Image forming apparatus

Abstract

An image forming apparatus includes: a conveyance section configured to convey a sheet; a measuring unit for measuring a characteristic quantity of the sheet conveyed by the conveying unit; a sheet detection sensor for detecting the sheet conveyed by the conveyance unit; a pressing member movable between a first position separated from the measuring portion and a second position closer to the measuring portion than the first position; a moving portion configured to move the pressing member; an image forming section configured to form an image on the sheet conveyed by the conveying section based on a predetermined image forming condition; and a controller configured to stop conveying the sheet by the conveying portion in a case where the sheet detection sensor detects the sheet.

Description

Technical Field

[0001] The present invention relates to an image forming apparatus including a media sensor for discriminating a type of a sheet (sheet type). Background Art

[0002] In recent years, an image forming apparatus includes a media sensor for identifying the type of a sheet material as a recording medium. The media sensor measures a characteristic quantity of a sheet material by using, for example, an optical sensor or an ultrasonic sensor. The image forming apparatus extracts relevant sheet material information from pre-registered sheet material information and identifies the type of the sheet material (sheet material type) based on the measurement result of the characteristic quantity of the sheet material acquired by the media sensor. The sheet material information is information including characteristic quantities (e.g., quantitative and surface characteristics) of each sheet material type. The image forming apparatus prints an image on the sheet material based on an image forming condition corresponding to the determined sheet material type. In U.S. Patent No. 8,045,868, an image forming apparatus for forming an image by determining a sheet material type is disclosed.

[0003] In the related art, this type of image forming apparatus temporarily stops a sheet at a measuring position of a medium sensor, and then brings the sheet against the medium sensor. Then, the image forming apparatus restarts the conveyance of the sheet, measures a characteristic amount while conveying the sheet, determines the type of the sheet, and sets an image forming condition. In the case where the time period required from measuring the characteristic amount of the sheet to setting the image forming condition is long, there is a possibility that an image is printed on the sheet before the image forming condition is set. In this case, there is a concern that printing may be performed before the image forming condition is set according to the type of the sheet. Summary of the invention

[0004] An image forming apparatus according to at least one embodiment of the present invention includes: a conveying section configured to convey a sheet; a measuring section for measuring a characteristic amount of the sheet conveyed by the conveying section; a detection sensor for detecting the sheet conveyed by the conveying section; a pressing member capable of moving between a first position separated from the measuring section and a second position closer to the measuring section than the first position; a moving section configured to move the pressing member; an image forming section configured to form an image on the sheet conveyed by the conveying section based on a predetermined image forming condition; and a control section, wherein the control section is configured to: when the detection sensor detects a When a sheet is not received, the conveying section stops conveying the sheet and controls the moving section to move the pressing member from the first position to the second position; when the pressing member is arranged in the second position, the conveying section is controlled to restart conveying the sheet, so as to control the measuring section to measure the characteristic quantity of the sheet and determine the predetermined image forming condition based on the measured characteristic quantity; and before the image forming section forms an image on the sheet, the conveying section stops conveying the sheet to set the predetermined image forming condition in the image forming section, and restarts conveying the sheet by the conveying section to control the image forming section to form an image based on the predetermined image forming condition.

[0005] Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings). BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a structural diagram of an image forming apparatus.

[0007] Figure 2A and Figure 2B It is an enlarged view of the fixing device.

[0008] Figure 3 This is a diagram illustrating the controller.

[0009] Figure 4A and Figure 4B This is a diagram illustrating the structure of a media sensor.

[0010] Figure 5A and Figure 5B This is a diagram illustrating the structure of a media sensor.

[0011] Figure 6 This is a diagram illustrating the relationship between transmittance and quantity.

[0012] Fig. 7A and Figure 7B It is an explanatory diagram of the reading result obtained by the optical sensor.

[0013] Figure 8 This is an example diagram of a classification table of sheet material types.

[0014] Fig. 9This is an example diagram of a classification table of sheet material types.

[0015] Fig.10 This is an example diagram of a classification table of sheet material types.

[0016] Fig.11 is a process flow chart for illustrating image forming processing.

[0017] Fig.12 is another process flow chart for illustrating the image forming process.

[0018] Fig.13 This is a diagram illustrating the structure of a media sensor. DETAILED DESCRIPTION

[0019] Now, at least one exemplary embodiment 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 gram per square meter (gsm).

[0020] <Image Forming Apparatus>

[0021] Figure 1 201 is a block diagram of an image forming apparatus according to at least one embodiment. The image forming apparatus 201 according to at least one embodiment is, for example, a tandem intermediate transfer type laser beam printer using an electrophotographic process. The image forming apparatus 201 forms a full-color image or a monochrome image on a sheet S as a recording medium based on image data acquired from an external device such as a personal computer via a network or based on image data acquired from an image reading device 202 provided on top of the image forming apparatus 201 and outputs the sheet S.

[0022] The image forming apparatus 201 has a component for forming an image in a main body 201A, and includes an image reading device 202 and an operation unit 502 on top of the main body 201A. A discharge space D including a placement portion 223 for receiving a sheet S to be discharged into the discharge space D after image formation is formed between the main body 201A of the image forming apparatus 201 and the image reading device 202.

[0023] The image reading device 202 is a reader that reads an image from a manuscript to generate image data. The image reading device 202 is used, for example, in a process of copying a manuscript. In at least one embodiment, the image reading device 202 is configured as a part of the image forming apparatus 201. However, the image reading device 202 is not limited to this structure, and the image reading device 202 can be electrically connected to the image forming apparatus 201 as a device different from the image forming apparatus 201.

[0024] The operation unit 502 is a user interface including an input interface and an output interface. Examples of the input interface include various key buttons and a touch panel. Examples of the output interface include a display and a speaker. The user can input various instructions to the image forming device 201 through the operation unit 502. The image forming device 201 notifies the user of various types of information by displaying various screens on the display of the operation unit 502. In at least one embodiment, the operation unit 502 is configured as a part of the image forming device 201. The operation unit 502 is not limited to this structure, and the operation unit 502 can be electrically connected to the image forming device 201 as a device different from the image forming device 201.

