Image forming device

Abstract

To provide an image formation device that allows a certain sized or a free-sized sheet of paper to be detected.SOLUTION: The image formation device includes a tray, a first electrode, an electrostatic capacity detection unit and a control unit. The tray loads a sheet to be supplied to the body of the image formation device. A guide is provided on the tray and regulates the side edge of the sheet with a variable regulating width. The first electrode includes a plurality of electrodes. The electrostatic capacity detection unit detects a detection value that corresponds to the quantity of electricity stored on each electrode of the first electrode. The control unit detects the position of the guide based on the relative value of the detected value of each electrode detected by the electrostatic capacity detection unit.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] FIELD An embodiment of the present invention relates to an image forming apparatus. [Background technology]

[0002] When manually feeding a sheet into an image forming device, some devices detect the sheet size by combining contact points according to the position of the sheet guide. However, this method has the problem that it can only detect specified sizes. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2020-83593 Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention is to provide an image forming apparatus that is capable of detecting paper of a predetermined size and a free size. [Means for solving the problem]

[0005] In order to solve the above problem, the image forming apparatus of this embodiment has a tray, a first electrode, a capacitance detection unit, and a control unit. The tray holds sheets to be fed to the image forming apparatus main body. The guide is provided on the tray and regulates the side edges of the sheets, and the regulation width is variable. The first electrode has a plurality of electrodes. The capacitance detection unit detects a detection value corresponding to the amount of electricity stored in each electrode of the first electrode. The control unit calculates the detection value of each electrode detected by the capacitance detection unit. ratio of The position of the guide is detected based on the [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of an MFP according to an embodiment. [Figure 2] FIG. 2 is a block diagram showing the hardware configuration of the MFP according to the embodiment. [Figure 3] FIG. 2 is a perspective view showing a manual feed tray according to the embodiment. [Figure 4] FIG. 2 is a plan view showing the manual feed tray according to the embodiment. [Figure 5] FIG. 3 is a schematic diagram of a capacitance detection substrate 83 according to an embodiment. [Figure 6] 10 is a graph showing detected values relating to the capacitance of the first electrode according to the embodiment. [Figure 7] 10 is a table for detecting sizes on a given sheet according to an embodiment. [Figure 8] 10 is a graph showing a detected value related to the capacitance of the first electrode for detecting a predetermined size according to an embodiment. [Figure 9] 6 is a graph showing a change in capacitance of a second electrode detected by a capacitance detection unit according to an embodiment. [Figure 10] FIG. 10 is a perspective view showing an ADF according to another embodiment. [Figure 11] FIG. 10 is a perspective view showing a paper feed cassette according to another embodiment. [Figure 12] 10 is a graph showing detected values relating to the capacitance of the first electrode and the third electrode of a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, an embodiment of an image forming apparatus will be described with reference to the drawings. In the embodiment, an MFP (Multi Functional Peripheral) is used as one aspect of the image forming apparatus.

[0008] 1 is a schematic diagram showing the configuration of an MFP. As shown in FIG. 1, the MFP 1 has a conveying unit 2, a control panel 3, a scanner 4, a printer 5, an inverting unit 6, a paper feed cassette 7, and a manual feed tray 8.

[0009] 2 is a block diagram showing the hardware configuration of the MFP 1. As shown in FIG. 2, the MFP 1 further includes a control unit 9, a storage unit 10, and an electrostatic capacitance detection board 83.

[0010] The control unit 9 has a processor equipped with a CPU (Central Processing Unit) or an MPU (Micro Processing Unit) and a memory. The memory is, for example, a semiconductor 87 memory, and has a ROM (Read Only Memory) that stores various control programs and a RAM (Random Access Memory) that provides a temporary working area for the processor. The control unit 9 controls each part of the MFP 1 based on the various programs stored in the ROM.

[0011] The storage unit 10 is, for example, a hard disk drive (HDD) or a solid state drive (SSD). The storage unit 10 acquires image data acquired or generated by each component of the MFP 1, for example.

