Patent Publication Number: US-10766726-B2

Title: Sheet conveying device for conveying sheets such as documents, recording paper, and the like

Description:
INCORPORATION BY REFERENCE 
     This application is based on and claims the benefit of priority from Japanese Patent Application No. 2018-009575 filed on Jan. 24, 2018, the contents of which are hereby incorporated by reference. 
     BACKGROUND 
     The present disclosure relates to a sheet conveying device that conveys sheets such as documents, recording paper and the like. 
     Conventionally, an image forming apparatus such as a copying machine, printer and the like includes a sheet conveying device for feeding recording paper as a sheet, one by one to an image-forming unit. In such a sheet conveying devide, a technique for detecting overlapped feeding using a sensor such as an ultrasonic sensor for detecting overlapped feeding has been proposed. 
     SUMMARY 
     The sheet conveying device according to the present disclosure is a sheet conveying device that includes a paper-supply roller for feeding sheets one by one from a paper-supply unit to a paper-conveyance path, and a conveying-roller for conveying sheets fed to the paper-conveyance path by the paper-supply roller. The sheet conveying device further includes a sheet-detecting unit, an overlapped-feeding-detecting unit, an overlapped-feeding-distance-calculating unit, and a conveyance-control unit. The sheet-detecting unit detects a leading edge position of a sheet. The overlapped-feeding-detecting unit detects overlapped feeding of sheets. The overlapped-feeding-distance-calculating unit, based on the detection results of the sheet-detecting unit and the overlapped-feeding-detecting unit, calculates an overlapped-feeding distance in which sheets are overlapped. The conveyance-control unit causes the paper-supply roller to stop at a timing when a position separated a set length in the sheet-conveyance direction from a sheet trailing edge reaches the paper-supply roller. The conveyance-control unit, in a case where detection of overlapped feeding by the overlapped-feeding-detecting unit occurs a plurality of times, extends the set length based on the overlapped-feeding distance. 
     Moreover, the sheet conveying device according to the present disclosure is a sheet conveying device the includes a paper-supply roller for feeding sheets one by one from a paper-supply unit to a paper-conveyance path, and a conveying-roller for conveying sheets fed to the paper-conveyance path by the paper-supply roller. The sheet conveying device further includes a sheet-detecting unit, an overlapped-feeding-detecting unit, an overlapped-feeding-distance-calculating unit, and a conveyance-control unit. The sheet-detecting unit detects a leading edge position of a sheet. The overlapped-feeding-detecting unit detects overlapped-feeding of sheets. The overlapped-feeding-distance-calculating unit, based on the detection results of the sheet-detecting unit and the overlapped-feeding-detecting unit, calculates an overlapped-feeding distance in which sheets are overlapped. The conveyance-control unit causes the paper-supply roller to stop at a timing when a position separated a set length in the sheet-conveyance direction from a sheet trailing edge reaches the paper-supply roller. The conveyance-control unit, in a case where detection of overlapped-feeding by the overlapped-feeding-detecting unit occurs a plurality of times, changes the set length to the overlapped-feeding distance. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic cross-sectional view of an embodiment of an image forming apparatus according to the present disclosure. 
         FIG. 2  is a block diagram illustrating a schematic configuration of the image forming apparatus illustrated in  FIG. 1 . 
         FIG. 3A  is an explanatory diagram for explaining the sheet detection operation by the ultrasonic sensor in  FIG. 1 . 
         FIG. 3B  is an explanatory diagram for explaining the sheet detection operation by the ultrasonic sensor in  FIG. 1 . 
         FIG. 4A  is an explanatory view for explaining sheet conveyance control by the conveyance-control unit illustrated in  FIG. 2 . 
         FIG. 4B  is an explanatory view for explaining sheet conveyance control by the conveyance-control unit illustrated in  FIG. 2 . 
         FIG. 4C  is an explanatory view for explaining sheet conveyance control by the conveyance-control unit illustrated in  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     In the following, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that in the following embodiments, the same reference numerals are given to the configurations showing similar functions. 
     As illustrated in  FIG. 1 , the image forming apparatus  1  of the present embodiment includes a document-reading unit  2 , a document-feeding unit  3 , a main unit  4 , and an operation unit  5 . The document-reading unit  2  is arranged on the upper portion of the main unit  4 , and the operation unit  5  is arranged on the upper front side of the main unit  4 . 
     The operation unit  5  is provided with a liquid-crystal display unit and various operation buttons. A user performs various settings such as an operating mode or the like by operating the operation unit  5  and inputting instructions. In doing so, a copying operation for recording a document image on recording paper, a network transmitting operation for transmitting a document image via a network such as the Internet or the like, and an accumulating operation for storing a document image in a database are executed. 