[0025] The image forming apparatus 201 includes an image forming unit 201B, an intermediate transfer unit 201C, a secondary transfer unit 201D, a fixing device 201E, and a cassette sheet feeding unit 230 in a main body 201A. The main body 201A includes a manual sheet feeding unit 235.

[0026] Each of the cassette sheet feeding units 230 feeds a sheet S from a corresponding one of the sheet feeding cassettes 1 that accommodate the sheet S. The cassette sheet feeding unit 230 includes a pickup roller 2 and a separation unit. The separation unit includes a feed roller 3 and a retard roller 4 for separating the sheet S sent out from the pickup roller 2. The sheets S are fed one by one from the sheet feeding cassette 1 through the pickup roller 2 and the separation unit. In at least one embodiment, a structure is described in which a plurality of (four in this example) cassette sheet feeding units 230 are provided. However, any number of cassette sheet feeding units 230 may be provided. The sheet S fed from the cassette sheet feeding unit 230 is conveyed to the registration roller pair 240 via the conveying roller pair 280 and 290.

[0027] The sheet S may also be fed from a unit other than the cassette sheet feeding unit 230, that is, from the manual sheet feeding unit 235. The manual sheet feeding unit 235 includes a manual feeding tray 5 for receiving the sheet S placed by the user. Similar to the cassette sheet feeding unit 230, the manual sheet feeding unit 235 includes a pickup roller and a separation unit, and the sheets S are fed one by one from the manual feeding tray 5. The sheet S fed from the manual sheet feeding unit 235 is also conveyed to the registration roller pair 240 via the conveying roller pair 280 and 290. The conveying roller pair 280 and 290 is a rotating member for conveying the sheet S.

[0028] The media sensor 100 for measuring the characteristic amount of the sheet S is arranged on the conveying path between the conveying roller pair 280 and the conveying roller pair 290. The conveying roller pair 280 is arranged on the upstream side of the media sensor 100 in the conveying direction of the sheet S, and the conveying roller pair 290 is arranged on the downstream side of the media sensor 100 in the conveying direction of the sheet S. The media sensor 100 outputs, for example, information corresponding to a quantitative amount (quantitative information) and information corresponding to a surface characteristic (surface characteristic information) as the characteristic amount of the sheet S conveyed from the cassette sheet feeding unit 230 or the manual sheet feeding unit 235. The media sensor 100 may be arranged at least one of the following two positions: a position where the sheet S fed from the cassette sheet feeding unit 230 can be measured and a position where the sheet S fed from the manual sheet feeding unit 235 can be measured. The details of the structure of the media sensor 100 will be described later.

[0029] The image forming unit 201B is a four-drum full-color type, and includes a laser scanner 210 and four process boxes 211. The four process boxes 211 are used to form toner images of four colors (specifically, yellow (Y), magenta (M), cyan (C), and black (K)). Each process box 211 includes a photosensitive drum 212, a charging device 213, and a developing device 214. A toner box 215 is arranged above the process box 211. The toner box 215 is used to replenish toner to the corresponding developing device 214.

[0030] The intermediate transfer unit 201C includes an intermediate transfer belt 216 wound around a driving roller 216a and a tension roller 216b. Inside the intermediate transfer belt 216, four primary transfer rollers 219 are provided, which abut against the intermediate transfer belt 216 at positions opposite to the photosensitive drums 212. The driving roller 216a driven by a driving unit (not shown) drives the intermediate transfer belt 216 to rotate in the direction of the arrow.

[0031] The secondary transfer unit 201D includes a secondary transfer roller 217, which is arranged to sandwich the intermediate transfer belt 216 at a position opposite to the driving roller 216a. The fixing device 201E is arranged on the downstream side of the secondary transfer roller 217 along the conveying direction of the sheet S, and includes a pressure roller 220a and a heating roller 220b. On the downstream side of the fixing device 201E along the conveying direction of the sheet S, a first discharge roller pair 225a, a second discharge roller pair 225b and a reversing unit 201F for duplex printing are arranged. The reversing unit 201F for duplex printing includes a reversing roller pair 222 and a re-conveying passage R. The reversing roller pair 222 can rotate in the forward and reverse directions. The re-conveying passage R allows the sheet S with an image formed on one side to be conveyed to the image forming unit 201B.

[0032] The image forming apparatus 201 having the above-described structure operates as follows. When acquiring an instruction to start a print job, the image forming apparatus 201 acquires image data from the image reading device 202 or from an external device, and forms an image corresponding to the image data on a sheet S. At this time, the image forming apparatus 201 performs each step of image formation based on an image forming condition given according to the characteristics of the sheet S. A print job is a series of operations performed based on a print signal instructing to form an image on a sheet S, wherein the sheet S is conveyed and an image is formed on the sheet S, and after the image forming operation is completed, the sheet S is discharged to the placement portion 223. The image forming apparatus 201 acquires an instruction to start a print job from the operation unit 502 or an external device.

[0033] The image forming unit 201B uniformly charges the surface of the photosensitive drum 212 to a potential having a predetermined polarity using the charging device 213. The laser scanner 210 irradiates the uniformly charged surface of the photosensitive drum 212 with a corresponding laser beam modulated based on image data. Thus, electrostatic latent images of corresponding colors (yellow, magenta, cyan, and black) are formed on the corresponding surfaces of the photosensitive drum 212.

[0034] The image forming unit 201B develops the electrostatic latent image formed on the photosensitive drum 212 using the developing device 214. The electrostatic latent image is developed on the photosensitive drum 212 with the toner of the corresponding color, thereby forming a toner image of the corresponding color on the photosensitive drum 212. The toner images are sequentially transferred from the photosensitive drum 212 to the rotating intermediate transfer belt 216 in an overlapping manner by the primary transfer roller 219. In this way, a full-color toner image is formed on the intermediate transfer belt 216. The intermediate transfer belt 216 rotates to convey the full-color toner image to the secondary transfer unit 201D.

