Paper feeder, paper feed method, program and image formation apparatus

Abstract

To provide a paper feeder, a paper feed method, a program and an image formation apparatus which can increase the detection accuracy of a roll end.SOLUTION: This invention is a paper feeder which rotates roll paper forward and backward to feed the roll paper. The paper feeder comprises: a roller; a sensor which detects a step at an end part of the roll paper; a support member which arranges the sensor and the roller at positions mutually offset in the circumferential direction of the roll paper toward almost the center of the roll paper and supports the sensor and the roller so as to be abutted against a surface of the roll paper; and a control unit which controls the rotation of the roll paper based on sensor signals outputted from the sensor. The control unit rotates the roll paper in a paper feed direction, and compares the slope of a change in the sensor signals and a threshold value to detect a paper tube of the roll paper.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present invention relates to a paper feeding device, a paper feeding method, a program, and an image forming apparatus. [Background technology]

[0002] A roll end detection technology has been developed to detect the rear end (roll end) of roll paper in a roll paper feeder that feeds and transports roll paper. A technology has also been developed that uses a sensor that can directly detect the thickness of the roll paper to detect the step between the roll paper and the paper core at the end of the roll and detects the roll end. Patent Document 1 discloses a technology that brings a roller into contact with the surface of the roll paper and detects the roll end with a sensor by detecting unevenness in the rotation of the roller, or detects the roll end based on changes in the current value of the motor that drives the roller. Summary of the Invention [Problem to be solved by the invention]

[0003] However, the above-mentioned roll end detection technology does not directly detect the rear end of the paper, so there is a possibility of false detection of the roll end. Also, with the above-mentioned roll end detection technology, since the surface of the paper core of the roll paper is rough, if a convex or concave portion comes just after the roll end, the change in the signal output from the sensor may be small, and the roll end may not be detected. For example, when the step portion of the roll end passes the actuator of the sensor, the surface just after the roll end becomes smooth, and the signal from the sensor does not obtain a large change that exceeds the threshold value, and the change becomes small.

[0004] Also, if the center of the roll paper is secured with tape, when the roll paper becomes long, the sensor position will be at the edge of the roll paper to accommodate roll paper of multiple widths. In that case, the edge of the roll paper may float, and the sensor signal may become unstable. For example, when the rear end of the roll paper floats, there is no problem because the sensor actuator changes suddenly, but if the rear end of the roll paper is curved and makes contact, there is no large change in the sensor signal as it passes the sensor actuator, and it becomes small.

[0005] The present invention has been made in view of the above, and an object of the present invention is to provide a paper feeding device, a paper feeding method, a program, and an image forming apparatus that can improve the accuracy of detecting the roll end. [Means for solving the problem]

[0006] In order to solve the above-mentioned problems and achieve the object, the present invention provides a paper feeding device that rotates roll paper forward and backward and feeds the roll paper, comprising a roller, a sensor that detects steps at the end of the roll paper, a support member that positions the sensor and the roller at positions offset from each other in the circumferential direction of the roll paper toward approximately the center of the roll paper and supports the sensor and the roller so that they abut against the surface of the roll paper, and a control unit that controls the rotation of the roll paper based on a sensor signal output from the sensor, and the control unit rotates the roll paper in the feed direction and detects the paper core of the roll paper by comparing the slope of the change in the sensor signal with a threshold value. Effect of the Invention

[0007] Advantageous Effects of Invention According to the present invention, there is an effect that the accuracy of detecting the roll end can be improved. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a perspective view of a schematic configuration example of an image forming apparatus according to the present embodiment. [Diagram 2]FIG. 2 is a side cross-sectional view of the image forming apparatus according to the present embodiment. [Diagram 3] FIG. 3 is a side view illustrating a main part of an example of the configuration of the sheet feeding device according to the present embodiment. [Figure 4] FIG. 4 is a functional block diagram illustrating an example of functions of the sheet feeding device according to the present embodiment. [Diagram 5] FIG. 5 is a flowchart illustrating an example of the operation of setting roll paper in the paper feeder of this embodiment. [Figure 6] FIG. 6 is a diagram for explaining a configuration example of the arm according to the present embodiment. [Figure 7] FIG. 7 is a diagram illustrating an example of the operation of detecting the leading edge of the roll paper in the paper feeder according to the present embodiment. [Figure 8] FIG. 8 is a diagram for explaining an example of the relationship between the rollers, the sensor, the leading edge position of the roll paper, and changes in the sensor signal in the paper feeder according to the present embodiment. [Figure 9A] FIG. 9A is a diagram for explaining an example of the relationship between the rollers, the sensor, the leading edge position of the roll paper, and changes in the sensor signal in the paper feeder according to the present embodiment. [Figure 9B] FIG. 9B is a diagram for explaining an example of the configuration for automatic feeding of roll paper in the paper feeder according to the present embodiment. [Figure 10] FIG. 10 is a diagram showing an example of a state at the end of the roll when the rear end of the roll paper is glued in the paper feeder according to the present embodiment. [Figure 11] FIG. 11 is a diagram showing an example of a paper passing state when the rear end of the roll paper is secured with tape in the paper feeder according to the present embodiment. [Figure 12] FIG. 12 is a diagram for explaining an example of the roll paper feeding operation in the paper feeding device according to the present embodiment. [Figure 13] FIG. 13 is a diagram showing an example of the relationship between the rollers, the sensor, and the rear end position of the roll paper in the paper feeder according to the present embodiment and changes in the sensor signal. [Figure 14]FIG. 14 is a diagram showing an example of the relationship between the rollers, the sensor, and the rear end position of the roll paper in the paper feeder according to the present embodiment and changes in the sensor signal. [Figure 15] FIG. 15 is a flowchart showing an example of the flow of the roll end detection operation in the paper feeder according to the present embodiment. [Figure 16] FIG. 16 is a diagram showing an example of a detailed relationship between the rollers, the sensor, the rear end position of the roll paper, and changes in the sensor signal in the paper feeder according to the present embodiment. [Figure 17] FIG. 17 is a diagram showing an example of a detailed relationship between the rollers, the sensor, the rear end position of the roll paper, and changes in the sensor signal in the paper feeder according to the present embodiment. [Figure 18] FIG. 18 is a diagram showing an example of roll paper fed by the paper feeder according to the present embodiment. [Figure 19] FIG. 19 is a diagram showing an example of roll paper fed by the paper feeder according to the present embodiment. [Figure 20] FIG. 20 is a diagram showing an example of roll paper fed by the paper feeder according to the present embodiment. [Figure 21] FIG. 21 is a diagram showing an example of roll paper fed by the paper feeder according to the present embodiment. [Figure 22] FIG. 22 is a diagram for explaining an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 23A] FIG. 23A is a diagram illustrating an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 23B] FIG. 23B is a diagram for explaining an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 23C] FIG. 23C is a diagram illustrating an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 24] FIG. 24 is a diagram for explaining an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 25A] FIG. 25A is a diagram illustrating an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 25B] FIG. 25B is a diagram for explaining an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 25C] FIG. 25C is a diagram illustrating an example of the operation of detecting the edge of the roll paper in the paper feeding device according to the present embodiment. [Figure 26] FIG. 26 is a diagram for explaining an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 27A] FIG. 27A is a diagram illustrating an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 27B] FIG. 27B is a diagram for explaining an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 27C] FIG. 27C is a diagram illustrating an example of the operation of detecting the edge of the roll paper in the paper feeding device according to the present embodiment. [Figure 28A] FIG. 28A is a diagram illustrating an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 28B] FIG. 28B is a diagram for explaining an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 28C] FIG. 28C is a diagram illustrating an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 29A] FIG. 29A is a diagram illustrating an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 29B] FIG. 29B is a diagram for explaining an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 29C] FIG. 29C is a diagram illustrating an example of the operation of detecting the edge of the roll paper in the paper feeding device according to the present embodiment. [Diagram 30] FIG. 30 is a diagram for explaining an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 31A] FIG. 31A is a diagram illustrating an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 31B] FIG. 31B is a diagram for explaining an example of the operation of detecting the edge of the roll paper in the paper feeder according to the present embodiment. [Figure 31C] FIG. 31C is a diagram illustrating an example of the operation of detecting the edge of the roll paper in the paper feeding device according to the present embodiment. [Figure 31D] FIG. 31D is a diagram for explaining an example of the operation of detecting the edge of the roll paper in the paper feeding device according to the present embodiment. [Diagram 32] FIG. 32 is a schematic diagram showing an example of a change in the sensor signal on the surface of the roll paper in the paper feeder according to the present embodiment. [Diagram 33] FIG. 33 is a schematic diagram showing an example of a change in the sensor signal at the edge of the roll paper in the paper feeder according to the present embodiment. [Diagram 34] FIG. 34 is a schematic diagram showing an example of fluctuation in the slope of a signal change in the paper feeder according to the present embodiment. [Diagram 35] FIG. 35 is a diagram for explaining an example of a method for comparing the magnitude of the gradient of the signal change in the paper feeder according to the present embodiment. [Diagram 36] FIG. 36 is a diagram for explaining an example of a method for comparing the magnitude of the gradient of the signal change in the paper feeder according to the present embodiment. [Figure 37] FIG. 37 is a diagram showing an example of the gradient of the paper surface signal fluctuation when a foreign object is present on part of the surface of the roll paper in the paper feeder according to this embodiment. [Figure 38] FIG. 38 is a flow chart showing an example of the flow of the operation of detecting the roll end of the roll paper in the paper feeder according to the present embodiment. [Figure 39]FIG. 39 is a flowchart showing an example of the flow of the paper tube detection operation in the paper feeder according to the present embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of a paper feeder, a paper feed method, a program, and an image forming apparatus will be described in detail with reference to the accompanying drawings.

