JP2008133083A - Paper feeder and image forming device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a paper feeder capable of detecting the size of a sheet material by loop coils juxtaposed in a predetermined range and a resonance circuit existing in a position opposed to these loop coils, and an image forming device using this paper feeder. <P>SOLUTION: This paper feeder is characterized by having a first position indicating means 004 arranged in a width regulating member 002, a second position indicating means 005 arranged in a length regulating means 003, a sensor board 006 of arranging a plurality of transmission-reception switchable loop coils on a passage for respectively moving the respective position indicating means, a position detecting means 007 detecting an arrangement position of the loop coils of the respective position indicating means as a present position from the characteristic distribution of its received signal, by receiving the signal received to the respective indicating means by the loop coils switched to a receiving state, by sending the signal from the loop coils of a transmission state to the respective position indicating means, and a size determining means 008 determining the size of the sheet material 009 based on the present position of the respective position indicating means received from the position detecting means 007. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a sheet feeding device for feeding a sheet material (for example, paper) to a subsequent stage and an image forming apparatus including the sheet feeding device. More specifically, the present invention relates to a sheet feeding device that detects the size of a sheet material and an image forming apparatus including the sheet feeding device.

  In an image forming apparatus such as a copying machine, a facsimile machine, and a printer, the size of a sheet material that is a recording medium such as transfer paper can be selected according to the purpose and size of use of a user. In such a case, a dedicated sheet feeding tray may be prepared for each size. However, in order to reduce the burden on the user, a sheet feeding tray that can set various sheet materials is used. Then, the sheet material is in contact with the sheet end surface orthogonal to the sheet feeding direction of the sheet material stacked on the tray, and a width regulating member that aligns the position of the sheet material in the direction orthogonal to the sheet feeding direction of the sheet material; A length regulating member that abuts the end surface of the sheet material in the sheet feeding direction and aligns the sheet position in the sheet feeding direction is provided, and the width regulating member and the length regulating member are slid to form the sheet material. The stacking position of the sheet material is positioned by the contact. Here, the sheet material refers to transfer paper, a transfer material containing OHP, and an intersheet that is paper inserted between the transfer paper.

  In addition, in the POD (Print On Demand) market, which has been increasing in recent years, the use of non-standard paper such as paper cut by a user has increased. In general, the image forming apparatus is configured not to pass the sheet when the size cannot be determined. Therefore, in the case of such an irregular sheet, the user needs to manually input the length and width of the sheet material. there were.

  In such a sheet feeding tray using various sheet materials, it is necessary to detect which size of sheet material is currently set in the tray. Therefore, it is necessary to detect the size of the sheet material in such a tray. Therefore, conventionally, a rotating member having a stepped groove formed in the bottom of the paper feed tray is rotatably provided, and the size of the sheet material is detected by rotating the rotating member by moving the end fence of the tray ( For example, refer to Patent Document 1), and when the cursor for width adjustment is moved according to the size according to the size of the sheet material using the volume resistor, the volume resistor is linked with the movement of the cursor. A technique for detecting the size of the sheet material by changing the resistance value by moving the sliding portion and reading the voltage value generated by passing a current through the volume resistor (for example, see Patent Document 2). In place of the volume resistor, a substrate on which a plurality of conductors are arranged in a predetermined pattern is used, and an electrode is provided on the cursor so as to contact the substrate. Depending on the position of the cursor, the electrode is brought into contact with or not in contact with the conductor, and a switch is turned on and off to turn on the signal line connected to each conductor according to the position of the cursor. Alternatively, a signal indicating OFF is generated, and a technique for detecting the size by a combination of ON / OFF of signals from the plurality of signal lines (see, for example, Patent Document 3), and the size in the sheet feeding direction by a volume resistor. Techniques have been proposed for detecting and detecting the size in the direction perpendicular to the sheet feeding direction by an optical sensor, and the size of the sheet material has been detected by these techniques.