     The document-reading unit  2  is a scanner that reads a document image by irradiating light onto a document fed by the document-feeding unit  3  or a document placed on a platen glass, and receiving reflected light or the like from that document. 
     The document-feeding unit  3  sequentially feeds set documents one by one by a document-conveying mechanism and feeds them to a document reading position. 
     The main unit  4  includes an image-forming unit  6  and a sheet conveying device  7  that conveys recording paper as sheets. 
     The image-forming unit  6  includes, for example, a photosensitive drum, an optical unit, a developing unit, a transfer unit, and a fixing device. The optical unit forms an electrostatic latent image on the surface of the photosensitive drum based on a document image. The developing unit forms a toner image by causing toner to adhere to the surface of the photosensitive drum on which the electrostatic latent image is formed. The transfer unit transfers the toner image on the photosensitive drum to recording paper. The fixing device heats and fixes the toner image on the recording paper. 
     The sheet conveying device  7  includes a paper-supply unit  71 , a paper-supply roller  72 , a paper-conveyance path  73 , and a conveying roller  74 . The paper-supply unit  71  is a paper-supply cassette in which a plurality of sheets of recording paper is stored, and the paper-supply roller  72  feeds the recording paper one by one from the paper-supply unit  71  to the paper-conveyance path  73 . The recording paper fed to the paper-conveyance path  73  by the paper-feeding roller  72  is conveyed to the image-forming unit  6  by the conveying roller  74 . Then, the recording paper on which recording is performed by the image-forming unit  6  is discharged to a discharge space formed between the document-reading unit  2  and the main unit  4 . 
     An ultrasonic sensor  8  is arranged on the downstream side in the sheet-conveyance direction of the paper-feeding roller  72 , or in other words, is arranged in the paper-conveyance path  73  between the paper-feeding roller  72  and the conveying roller  74 . The ultrasonic sensor  8  includes a transmitting unit  8   a  for transmitting ultrasonic waves and a receiving unit  8   b  for receiving ultrasonic waves from the transmitting unit  8   a . The transmitting unit  8   a  and the receiving unit  8   b  are arranged on both sides in the vertical direction of the paper-conveyance path  73 . 
       FIG. 2  is a block diagram illustrating a schematic configuration of the image forming apparatus  1 . The above-described document-reading unit  2 , document-feeding unit  3 , operation unit  5 , image-forming unit  6 , and the sheet conveying device  7  are connected to a main-control unit  9 , and the operation is controlled by the main-control unit  9 . Moreover, an image-processing unit  10  and a storage unit  11  are connected to the main-control unit  9 . 
     The main-control unit  9  is an information-processing unit such as a microcomputer or the like that includes a CPU (central processing unit), a ROM (read only memory), a RAM (random access memory), and the like. The ROM stores a control program for performing operation control of the image forming apparatus  1 . The CPU of the main-control unit  9  performs overall control of the apparatus by reading the control program stored in the ROM and developing the control program in the RAM. 
     The image-processing unit  10  is a unit that performs specific image processing on image data; and, for example, performs image processing such as enlargement/reduction processing, gradation adjustment, density adjustment and the like. 
     The storage unit  11  is a storage unit such as a semiconductor memory, an HDD (hard disk drive), or the like, and together with storing image data acquired by reading a document by the document-reading unit  2 , stores various kinds of management information. 
     The sheet conveying device  7  includes a paper-supply motor  75  for rotating the paper-supply roller  72 , a conveying motor  76  for rotating the conveying roller  74 , and a conveyance-control unit  77  for controlling the driving of the paper-supply motor  75  and the conveying motor  76 . 
     The conveyance-control unit  77  is an arithmetic processing circuit such as a microcomputer or the like including a CPU (central processing unit), a ROM (read only memory), a RAM (random access memory), and the like. The ROM stores a control program for performing operation control of the sheet conveying device  7 . The CPU of the conveyance-control unit  77 , by reading the control program stored in the ROM and developing the control program in the RAM, controls the conveyance of sheets by driving the paper-supply motor  75  and the conveying motor  76  according to various instruction information from the main-control unit  9 . 
     In addition, the ultrasonic sensor  8  is connected to the conveyance-control unit  77 . Then, based on the output from the ultrasonic sensor  8 , the conveyance-control unit  77  functions as a sheet-detecting unit  771  for detecting the leading edge of a sheet of recording paper, an overlapped-feeding-detecting unit  772  for detecting overlapped feeding, and a overlapped-feeding-distance-calculating unit  773  for calculating an overlapped-feeding distance. 
