Sheet transfer device

Abstract

To solve a problem in which a decrease in the accuracy of detecting the basis weight may be reduced, and a document is not transported at an appropriate speed, thereby causing a jam.SOLUTION: The type (e.g., basis weight) of a sheet (document) is detected by burst waves of a plurality of intensities. As a result, it is possible to prevent a decrease in the accuracy of detection of the type of sheet by an ultrasonic sensor.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a sheet transport device that transports a sheet. [Background technology]

[0002] Conventionally, a technique has been disclosed in which the basis weight of a sheet being conveyed is detected by an ultrasonic sensor, and the conveying speed of the document is controlled based on the detection result (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2019-059606 A Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, the types of media have become more diverse, and there are now papers that have a high reception level for ultrasonic sensors despite being thick paper, and papers that have a low reception level for ultrasonic sensors despite being thin paper. In other words, the configuration of Patent Document 1 may result in a decrease in the accuracy of detecting basis weight. As a result, the document cannot be transported at an appropriate speed, and a jam may occur.

[0005] In view of the above-mentioned problems, an object of the present invention is to suppress a decrease in the accuracy of sheet type detection by an ultrasonic sensor. [Means for solving the problem]

[0006] In order to solve the above problems, a sheet conveying device according to the present invention comprises: A conveying means for conveying a sheet; A sensor including an output unit that outputs ultrasonic waves and a receiving unit that receives the ultrasonic waves; a memory that stores information correlating the intensity of the ultrasonic waves received by the receiving unit when the output unit outputs the ultrasonic waves of a first intensity, the intensity of the ultrasonic waves received by the receiving unit when the output unit outputs the ultrasonic waves of a second intensity, and the basis weight of the sheet; a determination unit that determines a basis weight of the sheet being conveyed by the conveying unit based on an intensity of the ultrasonic wave received by the receiving unit when the output unit outputs the ultrasonic wave of the first intensity, an intensity of the ultrasonic wave received by the receiving unit when the output unit outputs the ultrasonic wave of the second intensity, and information stored in the memory; The present invention is characterized by having the following. Effect of the Invention

[0007] According to the present invention, it is possible to suppress a decrease in the accuracy of detection of the type of sheet by the ultrasonic sensor. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram illustrating a configuration of an image forming apparatus. [Diagram 2] FIG. 2 is a block diagram showing an example of a control configuration of the image forming apparatus. [Diagram 3] 13A and 13B are diagrams illustrating signals received by the double feed detection sensor T2. [Figure 4] 11 is a diagram showing the relationship between the wave number of a burst wave output from a double-feed detection sensor T1 and the amplitude of a signal corresponding to ultrasonic waves received by a double-feed detection sensor T2. FIG. [Diagram 5] 13 shows the relationship between the basis weight and the reception level of the double feed detection sensor T2 for each wave number of the burst wave. [Figure 6] 1A and 1B are diagrams illustrating an operation of irradiating ultrasonic waves onto paper. [Figure 7] This figure shows the reception level when the burst wave has four waves, when the burst wave has three waves, and when the burst wave has two waves, for each corresponding sheet. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Preferred embodiments of the present invention will be described below with reference to the drawings. However, the shapes of the components and their relative positions described in the embodiments may be changed as appropriate depending on the configuration of the device to which the present invention is applied and various conditions, and the scope of the present invention is not intended to be limited to the following embodiments.

[0010] [First embodiment] [Image forming device] 1 is a cross-sectional view showing the configuration of a color electrophotographic copying machine (hereinafter referred to as an image forming apparatus) 100 used in this embodiment. Note that the image forming apparatus is not limited to a copying machine, and may be, for example, a facsimile machine, a printing machine, a printer, etc. Furthermore, the recording method is not limited to an electrophotographic method, and may be, for example, an inkjet method, etc. Furthermore, the type of the image forming apparatus may be either a monochrome type or a color type.

[0011] The configuration and functions of the image forming apparatus 100 will be described below with reference to Fig. 1. As shown in Fig. 1, the image forming apparatus 100 has an original feeding device 201 as a sheet transport device, an original reading device 200 including a reading device 202, and an image printing device 301.

