JP2008297021A - Paper feed device and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper feed device capable of detecting the remaining amount of paper sheets with excellent accuracy, avoiding degradation of the productivity, and correctly performing the near-empty processing. <P>SOLUTION: The paper feed device comprises a paper sheet loading stand for loading paper sheets to be fed, and a plurality of distance measurement sensors. One of the distance measurement sensors is arranged to measure the distance to an upper surface of the paper sheet loading stand in a non-loaded state, and the other is arranged to measure the distance to an upper surface of the paper sheet loaded on the paper sheet loading stand. A control means is provided, which calculates the amount of paper sheets loaded on the paper sheet loading stand by the difference between the distance measured by one distance measurement sensor and the distance measured by the other. By comparing the calculated amount of paper sheets with the predetermined remaining amount threshold, the near-empty processing is performed when the remaining paper sheet amount is equal to or less than the remaining amount threshold. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a paper feeding device that feeds paper and an image forming apparatus that includes the paper feeding device and forms an image on paper fed from the paper feeding device based on image data.

Image forming apparatuses such as copiers, facsimiles, printers, and multifunction machines of these perform image formation on paper based on image data, and the paper is fed into a paper feeding device or image formation integrated with the image forming apparatus. Paper is fed from a paper feed tray of a paper feed device externally attached to the apparatus. In the paper feed tray, paper is stacked on the paper stacking base (also called the bottom plate), and the height of the paper stacking base is adjusted as the paper is removed, so that paper can be fed one after another from the tray and fed. I have to.
The paper feeding device is provided with a paper presence / absence detection sensor for detecting the presence / absence of paper in each tray. When the absence of paper is detected, the image forming apparatus stops the operation in response to the detection result. A message instructing paper supply is displayed.

However, in this method, the operation is suddenly stopped in the middle of image formation, which causes a decrease in productivity. In addition, since it takes time to form an image in a color machine or the like, the image is already written on the photosensitive member or the transfer belt when the absence of paper is detected, and the toner is consumed wastefully. For this reason, it has been desired to develop an image forming apparatus capable of preliminarily supplying paper by knowing the remaining amount of paper in advance or avoiding wasteful toner consumption. On the other hand, the remaining thickness of the paper is detected, the thickness per sheet is calculated from the number of fed sheets and the change in the remaining thickness, and the sheet thickness per sheet is calculated. An image forming apparatus that calculates the remaining number of sheets based on the remaining thickness is proposed (see Patent Document 1). In this image forming apparatus, the remaining thickness of the paper is detected by detecting the amount of displacement (lifting amount) of the loading platform relative to the height of the loading platform when the paper is fully loaded. The remaining sheet thickness is obtained by subtracting the amount of displacement from the sheet thickness at the time. By detecting the remaining amount of paper in advance by this image forming apparatus, when the remaining amount of paper becomes low, it becomes possible to stop the operation or perform near empty processing for instructing the replenishment of paper.
Japanese Patent Laid-Open No. 9-2089086

  However, in the configuration of the image forming apparatus proposed above, it is necessary that the position of the sheet stacking table is accurately stopped regardless of the state of the sheet, and the upper surface of the sheet is accurately positioned at the set position. However, in general, the position of the sheet stacking table is controlled so as to stop the drive motor that adjusts the sheet stacking table by detecting the upper surface of the sheet with a sensor. The stoppage of the drive motor differs depending on the remaining amount (mass) of the paper (the time until stoppage varies depending on the inertia state of the load). Due to this difference, the stop position of the sheet stacking table varies, and the height of the upper surface of the sheet changes within a range (1-2 mm) that does not affect the sheet passing. Although the variation does not affect the paper feeding, there is a large difference with respect to the paper thickness (about 0.04 to 0.6 mm), and therefore there is a problem that the remaining amount of paper cannot be detected with high accuracy. If you calculate the remaining number of sheets by increasing the safety level in anticipation of errors, the near-empty process will be accelerated and the machine will stop even though there are several tens of sheets remaining. There is a problem that productivity is reduced due to movement to another tray (ATS) or the like even though there is a remainder.

  The present invention has been made against the background of the above circumstances, accurately detects the remaining amount of paper that can be fed, accurately executes near-empty processing without impairing productivity, and is wasteful. An object of the present invention is to provide a sheet feeding device and an image forming apparatus that can reliably avoid toner consumption and the like.

