Detection device and image forming device

Abstract

To provide a detection device which is suitable for a difference in requests for a detection part between before and after heating, compared to the case where a front end and a rear end of the medium before and after heating are detected by the same detection part.SOLUTION: A detection device includes: a first detection part for detecting a front end and a rear end of a medium before heating; and a second detection part which detects the front end and the rear end of the medium after heating, and is different from the first detection part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Patent document 1 discloses an image forming device that has an image forming section for forming images, a paper inversion section for double-sided printing, a guide means for maintaining the position of the paper in the paper inversion section, and a paper position maintaining means that, when paper is transported whose length in the paper transport direction is longer than the length of the transport path within the paper inversion section, continues to maintain the position of the paper using the guide means from the point when the entire paper is contained in the transport path, the transport operation stops, and the rear end of the paper reaches the inversion start position, and ends the maintenance and releases the paper when the next image forming operation becomes possible.

[0003] Patent document 2 discloses a sheet length measuring device having a rotating body that rotates in contact with a sheet material, a measurement mechanism that measures the amount of rotation of the rotating body, and a position detection mechanism that is provided upstream and downstream of the rotating body in the conveying direction of the sheet material, wherein the position detection mechanism has a detection member row in which multiple detection members are arranged, and the position detection mechanism is arranged across the side edges of the sheet material in the width direction and is arranged at an angle with respect to the conveying direction of the sheet material, and the sheet length of the sheet material is measured based on the amount of rotation of the rotating body measured by the measurement mechanism and the end position of the sheet material detected by the position detection mechanism. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4133702 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-114659 Summary of the Invention [Problem to be solved by the invention]

[0005] When a medium such as paper is heated, the state of the medium may change, for example, due to a decrease in moisture content and shrinkage. For this reason, it may be necessary to detect the leading and trailing edges of the medium before and after heating. If these detections are performed using the same detection unit, there is a concern that it may not be easy to achieve compatibility when requirements differ between the medium before and after heating, such as detection accuracy or detection time.

[0006] The present invention aims to provide a detection device that can easily meet the different requirements for media before heating and media after heating, compared to when the front and rear ends of the media are detected using the same detection unit for both media before heating and media after heating. [Means for solving the problem]

[0007] The first aspect includes a first detection unit that detects the leading and trailing ends of the medium before heating, and a second detection unit that detects the leading and trailing ends of the medium after heating and is separate from the first detection unit.

[0008] In a second aspect, the first detection unit and the second detection unit detect the leading edge and trailing edge of the same medium in an unheated state, and perform calibration using the respective detection results.

[0009] In the third aspect, the calibration is performed by correcting a detection error of one of the first and second detection units, which has lower detection accuracy, relative to a detection value of the other of the first and second detection units, which has higher detection accuracy.

[0010] In a fourth aspect, the detector with high detection accuracy is the second detector that detects the leading edge and trailing edge of the medium after heating while the medium is stationary.

[0011] A fifth aspect includes a media transport unit that transports media, an image forming unit that forms an image on the transported media, a heating unit that heats the media on which the image has been formed, a first detection unit that detects the leading and trailing ends of the media before it passes through the heating unit during the image forming operation, and a second detection unit that is separate from the first detection unit and that detects the leading and trailing ends of the media after it has been transported from the first detection unit and passed through the heating unit during the image forming operation, wherein when calibrating the first detection unit and the second detection unit, the first detection unit detects the leading and trailing ends of the media before it passes through the heating unit, and the second detection unit detects the leading and trailing ends of the media after it has been transported from the first detection unit and passed through the heating unit where the surface temperature is lower than during the image forming operation.

[0012] A sixth aspect includes a first detection unit that detects the leading and trailing ends of the medium before heating, a second detection unit that detects the leading and trailing ends of the medium after heating and is separate from the first detection unit, and an image forming unit that forms an image based on the detection results of the first detection unit and the second detection unit, wherein the first detection unit is arranged downstream of a position upstream from the transfer point along the medium transport path, and measures the distance the image travels from the formation point where image formation occurs to the transfer point where the image is transferred to the medium, and the second detection unit is arranged upstream of a position upstream from the transfer point along the medium transport path, and measures the distance the image travels from the formation point where image formation occurs to the transfer point where the image is transferred to the medium.

[0013] The seventh aspect includes a first detection unit that detects the leading and trailing ends of the medium before heating, a second detection unit that detects the leading and trailing ends of the medium after heating and is separate from the first detection unit, an image forming unit that forms an image based on the detection results of the first detection unit and the second detection unit, a first transport path that transports the medium from a media storage unit that stores the medium to the image forming unit, and a second transport path that inverts the medium on which an image has been formed in the image forming unit, wherein the first detection unit is arranged in the first transport path and the second detection unit is arranged in the second transport path.

[0014] In an eighth aspect, the first detector detects the leading and trailing edges of a medium in a conveyed state, and the second detector detects the leading and trailing edges of a medium in a stationary state. [Effects of the Invention]

[0015] According to the configuration of the first aspect, it is possible to easily meet different requirements for the media before heating and the media after heating, compared to when the front and rear ends of the media are detected using the same detection unit for both the media before heating and the media after heating.

[0016] According to the configuration of the second aspect, the accuracy of calibration is improved compared to when the first detection unit and the second detection unit detect the leading and trailing ends of the same medium in heated and unheated states (i.e., different states).

[0017] According to the configuration of the third aspect, by correcting the detection error of the detection unit with higher detection accuracy relative to the detection value of the detection unit with lower detection accuracy, out of the first detection unit and the second detection unit, the detection accuracy of the detection device is improved compared to when calibration is performed.

[0018] According to the configuration of the fourth aspect, the detection accuracy of the detection device is improved compared to when the detection unit with high detection accuracy is the second detection unit that detects the leading and trailing edges of the medium during transport and after heating.

[0019] According to the configuration of the fifth aspect, when calibrating the first detection unit and the second detection unit, the accuracy of the calibration is improved compared to when both the first detection unit and the second detection unit perform the same detection as during image formation operation.

[0020] According to the configuration of the sixth aspect, even if the first detection unit is placed closer to the transfer point due to requirements such as miniaturization, it is possible to have the detection results of the second detection unit reflected in image formation based on the first detection unit and the second detection unit in time.

[0021] According to the configuration of the seventh aspect, the leading edge and trailing edge of the medium transported on each of the first transport path and the second transport path can be detected on each of the first transport path and the second transport path.

[0022] According to the configuration of the eighth aspect, the detection accuracy of the second detection unit can be improved while maintaining the time required for detection by the first detection unit the same as when the first detection unit and the second detection unit detect the leading and trailing ends of a medium being transported. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic diagram illustrating a configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] 1 is a schematic diagram illustrating a configuration in which an electrophotographic image forming unit is used in an image forming apparatus according to an embodiment of the present invention. [Figure 3] 10 is a schematic diagram illustrating a configuration in which a medium storage unit is disposed on a side of a conveyance path in an image forming apparatus according to the present embodiment. FIG. [Figure 4] FIG. 2 is a perspective view showing the configuration of a second detection device according to the present embodiment. [Figure 5] FIG. 2 is a perspective view showing a state in which a first unit and a second unit in the second detection device according to the present embodiment are removed from the detection device main body. [Figure 6] FIG. 2 is a plan view showing the configuration of a second detection device according to the present embodiment. [Figure 7] 10 is a cross-sectional view for explaining positioning at a rear portion of the second detection device according to the embodiment. FIG. [Figure 8] FIG. 10 is a perspective view for explaining positioning at a front portion of the second detection device according to the embodiment. [Figure 9] 10 is a cross-sectional view for explaining positioning at a front portion of the second detection device according to the embodiment. FIG. [Figure 10] 5 is a perspective view showing a state in which the opening / closing unit has been moved to an open position in the configuration shown in FIG. 4. FIG. [Figure 11] FIG. 2 is a perspective view of a detection device main body of the second detection device according to the present embodiment, viewed from below. [Figure 12] FIG. 2 is an enlarged plan view showing a part of the configuration of a second detection device according to the present embodiment. [Figure 13] 12. FIG. 13 is a cross-sectional view taken along line AA in FIG. 6 and a cross-sectional view taken along line AA in FIG. [Figure 14] FIG. 2 is a block diagram illustrating an example of a hardware configuration of one control device according to the present embodiment. [Figure 15] FIG. 2 is a block diagram showing an example of the functional configuration of a processor of one control device according to the present embodiment. [Figure 16] FIG. 2 is a side cross-sectional view of a second detection device according to the present embodiment. [Figure 17] FIG. 2 is a side cross-sectional view of a second detection device according to the present embodiment. [Figure 18] FIG. 10 is a block diagram showing an example of a hardware configuration of another control device according to the present embodiment. [Figure 19] FIG. 10 is a block diagram showing an example of a functional configuration of a processor of another control device according to the present embodiment. [Figure 20] FIG. 4 is a diagram showing a timing chart of the second detection device according to the embodiment. [Figure 21] 10A and 10B are conceptual diagrams for explaining a method for measuring the length of a medium in the transport direction in the second detection device according to the embodiment. [Figure 22] 22 is a diagram showing a state in which the medium is bent in the configuration shown in FIG. 21. FIG. [Figure 23] 10A and 10B are conceptual diagrams for explaining a method for measuring the transport direction length and width direction length of a medium in the second detection device according to the embodiment. [Figure 24] FIG. 2 is a side cross-sectional view showing the configuration of a first detection device according to the present embodiment. [Figure 25] FIG. 2 is a plan view showing the configuration of a first detection device according to the present embodiment. [Figure 26] FIG. 2 is a side cross-sectional view showing the configuration of a first detection device according to the present embodiment. [Figure 27] FIG. 2 is a block diagram showing an example of a hardware configuration of a control device according to the present embodiment. [Figure 28]FIG. 2 is a block diagram showing an example of a functional configuration of a processor of the control device according to the present embodiment. [Figure 29] FIG. 4 is a diagram showing a timing chart of the first detection device according to the embodiment. [Figure 30] 10 is a diagram illustrating measurement of the length in the transport direction of a medium having a cutting error. [Figure 31] 10 is a diagram illustrating measurement of the length of a skewed medium in the transport direction. [Figure 32] 1 is a diagram illustrating measurement of the width direction length of a medium. [Figure 33] 10 is a diagram illustrating a case where a side edge of an upstream portion of a medium in the transport direction is detected. [Figure 34] 10 is a diagram illustrating a case where a side edge of a downstream portion in the transport direction of a medium is detected. DETAILED DESCRIPTION OF THE INVENTION

[0024] An example of an embodiment of the present invention will be described below with reference to the drawings.

[0025] (Image forming device 10) The configuration of an image forming apparatus 10 according to this embodiment will be described below. Fig. 1 is a schematic diagram showing the configuration of an image forming apparatus 10 according to this embodiment.

[0026] In addition, the arrow UP shown in the figure indicates the top (vertically upward) of the device, and the arrow DO indicates the bottom (vertically downward) of the device. Also, the arrow LH shown in the figure indicates the left side of the device, and the arrow RH indicates the right side of the device. Also, the arrow FR shown in the figure indicates the front of the device, and the arrow RR indicates the rear of the device. These directions are defined for the convenience of explanation, and the device configuration is not limited to these directions. In addition, in each direction of the device, the word "device" may be omitted. That is, for example, "above the device" may be simply expressed as "above."

[0027] In the following description, the "up-down direction" may be used to mean "both above and below" or "either above or below." The "left-right direction" may be used to mean "both right and left" or "either right or left." The "left-right direction" may also be referred to as the lateral direction or horizontal direction. The "front-rear direction" may be used to mean "both forward and backward" or "either forward or backward." The front-rear direction corresponds to the width direction described below, and may also be referred to as the lateral direction or horizontal direction. The up-down direction, left-right direction, and front-rear direction are directions that intersect with each other (specifically, directions that are perpendicular to each other).

[0028] In addition, the symbol "x" inside a "circle" in the figure indicates an arrow pointing from the front to the back of the page. In addition, the symbol "·" inside a "circle" in the figure indicates an arrow pointing from the back to the front of the page.

[0029] The image forming apparatus 10 shown in Fig. 1 is an apparatus for forming an image. Specifically, the image forming apparatus 10 is an inkjet image forming apparatus that forms an image on a medium P using ink. More specifically, as shown in Fig. 1, the image forming apparatus 10 has an image forming apparatus main body 11, a medium storage unit 12, a medium discharge unit 13, an image forming unit 14, a heating unit 19, a conveying mechanism 20, a control device 160, and a detection device 100 that includes a first detection device 500 and a second detection device 30.

[0030] The medium P, each part of the image forming apparatus 10, and the image forming operation in the image forming apparatus 10 will be described below.

[0031] (Medium P) The medium P is a target on which an image is formed by the image forming unit 14. Types of the medium P include, for example, paper and film. Examples of paper include cardboard and coated paper. Examples of film include resin film and metal film. In this embodiment, for example, paper is used as the medium P. Note that the types of the medium P are not limited to those described above, and various types of medium P can be used.

[0032] The size (i.e., dimensions) of the medium P is, for example, A3+ or larger, including sizes such as A2, A1, A0, and B series. Note that the size of the medium P is not limited to the above, and various sizes of medium P can be used.

[0033] Here, the length of the medium P along the transport direction is referred to as the transport direction length. The direction intersecting the transport direction of the medium P (specifically, the perpendicular direction) is referred to as the width direction, and the length of the medium P along the width direction is referred to as the width direction length.

[0034] In this embodiment, the upstream end of the medium P in the transport direction may be referred to as the leading end or the upstream end. The downstream end of the medium P in the transport direction may be referred to as the trailing end or the downstream end. The widthwise ends of the medium P may be referred to as the side ends.

[0035] (Detection device 100) The detection device 100 is a device that detects the edge of the medium P. This detection device 100 includes a first detection device 500, a second detection device 30, and a transport mechanism 20. The first detection device 500 is an example of a first detection unit, and has the function of detecting the leading and trailing edges of the medium P before heating. The second detection device 30 is an example of a second detection unit, and has the function of detecting the leading and trailing edges of the medium P after heating. The second detection device 30 is provided as a detection unit separate from the first detection device 500. That is, in this embodiment, the edges of the medium P are detected by separate detection devices (i.e., the first detection device 500 and the second detection device 30) before and after heating the medium P.

[0036] The transport mechanism 20 is an example of a medium transport unit, and has a function of transporting the medium P. Specifically, the transport mechanism 20 has a function of transporting the medium P from the first detection device 500 to the second detection device 30, and also transporting the medium P from the second detection device 30 to the first detection device 500.

[0037] Here, in the detection device 100, "detecting (or sensing) the edge" is not limited to directly detecting (or sensing) the edge (i.e., the edge) of the medium P itself, but also includes, for example, detecting (or sensing) a mark (such as a registration mark) attached to the edge of the medium P. The mark is attached at a predetermined distance from the edge of the medium P, and the distance from the edge of the medium P is known.

[0038] As described above, the transport mechanism 20 is a component of the detection device 100, but it can also be understood as a component constituting part of the image forming apparatus 10 other than the detection device 100. In other words, it can be understood that the transport mechanism 20 serves both as a component of the detection device 100 and as a component of the image forming apparatus 10 other than the detection device 100. The specific configurations of the first detection device 500, the second detection device 30, and the transport mechanism 20 will be described later.

[0039] (Image forming apparatus main body 11) 1, the image forming apparatus main body 11 is a portion in which each component of the image forming apparatus 10 is provided. Specifically, for example, the medium container 12, the image forming unit 14, the heating unit 19, and the detection device 100 (i.e., the conveying mechanism 20, the first detection device 500, and the second detection device 30) are arranged inside the image forming apparatus main body 11. The image forming apparatus main body 11 has a housing 18 divided into multiple portions 18A and 18B. The medium container 12, the image forming unit 14, the heating unit 19, and the first detection device 500 are arranged in the portion 18A of the housing 18. The second detection device 30 is arranged in the portion 18B of the housing 18.

[0040] The first detection device 500 and the second detection device 30 are detachably disposed in the image forming apparatus main body 11. In other words, the first detection device 500 and the second detection device 30 are detachably attached to the image forming apparatus main body 11.

[0041] (medium storage section 12) The medium container 12 is a portion of the image forming apparatus 10 that contains the medium P. The medium P contained in the medium container 12 is supplied to the image forming unit 14.

[0042] (Media discharge section 13) The medium discharge unit 13 is a portion of the image forming apparatus 10 to which the medium P is discharged. The medium P on which an image has been formed by the image forming unit 14 is discharged to the medium discharge unit 13.

[0043] (Image forming unit 14) 1 is an example of an image forming unit that forms an image on the transported medium P. The image forming unit 14 forms an image based on the detection results of the first detection device 500 and the second detection device 30. This point will be described later.

[0044] In this embodiment, the image forming unit 14 uses ink to form an image on the medium P. Specifically, as shown in FIG. 1, the image forming unit 14 has ejection units 15Y, 15M, 15C, and 15K (hereinafter referred to as 15Y to 15K), a transfer body 16, and an opposing member 17 that faces the transfer body 16.

[0045] In the image forming unit 14, each of the ejection units 15Y to 15K ejects ink droplets of each color, yellow (Y), magenta (M), cyan (C), and black (K), onto the transfer body 16 to form an image on the transfer body 16. Furthermore, in the image forming unit 14, the image of each color formed on the transfer body 16 is transferred to the medium P passing through a transfer position TA between the transfer body 16 and an opposing member 17. In this way, an image is formed on the medium P. The transfer position TA can also be said to be an image forming position where an image is formed on the medium P.

[0046] Note that the image forming unit is not limited to the configuration of the image forming unit 14. For example, the image forming unit may have a configuration in which each of the ejection units 15Y to 15K ejects ink droplets directly onto the medium P without using the transfer body 16.

[0047] (Image forming unit 214) As an example of the image forming section, as shown in FIG. 2, an electrophotographic image forming section 214 that forms an image on the medium P using toner may be used.

[0048] As shown in FIG. 2, the image forming section 214 includes toner image forming sections 215Y, 215M, 215C, and 215K (hereinafter referred to as 215Y to 215K), a transfer body 216, and a transfer member 217.

[0049] In image forming unit 214, toner image forming units 215Y to 215K perform the steps of charging, exposing, developing, and transferring to form toner images of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) on transfer body 216. The toner images of the respective colors formed on transfer body 216 are transferred by transfer member 217 to medium P passing through transfer position TA between transfer body 216 and transfer member 217. In this way, an image is formed on medium P. In this way, an example of an image forming apparatus may be an electrophotographic image forming apparatus.

[0050] As an example of the image forming section, each of the toner image forming sections 215Y to 215K may be configured to form a toner image directly on the medium P without using the transfer body 216.

[0051] (Heating section 19) 1 is an example of a heating unit that heats a medium P on which an image has been formed. As an example, the heating unit 19 heats the medium P without contacting the medium P using a heat source (not shown), thereby drying the ink image.

[0052] An example of the heating unit is not limited to the above-mentioned heating unit 19. An example of the heating unit may be, for example, a device that heats the medium P by contacting the medium P within a range that does not affect the image, and various heating units can be used.

[0053] In an electrophotographic image forming apparatus equipped with the image forming section 214, the heating section 19 functions as, for example, a fixing device that fixes a toner image by heating.

[0054] (Transport mechanism 20) The transport mechanism 20 is a mechanism that transports the medium P. As an example, the transport mechanism 20 transports the medium P using a transport member 29 such as a transport roll. Note that the transport member 29 may be a transport belt or the like, as long as it is a member that can apply a transport force to the medium P and transport the medium P.