[0010] An example of the configuration of an image forming apparatus to which a paper feeder according to the present embodiment is applied will be described with reference to Figures 1 and 2. The image forming apparatus according to the present embodiment is an inkjet printer that prints on a recording medium by ejecting ink droplets corresponding to image data, but the present invention can also be applied to copying machines and printers of an electrophotographic system or the like that transport a recording medium and print.

[0011] Fig. 1 is a perspective view of a schematic configuration example of an image forming apparatus according to the present embodiment. Fig. 2 shows a side cross-sectional view of the image forming apparatus according to the present embodiment, and explains the overall configuration of the image forming apparatus according to one embodiment and the operation of the main parts. In Fig. 1, the arrows X indicate the depth direction (front-rear direction) of the image forming apparatus 80, Y indicate the width direction (main scanning direction) of the image forming apparatus 80, and Z indicate the up-down direction.

[0012] 1, image forming apparatus 80 is a serial type liquid ejection type (ink ejection type) image forming apparatus, and a main body housing 81 is disposed on a main body frame 82. In image forming apparatus 80, a main guide rod 64 and a sub guide rod 65 are stretched across the main scanning direction indicated by double arrow Y in Fig. 1 within main body housing 81. Main guide rod 64 movably supports carriage 66, and carriage 66 is provided with a connecting piece 66a that engages with sub guide rod 65 to stabilize the position of carriage 66.

[0013] In the image forming device 80, an endless belt-like 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 rotationally driven 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 rotationally driven by the main scanning motor 70, thereby rotating and moving the timing belt 67 in the main scanning direction according to the rotation direction of the main scanning motor 70.

[0014] The carriage 66 is connected to a timing belt 67, and as the timing belt 67 is rotated in the main scanning direction by a drive pulley 68, the carriage 66 reciprocates in the main scanning direction along the main guide rod 64.

[0015] 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 that respectively store yellow (Y), magenta (M), cyan (C), and black (K) ink. Each cartridge in cartridge unit 71 is connected by a pipe to the recording head of the corresponding color mounted on carriage 66, and ink is supplied from cartridge unit 71 to the recording head of each color through the pipe.

[0016] The image forming device 80 records an image on the paper P by ejecting ink onto the paper P, which is intermittently transported in a sub-scanning direction (the direction of arrow X in FIG. 1) perpendicular to the main scanning direction over a platen (plate) 74 (see FIG. 2) while moving the carriage 66 in the main scanning direction.

[0017] The paper P is not limited to paper, and various types such as rolled film can be used. However, in the following explanation, for clarity, the paper being transported will be referred to as paper P, the rolled state of paper P will be referred to as roll paper Pr (Pa, Pb), and the core tube (core portion or paper tube) of roll paper Pr will be referred to as Ps.

[0018] As shown in FIG. 2, the image forming apparatus 80 has a chamber 75 with a fan disposed below the platen 74, and by driving the fan, the paper P transported over the platen 74 is transported in close contact with the platen 74.

[0019] 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, the carriage 66 is moved in the main scanning direction and ink is ejected from the nozzle row 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 (roll paper) Pr.

[0020] The maintenance mechanism 72 cleans the ejection surface of the print head, caps it, ejects unnecessary ink, etc., in order to remove unnecessary ink from the print head and maintain the reliability of the print head.

[0021] In the image forming device 80, an encoder sheet is disposed parallel to the timing belt 67 and the main guide rod 64, at least over the movement range 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 result of reading the encoder sheet by the encoder sensor.

[0022] 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.

[0023] In the image forming apparatus 80, as shown in FIGS. 1 and 2, a main body frame 82 supporting a main body housing 81 is provided with two spool bearing pedestals 5a and 5b in the vertical direction in FIGS.

[0024] Paper (rolled paper) P pulled out from the leading end of roll paper Pr set on spool bearing pedestals 5a, 5b is transported in transport path 9 by transport roller pairs 6a, 6b, registration roller 10, and registration pressure roller 17, as shown by the arrows in Fig. 2. Controller 100 controls drive device 7 to rotate transport roller pairs 6a, 6b, registration roller 10, registration pressure roller 17, etc. Roll paper receiving stands 8a, 8b are provided below roll paper Pr (Pa, Pb) to prevent roll paper Pr from falling.

[0025] 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 at a reversing unit 19.

[0026] 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.

