Image forming device

Abstract

To provide an image forming device which reduces the amount of data to be processed and simplifies processing when using a line sensor divided into a plurality of blocks.SOLUTION: An image forming device includes a paper sheet conveyance part, an image forming part, and a paper sheet reading unit. The paper sheet reading unit includes a line sensor. The line sensor reads a conveyed paper sheet. The line sensor has a plurality of division line sensors. The division line sensor is arranged at a non-straddling position. The non-straddling position is a position where the distance in a main scanning direction between a gap between the division line sensors and an ideal edge position of all available standard sizes exceeds an allowable value.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to an image forming apparatus that transports paper to be printed and reads the transported paper. [Background technology]

[0002] A reading unit for reading the conveyed paper may be provided in the image forming apparatus. The reading unit includes an image sensor. Patent Document 1 describes an image forming apparatus including the reading unit.

[0003] Specifically, Patent Document 1 describes an image forming apparatus that develops a latent image formed on an image carrier by exposure with a developer, transfers the image to a recording material to form an image, and determines the exposure position by detecting the passing position of the recording material in a direction perpendicular to the conveying direction as the recording material is conveyed to the image forming position, the image forming apparatus having a line sensor as a passing position detection means, and an opening in a part of the area of ​​a conveying guide facing the line sensor at a position where the recording material side edge of the paper width where image formation is frequent passes, and the size of the opening is reduced (see Patent Document 1: claim 1, paragraph

[0032] , etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2005-077975 A Summary of the Invention [Problem to be solved by the invention]

[0005] An image forming apparatus may be provided with an image sensor. For example, a line sensor may be placed in the paper transport path as an image sensor. The line sensor reads the transported paper. Based on the image data obtained by reading the transported paper, the status of the paper currently being transported can be known.

[0006] A line sensor has multiple photoelectric conversion elements. The charge stored in each photoelectric conversion element is read out in sequence. The more photoelectric conversion elements a line sensor contains, the more times the charge is read out in one scan. For this reason, a single line sensor is sometimes divided into multiple blocks. This makes it possible to read out the charge from each block. It is possible to scan one line at high speed without using a high-speed readout signal (clock signal).

[0007] There are various sizes (standard sizes) of paper that can be used in image forming devices. Also, paper may shift to one side or the other in the main scanning direction. The way in which paper shifts is not fixed. The edge of the paper may or may not exceed the boundary between blocks. In other words, the block on the outside or inside in the main scanning direction as viewed from the edge of the paper may or may not read the edge of the paper. In this case, to recognize the position of the edge of the paper, it is necessary to check the image data of multiple blocks that sandwich the boundary. However, the more blocks whose image data are checked, the greater the amount of data that must be processed, which creates a problem of complex control.

[0008] The device described in Patent Document 1 does not mention dividing the line sensor into multiple parts. Therefore, Patent Document 1 does not include any description that can solve the above problem.

[0009] In view of the above problems, the present invention aims to reduce the amount of data to be processed and simplify the processing when a line sensor divided into a plurality of parts is used. [Means for solving the problem]

[0010] The image forming apparatus according to the present invention includes a paper transport section, an image forming section, and a paper reading unit. The paper transport section transports paper. The image forming section forms an image on the transported paper. The paper reading unit includes a lamp and a line sensor. The lamp irradiates light onto the transported paper. The line sensor reads the transported paper. The paper reading unit is provided upstream of the image forming section in the paper transport direction. The line sensor includes a plurality of split line sensors. The split line sensors are arranged in a row. The light receiving elements of the split line sensors are arranged along the main scanning direction. The split line sensors are arranged in a non-straddling position. The non-straddling position is a position where the distance in the main scanning direction between the gap between the split line sensor and the split line sensor and the ideal edge positions of all available standard sizes exceeds a tolerance value. The ideal edge position is the position of the edge of the transported paper when there is no positional deviation in the main scanning direction. The tolerance is set in advance and is the upper limit of the allowable range of deviation of the conveyed paper in the main scanning direction. Effect of the Invention

[0011] According to the present invention, when a line sensor divided into a plurality of blocks is used, the amount of data to be processed can be reduced, and processing can be simplified. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a diagram illustrating an example of a multifunction peripheral according to an embodiment. [Diagram 2] FIG. 1 is a diagram illustrating an example of a multifunction peripheral according to an embodiment. [Diagram 3] FIG. 2 is a diagram illustrating an example of an image forming unit according to the embodiment. [Figure 4] FIG. 1 is a diagram illustrating an example of a multifunction peripheral according to an embodiment. [Diagram 5] FIG. 2 is a diagram illustrating an example of a paper reading unit according to the embodiment. [Figure 6]FIG. 2 is a diagram illustrating an example of a registrationless unit according to the embodiment. [Figure 7] FIG. 1 is a diagram illustrating an example of a multifunction peripheral according to an embodiment. [Figure 8] FIG. 2 is a diagram illustrating an example of a circuit included in the multifunction peripheral according to the embodiment. [Figure 9] FIG. 4 is a diagram illustrating an example of an arrangement of divided line sensors according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] An image forming apparatus according to an embodiment will be described below with reference to Figs. 1 to 9. In the following, a multifunction device 100 will be taken as an example of an image forming apparatus. The multifunction device 100 can print and transmit data based on image data. Note that the image forming apparatus is not limited to the multifunction device 100, and may be, for example, a printer. The elements of the configuration, arrangement, and the like described in the description of this embodiment do not limit the scope of the invention and are merely illustrative examples.

[0014] (Multifunction machine 100) A multifunction peripheral 100 according to an embodiment will be described with reference to Figures 1 to 3. Figures 1 and 2 are diagrams showing an example of the multifunction peripheral 100 according to an embodiment. Figure 3 is a diagram showing an example of an image forming section 5c according to an embodiment.

[0015] As shown in FIG. 1, the multifunction device 100 includes a control unit 1, a storage unit 2, an image reading unit 3, an operation panel 4, and a printer unit 5.

[0016] The control unit 1 controls the operation of the multifunction device 100. The control unit 1 controls the operation of each part of the multifunction device 100 for a job (copying or sending). The control unit 1 includes a main control circuit 11, an image data generation circuit 12, an image processing circuit 13, and a communication circuit 14. For example, the main control circuit 11 is a CPU. The main control circuit 11 performs processing and calculations related to the job. The image data generation circuit 12 includes an A / D conversion circuit. The image data generation circuit 12 processes the analog image signal output by the image reading unit 3 after reading the original document, to generate original image data. The image processing circuit 13 is an integrated circuit for image processing (for example, an ASIC). The image processing circuit 13 performs image processing of the original image data.

