JP2009280312A - Sheet thickness detection device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sheet thickness detection device which is inexpensive, improves space-saving, and does not damage the sheet. <P>SOLUTION: The sheet thickness detection device is equipped with a curved conveying path 19 for guiding a document conveyed by a roller 20, which includes a curved inner guide 19b provided at a curved inner side and a curved outer guide 19a with a larger curvature than that of the inner guide 19b provided at the curved outer side. The thickness of the document to be conveyed is determined based on the time from a predetermined timing until the chip end of the document is detected by a pre-registration sensor 12. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a sheet thickness detection device that detects the thickness of a sheet.

  In recent high-speed copiers, it has been required to increase the capacity of an original conveying apparatus that conveys an original, that is, to allow a larger number of originals to be placed on the original conveying apparatus at a time than before. In order to increase the capacity of the document conveying device, it is conceivable to provide a mechanism for raising the document tray as the number of documents on the document tray decreases in order to stabilize the separation and conveyance of documents on the document tray.

  Japanese Patent Application Laid-Open No. H10-228867 discloses a technique applicable to document tray lifting control. In Patent Document 1, the amount of movement of the tray to be lifted is detected, the number of sheets fed from the tray is counted, and the thickness per sheet is calculated from the amount of movement of the tray and the number of fed sheets. It is shown that it is calculated and reflected in the raising control of the tray.

  However, the material of the original placed on the original tray is not limited to plain paper, but also various types such as thick paper and thin paper, and a bundle of originals in which these sheets are mixed may be placed. In such a case, according to the method of obtaining the thickness per sheet from the amount of movement of the tray and the number of fed sheets, it is not possible to obtain the thickness of each original having various thicknesses. Therefore, it is not suitable for improving the accuracy of raising control of the document tray.

As a method for detecting the thickness of a sheet, a method for detecting a paper thickness by a current of a conveyance motor (Patent Document 2) or a method for detecting a paper thickness by measuring a displacement during conveyance between rollers for conveying a sheet. (Patent Document 3) has been proposed. In addition, a flag (lever) for detecting the passage of a sheet is biased by a spring, and the time required to push down the flag varies depending on the strength of the sheet, and the sheet thickness is detected. Has been proposed (Patent Document 4).
JP 2001-199563 A JP 2003-285484 A JP 2001-328748 A JP 2003-31894 A

  However, those disclosed in Patent Documents 2 and 3 require a dedicated additional sensor, and the cost of the apparatus increases due to an increase in the number of parts. Moreover, since the thing shown by patent document 2 and 3 needs to ensure the space which provides a dedicated sensor, an apparatus will enlarge.

  Further, in the one disclosed in Patent Document 4, since the vibration by the spring is generated when the trailing edge of the sheet passes the lever, in order to increase the detection accuracy of the next sheet leading edge by providing time for the vibration to converge. It is necessary to widen the distance between the sheets.

  Further, when the sheet conveyance speed is high, the impact applied to the leading edge of the sheet in contact with the flag is large, and the leading edge of the sheet in contact with the flag may be deformed in a thin paper or a weak sheet.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet thickness detection device that is low in cost, saves space, and does not damage the sheet.

  In view of the above-described problems, the present invention provides a conveyance unit that conveys a sheet, a curved conveyance path that guides the sheet conveyed by the conveyance unit, a curved inner guide provided inside the curve, A curved conveyance path having an outer guide curved with a curvature larger than the curvature of the inner guide provided on the outside; a detection means provided downstream of the curved conveyance path in the sheet conveyance direction; And a determination unit that determines the thickness of the conveyed sheet based on the time from the timing until the leading edge of the sheet is detected by the detection unit. is there.

  According to the present invention, it is possible to provide a sheet thickness detection device that can save space at low cost.

  FIG. 1 is a cross-sectional view of the document conveying device 100 and the document reading device 200. The document conveying apparatus 100 includes a document tray 30 that can be moved up and down to place a document bundle S composed of at least one sheet, a separation pad 21 that restricts the document bundle S from moving downstream in the conveyance direction, and a pickup. And a roller 1. Before starting the conveyance of the original, the pickup roller 1 is lowered onto the original bundle S and the original tray 30 is raised. As shown in FIG. 2, when the document tray 30 is raised, the pickup roller 1 that is in contact with the upper surface of the document bundle S is pushed up. When the pickup roller 1 is pushed up, the flag 9 blocks between the light emitting part and the light receiving part of the paper surface detection sensor 10. The paper surface detection sensor 10 outputs an ON signal when blocked by the flag 9. When the on signal is output from the paper surface detection sensor 10, the raising of the document tray 30 is stopped. Then, the document is fed from the document bundle S by the pickup roller 1.

