Sheet conveying device and image forming apparatus

Abstract

To provide a sheet transport device that surely detects a paper tip of a roll and stably transports delivered paper to a paper feeding part.SOLUTION: The sheet transport device for supplying paper P from a roll Pr formed by winding sheet-like paper to a paper feeding part, includes: a sensor 93 capable of detecting a paper tip of the roll Pr; a roller member 92 disposed at a different position from the sensor 93 in a circumferential direction of the roll Pr; and a guide member 91 capable of supporting the sensor 93 and the roller member 92 so as to abut on a surface of the roll Pr. The sheet transport device controls the rotation speed of the roll Pr when supplying the paper tip to the paper feeding part in response to the sensor displacement output.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] In image forming devices that use rolls (roll paper) formed by winding sheet-shaped paper, sheet conveying devices equipped with a paper feed mechanism are already known in which a user manually inserts the leading edge of the paper into the paper feed section, and the device detects the leading edge and then performs the paper feeding operation. Conventional paper feeding procedures require the manual insertion of the leading edge of the roll of paper, which is time-consuming, and depending on how the paper is inserted, it can be inserted at an angle, causing skew and requiring a service call.

[0003] To address this problem, Patent Document 1 discloses a technology in which the roll is rotated in the winding direction to peel off the paper, and the leading edge of the peeled paper is detected using a sensor (a sensor whose output value changes depending on the distance to the paper). Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the device of Patent Document 1, the peeling condition changes depending on the thickness, stiffness, and curl of the paper, so the sensor output can become unstable, making it difficult to reliably detect the leading edge of the paper.

[0005] On the other hand, when the leading edge of the paper is detected and the paper is automatically transported to the paper feed section, it is required to stabilize the behavior of the paper.

[0006] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a sheet transport device that can reliably detect the leading edge of the paper on the roll and can stably transport the unwound paper to the paper feed unit. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, the sheet conveying device of the present invention is a sheet conveying device that supplies paper from a roll formed by winding a sheet-like paper to a paper feeding section, Areas with uneven surfaces Paper edge as a sensor that can detect the temperature difference and a sensor that is disposed at a position different from the sensor in the circumferential direction of the roll; , pressing the leading edge of the paper a roller member; and a guide member that supports the sensor and the roller member so as to contact the surface of the roll, two or more roller members are arranged in the width direction of the guide member, and the sensor is arranged between one of the roller members and another of the roller members in the width direction of the guide member; The rotation speed of the roll when the leading edge of the paper is fed to the paper feed unit is controlled in accordance with the sensor displacement output. Another aspect of the sheet conveying device of the present invention is a sheet conveying device that supplies sheet-shaped paper from a roll formed by winding the paper to a paper supply section, and is equipped with a sensor that can detect the leading edge of the paper on the roll, a roller member that is positioned at a different position from the sensor in the circumferential direction of the roll, and a guide member that supports the sensor and the roller member so that they abut against the surface of the roll, and detects the paper thickness of the paper according to the sensor displacement output, and controls the rotation speed of the roll when supplying the leading edge of the paper to the paper supply section. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a sheet transport device that can reliably detect the leading edge of the paper on the roll and can stably transport the unwound paper to the paper feed unit. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram illustrating an example of a schematic configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 2] 1 is a schematic cross-sectional view showing an example of the configuration of an image forming apparatus according to an embodiment of the present invention. [Figure 3] FIG. 10 is a diagram illustrating a conventional method for setting a roll. [Figure 4] 1 is a side view illustrating a main part of a configuration example of a sheet conveying device according to an embodiment of the present invention. [Figure 5] FIG. 2 is a block diagram illustrating an example of functions of a sheet conveying device according to an embodiment of the present invention. [Figure 6] 3A and 3B are diagrams illustrating an example of the configuration of a guide member and a sensor. [Figure 7] 10A and 10B are diagrams illustrating an example of an operation for detecting the leading edge of the paper on the roll. [Figure 8] 10A and 10B are diagrams illustrating differences due to the positional relationship between the roller member and the sensor. [Figure 9]1A and 1B are diagrams showing a schematic diagram and an example of a signal waveform when a concave scratch is present on the roll surface; [Figure 10] 10A and 10B are explanatory diagrams showing the relationship between the position of the paper tip on the roll and changes in the sensor output signal. [Figure 11] FIG. 4 is an explanatory diagram showing details of changes in a sensor signal. [Figure 12] FIG. 10 is an explanatory diagram showing the relationship between the roll diameter and the amount of change in the sensor signal. [Figure 13] 10 is an explanatory diagram showing the relationship between the thickness of a sheet and the amount of displacement (pulse) of a sensor signal. FIG. [Figure 14] 10 is a flowchart illustrating an example of an operation for setting a roll in the sheet conveying device according to the embodiment of the present invention. [Figure 15] 15 is a flowchart showing a detailed flow of the leading edge detection process in the flowchart of FIG. 14. [Figure 16] 16 is a flowchart showing the flow following FIG. 15. [Figure 17] FIG. 17 is a diagram illustrating symbols used in FIGS. 15 and 16. DETAILED DESCRIPTION OF THE INVENTION

[0010] The sheet conveying device and image forming apparatus of the present invention will be described below with reference to the drawings. The present invention is not limited to the following embodiments, and can be modified, added, modified, deleted, or otherwise altered within the scope of what one skilled in the art can conceive. As long as the effects and advantages of the present invention are achieved in any aspect, it is within the scope of the present invention. In addition, in each drawing, components and corresponding parts having the same configuration or function are designated by the same reference numerals, and their description will be omitted.