[0012] <Document reader> The position in the width direction (a direction intersecting the feeding direction in which the document P is fed) of the document P loaded on the document loading section 2 of the document feeding device 201 is regulated by a pair of regulating sections 1 provided on the document loading section 2. The pair of regulating sections 1 are configured to be movable in accordance with the width of the document.

[0013] The originals P are fed one by one by the pickup roller 3, and then transported further downstream by the feed roller 4. A separation roller 5 that is in pressure contact with the feed roller 4 is provided at a position opposite to the feed roller 4. The separation roller 5 is configured to rotate when a load torque equal to or greater than a predetermined torque is applied to the separation roller 5, and has the function of separating the originals that are fed in a two-sheet overlapping state.

[0014] The pickup roller 3 and the feed roller 4 are connected by a swing arm 12. The swing arm 12 is supported by the rotation shaft of the feed roller 4 so as to be rotatable around the rotation shaft of the feed roller 4.

[0015] The document P fed by the feed roller 4 is further conveyed downstream by the conveying roller 6. Downstream of the conveying roller 6, there are provided double-feed detection sensors T1 and T2 that detect whether or not two or more documents have been conveyed in an overlapping state (double-feed). The double-feed detection sensor is, for example, an ultrasonic sensor, and an ultrasonic transmission sensor T1 as an output unit transmits ultrasonic waves, and an ultrasonic reception sensor T2 as a receiving unit receives the ultrasonic waves.

[0016] The document P is discharged onto a discharge tray 10 by a discharge roller 11 .

[0017] The reading device 202 is provided with a reading unit 16 that reads an image of the first side of a document being conveyed. The reading unit 16 has an LED 110, an image sensor 111, and an optical component group 112. The image sensor 111 has a plurality of light receiving elements that receive R (red), G (green), and B (blue) light in the main scanning direction (corresponding to the width direction perpendicular to the conveying direction of the document). The reading unit 16 reads an image of the front side (first side) of the document as follows. Specifically, the LED 110 as a light source irradiates (emits) light onto the front side of the document being conveyed through the reading glass 108. The optical component group 112 guides the reflected light from the document received through the reading glass 108 to the image sensor 111. The image sensor 111 outputs analog image data based on the received light. The image sensor 111 simultaneously reads one line of the image in the main scanning direction. Therefore, by reading one line of image multiple times with the image sensor 111 while conveying the document, the image sensor 111 can output image data including the entire document.

[0018] Further, the document feeder 201 is provided with a reading unit 17 that reads an image on the second side of the document being conveyed. The configuration of the reading unit 17 is similar to that of the reading unit 16, and therefore a description thereof will be omitted.

[0019] Methods for reading an original include a skimming method and a pressure plate reading method. The skimming method is a method for reading an image of an original transported by the above-mentioned method. The pressure plate reading method is a method for reading an image of an original placed on the original table glass 214 of the reading device 202 by the reading unit 16 moving at a constant speed in the sub-scanning direction (rightward in FIG. 1) corresponding to the transport direction in which the original is transported. Usually, images of sheet-like originals are read by the skimming method, and images of bound originals such as books and pamphlets are read by the pressure plate reading method.

[0020] The document feeder 201 is rotatable relative to the reader 202 between an open position where the document glass 214 is exposed and a closed position where the document glass 214 is covered by a pressure plate 18. The document feeder 201 has a pressure plate that presses the document placed on the document glass 214 toward the document glass 214 in the closed position. In the pressure plate reading method, the document placed on the document glass 214 is read by the reader 16 that moves in the sub-scanning direction.

[0021] <Image printing device> A sheet storage tray 18 for storing recording media is provided inside the image printing device 301. Note that the recording media are those on which an image is formed by the image forming device, and include, for example, paper, resin sheets, cloth, OHP sheets, labels, etc.

[0022] The recording medium stored in the sheet storage tray 18 is sent out by a pickup roller 19, and is sent to a registration roller 20 by conveyance rollers 39, 40, 41, 42, etc.

