 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] (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). Note that 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 by the image forming apparatus 201.

[0031] 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 paper characteristics are, for example, the surface properties and basis weight of the paper. 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.

[0032] 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.

[0033] 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.

[0034] The media sensor 100 includes an information processing unit 160, 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 and a paper pressure roller control unit 271 are 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.

[0035] 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.

[0036] The paper detection sensor 270 is a sensor for detecting the paper S being transported to the measurement position of the media sensor 100. The control unit 400 temporarily stops transporting the paper S after a predetermined time has elapsed since the paper detection sensor 270 detected the transported paper S. The predetermined time is set in advance and is the time from when the leading edge of the paper S is detected by the paper detection sensor 270 until it reaches the transport roller pair 290. This causes the paper S to stop at the measurement position of the media sensor 100.

[0037] When the transport of the paper S stops, the information processing unit 160 controls the paper pressure roller control unit 271 to move the paper pressure roller described below. The paper pressure roller, which will be described in detail later, can move between a first position away from the media sensor 100 and a second position closer to the media sensor 100 than the first position. The paper pressure roller waits at the first position except when the media sensor 100 measures the characteristic amount of the paper S. When the transport of the paper S stops, the paper pressure roller control unit 271 moves the paper pressure roller from the first position to the second position under the control of the information processing unit 160. This causes the paper S to abut against the media sensor 100.

[0038] When the paper pressure rollers move to the second position, the control unit 400 resumes transport of the paper S. When the paper pressure rollers move to the second position, the information processing unit 160 starts a paper measurement sequence for measuring the characteristic quantities of the paper S. By starting the paper measurement sequence, the information processing unit 160 causes the ultrasonic sensor 120 and the optical sensor 150 of the media sensor 100 to perform the measurement operation of the characteristic quantities.

[0039] The ultrasonic sensor 120 measures the paper S with ultrasonic waves and outputs a predetermined voltage value as a 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, a brightness integrated value, and a PP (Peak to Peak) integrated value.

[0040] 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 basis weight information and the 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 the paper type database 402, and determines the image forming conditions (for example, the secondary transfer bias value, the target fixing temperature of the fixing unit 201E, the conveying speed during fixing, etc.) corresponding to the paper type and basis weight. The control unit 400 controls the image forming operation under the determined image forming conditions. Note that, although the method of determining the image forming conditions from the type and basis weight of the paper S has been described, the present invention is not limited to this. For example, the control unit 400 determines the type of the paper S (paper type, paper type information) based on the information corresponding to the acquired surface property and basis weight. The control unit 400 may determine one image forming condition corresponding to the information corresponding to the type of the paper S from among a plurality of image forming conditions stored in the paper type database 402.

[0041] (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.

[0042] As shown in FIG. 4, the media sensor 100 is provided between the pair of conveying rollers 280 and the pair of conveying rollers 290, and acquires basis weight information and surface property information of the conveyed paper S. The paper detection sensor 270 is provided upstream of the media sensor 100 in the conveying direction of the paper S (the conveying roller pair 280 side). The paper pressure roller 260 is provided at a position facing the media sensor 100 with respect to the conveying path of the paper S. As described above, the paper pressure roller 260 is configured to move between a first position separated from the media sensor 100 and a second position close to the media sensor 100. FIG. 4(a) illustrates a state in which the paper pressure roller 260 is disposed at the first position. FIG. 4(b) illustrates a state in which the paper pressure roller 260 is disposed at the second position. When the paper pressure roller 260 is disposed at the second position, the paper S is pressed against the media sensor 100.

[0043] 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.

[0044] 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.

[0045] 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, and is configured to press the paper S toward the optical sensor 150. FIG. 5(a) illustrates a state in which the paper pressure rollers 260 and 261 are arranged at a first position. FIG. 5(b) illustrates a state in which the paper pressure rollers 260 and 261 are arranged at a second position.

[0046] By being disposed at the second position, the paper pressure rollers 260, 261 are 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, 261. In other words, the paper pressure rollers 260, 261 are pressing members that press the paper S to bring it into contact with the media sensor 100. This keeps the side of the paper S perpendicular to the transport direction parallel to the direction of the line sensor 1502. In this state, variation in the position and attitude of the paper S is reduced, so that the media sensor 100 can measure the characteristics of the paper S, such as the surface properties and basis weight, in a stable state.