  That is, the first invention of the paper feeding device of the present invention includes a paper stacking table on which paper to be fed is stacked and a plurality of distance measuring sensors, and one of the distance measuring sensors is the paper stacking device. A distance between the upper surface of the sheet and the sheet non-stacking surface, and the other distance measuring sensor is arranged to measure a distance between the upper surface of the sheets stacked on the sheet loading table and the one distance measuring sensor. And a control means for calculating the amount of paper stacked on the paper stacking board based on the difference between the distance measured in step 1 and the distance measured by the other distance measuring sensor.

  According to the paper feeding device of the first aspect of the present invention, the amount of paper loaded on the paper stacking table is obtained as a difference between the distances measured by the two distance measuring sensors. You can know the amount of paper accurately. Various controls can be performed based on accurate information on the amount of paper.

  A sheet feeding device according to a second aspect of the present invention is the sheet feeding device according to the first aspect of the present invention, wherein the control means is measured by the one distance measuring sensor in a state where the sheet is not stacked on the sheet stacking table. The difference obtained when the paper is loaded on the paper stacking table is corrected using the unloaded difference obtained from the measured distance and the distance measured by the other distance measuring sensor as a correction amount. The amount of paper is calculated.

  According to the second aspect of the present invention, since the difference in the measurement distance between the distance measuring sensors can be obtained in a state where no paper is stacked on the paper stacking base, the vertical position of the two distance measuring sensors can be obtained. Even if they are not exactly the same, by correcting this as a correction amount, the difference in the distance can be obtained as accurate when the paper is stacked on the paper stacking base. The remaining amount of paper can be measured accurately. Since it is difficult for the distance measuring sensor to adjust the measurement result when the paper is not stacked to 0 due to the accuracy of the mounting position, the inclination of the paper stacking table, etc., the above-described configuration eases the requirement for the mounting accuracy of the distance measuring sensor.

  The paper feeding device according to a third aspect of the present invention is characterized in that, in the paper feeding device according to the second aspect of the present invention, the control means uses the correction amount acquired in advance.

  A paper feeding device according to a fourth aspect of the present invention is the paper feeding device according to any one of the first to third aspects, wherein the calculated paper amount is a paper height.

  According to a fifth aspect of the present invention, in the paper feeding device according to any one of the first to third aspects, the control unit calculates the number of sheets from the difference based on the sheet information. Features.

  According to a sixth aspect of the present invention, there is provided the paper feeding device according to the fourth aspect of the present invention, wherein the control means calculates a paper thickness from a change in the height of the paper by feeding a predetermined number of sheets, The number of sheets stacked on the sheet stacking table is calculated from the sheet height calculated from the difference.

  A paper feeding device according to a seventh aspect of the present invention is the paper feeding device according to any one of the first to sixth aspects, wherein the paper feeding device is in the vicinity of a distance measuring sensor that measures the distance from the upper surface of the paper loaded on the paper loading table. Further, a sheet pressing member for suppressing the floating of the sheet is provided.

  According to an eighth aspect of the present invention, there is provided the paper feeding device according to any one of the first to seventh aspects of the present invention, wherein the paper stacking base is adjusted and controlled in a vertical position according to a stacking amount of the loaded paper. It is characterized by being.

  According to a ninth aspect of the present invention, there is provided an image forming apparatus according to any one of the first to eighth aspects of the present invention, and an image for forming an image on a sheet fed from the sheet feeding apparatus based on image data. And a forming portion.

  An image forming apparatus according to a tenth aspect of the present invention is characterized in that, in the image forming apparatus according to the tenth aspect of the present invention, information on sheets stacked on the sheet stacking table is registered.

  An image forming apparatus according to an eleventh aspect of the present invention is the image forming apparatus according to the ninth or tenth aspect of the present invention, wherein the sheet amount obtained by the control means is compared with a predetermined remaining amount threshold value. When the amount of paper is less than or equal to the remaining amount threshold value, near empty processing is performed.

  According to the image forming apparatus of the eleventh aspect of the present invention, the remaining amount of paper in the paper feeding device can be accurately obtained, and the near empty process can be performed based on the remaining amount of paper. As a result, near empty processing can be performed while maintaining productivity, and wasteful processing of toner can be avoided.