[0011] The sheet conveying device according to the present invention feeds paper from a roll formed by winding a long piece of paper (also referred to as a "sheet") around the roll.

[0012] An example of the configuration of an image forming apparatus to which a sheet conveying device according to an embodiment of the present invention is applied will be described with reference to FIGS. An image forming apparatus according to one embodiment of the present invention is an inkjet printer that prints on a recording medium by ejecting ink droplets in accordance with image data, but the present invention can also be applied to electrophotographic copying machines and printers that transport a recording medium and print.

[0013] Fig. 1 is a perspective view of a schematic configuration example of an image forming apparatus 80 according to one embodiment, and Fig. 2 is a side cross-sectional view of the image forming apparatus, and the overall configuration of the image forming apparatus according to one embodiment and the operation of its main parts will be described. In Fig. 1, arrows indicate X, Y, and Z, respectively, in the depth direction (front-rear direction) of the image forming apparatus 80, width direction (main scanning direction) of the image forming apparatus 80, and up-down direction.

[0014] 1, an image forming apparatus 80 includes an image forming section 60 and a sheet conveying section 20. FIG. 1 shows a serial-type liquid ejection (ink ejection) image forming apparatus, in which a main body housing 81 is disposed on a main body frame 82. In the image forming apparatus 80, a main guide rod 64 and a sub-guide rod 65 are stretched within the main body housing 81 in the main scanning direction indicated by the double-headed arrow Y in FIG. 1. The main guide rod 64 movably supports a carriage 66, and the carriage 66 is provided with a connecting piece 66a that engages with the sub-guide rod 65 to stabilize the position of the carriage 66.

[0015] In the image forming device 80, an endless timing belt 67 is disposed along a main guide rod 64, and the timing belt 67 is stretched between a drive pulley 68 and a driven pulley 69. The drive pulley 68 is driven to rotate by a main scanning motor 70, and the driven pulley 69 is disposed in a state in which it applies a predetermined tension to the timing belt 67. The drive pulley 68 is driven to rotate by the main scanning motor 70, and thereby causes the timing belt 67 to rotate in the main scanning direction according to the direction of rotation of the drive pulley 68.

[0016] The carriage 66 is connected to a timing belt 67, and when the timing belt 67 is rotated in the main scanning direction by a drive pulley 68, the carriage 66 moves back and forth in the main scanning direction along the main guide rod 64.

[0017] In the image forming device 80, a cartridge unit 71 and a maintenance mechanism unit 72 are detachably housed at an end position in the main scanning direction within a main body housing 81. Cartridge unit 71 houses replaceable cartridges 73, each containing yellow (Y), magenta (M), cyan (C), and black (K) ink. Each cartridge in cartridge unit 71 is connected by a pipe (not shown) to a recording head of the corresponding color among the recording heads (not shown) mounted on carriage 66, and ink is supplied from cartridge unit 71 to the recording head of each color through the pipe.

[0018] The image forming device 80 records an image on the paper P by ejecting ink onto the paper P, which is transported intermittently in a sub-scanning direction (the direction of arrow X in Figure 1) perpendicular to the main scanning direction, on a platen (plate) 74 (see Figure 2) while moving the carriage 66 in the main scanning direction.

[0019] The paper P is not limited to paper, and various types such as film can be used. However, in the following explanation, for clarity, the paper being transported will be referred to as paper P, the roll formed by winding paper P will be referred to as Pr(Pa, Pb), and the core tube (core portion) of roll Pr will be referred to as Ps.

[0020] As shown in FIG. 2, the image forming device 80 has a chamber 75 with a fan disposed below the platen 74, and by driving the fan, the paper P transported on the platen 74 is transported in close contact with the platen 74.

[0021] The image forming device 80 intermittently transports paper P in the sub-scanning direction, and while the transport of paper P in the sub-scanning direction is stopped, it moves the carriage 66 in the main scanning direction and ejects ink from the nozzle array of the recording head mounted on the carriage 66 onto the paper P on the platen 74, thereby forming (recording) an image on the rolled paper P.

[0022] The maintenance mechanism 72 cleans the ejection surface of the print head, caps it, ejects unnecessary ink, etc., in order to discharge unnecessary ink from the print head and maintain the reliability of the print head.

[0023] In the image forming device 80, an encoder sheet (not shown) is disposed parallel to the timing belt 67 and the main guide rod 64, at least over the range of movement of the carriage 66. An encoder sensor that reads the encoder sheet is attached to the carriage 66. The image forming device 80 controls the movement of the carriage 66 in the main scanning direction by controlling the drive of the main scanning motor 70 based on the results of reading the encoder sheet by the encoder sensor.

[0024] In addition, a reflective sensor (encoder sensor, paper tip detection sensor) mounted on the carriage 66 detects both ends of the paper P transported to the image forming unit 60, and at that time, the size of the paper P is detected from the main scanning direction position read by the paper tip detection sensor.