[0055] The transport mechanism 20 transports the medium P from the medium storage unit 12 to the image forming unit 14 (specifically, the transfer position TA). Furthermore, the transport mechanism 20 transports the medium P from the image forming unit 14 to the heating unit 19. Furthermore, the transport mechanism 20 transports the medium P from the heating unit 19 to the medium discharge unit 13. Furthermore, the transport mechanism 20 transports the medium P from the heating unit 19 to the image forming unit 14.

[0056] Therefore, the image forming apparatus 10 is formed with a transport path 21 from the medium storage unit 12 to the image forming unit 14, a transport path 22 from the image forming unit 14 to the heating unit 19, and a transport path 23 from the heating unit 19 to the medium discharge unit 13. Furthermore, the image forming apparatus 10 is formed with a transport path 24 from the heating unit 19 to the image forming unit 14.

[0057] The transport path 24 is a transport path that returns the medium P, on one side of which an image has been formed, to the image forming unit 14 (specifically, the transfer position TA). The transport path 24 is also a transport path that turns over the medium P, on one side of which an image has been formed.

[0058] A portion of the transport path 21 and the transport path 24 (specifically, a portion downstream in the transport direction) is shared. Therefore, it is possible to understand that the transport path 25, along which the medium P is transported from the medium storage unit 12, is connected to the transport path 24, and that the medium P is supplied from the medium storage unit 12 to the transport path 24. Therefore, the connection position where the transport path 25 is connected to the transport path 24 can be understood as a supply position 25A where new medium P from the medium storage unit 12 is supplied to the transport path 24 toward the image forming unit 14. In other words, in this embodiment, the medium P is supplied from the supply position 25A to the image forming unit 14 through the transport path 24.

[0059] (Image Forming Operation in Image Forming Apparatus 10) In the image forming apparatus 10, the medium P is transported from the medium storage unit 12 to the image forming unit 14 (specifically, the transfer position TA) via the transport path 21, and a first image (hereinafter sometimes referred to as the "front image") is formed by the image forming unit 14 on one side (i.e., the front side) of the medium P. When an image is formed on only one side of the medium P, the medium P with the front image formed on one side passes through the heating unit 19 and is discharged to the medium discharge unit 13.

[0060] On the other hand, when forming images on both sides of the medium P, the medium P with the front image formed on one side passes through the heating unit 19 and is transported along the transport path 24, where it is turned over and returned to the image forming unit 14 (specifically, the transfer position TA). Then, the image forming unit 14 forms a second image (hereinafter sometimes referred to as a "back side image") on the other side (i.e., the back side) of the heated medium P. In other words, the image forming unit 14 forms an image again. The medium P is then discharged to the medium discharge unit 13 via the heating unit 19.

[0061] (Position of the medium storage unit 12) 1, the medium container 12 is disposed below the transport path 24. Therefore, the medium P in the medium container 12 is supplied to the supply position 25A of the transport path 24 from below.

[0062] As shown in FIG. 3, the medium storage unit 12 may be disposed laterally relative to the transport path 24. In this case, the medium P in the medium storage unit 12 is supplied from the side (the right side in FIG. 3) to the supply position 25A of the transport path 24. In the configuration shown in FIG. 3, the medium storage unit 12 is disposed laterally relative to the image forming unit 14 (specifically, the transfer position TA). This allows the medium P to be supplied from the side to the image forming unit 14 (specifically, the transfer position TA). The image forming apparatus main body 11 is not shown in FIG. 3.

[0063] (Second detection device 30) 1 has the function of detecting the leading and trailing edges of the medium P after heating, as described above. Specifically, during an image forming operation, the second detecting device 30 detects the leading and trailing edges of the medium P that has been conveyed from the first detecting device 500 and passed through the heating section 19 and is in a stationary state. The specific configuration of the second detecting device 30 will be described below.

[0064] Fig. 4 is a perspective view showing the configuration of the second detection device 30. Fig. 5 is a perspective view showing the state in which the first unit 31 and the second unit 32 of the second detection device 30 are removed from the detection device main body 40. Fig. 6 is a plan view showing the configuration of the second detection device 30. Note that Fig. 1 shows the second detection device 30 in a simplified form.

[0065] 4 and 5, the second detection device 30 includes a detection device main body 40, a first unit 31, a second unit 32, an opening / closing section 70, a conveying section 80 (see FIG. 1), front and rear end detection sections 90, side end detection sections 98, a presser member 110 (see FIGS. 12 and 13), a presser member 120 (see FIG. 6), and a rear end sensor 99. The shape of the second detection device 30 and the configuration of each section of the second detection device 30 will be described below. Furthermore, the control device 160, the arrangement of the second detection device 30 in the image forming device 10, and removal of the second detection device 30 from the image forming device main body 11 will be described.

[0066] (Shape of second detection device 30) As shown in FIG. 4, the second detection device 30 has a longer left-right length (corresponding to the length in the transport direction) and a longer front-rear length (corresponding to the length in the width direction) than the length in the up-down direction. That is, the second detection device 30 is formed in a flat shape that is thin in the up-down direction and widens in the up-down direction and the left-right direction (specifically, the horizontal direction). Furthermore, since the second detection device 30 transports media P of sizes A3+ or larger, it has a size of at least A3+ or larger in plan view. The shape of the second detection device 30 is not limited to a flat shape and can be various shapes.

[0067] (Detection device main body 40) 5, the detection device main body 40 is formed in a flat shape that is thin in the vertical direction and wide in the front-rear and left-right directions, similar to the overall shape of the second detection device 30. Specifically, the detection device main body 40 has a plate body 41, a front plate 42, a rear plate 43, and a guide plate 44. The detection device main body 40 is formed, for example, from a metal material such as sheet metal, a resin material, or other materials.

[0068] The plate body 41 is formed in a plate shape that extends in the front-rear and left-right directions and has a thickness in the up-down direction. The upper surface of this plate body 41 serves as a conveying path surface 41A. The plate body 41 is formed with a plurality of openings 41B in which roll sections 842, 852, and 862, which will be described later, are disposed. In this embodiment, as an example, twelve openings 41B are formed. A plurality of reflecting plates 97, which will be described later, are disposed on the upper surface of the plate body 41. In this embodiment, as an example, eight reflecting plates 97 are disposed.

[0069] The front plate 42 is a plate that protrudes downward from the front end of the plate body 41 and is formed integrally with the plate body 41. The front plate 42 is formed in a plate shape with its thickness direction extending in the front-to-rear direction. The front plate 42 rotatably supports drive rolls 84, 85, and 86, which will be described later (see FIG. 11).

[0070] The front plate 42 is provided with a support portion 42A that supports the opening / closing portion 70. The support portion 42A is formed by cutting and raising a part of the plate body 41, for example.

[0071] The rear plate 43 is a plate that protrudes upward from the rear end of the plate body 41 and is formed integrally with the plate body 41. The rear plate 43 is formed in a plate shape with its thickness direction in the front-to-rear direction. As will be described later, the rear plate 43 functions as a positioning portion that positions the first unit 31 and the second unit 32. The rear plate 43 is formed with a plurality of insertion holes 45E into which protrusions 51E (described later) are inserted and a plurality of insertion holes 46E into which protrusions 61E (described later) are inserted. In this embodiment, as an example, two insertion holes 45E are formed, and in this embodiment, as an example, three insertion holes 46E are formed. The insertion holes 45E and the insertion holes 46E are elongated holes that are elongated in the left-right direction.

[0072] The guide plate 44 is connected to the right end of the plate body 41. It extends diagonally upward to the right from the right end of the plate body 41. The guide plate 44 has the function of guiding the medium P toward the plate body 41 (i.e., the left side). An opening 44B is formed at the lower end of the guide plate 44, through which the medium P passes as it is transported from the plate body 41 to the right side (i.e., in the second transport direction described below). The guide plate 44 has a relatively small curvature. Specifically, the curvature of the guide plate 44 is smaller than the curvature of the transport path 25, for example. Therefore, the medium P transported along the guide plate 44 is less likely to bend. As a result, the medium P and the image formed on the medium P are less likely to be scratched by rubbing against the guide plate 44.

[0073] (First Unit 31) 4 and 5, the first unit 31 is disposed above the detection device main body 40. Specifically, the first unit 31 is disposed above the left portion of the detection device main body 40. More specifically, the first unit 31 constitutes the upper left portion of the second detection device 30.

[0074] The first unit 31 has a unit main body 50 and a substrate support section 59. The first unit 31 is further provided with driven rolls 87 and 88 (described later) of the conveying section 80, and sensors 91(A), 92(A), and 93(A)(B) and sensor substrates 95(A), 95(B), 95(C), and 95(D) (described later) in the front and rear end detection section 90 and the side end detection section 98. The first unit 31 is formed of, for example, a metal material such as sheet metal, a resin material, or other materials.

[0075] As shown in FIG. 5, the unit body 50 includes a plate 51, a front plate 52, a rear plate 53, a left plate 54, and a right plate 55. The plate 51 is formed like a plate extending in the front-rear and left-right directions and having a thickness in the up-down direction. The lower surface of the plate 51 serves as a conveying path surface 51A (see FIGS. 5, 7, and 13). The plate 51 is formed with an opening 51B in which driven rolls 87 and 88 are disposed, and an opening 51C (see FIG. 6) in which sensors 91(A), 92(A), and 93(A)(B) are disposed. The plate 51 is disposed above the plate 41 of the detection device body 40, facing the plate 41 with a gap between them (see FIGS. 7 and 13).

[0076] The front plate 52 is a plate that protrudes upward from the front end of the plate body 51. The rear plate 53 is a plate that protrudes upward from the rear end of the plate body 51. The front plate 52 and the rear plate 53 are formed in a plate shape with the thickness direction extending in the front-to-rear direction.

[0077] The left plate 54 is a plate that protrudes upward from the left end of the plate body 51. The right plate 55 is a plate that protrudes upward from the right end of the plate body 51. The left plate 54 and the right plate 55 are formed in a plate shape with the thickness direction extending in the left-right direction.

[0078] As shown in Figures 5, 6, and 7(A) and (B), a protrusion 51E is provided at the rear end of the plate body 51, which is inserted into the insertion hole 45E of the rear plate 43 of the detection device main body 40. This protrusion 51E is disposed on the same plane as the plate body 51 and protrudes rearward relative to the rear plate 53. As one example, the protrusion 51E is formed by cutting and raising a portion of the rear plate 53. At the rear of the first unit 31, as shown in Figures 7(A) and (B), the protrusion 51E is inserted into the insertion hole 45E, and the rear plate 53 abuts against the rear plate 43 of the detection device main body 40.

[0079] 8 and 9, a through hole 51D is formed in the front portion of the plate body 51, through which a fastening member 38 such as a bolt is passed. A plurality of through holes 51D are formed in the left-right direction. Then, in the front portion of the first unit 31, the plate body 51 and the plate body 41 are fastened together by the fastening member 38, with a spacer 39 sandwiched between the plate body 51 of the first unit 31 and the plate body 41 of the detection device main body 40.

[0080] The first unit 31 is positioned relative to the detection device main body 40 in the front-rear direction by the rear plate 53 abutting against the rear plate 43 of the detection device main body 40. Furthermore, the first unit 31 is positioned relative to the detection device main body 40 in the up-down direction and the left-right direction by the protrusion 51E being inserted into the insertion hole 45E and the plate body 51 and the plate body 41 being fastened together by the fastening member 38 via the spacer 39.

[0081] Furthermore, the first unit 31 can be removed from the detection device main body 40 by removing the fastening members 38. That is, the first unit 31 is disposed so as to be removable from the detection device main body 40. Note that, in the present embodiment, as described above, the first unit 31 is attached to the detection device main body 40 by the fastening members 38, but the attachment member for attaching the first unit 31 to the detection device main body 40 is not limited to the fastening members 38. The attachment member may be, for example, a clamp or the like, as long as it is a member that can attach the first unit 31 to the detection device main body 40.

[0082] As shown in Figures 4 and 5, the board support portion 59 is a portion that has the function of supporting a sensor board 95, which will be described later. Specifically, as shown in Figure 5, the board support portion 59 has an attachment plate 59A and a connecting plate 59B. The attachment plate 59A is disposed above the plate body 51. A plurality of sensor boards 95 are attached to the attachment plate 59A. The connecting plate 59B extends downward from the attachment plate 59A and is connected to the plate body 51.

[0083] (Second Unit 32) 4 and 5, the second unit 32 is disposed above the detection device main body 40. Specifically, the second unit 32 is disposed above the right portion of the detection device main body 40. More specifically, the second unit 32 constitutes the right portion of the upper part of the second detection device 30. Therefore, the upper part of the second detection device 30 can be divided into the first unit 31 and the second unit 32.

[0084] The second unit 32 has a unit main body 60 and a substrate support section 69. The second unit 32 is further provided with a driven roll 89 (to be described later) of the conveying section 80, sensors 91(B), 92(B), 94(A)(B) (to be described later) in the front and rear end detection section 90 and the side end detection section 98, and sensor substrates 95(E), 95(F), 95(G), 95(H) (to be described later). The second unit 32 is formed of, for example, a metal material such as sheet metal, a resin material, or other materials.

[0085] As shown in FIG. 5, the unit body 60 has a plate body 61, a front plate 62, a rear plate 63, a left plate 64, and a right plate 65. The plate body 61 is formed in a plate shape that extends in the front-rear and left-right directions and has a thickness in the up-down direction. The lower surface of the plate body 61 serves as a conveying path surface 61A (see FIGS. 5 and 7). The plate body 61 is formed with an opening 61B in which a driven roll 89 is disposed, and an opening 61C (see FIG. 6) in which sensors 91(B), 92(B), and 94(A)(B) are disposed. The plate body 61 is disposed above the plate body 41 of the detection device body 40, facing the plate body 41 with a gap between them (see FIG. 7).

[0086] The front plate 62 is a plate that protrudes upward from the front end of the plate body 61. The rear plate 63 is a plate that protrudes upward from the rear end of the plate body 61. The front plate 62 and the rear plate 63 are formed in a plate shape with the thickness direction extending in the front-to-rear direction.

[0087] The left plate 64 is a plate that protrudes upward from the left end of the plate body 61. The right plate 65 is a plate that protrudes upward from the right end of the plate body 61 along the guide plate 44. The left plate 64 is formed in a plate shape with its thickness in the left-right direction.

[0088] As shown in Figures 5, 6, and 7(A) and (B), a protrusion 61E is provided at the rear end of the plate body 61 to be inserted into the insertion hole 46E of the rear plate 43 of the detection device main body 40. This protrusion 61E is disposed on the same plane as the plate body 61 and protrudes rearward relative to the rear plate 63. As one example, the protrusion 61E is formed by cutting and raising a portion of the rear plate 63. Then, at the rear of the second unit 32, as shown in Figures 7(A) and (B), the protrusion 61E is inserted into the insertion hole 46E, and the rear plate 63 abuts against the rear plate 43 of the detection device main body 40.

[0089] 9, a through hole 61D is formed in the front portion of the plate 61, through which a fastening member 38 such as a bolt is passed. A plurality of through holes 61D are formed in the left-right direction. Then, in the front portion of the second unit 32, the plate 61 of the second unit 32 and the plate 41 of the detection device main body 40 are fastened to each other by the fastening member 38, with a spacer 39 sandwiched between them.

[0090] The second unit 32 is positioned relative to the detection device main body 40 in the front-rear direction by the rear plate 63 abutting against the rear plate 43 of the detection device main body 40. The second unit 32 is also positioned relative to the detection device main body 40 in the up-down direction and the left-right direction by the protrusion 61E being inserted into the insertion hole 46E and the plate body 61 and the plate body 41 being fastened together by the fastening member 38 via the spacer 39.

[0091] Moreover, the second unit 32 can be removed from the detection device main body 40 by removing the fastening members 38. That is, the second unit 32 is disposed in a detachable manner relative to the detection device main body 40.

[0092] As shown in Figures 4 and 5, the board support part 69 is a part that has the function of supporting a sensor board 95, which will be described later. Specifically, as shown in Figure 5, the board support part 69 has an attachment plate 69A and a connecting plate 69B. The attachment plate 69A is disposed above the plate body 61. A plurality of sensor boards 95 are attached to the attachment plate 69A. The connecting plate 69B extends downward from the attachment plate 69A and is connected to the plate body 61.

[0093] (Opening and closing part 70) As shown in FIGS. 4 and 10, the opening / closing unit 70 has a function of opening and closing an opening 77 that opens the transport path 80A (see FIG. 1) in the transport unit 80. As shown in FIG. 4, the opening / closing unit 70 is disposed above the detection device main body 40, between the first unit 31 and the second unit 32. The opening / closing unit 70 is disposed between the sensors 91(A) and 92(A) provided in the first unit 31 and the sensors 91(A) and 92(B) provided in the second unit 32, at a position where the sensors 91 to 94 are not present. The opening / closing unit 70 is formed, for example, from a metal material such as sheet metal, a resin material, or other materials.

[0094] 4 and 5, the opening / closing unit 70 has a plate body 71, a front plate 72, a rear plate 73, a left plate 74, and a grip part 76. The plate body 71 is formed in a plate shape that extends in the front-rear and left-right directions and has a thickness in the up-down direction. The lower surface of the plate body 71 serves as a transport path surface 71A (see FIG. 10).

[0095] The front plate 72 is a plate that protrudes upward from the front end of the plate body 71. The rear plate 73 is a plate that protrudes upward from the rear end of the plate body 71. The front plate 72 and the rear plate 73 are formed into plate shapes whose thickness direction is the front-to-rear direction. The left plate 74 is a plate that protrudes upward from the left end of the plate body 71. The left plate 74 is formed into a plate shape whose thickness direction is the left-to-right direction.

[0096] 4 and 10, the opening / closing unit 70 is supported by the detection device main body 40 so as to be able to open and close an opening 77 that opens the transport path 80A (see FIG. 1) in the transport unit 80. That is, the opening / closing unit 70 is movable between a closed position (position shown in FIG. 4) where the opening 77 is closed and an open position (position shown in FIG. 10) where the opening 77 is open. Specifically, the right end of the front plate 72 and the right end of the rear plate 73 of the opening / closing unit 70 are rotatably supported by the support portion 42A and the rear plate 43 of the detection device main body 40, respectively.

[0097] In the closed position, the opening / closing unit 70 is disposed above the plate body 41 of the detection device main body 40, facing the plate body 41 with a gap between them. The gripping portion 76 is provided on the front side of the front plate 72 and protrudes forward from the front plate 72. An operator grips the gripping portion 76 to move the opening / closing unit 70 between the closed position and the open position.

[0098] As an example, the opening / closing unit 70 is opened and closed to clear a blockage (so-called jam) of the medium P that has occurred in the transport path 80A (see FIG. 1). The opening / closing unit 70 is not limited to the above-mentioned use, and may be opened and closed for various purposes, such as cleaning the transport path surface 71A and the transport path surface 41A of the transport path 80A (see FIG. 1). Here, it is required that the medium P and the image are not noticeably scratched. Whether or not a noticeable scratch occurs depends on the curvature of the guide plate 44 and the stiffness of the medium P, and noticeable scratches may also occur due to foreign matter that has entered the transport path 80A. Therefore, it is beneficial to be able to open and clean the transport path 80A.

[0099] (Overview of the conveying unit 80) The transport unit 80 shown in FIG. 1 has a transport path 80B along which the medium P is transported, and in the transport path 80B, the transport of the medium P is stopped and the medium P is pulled in a pulling direction along the transport path 80B.