[0023] The image printing device 301 is also provided with a manual feed tray 44 on which recording media are stacked. The recording media stacked on the manual feed tray 44 are sent out by a pickup roller 43, and are then sent to the registration rollers 20 by a transport roller 42 and the like.

[0024] The leading edge of the recording medium conveyed by the pre-registration roller 37 hits the registration roller 20. As a result, a loop is formed in the recording medium between the registration roller 20 and the pre-registration roller 37, and the skew of the recording medium is corrected (reduced).

[0025] The image signal output from the document reading device 200 is input for each color component to optical scanning devices 21Y, 21M, 21C, and 21K including a semiconductor laser and a polygon mirror. Specifically, the image signal for yellow output from the document reading device 200 is input to optical scanning device 3Y, and the image signal for magenta output from the document reading device 200 is input to optical scanning device 3M. In addition, the image signal for cyan output from the document reading device 200 is input to optical scanning device 3C, and the image signal for black output from the document reading device 200 is input to optical scanning device 3K. In the following description, a configuration for forming a yellow image will be described, but the same configuration applies to magenta, cyan, and black.

[0026] The outer peripheral surface of the photosensitive drum 22Y is charged by the charger 23Y. After the outer peripheral surface of the photosensitive drum 22Y is charged, a laser beam corresponding to an image signal input from the document reading device 200 to the optical scanning device 21Y is irradiated onto the outer peripheral surface of the photosensitive drum 22Y from the optical scanning device 21Y via an optical system including a polygon mirror and a mirror. As a result, an electrostatic latent image is formed on the outer peripheral surface of the photosensitive drum 22Y.

[0027] Next, the electrostatic latent image is developed by toner in a developing device 24Y as a developing unit, and a toner image is formed on the outer peripheral surface of the photosensitive drum 22Y. The toner image formed on the photosensitive drum 22Y is transferred to a transfer belt 27 as an intermediate transfer body by a transfer roller 25Y provided at a position facing the photosensitive drum 22Y. Note that the toner remaining on the outer peripheral surface of the photosensitive drum 22Y after the toner image is transferred to the transfer belt 27 is collected by a cleaning unit 26Y.

[0028] The yellow, magenta, cyan, and black toner images transferred onto the transfer belt 27 are transferred onto the recording medium by the pair of transfer rollers 28. A high voltage is applied to the pair of transfer rollers 28, and the toner images are transferred onto the recording medium due to the high voltage. The registration rollers 20 feed the recording medium into the pair of transfer rollers 28 in accordance with the timing of this transfer.

[0029] As described above, the recording medium onto which the toner image has been transferred is sent to the fixing device 29 as a fixing section, and the toner image is fixed to the recording medium by heating and pressurizing the recording medium by the fixing device 29. In this manner, an image is formed on the recording medium by the image forming apparatus 100.

[0030] When an image is formed in a single-sided printing mode, the recording medium that has passed through the fixing device 29 is discharged to a discharge tray 31 by a paper discharge roller 30. When an image is formed in a double-sided printing mode, the fixing device 29 performs a fixing process on the first side of the recording medium, and then the recording medium is conveyed to a reversing path 32 by a reversing roller 38. The recording medium conveyed to the reversing path 32 is reversed between the first side and the second side by the reversing roller 38 and conveyed to a conveying guide provided with conveying rollers 33, 34, 35, and 36. The recording medium is conveyed again to the registration roller 20 by the conveying rollers 33, 34, 35, and 36, and an image is formed on the second side of the recording medium by the method described above. Thereafter, the recording medium is discharged to a paper discharge tray 31 by a paper discharge roller 30.

[0031] The configuration and functions of image forming apparatus 100 have been described above.

[0032] [Control configuration] <Control configuration of image printing device> 2 is a block diagram showing an example of a control configuration of the image forming apparatus 100. First, the control configuration of the image printing apparatus 301 will be described.

[0033] 2, the system controller 151 includes a CPU 151a, a ROM 151b, and a RAM 151c. The system controller 151 is also connected to an analog-to-digital (A / D) converter 153, a high voltage control unit 155, a motor control device 600, sensors 159, and an AC driver 160. The system controller 151 is capable of transmitting and receiving data and commands to and from each of the units connected thereto.