[0035] In parallel with this operation of forming a toner image, the sheets S are conveyed one by one to the registration roller pair 240 by the cassette sheet feeding unit 230 or the manual sheet feeding unit 235. The characteristic amount of the sheet S is measured by the medium sensor 100 before the sheet S reaches the registration roller pair 240. The image forming apparatus 201 sets an image forming condition based on the measured characteristic amount, and performs subsequent image formation based on the set image forming condition. The image forming condition to be set includes, for example, a voltage value of a secondary transfer bias applied to the secondary transfer roller 217 during transfer of the toner image to the sheet S, a fixing temperature when the image is fixed by the fixing device 201E, and a conveying speed of the sheet S at the time of fixing.

[0036] The registration roller pair 240 corrects the skew of the sheet S conveyed to the registration roller pair 240. After the skew is corrected, the sheet S is conveyed to the secondary transfer unit 201D by the registration roller pair 240 in synchronization with the timing at which the toner image carried on 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 to the sheet S using a secondary transfer bias applied to the secondary transfer roller 217.

[0037] The sheet S with the transferred toner image is conveyed to the fixing device 201E. The fixing device 201E pinches and conveys the sheet S using a nip portion formed by the pressure roller 220a and the heating roller 220b. The fixing device 201E heats the sheet S using the heating roller 220b while pinching and conveying the sheet S, thereby melting and mixing the toner of the corresponding color on the sheet S. Furthermore, the fixing device 201E presses the sheet S using the pressure roller 220a, thereby fixing the melted and mixed toner to the sheet S. At this time, the viscosity of the melted toner generates an adhesive force on the sheet S to the heating roller 220b.

[0038] Figure 2A and Figure 2B 201E. In the case where the rigidity (strength) of the sheet S is small, the adhesion force generated on the sheet S to the heating roller 220b may cause the sheet S to be rolled up by the rotating heating roller 220b ( Figure 2B Therefore, a separation plate 221 ( Figure 2A ).

[0039] The image forming apparatus 201 can determine the state of the separation plate 221 according to the type and basis weight of the sheet S identified based on the measurement result of the media sensor 100. For example, in the case of performing image formation on a type of sheet S having a smaller rigidity, the separation plate 221 is arranged so that the distal end of the separation plate 221 contacts the surface of the heating roller 220b, as shown in FIG. Figure 2A As shown, the sheet S is separated from the heating roller 220b. In the case of image formation on a sheet S of a type having a large rigidity, the sheet S is not rolled up by the heating roller 220b. Therefore, the separation plate 221 is arranged so that the distal end of the separation plate 221 does not contact the surface of the heating roller 220b. In this way, the surface of the heating roller 220b can be prevented from being worn by the separation plate 221.

[0040] The sheet S with the fixed image is discharged to the discharge space D by any one of the first discharge roller pair 225a and the second discharge roller pair 225b. The sheet S is placed on the placement portion 223 provided on the bottom surface of the discharge space D in a protruding manner. In the case where images are to be formed on both sides of the sheet S, the sheet S with the fixed image on one side is conveyed to the re-conveying path R by the reversing roller pair 222. The sheet S is conveyed to the image forming unit 201B again, and an image is formed on the other side of the reversed sheet S. The re-conveying path R allows the sheet S to be conveyed to the conveying path between the conveying roller pair 290 and the registration roller pair 240.

[0041] <controller>

[0042] Figure 3 2 is an explanatory diagram of a controller for controlling the operation of such an image forming apparatus 201. The controller 200 is, for example, an information processing device including a central processing unit (CPU). The controller 200 can be implemented by, for example, a microprocessor unit (MPU) or an application specific integrated circuit (ASIC). The controller 200 controls the above-mentioned image forming operation performed by the image forming apparatus 201.

[0043] The controller 200 includes a control unit 400 and a memory 401. The memory 401 stores, for example, a control program for an image forming operation, initial values ​​of various setting values, and various types of data required for the image forming operation. In addition, the memory 401 has a storage area for storing a sheet type database 402. The sheet type database 402 is a database in which the correspondence between the characteristic amount of the sheet, the sheet type, and the image forming condition is preset. The characteristic amount of the sheet is, for example, the surface characteristics and the quantitative amount of the sheet. The control unit 400 is connected to an operation unit 502, a host device 501 as an external device, and a medium sensor 100.

[0044] The host device 501 is, for example, a personal computer, an image scanner, or a fax machine. The operation unit 502 inputs, for example, instructions and settings received via the input interface to the control unit 400. The operation unit 502 outputs various types of information via the output interface under the control of the control unit 400. As described above, the operation unit 502 may include a display as an output interface, and display various types of information on the display.

[0045] The control unit 400 acquires an instruction to start a print job from the host device 501 or the operation unit 502, and starts the print job. The control unit 400 acquires image data from the host device 501 or the image reading device 202, and performs image processing on the acquired image data. The control unit 400 executes the print job by causing the image forming unit 201B to form a toner image based on the image data that has been subjected to image processing, and feeding the sheet S.

[0046] The media sensor 100 includes: an information processing unit 160, an ultrasonic sensor 120, and an optical sensor 150. In at least one embodiment, the ultrasonic sensor 120 and the optical sensor 150 are used as a sheet measuring unit. In addition to the ultrasonic sensor 120 and the optical sensor 150, a sheet detection sensor 270 and a sheet pressing roller controller 271 are also connected to the information processing unit 160. The information processing unit 160 is an information processing device implemented by, for example, a CPU, an MPU, or an ASIC. The information processing unit 160 controls the measuring operation of the media sensor 100 and processes the measurement results.