[0027] In order 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 cuts the paper P to a predetermined length by being moved in the main scanning direction Y by the drive motor. The cut paper P is discharged to the discharge section. Note that although an example of the configuration of an image forming apparatus in which rolled paper Pa, Pb can be set on two spool bearing pedestals 5a, 5b is shown in FIGS. 1 and 2, an image forming apparatus having one spool bearing pedestal may also be used. Also, in the above explanation, the configuration corresponding to the two rolled paper Pa, Pb was described using identifiers a, b (for example, spool bearing pedestals 5a, 5b), but hereinafter, the identifiers a, b will not be described unless a distinction is made.

[0028] FIG. 3 is a side view illustrating the main parts of an example of the configuration of a paper feeder according to the present embodiment. Paper feeder 90 is an example of a paper feeder that rotates roll paper Pr forward or backward (forward and reverse rotation) to feed roll paper Pr. In this embodiment, paper feeder 90 includes at least an arm 91, a roller 92, a sensor 93, and a pair of transport rollers 6 as a transport section. Paper feeder 90 may further include an entrance guide plate 95. In FIG. 3, the position of roll paper Pr when the user sets roll paper Pr in paper feeder 90 is indicated by a dashed line. Roll paper Pr is held by a module component so as to be rotatable around the center (axis) of the roll paper.

[0029] An arm (guide plate) 91 serving as a support member for roll paper Pr is configured to be rotatable about a rotation center 911. One side of the rotation center 911 of the arm 91 is pressed in the direction of the roll paper by a spring or the like. This ensures that the arm 91 comes into contact with the outer diameter of the roll paper even if the diameter of the roll paper changes. The outline arrow indicates the rotation direction of the arm 91. The arm 91 also has a roller 92 and a sensor 93 on the other side of the rotation center 911. As the arm 91 is pressed in the direction of the roll paper, it supports the roller 92 and sensor 93 so that they abut against the surface of the roll paper Pr.

[0030] The arm 91 acts as a guide plate that guides the paper feed direction of the roll paper Pr. The arm 91 is preferably shaped (for example, arc-shaped) so that the portion (end side) where the roll paper Pr is set conforms to the outer diameter of the roll paper Pr so that the roll paper Pr is held when the user sets it (so that it does not fall, etc.). The arm 91 also functions as the roll paper receiving trays 8a and 8b in FIG. 2. The arm 91 as a support member also serves as a guide plate that guides the roll paper, thereby reducing the number of parts and keeping costs down. The arm 91 is an example of a support member that positions the sensor 93 and the roller 92 at positions offset from each other in the circumferential direction of the roll paper Pr toward approximately the center of the roll paper Pr, and supports the sensor 93 and the roller 92 so that they abut against the surface of the roll paper Pr.

[0031] The rollers 92 and the sensor 93 are positioned so as to face approximately the center of the roll paper (so as to face the axial center of the roll paper) regardless of the diameter of the roll paper. The rollers 92 are positioned at a different position from the sensor 93 in the circumferential direction of the roll paper Pr, and the rollers 92 and the sensor 93 are positioned offset from each other in the circumferential direction. The sensor 93 is an example of a sensor with the detection accuracy to detect steps (paper thickness) at the ends (leading and trailing ends) of the roll paper Pr.

[0032] The entrance guide plate 95 guides the transport direction of the paper peeled off from the roll paper Pr. In the configuration example of Fig. 3, during paper feeding operation (when the roll paper Pr rotates forward), the arm 91 acting as a guide plate guides the paper on the upstream side of the paper transport direction, and the entrance guide plate 95 guides it on the downstream side.

[0033] Next, the control of the functions of the sheet feeding device 90 will be described. Fig. 4 is a functional block diagram illustrating an example of the functions of the sheet feeding device of this embodiment. The control unit 100 controls the entire sheet feeding device 90. Fig. 4 shows an example of a functional block in which the control unit 100 controls the sensor 93, the motor drive circuit units 120 and 140, and the display unit 170, and other functional blocks are omitted. The functions of the control unit 100 may be configured to be executed by the control unit 100 (see Fig. 2) that controls the entire image forming apparatus 80.

[0034] The control unit 100 includes, for example, a CPU (Central Processing Unit), a RAM (Random Access Memory), and a ROM (Read Only Memory). The CPU executes various programs and controls the entire image forming apparatus 80 based on arithmetic processing and control programs. For example, the control unit 100 is an example of a control unit that controls the rotation of the roll paper Pr based on a sensor signal output from a sensor 93. The RAM is a volatile storage medium for reading and writing information at high speed, and functions as a work area when the CPU executes a program. The ROM is a read-only non-volatile storage medium in which various programs and control programs are stored.

[0035] The motor drive circuit unit 120 drives a motor under the control of the control unit 100 to drive the roll paper drive unit 130. The roll paper drive unit 130 rotates the roll paper in a forward or reverse direction. The roll paper drive unit 130 uses, for example, a roll paper rotation motor. The motor drive circuit unit 140 drives a motor under the control of the control unit 100 to drive the transport drive unit 150. The transport drive unit 150 drives the transport unit 160. The transport unit 160 is a transport means that transports the roll paper Pr, and is, for example, a pair of transport rollers 6. In other words, the transport unit 160 is an example of a transport unit that rotates the roll paper Pr forward and reverse and feeds the roll paper Pr. The display unit 170 is an example of a display unit that displays the feed status of the roll paper Pr.

[0036] Here, an example of the process of detecting the edge of the roll paper Pr by the control unit 100 in the paper feeder according to the present embodiment will be described.

[0037] The control unit 100 rotates the roll paper Pr in the paper feed direction (forward direction, main scanning direction) and detects the paper tube Ps of the roll paper Pr by comparing the slope of the change in the sensor signal with the threshold value. This makes it possible to detect the difference between the surface of the roll paper Pr and the surface of the paper tube Ps, thereby improving the accuracy of roll end detection.

[0038] The control unit 100 may also detect the paper tube Ps by comparing the integrated value of the absolute value of the slope of the change in the sensor signal per predetermined time with the threshold value. This makes it resistant to false detection of the paper tube Ps because the sensor signal is averaged even when a foreign object or scratch is detected on the surface of the roll paper Pr. For example, when a foreign object or scratch is detected on the surface of the roll paper Pr, there is a risk that there will be no difference from the sensor signal that detected the surface of the paper tube Ps or that the sensor signal will be reversed if only the magnitude of the sensor signal is compared. However, according to this embodiment, the sensor signal is averaged even when a foreign object or scratch is detected on the surface of the roll paper Pr, so false detection of the paper tube Ps can be reduced.

[0039] Here, the predetermined time may be equal to or less than the time required for the end of the roll paper Pr to leave the paper core Ps from the position of the sensor 93 in the paper feed direction. This allows a determination to be made before the rear end of the roll paper Pr enters the transport section 160 after the roll end (paper end) of the roll paper Pr is detected.

[0040] The control unit 100 also functions as an example of a setting unit that sets the threshold value. This allows the threshold value to be optimized to suit the roll paper Pr used by the user. Also, the user can optimize the threshold value to suit the roll paper Pr, eliminating the need for service or other support.

[0041] Furthermore, when the control unit 100 detects the paper tube Ps, it may determine that the roll end, which is the rear end of the roll paper Pr, has occurred. This makes it possible to detect the paper tube Ps, and therefore to detect that the roll end has occurred.