     In the output from the ultrasonic sensor  8 , when there is no sheet between the transmitting unit  8   a  and the receiving unit  8   b , attenuation of the ultrasonic waves received by the receiving unit  8   b  is a minimum and is a specific first output level. Then, as illustrated in  FIG. 3A , when a sheet is in a state of being properly conveyed and there is one sheet between the transmitting unit  8   a  and the receiving unit  8   b , the attenuation of the ultrasonic waves received by the receiving section  8   b  becomes large, and the output level becomes a second output level that is less than the first output level when there is no sheet. Furthermore, as illustrated in  FIG. 3B , when a state of overlapped feeding occurs and there is a plurality of sheets between the transmitting unit  8   a  and the receiving unit  8   b , the attenuation of the ultrasonic waves received by the receiving unit  8   b  becomes even larger, and the output level becomes a third output level that is less than the second output level when there is one sheet. 
     Therefore, as illustrated in  FIG. 3A , the sheet-detecting unit  771  compares the output from the ultrasonic sensor  8  with a first threshold value set to a value between the first output level and the second output level, and detects the arrival of the leading edge of a sheet at the timing when the output from the ultrasonic sensor  8  falls below the first threshold value. 
     Moreover, as illustrated in  FIG. 3B , the overlapped-feeding-detecting unit  772  compares the output from the ultrasonic sensor  8  with a second threshold set to a value between the second output level and the third output level, and when the output from the ultrasonic sensor  8  falls below the second threshold value, overlapped feeding of sheets is detected. 
     When overlapped feeding is detected by the overlapped-feeding-detecting unit  772 , the overlapped-feeding-distance-calculating unit  773  measures the time from the detection of the leading edge of the sheet by the sheet-detecting unit  771  to the detection of the overlapped feeding by the overlapped-feeding-detecting unit  772 . Then, the overlapped-feeding-distance-calculating unit  773  calculates a conveyance distance from the measured time and the conveyance speed (time×conveyance speed=conveyance distance) and calculates the overlapped-feeding distance (D mm) in which sheets overlap by subtracting the conveyance length from the paper length (overlapped-feeding distance=paper length−conveyance distance). Note that the paper length is the length in the sheet conveyance direction of the recording paper stored in the paper-supply unit  71 , and is a value of a setting inputted from the operation unit  5 , or a value grasped by a paper-detecting sensor or the like provided in the paper-supply unit  71 . 
     Next, sheet conveyance control by the conveyance-control unit  77  will be described in detail with reference to  FIGS. 4A to 4C . 
     When conveyance of recording paper is instructed from the main-control unit  9 , the conveyance-control unit  77  causes the paper-supply roller  72  to rotate by driving the paper-supply motor  75 , and feeds recording paper from the paper-supply unit  71  to the paper-conveyance path  73 . At the same time as this, the conveyance-control unit  77  causes the conveying roller  74  to rotate by driving the conveying motor  76 , and conveys the recording paper toward the image-forming unit  6 . In order to unify paper behavior while conveying the recording paper, rotation control of the paper-supply roller  72  and the conveying roller  74  is determined according to the paper type, size, and the like that are prescribed in advance. 
     Then, as illustrated in  FIG. 4A , the conveyance-control unit  77 , by causing the rotation of the paper-supply roller  72  to stop before the trailing edge of the recording paper passes, suppresses overlapped feeding of the recording paper by increasing the conveyance load in the vicinity of the trailing edge of the recording paper. The timing for stopping the paper-supply roller  72  is set with reference to the trailing edge of the recording paper, and the conveyance-control unit  77  causes the paper-supply roller  72  to stop at timing when a position separated by a set distance in the sheet-conveyance direction from the trailing edge of the recording paper reaches the paper-supply roller  72 . Incidentally, it should be noted that the set length is set to the preset initial value=X mm in the case where the sheet is normally conveyed. 
     A description will be given of a case where detection of overlapped feeding by the overlapped-feeding-detecting unit  772  occurs a plurality of times under the same conveyance conditions (paper size, cassette paper-supply tray, paper type, and the like). In this case, as illustrated in  FIG. 4B , the conveyance-control unit  77  suppresses overlapped feeding of the recording paper by further increasing the conveyance load in the vicinity of the trailing edge of the recording paper by changing the set length to a value (X mm+α mm) obtained by adding an adjustment value (α mm) to the initial value (X mm). 
     The conveyance-control unit  77  determines the adjustment value (α mm) based on the overlapped-feeding distance calculated by the overlapped-feeding-distance-calculating unit  773 . The overlapped-feeding-distance-calculating unit  773  sets the adjustment value (α mm) to be longer as the overlapped-feeding distance becomes longer. The adjustment value (α mm) may be calculated by multiplying the overlapped-feeding distance by a coefficient, or it may be determined in stages according to the overlapped-feeding distance. 