[0047] The control unit 400 discriminates the sheet type based on the measurement result (feature amount of the sheet) of the media sensor 100 processed by the information processing unit 160, and sets the image forming conditions corresponding to the sheet type. The image forming conditions (e.g., the conveying speed at the time of fixing, the target fixing temperature, and the transfer voltage at the time of secondary transfer) vary with the physical properties (e.g., basis weight, rigidity, surface properties, and material) of the sheet S on which the image is to be formed. Therefore, when forming an image, it is necessary to set in advance the image forming conditions corresponding to the feature amount of the sheet S to be used.

[0048] The sheet detection sensor 270 is a sensor for detecting the sheet S conveyed to the measuring position of the media sensor 100. After a predetermined period of time has passed since the sheet detection sensor 270 detected the conveyed sheet S, the control unit 400 temporarily stops the conveyance of the sheet S. The predetermined period of time is set in advance as a period of time from when the sheet detection sensor 270 detects the leading edge of the sheet S until the leading edge of the sheet S reaches the conveying roller pair 290. As a result, the sheet S stops at the measuring position of the media sensor 100.

[0049] When the conveyance of the sheet S stops, the information processing unit 160 controls the sheet pressing roller controller 271 to move the sheet pressing roller described later. The details are described later, but the sheet pressing roller can move between a first position separated from the media sensor 100 and a second position closer to the media sensor 100 than the first position. The sheet pressing roller stands by at the first position except when the media sensor 100 measures the characteristic amount of the sheet S. In the case where the conveyance of the sheet S stops, the sheet pressing roller controller 271 moves the sheet pressing roller from the first position to the second position under the control of the information processing unit 160. As a result, the sheet S abuts against the media sensor 100.

[0050] When the sheet pressing roller moves to the second position, the control unit 400 restarts the conveyance of the sheet S. When the sheet pressing roller moves to the second position, the information processing unit 160 starts a sheet measurement sequence for measuring the feature amount of the sheet S. By starting the sheet measurement sequence, the information processing unit 160 causes the ultrasonic sensor 120 and the optical sensor 150 of the media sensor 100 to perform an operation for measuring the feature amount.

[0051] The ultrasonic sensor 120 measures the sheet S by using ultrasonic waves, and outputs an output value of 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 sheet S from the output value given when the sheet S is present and the output value given when the sheet S is not present. The information processing unit 160 detects quantitative information based on the transmittance of the sheet S. The optical sensor 150 is, for example, a contact image sensor (CIS). The information processing unit 160 stores the brightness value of each pixel as an imaging result acquired by the optical sensor 150. The information processing unit 160 converts the stored brightness value of each pixel into surface characteristic information, such as a difference cumulative value (the sum of the differences in brightness values ​​of adjacent pixels), a brightness cumulative value, and a peak-to-peak (PP) cumulative value.

[0052] The information processing unit 160 sends the quantitative information and the surface property information to the control unit 400. The control unit 400 determines the sheet type and the quantitative of the sheet S based on the acquired quantitative information and the surface property information. The control unit 400 identifies the sheet type of the sheet S based on a plurality of pieces of information stored in the sheet type database 402, and determines an image forming condition corresponding to the sheet type and the quantitative (e.g., a secondary transfer bias value, a target fixing temperature of the fixing device 201E, and a conveying speed during fixing). The control unit 400 controls the image forming operation based on the determined image forming condition. The description given here relates to a method for determining an image forming condition based on the type and the quantitative of the sheet S, but the method is not limited thereto. For example, the control unit 400 determines the type (paper type, paper type information) of the sheet S based on the acquired information corresponding to the surface property and the quantitative. The control unit 400 can determine an image forming condition corresponding to the information corresponding to the type of the sheet S from a plurality of image forming conditions stored in the sheet type database 402.

[0053] <Structure of Media Sensor>

[0054] Figure 4A and Figure 4B as well as Figure 5A and Figure 5B It is an explanatory diagram of the structure of the media sensor 100 . Figure 4A and Figure 4B1 is a view of the media sensor 100 viewed from a direction orthogonal to the conveyance direction of the sheet S. FIG. Figure 5A and Figure 5B 1 is a view of the media sensor 100 viewed from the upstream side in the conveying direction of the sheet S. FIG.

[0055] like Figure 4A and Figure 4B As shown, the media sensor 100 is arranged between the conveying roller pair 280 and the conveying roller pair 290, and acquires the characteristic quantity (quantitative information and surface characteristic information) of the conveyed sheet S. The sheet detection sensor 270 is arranged on the upstream side of the media sensor 100 along the conveying direction of the sheet S (on the conveying roller pair 280 side). The sheet pressing roller 260 is arranged at a position facing the media sensor 100 with respect to the conveying path of the sheet S. As described above, the sheet pressing 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. Figure 4A exemplifies a state in which the sheet pressing roller 260 is arranged in the first position. Figure 4B 2 illustrates a state where the sheet pressing roller 260 is arranged at the second position. By arranging the sheet pressing roller 260 at the second position, the sheet S is pressed toward the media sensor 100. Figure 4B In the state of the second position shown, the sheet pressing roller 260 rotates as the sheet is conveyed.

[0056] like Figure 5A and Figure 5B As shown, in the media sensor 100, the ultrasonic sensor 120 and the optical sensor 150 are arranged at the same position along the conveying direction of the sheet S, and are arranged side by side in a direction orthogonal to the conveying direction. The ultrasonic sensor 120 includes an ultrasonic transmitter 130 and an ultrasonic receiver 131. The optical sensor 150 is a CIS including a light source 1501 (e.g., a light emitting diode (LED)) and a line sensor 1502. The optical sensor 150 can be configured by using a charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor.

[0057] The optical sensor 150 measures the brightness value of the received light so as to measure the surface characteristics of the sheet S. For this purpose, the sheet S needs to be kept at the optical focus position of the optical sensor 150. In the case where the ultrasonic sensor 120 measures the sheet S, the measurement accuracy is improved when there is no influence due to the shaking of the conveyed sheet S. For this purpose, the sheet S needs to be conveyed in a stable posture.