[0042] Furthermore, the control unit 100 may stop the feeding operation of the roll paper Pr after determining that the roll end of the roll paper Pr has been reached. This prevents overloading of the roll paper drive unit 130 and the generation of abnormal noise. It also prevents paper jams caused by the stop tape at the rear end of the roll paper Pr getting mixed in with the transport unit 160.

[0043] Furthermore, after determining that the roll end has occurred, the control unit 100 may display on the display unit 170 that the roll paper Pr has run out. This makes it possible to inform the user that the roll paper Pr has run out.

[0044] The control unit 100 may also determine that the roll end has occurred when it detects the rear end of the roll paper Pr by rotating the roll paper Pr in the paper feed direction and detecting the slope of the change in the sensor signal when the roll end (rear end) of the roll paper Pr passes the sensor 93 and the slope of the change in the sensor signal when the rear end of the roll paper Pr passes the rollers 92, or when it detects the paper core Ps by rotating the roll paper Pr in the paper feed direction and comparing the slope of the change in the sensor signal with a threshold value. This increases the number of ways to determine the roll end, making it possible to more reliably detect that the roll end has occurred using a determination method suited to the roll paper Pr.

[0045] The control unit 100 may also determine that the roll end has occurred when it detects the rear end of the roll paper Pr by rotating the roll paper Pr in the paper feed direction and detecting the slope of the change in the sensor signal when the rear end of the roll paper Pr passes the sensor 93 and the slope of the change in the sensor signal when the rear end of the roll paper Pr passes the rollers 92, or when it detects the paper core Ps by rotating the roll paper Pr in the paper feed direction and comparing the slope of the change in the sensor signal with a threshold value. This allows the roll end to be determined precisely, making it possible to more reliably detect that the roll has ended.

[0046] Furthermore, the control unit 100 may determine that the paper tube Ps has been set if the slope of the change in the sensor signal after the start of the leading edge detection operation exceeds a threshold value during the leading edge detection operation after the roll paper Pr has been set. This makes it possible to detect that the paper tube Ps has been set with a slight operation before an error is detected after the leading edge detection operation.

[0047] Furthermore, the control unit 100 may stop the leading edge detection operation when it determines that the paper tube Ps has been set, and notify the user that the paper tube Ps has been set. This makes it possible to detect that the paper tube Ps has been set with a slight operation before an error is detected after the leading edge detection operation, stop the leading edge detection operation, and notify the user, thereby reducing downtime.

[0048] Alternatively, the control unit 100 may detect the leading edge of the rolled paper Pr by rotating the rolled paper Pr in the direction opposite to the paper feed direction and detecting the slope of the change in the sensor signal when the leading edge of the rolled paper Pr passes roller 92 and the slope of the change in the sensor signal when the leading edge of the rolled paper Pr passes sensor 93. This makes it possible to directly detect the leading edge of the rolled paper Pr by using a configuration that detects the roll end without adding any additional parts, and to reliably detect the leading edge of the rolled paper Pr without erroneous detection.

[0049] Next, an example of the operation of setting the roll paper Pr will be described. FIG. 5 is a flow chart illustrating an example of the operation of setting the roll paper in the paper feeder of this embodiment. When the control unit 100 detects that the roll paper Pr has been set in the paper feeder 90 (step S11), for example, when this is detected by the detection result of the sensor 93, it controls the motor drive circuit unit 120 and controls the roll paper drive unit 130 to reverse the roll paper Pr. The roll paper rotation motor (roll paper drive unit 130) rotates the roll paper Pr in the winding direction by a reverse operation (step S12), and the sensor 93 performs a leading edge detection operation to detect the leading edge of the roll paper Pr (step S13). When the leading edge is detected by the sensor 93, the motor drive circuit unit 120 stops the roll paper rotation motor at the paper leading edge stop position under the control of the control unit 100 (step S14), and feeds the leading edge of the roll paper Pr in the conveying direction by a forward rotation operation (step S15). The sensor 93 also starts detecting the rear end (roll end) of the roll paper Pr (step S16). The motor drive circuit unit 140 rotates the transport unit 160 to transport the leading edge of the paper into the device (step S17).

[0050] Next, a configuration example of an arm as a support member and an example of a leading edge detection operation will be described. Fig. 6 is a diagram for explaining a configuration example of an arm in this embodiment, in which (A) is a perspective view explaining an example of an arm 91, (B) is a schematic diagram showing the appearance of a sensor 93, and (C) is a side view explaining an example of an actuator and a side plate that constitute the sensor 93. The arm 91 is positioned so that the roller 92 is on the upstream side in the paper transport direction and the sensor 93 is on the downstream side during the operation (reverse rotation) in which the sensor 93 detects the leading edge of the roll paper.

[0051] The sensor 93 uses, for example, an encoder sensor with a slit 932 provided in an actuator 931, and has a resolution of about 5 μm / pulse, making it possible to detect a step equivalent to the paper thickness. The actuator 931 is disposed between two side plates 933 that form the sensor housing, and a shaft 934 is fitted into a bearing of the side plate 933, so that the actuator 931 rotates around the shaft 934. The actuator 931 has an asymmetric shape with the shaft 934 at the center, for example, as shown in Fig. 6(C). The sensor 93 has a light-emitting unit and a light-receiving unit, and detects the leading edge of the roll paper Pr by counting the number of times that 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).

[0052] In the configuration example of Fig. 6, two rollers 92 are provided, and a sensor 93 is disposed between the two rollers 92. By disposing the sensor 93 between the rollers 92, it is possible to reliably press the floating leading edge of the roll paper, and the output of the sensor 93 does not become unstable depending on the thickness, stiffness, or curl of the paper, so the leading edge can be reliably detected. In addition, because the rollers 92 and the sensor 93 are disposed offset in the circumferential direction, even if there is a partial scratch, the proportion of both the roller and the sensor being affected is reduced, making it less likely to cause erroneous detection. In the following explanation, two or more rollers 92 are also referred to as a roller portion.

[0053] 7 is a diagram illustrating an example of the operation of detecting the leading edge of roll paper in the paper feeder according to the present embodiment. Fig. 7 shows the progress of the leading edge of roll paper Pr passing between roller 92 and sensor 93, with (A) showing the state before the leading edge passes roller 92, (B) showing the state after the leading edge has passed roller 92 and before passing sensor 93, and (C) showing the state after the leading edge has passed sensor 93.

[0054] The sensor 93 and roller 92 are positioned adjacent to each other but offset (offset in the circumferential direction of the roll paper Pr), and because the roller 92 is located upstream of the sensor 93, the roller 92 can hold down the leading edge of the paper until just before the sensor 93 detects the leading edge (FIG. 7(A)). In this manner, the sensor 93 can detect the step (paper thickness) on the surface of the roll paper Pr as the leading edge while the leading edge is in close contact with the surface of the roll paper Pr. This ensures that 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 leading edge of the roll paper Pr.

[0055] In this embodiment, the rollers 92 are positioned upstream of the sensor 93, but detection is also possible in the opposite position. However, positioning the rollers 92 upstream of the sensor 93 is preferable because it makes it possible to more reliably prevent the leading edge of the roll paper Pr from floating until just before detection. Also, by providing two rollers 92 and positioning the sensor 93 between the rollers as shown in Figure 6, it is possible to more reliably prevent the leading edge of the roll paper from floating than with a single roller 92.