  An image forming apparatus according to a twelfth aspect of the invention is the image forming apparatus according to the eleventh aspect of the invention, wherein the near empty process is any one of a change of a tray in the paper feeding device, a stop of the image forming device, and a paper filling instruction. .

  An image forming apparatus according to a thirteenth aspect of the present invention is the image forming apparatus according to the eleventh or twelfth aspect of the present invention, further comprising an input unit that allows a user to set or change the remaining amount threshold value.

  An image forming apparatus according to a fourteenth aspect of the present invention is the image forming apparatus according to any one of the eleventh to thirteenth aspects, wherein the remaining amount threshold is a sheet height or the number of sheets.

  An image forming apparatus according to a fifteenth aspect of the present invention is the image forming apparatus according to any one of the eleventh to fourteenth aspects, wherein a sheet height and a number of sheets are set as the remaining amount threshold, When the number of stacked sheets is not calculated, the sheet height is used as the remaining amount threshold, and the number of sheets is used as the remaining amount threshold when the number of sheets is calculated.

  According to the fifteenth aspect of the image forming apparatus of the present invention, when the number of sheets cannot be obtained as the remaining amount, it is possible to make a determination for the near empty processing based on the sheet height, and it is difficult to calculate the number of sheets. It is possible to perform near-empty processing based on the remaining amount of paper even before the start of time or job printing.

  As described above, according to the sheet feeding device of the present invention, the sheet stacking unit on which sheets to be fed are stacked and a plurality of distance measuring sensors are provided, and one of the distance measuring sensors is the sheet stacking sensor. A distance between the upper surface of the sheet and the sheet non-stacking surface, and the other distance measuring sensor is arranged to measure a distance between the upper surface of the sheets stacked on the sheet loading table and the one distance measuring sensor. Control means for calculating the amount of paper stacked on the paper stacking board based on the difference between the distance measured by the other distance measuring sensor and the distance measured by the other one distance measuring sensor. By using this, it is possible to accurately detect the amount of paper on the paper stacking table.

  According to the image forming apparatus of the present invention, the image forming apparatus includes the above-described sheet feeding device of the present invention and an image forming unit that forms an image on a sheet fed from the sheet feeding device based on the image data. Therefore, it is possible to perform accurate device operation based on accurate information on the remaining amount of paper in the paper feeding device, and it is possible to perform near-empty processing without reducing productivity, thereby increasing productivity. Since it is possible to detect the absence of paper immediately before maintaining, it is possible to suppress wasteful consumption of toner.

Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a diagram showing an outline of a mechanical structure in an image forming apparatus 1 according to an embodiment of the present invention. Although not shown in FIG. 1, the image forming apparatus 1 has an image reading unit 3 including a scanner, an automatic document feeder (ADF), and the like on the upper side, and in the vicinity thereof, image forming is performed. There is provided an operation unit 4 which can input various settings of the apparatus and display information. The operation unit 4 can be configured by, for example, a touch panel LCD.

  In addition, on the lower side of the image forming apparatus 1, three-stage sheet feeding trays 20, 30, and 40 for storing and feeding sheets are arranged, and a manual sheet feeding tray 50 is disposed on the side of the image forming apparatus 1. Is arranged. These paper feed trays 20 to 50 have paper stacking bases 21, 31, 41, 51 on which the papers P 1 to P 4 are respectively stacked. These paper stacking bases 21 to 51 are equipped with a paper tray lifting / stopping motor 22. , 32, 42, 52 can adjust the vertical position. Each of the paper feed trays 20 to 50 is provided with paper feed rollers 23, 33, 43, and 53 for feeding the stacked sheets. The paper feed tray, the paper stacking table, the paper tray lifting / stopping motor, and the paper feed roller constitute a part of the paper feed unit 2 serving as a paper feed device. The paper feed unit 2 is connected to a conveyance unit 8 including a conveyance roller and a conveyance route. The conveyance route of the conveyance unit 8 extends to the image forming unit 7 that forms an image on the paper fed from the paper supply unit 2. It is arranged to convey. The paper feeding unit and the conveying means 8 may constitute a paper feeding device.