[0058] In at least one embodiment, in order to convey the sheet S in a stable posture, the sheet pressing roller 260 and the sheet pressing roller 261 are arranged between the conveying roller pair 280 and the conveying roller pair 290. The sheet pressing roller 260 and the sheet pressing roller 261 are arranged at the same position along the conveying direction of the sheet S. The sheet pressing roller 260 is arranged to face the optical sensor 150 across the conveying path, and is configured to press the sheet S toward the optical sensor 150. Figure 5A 2 illustrates a state where the sheet pressing rollers 260 and 261 are arranged in the first position. Figure 5B 2 illustrates a state in which the sheet pressing rollers 260 and 261 are arranged at the second position.

[0059] When arranged in the second position, the sheet pressing rollers 260 and 261 are pressed against the sheet S whose conveyance has stopped. The sheet pressing rollers 260 and 261 press the sheet S against the media sensor 100. That is, the sheet pressing rollers 260 and 261 are pressing members that press the sheet S and make the sheet S abut against the media sensor 100. As a result, the side of the sheet S that is orthogonal to the conveyance direction is maintained parallel to the direction of the line sensor 1502. In this state, changes in the position and orientation of the sheet S are reduced, so the media sensor 100 can measure the characteristic quantities of the sheet S, such as surface characteristics and basis weight, in a stable state.

[0060] In a case where the sheet pressing rollers 260 and 261 are arranged in the second position and the conveyance of the sheet S is not stopped, the conveyance causes the sheet S to shake, which may cause the sheet S to be skewed or jammed. It is important that the longitudinal direction of the line sensor 1502 should be orthogonal to the conveyance direction of the sheet S. To this end, the sheet pressing rollers 260 and 261 are pressed against the stopped sheet S so that the characteristic quantity can be stably measured. The control unit 400 restarts the conveyance of the sheet S when the posture of the sheet S is in a stable state, and at the same time instructs the information processing unit 160 to measure the characteristic quantity of the sheet S by using the medium sensor 100. In response to the instruction, the information processing unit 160 starts measuring the characteristic quantity of the sheet S by using the medium sensor 100.

[0061] <Quantitative measurement>

[0062] In the ultrasonic sensor 120, an ultrasonic transmitter 130 and an ultrasonic receiver 131 are arranged at positions opposite to each other across the conveying path. The ultrasonic transmitter 130 is arranged on the upper block 110 side of the media sensor 100. The ultrasonic receiver 131 is arranged on the lower block 109 side of the media sensor 100. The ultrasonic sensor 120 receives the ultrasonic wave output from the ultrasonic transmitter 130 via the conveying path of the sheet S through the ultrasonic receiver 131. The ultrasonic receiver 131 outputs information (output value) for determining the quantitative amount of the sheet S based on the received ultrasonic wave.

[0063] The ultrasonic transmitter 130 and the ultrasonic receiver 131 are each formed of a piezoelectric element, which is an element for converting between mechanical displacement and electrical signals, and an electrode terminal. The ultrasonic transmitter 130 generates ultrasonic waves through the oscillation of the piezoelectric element in response to inputting a pulse voltage having a predetermined frequency to the electrode terminal. The generated ultrasonic wave propagates through the air. When the ultrasonic wave reaches the sheet S, the ultrasonic wave causes the sheet S to vibrate. The ultrasonic wave generated in the ultrasonic transmitter 130 propagates to the ultrasonic receiver 131 via the sheet S. The piezoelectric element of the ultrasonic receiver 131 causes the electrode terminal to generate an output voltage corresponding to the amplitude of the received ultrasonic wave. The output voltage has a voltage value corresponding to the quantitative amount of the sheet S. The output voltage is sent to the information processing unit 160 as an output value.

[0064] The ratio between the output voltage given when the sheet S is not present and the output voltage given when the sheet S is present between the ultrasonic transmitter 130 and the ultrasonic receiver 131 is the transmittance. The transmittance of ultrasonic waves changes with the basis weight (areal density) of the sheet S. Therefore, the basis weight of the sheet S can be estimated by using a conversion formula or a conversion table between the transmittance and the basis weight. Figure 6 This is a diagram illustrating the relationship between transmittance and quantitative value. The quantitative value is estimated by using a conversion formula or conversion table that expresses this relationship.

[0065] <Measurement of surface characteristics>

[0066] The surface characteristics of the sheet S are detected by the optical sensor 150. Light emitted from the light source 1501 irradiates the sheet S at a constant angle through a light guide (not shown). The sheet S reflects the irradiated light. The light reflected by the sheet S forms an image on the line sensor 1502 via a lens (not shown). In this way, the line sensor 1502 can read the light reflected from the sheet S as an image. Fig. 7A and Figure 7B 2 is an explanatory diagram of a reading result obtained by the optical sensor 150 .

[0067] exist Fig. 7A An example of an image read by the line sensor 1502 is illustrated in FIG. The line sensor 1502 includes a plurality of light receiving elements 1502a. The plurality of light receiving elements 1502a are arranged in a direction orthogonal to the conveying direction of the sheet S, so the line sensor 1502 can read an image corresponding to one line at a time. Fig. 7A In the example of , 400 light receiving elements 1502a are arranged, so the line sensor 1502 can read an image of 400 pixels (A1 to A400) at a time.

[0068] In at least one embodiment, a plurality of light receiving elements 1502a are arranged to achieve a resolution of 300 dpi. The image corresponding to one line read by the line sensor 1502 at one time is insufficient as the amount of information for determining the surface characteristics of the sheet S. This is because in the image corresponding to one line, there is a large deviation in the reading result of each reading position. For this reason, the optical sensor 150 performs a plurality of reading operations on the conveyed sheet S, and obtains the reading results of the images of the plurality of lines of the sheet S. By connecting the reading results of the plurality of lines along the conveying direction of the sheet S, the trend of the surface characteristics of the sheet S of a predetermined size can be determined.