[0012] The transport unit 2 has a transport path connecting the paper feed cassette 7, manual feed tray 8, printer 5, paper discharge outlet, and reversing unit 6. The transport unit 2 transports sheets from the paper feed cassette 7 or manual feed tray 8 along the transport path. The transport unit 2 has multiple transport rollers at various points along the transport path as a transport means for transporting the sheets. The upstream side of the sheet transport direction is the paper feed cassette 7 or manual feed tray 8, and the downstream side is the paper discharge outlet.

[0013] The control panel 3 has a plurality of buttons that accept user operations. The control panel 3 outputs a signal corresponding to the operation performed by the user to the control unit 9 of the MFP 1. The control panel 3 is configured as a touch panel integrated with a display. The display displays information related to the MFP 1. The display is an image display device such as a liquid crystal display or an organic EL (Electro Luminescence) display.

[0014] The scanner 4 reads an image of a document. The scanner 4 includes, for example, an ADF (Auto Document Feeder) 41 and a DSDF (Dual Scan Document Feeder). For example, the ADF 41 continuously transports multiple sheets set in the ADF 41 so that they slide along the glass surface of the scanner 4, and the scanner 4 reads the images on the transported sheets. Information about the read image may be transmitted to an external device such as a PC (Personal Computer) via a network. Information about the read image may be stored in the storage unit 10 and printed as an image on a sheet by the printer 5.

[0015] The printer 5 forms an image on a sheet conveyed from the paper feed cassette 7 or the manual feed tray 8 based on image information transmitted from an external device such as the scanner 4 or a PC. The sheet on which the image has been formed is conveyed to the paper discharge port and discharged. The printer 5 uses, for example, toner as a developing material.

[0016] The inverting unit 6 conveys the sheet upstream of the printer 5 so that the sheet conveyed from the printer 5 is inverted. The inverting unit 6 is disposed downstream of the printer 5 on the conveyance path. The inverting unit 6 operates, for example, when performing double-sided printing, which forms images on both sides of the sheet.

[0017] The paper feed cassette 7 stores sheets on which images are formed. The MFP 1 may have multiple paper feed cassettes 7.

[0018] FIG. 3 shows a perspective view of the manual feed tray 8 of the embodiment. FIG. 4 shows a plan view of the manual feed tray 8 of the embodiment. On the surface of the manual feed tray 8 on which sheets are stacked, the direction parallel to the sheet transport direction is defined as the length direction. On the surface of the manual feed tray 8 on which sheets are stacked, the direction perpendicular to the sheet transport direction is defined as the width direction. The direction perpendicular to both the length direction and width direction of the manual feed tray 8 is defined as the up-down direction. FIG. 4 shows sheets S stacked on the manual feed tray 8 as an example.

[0019] Sheets on which images are to be formed are stacked on the manual feed tray 8. The manual feed tray 8 draws the stacked sheets into the MFP 1 by a paper feed roller 21. The manual feed tray 8 has a first guide 81, a second guide 82, a capacitance detection board 83, and a conductor 87.

[0020] The first guide 81 and the second guide 82 are a pair of regulating members provided on the surface of the manual feed tray 8. The first guide 81 has a bottom surface 811 that faces the surface of the manual feed tray 8 and is a flat surface extending in the lengthwise and widthwise directions, and a regulating surface 812 that is a flat surface extending vertically upward from the bottom surface 811. The second guide 82 has a bottom surface 821 that faces the surface of the manual feed tray 8 and is a flat surface extending in the lengthwise and widthwise directions, and a regulating surface 822 that is a flat surface extending vertically upward from the bottom surface 821. The first guide 81 and the second guide 82 are provided on the surface of the manual feed tray 8 with a gap therebetween in the width direction so that their regulating surfaces face each other. The regulating surface 812 of the first guide 81 and the regulating surface 822 of the second guide 82 abut against the side edges of sheets stacked on the surface of the manual feed tray 8 to regulating the sheets in the width direction. The regulating width, which is the widthwise distance between the regulating surfaces of the first guide 81 and the second guide 82, is variable. The first guide 81 and the second guide 82 have, for example, protrusions 813 extending perpendicularly downward from the bottom surface 811 and the bottom surface 821, respectively, and are configured to engage with grooves 814 provided along the width direction on the surface of the manual feed tray 8. The first guide 81 and the second guide 82 move in the width direction along the grooves 814 of the manual feed tray 8. The first guide 81 and the second guide 82 move the same distance in opposite directions using a rack and pinion structure 815, with a center line on the surface of the manual feed tray 8 that is perpendicular to the width direction as the reference.