[0100] Conveying path 80B is a path along which medium P heated by heating unit 19 is transported in second detecting device 30, and is formed by conveying path 80A. Conveying path 80A is a passage formed by conveying path surfaces 41A, 51A, 61A, and 71A. As shown in FIG. 1, conveying path 80A constitutes part of conveying path 24 from heating unit 19 to image forming unit 14.

[0101] Furthermore, in the conveying unit 80, the conveyance of the medium P on which the front side image has been formed is stopped, and after the medium P has stopped, conveyance of the medium P is resumed toward the image forming unit 14 (specifically, the transfer position TA). Specifically, in the conveying unit 80, the medium P is conveyed to the left (hereinafter, the conveyance direction of the medium P before it has stopped is referred to as the "first conveyance direction"), the leftward conveyance of the medium P is stopped, and after the medium P has stopped, conveyance of the medium P is resumed to the right (hereinafter, the conveyance direction of the medium P after it has stopped is referred to as the "second conveyance direction"). That is, in the conveying unit 80, after the medium P has stopped, conveyance is resumed in a second conveyance direction different from the first conveyance direction. Furthermore, the first conveyance direction and the second conveyance direction are opposite directions. In other words, the conveying unit 80 can be said to switch back the medium P. Thus, in this embodiment, the leftward direction corresponds to the first conveyance direction, and the rightward direction corresponds to the second conveyance direction. Note that the conveying unit 80 conveys one sheet of medium P. Furthermore, the transport unit 80 stops the medium P at a predetermined stopping position.

[0102] As described above, in the transport unit 80, the medium P is transported in the transport direction on the transport path 80B, and then transport of the medium P in the transport direction is stopped. Furthermore, in the transport unit 80, the medium P whose transport has been stopped is pulled in a direction along the transport path 80B (hereinafter referred to as the pulling direction). The pulling direction is a direction that includes the first transport direction and the second transport direction.

[0103] As described above, since the first and second conveying directions are opposite to each other, the upstream side of the first conveying direction can be regarded as the downstream side of the second conveying direction, and the downstream side of the first conveying direction can be regarded as the upstream side of the second conveying direction. Therefore, in the second detection device 30, each member arranged on the upstream side of the first conveying direction can be regarded as a member arranged on the downstream side of the second conveying direction, and each member arranged on the downstream side of the first conveying direction can be regarded as a member arranged on the upstream side of the second conveying direction.

[0104] In the description of the second detection device 30, the "conveying direction" refers to the "first conveying direction." Therefore, in the description of the second detection device 30, the "first conveying direction" may be simply referred to as the "conveying direction."

[0105] (Specific configuration of the conveying unit 80) 16 and 17, the transport unit 80 specifically has an upstream transport unit 80X that transports the medium P in a first transport direction on the transport path 80B and stops the transport, and a downstream transport unit 80Y that is disposed downstream in the transport direction from the upstream transport unit 80X and transports the medium P in the first transport direction on the transport path 80B and stops the transport. Note that in FIGS. 16 and 17, for simplicity of illustration, the transport path surfaces 51A, 61A, and 71A are shown as a single unit.

[0106] The upstream transport section 80X has a transport member 83. The transport member 83 is disposed in an upstream portion of the second detection device 30 in the transport direction (specifically, in a portion on the right side).

[0107] The downstream transport unit 80Y has transport members 81 and 82. The transport members 81 and 82 are arranged downstream in the transport direction relative to the transport member 83 (specifically, on the left side). Specifically, the transport member 82 is arranged upstream in the transport direction relative to the transport member 81 and downstream in the transport direction relative to the transport member 83. Each of the transport members 81, 82, and 83 has a function of transporting the medium P in a first transport direction (corresponding to the left) on the transport path 80B and stopping the transport. Furthermore, the transport members 81, 82, and 83 have a function of pulling the medium P in a pulling direction on the transport path 80B. The transport members 81, 82, and 83 have a function of transporting the medium P in a second transport direction (corresponding to the right) on the transport path 80B. The transport members 81 and 82 are an example of a downstream transport unit, and the transport member 83 is an example of an upstream transport unit. Furthermore, the conveying member 81 is an example of a first conveying section, and the conveying member 82 is an example of a second conveying section.

[0108] The transport members 81, 82, 83 each have a driving roll 84, 85, 86 as a rotating member that is rotated to apply a transport force to the medium P, and a driven roll 87, 88, 89 as a driven member that is driven by the driving roll 84, 85, 86, respectively.

[0109] As shown in Fig. 11, the drive rolls 84, 85, and 86 each have a shaft portion 841, 851, and 861, roll portions 842, 852, and 862, and connection portions 843, 853, and 863. The shaft portions 841, 851, and 861 are arranged along the front-rear direction. One axial end portion (specifically, the front end portion) of each of the shaft portions 841, 851, and 861 is rotatably supported by the front plate 42 of the detection device main body 40. The other axial end portion (specifically, the rear end portion) of each of the shaft portions 841, 851, and 861 is rotatably supported by a shaft portion support portion (not shown) provided on the plate body 41 of the detection device main body 40.

[0110] The roll portions 842, 852, 862 are arranged at intervals along the axial direction of the shaft portions 841, 851, 861. Each of the roll portions 842, 852, 862 protrudes upward from the opening 41B of the plate body 41. That is, the roll portions 842, 852, 862 of the drive rolls 84, 85, 86 (i.e., the portions that contact the medium P) protrude upward from the transport path surface 41A of the detection device main body 40. In this embodiment, four roll portions 842, 852, 862 are provided, as indicated by the reference characters (A), (B), (C), and (D) in the drawing.

[0111] The connecting portions 843, 853, and 863 are connected to the connecting portions 743, 753, and 763, which rotate by driving force from driving sources 777 and 778, such as motors. The connecting portions 843, 853, and 863 and the connecting portions 743, 753, and 763 are configured as shaft joints (also referred to as couplings) that are axially connected to each other. The driving force from the driving source 777 is transmitted to the connecting portions 743 and 753 via transmission members such as gears (not shown). As a result, the conveying member 81, which includes the driving roll 84 and the driven roll 87, and the conveying member 82, which includes the driving roll 85 and the driven roll 88, are rotated by the common driving source 777. On the other hand, the driving force from the driving source 778 is transmitted to the connecting portion 763 via transmission members such as gears (not shown). As a result, the conveying member 83, which includes the driving roll 86 and the driven roll 89, is rotated by the driving source 778. The control device 160 functions as a control unit that controls the driving of the driving sources 777 and 778 .

[0112] In the present embodiment, as an example, the connection portions 743, 753, 763, the drive sources 777, 778, and the control device 160 are provided in the image forming apparatus main body 11. That is, in the present embodiment, the connection portions 743, 753, 763, the drive sources 777, 778, and the control device 160 are understood to be not components of the second detection device 30. In this way, the drive rolls 84, 85, 86 are rotated by the drive forces of the drive sources 777, 778 arranged in the image forming apparatus main body 11 being transmitted to the roll portions 842, 852, 862 via the shaft portions 841, 851, 861 by connecting the connection portions 843, 853, 863 to the connection portions 743, 753, 763 arranged in the image forming apparatus main body 11.

[0113] 4 and 5, a plurality of driven rolls 87, 88, 89 are provided. Specifically, the number of driven rolls 87, 88, 89 is the same as the number of roll portions 842, 852, 862. In this embodiment, four driven rolls 87, 88, 89 are provided, as indicated by the reference characters (A), (B), (C), and (D) in the drawings.

[0114] Each of the driven rolls 87, 88, and 89 is disposed opposite one of the roll sections 842, 852, and 862. That is, a plurality of each of the driven rolls 87, 88, and 89 (four in this embodiment) are disposed along the front-to-rear direction. The reference symbols (A), (B), (C), and (D) assigned to each of the driven rolls 87, 88, and 89 are assigned in this order from the roll disposed on the front side to the roll disposed on the rear side.

[0115] Each of the driven rolls 87(A) and 87(B), and the driven rolls 88(A) and 88(B) is arranged with a sensor 93(A) (described later) sandwiched between them in the front-to-back direction when viewed in a direction perpendicular to the image forming surface of the medium P.

[0116] Roll section 842(A) and roll section 842(B), and roll section 852(A) and roll section 852(B), are each arranged in the front-to-back direction, sandwiching sensor 93(A), which will be described later, when viewed in a direction perpendicular to the image forming surface of medium P.

[0117] Specifically, the driven rolls 87(A) and 87(B) and the roll portions 842(A) and 842(B) each sandwich a left side portion of a sensor 93(A) (described later) in the front-to-rear direction. The driven rolls 88(A) and 88(B) and the roll portions 852(A) and 852(B) each sandwich a right side portion of a sensor 93(A) (described later) in the front-to-rear direction.

[0118] Each of the driven rolls 87(C) and 87(D), and the driven rolls 88(C) and 88(D) is arranged with the sensor 93(B) described below sandwiched between them in the front-to-back direction when viewed in a direction perpendicular to the image forming surface of the medium P.

[0119] Roll section 842(C) and roll section 842(D), and roll section 852(C) and roll section 852(D), are each arranged in the front-to-back direction, sandwiching sensor 93(B), which will be described later, when viewed in a direction perpendicular to the image forming surface of medium P.

[0120] Specifically, the driven rolls 87(C) and 87(D) and the roll portions 842(C) and 842(D) each sandwich a left portion of a sensor 93(B) (described later) in the front-to-rear direction. The driven rolls 88(C) and 88(D) and the roll portions 852(C) and 852(D) each sandwich a right portion of a sensor 93(B) (described later) in the front-to-rear direction.

[0121] The driven rolls 89(A) and 89(B) and the roll portions 862(A) and 862(B) are each arranged, when viewed in a direction perpendicular to the image forming surface of the medium P, with the sensor 94(A) described below sandwiched between them in the front-to-back direction.

[0122] The driven rolls 89(C) and 89(D) and the roll portions 862(C) and 862(D) are each arranged on either side of the sensor 94(B) described below in the front-to-back direction when viewed in a direction perpendicular to the image forming surface of the medium P.

[0123] As described above, in this embodiment, the driven rolls 87, 88, 89 and the roll sections 842, 852, 862 are appropriately arranged to sandwich the sensors 93, 94 in the front-to-back direction (i.e., the width direction of the medium P) when viewed in a direction perpendicular to the image forming surface of the medium P.

[0124] Each of the driven rolls 87, 88 is disposed in the first unit 31, as shown in Fig. 5. Each of these driven rolls 87, 88 is rotatably supported by the plate body 51 so that its outer circumferential surface (i.e., the surface that contacts the medium P) protrudes downward from the opening 51B of the plate body 51 of the first unit 31, as shown in Fig. 13. That is, each of the driven rolls 87, 88 has its outer circumferential surface protruding downward from the transport path surface 51A of the first unit 31, and is in contact with each of the roll portions 842, 852.

[0125] The driven rolls 89 are disposed in the second unit 32. Specifically, each of the driven rolls 89, similar to the driven rolls 87 and 88, is rotatably supported by the plate body 61 such that its outer circumferential surface (i.e., the surface that contacts the medium P) protrudes downward from the opening 61B of the plate body 61 of the second unit 32. That is, the outer circumferential surface of the driven roll 89 protrudes downward from the transport path surface 61A of the plate body 61 and is in contact with the roll portion 862.

[0126] In the transport section 80, the drive rolls 84, 85, and 86 and the driven rolls 87, 88, and 89 each sandwich the medium P, and as the drive rolls 84, 85, and 86 are driven to rotate, a transport force is applied to the medium P, and the medium P is transported along the transport path 80B.

[0127] In addition, in the transport unit 80, transport in the first transport direction and transport in the second transport direction on the transport path 80B is performed by changing the rotation direction of the transport members 81, 82, and 83. Furthermore, in the transport unit 80, between transport of the medium P in the first transport direction and transport of the medium P in the second transport direction, the transport of the medium P is stopped and a state is created in which the medium P is pulled in a pulling direction along the transport path 80B (hereinafter, sometimes referred to as a tensile state). The operation of the transport unit 80 is controlled by the control device 160. Specific transport operations in the transport unit 80 will be described later.

[0128] Furthermore, the transport unit 80 has transport path surfaces 41A, 51A, 61A, and 71A that face one side and the other side of the medium P in the tensioned state, respectively (see FIG. 1). As described above, the transport path surface 41A is formed by the upper surface of the plate body 41 of the detection device main body 40 (see FIGS. 5 and 13), and faces the lower surface of the medium P in the tensioned state, guiding the lower surface of the medium P.

[0129] The transport path surface 41A is flat across the entire surface of the medium P. Specifically, the transport path surface 41A is flat across the entire surface of the maximum-sized medium P used in the image forming apparatus 10. Furthermore, the transport path surface 41A is formed larger than the maximum-sized medium P in the transport direction and width direction. The transport path surface 41A may have partial irregularities. The transport path surface 41A may have partial convex portions, for example, by providing a member such as a reflector 97 or by having members such as roll portions 842, 852, and 862 protrude. The transport path surface 41A may also have partial concave portions, for example, by forming holes such as the opening 416B, grooves, or recesses. The transport path surface 41A may also have a structure that reduces the contact area with the medium P by having at least one of concave and convex portions, for example, by forming ribs or drawing a metal plate. Thus, the above-mentioned "flat surface" includes a flat surface having partial irregularities.

[0130] As described above, the transport path surface 51A is formed by the underside of the plate body 51 of the first unit 31 (see Figures 7 and 13), and faces the upper surface of the medium P in the tensioned state, guiding the upper surface of the medium P. As described above, the transport path surface 61A is formed by the underside of the plate body 61 of the second unit 32 (see Figure 7), and faces the upper surface of the medium P in the tensioned state, guiding the upper surface of the medium P. As described above, the transport path surface 71A is formed by the underside of the plate body 71 of the opening / closing section 70 (see Figure 10), and faces the upper surface of the medium P in the tensioned state, guiding the upper surface of the medium P.

[0131] The road surface above the medium P in the tensioned state, which is formed by the transport road surfaces 51A, 61A, and 71A, is flat over the entire surface of the medium P. Specifically, this road surface is flat over the entire surface of the maximum size medium P used in the image forming device 10.

[0132] As described above, the transport members 81 and 82 have the function of transporting the medium P, but they can also be understood as support portions that support the medium P transported by the transport member 83. Specifically, the drive rolls 84 and 85 support the underside of the medium P with roll portions 842 and 852 that protrude upward relative to the transport path surface 41A of the detection device main body 40. The driven rolls 87 and 88 press the medium P against the drive rolls 84 and 85 with their outer peripheral surfaces that protrude downward relative to the transport path surface 51A of the first unit 31.

[0133] In this way, in the transport section 80, the drive rolls 84 and 85 support the lower surface of the medium P at a position above the transport path surface 41A of the detection device main body 40 (ie, at a position away from the transport path surface 41A).

[0134] Conveying members 81 and 82 are arranged at a plurality of positions corresponding to media P with different lengths in the conveying direction. Specifically, conveying member 81 is arranged at a position where it can support the lower end side in the conveying direction of a medium P of the maximum size (specifically, the longest length in the conveying direction) used in image forming apparatus 10. Conveying member 82 is arranged at a position where it can support the lower end side in the conveying direction of a medium P of the minimum size (specifically, the shortest length in the conveying direction) used in image forming apparatus 10.

[0135] (Rear end sensor 99) The trailing end sensor 99 is a detection unit that detects the trailing end of the medium P. The trailing end sensor 99 is disposed on the upstream side in the transport direction relative to the transport member 83. In other words, the trailing end sensor 99 detects the trailing end of the medium P on the upstream side in the transport direction relative to the transport member 83.

[0136] Specifically, the trailing edge sensor 99 is a non-contact sensor that detects the trailing edge of the medium P without coming into contact with the medium P. Even more specifically, the trailing edge sensor 99 is an optical sensor that uses light that is irradiated toward the medium P. Even more specifically, the trailing edge sensor 99 is a reflective optical sensor that detects the trailing edge of the medium P by detecting reflected light of light that is irradiated onto the medium P. Note that a transmissive optical sensor may also be used as the trailing edge sensor 99.

[0137] In this embodiment, as will be described later, each part of the transport unit 80 is operated based on the timing when the trailing edge sensor 99 detects the trailing edge of the medium P.

[0138] (Control device 160) Here, the configuration of the control device 160 will be described. The control device 160 has a control function for controlling the operation of the image forming apparatus 10 including the second detection device 30. In this embodiment, the control device 160 controls the operation of the conveying unit 80 of the second detection device 30. Specifically, as shown in FIG. 18 , the control device 160 has a processor 161, a memory 162, a storage 163, and a timer 164.

[0139] The term "processor" refers to a processor in a broad sense, and processor 161 may be a general-purpose processor (e.g., a CPU (Central Processing Unit)) or a dedicated processor (e.g., a GPU: Graphics Processing Unit, ASIC: Application Specific Integrated Circuit, FPGA: Field Programmable Gate Array, programmable logic device, etc.).

[0140] The storage 163 stores various programs including a control program 163A (see FIG. 19) and various data. Specifically, the storage 163 is realized by a recording device such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), or a flash memory.

[0141] Memory 162 is a work area for processor 161 to execute various programs, and temporarily records various programs or various data when processor 161 executes processing. Processor 161 reads various programs including control program 163A from storage 163 into memory 162, and executes the programs using memory 162 as a work area. Timer 164 is a measurement unit for measuring first, second, and third elapsed times, which will be described later.

[0142] In the control device 160, the processor 161 executes the control program 163A to realize various functions. The following describes the functional configuration realized by the cooperation of the processor 161 as a hardware resource and the control program 163A as a software resource. Figure 19 is a block diagram showing the functional configuration of the processor 161.

[0143] 19, in the control device 160, the processor 161 executes the control program 163A to function as an acquisition unit 161A and a control unit 161C. The acquisition unit 161A acquires detection information indicating that the rear end of the medium P has been detected by the rear end sensor 99.

[0144] The control unit 161C controls the transport unit 80 (specifically, the drive sources 777 and 778) to perform the transport operation described below.

[0145] 20, in the transport section 80, the drive rolls 84, 85, and 86 are rotationally driven to rotate in the forward direction (counterclockwise in FIG. 16), and the driven rolls 87, 88, and 89 are driven to rotate in the forward direction (clockwise in FIG. 16), thereby transporting the medium P in the first transport direction (corresponding to the left).

[0146] Next, after the first elapsed time has elapsed since the trailing edge sensor 99 detected the trailing edge of the medium P, the drive roll 86 and the driven roll 89 stop rotating (specifically, start to stop rotating).

[0147] Next, after a second elapsed time has elapsed since the drive roll 86 and the driven roll 89 stopped rotating (specifically, since they started to stop rotating), the drive rolls 84, 85 and the driven rolls 87, 88 also stop rotating (specifically, since they started to stop rotating). This brings the medium P to a stopped state. In this way, the drive roll 86 and the driven roll 89, and the drive rolls 84, 85 and the driven rolls 87, 88 stop rotating with a time difference, and the medium P is pulled in the pulling direction. That is, the medium P is stopped from being transported in the transport path 80B and is pulled in the pulling direction.

[0148] Then, after a third elapsed time has elapsed since the drive rolls 84 and 85 stopped rotating (specifically, since they started to stop rotating), the drive rolls 84, 85, and 86 rotate in the reverse direction (clockwise in FIG. 16), and the driven rolls 87, 88, and 89 rotate in the reverse direction (counterclockwise in FIG. 16), thereby transporting the medium P in the second transport direction (corresponding to the right).

