Sheet stacking device and image forming apparatus

Abstract

To provide a sheet loading device and an image forming device capable of accurately detecting a sheet size.SOLUTION: A sheet feeding cassette 15 serving as a sheet loading device includes: a bottom plate 104 serving as a sheet loading part for placing a sheet; and an imaging device 110 serving as imaging means for imaging the entire sheet loaded on the bottom plate 104. A sheet loading device detects a sheet size of the sheet loaded on the bottom plate 104, a sheet loading amount, the presence or absence of an image on a front surface, a gap between a side fence 102 or an end fence 103 and the sheet, and whether or not the sheet on the bottom plate is the last sheet, based on image data captured by the imaging device 110.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a sheet stacking device and an image forming apparatus. [Background technology]

[0002] 2. Description of the Related Art Conventionally, a sheet stacking device including a sheet stacking section for stacking sheets is known.

[0003] Patent document 1 describes a sheet stacking device that includes a detection mechanism that detects the position of a side fence, which acts as a regulating member that regulates the position of sheets loaded on the sheet stacking section, and detects the size of the sheets loaded on the sheet stacking section based on the position of the side fence detected by the detection mechanism. Summary of the Invention [Problem to be solved by the invention]

[0004] However, there are cases where the sheet size cannot be detected accurately. [Means for solving the problem]

[0005] In order to solve the above-mentioned problems, the present invention provides a sheet stacking device that includes a sheet stacking section for stacking sheets, an end fence that abuts against the rear ends of the sheets stacked on the sheet stacking section to regulate the position of the sheets in the feeding direction, and an imaging device that images all of the sheets stacked on the sheet stacking section and the end fence, and that measures a gap between the end fence and the rear ends of the sheets based on image data captured by the imaging device when the sheets are set, and a gap between the end fence and the rear ends of the sheets based on image data captured by the imaging device after the feeding device starts feeding the sheets. The difference value of Based on this, it is possible to detect whether the sheet stacked on the sheet stacking section is the last sheet or not. [Effects of the Invention]

[0006] According to the present invention, the sheet size can be detected with high accuracy. [Brief explanation of the drawings]

[0007] [Figure 1] 1 is a cross-sectional view showing the outline of a full-color printer as an example of an image forming apparatus equipped with a double-sided device according to an embodiment of the present invention; [Figure 2] FIG. 2 is an explanatory diagram of a conveying path of a full-color printer. [Figure 3] FIG. 2 is a schematic perspective view showing a sheet feed cassette serving as a sheet stacking device. [Figure 4] FIG. 2 is a schematic configuration diagram illustrating an imaging device that captures an image of the inside of a paper feed cassette. [Figure 5] FIG. 10 is a schematic configuration diagram illustrating an example in which an imaging device for imaging a manual feed tray as a sheet stacking device is provided. [Figure 6] FIG. 2 is a control block diagram for executing predetermined processing based on paper information, paper set information, etc. acquired based on image data captured by an imaging device. [Figure 7] FIG. 4 is a control flow diagram of paper size detection control. [Figure 8] FIG. 10 is a diagram showing the state when the paper load is large. [Figure 9] FIG. 10 is a diagram showing a state when the paper stack amount is small. [Figure 10] FIG. 10 is a control flow diagram of paper load amount detection control. [Figure 11] FIG. 2 is a diagram illustrating a state in which paper is set in a paper feed cassette with the side on which an image is formed facing up. [Figure 12] FIG. 10 is a control flow diagram of image presence / absence detection control on the front surface. [Figure 13] 6A and 6B are diagrams for explaining detection of the presence or absence of a gap between a sheet and a side fence, and a gap between a sheet and an end fence by a processing section. [Figure 14] FIG. 10 is a control flow diagram of gap detection control between the paper and the fence. [Figure 15] FIG. 4 is a diagram illustrating detection of the final sheet. [Figure 16] FIG. 10 is a control flow diagram of final sheet detection control. DETAILED DESCRIPTION OF THE INVENTION

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing the outline of a full-color printer, which is an example of an image forming apparatus equipped with a double-sided device according to this embodiment. The printer 100 shown in Figure 1 has an intermediate transfer belt 11 wound around multiple rollers located approximately in the center of the device body 50, and four image-forming units 10 (M, C, Y, Bk) arranged along the lower running edge of the intermediate transfer belt 11.

[0009] Each imaging unit 10 has a photosensitive drum 1 as an image carrier. Around this photosensitive drum 1, a charging means, a developing device, a cleaning means, etc. are arranged, and further, a primary transfer roller 12 as a primary transfer means is provided inside an intermediate transfer belt 11 at a position facing each photosensitive drum 1.

[0010] In this printer 100, the four imaging units 10 are configured with the same structure, but the color of the developer used in the developing device of each imaging unit is different: magenta, cyan, yellow, and black. The four imaging units 10 are arranged in the order of magenta, cyan, yellow, and black from left to right in the figure. Each imaging unit 10 is detachably mounted in the device main body as a process cartridge.

[0011] An optical writing device 14 is provided below the imaging units 10. The optical writing device 14 has a polygon mirror, a group of mirrors, etc., and irradiates the surface of the photosensitive drum 1 of each color imaging unit with optically modulated laser light. Although the optical writing device 14 may be provided individually for each imaging unit 10, it is advantageous in terms of cost to use a common optical writing device. In this printer 100, the intermediate transfer belt 11 and the optical writing device 14 are also unitized, and each is configured to be detachable from the main body of the printer.

[0012] At the bottom of the device, paper feed cassettes 15 are set as sheet stacking devices, and paper feed means 16 corresponding to each paper feed cassette are provided. Paper feed means 16 is composed of a pick-up roller, a supply roller, and a separation roller. A pair of conveying rollers 17 is provided to convey sheets such as transfer paper (hereinafter referred to as paper P) fed by the paper feed means 16. A pair of registration rollers 18 is provided above the pair of conveying rollers 17 (downstream in the paper conveying direction). A transfer roller 19 serving as secondary transfer means is provided above the pair of registration rollers 18, facing a transfer counter roller 13, which is one of the rollers around which the intermediate transfer belt 11 is stretched, to form a secondary transfer section.

[0013] A fixing device 20 is provided above the secondary transfer section, and above the fixing device 20, first to third switching claws 21, 22, and 23 are arranged for switching the paper transport direction. Each switching claw 21 to 23 is driven by an actuator such as a solenoid to switch the paper transport direction. Reference numerals 24 to 27 denote pairs of transport rollers appropriately arranged in the paper transport path. Reference numerals 35 to 41 denote paper sensors appropriately arranged in the paper transport path.

[0014] The top surface of the device main body 50 is configured as a paper discharge tray 30 , and a pair of paper discharge rollers 29 for discharging paper onto the paper discharge tray 30 is provided above and to the left of the fixing device 20 .

[0015] A switchback conveying path 61 and a re-feeding path 62 are formed inside a duplexing unit 60, which is a duplexing device that reverses the front and back of paper P. A first reversing roller pair 31 is provided at the entrance (upper side of the device) of the switchback conveying path 61, and a second reversing roller pair 32 is provided midway through the switchback conveying path 61. The first and second reversing roller pairs 31 and 32 are configured to be rotatable forward and reverse. Furthermore, conveying roller pairs 26 and 27 are disposed at positions that divide the re-feeding path 62 into approximately three equal parts. The aforementioned third switching claw 23 is disposed immediately adjacent to the first reversing roller pair 31, at the entrance from the switchback conveying path 61 to the re-feeding path 62.