[0021] The conductor 87 is provided to face the capacitance detection board 83. In the embodiment, the conductor 87 is provided on the bottom surface 811 of the first guide 81, that is, at a position facing the manual feed tray 8. The conductor 87 is, for example, a rectangular plate. The conductor 87 is, for example, a metal plate. As the first guide 81 moves, the conductor 87 moves in the width direction while facing the capacitance detection board 83. That is, in the embodiment, the position of the conductor 87 in the width direction on the capacitance detection board 83 corresponds to the position of the first guide 81 in the width direction on the capacitance detection board 83. The installation position of the conductor 87 is not limited to the bottom surface 811 of the first guide 81, as long as it is a position facing the capacitance detection board 83.

[0022] FIG. 5 shows a schematic diagram of a capacitance detection substrate 83 according to an embodiment. The capacitance detection board 83 has a first electrode 84, a second electrode 85, and a capacitance detection unit 86. The capacitance detection board 83 is provided on the surface of the manual feed tray 8 so as to face the conductor 87. The capacitance detection board 83 extends in the width direction, which is the direction of movement of the conductor 87. In this embodiment, the capacitance detection board 83 is provided so that the electrode 845 and the second electrode 85 face a center line on the surface of the manual feed tray 8 that is perpendicular to the width direction.

[0023] The first electrodes 84 are electrodes for detecting the position of the conductor 87 on the capacitance detection substrate 83. The first electrodes 84 include an electrode 841, an electrode 842, an electrode 843, an electrode 844, and an electrode 845. The electrodes 841, 842, 843, 844, and 845 are arranged along the width direction. That is, the electrodes of the first electrodes 84 (electrodes 841, 842, 843, 844, and 845) are arranged in order along the direction of movement of the conductor 87. The electrodes of the first electrodes 84 are arranged such that, at any position along the width direction of each electrode, another electrode of the first electrodes 84 faces the conductor 87 in the up-down direction. The number of electrodes of the first electrodes 84 is not limited as long as it is two or more.

[0024] At any position in the width direction of electrode 841, conductor 87 vertically faces electrode 841 as well as electrode 842 and electrode 843. At any position in the width direction of electrode 842, conductor 87 vertically faces electrode 842 as well as electrode 841, electrode 843, and electrode 844. At any position in the width direction of electrode 843, conductor 87 vertically faces electrode 841, electrode 842, electrode 844, and electrode 845 as well as electrode 843. At any position in the width direction of electrode 844, conductor 87 vertically faces electrode 842, electrode 843, and electrode 845 as well as electrode 844. At any position in the width direction of electrode 845, conductor 87 vertically faces electrode 843 and electrode 844 as well as electrode 845.

[0025] The arrangement of the first electrodes 84 will be described in detail. For convenience of the following description, the widthwise positions of the first electrodes 84 are divided into points a to n, which are defined as points a to n. The widthwise length of electrode 841 is from point a to point d. The widthwise length of electrode 842 is from point a to point h. The widthwise length of electrode 843 is from point c to point l. The widthwise length of electrode 844 is from point g to point n. The widthwise length of electrode 845 is from point k to point n.

[0026] For convenience of explanation, the length in the longitudinal direction of electrode 841 is defined as a first length. The length in the longitudinal direction of electrode 842 is defined as a second length. The length in the longitudinal direction of electrode 843 is defined as a third length. The length in the longitudinal direction of electrode 844 is defined as a fourth length. The length in the longitudinal direction of electrode 845 is defined as a fifth length.