  The document fed by the pickup roller 1 is separated into one sheet by the separation roller 2 and the separation pad 21. A post-separation sensor 11 is provided upstream in the sheet conveyance direction of the curved conveyance path 19 and in the vicinity of the upstream of the conveyance roller 3 in the sheet conveyance direction, and outputs an ON signal while a document is being detected. By determining whether or not the post-separation sensor 11 is turned on after a predetermined time from the start of feeding the document by the pickup roller 1, it is determined whether or not the document is fed properly.

  Then, the original is conveyed to the registration roller 4 by the conveyance roller 3, the conveyance path 22, the conveyance roller 20, and the curved conveyance path 19, and the original is abutted against the registration roller 4. When the document is abutted against the registration roller 4 without rotating the registration roller 4, the skew of the document is eliminated. A pre-registration sensor 12 is provided downstream of the curved conveyance path 19 in the sheet conveyance direction and in the vicinity of the registration roller 4 in the sheet conveyance direction, and outputs an ON signal while a document is being detected. By rotating the registration roller 4 in the sheet conveyance direction after a predetermined time has elapsed since the output of the pre-registration sensor 12 is turned on, the original is sent downstream in the conveyance direction with the skew of the original eliminated.

  On the downstream side of the registration roller 4 in the sheet conveyance direction, a paper feed path is provided for feeding the document that has passed through the registration roller 4 toward the reading glass 201. The document sent to the paper feed path is sent onto the flow reading glass 201 by the feeding roller 5 and the reading roller 7. When the original passes through the flow reading glass 201, the reflected light from the surface of the original exposed by the lamp 203 is guided to the CCD sensor 208 by the mirrors 204, 205, 206 and the lens 207, and is read by the CCD sensor 208. The document fed by the reading roller 7 is transported between the roller 16 and the moving glass 18 via the transport roller 6 and discharged to the document discharge tray 31 via the discharge roller 8. When the document is conveyed between the roller 16 and the moving glass 18, the document back side reading unit 17 reads the back side image of the document.

  Further, the document tray 30 is provided with a document presence / absence sensor 14 and can detect whether or not the document bundle S is placed and whether or not all document feeding is completed. Further, the document tray 30 is provided with a side regulating plate (not shown) that is slidable in the sub-scanning direction of the document bundle placed thereon. The document tray 30 is provided with a document width detection sensor (not shown) that detects the document width in conjunction with the side regulating plate. The size of the document fed from the document tray 30 can be determined by the combination of the output of the document width detection sensor and the output of the pre-registration sensor 12.

  FIG. 3 is a control block diagram of the document conveying device 100 and the document reading device 200 described above. The document conveying device 100 includes a central processing unit (hereinafter referred to as CPU) 300, a read only memory (hereinafter referred to as ROM) 301, a random access memory (hereinafter referred to as RAM) 302, and the like. The ROM 301 stores a control program, and the RAM 302 stores input data and work data. Further, a motor 303 that drives various conveying rollers, a lifter motor 306 that moves the document tray 30 up and down, and a pickup motor 311 are connected to the output port of the CPU 300. The post-separation sensor 11, the pre-registration sensor 12, and the paper surface detection sensor 10 are connected to the input port of the CPU 300.

  The CPU 300 controls document conveyance in accordance with a control program stored in a ROM 301 connected via a bus. The CPU 300 performs serial communication with the CPU 321 of the document reading apparatus 200, and exchanges control data with the document reading apparatus 200.

  1 includes a lamp 305 that exposes the back side of the document and a contact image sensor (CIS) 308 that reads reflected light from the back side of the document. The image signal output from the CIS 308 is converted into digital image data, and the image processing unit 309 performs image processing. The image data processed by the image processing unit 309 is held in the image memory 329 of the document reading apparatus 200.

  The document reading apparatus 200 includes a CPU 321, a ROM 322, a RAM 323, and the like. The CPU 321 controls the document reading apparatus 200. The ROM 322 stores a program to be executed by the CPU 321. The RAM 323 is used as a work RAM for the CPU 321. The CPU 321 controls the lamp 203 and the CCD sensor 208.