[0056] 8 and 9A are diagrams for explaining an example of the relationship between the rollers, the sensor, the leading edge position of the roll paper, and the change in the sensor signal in the paper feeder according to this embodiment. The control unit 100 detects the leading edge of the roll paper Pr by rotating the roll paper Pr in the reverse direction (CW) and detecting the sensor signal when the leading edge of the roll paper Pr passes the roller 92 (see symbol A in FIG. 8) and then the sensor signal when the leading edge of the roll paper Pr passes the sensor 93 (see symbol B in FIG. 8). When detecting the leading edge of the roll paper Pr, the control unit 100 rotates the roll paper Pr in the reverse direction (CW) and detects the slope of the signal change per unit time when the leading edge of the roll paper Pr passes the roller 92 and then the slope of the signal change per unit time when the leading edge of the roll paper Pr passes the sensor 93, thereby detecting the leading edge of the roll paper Pr.

[0057] Furthermore, because the rollers 92 and the sensor 93 are offset in both the circumferential and cylindrical directions, even if there is a partial scratch, the proportion of the scratch that is applied to both the rollers 92 and the sensor 93 is small. Therefore, the sensor signal of the sensor 93 does not have a signal waveform with rising and falling edges as shown in Fig. 9A, making it difficult to erroneously detect the leading edge of the roll paper Pr.

[0058] The control unit 100 controls the motor drive circuit unit 120 to continue reverse rotation after detecting the leading edge of the roll paper Pr, stopping the leading edge of the roll paper Pr at the paper leading edge stop position shown in Fig. 3, and transitioning to forward rotation (CCW). This reduces variation in the paper leading edge insertion posture at the guide entrance, and makes it possible to transport the roll paper Pr downstream stably regardless of the paper condition (e.g. curl, paper type, paper thickness) of the roll paper Pr.

[0059] With the configuration of this embodiment, the step at the leading edge of roll paper Pr, which is equivalent to the paper thickness, can be directly detected, so the output of sensor 93 does not become unstable depending on the thickness, stiffness, or curl of roll paper Pr, and detection accuracy for the leading edge of roll paper Pr can be ensured. Also, by simply placing roll paper Pr in paper feeder 90, the setting operation for roll paper Pr can be completed automatically, eliminating the need for manual labor and preventing skew and jams due to poor guiding of roll paper Pr.

[0060] 9B is a diagram for explaining an example of the configuration of automatic roll paper feeding in the paper feeder according to this embodiment. As described above, the sensor 93 held by the arm (guide plate) 91 uses an encoder sensor with a slit 932 provided in an actuator 931, and with a resolution of about 5 μm / pulse, it is possible to detect a step equivalent to the paper thickness (thickness of the roll paper Pr). The roll paper Pr is (1) rotated in the reverse direction (CW) in the direction in which the roll paper Pr is wound up, and a leading edge detection operation is performed. After the leading edge of the roll paper Pr is detected, the leading edge of the roll paper Pr is sent in the transport direction by a forward rotation operation (CCW), and the roll paper Pr is transported by the transport unit 160 into the machine (image forming device 80) and automatically fed.

[0061] 10 is a diagram showing an example of the state at the end of the roll when the rear end of the roll paper is glued in the paper feeder according to this embodiment. When the roll paper Pr reaches the end of the roll, the roll paper Pr is pulled and driven to be transported until it is determined that a paper jam has occurred, which places a large load on the drive unit (transport drive unit 150) and may cause abnormal noise in some cases. Also, at this time, the image forming device 80 only displays a paper jam error, and the user cannot immediately recognize that the roll paper Pr has run out.

[0062] Fig. 11 is a diagram showing an example of the state of paper passing when the rear end of the roll paper is secured with tape in the paper feeder according to the present embodiment. When the roll paper Pr reaches its end, unlike Fig. 10, the rear end of the roll paper Pr leaves the paper tube Ps and continues to be transported. Because the rear end of the roll paper Pr leaves the paper tube Ps, no paper jam is displayed at this point, but if tape or the like remains on the rear end of the roll paper Pr, it will stick inside the image forming device 80 and cause a paper jam.

[0063] Fig. 12 is a diagram for explaining an example of the roll paper feeding operation in the paper feeder according to this embodiment. In this embodiment, to solve these problems, as shown in Fig. 12, after detecting the leading edge of the roll paper Pr, the sensor 93 detects the unevenness of the surface of the roll paper Pr even during forward rotation (CCW), and the paper thickness detection sensor (sensor 93) reads the step of the roll paper Pr that occurs when the roll end of the roll paper Pr is detected, thereby detecting that the roll paper Pr has run out.

[0064] Figures 13 and 14 are diagrams showing an example of the relationship between the rollers, the sensor, and the rear end position of the rolled paper in the paper feeder according to this embodiment and the change in the sensor signal. Specifically, Figure 13 shows the operation (A) when the rear end of the rolled paper Pr passes the sensor 93, and the operation (B) when the rear end of the rolled paper Pr next passes the roller 92. Figure 15 is a flow chart showing an example of the flow of the roll end detection operation in the paper feeder according to this embodiment.

[0065] After the leading edge of roll paper Pr is detected, the unevenness of the surface of roll paper Pr is detected by sensor 93 while roll paper Pr is rotating forward (CCW) in the paper transport direction. When the rear end of roll paper Pr passes sensor 93 (see FIG. 13(A)), actuator 931 of sensor 93 rises upward, and then when the rear end of roll paper Pr passes roller 92 (see FIG. 13(B)), the guide plate (arm 91) rises upward, actuator 931 of sensor 93 falls downward, and the displacement of the sensor signal changes as shown in FIG. 14 (i.e., the change is in the opposite phase to the displacement of the sensor signal when the leading edge of roll paper Pr is detected as shown in FIG. 9).

[0066] While the roll paper Pr is rotating in the forward direction (CCW) in the paper transport direction, the control unit 231 detects a sensor signal (R1) when the rear end of the roll paper Pr passes through the sensor 93 (see FIG. 13A) (step S1501: Yes), and then detects a sensor signal (R2) when the rear end of the roll paper Pr passes through the roller 92 (see FIG. 13B) (step S1502: Yes), thereby detecting the rear end (roll end) of the roll paper Pr (step S1503). After detecting the roll end of the roll paper Pr, the control unit 231 immediately stops transport of the roll paper Pr (step S1504) and displays on the display unit 170 (e.g., the operation panel) that there is no more roll paper Pr (step S1505).

[0067] In the automatic roll paper feeding configuration of the paper feeder 90 according to this embodiment, the mechanism for detecting the leading edge of the roll paper Pr for automatic roll feeding is used in conjunction with roll end detection, eliminating the need for additional components to detect the roll end. Also, just like the operation for detecting the leading edge of the roll paper Pr, the step at the rear end of the roll paper Pr, which is equivalent to the paper thickness, can be detected, so the roll end can be detected directly.

[0068] 16 and 17 are diagrams showing an example of the detailed relationship between the rollers, the sensor, the rear end position of the roll paper, and the change in the sensor signal in the paper feeder according to this embodiment. In this embodiment, the control unit 100 obtains the amount of change in the sensor signal from the sensor 93 per unit time (i.e., the slope of the change in the sensor signal. Hereinafter, this will be referred to as the slope of the signal change), and detects the ends (leading and trailing ends) of the roll paper Pr based on the amount of change.