[0027] 5, when the conductor 87 is located between point a and point b where it faces the electrodes 841 and 842, the conductor 87 faces the electrode 841 at a first length on the upstream side in the sheet conveying direction and faces the electrode 842 at a second length on the downstream side in the sheet conveying direction. As the conductor 87 transitions from point a to point b, the first length shortens and the second length lengthens. When the conductor 87 is located between point b and point c where it faces the electrodes 841 and 842, the conductor 87 faces the electrode 841 at a first length on the upstream side in the sheet conveying direction and faces the electrode 842 at a second length on the downstream side in the sheet conveying direction. As the conductor 87 transitions from point b to point c, the first length shortens and the second length remains constant. When the conductor 87 is located between points c and d, where it faces the electrodes 841, 842, and 843, the conductor 87 faces the electrode 841 at a first length on the upstream side in the sheet transport direction, faces the electrode 842 at a second length on the downstream side in the sheet transport direction, and faces the electrode 843 at a third length further downstream in the sheet transport direction than the electrode 842. As the conductor 87 transitions from point c to point d, the first length shortens, the second length remains constant, and the third length lengthens. When the conductor 87 is located between points d and e, where it faces the electrodes 842 and 843, the conductor 87 faces the electrode 842 at a second length on the upstream side in the sheet transport direction, and faces the electrode 843 at a third length on the downstream side in the sheet transport direction. As the conductor 87 transitions from point d to point e, the conductor 87 faces the electrode 842 at a second length on the upstream side in the sheet transport direction, and faces the electrode 843 at a third length on the downstream side in the sheet transport direction. When the conductor 87 is located between points e and f, where it faces the electrodes 842 and 843, the conductor 87 faces the electrode 842 at a second length on the upstream side in the sheet transport direction and faces the electrode 843 at a third length on the downstream side in the sheet transport direction. As the conductor 87 transitions from point e to point f, the second length shortens and the third length lengthens. When the conductor 87 is located between points f and g, where it faces the electrodes 842 and 843, the conductor 87 faces the electrode 842 at a second length on the upstream side in the sheet transport direction and faces the electrode 843 at a third length on the downstream side in the sheet transport direction. As the conductor 87 transitions from point f to point g, the second length shortens and the third length remains constant.When the conductor 87 is located between points g and h, where it faces the electrodes 842, 843, and 844, the conductor 87 faces the electrode 842 at a second length on the upstream side in the sheet transport direction, faces the electrode 843 at a third length on the downstream side in the sheet transport direction, and faces the electrode 844 at a fourth length further downstream than the electrode 843 in the sheet transport direction. As the conductor 87 transitions from point g to point h, the second length shortens, the third length remains constant, and the fourth length length increases. When the conductor 87 is located between points h and i, where it faces the electrodes 843 and 844, the conductor 87 faces the electrode 843 at a third length on the upstream side in the sheet transport direction, and faces the electrode 844 at a fourth length on the downstream side in the sheet transport direction. As the conductor 87 transitions from point h to point i, the third length remains constant, and the fourth length increases. When the conductor 87 is at point i to point j facing the electrode 843 and the electrode 844, the conductor 87 faces the electrode 843 at a third length on the upstream side in the sheet transport direction and faces the electrode 844 at a fourth length on the downstream side in the sheet transport direction. As the conductor 87 transitions from point i to point j, the third length shortens and the fourth length lengthens. When the conductor 87 is at point j to point k facing the electrode 843 and the electrode 844, the conductor 87 faces the electrode 843 at a third length on the upstream side in the sheet transport direction and faces the electrode 844 at a fourth length on the downstream side in the sheet transport direction. As the conductor 87 transitions from point j to point k, the third length shortens and the fourth length remains constant. When the conductor 87 is located between points k and l where it faces electrodes 843, 844, and 845, the conductor 87 faces electrode 843 at a third length on the upstream side in the sheet transport direction, faces electrode 844 at a fourth length on the downstream side in the sheet transport direction, and faces electrode 845 at a fifth length further downstream than electrode 844 in the sheet transport direction. As the conductor 87 transitions from point k to point l, the third length shortens, the fourth length remains constant, and the fifth length lengthens. When the conductor 87 is located between points l and m where it faces electrodes 844 and 845, the conductor 87 faces electrode 844 at a fourth length on the upstream side in the sheet transport direction, and faces electrode 845 at a fifth length on the downstream side in the sheet transport direction. As the conductor 87 transitions from point l to point m, the conductor 87 faces electrode 844 at a fourth length on the upstream side in the sheet transport direction, and faces electrode 845 at a fifth length on the downstream side in the sheet transport direction.When the conductor 87 is located between point m and point n, where it faces the electrode 844 and the electrode 845, the conductor 87 faces the electrode 844 at a fourth length on the upstream side in the sheet conveying direction, and faces the electrode 845 at a fifth length on the downstream side in the sheet conveying direction. As the conductor 87 moves from point m to point n, the fourth length becomes shorter and the fifth length becomes longer.