[0069] The information processing unit 160 performs digital processing on the image read by the optical sensor 150, and stores the result of the digital processing as an output value (brightness value) of each pixel. The information processing unit 160 acquires and stores the difference cumulative value, the brightness cumulative value, and the PP cumulative value of the brightness value based on the stored brightness value of each pixel. These values ​​are the surface characteristic information of the sheet S.

[0070] The difference accumulation value is obtained by accumulating the difference in brightness values ​​of every two adjacent pixels of the image read by the line sensor 1502 for each of the plurality of lines to obtain the difference accumulation result of the line, and then summing the difference accumulation results of the plurality of lines. The difference accumulation value is an indicator of the unevenness of the sheet. Figure 7B In the case where the detection value of each pixel is represented by the pixel position (1 to n) and the detection line (A to m), the difference cumulative value Y is represented based on the following equation (1), where k represents the difference cumulative value of each line. Figure 7B The detection pixel data direction in is the arrangement direction of the light receiving elements 1502a of the line sensor 1502 (the direction of one pixel line). Figure 7B The detection line direction in φ is the conveying direction of the sheet S.

[0071]

[0072] The brightness integrated value is the sum of the brightness values ​​of each pixel received by the line sensor 1502 for a plurality of detection lines, and represents the brightness of the surface of the sheet S. The brightness integrated value M is represented by the following equation (2).

[0073] M = A1 + A2 + ... + B1 + B2 + ... + mn (2)

[0074] The PP cumulative value is a value obtained by calculating the difference between the maximum and minimum values ​​in the brightness values ​​of each pixel in each of the multiple detection lines, and then summing the differences for each of the multiple detection lines. A transparent film made of a resin such as polyethylene terephthalate (PET) reflects less light irradiated from the light source 1501 and is detected as having low brightness. For embossed paper sheets such as those having intentionally provided geometrical concavities and convexities on the surface, the concavities and convexities increase the brightness difference between adjacent pixels, thereby producing a large difference cumulative value. For recycled paper sheets, the brightness values ​​are not uniform in fiber orientation, and the pulp fibers become shorter after several recycling processes, so the surface characteristics tend to be detected as rough. At the same time, for coated paper sheets, the coating on the surface makes the paper sheet look less concave and convex, and the difference cumulative value tends to become smaller. The brightness cumulative value and the PP cumulative value are parameters used to identify these sheets.

[0075] The control unit 400 acquires quantitative information and surface characteristic information (difference cumulative value, brightness cumulative value, PP cumulative value) as feature amounts of the sheet S from the information processing unit 160, and determines image forming conditions by referring to the sheet type database 402. The control unit 400 performs image formation corresponding to the print job based on the determined image forming conditions.

[0076] <Determining Image Formation Conditions>

[0077] As described above, the control unit 400 acquires quantitative information and surface property information (difference cumulative value, brightness cumulative value, PP cumulative 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 sheet type of the sheet S based on the surface property. Figure 8 and Fig. 9 2 is an example diagram of a classification table of sheet types. The control unit 400 classifies sheet types based on such a classification table.

[0078] Figure 8 It is a classification table of film types based on the difference cumulative value and the brightness cumulative value. Figure 8 The table in is a matrix in which the vertical axis represents the difference cumulative value and the horizontal axis represents the lightness cumulative value, and the surface characteristics of the sheet are measured in advance and the sheet type is classified by machine learning. The thresholds for classifying the sheet type are a0 to a3 for the lightness cumulative value and b0 to b4 for the difference cumulative value. These thresholds are stored in the sheet type database 402 of the memory 401. Note that by also adding the PP cumulative value as a parameter, this classification table can be a three-dimensional matrix capable of classifying the sheet type in more detail. The control unit 400 discriminates the sheet type by comparing the surface characteristic information with each threshold.

[0079] Fig. 9The sheet type is determined based on the basis weight range in which the basis weight measured by the media sensor 100 falls. Thresholds representing the basis weight range are represented by C1 to C23 and are stored in the sheet type database 402 of the memory 401.

[0080] The control unit 400 generates a signal based on the quantitative information obtained from the media sensor 100 and the surface characteristic information and the Figure 8 The sheet type is determined by the classification table Fig. 9 The control unit 400 determines the image forming conditions corresponding to the determined sheet type. Fig.10 It is a summary Figure 8 and Fig. 9 Such a classification table may be stored in the sheet type database 402 of the memory 401, and the control unit 400 may determine the image forming conditions based on such a classification table.

[0081] Therefore, the control unit 400 compares the measurement result acquired from the media sensor 100 with the sheet type database 402 to determine the image forming conditions (e.g., the conveying speed at the time of fixing, the target fixing temperature, and the transfer voltage at the time of secondary transfer). When the image forming conditions need to be updated because the determined image forming conditions are different from the image forming conditions that have been set, the control unit 400 stops the conveyance of the sheet S again and changes the image forming conditions. After the image forming conditions are changed, the control unit 400 restarts the conveyance of the sheet S and performs image formation.

[0082] Fig.11 1 is a process flow chart for illustrating an image forming process including a process for determining an image forming condition. As described above, the image forming condition is determined by the control unit 400, the sheet detection sensor 270, and the medium sensor 100 working in cooperation. The process is started when the control unit 400 obtains an instruction to start a print job from the operation unit 502 or the host device 501.

[0083] When the control unit 400 acquires an instruction to start a print job, the control unit 400 starts conveyance of the sheet S (step S1001). The sheet S is fed from the cassette sheet feeding unit 230 or the manual sheet feeding unit 235. When conveyance of the sheet S is started, the control unit 400 and the media sensor 100 wait until the sheet detection sensor 270 detects the sheet S (step S1002).

[0084] When the sheet detection sensor 270 detects the sheet S, the control unit 400 waits until a first predetermined time period has passed (step S1003), and stops conveyance of the sheet S after the first predetermined time period has passed (step S1004). The first predetermined time period is a time period from when the sheet detection sensor 270 detects the leading edge of the sheet S until the leading edge of the sheet S reaches the conveying roller pair 290.