[0016] A manual feed tray 33 serving as a sheet stacking device is provided on the side of the duplex unit 60 so that it can be pulled out and stored. FIG. 1 shows the manual feed tray 33 in the pulled-out state. To feed paper P from this manual feed tray 33, a paper feed means 34 consisting of a pick-up roller, a supply roller, and a separation roller is provided. A paper re-feed roller 28 is disposed on the side of the paper feed means 34, inside the device. Driven rollers are respectively pressed against the upper and lower sides of the paper re-feed roller 28. This paper re-feed roller 28 is configured to be rotatable in both forward and reverse directions, and is rotated counterclockwise in the figure when refeding paper P from the paper re-feed path 62, and is rotated clockwise in the figure when feeding paper P from the manual feed tray 33.

[0017] A basic image forming operation in the printer 100 configured as above will now be briefly described. The photosensitive drum 1 of the imaging unit 10 is rotated clockwise in the figure by a driving means, and the surface of the photosensitive drum 1 is uniformly charged to a predetermined polarity by a charging means. The charged photosensitive surface is irradiated with laser light from an optical writing device 14, thereby forming an electrostatic latent image on the surface of the photosensitive drum 1. At this time, the image information exposed to each photosensitive drum 1 is monochromatic image information obtained by decomposing a desired full-color image into color information of magenta, cyan, yellow, and black. Toner of each color is applied from a developing device to the electrostatic latent image thus formed, and it is visualized as a toner image.

[0018] Furthermore, the intermediate transfer belt 11 is driven to run counterclockwise as shown by the arrow in the figure, and in each image forming unit 10, the action of the primary transfer roller 12 causes the toner images of each color to be transferred in succession from the photosensitive drum 1 to the intermediate transfer belt 11. In this way, the intermediate transfer belt 11 carries a full-color toner image on its surface. It is also possible to form a single color image, or a two- or three-color image using any one of the image forming units 10. For monochrome printing, the image is formed using the Bk unit on the far right of the four image forming units in the diagram.

[0019] After the toner image is transferred, residual toner remaining on the surface of the photosensitive drum is removed from the surface of the photosensitive drum by a cleaning device, and then the surface is subjected to the action of a static eliminator to initialize the surface potential and prepare for the next image formation.

[0020] Meanwhile, paper is selectively fed from paper feed cassette 15 or manual feed tray 33 and is sent by registration roller pair 18 toward the secondary transfer position in time with the toner image carried on intermediate transfer belt 11. A transfer voltage of opposite polarity to the toner charge polarity of the toner image on the surface of the intermediate transfer belt is applied to transfer roller 19, thereby transferring the toner image on the surface of the intermediate transfer belt all at once onto the paper. When paper P with the transferred toner image passes through fixing device 20, the toner image is fused and fixed to paper P by heat and pressure. The fixed transfer material is discharged by paper discharge roller pair 29 to paper discharge tray 30 located on the top surface of device main body 50.

[0021] FIG. 2 is an explanatory diagram of the conveying path of the full-color printer. The solid line [1] in FIG. 2 indicates the paper transport path during single-sided printing (when paper is fed from the paper feed cassette 15). The dashed line [2] in Figure 2 indicates the paper transport path (after passing through the fixing device) when paper P is discharged to the optional tray. This printer 100 can be equipped with an optional paper output tray (for example, a four-bin tray with a sorting function) on the top surface of the device above the second switching claw 22. The dashed line [2] in Figure 2 indicates the paper transport path for discharging paper P after fixing to the optional tray.

[0022] The two-dot chain line [3] in Figure 2 indicates the transport path when paper enters the switchback transport path 61. When printing on both sides of the paper, the paper P with a toner image fixed on one side of the paper is entered into the switchback transport path 61 by appropriately switching the first to third switching claws 21 to 23. In this case, the first and second switching claws 21, 22 are switched to the positions shown by the imaginary lines in Figure 2. The third switching claw 23 is also switched to the position shown by the solid line in Figure 2. The first and second reversing roller pairs 31, 32 are also rotated in the forward direction (clockwise in Figure 1). When the sensor 40 detects the rear end of the paper that has entered the switchback conveying path 61, the first and second reversing roller pairs 31 and 32 are rotated in the opposite direction (counterclockwise in FIG. 1) to reverse the paper P. At this time, the third switching claw 23 is switched to the position shown by the imaginary line in FIG. 2, so that the reversed paper P is sent to the re-feeding path 62.

[0023] The dashed line [4] in FIG. 2 indicates the paper transport path through the paper re-feed path 62 (however, from the third switching claw 23 to the part where it joins with the solid line [1]). The paper re-feed path 62 merges with the paper transport path from the manual feed tray 33 at its lower end, and further merges with the paper transport path from the paper feed cassette 15 at the rear side of the paper re-feed roller 28. The paper is transported in the paper re-feed path 62 by the transport roller pairs 26 and 27, and is further sent to the registration roller pair 18 by the paper re-feed roller 28.

[0024] The paper P that has been inverted in the switchback conveying path 61 is passed through the re-feeding path 62, whereby the paper is turned over, and a toner image is transferred from the intermediate transfer belt 11 to the back side of the paper, and the back side image is fixed by the fixing device 20. The paper P, which carries images on both sides, is conveyed to the paper conveying path (dashed line [2]) when ejecting to the paper output tray 30 or an optional tray, and then ejected to the optional tray, completing the double-sided print.

[0025] 2 indicates the paper transport path when paper P is fed from manual feed tray 33 (up to the position past re-feed roller 8).

[0026] FIG. 3 is a schematic perspective view showing a sheet feed cassette 15 serving as a sheet stacking device. The paper feed cassette 15 has a tray housing 101 that is a storage housing for storing paper sheets P. The tray housing 101 is provided with two side fences 102 as regulating members, an end fence 103 as a regulating member, and a bottom plate 104 as a sheet stacking portion.

[0027] The two side fences 102 are movable in the width direction to match the size of the paper P set in the paper feed cassette 15, and after setting the paper P, the user can move them to match the width of the paper P, allowing them to abut against both widthwise ends of the stack of paper P. This regulates the position of the paper P in the width direction within the tray housing 101.

[0028] The end fence 103 is movable in the feeding direction, and after setting the sheets P, the user moves the end fence 103 downstream in the feeding direction until it abuts against the rear end of the stack of sheets P. By abutting the end fence 103 against the rear end of the sheets P, the front end of the sheets P abuts against the front wall 101a of the tray housing 101, and the position of the sheets P in the feeding direction within the tray housing 101 is regulated.

[0029] The bottom plate 104 is held rotatably about a bottom plate rotation shaft 104a relative to the tray housing 101, and supports the underside of the downstream side (the leading edge side of the paper) in the feeding direction of the stored paper P, with the downstream end portion in the feeding direction moving up and down. When a large number of sheets of paper P are set, the downstream end portion in the feeding direction of the bottom plate 104 is in a lowered state, and when the number of sheets of paper P set decreases, it rises, maintaining a state in which the leading edge side end portion of the upper surface of the paper P is in contact with the pick-up roller of the paper feed means 16. This allows the paper P to be sent to the next process regardless of the number of sheets of paper P set.

[0030] The inner surface of the tray housing 101 of the paper feed cassette 15, the side fence 102, the end fence 103 and the bottom plate 104 are optically different from the white paper P in that they have different colors, reflectances, textures, etc., so that they can be distinguished from the paper P.