[0028] Of the areas of first electrode 84 facing conductor 87, the area facing conductor 87 of at least one electrode increases or decreases as conductor 87 moves. For example, from point b to point e, the area of electrode 842 facing conductor 87 is constant, but the area of at least one of electrodes 841 and 843 facing conductor 87 changes as conductor 87 moves.

[0029] The second electrode 85 is an electrode for detecting whether or not a sheet is placed on the manual feed tray 8. In the width direction, the second electrode 85 is provided so as to correspond to a position where the smallest size sheet is placed among the sheets that can be placed on the manual feed tray 8. In this embodiment, the second electrode 85 is provided near the electrode 844. The second electrode 85 is provided at a position that does not face the conductor 87.

[0030] The capacitance detection unit 86 detects a detection value related to the capacitance of the first electrode 84 or the second electrode 85. The capacitance detection unit 86 is electrically connected to the first electrode 84 and the second electrode 85. The capacitance of each electrode of the first electrode 84 increases when the electrode faces the conductor 87. The amount of increase in the capacitance of each electrode of the first electrode 84 changes depending on the area of the electrode that faces the conductor 87. The capacitance detection unit 86 detects, as a detection value, the difference between the capacitance of each electrode of the first electrode 84 when it is not facing the conductor 87 and the capacitance of each electrode of the first electrode 84 that has increased due to facing the conductor 87.

[0031] FIG. 6 shows a graph of detection values related to the capacitance of the first electrode 84 detected by the capacitance detection unit 86. Points a to l in FIG. 6 indicate points a to l on the first electrode 84. The vertical axis of the graph in FIG. 6 indicates the detection value related to the capacitance of each electrode of the first electrode 84. The horizontal axis of the graph in FIG. 6 indicates the position of the conductor 87 on the first electrode 84. In other words, the horizontal axis of the graph in FIG. 6 corresponds to the position of the first guide 81 in the width direction on the capacitance detection board 83.

[0032] The detected value of electrode 841 is maximum when conductor 87 is at point a and minimum when conductor 87 is at point d to point n. The detected value of electrode 842 is maximum when conductor 87 is at point b to point e and minimum when conductor 87 is at point h to point n. The detected value of electrode 843 is maximum when conductor 87 is at point f to point i and minimum when conductor 87 is at point a to point c or point l to point n. The detected value of electrode 844 is maximum when conductor 87 is at point j to point m and minimum when conductor 87 is at point a to point g. The detected value of electrode 845 is maximum when conductor 87 is at point n and minimum when conductor 87 is at point a to point k.

[0033] The control unit 9 detects the position of the conductor 87 in the width direction on the first electrode 84 based on the relative values of the detection values of each electrode. For example, when the conductor 87 is at point a, the control unit 9 compares the detection values of electrodes 841 to 845 and detects the position of the conductor 87 based on the relative values based on each detection value. When comparing the detection values of each electrode, the control unit 9 may compare the detection values of all the electrodes of the first electrode 84, or may compare the detection values of at least two or more electrodes.

[0034] The control unit 9 detects the position of the conductor 87 based on the detection values of each electrode of the first electrode 84. For example, when the ratio of the detection values of the electrodes 841 and 842 is 20:1, the control unit 9 detects that the conductor 87 is located at a position where the length in the width direction between the restriction surfaces 812 and 822 is 297 mm. For example, when the ratio of the detection values of the electrodes 842, 843, and 844 is 4:10:1, the control unit 9 detects that the conductor 87 is located at a position where the length in the width direction between the restriction surfaces 812 and 822 is 182 mm. The ratio of the detection values of the first electrodes 84 used to detect the position of the conductor 87 described above is an example, and is not limited to these numerical values.