[0047] 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.

[0048] (Basis weight measurement) In the ultrasonic sensor 120, an ultrasonic transmitter 130 and an ultrasonic receiver 131 are disposed at positions facing each other 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. In the ultrasonic sensor 120, the ultrasonic receiver 131 receives ultrasonic waves output from the ultrasonic transmitter 130 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.

[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 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.

[0050] The transmittance is the ratio of the output voltage when there is no paper S between the ultrasonic transmitter 130 and the ultrasonic receiver 131 to the output voltage when there is paper S. The transmittance of ultrasonic waves changes depending on the basis weight (areal density) of the paper S. Therefore, the basis weight of the paper S can be estimated by using a conversion formula or conversion table between the transmittance and basis weight. FIG. 6 is an explanatory diagram of the relationship between the transmittance and basis weight. The basis weight is estimated using a conversion formula or conversion table that expresses such a relationship.

[0051] (Surface quality measurement) The surface property of the paper S is detected by the 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 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. FIG. 7 is an explanatory diagram of the reading result by the optical sensor 150.

[0052] Fig. 7(a) illustrates an example of an image read by the line sensor 1502. The line sensor 1502 has a plurality of light receiving elements 1502a. The plurality of light receiving elements 1502a are arranged in a direction perpendicular to the conveying direction of the paper S, and can read one line of an image at a time. In the example of Fig. 7(a), 400 light receiving elements 1502a are provided, and an image of 400 pixels (A1 to A400) can be read at a time.

[0053] In this embodiment, multiple light receiving elements 1502a are arranged to provide 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 read results for each read position is large in a one-line image. For this reason, the optical sensor 150 performs multiple read operations on the paper S being transported, and obtains the read results of the image of multiple lines of the paper S. By stitching together the read 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.

[0054] The information processing unit 160 performs digital processing on the image read by the optical sensor 150, and stores the results of the digital processing as output values ​​(brightness values) for each pixel. The information processing unit 160 acquires and accumulates a difference integrated value, a lightness integrated value, and a PP integrated value of the brightness value from the saved brightness values ​​for each pixel. These values ​​become surface property information of the paper S.

[0055] The difference accumulation value is a value obtained by accumulating the difference in brightness value for each adjacent pixel of the image read by the line sensor 1502, and adding the results for the number of lines. The difference accumulation value is an index that expresses the unevenness of the paper. In FIG. 7(b), if the detection value of each pixel is expressed by the pixel position (1 to n) and the detection line (A to m), the difference accumulation value Y is expressed by the following formula (1) using the difference accumulation value k for each line. Note that the direction of the detected pixel data in FIG. 7(b) is the arrangement direction of the light receiving elements 1502a of the line sensor 1502 (the direction of the pixels in one line). Also, the detection line direction in FIG. 7(b) is the transport direction of the paper S. k1=|A2-A1|+|A3-A2|…+|An-A(n-1)| k2=|B2-B1|+|B3-B2|…+|Bn-B(n-1)| · · · km=|m2-m1|+|m3-m2|…+|mn-m(n-1)| Y = k1 + k2 + ... + km ... (1)

[0056] The brightness integrated value is obtained by adding up the integrated values ​​of the luminance values ​​of each pixel received by the line sensor 1502 for the number of detected lines, and represents the brightness of the surface of the paper S. The brightness integrated value M is expressed by the following formula (2). M=A1+A2+…+B1+B2+…+mn…(2)

[0057] The PP integrated value is the sum of the difference between the maximum and minimum brightness values ​​of one line for the number of detected lines. Transparent films made of resins such as PET reflect less light from the light source 1501, and are detected as low in brightness. Paper with intentionally created geometric unevenness on the surface, such as embossed paper, increases the brightness difference between adjacent pixels due to the unevenness, and the difference integrated value increases. Recycled paper also has an uneven grain direction, and the pulp fibers become shorter after going through several recycling processes, so the surface tends to be detected as rough. Conversely, coated paper appears to have fewer unevenness due to the coating layer on the surface, and the difference integrated value tends to be smaller. The brightness integrated value and PP integrated value are parameters used to distinguish these types of paper.