[0025] In the image forming apparatus 80, as shown in FIGS. 1 and 2, two spool bearing pedestals 5a and 5b are provided on a main body frame 82 that supports a main body housing 81, in the vertical direction in FIGS.

[0026] The paper P pulled out from the tip of the roll Pr set on the spool bearing bases 5a and 5b is transported within the transport path 9 by the transport roller pair 6a and 6b, the registration roller 10, and the registration pressure roller 17, as shown by the arrows in Figure 2. The control unit 100 controls the driving device 7 to rotate the pair of conveying rollers 6a and 6b, the registration roller 10, the registration pressure roller 17, and the like. Below the roll Pr (Pa, Pb), roll paper trays 8a, 8b are provided to prevent the roll Pr from falling.

[0027] The paper P passes through a transport path 9 supported by medium transport guide members 18a, 18b, etc., and is transported onto a platen 74 in the image forming unit 60. When images are to be formed on both sides, the paper P is reversed in a reversing unit 19.

[0028] In the image forming unit 60, an image is formed by a liquid recording head discharging droplets of each color onto the paper P in accordance with image data. A cutter 76 extending in the sub-scanning direction (paper width direction) is provided at the forward transport direction discharge section for the paper P on which the image has been formed, and is used to cut the paper P, which is made of continuous paper, to a predetermined length.

[0029] To align the leading edge of the transported continuous paper P, the cutter 76 is fixed to a wire or timing belt stretched between multiple pulleys (one of which is connected to a drive motor), and is moved in the main scanning direction Y by the drive motor to cut the paper P to a predetermined length. The cut paper P is then discharged to the discharge section. 1 and 2 show an example of the configuration of an image forming apparatus in which rolls Pa and Pb can be set on two spool bearing pedestals 5a and 5b, but the image forming apparatus may also be provided with one spool bearing pedestal.

[0030] In the above description, the configurations corresponding to the two rolls Pa and Pb are described using the identifiers a and b, but hereinafter, when there is no need to distinguish between them, they will be referred to as Pr. Furthermore, for example, spool bearing pedestals 5a, 5b, etc. will not be described below with the identifiers a, b unless they are to be distinguished.

[0031] A conventional method for setting roll paper will now be described with reference to Figure 3, which is a diagram illustrating a conventional method for setting roll paper. Roll Pr (Pa, Pb) has flanges (flange members) at its widthwise ends, and spool 1 is set on it. The user places roll Pr with spool 1 set on the paper feeder receiver (spool bearing stand) of the device, finds the leading edge of the paper on roll Pr, and while maintaining the leading edge, holds it down with both hands as shown in Figure 3(B), and rotates roll Pr so that the leading edge of paper P is at the front. Next, the user positions the leading edge of the paper between guide plates G at the back of roll Pr and inserts it while rotating roll Pr (see Figures 3(C) and 3(D)). Guide plates G are made of a transparent material so that the paper can be seen, and consist of two plates, one on top and one on bottom. The user rotates the roll paper to the back so that the leading edge of the paper is at the top of the lower guide, and when the paper is inserted into the back of the guide, the paper is fixed internally and pulled into the device.

[0032] The guide plate where the leading edge of the paper is inserted is located at the back of the roll Pr, so it is hidden by the roll Pr and is difficult to see, and because it is transparent, even if you think you have inserted it between two guide plates, it may end up being above the upper guide plate, and you may have to start over. Also, if the guide plates were not transparent, it would be difficult to check whether the paper was inserted between the two guide plates. In addition, the leading edge of the paper roll needs to be inserted as evenly as possible, which requires careful attention. If the leading edge of the paper is not inserted evenly, it will be fed at an angle, causing skew, which will lead to the operation having to be redone or a jam.

[0033] Furthermore, as shown in Figures 3(A) to 3(C), in an apparatus in which the roll setting section is configured in two stages, when roll Pa is set in the upper stage and roll Pb is set in the lower stage and the tip is inserted between the guide plates, the guide plate G is even more difficult to see because roll Pa is already in the upper stage, making setting difficult and increasing the risk of inserting it at an angle.

[0034] Therefore, the sheet conveying device of this embodiment detects the leading edge of the paper on the roll Pr by detecting the step at the leading edge with a sensor, and conveys the leading edge of the paper to the paper feed unit. The paper feed section is a means for supplying paper P to a destination (for example, an image forming section of an image forming apparatus), and is configured by, for example, the pair of conveying rollers 6 or the conveying path 9 in FIG.

[0035] FIG. 4 is a side view illustrating a main part of a configuration example of a sheet conveying device according to an embodiment. As shown in Figure 4, the sheet conveying device of this embodiment is a sheet conveying device that supplies paper P to a paper supply section from a roll Pr formed by winding sheet-shaped paper, and is equipped with a sensor 93 that can detect the leading edge of the paper on the roll Pr, a roller member 92 that is positioned at a different position from the sensor 93 in the circumferential direction of the roll Pr, and a guide member 91 that supports the sensor 93 and roller member 92 so that they abut against the surface of the roll Pr. The guide member 91 is rotatable and supports the roller member 92 and the sensor 93 so that they can be moved toward and away from the surface of the roll Pr. It is also preferable to provide a pair of transport rollers 6 that constitute the paper feed section, and further provide an entrance guide plate 95 on the upstream side in the direction in which the leading edge of the paper is fed to the paper feed section.