[0035] The capacitance of each electrode of first electrode 84 may change depending on the outside air temperature. Therefore, it is preferable that control unit 9 detects the position of each electrode of first electrode 84 based on the relative value of the detection value, rather than the absolute value of the detection value.

[0036] This allows the control unit 9 to detect the position of the first guide 81 on the manual feed tray 8, that is, the length of the sheet in the width direction to be used.

[0037] The control unit 9 can detect the size of a predetermined sheet. A predetermined sheet is a sheet having dimensions that conform to an international standard, such as ISO. In this embodiment, JIS standard sizes are used. For example, the following sheet dimensions will be used in the following explanation: A3 size (297 x 420), B4 size (257 x 364), A4 size (210 x 297), B5 size (182 x 257), A5 size (148 x 210), A6 size (105 x 148), and business card size (55 x 91). Note that these sheet sizes are expressed as (width direction x length direction).

[0038] FIG. 7 shows a table relating to detection of a predetermined sheet size. FIG. 8 shows a graph of detection values relating to the capacitance of the first electrodes 84 relating to detection of the predetermined sheet size. The control unit 9 detects the position of the conductor 87 in the width direction on the first electrodes 84 based on the combination of the first electrodes 84 for which a detection value equal to or greater than the first threshold is detected. In FIG. 7, the numerical values 1 indicate that the detection value of the electrode is equal to or greater than the first threshold, and 0 indicate that the detection value of the electrode is less than the first threshold. The first threshold may be a different value for each of the first electrodes 84. In FIG. 8, for ease of explanation, the positions of the first electrodes 84 in the width direction are divided into points t to z, and are defined as points t to z.

[0039] In FIG. 8 , for example, when the conductor 87 is at point t, only the detection value of electrode 841 is equal to or greater than the first threshold, and the sheet size is detected as A3 size. When the conductor 87 is at point u, the detection values of electrodes 841 and 842 are equal to or greater than the first threshold, and the sheet size is detected as B4 size. When the conductor 87 is at point v, the detection values of electrodes 842 and 843 are equal to or greater than the first threshold, and the sheet size is detected as A4 size. When the conductor 87 is at point w, only the detection value of electrode 843 is equal to or greater than the first threshold, and the sheet size is detected as B5 size. When the conductor 87 is at point x, the detection values of electrodes 843 and 844 are equal to or greater than the first threshold, and the sheet size is detected as A5 size. When the conductor 87 is at point y, the detection values of electrodes 844 and 845 are equal to or greater than the first threshold, and the sheet size is detected as A6 size. When the conductor 87 is at point z, only the detection value of electrode 845 is equal to or greater than the first threshold, and the sheet size is detected as business card size.

[0040] This allows the control unit 9 to detect the specified position of the first guide 81 on the manual feed tray 8, that is, the length in the width direction of the default sheet to be used.

[0041] As described above, by detecting the position of the first guide 81 on the manual feed tray 8, an image can be formed on the sheet fed from the manual feed tray 8 based on the position of the first guide 81.

[0042] In the embodiment, the width of the sheet is detected, but by arranging the capacitance detection board 83 and the conductor 87 so that the conductor 87 moves in the length direction, the length of the sheet in the length direction can be detected.

[0043] FIG. 9 shows the change in the capacitance of the second electrode 85 detected by the capacitance detection unit 86. The vertical axis of the graph in FIG. 9 represents the detected value related to the capacitance of the second electrode 85. The horizontal axis of the graph in FIG. 9 represents the width direction of the sheet placed on the second electrode 85. The graph in FIG. 9 also represents the detected value of the capacitance between the second electrode 85 and a sheet placed opposite the second electrode 85. The sheet is placed with its center line aligned with the center line of the manual feed tray. The graph in FIG. 9 represents a case where the length direction of the sheet placed on the second electrode 85 is at least longer than the length direction of the second electrode 85. The detected value of the second electrode 85 exceeds the second threshold when at least the smallest size sheet placed on the manual feed tray 8 is placed. In this embodiment, the detected value of the second electrode 85 exceeds the second threshold when at least a business card-sized sheet is placed on the manual feed tray 8.