[0031] FIG. 4 is a schematic diagram illustrating the configuration of an imaging device 110 that captures an image of the inside of the paper feed cassette 15. As shown in FIG. The imaging device 110 has an imaging unit 111 formed of a CCD or CMOS sensor or the like, and an optical unit 112 formed of lenses, mirrors, and the like. As shown by the dashed-dotted line in the figure, the imaging device 110 is configured so that the entire interior of the paper feed cassette 15 is within an imaging range S. The imaging device 110 uses an ultra-wide-angle lens, such as a fisheye lens, as the optical unit 112, so that the entire interior of the paper feed cassette 15 can be imaged. Alternatively, a rotatable mirror may be used as the optical unit 112, and the entire interior of the paper feed cassette may be imaged by scanning with the mirror. The imaging device 110 also has an illumination unit that illuminates the interior of the paper feed cassette, and the illumination unit is turned on when imaging the interior of the paper feed cassette.

[0032] In this way, by configuring the optical unit 112 so that it can capture the entire surface of the paper in the paper feed cassette 15, a movement mechanism for moving the imaging unit 111 is not required, and the imaging device 110 can be provided without increasing the size of the device body.

[0033] As described above, in the present paper feed cassette 15, the inner surface of the tray housing 101, the side fences 102, the end fence 103, and the bottom plate 104 are optically differentiated from the paper P. This allows the paper P to be easily recognized from the image captured by the imaging device 110.

[0034] FIG. 5 is a schematic diagram illustrating an example in which a manual feed imaging device 120 for imaging the manual feed tray 33 as a sheet stacking device is provided. 5, a manual-feed imaging device 120 is disposed on the right side of the device body 50 in the figure, above the manual feed tray 33. The manual feed imaging device 120 also has an imaging section 111 formed of a CCD, CMOS sensor, etc., and an optical section 112 formed of lenses, mirrors, etc. An ultra-wide-angle lens such as a fisheye lens is used as the optical section 112 so that the entire manual feed tray 33 becomes the imaging range S.

[0035] Regarding the manual feed tray 33, the sheet placement surface as a sheet stacking portion of the manual feed tray 33, the side fence 33a, has an optical difference from the white paper P, such as a different color, a different reflectance, or a different texture.

[0036] Based on the image data captured by the imaging devices 110 and 120, the system obtains information about the paper sheets set in the paper feed cassette 15 (paper size, presence or absence of an image, etc.) and paper set information (number of sheets loaded, restriction status by side fences and end fences), and then executes a predetermined process based on the paper information and paper set information based on the image data.

[0037] FIG. 6 is a control block diagram for detecting paper information, paper set information, and the like based on image data captured by the imaging device 110, and for executing predetermined processing based on the detection results. 6 processes image data captured by the imaging devices 110 and 120. The processing unit 80 performs image processing such as contrast processing and keystone correction on the image data captured by the imaging devices 110 and 120, and acquires paper information and paper set information.

[0038] The storage unit 90 is comprised of a HDD, flash memory, etc., and stores information such as determination information for whether or not to execute a predetermined process based on paper information and paper set information acquired from image data. For example, standard paper size data for specifying the size of the set paper, and threshold values ​​for determining whether the paper set status is normal, etc. are stored.

[0039] The operation panel 70 as a notification means functions as an input receiving unit that receives various instruction inputs in response to user operations, and also has a notification function that displays and notifies various information (such as received operation information, information indicating the printer's operating status, information indicating the setting status, etc.).

[0040] The operation panel 70 is configured, for example, by a liquid crystal display (LCD) equipped with a touch panel function, but is not limited to this. For example, it may be configured by an organic electroluminescence (EL) display equipped with a touch panel function. Furthermore, in addition to or instead of this, an operation unit such as hardware keys and a display unit such as a lamp may be provided. Furthermore, an audio unit such as a speaker may be provided as a notification unit to notify the user by voice.

[0041] The processing unit 80 performs a determination process, which will be described in Examples 1 to 5 below, based on the paper information and paper set information acquired through image processing and the determination information stored in the storage unit 90. Then, based on the determination result, result information, etc. is displayed on the operation panel 70 to notify the user.

[0042] Next, the detection of paper information and paper set information based on image data captured by the imaging device 110 will be described in detail.

[0043] [Example 1] The first embodiment is an embodiment in which the paper size is detected as paper information based on image data captured by the imaging device 110.

[0044] Automatic paper size detection has been performed for some time, automatically detecting the size of paper loaded in paper feed cassette 15, manual feed tray 33, etc. Conventional automatic paper size detection methods identify the positions of side fence 102 and end fence 103 by providing information to sensors or switches using levers that move in conjunction with side fence 102 and end fence 103. Most conventional methods then detect the standard size based on the identified positions of side fence 102 and end fence 103.

[0045] The method of detecting the paper size based on the positions of the side fence 102 and the end fence 103 can detect the correct paper size by having the user abut the side fence 102 or the end fence 103 against the paper and regulate the position correctly after loading the paper in the paper feed cassette 15 or the manual feed tray 33. Therefore, if the user forgets to operate the side fence 102 or the end fence 103 and the side fence 102 or the end fence 103 does not abut the paper (there is a large gap between the paper and the fence), the paper size will be detected incorrectly.

[0046] Furthermore, if the user operates the side fence 102 or the end fence 103 to bring the side fence 102 or the end fence 103 into contact with the paper, but then forcefully or roughly returns the paper feed cassette 15 to the device main body 50, the end fence 103 or the side fence 102 may move due to play. As a result, the side fence or the end fence may not come into contact with the paper, which could result in an incorrect detection of the paper size. If the paper size is incorrectly detected, various problems may occur, such as incorrect image position, paper not being fed, paper jams, skew, and wrinkles.

[0047] In contrast, in the first embodiment, the paper size is detected based on image data captured by the imaging device 110. This makes it possible to accurately detect the paper size even when the side fence 102 or the end fence 103 is not in contact with the paper due to, for example, the user forgetting to operate the side fence 102 or the end fence 103.

[0048] FIG. 7 is a control flow diagram of the paper size detection control. 7, detection of the size of the paper set in the paper feed cassette 15 will be described. The paper feed cassette 15 is pulled out from the device body and paper is set in the paper feed cassette 15 (S1). The imaging device 110 starts imaging at a predetermined timing and acquires image data of the entire paper feed cassette (S2 to S4). After acquiring the image data, the processing unit 80 identifies the size of the paper set in the paper feed cassette (S5).

[0049] An example of the predetermined timing for starting imaging is when the set detection sensor, which detects the setting of the paper feed cassette 15 in the device body, switches from a state where it does not detect the setting to a state where it detects the setting. At this time, it is possible that the paper in the paper feed cassette 15 has been replaced. Therefore, it is preferable to take an image of the inside of the paper feed cassette and identify the size of the paper that has been set when the sensor switches from a state where it does not detect the setting to a state where it detects the setting. Also, because it is possible that the paper in the paper feed cassette 15 has been replaced while the device is turned off, it is preferable to take an image of the inside of the paper feed cassette and identify the size of the paper that has been set even when the device is turned on.

[0050] In this way, if an image of the inside of the paper feed cassette is taken before printing and the set paper size is identified, the paper size information set in this paper feed cassette is displayed on the operation panel, etc. (S6). Then, when printing, it is preferable that paper sizes other than the set paper size cannot be selected.

[0051] In addition, examples of predetermined times for starting imaging include when printing begins, such as when the user operates the operation panel 70 to select the paper size to be printed on, when a paper feed command is received, or when the user presses the start button on the operation panel.