  The image forming unit 7 includes photoreceptors 10, 11, 12, 13 prepared for each color (cyan, magenta, yellow, black, etc.), a charger (not shown), an LD unit, a developer, an intermediate transfer transfer belt 14, A secondary transfer belt 15, a cleaning device 16, a fixing device 17 and the like are provided, and the paper is discharged to the downstream side thereof.

  Details of the mechanical configuration of the paper feed tray will be described with reference to FIG. FIG. 2 shows the configuration of the paper feed tray 20 out of the paper feed trays, and the other paper feed trays have the same configuration, and thus detailed description thereof will be omitted.

  As described above, the paper stacking base (bottom plate) 21 is disposed in the paper feed tray 20, and the paper stacking base 21 can be moved up and down by a paper tray lifting / stopping motor 22 disposed on the lower side. The position can be adjusted. A distance measuring sensor 24a for measuring a distance (bottom plate height detection) from a non-stacking upper surface on which the sheets P1 are not stacked is disposed above the sheet stacking table 21, and a height position similar to that of the distance measuring sensor 24a. A distance measuring sensor 24b capable of measuring the distance (sheet portion height detection) from the upper surface of the sheet P1 loaded on the sheet loading table 21 is disposed. A paper feed roller 23 and a paper upper limit detection sensor 25 are arranged in the vicinity of the distance measuring sensor 24b. The paper feed roller 23 feeds out paper while being in contact with and pressed against the upper surface of the paper stacking table 21, and has a function as a paper pressing member of the present invention.

Next, FIG. 3 is a diagram showing an operation block of the image forming apparatus. This will be described below.
That is, the image forming apparatus 1 includes a control unit 5 that controls the entire image forming apparatus, the image reading unit 3, the operation unit 4, the paper feeding unit 2, the conveying unit 6, and the image forming unit 7 as main components.

  The control means 5 is a ROM that stores a CPU 5a and a program for operating the same, a RAM that temporarily stores data, an image memory that stores image data, setting data of the image forming apparatus 1, process control parameters, paper information, near A storage unit 5b including a nonvolatile memory for storing empty value data or the like is provided. The control unit 5 controls the entire image forming apparatus 1 and can call the setting data registered in the nonvolatile memory to operate the image forming apparatus 1.

  Further, the operation unit 4 is connected to the control means 5 in a controllable manner as described above. The operation unit 4 is controlled by the control unit 5 so that the user can perform a predetermined operation on the image forming apparatus 1. In the operation unit 4, the display and the operation may be performed independently, or the operation unit 4 may be an operation that can be performed on the display screen like an LCD touch panel. The operation unit 4 can input various settings for the image forming apparatus and functions as an input unit of the present invention.

  Further, the control means 5 is connected to the image reading means 3 for acquiring image data from the document as described above. The image reading unit 3 includes a scanner unit, an automatic document feeder, and the like, generates image data by reading a document, and sends the image data to the control unit 5. The image data may be acquired outside the image forming apparatus 1 and provided to the image forming apparatus 1 via a network, a recording medium, or the like.

  An image forming unit 7 is further connected to the control unit 5 in a controllable manner. The image forming unit 7 charges the photoconductors 10 to 13 with a charger (not shown), generates a latent image on the photoconductors 10 to 13 based on image data with an LD (not shown), and the like. The image is developed by a developing device and transferred onto a sheet through an intermediate transfer belt 14 and a secondary transfer belt 15 to form an image. After the transfer, toner particles remaining on the intermediate transfer belt 14 are removed by the cleaning member 16 to prepare for the next image formation. The image transferred to the transfer paper is heated and fixed by the fixing unit 17 and an image forming output (printing) is performed on the paper discharge unit 0.

  Further, as described above, the paper feeding unit 2 is connected to the control unit 5 in a controllable manner. The paper feed unit 2 is controlled by the control means 5 and selects the paper feed trays 20 to 50 to be used, the paper feed timing, the operation of the paper feed rollers 23 to 53, the operation of the paper tray lifting / stopping motors 22 to 52, etc. Is managed by the control means 5. The detection results of the distance measuring sensors 24a and 24b and the sheet upper limit detecting sensor 25 are input to the control means 5, and the amount of sheets stacked on the sheet stacking board is determined by the difference from the distance measured by the distance measuring sensor. It functions as a means for calculating and a means for performing near empty processing.