[0149] In this way, in the conveying unit 80, the conveying members 81, 82, and 83 (drive rolls 84, 85, and 86 and driven rolls 87, 88, and 89) convey the medium P in the first conveying direction and then stop the conveying. Furthermore, after the conveying member 83 stops conveying the medium P, the conveying members 81 and 82 also stop conveying the medium P, causing the conveying members 81, 82, and 83 to pull the medium P in the pulling direction. Then, the ends of the medium P in the pulled state (specifically, the front and rear ends and a pair of side ends) are detected by the front and rear end detection unit 90 and the side end detection unit 98, as described below.

[0150] Since the conveying members 81 and 82 are driven by a common driving source 777, the conveying member 81 rotates (forward and reverse) and stops together with the conveying member 82.

[0151] As described above, in this embodiment, the rotation of the transport member 83 is stopped based on the detection timing when the rear end sensor 99 detects the rear end of the medium P, and the transport member 83 stops transporting the medium P so that the amount by which the rear end of the medium P protrudes from the transport member 83 upstream in the transport direction becomes approximately the same regardless of the length of the medium P in the transport direction. Furthermore, the transport members 81, 82, and 83 re-transport the medium P from the end side where the amount of protrusion has become approximately the same (i.e., the upstream end side in the transport direction (specifically, the right end side)).

[0152] FIG. 16 shows the stopping positions on the transport path 80B where the smallest size medium P stops, and FIG. 17 shows the stopping positions on the transport path 80B where the largest size medium P stops.

[0153] At this stop position, the upstream portion of the smallest-sized medium P in the transport direction is sandwiched between the drive roll 86 and the driven roll 89, and the downstream portion in the transport direction is sandwiched between the drive roll 85 and the driven roll 88. Therefore, the transport member 82 (drive roll 85 and driven roll 88) pulls the smallest-sized medium P together with the transport member 83 (drive roll 86 and driven roll 89).

[0154] At the stop position, the upstream portion of the maximum-sized medium P in the transport direction is sandwiched between the drive roll 86 and the driven roll 89, and the downstream portion of the maximum-sized medium P in the transport direction is sandwiched between the drive roll 84 and the driven roll 87. Therefore, the transport member 81 (drive roll 84 and driven roll 87) pulls the maximum-sized medium P together with the transport member 83 (drive roll 86 and driven roll 89).

[0155] The maximum size medium P is an example of a "medium whose length in the transport direction is equal to or greater than a predetermined length," and is at least the medium P whose length in the transport direction is the maximum. The minimum size medium P is an example of a "medium whose length in the transport direction is less than a predetermined length," and is at least the medium P whose length in the transport direction is the minimum.

[0156] Although the control device 160 is disposed in the image forming apparatus 10, this is not limiting. For example, the control device 160 may be disposed in the second detection device 30 or another device disposed outside the image forming apparatus 10, and the location of the control device 160 is not limited. Furthermore, the control device 160 may be configured as a component of the detection device 100, for example.

[0157] (Front and rear end detection unit 90) The front and rear end detector 90 has a function of detecting the front and rear ends of the medium P when the transport is stopped and the medium P is being pulled in the pulling direction.

[0158] As shown in FIGS. 5 and 6, the front and rear end detection unit 90 includes sensors 91, 92, 93, and 94 (hereinafter referred to as 91 to 94), a sensor board 95, wiring 96 (see FIG. 6), and a reflector 97 (see FIG. 5).

[0159] 5 and 6, a plurality of sensors 93 and 94 are provided. Specifically, a pair (i.e., two) of sensors 93 and 94 are provided, as indicated by the symbols (A) and (B) in the drawings.

[0160] Sensor 93 is a detection unit that detects the leading edge of medium P. Sensor 94 is a detection unit that detects the trailing edge of medium P. Sensors 93 and 94 are non-contact sensors that detect the edges of medium P without coming into contact with medium P. More specifically, sensors 93 and 94 are optical sensors that use light irradiated toward medium P. Even more specifically, sensors 93 and 94 have multiple detection elements (specifically, light-emitting elements and light-receiving elements) arranged along the transport direction and are configured as line sensors that are elongated in the transport direction. Even more specifically, sensors 93 and 94 are configured as contact image sensors (CIS), as an example. Note that line sensors other than contact image sensors may be used as sensors 93 and 94.

[0161] In sensors 93 and 94, a detection area is formed by multiple detection elements arranged along the transport direction. The length of the detection area in the transport direction is the same as or shorter than the length of sensors 93 and 94 in the transport direction. Sensors 93 and 94 detect the position of the edge of medium P at the boundary between detection and non-detection of each detection element in the detection area, and position information indicated by the coordinates (specifically, the number of pixels from the downstream end of the detection area in the transport direction) is sent to, for example, control device 160.

[0162] The sensor 93 is disposed in a downstream portion of the second detection device 30 in the transport direction (specifically, the left portion). The sensor 93 is disposed in a position facing the downstream end of the tensioned medium P in the transport direction. Specifically, the sensor 93 is disposed so that its longitudinal direction intersects with the downstream end of the tensioned medium P in the transport direction when viewed in a direction perpendicular to the image forming surface of the medium P, and detects this downstream end. More specifically, the sensor 93 is disposed so that its detection area intersects with the downstream end of the tensioned medium P in the transport direction when the tensioned medium P is stopped at a predetermined position when viewed in a direction perpendicular to the image forming surface of the medium P. In other words, the sensor 93 is disposed so that the downstream end of the tensioned medium P in the transport direction when the tensioned medium P is stopped at a predetermined position is located between one end and the other end of the longitudinal direction of the detection area of ​​the sensor 93.

[0163] The sensor 94 is disposed in an upstream portion of the second detection device 30 in the transport direction (specifically, the right side portion). This sensor 94 is disposed in a position facing the upstream end of the tensioned medium P in the transport direction. Specifically, the sensor 94 is disposed so that its longitudinal direction intersects with the upstream end of the tensioned medium P in the transport direction when viewed in a direction perpendicular to the image forming surface of the medium P, and detects this upstream end. More specifically, the sensor 94 is disposed so that its detection area intersects with the upstream end of the tensioned medium P in the transport direction when the tensioned medium P is stopped at a predetermined position when viewed in a direction perpendicular to the image forming surface of the medium P. In other words, the sensor 94 is disposed so that the upstream end of the tensioned medium P in the transport direction when the tensioned medium P is stopped at a predetermined position is located between one end and the other end of the longitudinal direction of the detection area of ​​the sensor 94.

[0164] Specifically, the sensors 93(A) and 94(A) are arranged side by side in the left-right direction in a front portion of the second detection device 30. On the other hand, the sensors 93(B) and 94(B) are arranged side by side in the left-right direction in a rear portion of the second detection device 30.

[0165] In the front and rear end detection unit 90, a plurality of sensor substrates 95, wirings 96, and reflectors 97 are provided. Specifically, the number of sensor substrates 95, wirings 96, and reflectors 97 provided is the same as the number of sensors 93, 94. In the front and rear end detection unit 90, four wirings 96 and four reflectors 97 are provided. Furthermore, four sensor substrates 95 are provided, as indicated by the symbols (B), (C), (F), and (G) in the figure.

[0166] Each of the four sensor substrates 95 is a drive substrate that drives each of the four sensors 93, 94. Each of the four sensor substrates 95 is disposed adjacent to each of the four sensors 93, 94. Specifically, each of the sensors 93, 94 is driven by the sensor substrate 95 disposed closest to it among the four sensor substrates 95. That is, each of the sensors 93(A), 93(B), 94(A), and 94(B) is driven by each of the sensor substrates 95(B), 95(C), 95(F), and 95(G).

[0167] Each of the four wirings 96 is a connection line that electrically connects each of the four sensor substrates 95 with each of the four sensors 93, 94. The four wirings 96 are not bundled together and are spaced apart from one another. In other words, the four wirings 96 are not arranged such that one wiring 96 runs alongside the other wirings 96. The four wirings 96 are also arranged so that they do not cross each other. Each of the four reflecting plates 97 is provided on the conveyance path surface 41A of the plate body 41 of the detection device main body 40, facing each of the four sensors 93, 94. Considering the use of white paper as the medium P, the reflecting plate 97 is colored black, for example, which has a relatively large difference in reflectance from white.

[0168] (Side edge detection unit 98) The side edge detection unit 98 has the function of detecting the side edges of the medium P when the front and rear edge detection unit 90 detects the front and rear edges. In other words, the side edge detection unit 98 detects the side edges of the tensioned medium P. As shown in Figures 5 and 6, the side edge detection unit 98 includes sensors 91 and 92, a sensor board 95, wiring 96 (see Figure 6), and a reflector 97 (see Figure 5).

[0169] 5 and 6, a plurality of sensors 91 and 92 are provided. Specifically, a pair (i.e., two) of sensors 91 and 92 are provided, as indicated by the symbols (A) and (B) in the drawings.

[0170] Sensor 91 is a detection unit that detects one side edge of medium P (specifically, the side edge on the front side of the device). Sensor 92 is a detection unit that detects the other side edge of medium P (specifically, the side edge on the rear side of the device). Sensors 91 and 92 are non-contact sensors that detect the edges of medium P without coming into contact with medium P. More specifically, sensors 91 and 92 are optical sensors that use light irradiated toward medium P. Even more specifically, sensors 91 and 92 are configured as line sensors that have multiple detection elements (specifically, light-emitting elements and light-receiving elements) arranged along the width direction and are elongated in the width direction. Even more specifically, sensors 91 and 92 are configured as contact image sensors (CIS), as an example. Note that line sensors other than contact image sensors may be used as sensors 91 and 92.

[0171] In sensors 91 and 92, a detection area is formed by multiple detection elements arranged along the width direction. The width length of the detection area is the same as or smaller than the width length of sensors 91 and 92. Sensors 91 and 92 detect the position of the edge of medium P at the boundary between detection and non-detection of each detection element in the detection area, and position information indicated by the coordinates (specifically, the number of pixels from the rear end of the detection area) is sent to, for example, control device 160.

[0172] The sensor 91 is disposed in a front portion of the second detection device 30. This sensor 91 is disposed in a position facing one side edge (i.e., one end in the width direction) of the tensioned medium P. Specifically, the sensor 91 is disposed so as to intersect with one side edge of the tensioned medium P in the longitudinal direction when viewed in a direction perpendicular to the image forming surface of the medium P, and detects this one side edge. More specifically, the sensor 91 is disposed so that, when viewed in a direction perpendicular to the image forming surface of the medium P, its detection area intersects with one side edge of the tensioned medium P stopped at a predetermined position in the longitudinal direction. In other words, the sensor 91 is disposed so that one side edge of the tensioned medium P stopped at a predetermined position is located between one end and the other end of the longitudinal direction of the detection area of ​​the sensor 91.

[0173] The sensor 92 is disposed in a rear portion of the second detection device 30. The sensor 92 is disposed in a position facing the other side edge (i.e., the other end in the width direction) of the tensioned medium P. Specifically, the sensor 92 is disposed so that its longitudinal direction intersects with the other side edge of the tensioned medium P when viewed in a direction perpendicular to the image forming surface of the medium P, and detects the other side edge. More specifically, the sensor 92 is disposed so that its detection area intersects with the other side edge of the tensioned medium P stopped at a predetermined position when viewed in a direction perpendicular to the image forming surface of the medium P. In other words, the sensor 92 is disposed so that the other side edge of the tensioned medium P stopped at a predetermined position is located between one end and the other end of the longitudinal direction of the detection area of ​​the sensor 92.

[0174] Specifically, the sensor 91(A) and the sensor 92(A) are arranged side by side along the front-rear direction in a portion of the second detection device 30 on the downstream side in the conveying direction (specifically, the first unit 31). On the other hand, the sensor 91(B) and the sensor 92(B) are arranged side by side along the front-rear direction in a portion of the second detection device 30 on the upstream side in the conveying direction (specifically, the second unit 32).

[0175] Furthermore, in this embodiment, sensors 91 and 92 are located between sensors 93 and 94 in a side view. That is, sensors 91 and 92 are disposed upstream in the transport direction relative to sensor 93 and downstream in the transport direction relative to sensor 94. Note that a side view refers to a view from one side to the other in the width direction of medium P.

[0176] In the side edge detection unit 98, a plurality of sensor substrates 95, wirings 96, and reflectors 97 are provided. Specifically, the same number of sensor substrates 95, wirings 96, and reflectors 97 are provided as the sensors 91, 92. In the side edge detection unit 98, four of each of the wirings 96 and reflectors 97 are provided. Furthermore, four of the sensor substrates 95 are provided, as indicated by the symbols (A), (D), (E), and (H) in the figure.

[0177] Each of the four sensor substrates 95 is a drive substrate that drives each of the four sensors 91, 92. Each of the four sensor substrates 95 is disposed adjacent to each of the four sensors 91, 92. Specifically, each of the sensors 91, 92 is driven by the sensor substrate 95 disposed closest to it among the four sensor substrates 95. That is, each of the sensors 91(A), 92(A), 91(B), and 92(B) is driven by each of the sensor substrates 95(A), 95(D), 95(E), and 95(H).

[0178] Each of the four wirings 96 is a connection line that electrically connects each of the four sensor substrates 95 with each of the four sensors 91, 92. The four wirings 96 are not bundled together and are spaced apart from one another. In other words, the four wirings 96 are not arranged such that one wiring 96 runs alongside the other wirings 96. The four wirings 96 are also arranged so that they do not cross each other. Each of the four reflecting plates 97 is provided on the transport path surface 41A of the plate body 41 of the detection device main body 40, facing each of the four sensors 91, 92. Considering the use of white paper as the medium P, the reflecting plate 97 is colored black, for example, which has a relatively large difference in reflectance from white.

[0179] In this embodiment, the sensor boards 95(A), 95(B), 95(C), and 95(D) are attached to the mounting plate 59A of the board support part 59 so as to be arranged in this order toward the rear side. The sensor boards 95(E), 95(F), 95(G), and 95(H) are attached to the mounting plate 69A of the board support part 69 so as to be arranged in this order toward the rear side.

[0180] In this embodiment, sensors 91(A), 92(A), 93(A)(B) and sensor substrates 95(A), 95(B), 95(C), 95(D) are provided in the first unit 31. Wiring 96 is provided in the first unit 31 to electrically connect each of the sensors 91(A), 92(A), 93(A)(B) to each of the sensor substrates 95(A), 95(B), 95(C), 95(D).

[0181] In this embodiment, sensors 91(B), 92(B), 94(A)(B) and sensor substrates 95(E), 95(F), 95(G), and 95(H) are provided in the second unit 32. Wiring 96 electrically connecting each of sensors 91(B), 92(B), and 94(A)(B) to each of sensor substrates 95(E), 95(F), 95(G), and 95(H) is provided in the second unit 32. As described above, because sensors 91-94 are provided in the first unit 31 and second unit 32, they detect the edge of medium P from above the tensioned medium P. Therefore, adhesion of foreign matter such as paper dust to sensors 91-94 is suppressed compared to when sensors 91-94 detect the edge of medium P from below the tensioned medium P.

[0182] (Pressing member 110) 12 and 13 is a member that presses down the end of the tensioned medium P. Pressing down the end of the medium P means restricting the movement of the end of the medium P from above and below.

[0183] As shown in Figures 12 and 13, a plurality of pressing members 110 are provided. Specifically, in this embodiment, four pressing members 110 are provided, as indicated by the reference characters (A), (B), (C), and (D) in Figure 12. The pressing members 110 are made of a plate-shaped elastic member such as a resin film.

[0184] As shown in Fig. 13, the presser members 110(A) and 110(B) are disposed between the conveying members 81 and 82 in a side view. Also, as shown in Fig. 12, the presser members 110(A) and 110(B) are disposed with the sensor 93(A) sandwiched between them in the front-to-rear direction when viewed in a direction perpendicular to the image forming surface of the medium P.

[0185] 13, the presser members 110(C) and 110(D) are disposed downstream in the conveying direction relative to the conveying member 81 in a side view. Also, as shown in FIG. 12, the presser members 110(C) and 110(D) are disposed with the sensor 93(A) sandwiched between them in the front-to-rear direction when viewed in a direction perpendicular to the image forming surface of the medium P.

[0186] The upstream ends (i.e., right ends) of the pressing members 110(A), 110(B), 110(C), and 110(D) in the conveying direction are attached to the conveying path surface 41A of the detection device main body 40, and the downstream portions (i.e., left portions) in the conveying direction are pressed against the conveying path surface 51A of the first unit 31 by their own elastic force. As a result, the pressing members 110(A), 110(B), 110(C), and 110(D) press the medium P conveyed between them and the conveying path surface 51A against the conveying path surface 51A, thereby pressing the ends (specifically, the downstream ends) of the medium P in a tensioned state.

[0187] Although not shown in Figures 12 and 13, in this embodiment, similar to the configuration described above, a pressure member 110 is arranged to sandwich the sensor 93 (B) in the front-to-back direction when viewed in a direction perpendicular to the image forming surface of the medium P.

[0188] As described above, in this embodiment, the presser members 110 are disposed so as to sandwich the sensor 93 in the front-rear direction as appropriate when viewed in a direction perpendicular to the image forming surface of the medium P.

[0189] (Pressing member 120) 6 is an example of a support unit, and supports the medium P whose side edge is detected by the side edge detection unit 98. Specifically, the presser member 120 presses down the side edge of the medium P in a tensioned state. Note that pressing down the side edge of the medium P means restricting movement of the side edge of the medium P from above and below.

[0190] As shown in Fig. 6, a plurality of pressing members 120 are provided. Specifically, in this embodiment, four pressing members 120 are provided, as indicated by the reference characters (A), (B), (C), and (D) in Fig. 6. The pressing members 120 are made of a plate-shaped elastic member such as a resin film.

[0191] The pressing members 120(A), 120(B), 120(C), and 120(D) are arranged downstream of the conveying member 83 in the conveying direction, and upstream of the conveying member 82 in the conveying direction.

[0192] The pressing member 120(A) is disposed along the sensor 92(A) on the upstream side of the sensor 92(A) in the conveying direction. The length of the pressing member 120(A) in the front-rear direction is approximately the same as the length of the sensor 92(A) in the front-rear direction.

[0193] The pressing member 120(B) is disposed along the sensor 92(B) on the upstream side in the conveying direction relative to the sensor 92(B). The length of the pressing member 120(B) in the front-to-rear direction is approximately the same as the length of the sensor 92(B) in the front-to-rear direction. The pressing members 120(A) and 120(B) are disposed behind the sensors 93(B) and 94(B).

[0194] The pressing member 120(C) is disposed along the sensor 91(A) on the upstream side of the sensor 91(A) in the conveying direction. The length of the pressing member 120(C) in the front-rear direction is approximately the same as the length of the sensor 91(A) in the front-rear direction.

[0195] Pressing member 120(D) is disposed along sensor 91(B) on the upstream side in the conveying direction relative to sensor 91(B). The length of pressing member 120(D) in the front-to-rear direction is approximately the same as the length of sensor 91(B) in the front-to-rear direction. Pressing members 120(C) and 120(D) are disposed forward of sensors 93(A) and 94(A).

[0196] The upstream ends (i.e., right ends) of the presser members 120(A), 120(B), 120(C), and 120(D) in the conveying direction are attached to the conveying path surface 41A of the detection device main body 40, and the downstream portions (i.e., left portions) in the conveying direction are pressed against the conveying path surface 51A of the first unit 31 by their own elastic force. As a result, the presser members 120(A), 120(B), 120(C), and 120(D) press the medium P conveyed between themselves and the conveying path surface 51A against the conveying path surface 51A, thereby pressing the side edges of the medium P in a tensioned state. This supports the side edges of the medium P.