[0052] When starting printing in this manner, if an image of the inside of the paper feed cassette is taken to identify the paper size set therein, after the paper size is identified, it is determined whether it differs from the paper size set by the user through operation panel 70. If the identified paper size differs from the paper size set by the user, the identified paper size information is displayed on operation panel 70 (S6). The operation panel 70 also displays a message such as "Please set the correct size paper in the paper feed cassette" (S7-1).

[0053] To identify the paper size based on the image data captured by the imaging device 110, the processing unit 80 first performs predetermined image processing on the image data to identify the paper set in the paper feed cassette. Next, the processing unit 80 acquires standard size paper size data from the storage unit 90. Based on the standard size paper size data obtained from the storage unit 90, the processing unit 80 identifies standard size paper size data that matches the paper data obtained from the image data. Based on the identified paper size data, the processing unit 80 identifies the size (standard size) of the paper set in the paper feed cassette 15.

[0054] As the standard size paper size data stored in the storage unit 90, for example, image data captured in advance of setting standard size paper in a paper feed cassette can be used.

[0055] The imaging device 110 captures an image of the entire interior of the paper feed cassette, so it can capture an image of all the paper sheets set in the paper feed cassette. This makes it possible to accurately detect the width dimension of the paper sheets and the length of the paper sheets in the sheet conveyance direction, and therefore to accurately detect the paper size.

[0056] As described above, the inner surface of the tray housing 101, the side fences 102, the end fence 103, and the bottom plate 104 of the paper feed cassette 15 are optically differentiated from the paper P. This allows the boundary between the paper and the components of the paper feed cassette 15 to be accurately determined from the image data captured by the imaging device 110, and the paper can be detected well from the image data.

[0057] Furthermore, for example, by providing a reference mark serving as a measurement reference at a predetermined position on the tray housing 101, it is possible to accurately identify the set paper size and compare it with standard paper size data stored in advance in a storage unit. This is preferable because it allows for highly accurate identification of the paper size. The reference mark may be a sticker, may be printed directly on the tray housing 101, or may be engraved into the tray housing 101.

[0058] For manual feed tray 33, the predetermined timing for starting imaging is when a paper set detection sensor that detects that paper has been set in the manual feed tray detects that paper has been set. As with the paper feed cassette, imaging may also be started at the start of printing, such as when a user operates operation panel 70 to select the paper size to be printed, when a paper feed command is received, or when the user presses the start button on the operation panel.

[0059] [Example 2] In the second embodiment, the amount of paper stacked is detected as paper set information based on image data captured by the imaging device 110.

[0060] Although a mark indicating the upper limit of the stacking position (reference numeral 105 in Figure 8) is printed on the side fence 102 etc., some users may load paper above this upper limit, resulting in an overload. If the paper loaded in the paper feed cassette is overloaded, the bottom plate lift function will not function properly, which may result in a false detection of a tray abnormality and a temporary inoperability of the device, such as requiring a service call.

[0061] In contrast to this, in this second embodiment, the amount of paper stacked is detected based on image data captured by the imaging device 110, so when there is an overload or when the loaded paper runs out, the user can be notified and asked to reload the paper, etc. Also, when the bottom plate lifting function does not function properly, the imaging device 110 detects whether there is an overload from the image data captured, and when there is an overload, it can be determined that there is no tray abnormality, making it possible to reduce downtime of the device due to false detection of a tray abnormality.

[0062] FIG. 8 is a diagram showing the state when the amount of paper stacked is large, and FIG. 9 is a diagram showing the state when the amount of paper stacked is small. 8 and 9, in the second embodiment, a detection mark 106 for detecting the amount of paper stacked is formed on the leading edge in the sheet conveyance direction of one of the two side fences 102. This detection mark 106 is a mark that allows easy distinction from paper and paper feed cassette parts such as the side fences from captured image data.

[0063] As shown in Fig. 8, when the number of loaded sheets is large, the portion of the detection mark 106 that is hidden by the loaded sheets increases, and the exposed area of ​​the detection mark 106 is small. On the other hand, as shown in Fig. 9, when the number of loaded sheets is small, the portion that is hidden by the loaded sheets decreases, and the exposed area of ​​the detection mark 106 increases.

[0064] In the second embodiment, the exposed area of ​​the detection mark 106 is calculated based on the captured image data, and the paper load amount is detected based on the calculated exposed area. For example, if this exposed area is less than a threshold, it is determined that the paper is overloaded, and the user is prompted to reload the paper. In addition, the relationship between the paper load amount and the exposed area of ​​the detection mark 106 is checked in advance, and the paper load amount is determined based on the calculated exposed area.

[0065] 8 and 9, the detection mark 106 is provided on the leading edge of the side fence 102 in the sheet conveyance direction, but it may also be provided on the trailing edge of the side fence 102 in the sheet conveyance direction. The detection mark may also be provided on the end fence. For example, a reference mark may be provided as a height reference, and the paper load amount may be detected from the distance between this reference mark and the top surface of the paper stack. The height of the leading edge of the top surface of the paper stack is kept constant by the bottom plate 104, so the paper load amount is detected from the distance between the trailing edge of the top surface of the paper stack and the reference mark.

[0066] FIG. 10 is a control flow diagram of the paper stack amount detection control. The paper stack amount detection control also starts imaging at the same timing as the paper size detection, and acquires image data of the entire paper feed cassette (S11 to S14). After acquiring the image data, the processing unit 80 detects the amount of paper stacked in the paper feed cassette 15 (S15).

[0067] When the setting detection sensor that detects the setting of paper feed cassette 15 in the device body switches from a state where it does not detect setting to a state where it detects setting, it is possible that paper has been added or replaced in paper feed cassette 15. As a result, the amount of paper loaded may have changed. Therefore, when the sensor switches from a state where it does not detect setting to a state where it detects setting, it is preferable to capture an image of the inside of the paper feed cassette to detect the amount of paper loaded. Also, because it is possible that paper has been replaced in paper feed cassette 15 while the device is powered off, it is preferable to capture an image of the inside of the paper feed cassette to detect the amount of paper loaded even when the device is powered on.

[0068] By detecting the amount of paper loaded when paper feed cassette 15 is set in the device body or when the power is turned on, if there is an overload of paper, a message indicating that there is an overload of paper is displayed on the operation panel, urging the user to reload paper (S17-1). Also, if there is no paper loaded in the paper feed cassette because paper was forgotten to be loaded, a message indicating that there is no paper is displayed on the operation panel 70, urging the user to load paper (S17-1).

[0069] To detect the paper load amount based on the image data captured by the imaging device 110, the processing unit 80 first performs predetermined image processing on the image data to identify the detection mark 106 and calculates the area of ​​the identified detection mark 106. Next, the processing unit 80 reads a threshold value for determining whether or not there is an overload from the memory unit 90, and determines that there is an overload if the calculated area of ​​the detection mark 106 is less than the threshold value. If there is an overload, as shown in S17-1, a message indicating that there is an overload is displayed on the operation panel 70, and the user is prompted to reduce the number of sheets in the paper stack and reset it.

[0070] Furthermore, when the processing unit 80 cannot detect paper from the image data, it determines that there is no paper, and displays a message on the operation panel 70 to that effect, prompting the user to set paper (S17-1).