     In addition, in the case where the detection of overlapped feeding by the overlapped-feeding-detecting unit  772  occurs a plurality of times under the same conveyance conditions (paper size, cassette paper-supply tray, paper type, and the like), the conveyance-control unit  77 , as illustrated in  FIG. 4C , may change the set length to the overlapped-feeding distance (D mm). 
     Incidentally, in the present embodiment, configuration is such that the position of the leading edge of the sheet and overlapped feeding are detected by the output of the ultrasonic sensor  8 , however, configuration is also possible in which the position of the leading edge of the sheet and the overlapped feeding are detected by the output of an optical sensor. In this case, a light-emitting unit and a light-receiving unit are arranged so as to be on both sides in the vertical direction of document conveying path  73 , and the position of the leading edge of the sheet and overlapped feeding are detected by the change in the light amount when a light emitted from the light-emitting unit passes through the sheet. 
     As described above, according to this embodiment, a sheet conveying device  7  includes a paper-supply roller  72  for feeding sheets one by one from a paper-supply unit  71  to a paper-conveyance path  73 , and a conveying-roller  74  for conveying sheets fed to the paper-conveyance path  73  by the paper-supply roller  72 ; and further includes: a sheet-detecting unit  771  for detecting the leading edge position of a sheet; an overlapped-feeding-detecting unit  772  for detecting overlapped feeding of sheets; an overlapped-feeding-distance-calculating unit  773  that, based on the detection results of the sheet-detecting unit and the overlapped-feeding-detecting unit, calculates an overlapped-feeding distance in which sheets are overlapped; and a conveyance-control unit  77  that causes the paper-supply roller  72  to stop at a timing when a position separated a set length in the sheet-conveyance direction from a sheet trailing edge reaches the paper-supply roller  72 ; wherein, the conveyance-control unit  77 , in a case where detection of overlapped feeding by the overlapped-feeding-detecting unit  772  occurs a plurality of times, extends the set length based on the overlapped-feeding distance. More specifically, the conveyance-control unit  77  changes the set length to a value obtained by adding an adjustment value based on the overlapped-feeding distance to the initial value. 
     With this configuration, the conveyance load in the vicinity of the trailing edge of the recording paper can be further increased in accordance with the detection of overlapped feeding, so it is possible to suppress the recurrence of overlapped feeding, and thus it is possible to improve the down time of an apparatus due to the frequent occurrence of overlapped feeding. 
     Moreover, according to this embodiment, a sheet conveying device  7  includes a paper-supply roller  72  for feeding sheets one by one from a paper-supply unit  71  to a paper-conveyance path  73 , and a conveying-roller  74  for conveying sheets fed to the paper-conveyance path  73  by the paper-supply roller  72 ; and further includes: a sheet-detecting unit  771  for detecting the leading edge position of a sheet; an overlapped-feeding-detecting unit  772  for detecting overlapped feeding of sheets; an overlapped-feeding-distance-calculating unit  773  that, based on the detection results of the sheet-detecting unit and the overlapped-feeding-detecting unit, calculates an overlapped-feeding distance in which sheets are overlapped; and a conveyance-control unit  77  that causes the paper-supply roller  72  to stop at a timing when a position separated a set length in the sheet-conveyance direction from a sheet trailing edge reaches the paper-supply roller  72 ; wherein, the conveyance-control unit  77 , in a case where detection of overlapped feeding by the overlapped-feeding-detecting unit  772  occurs a plurality of times, changes the set length to the overlapped-feeding distance. 
     With this configuration, the conveyance load at a location where overlapped-feeding occurs is increased, so it is possible to suppress the recurrence of overlapped feeding, and thus it is possible to improve the down time of an apparatus due to the frequent occurrence of overlapped feeding. 
     According to a typical technique, upon detection of the occurrence of overlapped feeding, sheet conveyance is stopped as overlapped-feeding-occurrence error processing. However, overlapped feeding often recurs until the cause is eliminated, and there is a problem of a situation, “the apparatus cannot be used due to the constant occurrence of overlapped feeding,” occurring until the paper-supply roller, or the like, is replaced, or until a service technician visits. 
     According to the present disclosure, it is possible to suppress the recurrence of overlapped feeding in accordance with detection of overlapped feeding, and it is possible to improve the down time of an apparatus in the case where overlapped feeding occurs frequently. 
     It should be noted that the technique according to the present disclosure is not limited to each of the above embodiments, and it is apparent that each embodiment can be appropriately changed within the scope of the technical idea of the present disclosure. Moreover, the number, the position, the shape, and the like of the above-described constituent members are not limited to those in the above embodiments, but may be a number, a position, a shape, and the like suitable for implementing the technique of the present disclosure. Note that in each figure, the same reference numerals are given to the same constituent elements.