[0197] Then, sensors 91(A), 91(B), 92(A), and 92(B) detect the side edges of medium P, the side edges of which are supported by pressing members 120(A), 120(B), 120(C), and 120(D).

[0198] In this embodiment, the pressing members 120(A), 120(B), 120(C), and 120(D) have a length in the front-to-rear direction, but each of the pressing members 120(A), 120(B), 120(C), and 120(D) may be composed of multiple members divided into multiple parts in the front-to-rear direction.

[0199] (Control function of the control device 160 for the second detection device 30) Here, a control function of the control device 160 to control the operation of the second detection device 30 will be described. Figures 14 and 15 illustrate components of the control device 160 that perform the control function of controlling the operation of the second detection device 30. Specifically, as described above, the control device 160 has a processor 161, a memory 162, and a storage 163 (see Figure 14).

[0200] In the control device 160, the processor 161 executes the control program 163A to realize various functions. The following describes the functional configuration realized by the cooperation of the processor 161 as a hardware resource and the control program 163A as a software resource. Figure 15 is a block diagram showing the functional configuration of the processor 161.

[0201] As shown in FIG. 15, in the control device 160, the processor 161 executes a control program 163A to function as an acquisition unit 161A, a measurement unit 161B, and a control unit 161C.

[0202] The acquisition unit 161A acquires detection information obtained by the front and rear end detection unit 90 and the side end detection unit 98 detecting the ends of the medium P. The detection information includes position information indicating the positions of the ends of the medium P. Specifically, the position information is position information indicating the position in the transport direction for the front and rear ends of the medium P, and is position information indicating the position in the width direction of the medium P for the side ends of the medium P.

[0203] Specifically, the acquisition unit 161A, for example, detects the position of the edge of the medium P at the boundary between detection and non-detection of individual detection elements in the detection area using sensors 93 and 94, and acquires position information indicated by the coordinates (specifically, the number of pixels from the downstream end of the detection area in the conveying direction).

[0204] In addition, the acquisition unit 161A, for example, detects the position of the edge of the medium P at the boundary between detection and non-detection of each detection element in the detection area by the sensors 91 and 92, and acquires position information indicated by its coordinates (specifically, the number of pixels from the rear end of the detection area).

[0205] Based on the position information acquired by the acquisition unit 161A, the measurement unit 161B measures the transport direction length and width direction length of the medium P. Specifically, the measurement unit 161B measures the transport direction length of the medium P, for example, as follows.

[0206] For example, as shown in FIGS. 21 and 23, the measurement unit 161B determines the distance LB from the trailing edge of the medium P to the upstream edge (ie, the right edge) of the detection area of ​​the sensor 94 based on the position information.

[0207] Specifically, the distance LB is calculated using the following formula (1) based on the total number of pixels P1 (pixels / mm) of the detection elements of the sensor 94 and the number of pixels P2 (pixels) from the upstream end of the detection area of ​​the sensor 94 in the transport direction to the rear end of the medium P. Note that Figures 21 to 23 are conceptual diagrams, and each component (transport members 82, 83, sensors 91 to 94) is shown schematically.

[0208] Formula (1): LB=P2÷P1

[0209] Furthermore, the measurement unit 161B calculates the distance LC from the leading edge of the medium P to the upstream edge (ie, the right edge) of the detection area of ​​the sensor 93 based on the position information, for example.

[0210] Specifically, the distance LC is calculated using the following formula (2) based on the total number of pixels P3 (pixels / mm) of the detection elements of the sensor 93 and the number of pixels P4 (pixels) from the upstream end of the detection area of ​​the sensor 93 in the transport direction to the front end of the medium P.

[0211] Formula (2): LC=P4÷P3

[0212] Here, the distance LA from the upstream end (i.e., the right end) of sensor 94 to the upstream end (i.e., the right end) of sensor 93 is known. Then, the measurement unit 161B calculates the transport direction length L1 of the medium P using the following equation (3).

[0213] Equation (3): L1 = LA + LC - LB

[0214] Furthermore, the measuring unit 161B measures the width direction length of the medium P, for example, as follows.

[0215] For example, as shown in FIG. 23, the measurement unit 161B determines the distance WB from one side edge of the medium P (i.e., the edge toward the rear of the device) to the rear edge of the detection area of ​​the sensor 92 (i.e., the edge toward the rear of the device) based on the position information.

[0216] Specifically, the distance WB is calculated using the following equation (4) based on the total number of pixels P5 (pixels / mm) of the detection elements of the sensor 92 and the number of pixels P6 (pixels) from the rear end of the detection area of ​​the sensor 92 to one side end of the medium P.

[0217] Formula (4): WB=P6÷P5

[0218] Furthermore, the measurement unit 161B, for example, calculates the distance WC from the other side edge of the medium P (i.e., the edge on the front side of the device) to the rear edge of the detection area of ​​the sensor 91 (i.e., the edge on the rear side of the device) based on the position information.

[0219] Specifically, the distance WB is calculated using the following equation (5) based on the total number of pixels P7 (pixels / mm) of the detection elements of the sensor 91 and the number of pixels P8 (pixels) from the rear end of the detection area of ​​the sensor 91 to the other side end of the medium P.

[0220] Formula (5): WC=P8÷P7

[0221] Here, the distance WA from the rear end of sensor 92 to the rear end of sensor 91 is known. Then, the measurement unit 161B calculates the width direction length W1 of the medium P using the following equation (6).

[0222] Formula (6): W1=WA+WC-WB

[0223] Then, the measuring unit 161B measures the size (dimensions) of the medium P from the measured length of the medium P in the transport direction and the length of the medium P in the width direction.

[0224] In this embodiment, the conveying direction length L1 of the medium P at one end and the other end in the width direction is measured from the detection results of sensors 93(B) and 94(B) arranged in the left-right direction in the rear part of the second detection device 30 and the detection results of sensors 93(A) and 94(A) arranged in the left-right direction in the front part of the second detection device 30.

[0225] Here, when paper is used as the medium P, the transport direction length L1 may differ between one end portion and the other end portion of the medium P in the width direction due to cutting error, but it is possible to measure the cutting error by measuring the transport direction length L1 between the one end portion and the other end portion of the medium P in the width direction. Note that, for example, any one of the average value, minimum value, and maximum value of the transport direction length L1 between the one end portion and the other end portion of the medium P in the width direction can be set as the transport direction length of the medium P.

[0226] In addition, in this embodiment, the widthwise length W1 of the medium P at the downstream and upstream portions in the transport direction is measured from the detection results of sensors 91(A) and 92(A) arranged along the front-to-back direction in the left portion of the second detection device 30 and the detection results of sensors 91(B) and 92(B) arranged along the front-to-back direction in the right portion of the second detection device 30.

[0227] Here, when paper is used as the medium P, the width direction length W1 may differ between the downstream and upstream portions of the medium P in the transport direction due to cutting errors, but it is possible to measure the cutting error by measuring the width direction length W1 of the downstream and upstream portions of the medium P in the transport direction. Note that, for example, the width direction length of the medium P can be determined as any one of the average value, minimum value, and maximum value of the width direction length W1 of the downstream and upstream portions of the medium P in the transport direction.

[0228] Furthermore, in this embodiment, for example, skew (i.e., tilt) of medium P may be detected from the deviation in detection position between sensors 91(A), 92(A), 93(A), and 94(A) and sensors 91(B), 92(B), 93(B), and 94(B). The amount of tilt of medium P may be corrected to determine the length of medium P in the transport direction and the length of medium P in the width direction.

[0229] The control unit 161C performs image adjustment of the image formed on the medium P whose edge has been detected, based on the size (dimensions) of the medium P measured by the measurement unit 161B. That is, after the second detection device 30 detects the edge of the medium P, the control unit 161C performs image adjustment of the back-side image formed on the detected medium P, based on the size (dimensions) of the medium P measured by the measurement unit 161B. For example, when the size of the medium P measured by the measurement unit 161B is smaller than the size specified as the size of the medium P on which the image is to be formed, the control unit 161C controls the image forming unit 14 to reduce and form the back-side image.

[0230] Although the control device 160 is disposed in the image forming apparatus 10, this is not limitative. For example, the control device 160 may be disposed in the second detection device 30 or another device disposed outside the image forming apparatus 10, and the location of the control device 160 is not limited.

[0231] (Modification to the configuration for pulling the medium P) In the present embodiment, in the transport path 80B, the transport members 81, 82, and 83 that transport the medium P in the first transport direction and stop the transport pull the medium P in the pulling direction, but this is not limited to this. For example, the transport members 81, 82, and 83 may transport and stop the transport of the medium P, and a separately provided pulling means may pull the medium P. Examples of the pulling means include transport members such as transport rolls and transport belts, and a means that pulls the medium P using suction force.

[0232] Furthermore, in this embodiment, after the transport member 83 stops transporting the medium P, the transport members 81 and 82 stop transporting the medium P, and the transport members 81, 82, and 83 pull the medium P in the pulling direction, but this is not limited to this. For example, the transport members 81, 82, and 83 may simultaneously stop transporting the medium P, and then at least one of the transport members 81, 82, and 83 may operate to pull the medium. Note that when the transport members 81 and 82 operate, the drive rolls 84 and 85 rotate forward, and when the transport member 83 operates, the drive roll 86 rotates reversely.

[0233] (Modifications of the upstream transport section 80X and the downstream transport section 80Y) In the present embodiment, the downstream transport unit 80Y includes the transport member 81 and the transport member 82 disposed upstream of the transport member 81 in the transport direction, but is not limited to this. For example, the downstream transport unit 80Y may be configured to include only a transport unit such as a single transport member. Specifically, the downstream transport unit 80Y may be configured to include only the transport member 82, for example. In this configuration, media P of all sizes, including the minimum and maximum sizes, are pulled by the transport members 82 and 83.

[0234] In this way, in this embodiment, the minimum size medium P and the maximum size medium P may be pulled by the same transport unit such as the same transport member. Furthermore, the downstream transport unit 80Y may be configured to have three or more transport units such as the same transport members.

[0235] Furthermore, in this embodiment, the upstream transport unit 80X has only the transport member 83, but it may have transport units such as multiple transport members. In this case, for example, it is possible for the downstream transport unit 80Y to have a single transport unit, and the upstream transport unit 80X to have a first transport unit and a second transport unit located upstream of the first transport unit in the transport direction. In this configuration, for example, instead of the rear end sensor 99, a front end sensor can be provided as a detector that detects the leading end of the medium P, and the medium P can be stopped based on the timing when the leading end sensor detects the leading end of the medium P.

[0236] Furthermore, by stopping the medium P based on the timing when the front end sensor detects the front end of the medium P, the downstream conveying section 80Y can stop the conveying of the medium P so that the amount by which the front end of the medium P protrudes downstream in the conveying direction from the downstream conveying section 80Y is approximately the same regardless of the length of the medium P in the conveying direction.

[0237] Furthermore, in a modified example in which the second detection device 30 is positioned downstream in the conveying direction relative to the conveying path 80A and upstream in the conveying direction relative to the transfer position TA, the conveying members 81, 82, and 83 can re-convey the medium P from the end side (i.e., the downstream side in the conveying direction) that has approximately the same protrusion amount.

[0238] (Change in pulling force by conveying members 81, 82, 83) The tensile force of the conveying members 81, 82, and 83 may be changed depending on the characteristics of the medium P. Specifically, the tensile force of the conveying members 81, 82, and 83 may be changed depending on the type of the medium P. The types of the medium P include types related to thickness, such as thin paper, plain paper, and thick paper, and types related to whether or not the medium is coated, such as coated paper and uncoated paper. The characteristics of the medium P include the type, stiffness, thickness, basis weight, size, weight, temperature, and the like of the medium P.

[0239] Specifically, the conveying members 81, 82, and 83 are configured to apply, for example, a first tensile force to a first type of medium P, and a second tensile force stronger than the first tensile force to a second type of medium having higher rigidity than the first type of medium P.

[0240] The tensile force is changed by changing the second elapsed time (i.e., the time difference) from when the conveying member 83 stops rotating until the conveying members 81 and 82 stop rotating. That is, by lengthening the second elapsed time, the tensile force is increased.

[0241] In this configuration in which the tensile force is changed depending on the type of medium P, multiple types of medium P are transported along transport path 80B. Along this transport path 80B, second detection device 30 (specifically, front and rear end detection unit 90) detects the front and rear ends of multiple types of medium P when transport is stopped and the medium P is in a tensioned state. This second detection device 30 changes the tensile force depending on the type of medium P. Then, image forming unit 14 forms images on multiple types of medium P based on the detection results of second detection device 30.

[0242] In a configuration in which the tensile force of the conveying members 81, 82, and 83 is changed depending on the characteristics of the medium P, wrinkles in the medium P are suppressed compared to when the tensile force of the conveying members 81, 82, and 83 is constant.

[0243] Furthermore, in this example, the second detection device 30 changes the tensile force depending on the type of medium P, so that appropriate image formation can be performed for the type of medium P, compared to a device that forms images based on the results of detecting the front and rear ends of multiple types of media P while pulling multiple types of media P with a constant tensile force.

[0244] (Modification of the conveying section 80) In the present embodiment, the connectors 743, 753, 763, the drive sources 777, 778, and the control device 160, which are connected to the connectors 843, 853, 863 of the drive rolls 84, 85, 86, are provided in the image forming apparatus main body 11. However, the present invention is not limited to this. The connectors 743, 753, 763, the drive sources 777, 778, and the control device 160 may be provided in the second detection device 30.

[0245] In the present embodiment, the transporting members 81 and 82 are configured to be rotated by a common drive source 777, but this is not limiting. For example, the transporting members 81 and 82 may be configured to be rotated by separate drive sources.

[0246] Furthermore, in the present embodiment, the transport member 83 stops transport of the medium P so that the amount by which the rear end of the medium P protrudes from the transport member 83 toward the upstream side in the transport direction is substantially the same regardless of the length of the medium P in the transport direction, but this is not limited to this. For example, the amount by which the rear end of the medium P protrudes from the transport member 83 toward the upstream side in the transport direction may be configured to vary depending on the medium P.

[0247] In this embodiment, drive rolls 84, 85, and 86 are used as the rotating members, but this is not limited thereto. For example, rolls, rollers, belts, wheels, etc. may be used alone or in combination as the rotating members. When a belt is used as the rotating member, the belt is wound around multiple rolls and rotates by receiving driving force from the rolls. Furthermore, the rotating members may be members that are not driven to rotate, as long as they rotate.

[0248] In this embodiment, the driven members are the driven rolls 87, 88, and 89, but are not limited to this. The driven members may be, for example, rollers, belts, wheels, etc., as long as they are members that are driven by the rotating member.

[0249] In addition, in the present embodiment, the drive rolls 84, 85, and 86 as rotating members are arranged in the detection device main body 40, and the driven rolls 87, 88, and 89 as driven members are arranged in the first unit 31 and the second unit 32, which are units arranged above the detection device main body 40. However, this is not limited to this. For example, a configuration may be possible in which driven members such as the driven rolls 87, 88, and 89 are arranged in the detection device main body 40, and rotating members such as the drive rolls 84, 85, and 86 are arranged in the first unit 31 and the second unit 32.

[0250] Furthermore, in the present embodiment, the driven rolls 87, 88, 89 and roll portions 842, 852, 862 are arranged to sandwich the sensors 93, 94 in the front-to-rear direction (i.e., the width direction of the medium P) as appropriate when viewed in a direction perpendicular to the image forming surface of the medium P, but this is not limited to this. For example, the driven rolls 87, 88, 89 and roll portions 842, 852, 862 may be arranged to sandwich the sensors 93, 94 in the transport direction as appropriate when viewed in a direction perpendicular to the image forming surface of the medium P. Furthermore, the driven rolls 87, 88, 89 and roll portions 842, 852, 862 may be arranged in positions that do not sandwich the sensors 93, 94.

[0251] In this embodiment, the first conveying direction is the leftward direction, and the second conveying direction is the rightward direction, but this is not limiting. The first conveying direction and the second conveying direction may be, for example, forward, backward, upward, downward, or any other direction.

[0252] Although the second transport direction is the opposite direction to the first transport direction in the above embodiment, it is not limited to this. The second transport direction may be, for example, a direction intersecting the first transport direction, or may be any direction different from the first transport direction. When the second transport direction is intersecting the first transport direction, the second detection device 30 may be configured to invert the medium P by a Möbius turn method. The Möbius turn method is a method of inverting the medium P by transporting the medium P by turning it back and forth multiple times so that the orientation of the medium P changes by 90 degrees each time, as viewed in a direction perpendicular to the image formation surface of the medium P. Furthermore, the second transport direction may be, for example, the same direction as the first transport direction.

[0253] (Modification of the pressing member 110) In the present embodiment, the presser member 110 is disposed so as to sandwich the sensor 93 in the front-to-rear direction as appropriate when viewed in a direction perpendicular to the image forming surface of the medium P, but this is not limited to this. The presser member 110 may be disposed so as to sandwich the sensor 93 in the conveyance direction as appropriate when viewed in a direction perpendicular to the image forming surface of the medium P. The presser member 110 may also be disposed in a position that does not sandwich the sensor 93. For example, the presser member 110 may be disposed in a position facing the sensor 93, or in a position shifted from the facing position, as long as the presser member 110 does not affect detection by the sensor 93.

[0254] Furthermore, in this embodiment, the presser member 110 presses down the downstream end of the medium P detected by the sensor 93, but instead of or in addition to this, it may be configured to press down one side end, the other side end, and the downstream end of the medium P detected by each of the sensors 91, 92, and 94. Note that the presser member 110 only needs to press down the end of the medium P that is the detection target, so in a configuration where there is an end that is not the detection target, the presser member 110 does not need to be arranged for that end.

[0255] Furthermore, the pressing member 110 is not limited to a plate-shaped elastic member such as a resin film. The pressing member 110 may be any member that supports the detection device main body 40 at a position above the transport path surface 41A, and may be a protruding part such as a rib, a driving, driven, or non-rotating roll, a belt, a roller, a wheel, or the like. Furthermore, the member that supports the medium P may be a member that supports the medium P by blowing or sucking a gas such as air.

[0256] (Modification of the pressing member 120) In the present embodiment, each of the presser members 120(A), 120(B), 120(C), and 120(D) is disposed along each of the sensors 92(A), 92(B), 91(A), and 91(B) on the upstream side of each of the sensors 92(A), 92(B), 91(A), and 91(B) in the conveying direction, but this is not limiting. For example, each of the presser members 120(A), 120(B), 120(C), and 120(D) may be disposed downstream of each of the sensors 92(A), 92(B), 91(A), and 91(B) in the conveying direction.

[0257] Furthermore, an example of the support unit is not limited to the presser member 120. An example of the support unit may be anything that supports the medium P whose side edge is detected by the side edge detection unit 98, such as a protruding part such as a rib, a driving, driven, or non-rotating roll, a belt, a roller, or a wheel. Another example of the support unit may be something that supports the medium P by blowing or sucking gas such as air.

[0258] Furthermore, this embodiment may be configured without the presser member 120 that supports the medium P whose side edge is detected by the side edge detector 98.

[0259] (Modification of the opening / closing unit 70) In this embodiment, the opening / closing unit 70 is disposed between the sensors 91(A), 92(A) and the sensors 91(A), 92(B) at a position where the sensors 91 to 94 are not present, but this is not limiting. For example, the opening / closing unit 70 may be disposed at a position where the sensors 93 and 94 are not present, and may be opened and closed together with the sensors 91 and 92. In this case, it is necessary to configure the opening / closing unit 70 so that the positioning accuracy of the opening / closing unit 70 does not affect the detection accuracy of the sensors 91 and 92.