  As a position detection technique, a loop coil having a plurality of turns is arranged in the position detection direction, a loop coil predicted to be closest to the resonance circuit for indicating the position is selected, and this loop coil is selected. When sending the transmission command and receiving the electromagnetic wave sent back from the resonance circuit by the electromagnetic interaction caused by this transmission signal, the signal characteristic distribution necessary for position detection is obtained by scanning all the loop coils, and this distribution (See, for example, Patent Document 4) for determining the position of the resonance circuit from the above. With this technique, the S / N in the position detection circuit can be greatly improved, the detection accuracy can be greatly improved, and a resolution of 0.01 mm can be obtained by arranging the loop coils.

JP 2002-187626 A Japanese Patent Laid-Open No. 10-1227 JP-A-8-295419 JP-A-8-161100

  However, in the configuration of Patent Document 1, since the paper is detected only in the paper feeding direction by the end fence, the detection size is limited. In addition, when detecting the size of the non-standard paper, it is necessary to detect with an accuracy of 1 mm in both the paper feeding direction and the direction orthogonal to the paper feeding direction. In the configuration of Patent Document 2 using volume resistance, it is difficult to ensure sufficient accuracy of size detection. Further, in the configuration of Patent Document 3, when the number of types of sizes to be detected increases, it is necessary to increase the number of signals and increase the on / off combination pattern. Therefore, the number of signal lines for inputting signal on / off to the CPU is increased. The number increases. For this reason, it is necessary to use an expensive CPU having a large number of signal input ports, resulting in high costs. In addition, there is a problem that the structure of the optical sensor becomes very complicated and the cost becomes high.

  Further, in the configuration in which the loop coil is simply arranged in the entire area and the two-dimensional area of the sheet material is detected, it is necessary to scan the entire plane even though the position indicator operates only in a specific range. There is a problem that an excessive load is generated and the cost is increased.

  The present invention has been made in view of such circumstances, and a sheet feeding device capable of detecting the size of a sheet material by a loop coil arranged in a predetermined range and a resonance circuit at a position facing the loop coil, and An object of the present invention is to provide an image forming apparatus used.

  In order to achieve the above object, the invention according to claim 1 is configured so that the loading means for loading the sheet material and the both ends in the width direction perpendicular to the sheet feeding direction of the sheet material loaded above are sandwiched. Two movable width restricting members installed, a movable length restricting member installed so as to press the rear end of the sheet material stacked in the paper feeding direction, and the width restricting member. The first resonance circuit, the second resonance circuit provided on the length restricting member, and the first resonance circuit and the second resonance circuit partially overlap each other on a path along which the first resonance circuit and the second resonance circuit move. A plurality of loop coils that can be switched between transmission and reception, and the first resonance circuit and the second resonance circuit, a signal is transmitted by electromagnetic coupling from the loop coil in a transmission state close to each of the first resonance circuit and the second resonance circuit, 1 resonant circuit and front The signal received by the second resonance circuit is received by the loop coil switched to the reception state, and the position on the loop coil arrangement of the first resonance circuit and the second resonance circuit is determined from the characteristic distribution of the received signal. The position detection means for detecting the current position as the current position, and the size of the sheet material is obtained based on the current position of the first resonance circuit and the current position of the second resonance circuit received from the position detection means. And a size determining means.

  According to a second aspect of the present invention, there is provided the sheet feeding device according to the first aspect, wherein the size determination unit includes a first resonance circuit and a first resonance circuit in a case where a sheet material having a known predetermined size is loaded. Two resonance circuits, storage means for storing a reference position that is a position on the array of the respective loop coils, and the size based on the reference position and the current position of each of the first resonance circuit and the second resonance circuit. It is characterized by seeking.

  A third aspect of the present invention is the paper feeding device according to the first or second aspect, wherein the sensor substrate sequentially scans the loop coils arranged in the width direction and the arrangement direction in series. And receiving.