[0058] The control unit 400 acquires basis weight information and surface property information (integrated difference value, integrated brightness value, and integrated PP value) as characteristic amounts of the paper S from the information processing unit 160, and determines image forming conditions by referring to the paper type database 402. The control unit 400 performs image formation according to the print job under the determined image forming conditions.

[0059] (Determination of Image Formation Conditions) As described above, the control unit 400 acquires basis weight information and surface property information (integrated difference value, integrated brightness value, and integrated PP value) from the media sensor 100. The control unit 400 determines the surface property of the sheet S based on the surface property information, and classifies the paper type of the sheet S based on the surface property. Figures 8 and 9 are illustrative diagrams of a paper type classification table. The control unit 400 classifies the paper type based on such a classification table.

[0060] FIG. 8 is a classification table of paper types according to difference integrated value and brightness integrated value. FIG. 8 is a matrix in which the surface properties of the paper are measured in advance and the paper types are classified by machine learning, with the difference integrated value on the vertical axis and the brightness integrated value on the horizontal axis. The thresholds for classifying the paper types are a0 to a3 for the brightness integrated value and b0 to b4 for the difference integrated value. These thresholds are stored in the paper type database 402 of the memory 401. Note that such a classification table may be a three-dimensional matrix that can classify the paper types in more detail by adding the PP integrated value as a parameter. The control unit 400 identifies the paper type by comparing the surface property information with each threshold value.

[0061] 9 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 media sensor 100 falls within. Threshold values ​​indicating the basis weight ranges are indicated by C1 to C23 and are stored in paper type database 402 in memory 401.

[0062] 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. 9 of the paper type determined based on the surface property information and the classification table of Fig. 8. The control unit 400 determines the image formation conditions according to the determined paper type. Fig. 10 is a paper type classification table that combines the classification tables of Fig. 8 and Fig. 9. Such a classification table may be stored in the paper type database 402 of the memory 401, and the control unit 400 may determine the image formation conditions using such a classification table.

[0063] In this way, the control unit 400 checks the measurement results obtained from the media sensor 100 against the paper type database 402 to determine the image formation conditions (transport speed during fixing, target fixing temperature, transfer voltage during secondary transfer, etc.). If the determined image formation conditions differ from the image formation conditions already set and the image formation conditions need to be updated, the control unit 400 stops the transport of the paper S again and changes the image formation conditions. After changing the image formation conditions, the control unit 400 resumes the transport of the paper S and performs image formation.

[0064] 11 is a process flow diagram showing the image formation process including the process of determining the image formation conditions. As described above, the image formation conditions are determined by the control unit 400, the paper detection sensor 270, and the media sensor 100 in cooperation with each other. This process is started when the control unit 400 receives an instruction to start a print job from the operation unit 502 or the host device 501.

[0065] When the control unit 400 receives an instruction to start a print job, it starts conveying the paper S (S1001). The paper S is fed from the cassette paper feed unit 230 or the manual paper feed unit 235. When the conveyance of the paper S starts, the control unit 400 and the media sensor 100 wait until the paper detection sensor 270 detects the paper S (S1002).

[0066] When the paper detection sensor 270 detects the paper S, the control unit 400 waits until a first predetermined time has elapsed (S1003), and stops conveying the paper S after the first predetermined time has elapsed (S1004). The first predetermined time is the time from when the leading edge of the paper S is detected by the paper detection sensor 270 until it reaches the conveying roller pair 290.

[0067] When the paper detection sensor 270 detects the paper S, the information processing unit 160 of the media sensor 100 waits until a second predetermined time has elapsed (S1003), and after the second predetermined time has elapsed, the paper pressure roller control unit 271 moves the paper pressure rollers 260, 261 to the second position. As the paper pressure rollers 260, 261 move to the second position, the paper S comes into contact with the media sensor 100 (S1005). The second predetermined time that the information processing unit 160 waits is longer than the first predetermined time that the control unit 400 waits, and is the time from when the leading edge of the paper S is detected by the paper detection sensor 270 until the transport of the paper S stops (the time from S1002 to S1004).