The basic operation of the image forming apparatus of the present invention will be described below.
The image data acquired by the image reading unit 3 or the like is sent to the control unit 5 and subjected to predetermined data processing, and then stored in the storage unit 5a. At the time of image formation, the control unit 5 sends image data to the image forming unit 7 and irradiates the photoconductors 10 to 13 with laser light corresponding to the image data by the LD unit to form an electrostatic latent image. Prior to this, the photoconductors 10 to 13 are charged by a charger. The electrostatic latent image is developed with a developing device to form a toner image on the photoconductors 10 to 13. The toner image is transferred onto the sheet via the intermediate transfer belt 14 and the secondary transfer belt 15 and then fixed by the fixing device 17.

  On the other hand, the control means 5 issues a paper feed command to a designated paper feed tray or a paper feed tray that is automatically selected based on information such as the paper size related to the job. The paper fed from the paper feed tray is transported through the transport unit 8 controlled by the control unit 5 and supplied to the image forming unit 7 described above. Further, in the paper feed unit 2, for example, the paper feed tray 20 is lifted by the paper tray lift / stop motor 22 while the paper tray upper limit detection sensor 25 detects the upper limit of the paper P <b> 1. Control is performed so that the upper surface of the stacked paper P1 is at the upper limit position. The paper P1 in the upper limit position is fed one by one by the paper feed roller 23. The distance between the non-stacking upper surface and the paper portion upper surface of the paper stacking table 21 is measured by distance measuring sensors 24 a and 24 b, and the result is sent to the control means 5. The control means 5 calculates the difference. In addition, the measurement results of the distance measuring sensors 24 a and 24 b are sent to the control unit 5 in a state where no sheets are stacked on the sheet stacking table.

  The control means 5 obtains the difference between the measurement results when the sheets are not stacked, and stores this difference in the storage unit 5b as a correction amount. Further, the difference between the measurement results when the sheets are stacked is obtained, and the difference is corrected by the correction amount to calculate the remaining sheet height on the sheet stacking table 21. In addition, when the sheet thickness information is included, the remaining sheet number can be calculated from the remaining sheet height. Further, the control means 5 can store a near empty threshold in the storage unit 5b. The threshold value can be defined by the number of sheets and the sheet height. The control means 5 compares the remaining amount of paper with the threshold value, and can execute a near empty process when the remaining amount of paper becomes equal to or less than the threshold value. The threshold value may be stored in advance in the storage unit 5 b as an initial value, or may be input and changed by the user via the operation unit 4.

Next, control for detecting the remaining amount of paper in the image forming apparatus 1 will be described in more detail based on a flowchart.
FIG. 4 illustrates a procedure for obtaining the correction amount described above.
First, the height storage mode when there is no tray paper is started (step A1). The mode may be started before the image forming apparatus 1 is shipped, or after the shipment, the user may instruct the start via the operation unit 4 as a setting at the time of installation or appropriately. . In starting the mode, the tray to be adjusted first is selected (step A2). Therefore, when a plurality of paper feed trays are provided, it is desirable to execute a procedure for obtaining a correction amount for each tray.

  After the adjustment tray is selected, it is determined whether or not there is paper on the adjustment tray (step A3). Presence / absence of paper can be determined by a known paper presence / absence detection sensor or the like. If there is a sheet on the adjustment tray, the correction amount cannot be obtained, so that a warning is displayed to request that the operation unit 4 has a sheet and to remove the sheet (step A4). After the warning is displayed, the timer is operated (step A5), and until the timer count ends (step A6), it is detected whether the tray has been inserted or removed (step A7). This determination can be made by a tray presence / absence detection sensor or the like. If the tray is inserted or removed, the process returns to step A3, and the presence or absence of paper is continuously detected. If the tray is not inserted / removed until the timer count is finished (step A6, YES), the sheet remains, so the height storage mode for determining the correction amount is finished (step A8).

On the other hand, when no paper is detected in step A3 (step A3, NO), it is detected whether or not the paper stacking base of the target tray is at the upper limit position (step A9). The detection can be performed by a loading table upper limit detection sensor (not shown). If the paper stacking base is not at the upper limit position (step A9, NO), the paper stacking base is raised by the paper tray lift / stop motor until the paper stacking base reaches the upper limit position (step A10).
If the paper stacking base is at the upper limit position (step A9, YES), if the paper tray raising / stopping motor is operating, the motor is stopped (step A11). Thereafter, the distance from the sheet stacking base (bottom plate) is detected by the distance measuring sensor for detecting the height of the bottom plate and the distance measuring sensor for detecting the height of the paper portion. This detection result is sent to the control means 5, and the control means 5 calculates the difference (paper portion height-bottom plate height) (step A12). This data is stored in the storage unit 5b as a correction amount (step A13), and the height storage mode is terminated (step A8).