[0044] The control unit 9 detects that a sheet has been placed on the manual feed tray 8 by detecting that the detection value of the second electrode 85 by the capacitance detection unit 86 has become equal to or greater than the second threshold. Alternatively, the control unit 9 may detect that a sheet has been placed on the manual feed tray 8 by detecting that the detection values of the first electrode 84 and the second electrode 85 by the capacitance detection unit 86 have become equal to or greater than the second threshold. The second threshold related to the detection value of the first electrode 84 is a value smaller than the first threshold. The detection value of the first electrode 84 exceeds the second threshold when at least a sheet of the smallest size among sheets that can be placed on the manual feed tray 8 is placed.

[0045] Detection of a sheet placed on the manual feed tray 8 may be achieved by the first electrode 84. For example, the control unit 9 detects that a sheet has been placed on the manual feed tray 8 by detecting that the detection value of electrode 845 by the capacitance detection unit 86 has reached or exceeded a second threshold. The first electrode 84 that detects the sheet is preferably an electrode that does not vertically face the conductor 87. This is because there is a high possibility that the detection value of the capacitance associated with the electrode and the conductor will reach or exceed the second threshold, resulting in the detection of a sheet being placed even when no sheet is present. Specifically, when the detection value of electrode 845 in FIG. 5 is used to detect a placed sheet, the conductor 87 can detect sheets of sizes at points a to k that do not face the electrode 845.

[0046] This allows the MFP 1 of this embodiment to detect that a sheet has been placed on the manual feed tray 8.

[0047] The control unit 9 can detect the length of the sheet based on the change in the capacitance of the second electrode 85 detected by the capacitance detection unit 86. The control unit 9 has a counter 91 for counting time. For example, when a sheet is drawn into the MFP 1 for printing or the like, the control unit 9 counts the time from when the sheet starts to be conveyed until the capacitance of the second electrode 85 becomes the capacitance in a state where the second electrode 85 is not facing the sheet. The control unit 9 can detect the length of the sheet placed on the manual feed tray 8 based on the length from the second electrode 85 to the feed entrance of the MFP 1 where the sheet is drawn, the sheet conveyance speed, and the time counted by the counter 91. The length from the second electrode 85 to the feed entrance of the MFP 1 where the sheet is drawn and the sheet conveyance speed are stored in advance in the storage unit 10.

[0048] This allows the MFP 1 of this embodiment to detect the lengthwise size of the pulled-in sheet.

[0049] 10 is a perspective view showing ADF 41. In another embodiment, for example, ADF 41 provided in scanner 4 has first guide 42, second guide 43, capacitance detection board 44, and conductor 45. The first guide 42, second guide 43, capacitance detection board 44, and conductor 45 are the same as the first guide 81, second guide 82, capacitance detection board 83, and conductor 87 in the embodiment of manual tray 8 described above, and therefore their description will be omitted. The control unit that detects the position of conductor 45 and the placement of a sheet may be provided in ADF 41, or may be provided in the main body of MFP 1 to which ADF 41 is connected.

[0050] Although the embodiment has been described taking the manual feed tray 8 and ADF 41 as examples, the present invention may also be provided in the paper feed cassette 7 as shown in FIG.

[0051] 11 is a perspective view showing a sheet feed cassette 7. In another embodiment, for example, the sheet feed cassette 7 has a first guide 71, a second guide 72, a capacitance detection board 73, and a conductor 74. The first guide 71, the second guide 72, the capacitance detection board 73, and the conductor 74 are the same as the first guide 81, the second guide 82, the capacitance detection board 83, and the conductor 87 in the embodiment of the manual feed tray 8 described above, and therefore their description will be omitted. A control unit that detects the position of the conductor 74 and that a sheet has been placed is provided in, for example, the MFP 1 main body.