[0085] In the case where the sheet detection sensor 270 detects the sheet S, the information processing unit 160 of the media sensor 100 waits until the second predetermined time period has passed (step S1003), and after the second predetermined time period has passed, causes the sheet pressing roller controller 271 to move the sheet pressing rollers 260 and 261 to the second position. By moving the sheet pressing rollers 260 and 261 to the second position, the sheet S abuts against the media sensor 100 (step S1005). The second predetermined time period that the information processing unit 160 waits for is longer than the first predetermined time period that the control unit 400 waits for, and is a time period from when the sheet detection sensor 270 detects the leading edge of the sheet S until the conveyance of the sheet S stops (a time period from step S1002 to step S1004).

[0086] The information processing unit 160 notifies the control unit 400 that the sheet S has abutted against the media sensor 100. In the case where the control unit 400 obtains the notification that the sheet S has abutted against the media sensor 100, the control unit 400 restarts the conveyance of the sheet S (step S1006). The control unit 400 notifies the media sensor 100 that the conveyance of the sheet S has been restarted. In the case where the information processing unit 160 obtains the notification of the restart of the conveyance of the sheet S, the information processing unit 160 starts measuring the sheet S by the ultrasonic sensor 120 and the optical sensor 150 (step S1007). When the measurement is completed, the information processing unit 160 causes the sheet pressing roller controller 271 to move the sheet pressing rollers 260 and 261 to the first position to be away from the media sensor 100 (step S1008). The information processing unit 160 notifies the control unit 400 of the measurement result (quantitative information and surface characteristic information) (step S1009).

[0087] The control unit 400 refers to the sheet type database 402 based on the acquired measurement result and determines the sheet type (step S1010). The control unit 400 determines the image forming condition based on the determined sheet type (step S1011). The control unit 400 determines whether the image forming condition needs to be changed by determining whether the determined image forming condition is different from the current image forming condition (step S1012).

[0088] When it is necessary to change the image forming condition (step S1012: Yes), the control unit 400 stops the conveyance of the sheet S again (step S1013). The control unit 400 changes the image forming condition after the conveyance of the sheet S is stopped (step S1014). When the change of the image forming condition is completed (step S1015), the control unit 400 restarts the conveyance of the sheet S (step S1016). For example, in a case where the current image forming condition is an image forming condition corresponding to a sheet of ordinary paper, and the image forming condition determined based on the measurement result of the media sensor 100 is an image forming condition corresponding to a sheet of thick coated paper, it is necessary to change the image forming condition. In this case, for example, the fixing temperature is changed from 200°C to 230°C. A period of several seconds is required during which the conveyance of the sheet S is stopped.

[0089] After resuming the conveyance of the sheet S, the control unit 400 controls image formation on the sheet S (step S1017). Note that when there is no need to change the image formation conditions (step S1012: No), the control unit 400 controls image formation without stopping the conveyance of the sheet S or changing the image formation conditions (step S1017).

[0090] Therefore, when it is necessary to change the image forming conditions, the conveyance of the sheet S is temporarily stopped and the image forming conditions are changed, so that an image is formed on the sheet S based on the optimal image forming conditions corresponding to the sheet type. Therefore, the image quality of the image printed on the sheet S is maintained. In addition to temporarily stopping the conveyance of the sheet S to change the image forming conditions, the conveyance speed of the sheet S may be slowed down to a predetermined conveyance speed to change the image forming conditions. It does not matter whether the conveyance is temporarily stopped or the conveyance speed is adjusted as long as the sheet S is conveyed to the secondary transfer unit 201D within the time period required to set the optimal image forming conditions corresponding to the sheet type.

[0091] <Modification example>

[0092] Fig.12 FIG. 2 is another process flow chart for illustrating the image forming process including the process for determining the image forming conditions. The process from starting the conveyance of the sheet S to determining the image forming conditions (steps S2001 to S2011) is similar to the process from starting the conveyance of the sheet S to determining the image forming conditions (steps S2001 to S2011). Fig.11 The processing steps from step S1001 to step S1011 are the same, so the description of these processing steps is omitted here.

[0093] After determining the image forming conditions, the control unit 400 stops conveying the sheet S (step S2012), and sets the image forming conditions (step S2013). When a predetermined time period has passed since the start of setting the image forming conditions (step S2014), the control unit 400 restarts conveying the sheet S (step S2015). The predetermined time period is the maximum time period required to change the image forming conditions. Thereafter, the control unit 400 starts image formation (step S2016).

[0094] By setting the predetermined time period from setting the image forming conditions to resuming the conveyance of the sheet S as the maximum time period required to change the image forming conditions, images can be formed using the optimal image forming conditions based on a simple sequence.

[0095] In the above description, the media sensor 100 is arranged in the image forming apparatus 201. However, as long as the media sensor 100 is arranged on the upstream side of the secondary transfer unit 201D in the conveying direction of the sheet, the media sensor 100 may be arranged outside the image forming apparatus 201. In addition, the processing performed 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 sheet type database 402 may be stored in a memory that can be accessed from the information processing unit 160. In any case, it is sufficient as long as the control unit 400 and the information processing unit 160 cooperate to perform the above-mentioned processing.

[0096] In addition, the above-mentioned image forming apparatus 201 determines control parameters such as image forming conditions by detecting the type and quantity of the sheet S based on the characteristic amount of the sheet S measured by the media sensor 100. However, the control parameters may be directly determined based on the characteristic amount. The media sensor 100 may be a device that measures physical properties of another sheet.