[0034] The CPU 151a reads out and executes various programs stored in the ROM 151b to execute various sequences related to a predetermined image formation sequence.

[0035] The RAM 151c is a storage device and stores various data such as set values ​​for the high voltage control unit 155, command values ​​for the motor control device 600, and the like.

[0036] System controller 151 receives signals from sensors 159, and sets the set value of high voltage control unit 155 based on the received signals.

[0037] A high voltage control unit 155 supplies a necessary voltage to a high voltage unit 156 (charger 310, developer 314, transfer charger 315, etc.) in accordance with a set value set by the system controller 151.

[0038] The motor control device 600 controls the motor 509 that drives a load provided in the image printing device 301 in response to a command output from the CPU 151a.

[0039] The A / D converter 153 receives a detection signal detected by a thermistor 154 for detecting the temperature of the fixing heater 161, converts the detection signal from an analog signal to a digital signal, and transmits the digital signal to the system controller 151. The system controller 151 controls the AC driver 160 based on the digital signal received from the A / D converter 153. The AC driver 160 controls the fixing heater 161 so that the temperature of the fixing heater 161 becomes a temperature required for performing the fixing process. The fixing heater 161 is a heater used in the fixing process, and is included in the fixing unit 318.

[0040] As described above, the system controller 151 controls the operation sequence of the image forming apparatus 100 .

[0041] <Control configuration of document reading device> Next, a description will be given of a control configuration of the document reading device 200. The CPU 401 controls the document reading device 200 by executing a program stored in the non-volatile memory 402.

[0042] The operation unit 403 provides a user interface. The CPU 401 controls the operation unit 403 so as to display, on a display unit provided in the operation unit 403, an operation screen for a user to perform reading settings when reading an image of a document by the document reading device 200. The CPU 401 receives information set by the user from the operation unit 403, and controls the document reading device 20 based on the information.

[0043] Furthermore, the CPU 401 determines whether or not the documents are being fed in multiples based on the multiple feed detection sensors T1 and T2.

[0044] The system controller 151 transmits information indicating the status of the image forming apparatus to the operation unit 403. The information indicating the status of the image forming apparatus is, for example, information regarding the number of images formed, the progress of the image forming operation, and information regarding sheet jams and multiple feeds in the image printing device 301 and the document feeding device 201. The operation unit 403 displays the information received from the system controller 151 on the display unit.

[0045] The image data output by the reading units 16 and 17 is input to the image processing unit 404. The image processing unit 404 converts the analog image data into digital image data. The digital image data has a higher numerical value as the intensity of the reflected light increases. This numerical level is hereinafter referred to as a luminance value. The image processing unit 404 performs corrections such as known shading corrections on the image data.

[0046] <Double feed detection sensor> Fig. 3 is a diagram showing signals received by the multi-feed detection sensor T2. Fig. 3(a) is a diagram showing a signal received by the multi-feed detection sensor T2 when there is no document. Fig. 3(b) is a diagram showing a signal received by the multi-feed detection sensor T2 when one document is being transported. Fig. 3(c) is a diagram showing a signal received by the multi-feed detection sensor T2 when two documents are being fed in a overlapping manner.

[0047] As shown in Fig. 3(b), the amplitude of the signal received by the multi-feed detection sensor T2 when one document is being conveyed is smaller than the amplitude of the signal received by the multi-feed detection sensor T2 when no document is being conveyed. This is because the signal (ultrasound) output from the multi-feed detection sensor T1 is attenuated by the document. Also, as shown in Fig. 3(c), the amplitude of the signal received by the multi-feed detection sensor T2 when two documents are being conveyed is smaller than the amplitude of the signal received by the multi-feed detection sensor T2 when one document is being conveyed. This is because the signal (ultrasound) output from the multi-feed detection sensor T1 is further attenuated by the two documents.