[0017] The communication circuit 14 includes a communication control circuit and a communication memory. The communication memory stores communication software. The communication control circuit controls communication based on the communication software. The communication circuit 14 communicates with the computer 200. For example, the computer 200 is a PC or a server. The communication circuit 14 receives print data from the computer 200. The control unit 1 causes the printer unit 5 to print based on the received print data (print job). The operation panel 4 also accepts destination settings. The control unit 1 causes the communication circuit 14 to transmit image data based on the reading of the original to the set destination (scan transmission).

[0018] The memory unit 2 includes a RAM, a ROM, and a storage. For example, the storage is either an HDD or an SSD, or both. The control unit 1 controls each unit based on the programs and data stored in the memory unit 2. The image reading unit 3 includes a light source and an image sensor. The image reading unit 3 reads a document.

[0019] The operation panel 4 includes a display panel 41, a touch panel 42, and hard keys 43. The operation panel 4 accepts settings made by the user. The control unit 1 displays messages, setting screens, and operation images on the display panel 41. For example, the operation images are buttons, keys, and tabs. Based on the output of the touch panel 42, the control unit 1 recognizes the operation image that has been operated. The hard keys 43 include a start key and a numeric keypad. The touch panel 42 and the hard keys 43 accept setting operations (job-related operations) made by the user. For example, they accept settings for the type of job to be executed and job setting values. Based on the output of the operation panel 4, the control unit 1 recognizes the setting contents.

[0020] The multifunction device 100 includes a printer unit 5. The printer unit 5 includes an engine control unit 50, a paper feed unit 5a, a paper transport unit 5b, an image forming unit 5c, an intermediate transfer unit 5d, and a fixing unit 5e. Based on a print instruction from the control unit 1, the engine control unit 50 controls the operations of the paper feed unit 5a, the paper transport unit 5b, the image forming unit 5c, the intermediate transfer unit 5d, and the fixing unit 5e.

[0021] For example, paper feed unit 5a includes a paper cassette 51 that stores set paper, and paper feed rollers 52 that feed paper. When printing, engine control unit 50 causes paper feed unit 5a to supply paper. For example, paper transport unit 5b includes a motor, a pair of transport rollers 53, and a transport guide 54. The space created by transport guide 54 is a path for transporting paper (paper transport path 54a, space). Engine control unit 50 causes paper sent out from paper feed unit 5a to be transported by paper transport unit 5b. Paper to be used for printing passes through paper transport path 54a.

[0022] The image forming section 5c forms an image (toner image). As shown in FIG. 2 and FIG. 3, the image forming section 5c includes image forming units for four colors and an exposure device 56. The multifunction device 100 includes an image forming unit 55B that forms a black image, an image forming unit 55Y that forms a yellow image, an image forming unit 55C that forms a cyan image, and an image forming unit 55M that forms a magenta image. The image forming units 55B to 55M form toner images of different colors. However, the configurations of the image forming units 55B to 55M are basically the same. Therefore, in the following description, the symbols Bk, Y, C, and M that indicate colors will be omitted unless otherwise specified.

[0023] Each image forming unit includes a photoconductor drum 57, a charging device 58, and a developing device 59. During printing, the engine control unit 50 rotates a drum motor (not shown) to rotate the photoconductor drum 57. The engine control unit 50 also causes the charging device 58 to charge the photoconductor drum 57. The engine control unit 50 also causes the exposure device 56 to expose the photoconductor drum 57 based on image data. The developing device 59 contains a developer including toner. The engine control unit 50 causes the developing device 59 to develop the electrostatic latent image on the photoconductor drum 57 with toner.

[0024] The intermediate transfer unit 5d includes an intermediate transfer belt 510, a secondary transfer roller 511, a driving roller 512, primary transfer rollers 513B, 513Y, 513C, and 513M, and driven rollers 514 and 515. The axial directions of the rollers of the intermediate transfer unit 5d are parallel. The intermediate transfer belt 510 is endless. The intermediate transfer belt 510 is passed around the rollers of the intermediate transfer unit 5d. The intermediate transfer unit 5d (intermediate transfer belt 510) receives the primary transfer of the toner image from the photosensitive drum 57. The intermediate transfer unit 5d also performs the secondary transfer of the toner image onto paper.

[0025] Fixing unit 5e includes heater 516 and fixing rotors 517 and 518. Engine control unit 50 causes fixing rotors 517 and 518 to heat and pressurize the paper onto which the toner image has been transferred. Engine control unit 50 causes fixing unit 5e to fix the toner image. Paper transport unit 5b ejects the paper after fixing to the outside of the machine (to ejection tray 519).

[0026] (Paper reading unit 6 and registrationless unit 7) Next, an example of the paper reading unit 6 and the registrationless unit 7 according to the embodiment will be described with reference to Figs. 4 to 7. Fig. 4 is a diagram showing an example of a multifunction device 100 according to the embodiment. Fig. 5 is a diagram showing an example of a paper reading unit 6 according to the embodiment. Fig. 6 is a diagram showing an example of a registrationless unit 7 according to the embodiment. Fig. 7 is a diagram showing an example of a multifunction device 100 according to the embodiment.

[0027] The multifunction device 100 includes a paper reading unit 6 and a registrationless unit 7. The paper reading unit 6 and the registrationless unit 7 are provided on the paper transport path (paper transport path 54a). The paper reading unit 6 reads the transported paper (transported paper). The paper reading unit 6 is provided upstream of the image forming section 5c (secondary transfer roller 511) in the paper transport direction (see FIG. 2). As shown in FIG. 5, a light-transmitting plate 6b is attached to one surface of the paper reading unit 6. The light-transmitting plate 6b is a glass plate or a light-transmitting resin plate. A lamp 6c, a lens 6d, and a line sensor 8 are housed in the sealed space formed by the housing 6a and the light-transmitting plate 6b. The paper reading unit 6 is a CIS-type scanner unit.

[0028] The engine control unit 50 includes an engine control circuit 50a, an engine memory 50b, and a unit control circuit 9. The engine memory 50b stores programs and data for print control. For example, the engine control circuit 50a and the unit control circuit 9 are CPUs. The unit control circuit 9 performs a predetermined process upon receiving an instruction from the engine control circuit 50a. In the multifunction device 100, the unit control circuit 9 controls the operation of the paper reading unit 6 and the registrationless unit 7. The engine control circuit 50a may control the operation of either the paper reading unit 6 or the registrationless unit 7, or both. Also, the main control circuit 11 may control the operation of either the paper reading unit 6 or the registrationless unit 7, or both.