  The image forming apparatus according to claim 4, wherein the stacking means for stacking the sheet material and the two movements installed so as to sandwich both ends in the width direction orthogonal to the sheet feeding direction of the previously stacked sheet material A possible width regulating member, a movable length regulating member installed so as to press the rear end in the sheet feeding direction of the stacked sheet material, and a first resonance circuit provided in the width regulating member, A plurality of transmission / reception switching is possible by partially overlapping a second resonance circuit provided on the length regulating member and a path along which each of the first resonance circuit and the second resonance circuit moves with a certain interval. A signal is transmitted by electromagnetic coupling from the loop coil in a transmission state close to each of the sensor substrate on which a simple loop coil is arranged, the first resonance circuit, and the second resonance circuit, and the first resonance circuit and the first resonance circuit. 2 resonant circuit The received signal is received by the loop coil switched to the reception state, and the position on the array of the loop coils of the first resonance circuit and the second resonance circuit is detected as the current position from the characteristic distribution of the received signal. Position detecting means, a size determining means for obtaining a size of the sheet material based on the current position of the first resonance circuit and the current position of the second resonance circuit received from the position detection means, and the sheet material The image forming apparatus includes a sheet feeding unit that feeds paper and an image forming unit that forms an image on the fed sheet material.

  According to the sheet feeding device according to claim 1 and the image forming device according to claim 4, the position of each regulating member can be detected by the characteristic distribution of signals obtained by the loop coil and the resonance circuit. The size can be determined. As a result, it is possible to detect the size of the sheet material with high accuracy.

  According to the paper feeding device of the second aspect, since the current position is obtained from the reference position, the position of the restricting member can be accurately detected. As a result, it is possible to detect the size of the sheet material with higher accuracy.

  According to the paper feeding device of the third aspect, since the loop coils are arranged in series, the configuration of the paper feeding device is simplified. Thereby, it becomes possible to hold down manufacturing cost.

[First Embodiment]
Hereinafter, a sheet feeding device according to a first embodiment of the present invention will be described. FIG. 1 is a block diagram showing functions of a sheet feeding device according to the present invention. The position detection unit 007 and the size determination unit 008 in FIG. 1 are composed of a CPU and a program that defines its operation. Further, each of the first position instruction means 004 and the second position instruction means 005 has a resonance circuit. Further, solid line arrows in FIG. 1 represent signal exchange, and dotted line arrows represent physical action relationships. Further, the sheet material 009 is loaded on the loading means 001, the first position indicating means 004 is provided on the width restricting member, and the second position indicating means 005 is provided on the length restricting member. FIG. 2A is a schematic plan view of a state in which the sheet material 009 is placed on the sheet feeding device according to the present invention. However, in FIG. 2A, the first position indicating means 004 and the second position indicating means 005 are shown so as to be visible, but actually, they are provided under the width restricting member 002 and the length restricting member 003, respectively. It is something that is not visible and small. FIG. 2B is a diagram for explaining the sensor substrate 006, the first position instruction unit 004, and the second position instruction unit 005 in the state of FIG. Here, in FIG. 1, FIG. 2 (A), FIG. 2 (B), the thing with the same code | symbol shows the same function.

  As shown in FIG. 2A, two loading means 001 are arranged so as to be movable in the width direction so that the width regulating member 002 presses both ends of the sheet material 009 in the width direction. The two width regulating members 002 are configured such that if one is moved inward, the other is moved inward by the same distance, and if one is moved outward, the other is also moved outward by the same distance. When the two width regulating members 002 are brought into contact with the sheet material 009 so as to sandwich the width direction of the sheet material 009 and the distance between the two width regulating members 002 is adjusted to the width of the sheet material 009, the sheet material 009 is obtained. The center of the distance in the width direction is aligned with the center 201 of the loading means 001. Further, the distance between the two width regulating members 002 at that time becomes the width of the sheet material 009. Further, as shown in FIG. 2A, the loading unit 001 is arranged to be movable in the paper feeding direction so that the length regulating member 003 presses the opposite end of the sheet material 009 in the paper feeding direction. ing. The length regulating member 003 is arranged so as to move on the center 201. Further, when this length regulating member 003 is brought into contact with the opposite end of the sheet material 009 in the paper feeding direction, the distance from the end on the paper feeding side of the stacking means 001 to the position of the length regulating member 003 Is the length of the sheet material 009 in the sheet feeding direction.