[0036] 4 shows the position of the roll Pr when it is set in the sheet conveying device. The roll Pr is held by a module component (not shown) so as to be rotatable about a roll center (axis) 96. In Figure 4, the forward rotation indicated by arrow D2 is the rotation direction during paper feed operation, in which roll paper Pr is sent in the transport direction, and the reverse rotation indicated by arrow D3 is the rotation direction during paper leading edge detection operation. The paper leading edge stop position is indicated by S.

[0037] The guide member 91 is configured to be rotatable about a rotation center 911. The guide member 91 also supports a roller member 92 and a sensor 93 on the other end side of the rotation center 911 in the paper transport direction. The guide member 91 is pressed toward the roll Pr by a spring or the like, so that the roller member 92 and the sensor 93 abut against the outer periphery of the roll Pr even if the roll diameter changes. Arrow D4 indicates the rotation direction of the guide member 91.

[0038] The guide member 91 also serves to guide the paper P peeled off from the roll Pr to the paper feed section. It is preferable that the guide member 91 has a shape (e.g., arc-shaped) in the area facing the roll Pr so that the roll Pr is held in place (to prevent it from falling, etc.) when the roll Pr is set. The guide member 91 also functions as the roll paper tray 8 shown in FIG. In this way, the guide member 91 also serves as a member for guiding the roll Pr, thereby reducing the number of parts and making it possible to keep costs down. The roller member 92 and the sensor 93 are arranged so as to face the center (shaft) 96 of the roll (so as to face the center (shaft) 96 of the roll), regardless of the size of the diameter of the roll.

[0039] The roll Pr rotates in the reverse direction (CW) indicated by arrow D3 to wind up the paper, and the leading edge of the paper is detected. After the leading edge of the paper is detected, the roll Pr switches to the forward direction (CCW) indicated by arrow D2, and the leading edge of the paper is transported to the paper feed unit in the transport direction indicated by arrow D1.

[0040] Next, the control of the functions of the sheet transport device will be described. FIG. 5 is a functional block diagram illustrating an example of functions of the sheet conveying device according to an embodiment. The control unit 110 controls the entire sheet conveying device. 5 shows an example of a functional block in which the control unit 110 controls the sensor 93, the operation panel 170, and the motor drive circuit units 120 and 140, and other functional blocks are omitted. The functions of control unit 110 may be configured to be executed by control unit 100 (see FIG. 2), which controls the entire image forming apparatus. Similarly, operation panel 170, which receives input from the user, may also be configured to function as an operation panel for the image forming apparatus.

[0041] The control unit 110 includes, for example, a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), and the like. The CPU executes various programs and controls the entire image processing apparatus based on arithmetic processing and control programs. RAM is a volatile storage medium for reading and writing information at high speed, and functions as a work area when the CPU executes programs. The ROM is a read-only non-volatile storage medium that stores various programs and control programs.

[0042] The motor drive circuit unit 120 drives the motor under the control of the control unit 110 to drive the roll drive unit 130 . The roll driving unit 130 rotates the roll in a forward or reverse direction and is, for example, a roll rotation motor. The motor drive circuit unit 140 drives the motor under the control of the control unit 110 to drive the transport drive unit 150 . The transport drive unit 150 drives the transport unit 160 . The conveying section 160 is a conveying means for conveying the paper, and is, for example, a pair of conveying rollers 6.

[0043] Figure 6 is an explanatory diagram showing an example of the configuration of a guide member provided in the sheet conveying device of this embodiment, where Figure 6(A) is an oblique view explaining an example of a guide member 91, Figure 6(B) is a schematic diagram showing the appearance of a sensor 93, and Figure 6(C) is a side view explaining an example of an actuator and side plate that constitute the sensor 93. The sensor 93 is preferably disposed downstream of the roller member 92 in the direction in which the leading edge of the paper is fed to the paper feed section.

[0044] The sensor 93 uses, for example, an encoder sensor in which a slit 932 is provided in an actuator 931. The actuator 931 is disposed between two side plates 933 that form the housing of the sensor, and a shaft 934 is fitted into a bearing of the side plate 933, and the actuator 931 rotates around the shaft 934. The actuator 931 has, for example, an asymmetric shape with respect to the shaft 934, as shown in FIG. 6(C). The sensor 93 has a light-emitting unit and a light-receiving unit (not shown), and detects the leading edge of the roll Pr by counting the number of times light passes through the slit 932 of the actuator 931 from the light-emitting unit to the light-receiving unit (by counting the number of signal waveforms).

[0045] In the configuration example shown in Figure 6(A), two roller members 92 are arranged in the width direction of the guide member 91, and the sensor 93 is arranged between one roller member 92 and the other roller member 92 in the width direction of the guide member 91. In this way, by arranging two or more roller members 92 in the width direction of the guide member 91 and placing the sensor 93 between them, it is possible to reliably prevent the leading edge of the paper from floating on the roll Pr, and to prevent the output of the sensor 93 from becoming unstable depending on the thickness, stiffness, and curl of the paper P, thereby enabling the leading edge of the paper to be reliably detected. Furthermore, since the roller member 92 and the sensor 93 are arranged offset in the circumferential direction of the roll Pr, even if there is a partial scratch or the like, the proportion of the scratch affecting both the roller member 92 and the sensor 93 is reduced, making the configuration less prone to false detection.