[0071] If the image data detects paper and the calculated area of ​​the detection mark 106 is equal to or greater than the threshold, data indicating the relationship between the number of stacked sheets and the area of ​​the detection mark is read from the memory unit 90. Then, the number of stacked sheets is determined from the calculated area of ​​the detection mark 106 and the data indicating the relationship between the number of stacked sheets and the area of ​​the detection mark, and the determined number of stacked sheets is displayed on the operation panel as the remaining paper amount (S16). Note that the detection of the number of stacked sheets based on this image data is performed when the paper feed cassette 15 is inserted into the device body or when the power is turned on, and thereafter the number of stacked sheets is reduced according to the number of printed sheets. Alternatively, the operation panel 70 may display a rough remaining amount of paper, such as "XX%."

[0072] Furthermore, an image may be taken by the imaging device 110 each time printing is completed or after a predetermined number of sheets have been printed, and the number of sheets loaded may be identified by calculating the area of ​​the detection mark 106. Furthermore, if the amount of remaining paper falls below a predetermined value, imaging may be started after paper has been fed (after the rear end of the paper has left the paper feed cassette 15), and the presence or absence of paper may be detected based on the image data.

[0073] In this way, by displaying the amount of remaining paper on the operation panel 70, the user can replenish the paper feed cassette with paper when the paper is running low, based on the amount of remaining paper displayed on the operation panel. As a result, it is possible to prevent the occurrence of paper shortages. Furthermore, when the paper is running low, it is possible to prepare paper to be loaded, which makes it possible to prevent situations in which the machine runs out of paper and there is no paper to replenish, resulting in downtime.

[0074] [Example 3] The third embodiment is an embodiment in which, based on image data captured by the imaging device 110, it is detected whether or not an image exists on the surface (front surface) of the paper on which the image is to be printed, as paper information.

[0075] Recently, the use of reversed paper (reusing paper that has already been printed on one side) has become more common from the perspective of recycling and energy conservation. However, when using reversed paper, as shown in Figure 11, there are cases where the paper is loaded upside down and the side with the image on it is loaded as the front side. In this case, the image to be printed this time overlaps the previously printed image ("R" in the figure), and the desired image cannot be obtained.

[0076] Conventionally, there is a device that checks whether or not there is an image on the front side of the paper before the pair of registration rollers 18, but with this conventional device, when it is determined that there is an image on the front side, image formation has already begun, so the formed toner image is discarded (forced cleaning) and toner is wasted.

[0077] In contrast to this, in the third embodiment, it is possible to determine whether or not there is an image on the front side of a sheet of paper when the sheet is set in the paper feed cassette 15 or the manual feed tray 33. This makes it possible to determine whether or not there is an image on the front side of a sheet of paper before the image formation operation, thereby reducing unnecessary consumption of toner.

[0078] FIG. 12 is a control flow diagram of the image presence / absence detection control on the front surface. The control to detect the presence or absence of an image on the front side also starts imaging at the same timing as the paper size detection, and acquires image data of the entire contents of the paper feed cassette (S21 to S24). After acquiring the image data, the processing unit 80 detects whether or not there is an image on the front side of the paper set in the paper feed cassette.

[0079] When the setting detection sensor that detects the setting of paper feed cassette 15 in the device body switches from a state where it does not detect setting to a state where it detects setting, there is a risk that the paper in paper feed cassette 15 has been replaced with paper on the back side (paper with an image printed on one side). Therefore, when the sensor switches from a state where it does not detect setting to a state where it detects setting, an image of the inside of the paper feed cassette is taken to detect whether or not there is an image on the front side of the set paper. In addition, there is a risk that the paper in paper feed cassette 15 has been replaced with paper on the back side when the device is turned off. Therefore, even when the device is turned on, an image of the inside of the paper feed cassette is taken to detect whether or not there is an image on the front side of the set paper.

[0080] Note that the imaging device 110 may take an image for detecting the presence or absence of an image on the front surface at any timing before the start of image formation, and may take an image at any timing other than that described in S22 in FIG.

[0081] To detect the presence or absence of an image on the front side based on the image data captured by the imaging device 110, the processing unit 80 checks whether or not there is an image other than the color of the paper (white) within the detection range of the paper in the captured image data. If there is an image other than the color of the paper (white), it is determined that there is an image on the front side of the paper.

[0082] Also, for example, if there is no paper color (white) within the paper detection range, it is determined that there is no paper. On the other hand, if there is a paper color (white) within the paper detection range and an image of a color other than the paper color (white) within the paper detection range, it may be determined that there is an image on the front side.

[0083] When the processing unit 80 determines that an image exists on the front side of the paper (S25-1), a message indicating that an image exists on the front side of the paper is displayed on the operation panel 70. Furthermore, a warning message is displayed (S26-1) to prompt the user to check the paper set in the paper feed cassette 15. In addition to this warning message, an "OK" button is also displayed.

[0084] When the user presses the OK button, the printer enters a state in which paper can be fed (S27-1). Meanwhile, if the user pulls out the paper feed cassette and the load detection is turned OFF in order to load paper into the paper feed cassette again (S28-1), the warning display is cleared. Then, when the load detection is switched from OFF to ON, an image of the inside of the paper feed cassette is captured again to detect whether or not there is an image of the front side of the paper. This makes it possible to prevent the image to be printed this time from unintentionally overlapping the image that was printed previously, and to prevent the wasteful consumption of toner.

[0085] Furthermore, if the loaded paper is wavy, curled, or folded, a shadow will appear on the paper portion of the image data. This shadow may lead the processing unit 80 to determine that an image other than the paper color (white) is present in the paper detection area. Therefore, it is preferable to be able to determine whether an image other than the paper color (white) is an image corresponding to the wavy, curled, or folded color, or an image formed on the front side. For example, by learning images corresponding to the wavy, curled, or folded color using deep learning or the like, it is possible to determine whether an image other than the paper color (white) is an image corresponding to the wavy, curled, or folded color.

[0086] When waving, curling, or folding is detected in the loaded paper, it means that the loaded paper has waving, curling, or folding, and there is a possibility that a paper jam may occur. Therefore, when the processing unit 80 detects waving, curling, or folding, it is preferable to display the state of the loaded paper, such as waving, curling, or folding, on the operation panel 70 and prompt the user to replace the paper. This makes it possible to prevent paper jams from occurring.

[0087] [Example 4] The fourth embodiment is an embodiment in which, based on image data captured by the imaging device 110, the presence or absence of a gap between the paper and the side fence 102 and the gap between the paper and the end fence 103 is detected as paper set information.

[0088] If the user fails to regulate the position of the loaded paper by forgetting to set the side fence 102 or end fence 103 or by not gathering it properly, non-feeding, paper jams, paper skew, and paper wrinkles may occur. Also, image position errors may occur, where the image is not formed in the intended position on the paper.

[0089] In contrast, in the fourth embodiment, the presence or absence of a gap between the paper and the side fence 102 and the gap between the paper and the end fence 103 is detected based on image data captured by the imaging device 110, and it is possible to determine whether the paper is correctly positioned. As a result, if the position of the loaded paper is not correctly regulated due to forgetting to set the side fence 102 or the end fence 103 or not gathering the paper enough, the user can be prompted to operate the side fence 102 or the end fence 103. This makes it possible to prevent non-feeding, paper jams, paper skew, and paper wrinkles. It also makes it possible to prevent image position errors, in which an image is not formed at the intended position on the paper.