Next, a procedure for calculating the remaining amount of paper when the paper is stacked on the paper stacking base will be described with reference to FIG.
First, the distance from the sheet stacking base (bottom plate) is detected by a distance measuring sensor for detecting the height of the bottom plate and sent to the control means 5 (step B1). Next, the distance from the upper surface of the paper is detected by a distance measuring sensor for detecting the height of the paper portion, and sent to the control means 5 (step B2). The control means 5 calculates the difference Ha (paper portion height-bottom plate height) from these measurement results (step B3). Further, the control means 5 reads the correction amount Hb of the storage unit 5b (step B4), and subtracts the correction amount Hb from the difference Ha calculated above to obtain corrected data H = Ha−Hb (step B5). Here, for example, if the correction amount is +, the corrected data H is smaller than the actual difference, and if the correction amount is −, the corrected data H is larger than the actual difference. The calculated value H is set as the remaining sheet height (step B6), and the process is terminated.

When the paper thickness is obtained by paper information or calculation at the time of paper feeding, the remaining amount of paper can be calculated by the number of sheets. The procedure will be described with reference to FIG.
First, the sheet thickness d is acquired from the sheet information stored in the storage unit 5b (step C1). Next, the distance from the sheet stacking base (bottom plate) is detected by the distance measuring sensor for detecting the bottom plate height in the same manner as the above procedure, and is sent to the control means 5 (step C2). Next, the distance from the upper surface of the paper is detected by a distance measuring sensor for detecting the height of the paper portion and sent to the control means 5 (step C3). The difference Ha is calculated from these measurement results (step C4). Further, the control means 5 reads the correction amount Hb in the storage unit 5b (step C5), and subtracts the correction amount Hb from the difference Ha calculated above to obtain H (step C6). The calculated value H is divided by the sheet thickness d to calculate S = H / d (step C7). The S is set as the remaining number of sheets (step C8), and the process is terminated.

  Further, in the image forming apparatus 1, when the remaining amount of paper is reduced, near-empty processing is possible in order to prevent a decrease in productivity and avoid wasteful consumption of toner. An example of this near empty process will be described based on the procedure of FIG. When the remaining amount of paper reaches the near empty threshold, the near empty process is started. First, it is determined whether or not there is an immediate tray change instruction (step D1). The instruction is set in advance by initial setting or the like. The setting may be set at the time of shipment of the image forming apparatus, or may be input and changed by the user via the operation unit 4. If there is an immediate tray change instruction, printing is stopped in preparation for the tray change (step D5).

  If there is no immediate tray change instruction, the printing operation is performed with the sheet interval changed and the printing speed reduced (step D2). This is to avoid wasted toner being consumed due to development of the photoconductor without being in time when a state of no paper is detected. Printing is continued at this reduced speed, and it is detected whether or not paper remains in the tray (step D3). If there is no paper, printing is stopped (step D5). If the presence of paper is detected, printing is continued until printing is completed while detecting the presence of paper (step D4), and printing is stopped when printing is completed (step D5). The content of the near empty processing is an example, and the present invention is not limited to this. Also, the user may be able to input and change the near empty processing content, or may be arbitrarily selected from a plurality of processing content.

  Next, a procedure up to the near empty process using the remaining sheet detection according to the present invention will be described with reference to the flowchart of FIG. In the image forming apparatus 1, threshold values relating to the number of sheets and the sheet height for near-empty processing are set, and the threshold value for the number of sheets is normally used.

  At the time of the printing operation, the user performs paper setting and a printing instruction (step E1). Receiving this, the control means 5 determines whether or not the paper thickness has been set (step E2). For example, the sheet thickness may be stored in advance in the storage unit 5b as the sheet information of the sheet set in the sheet setting. Further, the sheet thickness may be set and input in the sheet setting. Further, it may be acquired by a paper thickness calculation method described later. When the paper thickness is set (step E2, YES), the near empty position (paper height) is set from the near empty threshold of the number of sheets according to the set thickness (step E3). After the setting, the remaining sheet height is calculated by the procedure shown in FIG. 5 (step E4). The remaining sheet height is compared with the near empty position to determine whether or not the near empty position has been reached (step E34).