  The image signal output from the CCD sensor 208 is converted into digital image data, and image processing is performed by the image processing unit 325. The image selector 330 selectively transmits either the image data on the front side of the document received via the image processing unit 325 or the image data on the back side of the document held in the image memory 329 to the controller unit 400.

  The controller unit 400 includes a control circuit 401 that controls the controller unit 400, an operation unit 402 for a user to input an instruction such as document reading, a correction circuit 403 that corrects image data, and an image memory 404 that stores image data. is doing. The controller unit 400 causes the image forming apparatus to form an image on a recording sheet based on the image data.

  In the present embodiment, the CIS is used for the back surface image reading unit of the document conveying device 100 and the CCD is used for the front surface image reading unit of the document reading device 200, but any image reading sensor may be used. .

  Next, measurement of the paper thickness of the document will be described. FIG. 4 is a diagram illustrating a state when a thick paper document is conveyed on the curved conveyance path 19. The curved curved conveyance path 19 that guides the conveyed sheet includes a curved outer guide 19a that guides one side of the original and a curved inner guide 19b that guides the other side of the original. The curvature of the outer guide 19a provided on the outer side of the curved conveyance path 19 is larger than the curvature of the inner guide 19b provided on the inner side of the curve, and the space between the outer guide 19a and the inner guide 19b is different from that of other documents. It is configured wider than the section of the transport path.

  When the leading edge of the thick paper document transported by the transport roller 20 (FIG. 4A) hits the outer guide 19a of the curved transport path 19 (FIG. 4B), it is transported along the outer guide 19a (FIG. 4). (C)) abuts against the registration roller 4 (FIG. 4D). In the case of a thick paper original, the original is strong (high rigidity), and therefore is less likely to bend than a thin paper original. For this reason, the surface of the thick paper document is conveyed along the inner guide 19b (FIGS. 4C and 4D).

  FIG. 5 is a diagram showing a state when a thin paper document is conveyed on the curved conveyance path 19. When the leading edge of the thin paper document conveyed by the conveying roller 20 (FIG. 5A) hits the outer guide 19a of the curved conveying path 19 (FIG. 5B), it is conveyed along the outer guide 19a (FIG. 5). (C)) abuts against the registration roller 4 (FIG. 5D). In the case of a thin paper document, the stiffness of the document is weak (the rigidity is low), so that it is easier to bend than a thick paper document. Therefore, the surface of the thin paper document is conveyed along the outer guide 19a (FIGS. 5C and 5D).

  As described above, the thick paper document is transported along the inner guide 19b, and the thin paper document is transported along the outer guide 19a. Therefore, when the transport roller 20 transports the document at a constant speed, the leading edge of the thick paper document reaches the pre-registration sensor 12 and the registration roller 4 faster than the thin paper document.

  FIG. 6 shows that the sheet leading edge moves from the post-separation sensor 11 to the pre-registration sensor 12 when a sheet having a different weight (basis weight) per unit area is conveyed to the curved conveyance path 19 by the conveyance roller 20. It is a graph which shows the result of having measured time. Here, the conveyance roller 20 conveys the sheet at a constant speed. The same material is used for the seat. As shown in FIG. 6, it can be seen that the heavier the sheet, the shorter the sheet conveyance time in the curved conveyance path 19. In general, it is said that the stiffness (height of rigidity) of the sheet is proportional to the thickness of the sheet. Accordingly, FIG. 6 shows the movement of the sheet in the curved conveyance path 19 as the stiffness of the sheet increases. It can be understood that the time is short.

  Since the sheet weight and thickness are generally proportional, the thickness of the document is indirectly measured by detecting the time required for the leading edge of the document to move from the post-separation sensor 11 to the pre-registration sensor 12. can do. That is, the thicker the original, the shorter the time between sensors, and the thinner the original, the longer the time between sensors. Therefore, data (Table 1) indicating the correspondence between the conveyance time (inter-sensor time) from the post-separation sensor 11 to the pre-registration sensor 12 and the document thickness is measured in advance and stored in the ROM 301.

  The CPU 300 measures the time from when the post-separation sensor 11 (second detection unit) is turned on (detects the tip) until the pre-registration sensor 12 (first detection unit) is turned on (detects the tip). To do. Next, the CPU 300 obtains the thickness of the document corresponding to the measured time by referring to the data indicating the correspondence relationship stored in the ROM 301. In the present embodiment, the paper thickness level of the document is processed in five stages of 1 to 5. In this way, the thickness of the original can be measured.