[0069] When detecting the rear end of roll paper Pr, the sensor signal has the opposite phase to when detecting the leading edge of roll paper Pr. When the rear end of roll paper Pr passes sensor 93 while roll paper Pr is rotating in the paper transport direction (CCW) (see FIG. 13A), the actuator 931 of sensor 93 rises upward, and when the rear end of roll paper Pr subsequently passes roller 92 (see FIG. 13B), the guide plate (arm 91) rises upward and the actuator 931 of sensor 93 falls downward. Therefore, as shown in FIG. 17, the sensor signal changes in the opposite phase to the displacement of the sensor signal when the leading edge of roll paper Pr is detected, and the slope of the signal change per unit time has the opposite sign.

[0070] 18 to 21 are diagrams showing an example of roll paper fed by a paper feeder according to this embodiment. As shown in Fig. 18, the surface of roll paper Pr is smoother than the surface of the paper tube Ps of roll paper Pr, and the slope of the signal change on the surface of roll paper Pr is small, so the rear end of roll paper Pr can be detected. However, depending on the type of roll paper Pr, the condition of the paper tube surface varies, and there are cases where the rear end of roll paper Pr cannot be detected.

[0071] For example, the paper tube Ps shown in FIG. 19 has a black sheet attached to the surface of a rough paper tube, but is rougher than the surface of the roll paper Pr. Also, for example, the paper tube Ps shown in FIG. 20 has a white sheet attached to a rough paper tube, but the attached joints overlap, creating a step. The surface of the paper tube Ps shown in FIG. 20 is also rougher than the surface of the roll paper Pr. Furthermore, the paper tube Ps shown in FIG. 21 remains a rough paper tube, but has grooves on the surface. Also, the paper tube Ps shown in FIG. 21 is rougher than the surface of the roll paper Pr, and contains fibrous matter.

[0072] If the surface of the paper tube Ps is rough, and there is a convex or concave portion immediately after the roll end of the roll paper Pr, the slope of the signal change becomes small and it may not be possible to detect the roll end. Also, when the actuator 931 of the sensor 93 passes over the step between the roll end of the roll paper Pr and the surface of the paper tube, the movement of the actuator 931 becomes smooth, making it impossible to obtain a large slope of the signal change, and the slope of the signal change becomes small.

[0073] Therefore, in this embodiment, when detecting the rear end of the roll paper Pr, the control unit 100 detects the end (rear end) of the roll paper Pr by comparing the slope of the signal change when the actuator 931 of the sensor 93 moves over the end of the roll paper Pr (i.e., the ratio between the amount of movement of the roll paper Pr and the amount of change in the sensor signal) with a threshold value.

[0074] 22 and 23A to 23C are diagrams for explaining an example of the detection operation of the end of the roll paper in the paper feeder according to this embodiment. As shown in Fig. 22, even if the surface of the paper tube of the roll paper Pr is smooth, there is a section at the rear end of the roll paper Pr that floats by the thickness of the paper. Because the roll paper Pr is tightly wound around the paper tube Ps, the roll paper Pr and the paper tube Ps are in close contact even on the surface of the paper tube Ps that is rough.

[0075] 23A to 23C are schematic diagrams showing the slope of the signal change when the rear end of roll paper Pr passes actuator 931 of sensor 93, with the dotted lines in the diagrams indicating the slope of the signal change. As actuator 931 passes partway through the end of roll paper Pr from a state in which actuator 931 is on the surface of roll paper Pr (see FIG. 23A), the slope of the signal change gradually increases (see FIG. 23B), and when actuator 931 passes from the end of roll paper Pr to paper core Ps, the slope of the signal change becomes equal to or exceeds a threshold value (see FIG. 22C). This allows control unit 100 to detect the end of roll paper Pr based on whether the slope of the signal change becomes equal to or exceeds a threshold value.

[0076] 24, 25A to 25C are diagrams for explaining an example of the detection operation of the end of the roll paper in the paper feeder according to this embodiment. As shown in FIG. 24, the surface of the paper tube Ps of the roll paper Pr may be rough. In this case, the roll paper Pr is in close contact with the paper tube Ps at the part where the roll paper Pr starts to be wound around the paper tube Ps, but before the second turn, there are parts where the roll paper Pr cannot be in close contact with the paper tube Ps due to the thickness of the roll paper Pr. As a result, there are rough parts of the paper tube Ps, and the slope of the signal change does not exceed the threshold value, so the rear end of the roll paper Pr may not be detected.

[0077] 25A to 25C are schematic diagrams showing the actuator 931 passing the rear end of roll paper Pr when the surface of the paper core of roll paper Pr is rough, and the dotted line in the figure shows the slope of the signal change. As the actuator 931 passes partway through the end of the roll paper Pr from the state where the actuator 931 is on the surface of the roll paper Pr (see FIG. 25A), the slope of the signal change gradually becomes larger (see FIG. 25B). However, even if the actuator 931 reaches the paper core Ps from the end of the roll paper Pr, if the surface of the paper core Ps is rough, the slope of the signal change is smaller than the threshold value (see FIG. 25C). In this case, the control unit 100 cannot detect the end of the roll paper Pr depending on whether the slope of the signal change is equal to or greater than the threshold value.

[0078] 26, 27A to 27C are diagrams for explaining an example of the detection operation of the end of the roll paper in the paper feeder according to this embodiment. As shown in Fig. 25, if the surface of the paper tube of the roll paper Pr is rough and fibrous objects protrude, the part where the roll paper Pr starts to wind around the paper tube is in close contact with the paper tube Ps, but before the second turn, due to the thickness of the roll paper Pr, there will be a part where it cannot be in close contact with the paper tube Ps. In this case as well, fibrous objects of the paper tube Ps will come out, the slope of the signal change will not exceed the threshold value, and the rear end of the roll paper Pr may not be detected.

[0079] 27A to 27C are schematic diagrams of the actuator 931 passing the rear end of roll paper Pr when the surface of the paper core of roll paper Pr is rough and fibrous, and the dotted line in the figure indicates the slope of the signal change. As the actuator 931 passes partway through the end of the roll paper Pr from the state where the actuator 931 is on the surface of the roll paper Pr (see FIG. 27A), the slope of the signal change gradually becomes larger (see FIG. 27B). However, even if the actuator 931 reaches the paper core Ps from the end of the roll paper Pr, if the surface of the paper core Ps is rough, the slope of the signal change is smaller than the threshold value (see FIG. 27C). In this case, the control unit 100 cannot detect the end of the roll paper Pr depending on whether the slope of the signal change is equal to or greater than the threshold value.

[0080] Figures 28A to 28C are diagrams for explaining an example of the detection operation of the end of roll paper in the paper feeder according to this embodiment. Next, an example is shown in which there is a groove-shaped recess on the surface of the paper tube of roll paper Pr. Figures 28A to 28C are schematic diagrams of actuator 931 passing the rear end of roll paper Pr when there is a groove on the surface of the paper tube of roll paper Pr, and the dotted lines in the figures represent the slope of the signal change.