[0260] Further, the second detection device 30 may not have the opening / closing unit 70, and may have a configuration in which the opening 77 that opens the transport path 80A (see FIG. 1) in the transport unit 80 cannot be opened or closed.

[0261] (Modifications of the front and rear edge detectors 90 and the side edge detectors 98) In this embodiment, the sensors 91 to 94 are reflective optical sensors, but are not limited to this. For example, the sensors 91 to 94 may be transmissive optical sensors. The sensors 91 to 94 may be detectors that detect the edge of the medium P by contact with the edge of the medium P, and various detectors may be used. An example of a detector that detects the edge of the medium P by contact with the edge of the medium P is a detector that uses a contact member (e.g., a guide member) that contacts the side edge of the medium P. The sensors 91 to 94 may be cameras that capture images of the medium P and detect the edge of the medium P. Even when the length of the medium P is measured from an image captured by a camera, the length is the distance between the edges of the medium P, and therefore the edge of the medium P can be said to be detected.

[0262] In this embodiment, each of the sensors 91 to 94 is arranged so as to intersect with the end of the medium P in a tensioned state in the longitudinal direction when viewed in a direction perpendicular to the image forming surface of the medium P, but this is not limited to this. For example, each of the sensors 91 to 94 may be arranged so as to intersect with the end of the medium P in the lateral direction. Furthermore, each of the sensors 91 to 94 may be a sensor that does not have a longitudinal direction (for example, a square sensor when viewed in a direction perpendicular to the image forming surface of the medium P).

[0263] In addition, in this embodiment, the front and rear edge detection unit 90 and the side edge detection unit 98 detect one edge of the medium P using multiple sensors, but this is not limited to this. For example, a configuration may be provided in which only one sensor is provided to detect one edge of the medium P.

[0264] In addition, in the present embodiment, the sensors 91 to 94 are provided in the first unit 31 and the second unit 32, but this is not limiting. For example, the sensors 91 and 93 may be provided in the detection device main body 40, and the sensors 92 and 94 may be provided in the first unit 31 and the second unit 32.

[0265] Furthermore, in this embodiment, the front and rear end detectors 90 and the side end detectors 98 are provided, but it is sufficient if at least the front and rear end detectors 90 are provided.

[0266] The front and rear end detection unit 90 may be configured to detect the front and rear ends of the tensioned medium P for the largest size medium P, which has the longest length in the transport direction, and not detect the front and rear ends of the tensioned medium P for the smallest size medium P, which has the smallest length in the transport direction. In this configuration, for example, the front and rear end detection unit 90 detects the front and rear ends of the tensioned medium P for media P of sizes other than the smallest size, including the largest size medium P, and does not detect the front and rear ends of the tensioned medium P for the smallest size medium P.

[0267] Furthermore, in this configuration, for example, the size of the medium P is measured upstream in the conveying direction relative to the second detection device 30, and based on the measurement results, the front and rear end detection unit 90 determines whether or not to perform the detection operation of the front and rear ends of the medium P.

[0268] In this configuration, for the smallest size medium P, which has the smallest length in the conveying direction, the front and rear end detection unit 90 does not detect the front and rear ends of the medium P, so the number of times the front and rear end detection unit 90 detects the front and rear ends of the medium P is reduced compared to when the front and rear end detection unit 90 always detects the front and rear ends of the medium P regardless of the length of the medium P in the conveying direction.

[0269] (First detection device 500) 1 has the function of detecting the leading and trailing edges of the medium P before it is heated, as described above. Specifically, the first detection device 500 detects the leading and trailing edges of the medium P while it is being transported and before it passes through the heating unit 19 during an image forming operation. The specific configuration of the first detection device 500 will be described below.

[0270] FIG. 24 is a side cross-sectional view showing the configuration of the first detection device 500. FIG. 25 is a plan view showing the configuration of the first detection device 500. Note that in FIGS. 24 to 26 and 30 to 34, the left and right sides of the device are shown inverted relative to FIGS. 1 to 3. That is, in FIGS. 24 to 26 and 30 to 34, the left and right sides of the device are shown in the opposite direction to the left and right sides on the paper. In addition, in FIGS. 24 to 26, the conveying direction is indicated by an arrow H as appropriate. Note that in FIG. 1, the first detection device 500 is shown in a simplified form.

[0271] 24, the first detection device 500 includes a first support 510, a second support 520, a transport mechanism 503, detection units 610 and 620, and a front end sensor 627. The configuration of each unit of the first detection device 500 will be described below.

[0272] (First support 510) The first support 510 shown in FIG. 24 has a function of supporting a part of the transport mechanism 503 (specifically, drive rolls 531, 541, 551, 561, and 571, which will be described later).

[0273] 24, the first support body 510 constitutes the lower part of the first detection device 500. As one example, the first support body 510 is formed in a flat shape that is thin in the up-down direction and wide in the front-rear and left-right directions.

[0274] The first support 510 has a guide plate 514 that guides the medium P. The guide plate 514 faces the lower surface of the medium P and guides the medium P transported by the transport mechanism 503 downstream in the transport direction.

[0275] (Second support 520) The second support 520 shown in FIGS. 24 and 25 has a function of supporting other parts of the transport mechanism 503 (specifically, driven rolls 532, 542, 552, 562, and 572, which will be described later).

[0276] 24, the second support body 520 constitutes an upper portion of the first detection device 500. As one example, the second support body 520 is formed in a flat shape that is thin in the up-down direction and widens in the front-rear and left-right directions.

[0277] The second support 520 has a guide plate 524 that guides the medium P. The guide plate 524 faces the upper surface of the medium P and guides the medium P transported by the transport mechanism 503 downstream in the transport direction.

[0278] (Transport mechanism 503) The transport mechanism 503 shown in FIGS. 24 and 25 is a mechanism that transports the medium P in the first detection device 500. As shown in FIGS. 24 and 25, the transport mechanism 503 has transport rolls 530, 540, 550, 560, and 570. The transport rolls 530, 540, 550, 560, and 570 are arranged in this order toward the downstream side in the transport direction. Each of the transport rolls 530, 540, 550, 560, and 570 has the function of transporting the medium P and is configured as a pair of rolls as shown in FIG. 24. Specifically, the transport rolls 530, 540, 550, 560, and 570 each have a drive roll 531, 541, 551, 561, and 571, and a driven roll 532, 542, 552, 562, and 572.

[0279] The driving rolls 531, 541, 551, 561, and 571 are disposed below the driven rolls 532, 542, 552, 562, and 572, and are driven to rotate to apply a conveying force to the medium P.

[0280] The driven rolls 532, 542, 552, 562, and 572 are disposed above the drive rolls 531, 541, 551, 561, and 571, and rotate following the drive rolls 531, 541, 551, 561, and 571.

[0281] The driven rolls 532, 542, 552, 562, and 572 are supported by the second support 520 so as to be movable between a clamping position (position shown by solid lines in FIG. 24) where they clamp the medium P with the drive rolls 531, 541, 551, 561, and 571, and a separated position (position shown by two-dot chain lines in FIG. 24) where they are separated from the medium P. The transport rolls 530, 540, 550, 560, and 570 transport the medium P with the driven rolls 532, 542, 552, 562, and 572 positioned at the clamping position.

[0282] The transport roll 550 is an example of a transport unit, and has a function of transporting the medium P to the transport roll 560.

[0283] The transport roll 560 is provided downstream in the transport direction relative to the transport roll 550. This transport roll 560 is an example of an abutting section, and is an abutting roll that abuts against the front end of the medium P. Hereinafter, the transport roll 560 may also be referred to as the abutting roll 560. The abutting roll 560 has the function of correcting the inclination (i.e., skew) of the medium P by abutting against the front end of the medium P transported by the transport roll 550.

[0284] The transport roll 570 is provided downstream in the transport direction relative to the transport roll 560. This transport roll 570 is a correction roll that corrects misalignment of the medium P in the width direction. Hereinafter, the transport roll 570 may be referred to as the correction roll 570. The correction roll 570 moves along the width direction while sandwiching the medium P based on the detection result of the detection unit 620, thereby correcting misalignment of the medium P in the width direction.

[0285] The transport rolls 530 and 540 are provided upstream in the transport direction relative to the transport roll 550. The transport rolls 530 and 540 are an example of an upstream transport section, and transport the medium P toward the transport roll 550.

[0286] In this embodiment, the transport roll 550 transports the medium P at a constant speed and at a transport speed slower than the transport speed on the upstream side in the transport direction relative to the leading end sensor 612 (described later). Specifically, the transport roll 550 transports the medium P at a constant speed and at a transport speed slower than the transport speed when the medium P is transported upstream in the transport direction relative to the transport roll 550.

[0287] Although the transport mechanism 503 includes the transport rolls 530, 540, 550, 560, and 570, the present invention is not limited to this. For example, a transport member such as a transport belt may be included instead of the transport rolls 530, 540, 550, 560, and 570. That is, an example of the transport unit and an example of the upstream transport unit are not limited to the transport rolls 530, 540, and 550, and a transport member such as a transport belt may be used. Furthermore, an example of the abutting unit is not limited to the abutting roll 560, and may be a transport member such as a transport belt, as long as it abuts against the leading edge of the medium P transported from the upstream side of the transport roll 550 in the transport direction.

[0288] (Detection unit 610) 24 and 25 has a function of detecting the leading end and trailing end of the medium P being transported. As shown in FIGS. 24 and 25, the detection unit 610 has a leading end sensor 612 and a trailing end sensor 614.

[0289] The leading edge sensor 612 detects the leading edge of the medium P being transported. Specifically, the leading edge sensor 612 is a non-contact sensor that detects the leading edge of the medium P without coming into contact with the medium P. Even more specifically, the leading edge sensor 612 is an optical sensor that uses light irradiated toward the medium P. Even more specifically, the leading edge sensor 612 is a reflective optical sensor that detects the leading edge of the medium P by detecting reflected light of light irradiated onto the medium P. Note that a transmissive optical sensor may also be used as the leading edge sensor 612.

[0290] The trailing edge sensor 614 detects the trailing edge of the medium P being transported. The leading edge sensor 612 and the trailing edge sensor 614 are arranged so as to overlap when viewed in the transport direction, as shown in Fig. 25. Specifically, the leading edge sensor 612 and the trailing edge sensor 614 are arranged side by side in the transport direction (specifically, the left-right direction).

[0291] 24 and 25, in this embodiment, the detection unit 610 is provided upstream of the abutting roll 560 in the transport direction. Specifically, the leading end sensor 612 is provided upstream of the abutting roll 560 in the transport direction and downstream of the transport roll 550 in the transport direction. The trailing end sensor 614 is provided upstream of the transport roll 530 in the transport direction.

[0292] The trailing edge sensor 614 is a non-contact sensor that detects the trailing edge of the medium P without coming into contact with the medium P. More specifically, the trailing edge sensor 614 is an optical sensor that uses light irradiated toward the medium P. More specifically, as shown in FIG. 24, the trailing edge sensor 614 has multiple detection elements 616 (specifically, light-emitting elements and light-receiving elements) arranged along the transport direction and is configured as a line sensor that is elongated in the transport direction. More specifically, as an example, the trailing edge sensor 614 is configured as a contact image sensor (CIS). Note that a line sensor other than a contact image sensor may also be used as the trailing edge sensor 614.

[0293] The rear end sensor 614 has a detection area 614R that detects the rear end of the medium P, from the detection element 616(X) located at the most upstream side in the transport direction to the detection element 616(Y) located at the most downstream side in the transport direction.

[0294] The trailing end sensor 614 detects the position of the trailing end of the medium P at the boundary between detection and non-detection of each detection element 616 in the detection area 614R, and position information indicated by its coordinates (specifically, the number of pixels from the downstream end of the detection area 614R in the conveying direction) is sent to, for example, the control device 160.

[0295] 24, in the detection unit 610, the distance D1 between the detection element 616(X), which is located on the most upstream side of the trailing edge sensor 614 in the transport direction, and the leading edge sensor 612 is shorter than the length D2 in the transport direction of the maximum-sized medium P. In other words, when the leading edge of the maximum-sized medium P is detected by the leading edge sensor 612, the trailing edge of the medium P protrudes from the detection area 614R toward the upstream side in the transport direction. Note that the detection area 614R is positioned so that the leading edge of the maximum-sized medium P is downstream in the transport direction from the leading edge sensor 612 and the trailing edge of the medium P is located within the range of the detection area 614R before it reaches the abutment roll 560.

[0296] In this embodiment, as shown by the symbols (A) and (B) in Fig. 25, two sets of the front end sensor 612 and the rear end sensor 614 are arranged. Specifically, the front end sensor 612 and the rear end sensor 614 are arranged in a front portion and a rear portion of the first detection device 500.

[0297] In the detection unit 610, as shown in FIG. 26, the front end sensor 612 and the rear end sensor 614 each detect the front end and rear end of the medium P while it is being transported by the transport roll 550, with the driven rolls 532 and 542 of the transport rolls 530 and 540 positioned in the separated position.

[0298] Although the detection unit 610 has the above configuration, it is not limited to this configuration. The detection unit 610 may, for example, be configured with a pair of the leading edge sensor 612 and the trailing edge sensor 614. The detection unit 610 may also be configured with the leading edge sensor 612 and the trailing edge sensor 614 offset from each other in the width direction. The detection unit 610 may be configured to detect the leading edge and trailing edge of the medium P being transported.

[0299] (Front end sensor 627) 24 and 25 has a function of detecting the leading end of the medium P being transported and is detected by the detection unit 610. Specifically, the leading end sensor 627 is provided downstream of the correction roll 570 in the transport direction.

[0300] The front end sensor 627 detects the front end of the medium P being transported by the correction roll 570 with the transport rolls 530, 540, 550 and the driven rolls 532, 542, 552, 562 of the abutting roll 560 positioned at the separated positions.

[0301] Specifically, the leading edge sensor 627 is a non-contact sensor that detects the leading edge of the medium P without coming into contact with the medium P. Even more specifically, the leading edge sensor 627 is an optical sensor that uses light irradiated toward the medium P. Even more specifically, the leading edge sensor 627 is a reflective optical sensor that detects the edge of the medium P by detecting reflected light of light irradiated onto the medium P. Note that a transmissive optical sensor may also be used as the leading edge sensor 627.

[0302] (Detection unit 620) 24 and 25 has a function of detecting both widthwise ends (i.e., a pair of side ends) of the medium P being transported and detected by the detection unit 610. The detection unit 620 has a pair of side end sensors 628, as shown in FIG.

[0303] The pair of side edge sensors 628 are arranged at opposing positions facing one end and the other end of the width of the medium P (see FIGS. 33 and 34). That is, the detection unit 620 is divided in the width direction and arranged at opposing positions facing one end and the other end of the width of the medium P.

[0304] In this embodiment, as shown in Figure 25, the pair of side edge sensors 628 is composed of a side edge sensor 628(A) on the front side of the device and a side edge sensor 628(B) on the rear side of the device, and detects each of the pair of side edges of the medium P being transported. The pair of side edge sensors 628 are arranged so that they overlap when viewed in the width direction. Specifically, the pair of side edge sensors 628 are arranged side by side in the width direction (specifically, the front-to-rear direction).

[0305] In this embodiment, the detection unit 620 is provided downstream in the transport direction from the abutting roll 560. Specifically, the detection unit 620 is provided downstream in the transport direction from the front end sensor 627.

[0306] The pair of side edge sensors 628 are non-contact sensors that detect the pair of side edges of the medium P without coming into contact with the medium P. More specifically, the pair of side edge sensors 628 are optical sensors that use light irradiated toward the medium P. More specifically, as shown in FIG. 25 , the pair of side edge sensors 628 are configured as line sensors that are elongated in the width direction and have multiple detection elements 629 (specifically, light-emitting elements and light-receiving elements) arranged along the width direction. More specifically, the pair of side edge sensors 628 are configured as contact image sensors (CIS), as an example. Note that line sensors other than contact image sensors may also be used as the pair of side edge sensors 628.

[0307] The pair of side edge sensors 628 have a detection region 628R that detects the side edge of the medium P, from the detection element 629(X) located on one end side in the width direction to the detection element 629(Y) located on the other end side in the width direction.

[0308] The pair of side edge sensors 628 detect the position of the side edge of the medium P at the boundary between detection and non-detection of each detection element 629 in the detection area 628R, and position information indicated by the coordinates (specifically, the number of pixels from the front end of the detection area 628R) is sent to, for example, the control device 160.

[0309] In the detection section 620, a pair of side edge sensors 628 detect each of a pair of side edges of the medium P being transported by the correction roll 570 with the transport rolls 530, 540, 550 and the driven rolls 532, 542, 552, 562 of the abutment roll 560 positioned in a spaced apart position.

[0310] Although the detection unit 620 has the above configuration, it is not limited to this configuration. The detection unit 620 may, for example, be configured to have multiple pairs of side edge sensors 628 arranged. Furthermore, the detection unit 620 may be configured to have pairs of side edge sensors 628 arranged offset in the transport direction. Furthermore, although the detection unit 620 has been arranged downstream in the transport direction relative to the detection unit 610, it may also be configured to be arranged upstream in the transport direction relative to the detection unit 610. The detection unit 620 may be configured to detect both ends of the medium P detected by the detection unit 610 in a direction perpendicular to the transport direction of the medium P being transported.

[0311] (Control function of the control device 160 for the first detection device 500) Here, a control function of the control device 160 to control the operation of the first detection device 500 will be described. Figures 27 and 28 illustrate components of the control device 160 that perform the control function of controlling the operation of the first detection device 500. Specifically, as described above, the control device 160 has the processor 161, memory 162, and storage 163 (see Figure 27).

[0312] In the control device 160, the processor 161 executes the control program 163A to realize various functions. The following describes the functional configuration realized by the cooperation of the processor 161 as a hardware resource and the control program 163A as a software resource. Figure 28 is a block diagram showing the functional configuration of the processor 161.

[0313] As shown in FIG. 28, in the control device 160, the processor 161 executes a control program 163A to function as an acquisition unit 161A, a measurement unit 161B, and a control unit 161C.

[0314] The control unit 161C controls the transport mechanism 503, the detection units 610 and 620, and the front end sensor 627 to perform the detection operation described below.

[0315] 29, the transport mechanism 503 transports the medium P at a predetermined transport speed 1 using, for example, transport rolls 530 and 540, and transports the medium P while decelerating to a transport speed 2 that is slower than the transport speed 1. In the transport mechanism 503, for example, the transport roll 550 receives the medium P from the transport rolls 530 and 540 and transports the medium P at a constant transport speed 2. When the transport roll 550 transports the medium P, the driven rolls 532 and 542 of the transport rolls 530 and 540 move to the separated positions. In other words, the transport roll 550 alone transports the medium P toward the abutment roll 560 at a constant transport speed 2 (see FIG. 26).

[0316] When the leading end sensor 612 of the detection unit 610 detects the leading end of the medium P being transported by the transport rolls 550, the trailing end sensor 614 detects the trailing end of the medium P after a predetermined time (hereinafter referred to as elapsed time X) has elapsed. At this time, the leading end of the medium P is located upstream of the abutting rolls 560 in the transport direction (see FIG. 26). In other words, the trailing end is detected before the leading end of the medium P abuts against the abutting rolls 560. Furthermore, the leading end sensor 612 and the trailing end sensor 614 each detect the leading end and the trailing end of the medium P when the transport rolls 550 are transporting it alone.