[0048] FIG. 4 is a diagram showing the relationship between the wave number of the burst wave output from the double feed detection sensor T1 and the amplitude of the signal corresponding to the ultrasonic wave received by the double feed detection sensor T2. The double feed detection sensor T1 has a built-in piezoelectric element. By inputting a burst wave from the CPU 401 to the double feed detection sensor T1, electrical energy is applied to the piezoelectric element, and ultrasonic waves are emitted. Increasing the wave number of the burst wave corresponds to increasing the energy applied to the piezoelectric element. Therefore, when the wave number of the burst wave is increased, the energy of the ultrasonic wave is increased, and the level of the signal received by the double feed detection sensor T2 increases. However, when the wave number is increased beyond a certain value, the level of the received signal no longer increases in proportion to the wave number and becomes saturated. This is because the limit of the performance that the internal piezoelectric element can vibrate has been reached.

[0049] FIG. 5(a) shows the relationship between the basis weight (or paper thickness) and the reception level of the double feed detection sensor T2 for each wave number of the burst wave when one document is conveyed.

[0050] When using the double feed detection sensors T1 and T2 for double feed detection, unless the burst wave is set to 5 waves and the energy for driving the double feed detection sensor T1 is increased, it becomes difficult to see the difference in the reception level during double feed and during normal transport (single transport). Therefore, the number of burst waves is set to 5 waves.

[0051] On the other hand, when the double feed detection sensors T1 and T2 are used to detect the basis weight of the document, it becomes necessary to change the number of waves of the burst wave for the following reasons. Specifically, when the number of waves of the burst wave is set to 5 waves, if the paper has a large basis weight (thick paper), the difference in the reception level will be relatively linear. In other words, by reading the reception level, it is possible to determine which basis weight of paper is being conveyed. However, when the basis weight is below a certain value, the energy of the ultrasonic waves irradiated to the paper is too strong, and the obtained reception level is saturated at the limit value that the signal can swing. In other words, it is not possible to determine which basis weight of paper is small from the reception level. However, as mentioned above, by lowering the number of waves of the burst wave, the energy of the ultrasonic waves irradiated to the paper is reduced, so that a difference in the reception level will appear even for paper in a small basis weight area. When the burst wave is set to 3 waves, the reception level of paper in a small basis weight area will be linearly different for each basis weight compared to 5 waves.

[0052] Figure 5(b) shows the reception level for single feed and double feed when the basis weight is changed under the condition that the wave number of the burst wave is fixed. In the case of double feed detection, the purpose is to detect whether or not a double feed has occurred. In the case of a double feed, the reception level is constant regardless of the basis weight. In contrast, in the case of single feed, if you try to detect it by setting the wave number of the burst wave to a small number, the reception level will be low and the latitude to the threshold will be small. In other words, there is a high risk of falsely detecting a double feed even when a single feed is actually occurring.

[0053] For these reasons, if the data on the reception level of the double-feed detection is used to detect the basis weight, it becomes difficult to distinguish between paper in low basis weight areas. Therefore, it becomes necessary to control the basis weight detection and the double-feed detection by changing the wave number of the burst wave.

[0054] Next, a method of detecting double feed and basis weight using the double feed detection sensors T1 and T2 will be described with reference to FIG.

[0055] For example, in the case of general paper, the reception level decreases as the basis weight increases. However, there are some specific examples of paper that have a large basis weight and should be treated as thick paper, but have a high reception level. When detecting the basis weight of such paper, if the reception level in the database that is already available is applied, the paper will be recognized as thin paper and will not be treated as thick paper. Therefore, in this invention, a method for detecting thick paper with a large basis weight will be described with reference to the drawings.

[0056] Fig. 6(a) is a diagram showing the paper transport direction and the operation of irradiating ultrasonic waves to the paper. Fig. 6(b) is a diagram showing the part irradiated for double feed detection and the part irradiated for basis weight detection when ultrasonic waves are irradiated to the paper as in the diagram of Fig. 6(a). Fig. 6(c) is a diagram showing the burst wave drive and the received waveform of the ultrasonic waves caused by the drive when double feed detection and basis weight detection are alternately performed by ultrasonic transmission sensor T1 and ultrasonic reception sensor T2.