  On the other hand, if it is determined in step E2 that the paper thickness has not been set (step E2, NO), it is set to the near empty position given as the initial value (step E5). After the setting, the remaining sheet height is calculated by the procedure shown in FIG. 5 (step E6). The remaining sheet height is compared with the near empty position to determine whether or not the near empty position has been reached (step E7). If it is in the near empty position (step E7, YES), the near empty process shown in FIG. 7 is executed (step E8). After the processing, it is determined whether or not ATS (automatic tray selection) is set (step E9). At this time, a flag can be set and used based on the determination result of whether or not there is an immediate tray change instruction in the near empty process. If there is an ATS setting (step E9, YES), it is determined whether or not the same sheet as the paper setting is in another tray (step E10). Is performed (step E11), and the process returns to step E2. If the same sheet is not in another tray (step E10, NO), the image forming apparatus is mechanically stopped (step E12), and no paper is displayed on the operation unit 4 to prompt the user to replenish the sheet (step E13). ). This series of procedures (steps E2, E5 to E13) is suitable when the number of sheets is small and sheet information is not obtained at the beginning of the operation of the apparatus.

On the other hand, if the remaining amount of paper has not reached the near empty position in step E7 (step E7, NO), the printing operation is started to calculate the paper thickness (step E15), and the distance measuring sensor can detect it. It is determined whether the position is correct (step E16). This is because, for example, in a state where the paper stacking base is at a low position where the remaining amount of paper is almost full, the position detection may not be performed because it is outside the detectable range of the distance measuring sensor. If it is not the detectable position, the determination is repeated until the end of printing (step E17), and if the printing is terminated without being detected, the printing end process is performed (step E18). When the sheet stacking table is within the detectable range of the distance measuring sensor (step E16, YES), the counting of the number of printed sheets is started and a count target value is set (step E19). Next, the position detection by the bottom plate distance measuring sensor is immediately performed, the measurement result is sent to the control means 5 (step E20), and the detection result is stored in the storage unit 5b (step E21). After the measurement, it is counted up for each print and it is determined whether or not the count end is reached (step E22). If the count end is not reached, the remaining sheet height is calculated according to the procedure shown in FIG. E23), it is determined whether or not the near empty position has been reached (step E24). When it is determined that the near empty position has been reached (step E24, YES), the near empty process shown in FIG. 7 is performed without calculating the sheet thickness (step E38), and the process proceeds to step E9.
If the near empty position has not been reached (step E24, NO), the count end is determined (step E22) until the printing is finished (step E25), and if the printing is finished before the count end is reached (step E22). (E25, YES), printing is terminated (step E26).

  On the other hand, when the count end is reached before printing is completed by printing (step E22, YES), the position detection by the distance sensor for the bottom plate is immediately performed, and the measurement result is sent to the control means 5 (step E30). The control means 5 reads out the stored bottom plate measurement position at the start of counting, calculates the difference from the bottom plate measurement position after the count end, and divides this by the counted number of sheets, thereby obtaining the number of sheets per sheet. Is calculated (step E31). Using this sheet thickness, a near empty position is calculated from the number of sheets of the near empty threshold, and is replaced with the default near empty position (step E32). Next, the remaining sheet height is calculated by the procedure shown in FIG. 5 (step E33), and it is determined whether or not the near empty position has been reached (step E34). If it is determined that the near empty position has been reached (step E34, YES), the near empty process shown in FIG. 7 is performed without calculating the paper thickness (step E38), and the process proceeds to step E9. On the other hand, when it is determined that the near empty position has not been reached, the printing operation is continued (step E35), until the printing is completed (step E36), the near empty determination is repeated, and when printing is completed (step E36, YES), printing is performed. Is terminated (step E37).

  Conventionally, when the near-empty accuracy is low, the machine stops, the operation is slow, even though there are several tens of sheets remaining, and there is paper remaining (ATS) etc. However, in the present invention, as described in the above embodiment, near-empty determination can be performed with high accuracy, and the decrease in productivity is minimized. Thus, useless use of toner can be avoided.