[0081] As the actuator 931 passes partway through the end of the roll paper Pr from the state where it is on the surface of the roll paper Pr (see FIG. 28A), the slope of the signal change gradually increases (see FIG. 28B), but even if the actuator 931 reaches the paper tube Ps from the end of the roll paper Pr, if there is a groove on the surface of the paper tube Ps, the slope of the signal change is smaller than the threshold value (see FIG. 28C). In this case, the control unit 100 cannot detect the end of the roll paper Pr depending on whether the slope of the signal change is equal to or greater than the threshold value.

[0082] Figures 29A to 29C are diagrams for explaining an example of the detection operation of the end of the roll paper in the paper feeder according to this embodiment. In addition to the influence of the paper tube Ps described above, there are cases where fluff-like protrusions occur due to poor cutting at the rear end of the roll paper Pr. Figures 29A to 29C are schematic diagrams of when the actuator 931 passes the rear end of the roll paper Pr when there is fluff at the rear end of the roll paper Pr due to poor cutting, and the dotted line in the figure represents the slope of the signal change.

[0083] As the actuator 931 passes partway through the end of the roll paper Pr from the state where it is on the surface of the roll paper Pr (see FIG. 29A), the slope of the signal change gradually increases (see FIG. 29B), but even if the actuator 931 reaches the paper tube Ps from the end of the roll paper Pr, if there is a groove on the surface of the paper tube Ps, the slope of the signal change is smaller than the threshold value (see FIG. 29C). In this case, the control unit 100 cannot detect the end of the roll paper Pr depending on whether the slope of the signal change is equal to or greater than the threshold value.

[0084] 30, 31A to 31D are diagrams for explaining an example of the detection operation of the end of the roll paper in the paper feeder according to the present embodiment. As shown in FIG. 30, in the case of a wide roll paper Pr in which only the center part is taped to the paper core Ps, the roll paper Pr may be in a state of floating from the paper core Ps. If the sensor 93 for detecting the rear end of the roll paper Pr is provided at the end of the roll paper Pr, the roll paper Pr will be detected in a state of floating from the paper core Ps, and the slope of the signal change may become small and may not exceed the threshold value. When the rear end of the roll paper Pr floats, the actuator 931 of the sensor 93 changes suddenly, so the rear end of the roll paper Pr can be detected, but if the roll paper Pr comes into contact with the actuator 931 with R, there is a possibility that a large slope of the signal change will not be obtained when the roll paper Pr passes the actuator 931.

[0085] Here, sensor 93 is often provided at an end that is not affected by width, so that roll paper Pr of multiple widths can be detected by a single sensor 93. Although rollers 92 hold down roll paper Pr, in the case of stiff roll paper Pr, if the portion not secured by tape bends and the roll paper Pr becomes slanted (i.e., has an R with respect to the paper core) when actuator 931 passes the end of the roll paper Pr, the rear end of the roll paper Pr approaches the surface of the paper core, so the step becomes smaller and no large gradient in the signal change can be obtained.

[0086] Fig. 32 is a schematic diagram showing an example of a change in a sensor signal on the surface of a roll of paper in a paper feeder according to this embodiment. Fig. 33 is a schematic diagram showing an example of a change in a sensor signal on the end of a roll of paper in a paper feeder according to this embodiment. In this embodiment, the control unit 100 detects the rear end of the roll of paper Pr by detecting the difference in roughness between the surface of the roll of paper Pr and the surface of the paper tube Ps, and determines that the roll is at its end.

[0087] Specifically, the control unit 100 monitors the sensor signal on the surface of the roll paper Pr while the roll paper Pr is being fed or transported during printing. As described above, if the surface of the roll paper Pr is smooth, the slope of the signal change of the sensor 93 (slope of the paper surface signal fluctuation) Sp is small, as shown in FIG. 32. The control unit 100 determines whether the slope Sp1 of the signal change of the sensor signal per unit time exceeds the threshold value Ss. In contrast, the surface of the paper tube of the roll paper Pr is rough, so the slope St of the signal change of the sensor 93 (slope of the paper tube surface signal fluctuation) fluctuates greatly, as shown in FIG. 33. If the surface of the paper tube of the roll paper Pr is rough, there are cases where the slope St1 of the signal change of the sensor signal per unit time exceeds the threshold value Ss.

[0088] 34 is a schematic diagram showing an example of fluctuation in the slope of the signal change in the paper feeder according to this embodiment. In this embodiment, the control unit 100 detects the change (step) between the roll paper Pr and the paper tube Ps by comparing the magnitude of the slope of the signal change with a threshold value. Here, Ss is an example of a threshold value for determining between the roll paper Pr and the paper tube Ps. This threshold value Ss is set to be equal to or greater than the slope of the signal change on the surface of the roll paper Pr, and if the control unit 100 detects a change greater than this, it determines that the roll end of the roll paper Pr has been reached (determines that the portion of the paper tube Ps has been detected).

[0089] 35 and 36 are diagrams for explaining an example of a method for comparing the magnitude of the gradient of the signal change in the paper feeder according to the present embodiment. Specifically, FIG. 35 and FIG. 36 are diagrams for explaining an example of a method for comparing the magnitude of the change amount of the sensor signal per certain time T1. In this embodiment, the control unit 100 detects the paper tube Ps by comparing the integrated value Hp of the absolute value of the gradient of the signal change on the surface of the roll paper Pr with the integrated value Ht of the absolute value of the gradient of the signal change on the surface of the paper tube Ps. In addition, the control unit 100 sets a threshold value Hs that is greater than the integrated value Hp of the absolute value of the gradient of the signal change on the surface of the roll paper Pr, and when the integrated value H of the absolute value of the gradient of the signal change on the surface during the transport of the roll paper Pr exceeds the threshold value Hs, it is determined that the paper tube Ps is present. As a result, even if a foreign object or scratch is detected on the surface of the roll paper Pr, the gradient of the signal change is averaged, making it more resistant to false detection of the paper tube Ps. When a foreign object or scratch is detected on the roll paper Pr, if the magnitude of the sensor signal alone, as shown in Figure 34, is compared with the threshold value, there is a risk that there will be no difference or that the magnitude will be reversed from the sensor signal detecting the surface of the paper tube Ps.

[0090] 37 is a diagram showing an example of the slope of the paper surface signal fluctuation when there is a foreign object on part of the surface of the roll paper in the paper feeder according to this embodiment. When there is a foreign object on part of the surface of the roll paper Pr, the overall sensor signal fluctuates little, but the sensor signal fluctuates greatly only when a foreign object is detected on the surface of the roll paper Pr. Therefore, when detecting the paper tube of the roll paper Pr based only on the slope of the signal change, there is a risk of falsely detecting the paper tube Ps, but when looking at the integrated value of the absolute value of the slope of the signal change within a certain period of time, the slope of the signal change is averaged, eliminating the risk of false detection of the paper tube Ps and making it possible to detect the paper tube Ps more accurately.

[0091] Furthermore, by making the threshold value Ss shown in Fig. 34 and the threshold value Hs shown in Fig. 36 variable, it is possible to optimize the threshold value to suit the roll paper Pr used by the user. If the roll paper Pr used is special, for example, if the surface roughness of the roll paper Pr is different from normal, or if the surface condition of the paper tube Ps is different from normal, the threshold values ​​Ss and Hs can be set to suit the condition of the roll paper Pr.