[0057] Double feed detection is performed at the leading edge of the paper, and if double feed is detected, the transport of the paper must be stopped immediately. Since the basis weight is a parameter that should be measured when it is determined that double feed is not occurring, it must be measured after double feed detection. However, in the case of paper basis weight, the basis weight does not change significantly within a single sheet of paper. Therefore, basis weight detection does not need to be performed all the time from the leading edge to the trailing edge of the paper. Therefore, basis weight detection is performed at several locations (two or three locations) at the leading edge of the paper. The reason for obtaining data at multiple locations is to process the data and determine the basis weight while taking into account the variation in the detection data per location. In this way, by performing basis weight detection several times at the leading edge of the paper and lowering the wave number of the burst wave during basis weight detection compared to the wave number during double feed detection, the reception level characteristics for each basis weight can be obtained.

[0058] Next, how to detect the basis weight will be explained with reference to Fig. 10. Fig. 10 shows the signal level received by the ultrasonic receiving sensor T2 for each paper basis weight as an AD value. A high AD value indicates that the amplitude (reception level) of the received signal is large, and a low AD value indicates that the reception level is small.

[0059] Next, a method for identifying the basis weight will be described. First, the data in Fig. 7 is stored in the non-volatile memory 402. The data in Fig. 7 is a table showing the relationship between the reception level when the burst wave has four waves, the reception level when the burst wave has three waves, and the reception level when the burst wave has two waves, and the type of paper.

[0060] When the basis weight detection operation is performed, the reception level of the double feed detection sensor T2 is detected. Then, the CPU 401 searches for where the obtained value is located in the AD value range allocation for each type of sheet shown in Fig. 7. Then, the range of the transported paper is specified from the searched AD value range.

[0061] A specific example will be described. Assume that the detected value for 4 waves is 200, the value for 3 waves is 155, and the value for 2 waves is 120. The CPU 402 searches for the range corresponding to the above reception level characteristics from the data of FIG. 7 stored in the non-volatile memory 402. In the data this time, the range is 120 to 179 gsm, so it is determined that paper in the above range has been passed. However, consider a case where the result of reading the reception level of special paper specified by the user is that the value for 4 burst waves is 210, the value for 3 burst waves is 135, and the value for 2 burst waves is 90. In this case, there is no paper in the range with that tendency in the storage area of ​​the non-volatile memory 402. Therefore, in this case, the characteristics of the values ​​for each number of burst waves are stored in the custom storage area of ​​the storage area of ​​the non-volatile memory 402. Then, when the same characteristic value as above is obtained next time, the process is performed to determine that the paper is "user-defined paper." Furthermore, if it is determined that the basis weight data stored in the non-volatile memory 402 as the user-specified paper exceeds a predetermined value (processing in the thick paper mode is required), the document is transported in the thick paper mode without user settings.

[0062] As described above, in this embodiment, the type (e.g., basis weight) of a sheet (original) is detected (determined) by burst waves of multiple intensities. As a result, it is possible to suppress a decrease in the detection accuracy of the sheet type by the ultrasonic sensor.

[0063] The method for detecting the type of sheet in this embodiment may be used in the image printing device 301. That is, the method for detecting the type of sheet in this embodiment may be used in a sheet conveying device that conveys a sheet. [Explanation of symbols]

[0064] 6 Transport roller 401 CPU 402 Non-volatile memory T1, T2 double feed detection sensor

Claims

1. A conveying means for conveying a sheet; A sensor including an output unit that outputs ultrasonic waves and a receiving unit that receives the ultrasonic waves; a memory in which information is stored that associates the intensity of the ultrasonic waves received by the receiving unit when the output unit outputs the ultrasonic waves of a first intensity, the intensity of the ultrasonic waves received by the receiving unit when the output unit outputs the ultrasonic waves of a second intensity, and the type of the sheet; a determination unit that determines the type of the sheet being conveyed by the conveying unit based on the intensity of the ultrasonic waves received by the receiving unit when the output unit outputs the ultrasonic waves of the first intensity, the intensity of the ultrasonic waves received by the receiving unit when the output unit outputs the ultrasonic waves of the second intensity, and information stored in the memory; A sheet conveying device comprising:

2. 2. The sheet transport device according to claim 1, wherein the transport means transports the sheet at a speed corresponding to the type of the sheet determined by the determination means.

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