  As mentioned above, although this invention was demonstrated based on the said embodiment, this invention is not limited to description of the said embodiment, Of course, it can change within the scope of the present invention.

1 is a schematic diagram illustrating a mechanical configuration of an image forming apparatus according to an embodiment of the present invention. Similarly, it is an enlarged plan view and a side view showing a part of the paper feed unit. Similarly, it is an operation block diagram. Similarly, it is a flowchart showing a procedure for obtaining a correction amount in paper height detection. Similarly, it is a flowchart showing a procedure for calculating the remaining sheet height. Similarly, it is a flowchart showing a procedure for calculating the remaining number of sheets. Similarly, it is a flowchart which shows the procedure of a near empty process. Similarly, it is a flowchart showing a procedure of near empty determination using a procedure for calculating the remaining sheet height.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 2 Paper feed part 4 Operation part 5 Control means 5a CPU
5b Storage unit 7 Image forming unit 8 Conveying means 20, 30, 40, 50 Paper feed trays 21, 31, 41, 51 Paper stacking bases 22, 32, 42, 52 Paper tray raising / stopping motor 23 Paper feed roller 24a Distance measurement Sensor 24b Distance sensor 25 Paper upper limit detection sensor

Claims (15)

  A sheet stacking table on which sheets to be fed are stacked; and a plurality of distance measuring sensors, wherein one of the distance measuring sensors measures a distance from the sheet non-stacking upper surface of the sheet stacking table, The other one of the sensors is arranged to measure the distance from the upper surface of the paper stacked on the paper stacking table, and the distance measured by the one distance measuring sensor and the other distance measuring sensor. A sheet feeding apparatus comprising: a control unit that calculates an amount of sheets stacked on the sheet stacking board based on a difference from the measured distance.   The control means is an unloaded state obtained from a distance measured by the one distance measuring sensor and a distance measured by the other distance measuring sensor in a state where the sheet is not loaded on the sheet loading table. The paper feeding device according to claim 1, wherein the paper amount is calculated by correcting the difference obtained in a state where the paper is stacked on the paper stacking table, using the difference as a correction amount.   The sheet feeding device according to claim 2, wherein the control unit uses the correction amount acquired in advance.   The sheet feeding device according to claim 1, wherein the calculated sheet amount is a sheet height.   The sheet feeding device according to claim 1, wherein the control unit calculates the number of sheets from the difference based on sheet information.   The control means calculates a paper thickness from the change in the paper height due to a predetermined number of paper feeds, and determines the paper loaded on the paper stacking table from the paper thickness and the paper height calculated from the difference. The sheet feeding device according to claim 4, wherein the number of sheets is calculated.   7. The sheet pressing member for suppressing the floating of the sheet is provided in the vicinity of a distance measuring sensor for measuring the distance from the upper surface of the sheet loaded on the sheet loading table. The sheet feeder according to any one of the above.   The sheet feeding device according to claim 1, wherein the sheet loading table is configured such that the vertical position is adjusted and controlled in accordance with the loading amount of the loaded sheets.   An image comprising: the sheet feeding device according to claim 1; and an image forming unit that forms an image on a sheet fed from the sheet feeding device based on image data. Forming equipment.   The image forming apparatus according to claim 9, wherein information on sheets stacked on the sheet stacking table is registered.   The paper amount obtained by the control means is compared with a predetermined remaining amount threshold value, and when the sheet amount is equal to or smaller than the remaining amount threshold value, a near empty process is performed. Or 10 is an image forming apparatus.   12. The image forming apparatus according to claim 11, wherein the near empty process is any one of a tray change in the sheet feeding device, an image forming apparatus stop, and a sheet filling instruction.   The image forming apparatus according to claim 11, further comprising an input unit that allows a user to set or change the remaining amount threshold value.   The image forming apparatus according to claim 11, wherein the remaining amount threshold is a sheet height or the number of sheets.   When the sheet height and the number of sheets are set as the remaining amount threshold, and the number of sheets loaded on the sheet stacking table is not calculated, the sheet height is used as the remaining amount threshold, and the number of sheets is set. The image forming apparatus according to claim 11, wherein the number of sheets is used as the remaining amount threshold in a state where calculation is performed.

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