[0029] FIG. 5 is a view of the paper transport path 54a as viewed from the main scanning direction (a direction perpendicular to the paper transport direction). The main scanning direction is the direction in which the line sensor 8 scans (reads). The main scanning direction is also the direction in which the light receiving elements (pixels, photoelectric conversion elements) of the line sensor 8 are arranged. During a print job, the unit control circuit 9 turns on the lamp 6c. FIG. 5 shows an example in which the paper reading unit 6 includes two lamps 6c. The lamps 6c irradiate light along the main scanning direction. For example, the lamps 6c include an LED.

[0030] The line sensor 8 includes multiple light receiving elements. The pixels are arranged in the main scanning direction. Light emitted from the lamp 6c and reflected by the original passes through the lens 6d and enters each pixel of the line sensor 8. When the paper is being transported (during a print job), the unit control circuit 9 causes the line sensor 8 to perform reading. The reading width of the line sensor 8 is narrower than the maximum width in the main scanning direction of printable standard paper.

[0031] The line sensor 8 is divided into a plurality of blocks. In other words, the line sensor 8 includes a plurality of divided line sensors 80. Fig. 4 shows a line sensor 8 including three blocks (divided line sensors 80). A combination of three reading sensors can be used as the line sensor 8. Note that the number of divided line sensors 80 is not limited to three.

[0032] Each divided line sensor 80 includes a plurality of light receiving elements. For convenience, they are referred to as a first divided line sensor 81, a second divided line sensor 82, and a third divided line sensor 83, in that order, from one side in the main scanning direction (the right side in FIG. 4, the side of the fulcrum shaft 76). Each divided line sensor 80 is arranged in a row (single row). As a result, each light receiving element (pixel) of each divided line sensor 80 is aligned along the main scanning direction.

[0033] Here, in the multifunction device 100, the paper is transported by a center paper passing method. The paper feeder 5a (paper cassette 51) regulates the position of the paper so that the center of the paper transport path 54a in the main scanning direction coincides with the center of the transported paper in the main scanning direction. As a result, the paper transporter 5b transports the paper so that the center of the paper transport path 54a in the main scanning direction coincides with the center of the transported paper in the main scanning direction. The dashed line in FIG. 4 is a line indicating the center of the paper and the paper transport path 54a in the main scanning direction. The third divided line sensor 83 is provided at a position to read the center in the main scanning direction. When the paper with the maximum width in the main scanning direction is used, the first divided line sensor 81 is provided at a position to read one end in the main scanning direction. The second divided line sensor 82 is provided between the first divided line sensor 81 and the third divided line sensor 83.

[0034] The unit control circuit 9 inputs a trigger signal TR to each divided line sensor 80. Each divided line sensor 80 includes a charge transfer circuit (shift register, transfer CCD). In accordance with the trigger signal TR, the charge stored in each pixel is transferred to the charge transfer circuit. The charge transfer circuit converts the charge into a voltage. The period of the trigger signal TR is the period of one scan.

[0035] The multifunction device 100 includes a clock signal generating circuit 90. The clock signal generating circuit 90 generates a reading clock signal CLK. The clock signal generating circuit 90 inputs the reading clock signal CLK to each divided line sensor 80. Each divided line sensor 80 outputs one pixel of analog image signal A1 per one reading clock signal CLK. The reading clock signal CLK has a frequency at which one divided line sensor 80 can output all-pixel analog image signals A1 during one period of the trigger signal TR.

[0036] A registrationless unit 7 is provided at a position where a registration roller pair would be provided in a conventional image forming apparatus (see FIG. 2). A conventional registration roller pair is stopped when the leading edge of the paper reaches the paper. The paper is abutted against the stopped registration roller pair to correct skew of the paper. However, when the registration roller pair is used, the paper is temporarily stopped. Therefore, the registrationless unit 7 corrects skew of the paper without stopping it, and transports the paper downstream. The registrationless unit 7 is provided upstream of the image forming section 5c (secondary transfer nip 5n, secondary transfer roller 511) in the paper transport direction (see FIG. 2). The registrationless unit 7 is provided downstream of the paper reading unit 6 in the paper transport direction.

[0037] FIG. 6 shows an example of the registrationless unit 7. As shown in FIG. 6, the registrationless unit 7 includes a case 71 and a moving plate 7a. A gap is provided between the case 71 and the moving plate 7a. In the example of FIG. 6, the case 71 is box-shaped. The moving plate 7a is plate-shaped. The main scanning direction is the longitudinal direction of both the case 71 and the moving plate 7a. The moving plate 7a and the bottom surface (the surface on the moving plate 7a side) of the case 71 are parallel to each other. The upper view of FIG. 6 is an example of a view of the registrationless unit 7 as seen from the upstream side in the paper transport direction in FIG. 2 (the lower side of the multifunction device 100). The lower view of FIG. 6 is a view showing the surface of the case 71 that faces the moving plate 7a (the moving plate 7a is not shown).

[0038] Case 71 houses registrationless roller pair 72 and registrationless motor 73. Registrationless roller pair 72 includes driving roller 74 and driven roller 75. The rotation axis of driving roller 74 and the rotation axis of driven roller 75 are parallel. The peripheral surface of driving roller 74 and the peripheral surface of driven roller 75 are in contact with each other. As shown in FIG. 2, paper is transported from bottom to top. The transported paper enters the nip between driving roller 74 and driven roller 75. The driving force of registrationless motor 73 is transmitted to driving roller 74 by multiple gears. When registrationless motor 73 is rotated, registrationless roller pair 72 rotates. This causes the transported paper to pass through registrationless unit 7 (nip).

[0039] A fulcrum shaft 76 (fulcrum, rotating shaft) is provided on the moving plate 7a. One end of the fulcrum shaft 76 is inserted into and fixed to the moving plate 7a. The fulcrum shaft 76 stands perpendicular to the plane of the moving plate 7a. The fulcrum shaft 76 is inserted into one end of the case 71 in the main scanning direction (direction perpendicular to the paper transport direction). The fulcrum shaft 76 allows the other end of the case 71 (part of the registration-less unit 7) to swing. The case 71 (part of the registration-less unit 7) can be rotated. As shown by the solid arrow in FIG. 4, the other end of the case 71 can swing toward the downstream side or upstream side in the paper transport direction.

[0040] The registrationless unit 7 includes a skew correction mechanism 7b and a positional deviation correction mechanism 7c. To correct skew of the conveyed paper, the skew correction mechanism 7b moves the other side (moving side) of the case 71. The skew correction mechanism 7b includes a correction motor 7d, a correction belt 7e, and a correction tooth surface member 7f.