[0090] FIG. 13 is a diagram for explaining detection by the processing unit 80 of the presence or absence of a gap between the paper and the side fence 102 and a gap between the paper and the end fence 103. In FIG. The processing unit 80 obtains the paper length PL and paper width PW from the image data captured by the imaging device 110. Specifically, the paper size is identified by the method described in the first embodiment, and the paper length PL and paper width PW can be obtained from the identified paper size.

[0091] The processing unit 80 also measures the distance between the pair of side fences 102 from the captured image data. To enable the processing unit 80 to easily determine the position of the side fences 102 from the image data, it is preferable to provide the side fences 102 with position detection marks that distinguish them from other components inside the paper feed cassette. The processing unit 80 then detects the gap between the side fences 102 and the paper based on the measured distance between the pair of side fences 102 and the paper width.

[0092] The processing unit 80 also measures the length from the front wall 101a of the tray housing 101 to the end fence 103 from the captured image data. In this case, too, it is preferable to provide position detection marks on the end fence 103 and the front wall 101a that distinguish them from components inside the paper feed cassette, so that the processing unit can easily determine the positions of the end fence 103 and the front wall 101a from the image data. The processing unit 80 then detects the gap between the end fence 103 and the paper from the measured length from the front wall 101a to the end fence 103 and the length of the paper.

[0093] FIG. 14 is a control flow diagram of the gap detection control between the paper and the fence. Imaging is started at the same timing as paper size detection, and image data of the entire paper feed cassette is acquired (S31 to S34). After acquiring the image data, the processing unit 80 identifies the paper size and measures the distance between the pair of side fences 102 and the length from the front wall 101a to the end fence 103 (S35).

[0094] Next, the processing unit 80 calculates the difference between the paper width obtained from the specified paper size and the distance between the side fences 102, and detects the gap between the paper and the side fences 102. It also calculates the difference between the paper length obtained from the specified paper size and the length from the front wall 101a to the end fence 103, and detects the gap between the paper and the end fence 103 (S36).

[0095] Next, the processing unit 80 reads the threshold value for the gap between the fence and the paper from the memory unit 90, and determines whether the calculated gap between the paper and the side fence 102 is equal to or greater than the threshold value. It also determines whether the calculated gap between the paper and the end fence 103 is equal to or greater than the threshold value (S37).

[0096] If the calculated gap between the paper and the side fence 102 or the gap between the paper and the end fence 103 is equal to or greater than the threshold (S38-1), a message indicating that the paper is not correctly positioned is displayed on the operation panel 70. Also, a message urging the user to check the end fence 103 and the side fence 102 is displayed, along with an "OK" button (S39-1).

[0097] When the user presses the OK button, the printer is ready to feed paper. Meanwhile, to check the positions of the end fence 103 and the side fence 102, the user pulls out the paper feed cassette 15, and when the set detection is turned OFF, the warning display is cleared. Then, when the set detection is switched from OFF to ON, an image of the inside of the paper feed cassette is captured again to check whether the end fence 103 and the side fence 102 are correctly regulating the paper position. This makes it possible to prevent the paper from being unintentionally fed without being positioned by the end fence 103 and the side fence 102.

[0098] [Example 5] The fifth embodiment is an embodiment in which it is detected whether the set sheet is the last sheet based on image data captured by the imaging device 110.

[0099] Conventionally, a message was displayed urging the user to load paper into the paper feed cassette 15 only after the paper ran out, so when printing continuously, it was necessary to discard the image-forming toner after the last sheet (forced cleaning).

[0100] In contrast, in the fifth embodiment, the last sheet of loaded paper is detected based on the captured image data, so that during continuous printing, the image forming operation can be temporarily stopped after forming an image on the last sheet of paper based on this detection result. This prevents the occurrence of a situation where the image forming toner after the last sheet is discarded (forced cleaning) and reduces the wasteful consumption of toner.

[0101] FIG. 15 is a diagram for explaining the detection of the last sheet. The leading edges of the top few sheets of paper in the stack of sheets on the bottom plate do not face the front wall 101a, and the front wall 101a does not restrict the movement of the sheets downstream in the paper transport direction. Furthermore, the paper feed unit 16 forms a separation nip by abutting a separation roller against the supply roller downstream in the paper transport direction from the pick-up roller, separates multiple sheets transported by the pick-up roller at the separation nip, and transports the topmost sheet toward the pair of registration rollers. Therefore, in most cases, when the topmost sheet of the stack of sheets is fed, the second sheet directly below the topmost sheet also moves into the separation nip due to frictional forces, etc. Therefore, the next sheet to be transported is located downstream in the paper transport direction from the paper set position.

[0102] When the sheet before the last sheet is fed by the sheet feeding means 16, the last sheet moves to the vicinity of the separation nip together with the sheet before the last sheet, as shown in Fig. 15. Therefore, by detecting the movement of the rear end position of the sheet detected from the captured image data, it is possible to determine whether or not the sheet in the paper feed cassette is the last sheet.

[0103] FIG. 16 is a control flow diagram of the final sheet detection control. The paper feed means 16 is driven to start feeding paper (S41), and after a predetermined time has passed, the imaging device 110 starts capturing an image of the inside of the paper feed cassette, and image data of the image captured inside the paper feed cassette is obtained (S42).

[0104] Next, the processing unit 80 detects the position of the rear end of the paper in the paper feed cassette based on the captured image data. The position of the rear end of the paper is detected from the boundary between the paper image portion (white image) of the image data and a colored image showing the bottom plate or the inner surface of the tray housing 101. The processing unit 80 also detects the position of the end fence 103 based on the captured image data. It is preferable to provide a position detection mark on the end fence 103 that distinguishes it from components inside the paper feed cassette and detect the position of the end fence 103 based on this position detection mark, as this makes it easier to detect the position of the end fence 103. Next, the processing unit 80 measures the gap between the rear end of the paper and the end fence 103 based on the detected positions of the rear end of the paper and the end fence 103 (S44).

[0105] Next, the processing unit 80 reads out the gap between the trailing edge of the paper and the end fence 103, measured based on image data captured when the paper was set and stored in the memory unit 90, and the threshold value for detecting the last paper. Then, the processing unit 80 calculates the difference between the gap between the trailing edge of the paper and the end fence 103 this time and the gap between the trailing edge of the paper and the end fence 103 when the paper was set, and measures the increase in the gap between the trailing edge of the paper and the end fence 103.

[0106] If there are three or more sheets of paper in the paper feed cassette when feeding starts, the leading edge of the last sheet of paper in contact with the bottom plate 104 abuts against the front wall 101a, restricting movement in the paper transport direction. Therefore, the last sheet of paper is not moving, and the increase in the gap between the trailing edge of the paper and the end fence 103 is almost zero. Therefore, in this case, the increase is below the threshold, and the processor 80 determines that this is not the last sheet of paper (S45-2).

[0107] On the other hand, if there are two sheets of paper in the paper feed cassette when feeding starts, the leading edge of the last sheet does not abut against the front wall 101a. Therefore, when feeding starts, the last sheet is transported to the separation nip together with the second sheet. As a result, the increase in the gap between the trailing edge of the paper and the end fence 103 when the paper is set exceeds the threshold value. This means that it is detected that there is only one sheet of paper left in the paper feed cassette.

[0108] In the above description, whether the paper is the last or not is determined based on the increase in the gap between the end fence and the paper when the paper is set, but it is also possible to determine that the last paper has moved if the gap between the paper and the end fence 103 exceeds a threshold value and determine that it is the last paper.