[0046] 7A and 7B are diagrams illustrating an example of an operation for detecting the leading edge 97 of the paper sheet, and FIG. 8A and 8B are diagrams illustrating differences due to the positional relationship between the roller member 92 and the sensor 93. Figure 7 shows the process by which the leading edge 97 of the paper passes through the roller member 92 and the sensor 93, with Figure 7(A) showing the state before the leading edge 97 of the paper passes through the roller member 92, Figure 7(B) showing the state before the leading edge 97 of the paper passes through the roller member 92 and passes through the sensor 93, and Figure 7(C) showing the state after the leading edge 97 of the paper has passed through the sensor 93. 8A shows a case where roller member 92 is located downstream of sensor 93 in the direction in which the leading edge of the paper is supplied to the paper feed section, and FIG. 8B shows a case where roller member 92 is located upstream of sensor 93. FIG. 8 also shows the difference in the occurrence of paper slack 98 during leading edge detection operation.

[0047] The sensor 93 and the roller member 92 are positioned adjacent to each other with an offset (offset in the circumferential direction of the roll), and since the roller member 92 is located upstream of the sensor 93, the roller member 92 can hold down the leading edge of the paper until just before the leading edge of the paper is detected by the sensor 93 (Figure 7(A)). As shown in Figure 7(B), when the leading edge 97 of the paper passes the roller member 92, the guide member 91 moves in the direction of the arrow D6. Then, the actuator of the sensor 93 moves in the direction of the arrow D5. As shown in Figure 7(C), when the leading edge 97 of the paper passes the sensor 93, the actuator of the sensor 93 moves in the direction of the arrow D7. This makes it possible to detect the area on the roll surface with a step (difference equivalent to the paper thickness) as the tip of the paper while the tip of the sensor 93 is in close contact with the surface of the roll Pr. Therefore, the output (detection result) of the sensor 93 does not become unstable depending on the thickness, stiffness, or curl of the paper, and the sensor 93 can reliably detect the tip of the paper on the roll Pr.

[0048] In this embodiment, the roller member 92 is arranged upstream of the sensor 93, but detection is also possible in the reverse arrangement (FIG. 8(A)). However, it is preferable to arrange the roller member 92 upstream of the sensor 93, as this makes it possible to more reliably prevent the leading edge of the paper from floating until just before detection. In addition, by providing two roller members 92 as shown in Figure 6 and placing a sensor 93 between the two roller members 92, it is possible to more reliably prevent the leading edge of the paper from floating or sagging than when there is only one roller member 92.

[0049] Furthermore, in the sheet conveying device of this embodiment, the roller member 92 and the sensor 93 are arranged offset in the circumferential direction of the roll Pr, so even if there is a partial scratch or the like, the proportion of it affecting both the roller member 92 and the sensor 93 is reduced. FIG. 9(A) shows a state in which the sensor 93 is in contact with a concave scratch on the roll surface. 9(A), concave scratches are generally not detected because the tip of sensor 93 is generally larger and the edge of the scratch is not as sharp as the tip of the paper. By making the shape of the actuator of sensor 93 larger than the concave scratch, such scratches are not mistakenly detected as the edge of the paper, ensuring detection accuracy.

[0050] FIG. 9(B) shows an example of a signal waveform when the leading edge of a sheet of paper is detected, and FIG. 9(C) shows an example of a signal waveform when a convex scratch is detected. In the arrangement of roller member 92 and sensor 93 shown in FIG. 6A, normal detection of the leading edge of a sheet (when the leading edge of a sheet passes sensor 93) results in a signal waveform as shown in FIG. 9B. On the other hand, if there is a band-shaped convex scratch or the like on the surface of the roll Pr, the signal waveform will be as shown in FIG. 9(C). Therefore, the control unit 110 can distinguish between the signal waveform of the normal detection of the leading edge of the paper and the signal waveform caused by a convex scratch in the detection results of the sensor 93, and can prevent erroneous detection.

[0051] As shown in Figures 4 to 9, in the sheet conveying device of this embodiment, when detecting the leading edge of the paper on the roll Pr, the sensor output does not become unstable depending on the thickness, stiffness, or curl state of the paper, and detection accuracy is ensured.

[0052] Next, detection of the leading edge of the paper based on the sensor displacement output and detection of the roll diameter will be described with reference to FIGS. The transport device according to the present invention controls the rotation speed (number of rotations) of the roll Pr when supplying the leading edge of the paper to the paper feed unit in accordance with the sensor displacement output. In detail, the leading edge of the paper is detected by the sensor displacement output, and the roll diameter of the roll Pr is detected from the sensor displacement output per unit time, and the rotation speed (number of rotations) of the roll Pr when supplying the leading edge of the paper to the paper feed section is controlled according to the value of the roll diameter. More specifically, the leading edge of the paper is detected by the sensor displacement output per unit time, and a threshold value for the sensor displacement output per unit time is set to detect the size of the roll diameter of the roll Pr, and the rotation speed (number of rotations) of the roll Pr when supplying the leading edge of the paper to the paper feed section is controlled according to the obtained roll diameter value.