[0041] For example, the orthodontic motor 7d is a stepping motor. The orthodontic motor 7d is attached to the moving plate 7a. The orthodontic motor 7d can rotate in both forward and reverse directions. A first orthodontic gear 7g is provided on the shaft of the orthodontic motor 7d. An orthodontic tooth surface member 7f (rack teeth) is attached to the surface of the case 71 facing the moving plate 7a. The teeth of the orthodontic tooth surface member 7f are aligned along the paper conveying direction. The orthodontic tooth surface member 7f meshes with the second orthodontic gear 7h. The orthodontic belt 7e is wound around the first orthodontic gear 7g and the second orthodontic gear 7h. When the orthodontic motor 7d is rotated, the first orthodontic gear 7g, the orthodontic belt 7e, and the second orthodontic gear 7h rotate. As a result, the case 71 to which the orthodontic tooth surface member 7f is attached rotates around the fulcrum shaft 76.

[0042] The other side of the registrationless unit 7 (case 71, registrationless roller pair 72) can be moved in a direction (paper transport direction) perpendicular to the main scanning direction. The amount of movement of the other end of the registrationless unit 7 (case 71) by the skew correction mechanism 7b may be about several mm to 5 mm upstream in the transport direction and about several mm to 5 mm downstream from the first home position (first reference position). The first home position will be described in detail later.

[0043] The positional deviation correction mechanism 7c includes a deviation correction motor 7i. For example, the deviation correction motor 7i is a stepping motor. The deviation correction motor 7i is attached to the moving plate 7a. The deviation correction motor 7i can rotate in both forward and reverse directions. A deviation correction gear 7j is provided on the shaft of the deviation correction motor 7i. The deviation correction gear 7j meshes with a correction tooth surface member 7k (rack teeth) formed on the edge of the moving plate 7a. When the deviation correction motor 7i is rotated, the deviation correction motor 7i and the deviation correction gear 7j rotate.

[0044] As a result, the registration-less unit 7 (moving plate 7a and case 71) moves in the main scanning direction. The amount of deviation of the transported paper in the main scanning direction is a maximum of about several millimeters. The range of movement of the registration-less unit 7 in the main scanning direction by the positional deviation correction mechanism 7c may be about several millimeters to 5 mm on one side in the main scanning direction and about several millimeters to 5 mm on the other side, centered on the second home position (second reference position). For example, the positional deviation correction mechanism 7c can move the registration-less unit 7 by 2 mm on each of the one and other sides, centered on the second home position.

[0045] Next, the first home position will be described. The first home position is the position (angle) of the case 71 where the axial direction of the registrationless roller pair 72 is parallel to the main scanning direction. At the first home position, the transported paper is sent in a direction parallel to the paper transport direction and perpendicular to the main scanning direction. A first home sensor 9a is provided to set the position of the registrationless unit 7 (case 71) to the first home position. The first home sensor 9a is a sensor for aligning the position of the case 71 in the rotational direction to the first home position.

[0046] For example, a transmission type optical sensor can be used as the first home sensor 9a. In this case, the first home sensor 9a includes a light emitting element and a light receiving element. A gap is provided between the light emitting surface of the light emitting element and the light receiving surface of the light receiving element. The output level (output voltage value) of the light receiving element changes depending on the amount of light received from the light emitting element. The registration-less unit 7 (case 71) is provided with a detection protrusion 71a. FIG. 6 shows an example in which the detection protrusion 71a is provided at the end of the other side (moving side) in the main scanning direction of the case 71. The first home sensor 9a is provided at a position facing the detection protrusion 71a. When the registration-less unit 7 (case 71) is rotated, the detection protrusion 71a passes through the gap of the first home sensor 9a. The detection protrusion 71a that enters the gap blocks the optical path from the light emitting element to the light receiving element.

[0047] The output of the first home sensor 9a (light receiving element) is input to the unit control circuit 9. The unit control circuit 9 recognizes the output level of the first home sensor 9a (light receiving element). The straightening motor 7d is operated, and based on the point in time when the output level of the first home sensor 9a becomes the level when the detection protrusion 71a is detected, the unit control circuit 9 sets the registrationless unit 7 (case 71) to the first home position. For example, the unit control circuit 9 rotates the straightening motor 7d in the reverse direction and lifts the case 71. When the output level of the first home sensor 9a becomes the level when the detection protrusion 71a is detected, the unit control circuit 9 stops the rotation of the straightening motor 7d and then rotates it forward. After rotating the straightening motor 7d forward for a predetermined number of pulses, the unit control circuit 9 stops the straightening motor 7d. When it stops, the registrationless unit 7 (case 71) is in the first home position.

[0048] For example, when the multifunction peripheral 100 is started by turning on the main power supply, and the power saving mode is released and the active mode (normal mode) is restored, the unit control circuit 9 sets the registrationless unit 7 (case 71) to the first home position.

[0049] As shown in Fig. 2, the registrationless unit 7 is installed so that paper can be removed from the bottom up. Therefore, when the correction motor 7d is not excited, the other side of the case 71 in the main scanning direction tends to lower under its own weight. When the case 71 is maintained at the first home position, the unit control circuit 9 excites the correction motor 7d. This maintains the position of the registrationless unit 7 (case 71).

[0050] The registration-less unit 7 can also be moved in the main scanning direction. Therefore, the second home position is also determined in advance. The second home position is the home position of the moving plate 7a (registration-less unit 7) in the main scanning direction. For example, the center position of the moving range of the registration-less unit 7 (moving plate 7a) in the main scanning direction can be set as the second home position. The second home position is a position where the registration-less unit 7 (moving plate 7a) can be moved to one side in the main scanning direction and also to the other side.

[0051] A second home sensor 9b is provided to set the registrationless unit 7 (movable plate 7a) at the second home position. The second home sensor 9b can be provided at the other end of the movable plate 7a in the main scanning direction (it may be at one end).

[0052] For example, a transmission type optical sensor can be used as the second home sensor 9b. In this case, the second home sensor 9b includes a light emitting element and a light receiving element. A gap is provided between the light emitting surface of the light emitting element and the light receiving surface of the light receiving element. The output level (output voltage value) of the light receiving element changes depending on the amount of light received from the light emitting element.

[0053] The second home sensor 9b is provided at a position where the other end of the moving plate 7a enters the gap when the registration-less unit 7 moves to the other side. The second home sensor 9b is a sensor for detecting that the registration-less unit 7 (moving plate 7a) has moved to the other side in the main scanning direction.

[0054] The output of the second home sensor 9b (light receiving element) is input to the unit control circuit 9. The unit control circuit 9 recognizes the output level of the second home sensor 9b (light receiving element). When the registrationless unit 7 (moving plate 7a) is at the second home position, the unit control circuit 9 operates the misalignment correction motor 7i to move the moving plate 7a to the other side in the main scanning direction. When the output level of the second home sensor 9b reaches the level at which the end of the moving plate 7a in the main scanning direction is detected, the unit control circuit 9 moves the registrationless unit 7 (moving plate 7a) by a predetermined distance to one side in the main scanning direction toward the center position of the moving range in the main scanning direction.