[0068] The information processing unit 160 notifies the control unit 400 that the paper S has been brought into contact with the media sensor 100. When the control unit 400 receives the notification that the paper S has been brought into contact with the media sensor 100, it resumes conveyance of the paper S (S1006). The control unit 400 notifies the media sensor 100 of the resumption of conveyance of the paper S. When the information processing unit 160 receives the notification that conveyance of the paper S has been resumed, it starts measuring the paper S with the ultrasonic sensor 120 and the optical sensor 150 (S1007). When the measurement is completed, the information processing unit 160 moves the paper pressure rollers 260 and 261 to the first position by the paper pressure roller control unit 271 to separate them from the media sensor 100 (S1008). The information processing unit 160 notifies the control unit 400 of the measurement results (basis weight information, surface property information) (S1009).

[0069] The control unit 400 refers to the paper type database 402 based on the acquired measurement results and determines the paper type (S1010). The control unit 400 determines the image forming conditions based on the determined paper type (S1011). The control unit 400 determines whether the determined image forming conditions are different from the current image forming conditions, thereby determining whether the image forming conditions need to be changed (S1012).

[0070] If it is necessary to change the image forming conditions (S1012: Y), the control unit 400 stops the conveyance of the paper S again (S1013). The control unit 400 changes the image forming conditions after stopping the conveyance of the paper S (S1014). When the change of the image forming conditions is completed (S1015), the control unit 400 resumes the conveyance of the paper S (S1016). For example, when the current image forming conditions are image forming conditions corresponding to plain paper, if the image forming conditions determined from the measurement result of the media sensor 100 are image forming conditions corresponding to thick coated paper, it is necessary to change the image forming conditions. In this case, for example, the fixing temperature is changed from 200[°C] to 230[°C]. A few seconds are required for this, and the conveyance of the paper S is stopped for this time.

[0071] After restarting the transport of the paper S, the control unit 400 controls the image formation on the paper S (S1017). If there is no need to change the image formation conditions (S1012: N), the control unit 400 controls the image formation (S1017) without stopping the transport of the paper S or changing the image formation conditions.

[0072] In this way, when it is necessary to change the image formation conditions, the transport of the paper S is temporarily stopped and the image formation conditions are changed, so that an image is formed on the paper S under optimal image formation conditions. Therefore, the image quality of the image printed on the paper S is maintained.

[0073] (Modification) 12 is another process flow diagram showing the image forming process including the process of determining the image forming conditions. The process (S2001 to S2011) from the start of conveyance of the paper S to the determination of the image forming conditions is similar to the process from S1001 to S1011 in FIG. 11, so the description will be omitted.

[0074] After determining the image formation conditions, the control unit 400 stops the transport of the paper S (S2012) and sets the image formation conditions (S2013). When a predetermined time has elapsed since the start of setting the image formation conditions (S2014), the control unit 400 resumes the transport of the paper S (S2015). The predetermined time is the maximum time required to change the image formation conditions. Thereafter, the control unit 400 starts image formation (S2016).

[0075] By setting the predetermined time from setting the image forming conditions to restarting the transport of the paper S as the maximum time required to change the image forming conditions, it becomes possible to form an image under optimal image forming conditions with a simple sequence.

[0076] 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.

[0077] 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.

[0078] The above describes the operation of the paper pressure roller 260 relative to the optical sensor 150. The paper pressure roller 260 is disposed so as to sandwich the ultrasonic sensor 120 between it and the paper pressure roller 261 (see FIG. 5). With this configuration, when the paper S reaches the measurement position of the media sensor 100, the paper pressure roller 260 and the paper pressure roller 261 press the paper S against the media sensor 100 at the measurement position of the ultrasonic sensor 120. The ultrasonic sensor 120 measures the characteristic amounts by transmitting ultrasonic waves through the paper S. Because the state of the paper S is stabilized by the paper pressure roller 260 and the paper pressure roller 261, the ultrasonic sensor 120 can also measure the characteristic amounts of the paper S with high accuracy.