  Here, in the present embodiment, the two width regulating members 002 sandwiching the sheet material 009 are configured to be movable, but this may adopt other configurations, for example, one width regulating member 002. It is also possible to adopt a configuration in which does not move. In this case, the length regulating member 003 is closer to the width direction regulating member 002 that does not move in the width direction of the sheet material 009 than the center 201, and the position of the length regulating member 003 is whatever the width. It is necessary to be configured to be able to hold the opposite end in the paper feeding direction even for other paper. For example, the sheet material 009 having any width can be pressed by disposing the length regulating member 003 at the same position in the width direction as the width direction regulating means 002 that does not move.

  A user or an operator places a sheet material 009 of a predetermined size (for example, A4 size sheet material 009) in advance on the stacking unit 001 before actually forming an image using the sheet feeding device. The restricting member 002 and the length restricting member 003 are moved to abut on the width of the sheet material 009 in the sheet feeding direction and the direction orthogonal to the sheet feeding direction of the sheet material 009 (hereinafter referred to as “width direction”). Let Then, the position detection unit 007 detects the position of the first position indicating unit 004 and the second position indicating unit 005 on the sheet material 009 on the loop coil arrangement, and the size determination unit 008 stores the respective positions. . Hereinafter, the stored positions of the first position indicating means 004 and the second position indicating means 005 are referred to as reference positions.

  Next, when image formation is actually performed using the sheet feeding device, the user or the operator places the sheet material 009 on the stacking unit 001. Then, the user or the operator makes contact with the width of the sheet material 009 on which the width regulating member 002 is loaded, and presses the opposite side of the sheet feeding direction of the sheet material 009 on which the length regulating member 003 is loaded. It abuts on the length of the sheet material 009.

  The first position indicating means 004 is provided on the bottom surface of the width regulating member 002 and moves in the width direction as the width regulating member 002 moves.

  The second position instruction unit 005 is provided on the bottom surface of the length regulating member 003 and moves in the paper feeding direction as the length regulating member 003 moves.

  As shown in FIG. 2B, the sensor substrate 006 is arranged so that the loop coils overlap with each other at a predetermined interval along the movement path in the width direction of the first position indicating means 004 (hereinafter referred to as “the sensor substrate 006”). This is referred to as a “first loop coil group 202”.) Further, the loop coils are arranged at predetermined intervals along the movement path in the paper feeding direction of the second position indicating means 005 so as to overlap each other at a constant interval. (Hereinafter, this is referred to as “second loop coil group 203”). Here, in this embodiment, since the length regulating member 003 moves on the center 201 as described above, the moving path of the first position indicating unit 004 is also on the center 201, and the second loop coil group 203 is also on the center 201. However, this varies depending on the movement path of the length regulating member 003 as described above. For example, the width regulating means 002 does not move the length regulating member 003. When arranged at the position, the second loop coil group 203 is arranged side by side in the sheet feeding direction at the same position in the width direction as the width direction regulating means 002 that does not move.

  The loop coil of the sensor substrate 006 can be switched between a loop coil for transmitting and a loop coil for receiving. Further, in the sensor substrate 006, the loop coils of the first loop coil group 202 and the second loop coil group 203 are arranged so as to scan and receive in order in series.