[0109] If the increase in the gap between the trailing edge of the paper and the end fence 103 exceeds a threshold and the processing unit 80 detects that there is only one sheet of paper left in the paper feed cassette (S45-1), a message indicating that there is no paper is displayed on the operation panel 70 after the next paper feed (S46-1). Alternatively, the out-of-paper notification may be made by sound such as a buzzer.

[0110] When the processor 80 detects that there is only one sheet of paper left in the paper feed cassette, a message indicating that the next sheet is the last may be displayed on the operation panel 70. This allows paper to be prepared before the paper cassette runs out, and allows paper to be replenished in the paper feed cassette 15 when or before the paper cassette runs out.

[0111] Furthermore, when the last sheet of paper is detected during continuous printing, the image formation operation is temporarily stopped at the next image formation, and an out-of-paper message is displayed on the operation panel 70. This reduces the waste of toner. Also, since the user can be notified that they have run out of paper before the last sheet of paper is fed, they can prepare replenishment paper more quickly than if they were notified that they have run out of paper after the last sheet of paper has been fed, and continuous printing can be resumed sooner.

[0112] The printer may have any one of the above-described embodiments 1 to 5, or may have a plurality of embodiments 1 to 5, or may have all of embodiments 1 to 5. Furthermore, while the above-described embodiments 1 to 5 have been described with respect to the paper feed cassette 15, embodiments 1 to 5 can also be adopted for the manual feed tray 33.

[0113] The above description is merely an example, and each of the following aspects provides unique effects. (Aspect 1) A sheet stacking device such as a paper feed cassette 15 is provided with a sheet stacking section such as a bottom plate 104 for stacking sheets such as paper P, and an imaging means such as an imaging device 110 for imaging the entire sheets stacked on the sheet stacking section, and detects the size of the sheets stacked on the sheet stacking section based on image data captured by the imaging means. In the sheet stacking device described in Patent Document 1, the user may forget to operate the side fences, which may result in the side fences not abutting the widthwise edges of the sheet and not restricting the sheet's position. Furthermore, structural play may create a gap between the side fences and the widthwise edges of the sheet. If the side fences do not abut the widthwise edges of the sheet, the position of the side fences does not correspond to the widthwise position of the sheet. As a result, sheet size information detected based on the position of the side fences may be incorrect. In contrast, in the first aspect, the imaging unit captures an image of the entire sheet stacked on the sheet stacking section, and the width and length of the sheet in the conveying direction can be determined based on the captured image data, thereby enabling the sheet size to be detected. This allows the sheet size to be detected with high accuracy even if the side fences do not abut against the sheets.

[0114] (Aspect 2) In aspect 1, an imaging means such as the imaging device 110 simultaneously captures an image of the sheets loaded on a sheet loading section such as the bottom plate 104 and a detection mark for detecting the height position of the sheets, and detects the amount of sheets loaded on the sheet loading section based on the image data obtained by simultaneously capturing the image of the detection mark and the sheets loaded on the sheet loading section. According to this, as explained in the second embodiment, by simultaneously capturing an image of the sheets loaded on the sheet loading section such as the bottom plate 104 and the detection mark 106 for detecting the height position of the sheets, it is possible to grasp the relationship between the detection mark 106 and the sheets loaded on the sheet loading section (in the second embodiment, the area of ​​the detection mark 106 that is not hidden by the sheets, which changes depending on the sheet height) based on the image data captured by the imaging means. As a result, it is possible to grasp the amount of sheets loaded on the sheet loading section based on the image data captured by the imaging means. By detecting the sheet load amount, it is possible to detect an overloaded state or when there is no paper loaded, and to notify the user and request that the paper be reloaded, etc. Furthermore, when there is an operational abnormality in the sheet stacking section such as the bottom plate, it is possible to determine whether the operational abnormality is due to an overloaded state, and it is possible to prevent downtime of the device due to false detection of an operational abnormality. Furthermore, the sheet size and the amount of loaded sheets can be detected from the image data captured by the imaging means, which reduces the number of parts and makes the device less expensive compared to when a device for detecting the sheet size and a device for detecting the amount of loaded sheets are provided separately.

[0115] (Aspect 3) In the first or second aspect, it is detected whether the sheet stacked on the sheet stacking section such as the bottom plate 104 is the last sheet based on image data captured by an imaging unit such as the imaging device 110. According to this, as explained in the fifth embodiment, the last sheet of paper moves toward a separation position such as a separation nip together with the previous sheet. Therefore, when it becomes the last sheet, the position of the sheet stacked in the sheet stacking section is located downstream in the sheet conveyance direction compared to when it is not the last sheet. Therefore, by having the imaging unit capture an image of the entire sheet, it is possible to determine from the captured image data whether the sheet has shifted downstream in the conveyance direction. Then, if it is detected from the captured image data that the sheet has shifted downstream in the conveyance direction, it can be determined that the sheet stacked in the sheet stacking section is the last sheet. In this way, by being able to determine whether the sheet stacked in the sheet stacking section is the last sheet, when it is detected that the sheet is the last during continuous printing, it is possible to perform image formation on this last sheet and then stop the image formation operation. This prevents situations where image formation toner has to be discarded (forced cleaning) and reduces wasteful toner consumption. The user can be notified that paper is running out before the sheet runs out, which shortens device downtime compared to notifying the user after the paper runs out. In addition, from the image data captured by the imaging means, it is possible to detect whether the sheet is the last one and other detections (at least one of detecting the sheet size and detecting the amount of sheets stacked), which allows the number of parts to be reduced and the device to be made cheaper than when a device for detecting the other things mentioned above and a device for detecting whether the sheet is the last one are provided separately.

[0116] (Aspect 4) A sheet stacking device such as a paper feed cassette 15 is provided with a sheet stacking section such as a bottom plate 104 for stacking sheets such as paper P, and an imaging means such as an imaging device 110 for imaging the entire sheets stacked in the sheet stacking section, and detects whether the sheet stacked in the sheet stacking section is the last one or not based on image data captured by the imaging means. According to this, as explained in the fifth embodiment, the last sheet of paper moves toward a separation position such as a separation nip together with the previous sheet. Therefore, when it becomes the last sheet, the position of the sheet stacked in the sheet stacking section is located downstream in the sheet conveyance direction compared to when it is not the last sheet. Therefore, by having the imaging unit capture an image of the entire sheet, it is possible to determine from the captured image data whether the sheet has shifted downstream in the conveyance direction. Then, if it is detected from the captured image data that the sheet has shifted downstream in the conveyance direction, it can be determined that the sheet stacked in the sheet stacking section is the last sheet. In this way, by being able to determine whether the sheet stacked in the sheet stacking section is the last sheet, when it is detected that the sheet is the last during continuous printing, it is possible to perform image formation on this last sheet and then stop the image formation operation. This prevents situations where image formation toner has to be discarded (forced cleaning) and reduces wasteful toner consumption. The user can be notified that paper is running out before the sheet runs out, which shortens device downtime compared to notifying the user after the paper runs out.

[0117] (Aspect 5) In any of the first to fourth aspects, the presence or absence of an image on the surface on which an image is to be formed, such as the front surface of a sheet, is detected based on image data captured by an imaging unit such as the imaging device 110. This makes it possible to detect when a user mistakenly places a sheet on the sheet stacking section with the image-formed side as the front side in so-called backside printing, in which an image is formed on the side opposite to the side on which an image is formed, as described in the third embodiment. This makes it possible to prevent an image from being unintentionally formed on the side on which an image is formed, and to prevent unnecessary consumption of toner. Furthermore, from the image data captured by the imaging means, in addition to detecting whether or not an image exists on the surface on which an image is to be formed, such as the front surface of the sheet, at least one of the following can be detected: sheet size, sheet stack amount, and whether or not this is the last sheet. In this way, multiple detections can be performed based on the image data captured by the imaging means, and the number of parts can be reduced compared to when separate detection devices are used for each detection, making the device less expensive.