  Although the thickness of the document is determined by measuring the time required for the leading edge of the document to move from the sensor 11 to the pre-registration sensor 12 after separation, the starting point of the time to be measured does not necessarily depend on the sensor output. The time may be measured from a predetermined timing. The predetermined timing is, for example, a document feeding start timing by the pickup roller 1, and the time from this timing until the pre-registration sensor 12 (first detection unit) detects the leading edge of the document is counted, and based on this time The thickness of the document may be determined.

  In the present embodiment, the post-separation sensor 11 and the pre-registration sensor 12 include a light emitting unit and a light receiving unit that receives light from the light emitting unit, and a document on which light from the light emitting unit to the light receiving unit is conveyed. An optical sensor provided so as to be interrupted by is used. For this reason, since the document leading edge is not a method of detecting the document leading edge by pushing down the flag, it is not necessary to consider the detection timing delay of the document leading edge. Further, since the leading edge of the document is not a method of detecting the leading edge of the document by pushing down the flag, the leading edge of the document is not damaged.

  FIG. 7 shows a control flowchart of the CPU 300 regarding document conveyance. A program for executing this control flowchart is stored in the ROM 301, read by the CPU 300, and manuscript conveyance control is performed according to the program. First, when a document stack S is placed on the document tray 30 by the user and a document reading start instruction is input from the operation unit 402, a document reading job is started (S1000). First, the CPU 300 lowers the pickup roller 1 (S1001), and drives the lifter motor 306 upward (S1002). When the paper surface detection sensor 10 is turned on (the paper surface reaches the feeding position) (S1003), the CPU 300 stops driving the lifter motor 306 (S1004).

  In accordance with a command from the controller unit 400, the CPU 300 starts the document feeding operation by driving the motor 303 (S1005). When the post-separation sensor 11 is turned on (S1006), the CPU 300 refers to the clock included in the CPU 300 and stores the current time in the RAM 302 (S1007). Next, when the pre-registration sensor 12 is turned on (S1008), the CPU 300 calculates the difference between the current time and the time stored in the RAM 302 when the post-separation sensor 11 is turned on. Then, the CPU 300 refers to the data indicating the relationship between the sensor time and the document thickness stored in the ROM 301, and acquires the document thickness level corresponding to the difference time (S1009).

  Next, when the post-separation sensor 11 is turned off (S1010) and the paper surface detection sensor 10 is off (S1011), the CPU 300 cumulatively adds the paper thickness level to the paper thickness counter prepared in the RAM 302. (S1015). Then, the CPU 300 determines whether or not the addition result of the paper thickness counter exceeds a predetermined value (20 in the embodiment) (S1016), and clears the paper thickness counter according to the excess, and the lifter motor 306 is raised (S1017). When the paper surface detection sensor 10 is turned on, the CPU 300 stops the lifting drive of the lifter motor 306 (S1018), and proceeds to step S1012. In this way, the CPU 300 determines the thickness of the document, and controls the rising timing of the document tray 30 based on the determined document thickness.

  If the paper thickness counter does not exceed 20 in step S1016, and if the paper surface detection sensor 10 is on in step S1011, the CPU 300 proceeds to step S1012.

  In step S1012, the CPU 300 determines whether all document feeding has been completed based on the output of the document presence / absence sensor 14 (S1012). If the CPU 300 determines that all document feeding has not been completed, the process advances to step S1005. On the other hand, if it is determined that all document feeding has been completed, the CPU 300 lowers the document tray 30 to a predetermined position (S1013), and ends the document transport job (S1014).

  8 to 10 are timing charts of the lifter motor 306 when the flowchart shown in FIG. 7 is executed. FIG. 8 shows a case where the stacked document bundle consists only of thick paper documents, FIG. 9 shows a case where the stacked document consists only of thin paper documents, and FIG. 10 shows a case where thick paper and thin paper are mixed in the stacked document bundles. It is a timing chart. In each figure, the paper thickness level is added to the paper thickness counter, and the lifter motor 306 is driven up in response to the paper thickness counter exceeding 20. Each figure also shows a state in which the sheet surface height of the document bundle on the document tray 30 is lowered, and the relationship between the sheet surface height and the lift-up start target position.