[0053] Furthermore, the conveying device according to the present invention can detect the thickness of the paper P according to the sensor displacement output.

[0054] Furthermore, the operation of detecting the diameter of the roll Pr can be performed at any timing. After the roll diameter is detected, the operation of feeding the leading edge of the paper to the paper feed unit is performed. The current roll diameter of the roll Pr can be calculated from the roll diameter and the thickness of the paper P detected according to the sensor displacement output per unit time, and the integrated amount of rotation of the roll Pr.

[0055] FIG. 10 is an explanatory diagram showing the relationship between the position of the paper tip on the roll and the change in the sensor output signal, and FIG. 11 is an explanatory diagram showing the details of the change in the sensor signal. As shown in Figure 10(A), the sensor output signals obtained when the leading edge 97 of the paper passes the roller member 92 (up to dashed line A) are designated as "I," the leading edge 97 of the paper passes the roller member 92 and before it passes the sensor 93 (from dashed line A to dashed line B) are designated as "II," and the leading edge 97 of the paper passes the sensor 93 (after dashed line B) are designated as "III." are shown in Figure 10(B).

[0056] To detect the leading edge of the paper, first, roll Pr is rotated in the reverse direction (CW) in the direction D3, and the sensor displacement output K1 per unit time is detected when the leading edge of the paper passes roller member 92 (dashed line A), and the sensor displacement output K2 per unit time when the leading edge of the paper passes sensor 93 (dashed line B). The leading edge of the paper is detected by detecting K1 and K2. After detecting the sensor displacement output K1, if the sensor displacement output K2 is detected continuously within a set time (T1), it is determined that the leading edge of the paper has been detected, thereby preventing false detection due to scratches on the uneven surface of the roll Pr. T1 can be expressed by the following formula: T1 = (circumferential distance from the roller to the sensor (mm)) ÷ (linear speed of the leading edge of the paper (mm / s)) + (setting margin) The paper leading edge linear speed can also be expressed as the number of motor revolutions (rotational speed).

[0057] If the leading edge of the paper is not detected during one rotation of the roll Pr, the same detection operation can be repeated a predetermined number of times, and the number of repetitions can be set to improve detection accuracy. The flow of the detection operation will be described later.

[0058] Furthermore, in a configuration in which two or more roller members 92 are arranged along the roll axis direction as shown in Figure 6(A), if the leading edge of the paper to be detected is oblique to the roll axis direction, there will be a difference in the timing at which the leading edge of the paper passes each roller member 92, which may make it difficult to detect the sensor displacement output K1. In such a case, if the leading edge of the paper is not detected even after repeating the detection operation a predetermined number of times, the detection accuracy can be improved by detecting only the sensor displacement output K2 when the leading edge of the paper passes through sensor 93.

[0059] Furthermore, when detecting the leading edge of the paper solely by detecting the sensor displacement output K2, the leading edge of the paper is deemed to have been detected if the sensor displacement output K2 is detected again within a certain time range (T2) corresponding to one rotation of the roll after the first K2 detection, and by making it possible to set the number of detection operations as desired, the detection accuracy can be improved.

[0060] After detecting the leading edge of the paper, the leading edge of the paper is stopped at the leading edge stop position indicated by symbol S in Figure 4, and then the paper moves to the forward rotation (CCW) operation indicated by D2, thereby suppressing variations in the posture in which the leading edge of the paper is inserted into the entrance guide plate 95, and allowing the paper to be transported stably to the paper feed section regardless of the paper condition (curl / paper type / paper thickness).

[0061] FIG. 12 is an explanatory diagram showing the relationship between the roll diameter and the amount of change in the sensor signal. Fig. 12(A) is an explanatory diagram showing the size of the roll diameter of the roll Pr, Fig. 12(B) shows the change in the sensor signal when the roll diameter is large, Fig. 12(C) shows the change in the sensor signal when the roll diameter is small, and Fig. 12(D) is a table showing an example of roll diameter detection (calculation) using threshold values.

[0062] When the roll Pr is rotated at a constant rotational speed (number of rotations, rpm), the moving speed (mm / s) of the leading edge of the paper varies depending on the diameter of the roll. 12(B) and 12(C), the amount of change in the sensor displacement outputs K1 and K2 per unit time varies depending on the moving speed (mm / s) of the paper leading edge. Therefore, by setting a threshold value for the sensor displacement output, it is possible to detect the size of the roll diameter. As shown in FIG. 12(D), the value x of the roll diameter can be calculated using the following formula 1 or 2. x=(K1+K2) / 2...Equation 1 x=K2...Equation 2 Although it is possible to distinguish between large and small diameters by setting one threshold, it is also possible to set multiple thresholds. By setting multiple thresholds, it is possible to distinguish between roll diameters in more detail. For example, the obtained roll diameter x can be determined as small when x<1, as medium when 1≦x<2, and as large when 2≦x.

[0063] The transport speed when transporting the paper to the paper feed unit after the paper leading edge detection operation, that is, the rotation speed (number of rotations) of the roll Pr, can be controlled according to the obtained value of the roll diameter. Regardless of the size of the roll diameter, by keeping the paper transport speed constant, it becomes possible to transport the paper stably.