[0055] (Signal processing circuit 91) Next, an example of the signal processing circuit 91 according to the embodiment will be described with reference to Fig. 8. Fig. 8 is a diagram showing an example of a circuit included in the multifunction peripheral 100 according to the embodiment.

[0056] The multifunction device 100 includes a signal processing circuit 91. The signal processing circuit 91 processes and converts the analog image signal A1 output by each divided line sensor 80 to generate image data B1. The image data B1 is a signal that indicates whether or not the conveyed paper on the paper reading unit 6 (light-transmitting plate 6b) has been read.

[0057] The voltage value of the analog image signal A1 of the pixel that reads the conveyed paper becomes larger. The higher the voltage value of the analog image signal A1, the brighter (whiter, lighter in color) the image that is read. Conversely, the voltage value of the pixel analog image signal A1 that reads an area where there is no conveyed paper becomes smaller. The voltage value of the pixel analog image signal A1 that reads the conveyed paper is higher than the voltage value of the pixel analog image signal A1 that does not read the conveyed paper.

[0058] Based on each pixel analog image signal A1, the signal processing circuit 91 generates image data B1. Specifically, the signal processing circuit 91 of the multifunction device 100 is a binarization circuit. The image data B1 is data (signal) obtained by the signal processing circuit 91 (binarization circuit) converting each pixel analog image signal A1 into a binarized signal. In other words, the image data B1 is image data of each divided line sensor. The image data B1 is obtained for each divided line sensor 80.

[0059] When the voltage value of the analog image signal A1 is greater than a predetermined threshold value Vref, the signal processing circuit 91 (binarization circuit) outputs High-level image data B1. When the voltage value of the analog image signal A1 is equal to or less than the threshold value Vref, the signal processing circuit 91 (binarization circuit) outputs Low-level image data B1. The signal processing circuit 91 obtains binarized image data B1 (monochrome image data with 1 bit per pixel).

[0060] The line sensor 8 includes a first divided line sensor 81, a second divided line sensor 82, and a third divided line sensor 83. A signal processing circuit 91 (binarization circuit) is provided for each divided line sensor 80. An analog image signal A1 for each pixel of the first divided line sensor 81 is input to the first signal processing circuit 91. An analog image signal A1 for each pixel of the second divided line sensor 82 is input to the second signal processing circuit 91. An analog image signal A1 for each pixel of the third divided line sensor 83 is input to the third signal processing circuit 91.

[0061] Each signal processing circuit 91 has the same configuration. An example of the signal processing circuit 91 is shown in the lower part of Fig. 8. The signal processing circuit 91 includes a comparator 92 and a plurality of resistors. The output (analog image signal A1) of the line sensor 8 is input to one input terminal of the comparator 92 in sequence, pixel by pixel. A reference voltage (threshold voltage Vref) generated by voltage division between a first resistor R1 and a second resistor R2 is input to the other input terminal of the comparator 92.

[0062] The comparator 92 binarizes the analog image signal A1. When the voltage value of the analog image signal A1 is greater than a reference voltage, the comparator 92 outputs high-level image data B1. The high level is a level that indicates that the conveyed paper has been read. When the voltage value of the analog image signal A1 is equal to or less than the reference voltage, the comparator 92 outputs low-level image data B1. The low level is a level that indicates that the conveyed paper has not been read.

[0063] The output (image data B1) of each signal processing circuit 91 is input to the unit control circuit 9. The unit control circuit 9 obtains the binary image data (monochrome image data, image data B1) generated by each signal processing circuit 91. The unit control circuit 9 can recognize which pixel of each divided line sensor 80 is at a high level and which pixel of each divided line sensor 80 is at a low level. Based on the image data B1, for example, the unit control circuit 9 can recognize (determine) the direction and angle of inclination of the transported paper.

[0064] (Recognition of the skew angle of transported paper) Next, an example of recognition of the skew angle of the transported paper based on image data B1 will be described. Two pixels (reference point pixels) are determined in advance to determine the skew angle of the transported paper. The reference point pixels are two pixels of the divided line sensor 80. The two reference point pixels may be provided within the reading range of the smallest paper among standard-sized papers that can be used for printing. The distance between the reference point pixels in the main scanning direction may be greater than 1 / 2 the width in the main scanning direction of the smallest paper that can be used for printing. The position of the reference point pixels may differ depending on the size of the paper.

[0065] When the two reference point pixels read the leading edge of the transported paper (become high level) at the same time (line), the unit control circuit 9 recognizes the tilt angle as zero. When one of the two points becomes high level earlier, the unit control circuit 9 recognizes that the transported paper is tilted. When the reference point pixel on one side in the main scanning direction becomes high level earlier, the unit control circuit 9 recognizes that the corner of the transported paper on one side in the main scanning direction is tilted in a direction that protrudes downstream. When the reference point pixel on the other side in the main scanning direction becomes high level earlier, the unit control circuit 9 recognizes that the corner of the transported paper on the other side in the main scanning direction is tilted in a direction that protrudes downstream.

[0066] When the conveyed paper is inclined, the unit control circuit 9 calculates the arc tangent (tan -1Specifically, the unit control circuit 9 may perform the following calculation to obtain the inclination angle. Tilt angle = tan -1 (a / b) Here, a is the transport distance from when one reference point pixel becomes High level to when the other reference point pixel becomes High level. For example, the unit control circuit 9 obtains a by multiplying the number of lines from when one reference point pixel becomes High level to when the other reference point pixel becomes High level by the period of one line and the paper transport speed per unit time. b is the distance in the main scanning direction between the two reference point pixels (component in the main scanning direction). b can be obtained by multiplying the number of pixels from one reference point pixel to the other reference point pixel by the pitch of one pixel. The inclination angle is obtained based on a right triangle with a as the height and b as the base.

[0067] During a print job, the unit control circuit 9 may complete the movement from the home position to the correction position before the paper enters the registrationless unit 7 (the registrationless roller pair 72).

[0068] (1) When a corner on one side (the side of the fulcrum shaft 76) of the paper in the main scanning direction protrudes downstream in the transport direction Before the leading edge of the conveyed paper arrives, the unit control circuit 9 moves the other end (moving side) of the registration-less unit 7 (case 71) upstream in the paper conveying direction. The position where the registration-less unit 7 is moved (rotated) by the same angle as the inclination angle from the first home position is the correction position.