[0118] (Aspect 6) A sheet stacking device such as a paper feed cassette 15 is provided with a sheet stacking section such as a bottom plate 104 for stacking sheets such as paper P, and an imaging means such as an imaging device 110 for imaging the sheets stacked on the sheet stacking section, and detects whether or not there is an image of the surface on which an image is to be formed, such as the front surface of the sheet, based on image data captured by the imaging means. This makes it possible to detect when a user mistakenly places a sheet on the sheet stacking section with the image-formed side as the front side in so-called backside printing, in which an image is formed on the side opposite to the side on which an image is formed, as described in the third embodiment. This makes it possible to prevent an image from being unintentionally formed on the side on which an image is formed, and to prevent unnecessary consumption of toner.

[0119] (Aspect 7) In any of aspects 1 to 6, a regulating member (side fence 102 or end fence 103) is provided to regulate the position of sheets such as paper loaded on a sheet loading section such as a bottom plate 104, and an imaging means such as an imaging device 110 simultaneously images the regulating member and the sheets loaded on the sheet loading section, and detects the distance between the sheets and the regulating member based on image data of the regulating member and the sheets simultaneously captured. This makes it possible to determine whether or not a sheet such as paper is positioned by a regulating member, as described in the fourth embodiment. As a result, if the position of loaded paper is not properly regulated due to forgetting to use a regulating member such as a side fence or end fence, or due to insufficient alignment, the user can be prompted to operate the regulating member. This can prevent non-feeding, paper jams, paper skew, and paper wrinkles. It can also prevent image position errors, where an image is not formed at the intended position on the paper. Furthermore, from the image data captured by the imaging means, it is possible to detect at least one of the following, in addition to the distance between the sheet and the regulating member: presence or absence of an image on the surface on which an image is to be formed, such as the front surface of the sheet; detection of the sheet size; detection of the amount of stacked sheets; and detection of whether or not this is the last sheet. In this way, multiple detections can be performed based on the image data captured by the imaging means, and the number of parts can be reduced compared to when separate detection devices are used for each detection, making the device less expensive.

[0120] (Aspect 8) A sheet stacking device such as a paper feed cassette 15 includes a sheet stacking section such as a bottom plate 104 for stacking sheets such as paper P, regulating members (side fences 102 and end fences 103) for regulating the position of the sheets stacked in the sheet stacking section, and an imaging means such as an imaging device 110 for simultaneously capturing images of the regulating members and the sheets stacked in the sheet stacking section, and detects the distance between the sheets and the regulating member based on image data captured by the imaging means. This makes it possible to determine whether or not a sheet such as paper is positioned by a regulating member, as described in the fourth embodiment. As a result, if the position of loaded paper is not properly regulated due to forgetting to use a regulating member such as a side fence or end fence, or due to insufficient alignment, the user can be prompted to operate the regulating member. This can prevent non-feeding, paper jams, paper skew, and paper wrinkles. It can also prevent image position errors, where an image is not formed at the intended position on the paper.

[0121] (Aspect 9) In any of aspects 1 to 8, image data captured by an imaging means such as imaging device 110 shows that the components of the sheet stacking device (such as side fences, end fences, bottom plates, and tray housings) have reflection characteristics that allow them to be distinguished from sheets. According to this, the boundary between the sheets stacked on the sheet stacking section and the components of the sheet stacking device can be easily determined from the captured image data, and the sheets can be detected with high accuracy.

[0122] (Aspect 10) In an image forming apparatus that includes a sheet stacking device such as a paper feed cassette 15 and feeds sheets from the sheet stacking device to form images on the sheets, the sheet stacking device used is one of the sheet stacking devices of aspects 1 to 9. This makes it possible to prevent abnormal images, sheet jams, wasteful toner consumption, and the like.

[0123] (Aspect 11) In the tenth aspect, a notification means such as an operation panel 70 is provided that notifies the user of information detected based on image data captured by an imaging means such as the imaging device 110. This allows the user to be notified of information about sheets loaded in a sheet loading device such as the paper feed cassette 15 or manual feed tray 33, as described in the embodiment, and encourages the user to take the appropriate action. [Explanation of symbols]

[0124] 1: Photosensitive drum 10: Imaging unit 15: Paper cassette 16:Paper feeding means 33: Manual feed tray 33a: Side fence 34:Paper feeding means 50: Device body 70: Operation panel 80: Processing section 90: Storage section 100: Printer 101: Tray housing 101a: Front wall 102: Side fence 103: End fence 104:Bottom plate 104a: Bottom plate pivot shaft 106: Detection mark 110: Imaging device 111: Imaging unit 112:Optical Department 120: Manual feed imaging device P:Paper PW: Paper width S: Image capture range [Prior art documents] [Patent documents]

[0125] [Patent Document 1] Patent No. 4324562

Claims

1. a sheet stacking section for stacking sheets; an end fence that abuts against a rear end of the sheet stacked on the sheet stacking section to regulate a position of the sheet in a feeding direction; an imaging unit for imaging the entire sheets stacked on the sheet stacking section and the end fence; A sheet stacking device characterized in that it detects whether the sheet stacked in the sheet stacking section is the last one based on whether the difference value between the gap between the end fence and the rear end of the sheet measured based on image data captured by the imaging means when the sheet is set and the gap between the end fence and the rear end of the sheet measured based on image data captured by the imaging means after the feeding means starts feeding the sheet exceeds a threshold value.

2. 2. The sheet stacking device according to claim 1, A sheet stacking device, characterized in that the sheet size of the sheets stacked on the sheet stacking section is detected based on image data captured by the imaging means.

3. 3. The sheet stacking device according to claim 1, the imaging means simultaneously images the sheet stacked on the sheet stacking section and a detection mark for detecting the position of the sheet in the height direction, a sheet stacking device for detecting the amount of sheets stacked on the sheet stacking section based on image data obtained by simultaneously capturing images of the detection mark and the sheets stacked on the sheet stacking section;

4. 4. The sheet stacking device according to claim 1, A sheet stacking device, characterized in that the presence or absence of an image on the surface of a sheet on which an image is to be formed is detected based on image data captured by said imaging means.

5. 5. The sheet stacking device according to claim 1, a side fence that abuts against an edge of the sheet in the width direction when the sheet is loaded on the sheet loading section to regulate the position of the sheet in the width direction; the imaging means simultaneously images the side fence and the sheets stacked on the sheet stacking section, A sheet stacking device, characterized in that a distance between the side fence and the sheets stacked on the sheet stacking section is detected based on image data obtained by simultaneously capturing images of the side fence and the sheets.

6. 6. The sheet stacking device according to claim 1, A sheet stacking device, characterized in that, from the image data captured by the imaging means, components of the sheet stacking device have optical differences with respect to the sheets.

7. A sheet stacking device; In the image forming apparatus, a sheet is fed from the sheet stacking device and an image is formed on the sheet, 7. An image forming apparatus, comprising: the sheet stacking device according to claim 1;

8. 8. The image forming apparatus according to claim 7, An image forming apparatus comprising: a notification unit that notifies a user of information detected based on image data captured by the imaging unit.

Images