[0317] In the case of a maximum-sized medium P, when the leading end is detected by the leading end sensor 612, the trailing end is located upstream in the transport direction relative to the detection area 614R of the trailing end sensor 614 (see FIG. 25), and after a predetermined elapsed time X has elapsed, the trailing end is located within the detection area 614R of the trailing end sensor 614 (see FIG. 26). In the case of a minimum-sized medium P, both when the leading end is detected by the leading end sensor 612 and after the predetermined elapsed time X has elapsed, the trailing end is located within the detection area 614R of the trailing end sensor 614.

[0318] Furthermore, the transport roll 550 transports the medium P for a predetermined time after the medium P hits the abutting roll 560, and stops transporting after the front end of the medium P hits the abutting roll 560 from one end to the other in the width direction.

[0319] Thereafter, the abutting roll 560 transports the medium P. When the abutting roll 560 transports the medium P, the transport rolls 530, 540, and 550 move the driven rolls 532, 542, and 552 to the separated positions. In other words, the abutting roll 560 transports the medium P toward the correction roll 570 by itself.

[0320] Thereafter, the correction roll 570 transports the medium P. When the correction roll 570 transports the medium P, the transport rolls 530, 540, 550 and the abutting roll 560 move the driven rolls 532, 542, 552, 562 to the separated positions. In other words, the correction roll 570 transports the medium P solely downstream in the transport direction.

[0321] When the leading edge sensor 627 of the detection unit 620 detects the leading edge of the medium P being transported by the correction roll 570, after a predetermined time (hereinafter referred to as elapsed time Y) has elapsed, the pair of side edge sensors 628 detect the pair of side edges of the medium P. The leading edge sensor 627 and the pair of side edge sensors 628 detect the pair of side edges of the medium P when it is being transported by the correction roll 570 alone.

[0322] The correction roll 570 corrects misalignment of the medium P in the width direction by moving along the width direction based on the amount of misalignment detected by the detection unit 620 (see below).

[0323] In addition, when the image forming unit 214 is used as the image forming unit, the abutting roll 560 resumes transporting the medium P so that the timing when the toner image formed on the transfer body 216 reaches the transfer position TA and the timing when the medium P reaches the transfer position TA are synchronized.

[0324] The acquisition unit 161A acquires detection information obtained by the detection units 610, 620 detecting the leading end, trailing end, and pair of side ends of the medium P. The detection information for the trailing end and pair of side ends includes position information indicating the positions of the trailing end and pair of side ends of the medium P. Specifically, the position information is position information indicating the position in the transport direction for the trailing end of the medium P, and is position information indicating the position in the width direction of the medium P for the side ends of the medium P.

[0325] Specifically, the acquisition unit 161A, for example, detects the position of the rear end of the medium P at the boundary between detection and non-detection of the individual detection elements 616 in the detection area 614R by the rear end sensor 614, and acquires position information indicated by its coordinates (specifically, the number of pixels from the downstream end of the detection area 614R in the transport direction).

[0326] In addition, the acquisition unit 161A, for example, detects the position of the side edge of the medium P at the boundary between detection and non-detection of each of the pair of side edge sensors 628 in the detection area 628R of the individual detection elements 629, and acquires position information indicated by the coordinates (specifically, the number of pixels from the front end of the detection area 628R).

[0327] The measuring unit 161B measures the length of the medium P in the transport direction based on the position information acquired by the acquiring unit 161A, for example, as follows.

[0328] For example, based on the position information, the measurement unit 161B determines the distance LA (see Figure 26) from the downstream end of the detection area 614R of the trailing end sensor 614 in the transport direction (i.e., the detection element 616(Y) arranged at the most downstream side in the transport direction) to the trailing end of the medium P.

[0329] Specifically, the distance LA is calculated using the following formula (1) based on the total number of pixels P1 (pixels / mm) of the detection element 616 of the trailing end sensor 614 and the number of pixels P2 (pixels) from the downstream end of the detection area 614R of the trailing end sensor 614 in the transport direction to the trailing end of the medium P.

[0330] Formula (1): LA = P2 ÷ P1

[0331] The distance LB (see FIG. 26) from the downstream end of the detection area 614R of the trailing end sensor 614 in the transport direction to the leading end sensor 612 is known. Furthermore, by multiplying the known transport speed 2 by the known elapsed time X, the distance LC (see FIG. 26) from the leading end sensor 612 to the leading end of the medium P is determined in advance as a known value. Then, the measurement unit 161B determines the length L1 of the medium P in the transport direction using the following equation (2):

[0332] Equation (2): L1 = LA + LB + LC

[0333] In this embodiment, as shown in Figure 30, the transport direction length L1 of one end portion and the other end portion of the width direction of the medium P is measured based on the detection results of two sets of leading end sensors 612(A)(B) and trailing end sensors 614(A)(B). Note that Figures 30 to 32 schematically show the two sets of leading end sensors 612(A)(B) and trailing end sensors 614(A)(B).

[0334] Here, when paper is used as the medium P, the conveying direction length L1 may differ between one end portion and the other end portion of the medium P in the width direction due to cutting error, as shown in Fig. 30, and it is possible to measure this cutting error. Note that the average, minimum, and maximum values ​​of the conveying direction length L1 between one end portion and the other end portion of the medium P in the width direction can be used as the conveying direction length of the medium P.

[0335] In this embodiment, as shown in Figure 31, it is possible to detect skew of the medium P from the difference in detection timing between the two pairs of front end sensors 612(A)(B). Here, if the medium P skews, an error may occur between the calculated transport direction length L1 and the true transport direction length Lm.

[0336] Therefore, to correct this error, the amount of skew can be calculated from the transport speed 2(v) of the medium P, the time difference Δt between the leading end sensors 612(A) and (B), and the distance X between the leading end sensors 612(A) and (B), as shown in the following equation (3), and correction can be performed to obtain the true paper length Lm.

[0337] Equation (3): Lm=(√((Δt÷v) 2 +X 2 )÷X)×L1

[0338] The measuring unit 161B measures the width direction length W1 of the medium P, for example, as follows, based on the position information acquired by the acquiring unit 161A.

[0339] For example, based on the position information, the measurement unit 161B determines the distance WA (see Figure 32) from the front end of the detection area 628R of the side edge sensor 628(A) (i.e., the detection element 629(Y) arranged on the front end side) to one side edge of the medium P (specifically, the side edge on the front side of the device).

[0340] Specifically, the distance WA is calculated using the following equation (4) based on the total number of pixels P3 (pixels / mm) of the detection element 629 of the side edge sensor 628(A) and the number of pixels P4 (pixels) from the front end of the detection area 628R of the side edge sensor 628(A) to one side end (specifically, the side end on the front side of the device).

[0341] Equation (4) WA = P4 ÷ P3

[0342] Furthermore, based on the position information, the measurement unit 161B determines the distance WB (see FIG. 32) from the front end of the detection area 628R of the side edge sensor 628(B) (i.e., the detection element 629(Y) arranged on the front end side) to the other side edge of the medium P (specifically, the side edge on the rear side of the device).

[0343] Specifically, the distance WB is calculated using the following equation (5) based on the total number of pixels P5 (pixels / mm) of the detection element 629 of the side edge sensor 628(B) and the number of pixels P6 (pixels) from the front end of the detection area 628R of the side edge sensor 628(B) to the other side end (specifically, the side end on the rear side of the device).

[0344] Formula (5) WB=P6÷P5

[0345] The distance WC from the front end of the detection area 614R of the side edge sensor 628(A) to the front end of the detection area 614R of the side edge sensor 628(B) is known. Then, the measurement unit 161B calculates the width direction length W1 of the medium P using the following equation (6).

[0346] Formula (6): W1=WC+WB-WA

[0347] Furthermore, the measurement unit 161B detects the amount of positional deviation in the width direction of the medium P based on the position information acquired by the acquisition unit 161A, for example, as follows.

[0348] Based on the position information, the measurement unit 161B, for example, determines the distance WA (see Figure 32) from the front end of the detection area 628R of the side edge sensor 628(A) (i.e., the detection element 629(Y) arranged on the front end side) to one side edge of the medium P (specifically, the side edge on the front side of the device), as described above.

[0349] Here, the distance WM (see Figure 32) from the front end of the detection area 628R of the side edge sensor 628(A) (i.e., the detection element 629(Y) arranged on the front end side) to one side edge of the medium P at the reference position of the medium P (specifically, the side edge on the front side of the device) is determined in advance as a known value.

[0350] The reference position of the medium P is a position in the width direction that is set in advance as a position where the medium P should be placed when the medium P is transported.

[0351] Then, the measurement unit 161B detects the amount of misalignment WN in the width direction of the medium P from the difference between the distance WM and the distance WA. In this way, the amount of misalignment WN in the width direction of the medium P is detected based on the detection result of one side edge sensor 628(A) of the detection unit 620.

[0352] The measurement unit 161B may detect the amount of misalignment in the width direction of the medium P based on the distance WB from the front end of the detection area 628R of the side edge sensor 628(B) (i.e., the detection element 629(Y) arranged on the front end side) to the other side edge of the medium P (specifically, the side edge on the rear side of the device). The measurement unit 161B may also detect the amount of misalignment in the width direction of the medium P based on the distance WA and the distance WB.

[0353] In this embodiment, a pair of side edge sensors 628 may detect a pair of side edges (see FIG. 33) on the upstream side in the transport direction of the medium P and a pair of side edges (see FIG. 34) on the downstream side in the transport direction of the medium P. From the detection results, the width direction length W1 of the upstream side in the transport direction and the downstream side in the transport direction of the medium P may be measured.

[0354] Specifically, for example, after an elapsed time Y has elapsed since the front end sensor 627 of the detection unit 620 detected the front end of the medium P being transported by the correction roll 570, a pair of side end sensors 628 detect a pair of side ends of the medium P, thereby detecting a pair of side ends in the upstream portion of the transport direction of the medium P, as shown in Figure 33.

[0355] In the example shown in Figure 33, the pair of side edges of the medium P are detected at a position where the front end of the medium P is transported from the front end sensor 627 a distance M1 calculated by multiplying the transport speed by the correction roll 570 by the elapsed time Y.

[0356] Furthermore, after an elapsed time Z, which is longer than the elapsed time Y, has elapsed since the front end sensor 627 of the detection unit 620 detected the front end of the medium P being transported by the correction roll 570, a pair of side end sensors 628 detects a pair of side ends of the medium P, thereby detecting a pair of side ends in the downstream portion of the medium P in the transport direction, as shown in Figure 34.

[0357] 34, the pair of side edges of the medium P are detected at a position where the leading edge of the medium P has been transported a distance M2, which is calculated by multiplying the transport speed of the correction roll 570 by the elapsed time Z, from the leading edge sensor 627. Distance M2 is longer than distance M1.

[0358] Here, when paper is used as the medium P, the width direction length W1 may differ between the upstream and downstream portions of the medium P in the transport direction due to cutting errors, and it is possible to measure this cutting error. Note that the average, minimum, and maximum values ​​of the width direction length W1 of the upstream and downstream portions of the medium P in the transport direction can be used as the width direction length of the medium P.

[0359] Furthermore, in this embodiment, the pair of side edge sensors 628 detect a pair of side edges (see Figure 33) on the upstream side of the transport direction of the medium P and a pair of side edges (see Figure 34) on the downstream side of the transport direction of the medium P, and based on the detection results, the error that occurs between the calculated widthwise length W1 and the true widthwise length due to the medium P being skewed may be corrected.

[0360] 32 to 34, the front end sensor 627 and the pair of side end sensors 628 are shown schematically.

[0361] (Arrangement of first detection device 500) As described above, the first detection device 500 is disposed inside the image forming apparatus main body 11. Specifically, the first detection device 500 is disposed in the transport path 21. The transport path 21 is a transport path from the medium storage unit 12 to the image forming unit 14. The transport path 21 is an example of a first transport path.

[0362] Furthermore, as shown in Figure 2, the first detection device 500 is positioned downstream of a position 236 upstream along the transport path of the medium P from the formation point 232 where the image is formed to the transfer point 234 where the image is transferred to the medium P, which is the distance 214A the image travels.

[0363] Specifically, when an electrophotographic image forming unit 214 is used, the formation point 232 is, for example, an exposure position on the outer periphery of the photosensitive member 222 where exposure is performed by the exposure device 223. Note that, when the exposure position has a length along the circumferential direction of the photosensitive member 222, the formation point 232 is, for example, the circumferential center of that length.

[0364] Transfer point 234 corresponds to transfer position TA. If transfer position TA has a length along the transport direction of medium P, for example, the center of that length in the transport direction is defined as transfer point 234. Distance 214A is the sum of distance 214B from formation point 232 to primary transfer position 238 toward the downstream side in the rotation direction of photosensitive body 222, and distance 214C from primary transfer position 238 to transfer point 234 toward the downstream side in the rotation direction of transfer body 216 (see dashed line in FIG. 2).

[0365] Position 236 is a position located a distance 214A upstream in the conveying direction from transfer point 234 along the conveying path of conveying path 21. If there are multiple formation points 232 in image forming unit 214, for example, the one with the longest distance corresponds to distance 214A. In the above example, the exposure position is considered to be formation point 232, but it is also possible to consider primary transfer position 238 as formation point 232.

[0366] The first detection device 500 is disposed downstream of the position 236 in the transport direction and upstream of the transfer point 234 in the transport direction.

[0367] When the image forming unit 14 that forms an image with ink is used as the image forming unit, the positions on the transfer body 16 where each of the ejection units 15Y to 15K ejects ink are formation points 232. When there are multiple formation points 232, for example, the one with the longest distance corresponds to the distance 214A.

[0368] (Arrangement of second detection device 30) As described above, the second detection device 30 is disposed inside the image forming apparatus main body 11. Specifically, the second detection device 30 is disposed at a position in the image forming apparatus 10 in which the second detection device 30 is disposed, where the transport of the medium P is stopped. More specifically, the second detection device 30 is disposed in the transport path 24 of the image forming apparatus 10, where the medium P is stopped to change the direction of the transported medium P. Specifically, the transport path 24 is the transport path where the medium P is stopped in order to turn the medium P over. In other words, the transport path 24 turns over the medium on which an image has been formed in the image forming unit 14. The transport path 24 is an example of a second transport path.

[0369] In the conveying path 24, the medium P is turned over by being switched back. The switchback is an operation of moving the medium P back and forth within the same path. In other words, the switchback is an operation of changing the direction of the medium P.

[0370] As described above, the transport path 24 is a transport path along which the medium P is transported from the heating unit 19 to the image forming unit 14. Furthermore, the second detection device 30 is disposed on the transport path 24 upstream in the transport direction of the supply position 25A where new medium P is supplied toward the image forming unit 14.

[0371] In this embodiment, as described above, the medium container 12, the image forming unit 14, and the heating unit 19 are disposed in the portion 18A of the housing 18. The second detection device 30 is disposed in the portion 18B of the housing 18. That is, the second detection device 30 including the front and rear edge detection unit 90 and the heating unit 19 are provided in different portions 18A and 18B of the housing 18.

[0372] Furthermore, in this embodiment, as described above, the second detection device 30 including the front and rear end detection unit 90 is provided downstream in the transport direction from the heating unit 19. Therefore, after the medium P is heated and before an image is formed again on the medium P, the front and rear end detection unit 90 detects the front and rear ends of the medium P, which is in a tensioned state and whose transport has been stopped. Furthermore, in this embodiment, the second detection device 30 including the front and rear end detection unit 90 is provided below the heating unit 19.

[0373] In this embodiment, the second detection device 30 is disposed upstream of a position 236 that is a distance 214A away from the transfer point 234 in the upstream direction of the conveyance direction. In other words, the second detection device 30 is disposed at a position that is farther away from the transfer point 234 than the distance 214A along the conveyance path of the conveyance path 21.

[0374] (Calibration of the first detection device 500 and the second detection device 30) In the detection device 100, calibration of the first detection device 500 and the second detection device 30 can be performed.

[0375] Here, calibration means correcting the relative detection error between the first detection device 500 and the second detection device 30.

[0376] Therefore, calibration includes a case where a relative detection error between the first detection device 500 and the second detection device 30 is corrected by correcting an absolute detection error in each of the first detection device 500 and the second detection device 30. The calibration method in this case will be referred to as the first method hereinafter.

[0377] Calibration also includes the case where the detection value of one of the first detection device 500 and the second detection device 30 is used as a reference to correct the detection error of the other. In this case, the referenced device may have an absolute detection error. The calibration method in this case will be referred to as the second method hereinafter.

[0378] (Common matters between Method 1 and Method 2) The detection device 100 is capable of performing a calibration operation using at least one of a first method and a second method.

[0379] When performing calibration using the first method and calibration using the second method, the first detection device 500 detects the leading and trailing edges of the medium P before it passes through the heating unit 19, and the second detection device 30 detects the leading and trailing edges of the medium P after it has been transported from the first detection device 500 and passed through the heating unit 19, where the surface temperature is lower than during image formation. Note that the surface temperature refers to the surface temperature of the heat-generating parts in the heating unit 19. Examples of heat-generating parts include pressure members such as heating rolls and flash lamps.

[0380] Specifically, the first detection device 500 and the second detection device 30 detect the leading and trailing ends of the same medium P in an unheated state, and perform calibration using the respective detection results. In other words, when performing calibration using the first method and calibration using the second method, the second detection device 30 detects the medium P detected by the first detection device 500 in the same state (specifically, an unheated state) as when the first detection device 500 detects it. Note that unheated also includes applying an amount of heat to the medium P that does not change the state of the medium P.

[0381] (First method) The first method is carried out by the following procedure.

[0382] For example, the user places a medium P dedicated to proofreading (hereinafter referred to as proofreading medium P) in the medium storage section 12, and instructs the image forming device 10 to perform proofreading via an operation section (not shown) such as an operation panel, thereby performing proofreading.

[0383] Here, in the first method, a medium P whose transport direction length and width direction length are known is used as the calibration medium P. Therefore, the control device 160 has information on the known transport direction length and width direction length of the calibration medium P as reference values. This information is stored in, for example, the storage 163.

[0384] The control unit 161C of the control device 160 controls each unit of the image forming apparatus 10 (for example, the first detection device 500, the second detection device 30, the heating unit 19, and the conveying mechanism 20) to perform the calibration operation described below.

[0385] In the calibration operation by the first method, the transport mechanism 20 transports the calibration medium P from the medium container 12 to the first detection device 500 along the transport path 21.

[0386] Next, the detection units 610 and 620 of the first detection device 500 detect the front end, the rear end, and a pair of side ends of the calibration medium P being transported.

[0387] As described above, the acquisition unit 161A acquires detection information obtained by the detection units 610 and 620 detecting the front end, rear end, and pair of side end portions of the calibration medium P. As described above, the measurement unit 161B measures the transport direction length and width direction length of the medium P based on the position information acquired by the acquisition unit 161A.

[0388] Furthermore, the measurement unit 161B calculates a correction value by comparing the measured transport direction length and width direction length (i.e., the measured values) with the known transport direction length and width direction length (i.e., the reference values) of the calibration medium P. The correction value (specifically, the correction ratio) SA is calculated for each of the transport direction length and width direction length as the ratio between the measured value SB and the reference value SC, for example, as shown in the following formula (A).

[0389] Formula (A): SA = SB ÷ SC

[0390] Information about the calculated correction value is stored, for example, in the storage 163. Note that the correction value may be calculated, for example, from the difference between the measurement value SB and the reference value SC.

[0391] Furthermore, the calibration medium P, whose front end, rear end, and pair of side ends have been detected by the first detection device 500, is transported by the transport mechanism 20 to the second detection device 30 via the transport paths 21, 22, and 24. At this time, the heating unit 19 does not perform a heating operation on the calibration medium P. In other words, the transport mechanism 20 passes the calibration medium P through the heating unit 19, whose heating operation has been stopped, and then transports it to the second detection device 30.