[0079] Similarly, the paper pressure roller 260 and the paper pressure roller 261 are useful when a transmission type optical sensor is used. FIG. 13 is a configuration explanatory diagram of a media sensor when a transmission type optical sensor 150a is used. The transmission type optical sensor 150a transmits light through the paper S to measure the feature amount. For this purpose, a light source 1501a and a line sensor 1502a are arranged opposite each other across the conveyance path. Also, the paper pressure roller 260 is not arranged, and the paper pressure roller 262 is arranged opposite the paper pressure roller 261 across the optical sensor 150a. Since the state of the paper S is stabilized by the paper pressure roller 261 and the transfer pressure roller 262, the transmission type optical sensor 150a can also measure the feature amount of the paper S with high accuracy. In other words, in addition to the configuration in which the paper pressure roller 260 directly presses the paper S against the optical sensor 150, the state of the paper S can also be stabilized by pressing the paper S against the optical sensor 150a with two rollers. This allows the sheet S to be stably measured even with the transmission type optical sensor 150a.

[0080] 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.

[0081] In the above description, the paper type database 402 is provided in the memory 401 of the controller 200, but the storage location of the paper type database 402 is not limited to this. For example, the paper type database 402 may be stored in the media sensor 100. In this case, the information processing unit 160 determines the type and basis weight of the paper S, and the information processing unit 160 also determines the image forming conditions. The controller 200 including the paper type database 402 may be provided on a cloud. In this case, if the image forming apparatus 201 is connected to the cloud via a network, the image forming conditions can be set using the latest paper type database and a discrimination algorithm.

Claims

1. A conveying means for conveying paper; a measuring means for measuring a characteristic amount of the paper conveyed by the conveying means; a detection means for detecting the paper conveyed by the conveying means; a pressing member movable between a first position spaced apart from the measuring means and a second position closer to the measuring means than the first position; A moving means for moving the pressing member; an image forming means for forming an image on the paper conveyed by the conveying means under predetermined image forming conditions; A control means, the control means stops the transport of the paper by the transport means when the detection means detects the paper, and causes the moving means to move the pressing member from the first position to the second position; With the pressing member disposed at the second position, the conveying means resumes conveying the paper, and the measuring means measures a characteristic amount of the paper, and the image forming conditions are determined based on the measured characteristic amount. before an image is formed on the paper by the image forming means, the transport means stops transporting the paper, the image forming means sets the image forming conditions, and the transport means restarts transporting the paper to cause the image forming means to form an image under the image forming conditions. Image forming device.

2. the control means stops the transport of the paper by the transport means and moves the pressing member to the second position by the moving means when a first predetermined time has elapsed since the detection means detected the paper; the control means causes the measurement means to measure the characteristic amount of the paper when a second predetermined time has elapsed since the detection means detected the paper; The second predetermined time is longer than the first predetermined time.

2. The image forming apparatus according to claim 1.

3. the conveying means includes a first conveying roller pair provided upstream of the measuring means in the conveying direction of the paper, and a second conveying roller pair provided downstream of the measuring means in the conveying direction of the paper, the detection means is provided between the first conveying roller pair and the measurement means, the first predetermined time is a time from when the leading edge of the paper is detected by the detection means to when the leading edge of the paper reaches the second conveying roller pair, The second predetermined time is a time from when the leading edge of the paper is detected by the detection means to when the transport of the paper is stopped.

3. The image forming apparatus according to claim 2.

4. The control unit is characterized in that, when the determined image forming conditions are different from the current image forming conditions, the control unit stops the conveyance of the paper by the conveyance unit and updates the image forming conditions.

2. The image forming apparatus according to claim 1.

5. The control unit is configured to resume conveyance of the paper when updating of the image forming conditions is completed.

5. The image forming apparatus according to claim 4.

6. The control unit is configured to resume the conveyance of the paper by the conveying unit when a predetermined time has elapsed since the start of setting the determined image forming conditions.

2. The image forming apparatus according to claim 1.

7. The predetermined time is a maximum time required for changing the image forming conditions.

7. The image forming apparatus according to claim 6.

8. the control means determines the type of the paper based on the characteristic amount of the paper measured by the measurement means, and determines image forming conditions in accordance with the paper type.

2. The image forming apparatus according to claim 1.

9. The control means is configured to move the pressing member to the first position by the moving means when the measurement of the characteristic amount of the paper by the measuring means is completed.

2. The image forming apparatus according to claim 1.

10. The pressing member is a rotating member.

10. The image forming apparatus according to claim 9.

Images