[0069] (2) When the corner on the other side (moving side) in the main scanning direction protrudes toward the downstream side in the transport direction Before the leading edge of the conveyed paper arrives, the unit control circuit 9 moves the other end of the registration-less unit 7 (case 71) downstream in the paper conveying direction. The position where the registration-less unit 7 is moved (rotated) by the same angle as the inclination angle from the first home position is the correction position.

[0070] When the transported paper enters the registrationless roller pair 72, the unit control circuit 9 moves (returns) the registrationless unit 7 (case 71) from the correction position to the first home position. Before the transported paper reaches the secondary transfer nip 5n, the unit control circuit 9 completes the movement to the first home position. By returning to each home position, the skew of the transported paper can be corrected while the paper transport continues.

[0071] (Recognition of the amount of misalignment of conveyed paper in the main scanning direction) Next, an example of recognition of the amount of positional deviation of the conveyed paper in the main scanning direction based on image data B1 will be described. Since the paper is center-passed, the ideal position where the edge of the paper passes is determined for each paper size. In other words, if the position of the conveyed paper is not deviated in the main scanning direction, the pixel position for reading the edge of the paper is determined.

[0072] The unit control circuit 9 determines the position of the pixel of the image data B1 that is at the edge (the most one side) of the high level in the main scanning direction as the actual edge position. The actual edge position is the position of the actual edge of the conveyed paper in the main scanning direction. The memory unit 2 stores data (data for recognizing the amount of deviation D1) that defines the position of the pixel at the edge of the paper when there is no deviation in the main scanning direction for each size of paper in a non-volatile manner (see FIG. 1). The unit control circuit 9 recognizes how many pixels and in which direction the position of the low density pixel (pixel whose analog image signal A1 is equal to or lower than the reference voltage) at the edge of the conveyed paper is deviated from the position defined by the data for recognizing the amount of deviation D1. The unit control circuit 9 can recognize the direction of deviation (whether the deviation is on one side or the other side in the main scanning direction). The unit control circuit 9 also multiplies the number of pixels of deviation by the pitch of one pixel of the image data B1 to determine the amount of deviation in the main scanning direction.

[0073] (1) When the paper position is shifted to one side in the main scanning direction (toward the fulcrum shaft 76) Before the leading edge of the conveyed paper arrives, the unit control circuit 9 moves the registration-less unit 7 (moving plate 7a) to one side in the main scanning direction by the recognized amount of deviation.

[0074] (2) When the paper position is misaligned to the other side (moving side) of the main scanning direction Before the leading edge of the conveyed paper arrives, the unit control circuit 9 moves the registration-less unit 7 (moving plate 7a) to the other side in the main scanning direction by the recognized amount of deviation.

[0075] When the transported paper enters the pair of registrationless rollers 72 after the moving plate 7a has moved, the unit control circuit 9 moves the registrationless unit 7 (case 71) from the correction position to the second home position. Before the transported paper reaches the secondary transfer nip 5n, the unit control circuit 9 completes the movement to the second home position. By returning to the second home position, it is possible to correct the positional deviation in the main scanning direction while continuing transport of the paper.

[0076] (Arrangement of split line sensor 80) Next, an example of the arrangement of the divided line sensors 80 according to the embodiment will be described with reference to Fig. 9. Fig. 9 is a diagram showing an example of the arrangement of the divided line sensors 80 according to the embodiment.

[0077] FIG. 9 shows an example of a diagram of each divided line sensor 80 viewed from a direction perpendicular to the main scanning direction and perpendicular to the paper transport direction (sub-scanning direction). There is an ideal edge position for each of the standard sizes that can be used. The ideal edge position is the position of the edge of the paper in the main scanning direction when the position of the transported paper is not misaligned. The multifunction device 100 can use paper of multiple standard sizes. In other words, the multifunction device 100 supports multiple standard sizes. In the misalignment amount recognition data D1, the position of the pixel corresponding to the ideal edge position is defined for each standard size that can be used.

[0078] The vertical dashed lines in Fig. 9 show an example of the ideal edge position of a usable standard size paper. The vertical solid lines in Fig. 9 are the line (center line CL) that passes through the center of the paper transport path 54a in the main scanning direction and the center of a transported paper that is not misaligned in the main scanning direction.

[0079] Ideally, there would be no misalignment of the conveyed paper in the main scanning direction. However, it is difficult to completely eliminate misalignment. Therefore, in the multifunction device 100, a tolerance is set in advance for the amount of misalignment in the main scanning direction. The tolerance is the upper limit of the allowable range of the amount of misalignment of the conveyed paper in the main scanning direction. For example, the tolerance is several mm. The tolerance may be 2 mm or 3 mm. The tolerance may be shorter than 2 mm or longer than 3 mm.

[0080] The paper cassette 51 (paper feed section 5a) regulates the position of the stored paper. For example, the paper cassette 51 is provided with a regulating plate. For example, the regulating plate regulates the position of the paper so that the center of the paper transport path 54a in the main scanning direction and the center of the paper coincide with each other. However, the position of the paper set in the paper cassette 51 may be slightly shifted. In addition, the position of the paper in the main scanning direction may be slightly shifted due to slippage in the pair of rollers that transport the paper. Even taking these into consideration, the multifunction device 100 is designed so that the amount of deviation of the transported paper in the main scanning direction does not exceed a tolerance. Usually, the amount of deviation from the ideal edge position to one side or the other side in the main scanning direction is up to a tolerance at most. However, this does not mean that deviation in the main scanning direction that exceeds the tolerance does not occur at all. In addition, this does not mean that deviation in the main scanning direction that exceeds the tolerance is not tolerated at all.

[0081] Line sensor 8 is positioned so as to read the edge of the largest paper among the available standard sizes. In other words, paper of the largest supported size passes over the detection surface (light receiving element) of line sensor 8. For example, the largest supported standard size paper is paper that is 13 inches wide in the main scanning direction.

[0082] A case will be described where the maximum width in the main scanning direction of usable standard paper is 13 inches. 13 inches is equivalent to approximately 330.2 mm. If the tolerance is 2 mm, the reading width of line sensor 8 is shorter than the maximum size and is long enough to read the center of the paper and to read one edge of the paper being conveyed even if it is shifted by 2 mm in the main scanning direction. In the example of Figure 9, when standard paper of the maximum supported size is conveyed, the first divided line sensor 81 reads one edge of the paper being conveyed in the main scanning direction.

[0083] Here, there are gaps between the first divided line sensor 81 and the second divided line sensor 82, and between the second divided line sensor 82 and the third divided line sensor 83. In Fig. 9, the gaps are shown with double lines. The actual width of the gap in the main scanning direction is very small. For example, it is 0.1 mm or less. The gaps shown in Fig. 9 are depicted wider than they actually are for emphasis.