[0064] In addition, the roll Pr is rewound (CW) for each print job in the image forming unit, the roll diameter is detected, and then the roll is rotated forward (CCW) again to perform the paper transport operation, thereby making it possible to detect the amount of paper remaining before printing is performed.

[0065] FIG. 13 is an explanatory diagram showing the relationship between the thickness of the paper and the sensor signal displacement (pulse). Since the sensor signal displacement (pulse) varies depending on the thickness of the paper, the paper thickness can be detected by setting a threshold value for the sensor displacement output. As shown in FIG. 13, for example, when y<0.6, it is thin paper, when 0.6≦y<0.9, it is normal paper, and when 0.9≦y, it is thick paper. Since paper thickness setting is necessary for setting printing conditions in the image forming unit, if it can be detected automatically, it will eliminate the need for users to manually set paper thickness via an operation panel or the like.

[0066] Furthermore, the current roll diameter of the roll Pr can be calculated using the roll diameter and the thickness of the paper P detected according to the sensor displacement output per unit time, and the integrated amount of rotation of the roll Pr. The control unit counts the rotation amount of the roll Pr, obtains the cumulative rotation amount (total rotation amount), and calculates the roll diameter using the roll diameter value obtained during the paper tip detection operation and the paper thickness, for example, using the formula shown below. (Current roll diameter) = (roll diameter x) - (paper thickness) x 2 - (total roll rotations) The roll diameter x is a value calculated by (K1+K2) / 2.

[0067] 14 to 16 are flowcharts illustrating an example of an operation for setting a roll Pr in a sheet conveying device according to an embodiment of the present invention. Note that the symbols in the flowchart are explained in FIG. Figure 14 is a flowchart showing the overall flow. When the control unit 110 detects that the roll Pr has been set in the sheet conveying device (for example, detected by the detection result of the sensor 93) (S001), it controls the motor drive circuit unit 120 and controls the roll drive unit 130 to reverse the roll Pr. The roll rotation motor (roll driving unit 130) rotates the roll Pr in the rewinding direction by a reverse operation (S002), and the sensor 93 starts the leading edge detection operation (S003).

[0068] It is determined whether the leading edge detection has been completed (S004), and if the paper leading edge detection operation is to be performed, the flow in Fig. 15 connected by connector A is performed. The detailed flow of the paper leading edge detection operation is shown in Fig. 15 and Fig. 16, and the flow is connected by connector B and returns to this flow. Once the paper leading edge detection is complete, under the control of the control unit 110, the motor drive circuit unit 120 stops the roll rotation motor at the paper leading edge stop position (S005), and then controls the roll drive unit 130 to rotate the roll Pr forward (S006). The rotation speed (number of rotations) of the roll rotation motor in step S006 is variable depending on the roll diameter detected in the paper leading edge detection operation. A paper transport operation is performed to transport the paper P unwound from the roll Pr rotating at the controlled rotation speed to the paper feed unit (S007). The motor drive circuit unit 140 rotates the transport unit 160 to transport the paper into the device.

[0069] FIG. 15 shows a detailed flow of the paper leading edge detection operation connected by a connector A from step S004 in FIG. First, the process starts with the paper leading edge detection count N=0 (S101), and determines whether the sensor displacement output K1 is detected (S102). After detecting K1, it determines whether K2 is detected within T1 (S103). "T1" is the time it takes for the paper leading edge to move, calculated based on the motor rotation speed and the distance from the roller member to the sensor, plus a set margin. If K2 is detected, the roll diameter is detected from K1 and K2 (S104), and the number of times N of paper leading edge detection is incremented by 1 (S105).

[0070] Next, it is determined whether the number of times N of detections of the leading edge of the paper is equal to or greater than a set value a (S106). "a" is the reference value of the number of detections to determine that the leading edge of the paper has been detected successfully (how many times detections are required to determine that detection has been successful). If N is equal to or greater than a, it is determined that the leading edge of the paper has been successfully detected (S107). The roll diameter is calculated based on the values ​​of the sensor displacement outputs K1 and K2, and the size of the roll diameter is determined based on a preset threshold (S108). The flow from this point onwards is connected to step S005 in Fig. 14 by connector B. Depending on the value of the roll diameter obtained in step S108, the rotation speed of the roll when feeding the leading edge of the paper to the paper feed unit in step S006 in Fig. 14 is controlled.

[0071] On the other hand, if N is less than a in step S106, it is determined whether K1 is detected again within T2 after K1 is detected (S109). "T2" is the time for one rotation of the roll calculated based on the motor rotation speed plus a set margin. If K1 is detected, it is then determined whether K2 is detected within T1 (S110).If K2 is detected, the number of times the leading edge of the paper is detected is incremented by one (S105).

[0072] If K1 is not detected in step S109, if K2 is not detected in step S110, or if K2 is not detected in step S103, it is determined whether the roll has rotated R times or more (S111), where "R" is the set value for the number of roll rotations (how many times the roll must rotate before the leading edge of the paper is detected). If the cumulative number of rotations is less than R, the flow returns to step S102 again. On the other hand, if the cumulative number of rotations is R or more, the flow in FIG.