[0097] The operation of the sheet pressing roller 260 has been described above with respect to the optical sensor 150. The sheet pressing roller 260 is arranged so as to sandwich the ultrasonic sensor 120 between the sheet pressing roller 260 and the sheet pressing roller 261 (see Figure 5A and Figure 5B ). With this structure, when the sheet S reaches the measuring position of the media sensor 100, the sheet pressing roller 260 and the sheet pressing roller 261 press the sheet S against the media sensor 100 at the measuring position of the ultrasonic sensor 120. The ultrasonic sensor 120 transmits ultrasonic waves through the sheet S and measures the characteristic amount. The sheet pressing roller 260 and the sheet pressing roller 261 stabilize the state of the sheet S, so the characteristic amount of the sheet S can be accurately measured by the ultrasonic sensor 120.

[0098] Similarly, the sheet pressing roller 260 and the sheet pressing roller 261 are also effective in the case of using a transmission type optical sensor. Fig.13 1 is an explanatory diagram of the structure of a medium sensor using a transmission type optical sensor 150t. The transmission type optical sensor 150t transmits light through a sheet S and measures a characteristic amount. To this end, a light source 1501t and a line sensor 1502t are arranged to face each other across a conveying path. In addition, a sheet pressing roller 260 is not included, and a sheet pressing roller 262 is arranged to face a sheet pressing roller 261 to sandwich the transmission type optical sensor 150t therebetween. The sheet pressing roller 261 and the sheet pressing roller 262 stabilize the state of the sheet S, and thus the characteristic amount of the sheet S can also be accurately measured by the transmission type optical sensor 150t. In other words, in addition to directly pressing the sheet S against the optical sensor 150 by the sheet pressing roller 260, the sheet S can also be pressed against the transmission type optical sensor 150t by two rollers to stabilize the state of the sheet S. As a result, the sheet S can be stably measured even by the transmission type optical sensor 150t.

[0099] The above-described media sensor 100 is an example and is not limited to a structure including the optical sensor 150 and the ultrasonic sensor 120 . The media sensor 100 may include another sensor capable of measuring a characteristic amount of the sheet S. Furthermore, the media sensor 100 may include any one of the optical sensor 150 and the ultrasonic sensor 120 .

[0100] Furthermore, a structure in which the sheet type database 402 is included in the memory 401 of the controller 200 has been described above, but the storage location of the sheet type database 402 is not limited thereto. For example, the sheet type database 402 may be stored in the media sensor 100. In this case, the information processing unit 160 determines the type and quantity of the sheet S, and the information processing unit 160 also determines the image forming condition. Furthermore, the controller 200 including the sheet type database 402 may be placed in the cloud. In this case, when the image forming device 201 is connected to the cloud via a network, the image forming condition may be set based on the latest sheet type database or the identification algorithm.

[0101] While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments.The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

[0102] This application claims the benefit of Japanese Patent Application No. 2023-149049, filed September 14, 2023, which is hereby incorporated by reference herein in its entirety.

Claims

1. An image forming device, comprising: a conveying portion configured to convey a sheet; a measuring unit configured to measure a characteristic quantity of the sheet conveyed by the conveying unit; a detection sensor, the detection sensor being used to detect the sheet conveyed by the conveying portion; a pressing member movable between a first position separated from the measuring portion and a second position closer to the measuring portion than the first position; a moving portion configured to move the pressing member; an image forming section configured to form an image on the sheet conveyed by the conveying section based on predetermined image forming conditions; as well as Control Department, Wherein, the control unit is configured as follows: When the detection sensor detects the sheet, stopping the conveyance of the sheet by the conveying unit and controlling the moving unit to move the pressing member from the first position to the second position; controlling the conveying section to restart conveyance of the sheet in a state where the pressing member is arranged at the second position, controlling the measuring section to measure the feature amount of the sheet, and determining the predetermined image forming condition based on the measured feature amount; and The conveyance of the sheet by the conveyance section is stopped before the image forming section forms an image on the sheet to set the predetermined image forming condition in the image forming section, and conveyance of the sheet by the conveyance section is restarted to control the image forming section to form an image based on the predetermined image forming condition.

2. The image forming apparatus according to claim 1, in, The control section is configured to stop conveyance of the sheet by the conveying section when a first predetermined period of time has elapsed since the detection sensor detected the sheet, and to control the moving section to move the pressing member to the second position, wherein the control section is configured to control the measuring section to measure the feature amount of the sheet material when a second predetermined period of time has passed since the detection sensor detected the sheet material, and The second predetermined time period is longer than the first predetermined time period.

3. The image forming apparatus according to claim 2, in, The conveying section includes: a first conveying roller pair arranged on an upstream side of the measuring section along a conveying direction of the sheet, and a second conveying roller pair arranged on a downstream side of the measuring section along the conveying direction of the sheet, wherein the detection sensor is arranged between the first conveying roller pair and the measuring portion, wherein the first predetermined time period is a time period from when the detection sensor detects the leading edge of the sheet until the leading edge of the sheet reaches the second conveying roller pair, and The second predetermined time period is a time period from when the detection sensor detects the leading edge of the sheet until the conveyance of the sheet stops.

4. The image forming apparatus according to claim 1, wherein: The control section is configured to stop conveyance of the sheet by the conveyance section to update the predetermined image forming condition if the determined predetermined image forming condition is different from the current image forming condition.

5. The image forming apparatus according to claim 4, wherein: The control section is configured to resume conveyance of the sheet when updating of the predetermined image forming condition is completed.

6. The image forming apparatus according to claim 1, wherein: The control section is configured to restart conveyance of the sheet by the conveyance section if a predetermined period of time has elapsed since a start of setting of the predetermined image forming condition determined.

7. The image forming apparatus according to claim 6, wherein: The predetermined time period is a maximum time period required to change the predetermined image forming condition.

8. The image forming apparatus according to claim 1, wherein: The control section is configured to determine a sheet type of the sheet based on the feature amount of the sheet measured by the measuring section, and determine an image forming condition corresponding to the sheet type.

9. The image forming apparatus according to claim 1, wherein: The control section is configured to control the moving section to move the pressing member to the first position when measurement of the feature amount of the sheet by the measuring section is completed.

10. The image forming apparatus according to claim 9, wherein: The pressing member is a rotating member.

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