[0052] FIG. 12 is a graph of detected values relating to the capacitance of the first electrode 84 and the third electrode 88 in a modified example. In this modified example, the control unit 9 can detect that the position of the first guide 81 on the manual feed tray 8, i.e., the widthwise length of the sheet being used, is smaller than the minimum size that can be handled by the MFP 1. The MFP 1 in this modified example does not support paper sizes smaller than A6 size (105 × 148). The first electrode 84 in FIG. 10 is the same as that described in the embodiment. The third electrode 88 is provided on a capacitance detection board 83. The third electrode 88 is electrically connected to the capacitance detection unit 86. The conductor 87 faces the third electrode 83 at a position in the widthwise direction. The third electrode 88 is located closer to the center line of the manual feed tray 8 than the position of the widthwise length of the minimum size sheet that can be handled by the MFP 1, among positions on the manual feed tray 8 detected from the detection value of the first electrode 84, and is located within a region where the conductor 87 can move. In the modified example, the position is closer to the center line of the manual feed tray 8 than the position (point y) at which the A6 size, which is the size of sheets that the MFP 1 can handle, and is located within an area where the conductor 87 can move. The detection value of the third electrode 88 exceeds the third threshold value when the third electrode 88 and the conductor 87 face each other.

[0053] The control unit 9 detects that the position of the first guide 81 is less than the width-wise length of the smallest size sheet that the MFP 1 can handle by detecting that the detection value of the third electrode 88 by the capacitance detection unit 86 has become equal to or greater than the third threshold value.

[0054] When the control unit 9 detects that the threshold value of the third electrode 88 has become equal to or greater than the third threshold value, the control unit 9 may not accept an input to execute printing by feeding a sheet from the manual feed tray 8. Furthermore, when the control unit 9 detects that the threshold value of the third electrode 88 of the capacitance detection board 44 provided in the ADF 41 has become equal to or greater than the third threshold value, the control unit 9 may not accept an input to execute scanning or copying that requires sheet transport by the ADF 41. Furthermore, when the control unit 9 detects that the threshold value of the third electrode 88 of the capacitance detection board 73 provided in the paper feed cassette 7 has become equal to or greater than the third threshold value, the control unit 9 may not accept an input to execute printing by feeding a sheet from the paper feed cassette 7 for which a detection value equal to or greater than the third threshold value has been detected.

[0055] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0056] 9. Control section 8 Manual feed tray 81···First Guide 82···Second Guide 84...first electrode 841, 842, 843, 844, 845... Electrode 85...Second electrode 86 Capacitance detection unit 87 Conductor

Claims

1. A tray for loading sheets; a guide provided on the tray for regulating a side edge of the sheet and having a variable regulation width; a first electrode having a plurality of electrodes; a capacitance detection unit that detects a detection value corresponding to an amount of electricity stored in each of the first electrodes; a control unit that detects the position of the guide based on a ratio of the detection values of the electrodes detected by the capacitance detection unit; an image forming unit that forms an image on the sheet supplied from the tray based on the position of the guide detected by the control unit; An image forming apparatus having the same.

2. a conductor provided on the guide and moving on the tray together with the movement of the guide due to the change in the restriction width; and the first electrode has a plurality of electrodes at a position facing the conductor in a moving direction of the conductor; The electrodes are arranged at positions where other electrodes face the conductor at any position in the moving direction of the conductor. The image forming apparatus according to claim 1 .

3. The control unit detects the position of the guide based on a combination of the electrodes in which the detection value equal to or greater than a first threshold value is detected.

3. The image forming apparatus according to claim 1.

4. A conductor provided on the guide and moving on the tray together with the movement of the guide due to the change in the regulation width; and The control unit detects the sheet when the detection value of at least one of the first electrodes that does not face the conductor is equal to or greater than a second threshold value. The image forming apparatus according to claim 1 .

5. A conductor provided on the guide and moving on the tray together with the movement of the guide due to the change in the regulation width; a second electrode provided at a position not facing the conductor but facing the sheets stacked on the tray; the capacitance detection unit detects the detection value according to the amount of electricity stored in the second electrode; The control unit detects the sheet when the detection values of at least one of the first electrodes that does not face the conductor and the second electrode are equal to or greater than a second threshold value. The image forming apparatus according to claim 1 .

Images