  The position detection unit 007 switches the loop coil of the sensor substrate 006 to the transmission state. Next, the position detecting unit 007 causes the first position indicating unit 004 to transmit a signal by electromagnetic coupling between the loop coil of the substrate sensor 006 and the first position indicating unit 004, and causes the coil of the first position indicating unit 004 to transmit the signal. Electromagnetic induction is generated, and a signal is stored in the coil and capacitor in the resonance circuit of the first position indicating means 004. Thereafter, while the signal is stored, the coil in the resonance circuit and a nearby loop coil are coupled. Thus, the signal is received by all the loop coils switched to the reception state by the position detection means 007. Then, the position detection unit 007 scans all the loop coils of the sensor substrate 006, and acquires the characteristic distribution of the returned signal. The characteristic distribution of the signal is expressed by the horizontal axis representing distance and the vertical axis representing received signal strength with respect to distance. The current position of the first position indicating means 004 can be obtained from the peak position of the characteristic distribution of the signal. In the position detection means 007, the S / N ratio can be improved by increasing the number of turns of the loop coil of the sensor substrate 006, and the resolution in detection can be set to about 0.01 mm. Here, when a signal is sent from the loop coil of the sensor substrate 006, if a loop coil closest to the first position indicating unit 004 can be predicted, the signal may be sent from the loop coil.

  Further, the position detection unit 007 sends the acquired position of the first position instruction unit 004 to the size determination unit 008. Here, the position of the first position indicating means 004 detected and transmitted by the position detecting means 007 is a position on the array of loop coils, and is information on a relative position with respect to the loop coils.

  Next, the position detection unit 007 switches the loop coil of the sensor substrate 006 to the transmission state. Next, the position detecting unit 007 causes the second position indicating unit 005 to transmit a signal by electromagnetic coupling between the loop coil of the sensor substrate 006 and the second position indicating unit 005, and causes the coil of the second position indicating unit 005 to transmit the signal. The electromagnetic induction is generated, and the signal is stored in the coil and the capacitor in the resonance circuit of the second position indicating unit 005. Then, while the signal is stored, the coil of the resonance circuit and the nearby loop coil are coupled. Thus, the signal is received by all the loop coils switched to the reception state by the position detection means 007. Then, the position detection unit 007 scans all the loop coils of the sensor substrate 006, and acquires the characteristic distribution of the returned signal. The current position of the second position indicating unit 005 can be obtained from the peak position of the characteristic distribution of the signal. Here, when a signal is sent from the loop coil of the sensor substrate 006, if the loop coil closest to the second position indicating unit 005 can be predicted, the signal may be sent from the loop coil.

  Further, the position detecting unit 007 sends the acquired position of the second position indicating unit 005 to the size determining unit 008. Here, the position of the second position indicating means 005 detected and transmitted by the position detecting means 007 is also information on the position relative to the loop coil.

  The size determination unit 008 stores the above-described reference position in advance in its own storage unit (not shown). For example, when the loop coil a in FIG. 2B is the first loop coil and the order is counted from the loop coil a, the loop coil b is the 18th loop coil and the loop coil c is the 40th. In the case of A4 size, the position of the first position indicating means 004 is stored as the seventh loop coil, and the position of the second position indicating means is stored as the 25th loop coil. Further, the size determination means 008 stores which loop coil is the boundary between the first loop coil group 202 and the second loop coil group 202 before shipment. For example, as shown in FIG. 2B, it is stored that the loop coil ahead of the 18th loop coil b is the second loop coil group 203.

  Here, the coil at the boundary between the first loop coil group 202 and the second loop coil group 203 is the 18th loop coil b, and the position of the first position indicating means 004 is directly above the fifth loop coil. The case where the position of the second position indicating means 005 is directly above the 30th loop coil will be described.

  The size determining means 008 receives the information on the current position of the first position indicating means 004 and determines whether the number is 18 or less. If it is 18 or less, the width direction information is 18 or more. For example, it is determined that the information is the paper feed direction. Here, since the position of the first position indicating means 004 is directly above the fifth loop coil, it is determined that the width is the sheet material 009. Since the position of the first position indicating means 004 representing the width of the A4 sheet material 009 as the reference position is the seventh position, the distance from the seventh loop coil to the fifth loop coil is calculated. Based on the width of the A4 sheet material 009, the width of the currently detected sheet material 009 is calculated.