[0084] In the following description, the gap between the first divided line sensor 81 and the second divided line sensor 82 will be referred to as a first gap W1. Also, the gap between the second divided line sensor 82 and the third divided line sensor 83 will be referred to as a second gap W2. The first gap W1 and the second gap W2 are gaps that are generated by connecting the divided line sensors 80 together. There are no light receiving elements (pixels) in these gaps.

[0085] Each divided line sensor 80 (first divided line sensor 81, second divided line sensor 82, and third divided line sensor 83) is disposed at a non-straddling position. A non-straddling position is a position where the distance in the main scanning direction between the ideal edge positions of all available standard size paper and the first gap W1 exceeds a tolerance. Also, a non-straddling position is a position where the distance in the main scanning direction between the ideal edge positions of all available standard size paper and the second gap W2 exceeds a tolerance.

[0086] That is, each divided line sensor 80 is disposed at a position in the main scanning direction where the distance between the ideal edge position and the first interval and the distance between the ideal edge position and the second interval are greater than the allowable value. Since they are disposed at non-straddling positions, the lengths in the main scanning direction of first divided line sensor 81, second divided line sensor 82, and third divided line sensor 83 and the number of light receiving elements may be different.

[0087] In the example shown in FIG. 9, the paper with the shortest distance between the ideal edge position and the gap is 16K. The edge of the 16K paper is read by first divided line sensor 81. The distance between the ideal edge position of 16K and second gap W2 is longer than the tolerance. Therefore, even if the conveyed paper is shifted in the main scanning direction, the edge of the 16K paper does not enter the reading range of second divided line sensor 82. The edge of the paper does not straddle the gap.

[0088] If the distance between the ideal edge position and the first interval, and the distance between the ideal edge position and the second interval are closer than the tolerance, the edge of the conveyed paper may straddle the gap. However, by arranging each divided line sensor 80 in a non-straddling position, the edge of the conveyed paper will not straddle the gap. There is no need to check the image data B1 of the two divided line sensors 80 to recognize the actual edge position of the paper.

[0089] 9, when Commercial, C5R, B5R, or Executive paper is used, the unit control circuit 9 can find the actual edge position by checking only image data B1 based on analog image signal A1 from second divided line sensor 82. When 16K, A4R, C4R, B5E, or 13-inch paper is used, the unit control circuit 9 can find the actual edge position by checking only image data B1 based on analog image signal A1 from first divided line sensor 81.

[0090] The operation panel 4 accepts the size of the paper to be used. The control unit 1 recognizes the set paper size. The unit control circuit 9 can recognize the size of the paper to be printed (conveyed). When determining the actual edge position, the unit control circuit 9 determines the actual edge position based on one of image data B1 based on the analog image signal A1 of the second divided line sensor 82 and image data B1 based on the analog image signal A1 of the first divided line sensor 81. In other words, the unit control circuit 9 determines the actual edge position based only on image data B1 of the divided line sensor 80 whose ideal edge position of the conveyed paper overlaps with its reading range when viewed from the sub-scanning direction.

[0091] More specifically, one of the multiple divided line sensors 80 is disposed at a position where the center of the conveyed paper passes through (third divided line sensor 83). The unit control circuit 9 determines the actual edge position based on image data B1 of one of the divided line sensors 80 (first divided line sensor 81 or second divided line sensor 82) disposed outside the third divided line sensor 83 in the main scanning direction.

[0092] Note that there is a possibility that the calculated deviation in the main scanning direction may exceed the allowable value. In this case, the unit control circuit 9 may calculate the same value as the allowable value as the deviation in the main scanning direction of the conveyed paper. In other words, the upper limit of the deviation in the main scanning direction that is calculated may be the allowable value. Then, the unit control circuit 9 may move the case 71 to the lateral deviation correction mechanism by a distance equal to the allowable value.

[0093] In this manner, the image forming apparatus (multifunction device 100) according to the embodiment includes a paper transport section 5b, an image forming section 5c, and a paper reading unit 6. The paper transport section 5b transports paper. The image forming section 5c forms an image on the transported paper. The paper reading unit 6 includes a lamp 6c and a line sensor 8. The lamp 6c irradiates light onto the transported paper. The line sensor 8 reads the transported paper. The paper reading unit 6 is provided upstream of the image forming section 5c in the paper transport direction. The line sensor 8 includes a plurality of split line sensors 80. The split line sensors 80 are arranged in a row. The light receiving elements of the split line sensors 80 are aligned along the main scanning direction. The split line sensors 80 are arranged in a non-straddling position. The non-straddling position is a position where the distance in the main scanning direction between the gap between the split line sensors 80 and the split line sensors 80 and the ideal edge positions of all available standard sizes exceeds a tolerance value in the main scanning direction. The ideal edge position is the position of the edge of the conveyed paper when there is no positional deviation in the main scanning direction. The tolerance is a predetermined value. For example, the tolerance is the upper limit of the allowable range of deviation of the conveyed paper in the main scanning direction.

[0094] Even if the position is shifted in the main scanning direction, the edge of the conveyed paper in the main scanning direction will not enter the reading range of the adjacent divided line sensor 80. This makes it possible to prevent the edge from spanning a gap. When determining the position of the edge of the paper in the main scanning direction, it is necessary to check only the image data B1 of one divided line sensor 80 (image data B1 based on analog image signal A1). The amount of data processing required to recognize the actual edge position of the conveyed paper is reduced. The process of recognizing the actual edge position of the paper can be simplified.

[0095] The image forming apparatus is equipped with a control circuit (unit control circuit 9). The control circuit determines the actual edge position based on the analog image signal A1 of each pixel output by the line sensor 8. The actual edge position is the actual position of the edge of the conveyed paper in the main scanning direction. It is possible to determine the position of the edge (end) of the conveyed paper in the main scanning direction.

[0096] The control circuit finds the actual edge position based only on image data B1 from the divided line sensors 80 whose reading range overlaps with the ideal edge position of the conveyed paper when viewed from the sub-scanning direction. The arrangement of the gaps between the divided line sensors 80 has been designed in such a way that even if the position of the conveyed paper shifts, the edge of the conveyed paper will not enter the reading range of an adjacent divided line sensor 80. There is no need to check image data B1 from the divided line sensors 80 in order to find the actual edge position of the paper. This reduces the amount of data processing.

[0097] One of the multiple split line sensors 80 is placed at a position where the center of the conveyed paper passes (a position that reads the paper center). The control circuit determines the actual edge position based only on image data B1 of one of the split line sensors 80 that is placed outside the split line sensor 80 that reads the center of the conveyed paper in the main scanning direction. This makes it possible to read the center of the paper. This is advantageous for determining the inclination. In addition, the actual edge position can be determined based on image data B1 of the split line sensor 80 that is placed outside the center of the paper.