  With the configuration and control described above, the paper thickness of the fed document is detected, the descending state of the sheet surface height of the document bundle S on the document tray 30 is grasped, and the document tray 30 is raised at an appropriate timing. It becomes possible to make it. According to the configuration of the present embodiment, since it is not necessary to add a sensor for detecting the paper thickness, it is possible to determine the paper thickness of the document at low cost. In addition, since it is not necessary to add a sensor for detecting the paper thickness (also used as a conventional sensor for detecting the timing of document conveyance), it is possible to determine the paper thickness of the document without increasing the size of the apparatus. Is possible. Further, since the leading edge of the document is detected by an optical sensor instead of pushing the spring biased flag by the leading edge of the document, it is possible to determine the paper thickness of the document without damaging the leading edge of the document. .

  In the above-described embodiment, the document thickness determination in the document conveying device has been described.

1 is a cross-sectional view of a document conveying device and a document reading device according to an embodiment of the present invention. FIG. 4 is a diagram illustrating a state where a document tray 30 is raised. FIG. 3 is a control block diagram of document feeder 100 and document reader 200. FIG. 6 is a diagram illustrating a state when a thick paper document is conveyed on a curved conveyance path 19; FIG. 6 is a diagram showing a state when a thin paper document is conveyed on a curved conveyance path 19; 6 is a graph showing a result of measuring a time required to move between sensors when sheets having different weights per unit area are conveyed to the curved conveyance path 19; It is a control flowchart of CPU300 regarding document conveyance. 6 is a lift-up timing chart in a case where a stacked document bundle is composed only of thick paper documents. 10 is a lift-up timing chart in a case where a loaded document is composed of only thin paper documents. 7 is a lift-up timing chart in the case where thick paper and thin paper are mixed in a stacked document bundle.

Explanation of symbols

4 Registration Roller 10 Paper Surface Detection Sensor 11 Post-Separation Sensor 12 Pre-Registration Sensor 19 Curved Conveyance Path 19a Outer Guide 19b Inner Guide 20 Conveying Roller 30 Document Tray 100 Document Conveying Device 200 Document Reading Device

Claims (8)

Conveying means for conveying the sheet;
A curved conveyance path for guiding a sheet conveyed by the conveyance means, wherein the curved inner guide is provided on the inner side of the curve and the outer curve is curved with a curvature larger than the curvature of the inner guide provided on the outer side of the curve. A curved conveying path having a guide;
A detecting means provided downstream of the curved conveying path in the sheet conveying direction, and detecting a leading edge of the sheet;
A determination unit that determines a thickness of a conveyed sheet based on a time from a predetermined timing until the leading end of the sheet is detected by the detection unit;
A sheet thickness detection device comprising: A stacking means for stacking sheets;
A feeding unit that feeds the sheets stacked on the stacking unit to the conveying unit;
The sheet thickness detection apparatus according to claim 1, wherein the predetermined timing is a timing at which feeding is started by the feeding unit. Provided in the sheet conveyance direction upstream of the curved conveyance path, having a second detection means for detecting the leading edge of the sheet,
2. The sheet thickness detection apparatus according to claim 1, wherein the predetermined timing is a timing at which the second detection unit detects the leading edge of the sheet. Stackable means for stacking sheets;
Control means for controlling the timing of raising the loading means;
A feeding unit that feeds the sheets stacked on the stacking unit to the conveying unit;
The sheet thickness detection apparatus according to claim 1, wherein the control unit controls the rising timing of the stacking unit based on the thickness of the sheet determined by the determination unit.   The control means cumulatively adds the thicknesses of sheets determined by the determination means, and raises the stacking means when the addition result exceeds a predetermined value. Item 5. The sheet thickness detection device according to Item 4.   The sheet thickness detection apparatus according to claim 5, wherein the control unit clears the addition result when the addition result exceeds the predetermined value.   The detection means includes a light emitting portion and a light receiving portion that receives light emitted from the light emitting portion, and is provided so that light from the light emitting portion to the light receiving portion is blocked by a document being conveyed. The sheet thickness detection apparatus according to claim 1, wherein the sheet thickness detection apparatus is a sensor. Storage means for storing data indicating the correspondence between the time from the predetermined timing until the leading edge of the sheet is detected by the detection means and the thickness of the sheet;
The determination means determines the thickness of the conveyed sheet based on the time from the predetermined timing until the leading edge of the sheet is detected by the detection means and the data stored in the storage means. The sheet thickness detection apparatus according to claim 1, wherein

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