  Next, the size determination unit 008 receives the information on the current position of the second position instruction unit 005 and determines whether the information is the width direction information or the sheet feeding direction information. Here, since the position of the second position indicating means 005 is directly above the 30th loop coil, it is determined that the length is in the paper feeding direction. Since the position of the second position indicating means 005 indicating the length in the sheet feeding direction of the A4 sheet material 009 which is the reference position is the 25th position, from the 25th loop coil to the 30th loop coil. And the length of the sheet material 009 currently detected in the paper feeding direction is calculated based on the length of the A4 sheet material 009 in the paper feeding direction.

  As described above, the size determination unit 008 can detect the size of the sheet material 009 by acquiring the currently detected width of the sheet material 009 and the length in the sheet feeding direction. Here, the size is determined as to which regular paper is a standard size, and is determined as it is when it is an irregular size paper.

  An image forming unit 010 having an image forming unit (not shown) receives information on the size of the sheet material 009 from the size determining unit 008, and forms an image on the fed sheet material 009 based on the size information. .

  Next, a flow for determining the size of the sheet material 009 of the sheet feeding device according to the present embodiment will be described with reference to FIG. FIG. 3 is a flowchart for detecting the size of the sheet material 009 of the sheet feeding apparatus according to this embodiment. Here, as a premise in the flowchart of FIG. 3, it is assumed that the operation of storing the reference position has already been performed by the user or the operator.

  Step S001: The user or operator places the sheet material 009 on the loading means 001, and adjusts the width regulating member 002 and the length regulating member 003 to the length of the sheet material 009, respectively.

  Step S002: The position detecting unit 007 sets the loop coil of the sensor substrate 006 to the transmission state, sends a signal to the first position indicating unit 004 by electromagnetic coupling between the first position indicating unit 004 and the loop coil closest thereto. The position instruction means 004 sends the received signal to the loop coil switched to the reception state by the position detection means 007. The position detecting unit 007 detects the position of the first position indicating unit 004 from the characteristic distribution of the signal received by the loop coil.

  Step S003: The size determination means 008 receives the position of the first position instruction means 004 from the position detection means 007, and receives the reference position and the coil at the boundary between the first loop coil group 202 and the second loop coil group 203 shown in FIG. Based on this information, the width of the currently detected sheet material 009 is calculated.

  Step S004: The position detecting means 007 sets the loop coil of the sensor substrate 006 to the transmission state, sends a signal to the second position indicating means 005 by the electromagnetic coupling between the second position indicating means 005 and the loop coil closest thereto. The position instruction unit 005 sends the received signal to the loop coil switched to the reception state by the position detection unit 007. The position detecting unit 007 detects the position of the second position indicating unit 005 from the characteristic distribution of the signal received by the loop coil.

  Step S005: The size determination means 008 receives the position of the second position instruction means 005 from the position detection means 007, and receives the reference position and the coil at the boundary between the first loop coil group 202 and the second loop coil group 203 shown in FIG. Based on this information, the length in the sheet feeding direction of the currently detected sheet material 009 is calculated.

  Step S006: The size determination unit 008 determines the size of the sheet material 009 from the calculated width of the sheet material 009 and the length in the sheet feeding direction.

  As described above, since the size of the sheet material 009 can be determined using position detection capable of setting the resolution to 0.01 mm, the size can be determined with high accuracy. Thereby, it is possible to form an image corresponding to various sizes of paper. Moreover, since the loop coil which all connected is used, control of determination of a structure and size of a machine can be made easy.