[0098] The image forming apparatus includes a registrationless unit 7. The registrationless unit 7 is provided upstream of the image forming unit 5c in the paper conveying direction and downstream of the paper reading unit 6 in the paper conveying direction. The registrationless unit 7 includes a registrationless roller pair 72, a registrationless motor 73, a case 71, and a positional deviation correction mechanism 7c. The registrationless roller pair 72 sends the conveyed paper to the image forming unit 5c without stopping the paper. The registrationless motor 73 rotates the registrationless roller pair 72. The case 71 houses the registrationless roller pair 72. The positional deviation correction mechanism 7c moves the case 71 in the main scanning direction. The control circuit calculates the amount of deviation of the conveyed paper in the main scanning direction based on the actual edge position and the ideal edge position. The control circuit moves the case 71 to the positional deviation correction mechanism 7c in a direction in which the deviation in the main scanning direction is eliminated from the time the conveyed paper enters the registrationless roller pair 72 until it passes through the registrationless roller pair 72. The amount of deviation of the conveyed paper in the main scanning direction can be calculated. Furthermore, the deviation in the main scanning direction can be corrected.

[0099] The control circuit moves the case 71 to the position deviation correction mechanism 7c by the distance of the determined deviation in the main scanning direction. Through correction, the deviation of the conveyed paper in the main scanning direction can be eliminated. The image can be printed on the conveyed paper without deviation.

[0100] The upper limit of the movement distance of the case 71 by the misalignment correction mechanism 7c is the tolerance. At the maximum, the paper can be moved in the main scanning direction a distance equal to the tolerance. Even if there is an irregularity, the movement distance of the case 71 and the paper can be kept within the tolerance. Since the upper limit of the movement distance is set, irregularities can be taken into consideration and the number of divided line sensors 80 that check the image data B1 (analog image signal A1) can be prevented from being increased.

[0101] The case 71 has a fulcrum shaft 76 provided at one end side in the main scanning direction. The registration-less unit 7 is equipped with a skew correction mechanism 7b. The skew correction mechanism 7b moves the other end side of the case 71 around the fulcrum shaft 76 to rotate the case 71. Based on the analog image signals A1 output by the multiple divided line sensors 80, the control circuit determines the skew angle of the conveyed paper. The control circuit rotates the case 71 to the skew correction mechanism 7b according to the determined skew angle. The skew angle of the conveyed paper can be determined. Furthermore, the skew of the conveyed paper can be corrected without stopping the conveyed paper.

[0102] Although an embodiment of the present invention has been described above, the scope of the present invention is not limited to this, and various modifications can be made without departing from the spirit of the invention.

[0103] For example, an example has been described in which the line sensor 8 includes three divided line sensors 80. However, the number of divisions may be two, or four or more. Even in this case, each divided line sensor 80 is arranged so that the distance between the gap between each divided line sensor 80 and the ideal edge position exceeds the allowable value. [Industrial Applicability]

[0104] The present invention can be used in an image forming apparatus including a paper reading unit that reads conveyed paper. [Explanation of symbols]

[0105] 100 Multifunction device (image forming device) 5b Paper transport section 5c Image forming unit 6 Paper reading unit 6c Lamp 7 Resistless Unit 71 Case 72 Resistless Roller vs. 73 Resistless Motor 76 Pivot Axis 7b Skew correction mechanism 7c Position deviation correction mechanism 8 line sensor 80 division line sensor 81 1st split line sensor 82 2nd split line sensor 83 3rd division line sensor 9 Unit control circuit (control circuit) A1 Analog image signal W1 First gap W2 Second gap

Claims

1. a paper transport unit that transports paper; an image forming unit that forms an image on the conveyed paper; a paper reading unit including a lamp that irradiates light onto the conveyed paper and a line sensor that reads the conveyed paper; a control circuit for determining an actual edge position based on an analog image signal of each pixel output by the line sensor; Equipped with the paper reading unit is provided upstream of the image forming unit in a paper transport direction, The line sensor includes a plurality of divided line sensors; Each of the divided line sensors is arranged in a row, The light receiving elements of each of the divided line sensors are aligned along the main scanning direction, Each of the split line sensors is disposed in a non-straddling position, the non-straddling position is a position where a distance in the main scanning direction between a gap between the divided line sensors and an ideal edge position of all available standard sizes exceeds a tolerance value, the ideal edge position is a position of the edge of the conveyed paper when there is no positional deviation in the main scanning direction, The tolerance is a predetermined value, the actual edge position is a position of an actual edge of the conveyed paper in the main scanning direction, An image forming device in which the control circuit determines the actual edge position based on image data of only one of the multiple divided line sensors, the ideal edge position of the transported paper overlapping within the reading range when viewed from the sub-scanning direction.

2. One of the plurality of divided line sensors is disposed at a position through which the center of the conveyed paper passes, The image forming apparatus according to claim 1 , wherein the control circuit determines the actual edge position based only on image data of one of the divided line sensors that is arranged outside the divided line sensor that reads the center of the transported paper in the main scanning direction.

3. a registrationless unit provided upstream of the image forming unit in a paper transport direction and downstream of the paper reading unit in the paper transport direction; The resistless unit is a pair of registrationless rollers that feed the conveyed paper to the image forming unit without stopping the paper; a registrationless motor for rotating the registrationless roller pair; a case for accommodating the pair of registrationless rollers; a positional deviation correction mechanism that moves the case in the main scanning direction, The control circuit includes: determining an amount of deviation of the conveyed paper in the main scanning direction based on the actual edge position and the ideal edge position; 3 . The image forming apparatus according to claim 1 , wherein the case is moved toward the positional deviation correction mechanism in a direction in which deviation in the main scanning direction is eliminated during the time from when the conveyed sheet enters the pair of registrationless rollers until when the conveyed sheet passes through the pair of registrationless rollers.

4. 4. The image forming apparatus according to claim 3, wherein the control circuit moves the case to the position deviation correction mechanism by a distance equal to the determined amount of deviation in the main scanning direction.

5. 5. The image forming apparatus according to claim 3, wherein an upper limit of the moving distance of the case caused by the position deviation correction mechanism is the allowable value.

6. the case has a fulcrum shaft provided at one end side in the main scanning direction, the registrationless unit includes a skew correction mechanism that moves the other end of the case around the fulcrum shaft to rotate the case, The control circuit includes: determining an inclination angle of the paper to be conveyed based on the analog image signals output from the plurality of divided line sensors; 6. The image forming apparatus according to claim 3, wherein the skew correction mechanism rotates and moves the case in accordance with the determined skew angle.

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