[0073] FIG. 16 shows a detailed flow of the paper leading edge detection operation connected by a connector E from step S111 in FIG. First, the process starts again from the leading edge detection count N=0 (S201), and determines whether the sensor displacement output K2 is detected (S202). If K2 is detected, the roll diameter is detected from K2 (S203). If K2 is detected, the paper leading edge detection count N is incremented by 1 (S204).

[0074] Next, it is determined whether the number of times N of detections of the leading edge of the paper is equal to or greater than a set value a (S205). "a" is the reference value of the number of detections to determine that the leading edge of the paper has been detected successfully (how many times detections are required to determine that detection has been successful). If N is equal to or greater than a, it is determined that the leading edge of the paper has been detected successfully (S206). The roll diameter is calculated based on the value of the sensor displacement output K2, and the roll diameter is determined from a preset threshold (S207). The subsequent flow is connected to step S005 in Fig. 14 by a connector B. Depending on the value of the roll diameter obtained in step S206, the rotation speed of the roll when feeding the leading edge of the paper to the paper feed unit in step S006 in Fig. 14 is controlled.

[0075] On the other hand, if N is less than a in step S204, it is determined whether K2 is detected again within T2 after K2 is detected (S208). "T2" is the time taken for one rotation of the roll calculated based on the motor rotation speed plus a set margin. If K2 is detected, the number of times the paper leading edge is detected is incremented by one (S204), and the process returns to the subsequent flow.

[0076] If K2 is not detected in step S208, or if K2 is not detected in step S202, it is determined whether the roll has rotated R times or more (S209), where "R" is the set value for the number of roll rotations (how many times the roll must rotate before the leading edge of the paper is detected). If the cumulative number of rotations is less than R, the flow returns to step S202. On the other hand, if the cumulative number of rotations is equal to or greater than R, it is determined that detection of the leading edge of the paper sheet has failed, and the roll rotation motor is stopped (S210).

[0077] As described above, by using the sheet conveying device of the present invention, in an image forming device that feeds rolled paper, the user can simply set the roll, and the leading edge of the paper on the roll can be automatically and reliably detected, and the unwound paper can be stably transported to the paper feed section. [Explanation of symbols]

[0078] 6 Transport roller pair 80 Image forming device 90 Sheet transport device 91 Guide member 92 Roller member 93 Sensors 95 Entrance guide plate 110 control section 911 Rotation center Pr(Pa, Pb) roll P paper [Prior art documents] [Patent documents]

[0079] [Patent Document 1] Japanese Patent Application Laid-Open No. 2018-150107

Claims

1. A sheet conveying device that supplies a sheet of paper from a roll formed by winding the sheet of paper to a paper feeding unit, a sensor capable of detecting a stepped portion on the surface of the roll as the leading edge of the paper; a roller member that is disposed at a position different from the sensor in the circumferential direction of the roll and presses the leading edge of the paper; a guide member that supports the sensor and the roller member so that they contact the surface of the roll, Two or more roller members are arranged in the width direction of the guide member, the sensor is disposed between one of the roller members and the other of the roller members in the width direction of the guide member, A sheet transport device, characterized in that the rotation speed of the roll when supplying the leading edge of the paper to the paper feed unit is controlled in accordance with a sensor displacement output.

2. A sheet conveying device that supplies sheet-shaped paper from a roll formed by winding the sheet to a paper feed section, a sensor capable of detecting the leading edge of the paper roll; a roller member disposed at a position different from the sensor in the circumferential direction of the roll; a guide member that supports the sensor and the roller member so that they contact the surface of the roll, A sheet conveying device characterized in that a thickness of the paper is detected in accordance with a sensor displacement output, and the rotation speed of the roll when the leading edge of the paper is fed to the paper feed section is controlled.

3. The leading edge of the paper is detected based on a sensor displacement output, and the roll diameter of the roll is detected based on the sensor displacement output per unit time.

3. The sheet conveying device according to claim 1, wherein the rotation speed of the roll when supplying the leading edge of the paper to the paper feed unit is controlled in accordance with the value of the roll diameter.

4. 4. The sheet conveying device according to claim 1, wherein the thickness of the sheet is detected in accordance with the displacement output of the sensor.

5. A sheet conveying device as described in any one of claims 1 to 4, characterized in that an operation is performed to detect the roll diameter of the roll at any timing after the roll paper is set, and then an operation is performed to supply the tip of the paper to the paper feeding section.

6. A sheet conveying device as described in any one of claims 2, 4 and 5, characterized in that the current roll diameter of the roll is calculated using the roll diameter and paper thickness of the paper detected according to the sensor displacement output per unit time and the cumulative amount of rotation of the roll.

7. 7. The sheet conveying device according to claim 1, wherein the sensor is disposed downstream of the roller member in a direction in which the leading edge of the sheet is fed to a sheet feeding unit.

8. 8. The sheet conveying device according to claim 1, wherein the sensor is an encoder sensor.

9. 9. The sheet conveying device according to claim 1, wherein the guide member is a member that guides the paper peeled off from the roll to the paper feed unit.

10. A sheet conveying device as described in any one of claims 1 to 9, characterized in that an entrance guide plate is further provided upstream of the pair of rollers provided in the paper feeding section in the direction in which the leading edge of the paper is supplied to the paper feeding section.

11. An image forming apparatus comprising the sheet conveying device according to any one of claims 1 to 10.

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