  In the present embodiment, the first position instruction means 004 and the second position instruction means 005 are provided at the bottom of each regulating member. However, this may be provided at other positions where the distance moved by each regulating member can be detected. . For example, when one of the width regulating members 002 is fixed and the position in the width direction of the length regulating member 002 is the same as the position in the width direction of the fixed width regulating member 002, paper feeding of the other width regulating member 002 is performed. The first position indicating unit 004 may be provided on the side surface on the direction side, and the second position indicating unit 005 may be provided on the side surface on the width regulating member 002 side to which the length regulating member is fixed. In this case, the sensor substrate 006 is provided to face each position indicating unit. That is, the first loop coil group 202 is supplied to the side surface in the width direction facing the second position instruction means 005 so that the loop coils are arranged in the width direction on the side surface on the paper feeding direction side facing the first position instruction means 004. It is necessary to provide the second loop coil group 203 so that the loop coils are arranged in the paper direction.

Block diagram of a paper feeder according to the present invention (A) Plan view of sheet feeding device according to the present invention (B) Diagram for explaining arrangement of sensor substrate and position indicating means Flowchart of sheet material size detection by the paper feeder according to the present invention

Explanation of symbols

001 Loading means 002 Width restricting member 003 Length restricting member 004 First position indicating means 005 Second position indicating means 006 Sensor substrate 007 Position detecting means 008 Size determining means 009 Sheet material

Claims (4)

A loading means for loading the sheet material;
Two movable width regulating members installed so as to sandwich both ends in the width direction orthogonal to the sheet feeding direction of the sheet material stacked as described above;
A movable length regulating member installed so as to press the rear end in the sheet feeding direction of the stacked sheet material;
First position indicating means having a resonance circuit provided in the width regulating member;
Second position indicating means having a resonance circuit provided in the length regulating member;
A sensor substrate on which a plurality of loop coils capable of switching between transmission and reception are arranged by partially overlapping each other on a path along which each of the first position instruction means and the second position instruction means moves;
A signal is transmitted to the first position indicating means and the second position indicating means from the loop coil in a transmission state by electromagnetic coupling, and the signals received by the first position indicating means and the second position indicating means. Is received by the loop coil switched to the reception state, and the position on the loop coil array of the first position indicating means and the second position indicating means is detected as the current position from the characteristic distribution of the received signal. Position detecting means for
Size determining means for obtaining the size of the sheet material based on the current position of the first position indicating means and the current position of the second position indicating means received from the position detecting means. Paper feeding device to be used. The size determination means includes
A first position indicating means and a second position indicating means when a sheet material of a known predetermined size is loaded, a storage means for storing a reference position which is a position on the array of the respective loop coils;
The sheet feeding device according to claim 1, wherein the size is obtained based on the current position of each of the reference position, the first position instruction unit, and the second position instruction unit.   The sheet feeding device according to claim 1, wherein the sensor substrate scans and receives the loop coils arranged in the width direction and the arrangement direction in series in order. A loading means for loading the sheet material;
Two movable width regulating members installed so as to sandwich both ends in the width direction orthogonal to the sheet feeding direction of the sheet material stacked as described above;
A movable length regulating member installed so as to press the rear end in the sheet feeding direction of the stacked sheet material;
First position indicating means having a resonance circuit provided in the width regulating member;
Second position indicating means having a resonance circuit provided in the length regulating member;
A sensor substrate on which a plurality of loop coils capable of switching between transmission and reception are arranged by partially overlapping each other on a path along which each of the first position instruction means and the second position instruction means moves;
A signal is transmitted to the first position indicating means and the second position indicating means from the loop coil in a transmission state by electromagnetic coupling, and the signals received by the first position indicating means and the second position indicating means. Is received by the loop coil switched to the reception state, and the position on the loop coil array of the first position indicating means and the second position indicating means is detected as the current position from the characteristic distribution of the received signal. Position detecting means for
Size determination means for obtaining the size of the sheet material based on the current position of the first position instruction means and the current position of the second position instruction means received from the position detection means;
A sheet feeding means for feeding the sheet material;
An image forming apparatus comprising: an image forming unit that forms an image on the fed sheet material.

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