[0392] Furthermore, if the heating unit 19 is configured to have contact members that come into contact with the medium P (a heating member such as a heating roll and a pressure member such as a pressure roll), the contact members may be retracted, for example, to a position where they do not come into contact with the calibration medium P. Specifically, in the heating unit 19 that heats the medium P by sandwiching it between a heating member and a pressure member, the state in which the heating member and the pressure member sandwich the calibration medium P (the so-called nip state) may be released. In other words, the heating member and the pressure member may be separated. Note that in the heating unit 19, if the heating member and the pressure member function as transport members that transport the calibration medium P, for example, the pressure with which the heating member and the pressure member sandwich the medium P (the so-called nip pressure) is reduced during the calibration operation compared to during the image formation operation.

[0393] Furthermore, at the transfer position TA, the state in which the transfer body 16 and the opposing member 17 sandwich the calibration medium P (the so-called nip state) may be released. That is, the transfer body 16 and the opposing member 17 may be separated. Also, when the transfer body 16 and the opposing member 17 function as transport members that transport the calibration medium P, for example, the pressure with which the transfer body 16 and the opposing member 17 sandwich the medium P (the so-called nip pressure) is reduced during the calibration operation compared to during the image formation operation.

[0394] Next, the second detection device 30 uses the front and rear end detection unit 90 and the side end detection unit 98 to detect the front end, rear end, and pair of side ends of the tensioned calibration medium P. As will be described later, the second detection device 30 does not require the calibration medium P to be tensioned; it is sufficient if the calibration medium P is not tensioned and its transport is stopped.

[0395] As described above, the acquisition unit 161A acquires detection information obtained by the front and rear end detection unit 90 and the side end detection unit 98 detecting the front end, rear end, and pair of side ends of the calibration medium P. As described above, the measurement unit 161B measures the transport direction length and width direction length of the medium P based on the position information acquired by the acquisition unit 161A.

[0396] Furthermore, the measurement unit 161B calculates a correction value by comparing the measured transport direction length and width direction length (i.e., the measured values) with the known transport direction length and width direction length (i.e., the reference values) of the calibration medium P. The correction value (specifically, the correction ratio) SA is calculated for each of the transport direction length and width direction length as the ratio between the measured value SB and the reference value SC, for example, as in the above-mentioned formula (A).

[0397] Information about the calculated correction value is stored, for example, in the storage 163. Note that the correction value may be calculated, for example, from the difference between the measurement value SB and the reference value SC.

[0398] During the image forming operation in the image forming device 10, the measurement unit 161B corrects the conveying direction length and width direction length (measured value SE) measured from the detection information detected by the first detection device 500 and the second detection device 30 using a correction value.

[0399] Specifically, as shown in the following formula (B), a value SF obtained by multiplying the measurement value SE by a correction value (correction ratio) SA is calculated as the corrected measurement value.

[0400] Formula (B): SF=SE×SA

[0401] Then, the measurement unit 161B measures the size (dimensions) of the medium P based on the corrected measurement values ​​of the transport direction length and width direction length of the medium P. The control unit 161C performs image adjustment of the image formed on the medium P whose edge has been detected, based on the size (dimensions) of the medium P measured by the measurement unit 161B.

[0402] (Second method) In the second method, the detection error of one of the first detection device 500 and the second detection device 30 is corrected based on the detection value of the other, so the length in the transport direction and the width direction of the calibration medium P do not need to be known. In the second method, for example, the control device 160 does not have information on the known lengths in the transport direction and the width direction of the calibration medium P.

[0403] The control unit 161C of the control device 160 controls each unit of the image forming apparatus 10 (for example, the first detection device 500, the second detection device 30, the heating unit 19, and the conveying mechanism 20) to perform the calibration operation described below.

[0404] In the calibration operation by the second method, the transport mechanism 20 transports the calibration medium P from the medium container 12 to the first detection device 500 along the transport path 21.

[0405] Next, the detection units 610 and 620 of the first detection device 500 detect the front end, the rear end, and a pair of side ends of the calibration medium P being transported.

[0406] As described above, the acquisition unit 161A acquires detection information obtained by the detection units 610 and 620 detecting the front end, rear end, and pair of side end portions of the calibration medium P. As described above, the measurement unit 161B measures the transport direction length and width direction length of the medium P based on the position information acquired by the acquisition unit 161A.

[0407] Furthermore, the calibration medium P, whose front end, rear end, and pair of side ends have been detected by the first detection device 500, is transported by the transport mechanism 20 to the second detection device 30 via the transport paths 21, 22, and 24. At this time, as with the calibration operation using the first method, the heating unit 19 does not perform a heating operation on the calibration medium P. In other words, the transport mechanism 20 passes the calibration medium P through the heating unit 19, whose heating operation has been stopped, and then transports it to the second detection device 30.

[0408] Furthermore, in the heating unit 19 and the transfer position TA, an operation to release the nip or an operation to reduce the nip pressure may be performed, similar to the calibration operation by the first method.

[0409] Next, the second detection device 30 uses the front and rear end detection unit 90 and the side end detection unit 98 to detect the front end, rear end, and pair of side ends of the tensioned calibration medium P. As will be described later, the second detection device 30 does not require the calibration medium P to be tensioned; it is sufficient if the calibration medium P is not tensioned and its transport is stopped.

[0410] As described above, the acquisition unit 161A acquires detection information obtained by the front and rear end detection unit 90 and the side end detection unit 98 detecting the front end, rear end, and pair of side ends of the calibration medium P. As described above, the measurement unit 161B measures the transport direction length and width direction length of the medium P based on the position information acquired by the acquisition unit 161A.

[0411] Furthermore, the measurement unit 161B compares the conveying direction length and width direction length (i.e., the measured values) based on the detection values ​​by the first detection device 500 with the conveying direction length and width direction length (i.e., the measured values) based on the detection values ​​by the second detection device 30, and calculates a correction value.

[0412] In this embodiment, calibration is performed by correcting the detection error of the detection device with lower detection accuracy relative to the detection value of the detection device with higher detection accuracy, either the first detection device 500 or the second detection device 30.

[0413] In this embodiment, the detector with the highest detection accuracy is the second detector 30, which detects the leading and trailing edges of the heated medium P while the medium P is stationary. Therefore, in this embodiment, the detection error of the first detector 500 is corrected for the transport direction length and width direction length (i.e., the measurement value TB) of the second detector 30.

[0414] That is, the correction value (specifically, the correction ratio) TA is calculated for each of the conveying direction length and the width direction length by, for example, the ratio between the measurement value TB from the first detection device 500 and the measurement value TC from the second detection device 30, as shown in the following formula (C).

[0415] Formula (C): TA = TB ÷ TC

[0416] Information about the calculated correction value is stored in, for example, the storage 163. Note that the correction value may be calculated from, for example, the difference between the measurement value TB of the first detection device 500 and the measurement value TC of the second detection device 30.

[0417] During the image forming operation in the image forming apparatus 10, the measurement unit 161B corrects the conveyance direction length and width direction length (measured value TE) measured from the detection information detected by the first detection device 500 using the correction value.

[0418] Specifically, as shown in the following formula (D), a value TF is calculated by multiplying the measurement value TE by a correction value (correction ratio) TA, and the corrected measurement value is calculated.

[0419] Formula (D): TF=TE×TA

[0420] Then, the measurement unit 161B measures the size (dimensions) of the medium P based on the corrected measurement values ​​of the transport direction length and width direction length of the medium P. The control unit 161C performs image adjustment of the image formed on the medium P whose edge has been detected, based on the size (dimensions) of the medium P measured by the measurement unit 161B.

[0421] In the above example, the detection error of the first detection device 500 was corrected against the detection value of the second detection device 30, but this is not limited to this, and the detection error of the second detection device 30 may also be corrected against the detection value of the first detection device 500.

[0422] Furthermore, when performing calibration using the first method and calibration using the second method, when the transport mechanism 20 transports the calibration medium P from the first detection device 500 to the second detection device 30, the heating unit 19 does not perform a heating operation on the calibration medium P, but this is not limited to this.

[0423] When performing calibration using the first method and calibration using the second method, the heating unit 19 may perform a heating operation at a surface temperature lower than that during image formation operation (preheating, etc.), and the calibration medium P may be passed through the heating unit 19.

[0424] (Action according to this embodiment) As described above, the detection device 100 includes a first detection device 500 that detects the leading and trailing ends of the medium P before heating, and a second detection device 30 that is separate from the first detection device 500 and that detects the leading and trailing ends of the medium P after heating.

[0425] Therefore, compared to using the same detection device to detect the leading and trailing edges of the medium P before and after heating, it is possible to easily satisfy different requirements for the medium P before and after heating. Specifically, for example, before heating, the first detection device 500 detects the edge of the medium P being transported, prioritizing detection speed and shortening the time required for detection. However, after heating, the second detection device 30 can be configured to detect the edge of the medium P whose transport has stopped, prioritizing detection accuracy. When detecting the edge of the medium P after transport has stopped, it takes time to return the stopped medium P to its original transport speed. However, when detecting the edge of the medium P while it is being transported, it does not take time to return to its original transport speed, thereby shortening the time required for detection.

[0426] In this embodiment, the first detection device 500 and the second detection device 30 detect the leading edge and trailing edge of the same medium P in an unheated state, and perform calibration using the respective detection results.

[0427] Therefore, the first detection device 500 and the second detection device 30 have improved calibration accuracy compared to when detecting the front and rear ends of the same medium P in heated and unheated states (i.e., different states).

[0428] In this embodiment, calibration is performed by correcting the detection error of the detection device with lower detection accuracy relative to the detection value of the detection device with higher detection accuracy, either the first detection device 500 or the second detection device 30.

[0429] Therefore, by correcting the detection error of the detection device with lower detection accuracy for the detection value of the detection device with lower detection accuracy, either the first detection device 500 or the second detection device 30, the detection accuracy of the detection device 100 is improved compared to when calibration is performed.

[0430] In this embodiment, the detector with high detection accuracy is the second detector 30, which detects the leading and trailing edges of the medium P after heating while the medium P is stationary.

[0431] Therefore, the detection accuracy of the detection device 100 is improved compared to when the detection device with high detection accuracy is a detection device that detects the leading and trailing edges of the medium during transport and after heating.

[0432] In this embodiment, when calibrating the first detection device 500 and the second detection device 30, the first detection device 500 detects the leading and trailing ends of the medium P before it passes through the heating section 19, and the second detection device 30 detects the leading and trailing ends of the medium P that has been transported from the first detection device 500 and passed through the heating section 19, where the surface temperature is lower than during image formation operation.

[0433] Therefore, when calibrating the first detection device 500 and the second detection device 30, the accuracy of the calibration is improved compared to when both the first detection device 500 and the second detection device 30 perform the same detection as during image formation operation.

[0434] 2, the first detection device 500 is disposed downstream of a position 236 along the transport path of the medium P, the distance 214A that the image travels from a formation point 232 where the image is formed to a transfer point 234 where the image is transferred to the medium P. On the other hand, the second detection device 30 is disposed upstream of the position 236.

[0435] Therefore, even if the first detection device 500 is placed closer to the transfer point 234 due to requirements such as miniaturization, it is possible to have the detection results of the second detection device 30 reflected in image formation (specifically, formation of a back-side image) based on the first detection device 500 and the second detection device 30 in time.

[0436] In this embodiment, the first detection device 500 is arranged on the conveying path 21 from the media storage section 12 to the image forming section 14, and the second detection device 30 is arranged on the conveying path 24 that inverts the media on which an image has been formed in the image forming section 14.

[0437] Therefore, the leading and trailing ends of the medium P being transported on each of the transport paths 21 and 24 can be detected on each of the transport paths 21 and 24.

[0438] In this embodiment, the first detector 500 detects the leading and trailing edges of the medium P while it is being transported, and the second detector 30 detects the leading and trailing edges of the medium P while it is stationary.

[0439] Therefore, compared to when the first detector 500 and the second detector 30 detect the leading and trailing edges of the medium P during transport, the detection time required by the first detector 500 is kept the same, while the detection accuracy of the second detector 30 is improved. The medium P that has passed through the heating unit 19 tends to shrink and curl, making the medium P prone to flapping. For this reason, it is desirable for the second detector 30 to stop the medium P and detect the edges. Furthermore, stopping the medium P to detect the edges reduces detection errors associated with the movement of the medium P.

[0440] (Variation) In this embodiment, the first detection device 500 and the second detection device 30 detect the leading and trailing edges of the same medium P in an unheated state and perform calibration using the respective detection results, but this is not limited to this. For example, the first detection device 500 and the second detection device 30 may be configured to detect the leading and trailing edges of the same medium P in a heated and unheated state (i.e., different states).

[0441] In the present embodiment, calibration is performed by correcting the detection error of the detection device with lower detection accuracy relative to the detection value of the detection device with higher detection accuracy out of the first detection device 500 and the second detection device 30, but this is not limited to this. For example, calibration may be performed by correcting the detection error of the detection device with lower detection accuracy relative to the detection value of the detection device with lower detection accuracy out of the first detection device 500 and the second detection device 30.

[0442] In this embodiment, the detector with high detection accuracy is the second detector 30 that detects the leading and trailing edges of the medium P after heating while the medium P is stationary, but this is not limited to this. For example, the detector with high detection accuracy may be a detector that detects the leading and trailing edges of the medium during transport and after heating.

[0443] In this embodiment, when calibrating the first detection device 500 and the second detection device 30, the first detection device 500 detects the leading and trailing edges of the medium P before it passes through the heating unit 19, and the second detection device 30 detects the leading and trailing edges of the medium P that has been transported from the first detection device 500 and passed through the heating unit 19, where the surface temperature is lower than during the image formation operation. However, this is not limited to this. For example, when calibrating the first detection device 500 and the second detection device 30, both the first detection device 500 and the second detection device 30 may be configured to perform the same detection as during the image formation operation.

[0444] In this embodiment, the first detector 500 detects the leading and trailing edges of the medium P while it is being transported, and the second detector 30 detects the leading and trailing edges of the medium P while it is stationary, but this is not limited to this. For example, the first detector 500 and the second detector 30 may be configured to detect the leading and trailing edges of the medium P while it is being transported.

[0445] (Modification of the second detection device 30) Although the second detection device 30 is configured to detect the edge of the medium P when the transport is stopped and the medium is pulled in the tensile direction, this is not limited to this. It may also be configured to detect the edge of the medium P when the transport is stopped and the medium P is not being pulled. In this configuration, for example, the transport member 83 (drive roll 86 and driven roll 89) and the transport members 81 and 82 (drive rolls 84 and 85 and driven rolls 87 and 88) stop rotating without any time lag, thereby stopping the medium P. Furthermore, the second detection device 30 may be configured to detect the edge of the medium P during transport.

[0446] (Modification of the arrangement of the first detection device 500) Although the first detection device 500 is disposed downstream in the transport direction from the position 236 and upstream in the transport direction from the transfer point 234, the present invention is not limited to this. For example, the first detection device 500 may be configured to be disposed upstream in the transport direction from the position 236 and downstream in the transport direction from the supply position 25A, as long as it is disposed in a position where it can detect the leading end and trailing end of the medium P before heating.

[0447] (Modification of the arrangement of the second detection device 30) In the present embodiment, the second detection device 30 including the front and rear end detection units 90 and the heating unit 19 are provided in different parts 18A and 18B of the housing 18, but this is not limiting. For example, the second detection device 30 including the front and rear end detection units 90 and the heating unit 19 may be provided in the same part of the housing 18.

[0448] In the present embodiment, the second detecting device 30 including the front and rear end detecting units 90 is provided below the heating unit 19, but this is not limiting. The second detecting device 30 including the front and rear end detecting units 90 may be provided above the heating unit 19.

[0449] Furthermore, in the present embodiment, the second detection device 30 is disposed on the upstream side of the transport path 24 in the transport direction relative to the supply position 25A where new medium P is supplied toward the image forming unit 14 (specifically, on the transport path 80A). However, this is not limited to this. For example, instead of or in addition to the second detection device 30 disposed on the transport path 24 (specifically, on the transport path 80A), the second detection device 30 may be disposed downstream of the transport path 80A in the transport direction and upstream of the supply position 25A in the transport direction. In this configuration, for example, the second detection device 30 is disposed at a position where it is stopped to maintain a distance from the medium P supplied from the medium storage unit 12 to the supply position 25A. In the transport unit 80 in this configuration, for example, transport of the medium P on which an image has been formed on the front side in the first transport direction is stopped and the medium P is pulled. After the medium P is stopped, transport of the medium P is resumed in the second transport direction, which is the same direction as the first transport direction, toward the image forming unit 14 (specifically, the transfer position TA). In this configuration, the second detection device 30 disposed on the transport path 80A may not be provided, and the transport path 24 may be configured as a transport path in which the medium P is not reversed. In this configuration, the second image is formed again on one side (front side) of the medium P on which the front side image as the first image has been formed. In this way, the second image may be an image formed on the side on which the first image has been formed.

[0450] The second detector 30 may be disposed at a position where it can detect the leading and trailing edges of the medium P after heating.

[0451] (Modification of image formed on medium P) In the present embodiment, the front image as the first image is formed on one side of the medium P, and the back image as the second image is formed on the other side of the medium P, but this is not limiting. The second image may be formed on the side of the medium P on which the first image is formed.

[0452] Furthermore, in this embodiment, the front image as the first image and the back image as the second image are formed by the same image forming unit 14, but they may be formed by different image forming units.

[0453] The first image may be, for example, an image formed by other means (for example, an image forming unit provided in the image forming device 10 separately from the image forming unit 14, or an image forming device separate from the image forming device 10) instead of or in addition to the image formed by the image forming unit 14. The first image may be any image formed on the medium P before the edge of the medium P is detected.

[0454] The present invention is not limited to the above-described embodiment, and various modifications, changes, and improvements are possible without departing from the spirit of the present invention. For example, the above-described modified examples may be appropriately combined to form a configuration. [Explanation of symbols]

[0455] 10 Image forming device 14, 214 Image forming section 19 Heating section 20 Transport mechanism (an example of a media transport unit) 21 Conveyor path (example of first conveyor path) 24 Conveyor path (example of second conveyor path) 30 Second detection device (an example of a second detection unit) 100 Detection device 500 First detection device (an example of a first detection unit) P medium

Claims

1. a first detector for detecting a front end and a rear end of the medium before heating; a second detection unit that detects the leading edge and the trailing edge of the medium after heating and is separate from the first detection unit; Equipped with the first detection unit and the second detection unit detect the leading edge and the trailing edge of the same medium in an unheated state, and perform calibration using the respective detection results; The calibration is performed by correcting a detection error of a detection unit with low detection accuracy with respect to a detection value of a detection unit with high detection accuracy out of the first detection unit and the second detection unit. Detection device.

2. The detection unit with high detection accuracy is the second detection unit detects the leading edge and the trailing edge of the medium after heating while the medium is stationary; The detection device according to claim 1 .

3. A first detection unit that detects the front end and rear end of the medium before heating; a second detector that detects the leading and trailing edges of the medium after heating and is separate from the first detector; A detection unit; an image forming unit that forms an image based on the detection results of the first detection unit and the second detection unit; a first conveying path that conveys the medium from a medium storage unit that stores the medium to the image forming unit; a second conveying path that reverses the medium on which the image has been formed by the image forming unit; Equipped with the first detection unit is disposed on the first transport path, the second detection unit is disposed on the second transport path, the first detector detects a leading edge and a trailing edge of the medium being conveyed; The second detection unit detects the leading and trailing edges of a stationary medium. Image forming device.

Images