[0092] In addition, by allowing the user to set the threshold value Ss and the threshold value Hs, the user can set the threshold value by himself / herself, eliminating the need for a service or other support, and can set the threshold value whenever necessary. For example, this can be easily done by setting several threshold values ​​in advance and allowing the user to select and set the value from an operation unit.

[0093] 38 is a flowchart showing an example of the flow of the detection operation for the roll end of roll paper in the paper feeder according to this embodiment. In this embodiment, while roll paper Pr is rotating in the forward direction (CCW) (step S3801), the control unit 100 determines whether or not the integrated value H of the absolute value of the slope of the change in the sensor signal on the surface of the roll paper Pr during transport exceeds a threshold value Hs (step S3802), and if the integrated value H exceeds the threshold value Hs (step S3802: Yes), it detects the paper core Ps (step S3803).

[0094] When the control unit 100 detects the paper tube Ps, it determines that the rear end (roll end) of the roll paper Pr has passed the sensor 93 (step S3804). The control unit 100 then stops the transport operation of the roll paper Pr (step S3805). From the time the sensor 93 detects the roll end until transport of the roll paper Pr is stopped, transport of the roll paper Pr needs to be stopped in the "range from the position of the sensor 93 to the sticking of the roll end to the paper tube Ps" shown in FIG. 10. If this range is exceeded, the transport drive system will be overloaded or abnormal noise will occur due to tension between the roll paper Pr and the paper tube, and if the rear end of the roll paper Pr is secured with tape, there is a risk of paper jams due to the tape getting mixed into the transport unit 160.

[0095] 35 is set to be equal to or less than the time required for transporting roll paper Pr from the position of sensor 93 to the time when the roll end separates from paper core Ps. This makes it possible to detect the roll end before the rear end of roll paper Pr enters transport section 160 after the roll end is detected. Also, by issuing a warning such as a display or sound on the operation section or the like that roll paper Pr has run out after transport of roll paper Pr has stopped (step S3806), it is possible to notify the user that roll paper Pr has run out, which leads to a reduction in downtime of paper feeder 90.

[0096] Furthermore, in this embodiment, the control unit 100 is provided with both functions: a method for directly detecting a step at the rear end of the roll paper Pr equivalent to the paper thickness, and a method for detecting the paper core Ps and judging the roll end, making it possible to select a roll end detection method suited to the roll paper Pr. By increasing the number of roll end detection methods, the roll end can be detected more reliably using a roll end detection method suited to the roll paper Pr.

[0097] Also, in this embodiment, the control unit 100 may be provided with both functions of a method of directly detecting a step equivalent to the paper thickness at the rear end of the roll paper Pr and a method of detecting the roll end by detecting the paper tube Ps, and may detect the roll end based on the results of both roll end detection methods. In other words, the control unit 100 may determine that the roll end has occurred when it detects the roll end at the paper tube Ps after detecting the roll end at the step equivalent to the paper thickness. In this way, by detecting the roll end precisely, it is possible to more reliably detect that the roll end has occurred.

[0098] Also, if the paper tube Ps is set by mistake when setting the roll paper Pr, the operation to detect the leading edge of the roll paper Pr begins, a detection error occurs at the leading edge of the roll paper Pr, and then the error is displayed after the transport of the roll paper Pr stops. In this case, the time until the error is displayed becomes downtime, which is wasted time for the user. Therefore, in this embodiment, the control unit 100 compares the slope of the signal change after the start of the operation to detect the leading edge of the roll paper Pr set with a pre-registered threshold value, and determines that the paper tube Ps has been set if the slope of the signal change exceeds the threshold value. Then, after it is determined that the paper tube Ps has been set, the leading edge detection operation is stopped and the user is notified, thereby significantly reducing downtime.

[0099] 39 is a flow chart showing an example of the flow of the paper core detection operation in the paper feeder according to the present embodiment. After the roll paper Pr is set (step S3901), the control unit 100 starts the leading edge detection operation (step S3902). After the leading edge detection operation starts, the control unit 100 compares, for example, the sensor signal S of a quarter rotation of the roll paper Pr with the threshold value Ss (step S3903).

[0100] If the sensor signal S does not exceed the threshold value Ss during that time (step S3903: No), the control unit 100 determines that roll paper Pr has been set and proceeds with normal leading edge detection operation (step S3904). After that, when the control unit 100 detects the leading edge of roll paper Pr, it stops the leading edge of roll paper Pr at the stop position (step S3905), then performs a forward rotation operation to transport the leading edge of roll paper Pr to the paper feed unit (step S3906), and then performs the printing operation (step S3907).

[0101] On the other hand, if the sensor signal S exceeds the threshold value Ss (step S3903: Yes), the control unit 100 detects the paper tube Ps (step S3908), determines that the paper tube Ps has been set (step S3909), and stops the transport operation of the roll paper Pr (step S3910). The control unit 100 then displays that fact on the display unit 170 to inform the user (step S3911). The control unit 100 can also inform the user that the transport operation of the roll paper Pr has stopped by an operation other than display, for example, a sound, etc. In the present embodiment, the control unit 100 uses the sensor signal S and the threshold value Ss to determine whether the paper tube Ps has been set or not, but it may also determine whether the paper tube Ps has been set or not by using the integral values ​​(accumulated values) Hp, Ht shown in FIG. 36 and the threshold value Hs.

[0102] Furthermore, the control unit 100 can detect the leading edge of the rolled paper Pr by rotating the rolled paper Pr in the direction opposite to the feeding direction and detecting the slope of the signal change of the sensor signal of the sensor 93 when the leading edge of the rolled paper Pr passes the rollers 92 and the slope of the signal change when the leading edge of the rolled paper Pr passes the sensor 93. In the automatic roll paper feeding configuration of the paper feeder 90 according to this embodiment, the mechanism for detecting the leading edge of the rolled paper Pr for automatic roll feeding is used in combination with detection of the paper core Ps, thereby achieving the function without adding any parts for performing the roll end.

[0103] Furthermore, by providing a paper feed mechanism having the functions of this embodiment, it is possible to detect the leading edge of the roll paper Pr and the roll end without adding any parts.

[0104] In this way, according to the paper feeder 90 of this embodiment, the difference between the surface of the roll paper Pr and the surface of the paper tube Ps can be detected, so that the accuracy of detecting the roll end can be improved.

[0105] The program executed by sheet feeding device 90 of the present embodiment is provided by being pre-installed in a ROM (Read Only Memory) or the like. The program executed by sheet feeding device 90 of the present embodiment may be provided by being recorded in an installable or executable file format on a computer-readable recording medium such as a CD-ROM, a flexible disk (FD), a CD-R, or a DVD (Digital Versatile Disk).

[0106] Furthermore, the program executed by sheet feeding device 90 of the present embodiment may be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Also, the program executed by sheet feeding device 90 of the present embodiment may be provided or distributed via a network such as the Internet.

[0107] The program executed by the paper feeding device 90 of this embodiment has a modular structure including each of the above-mentioned parts (control unit 100), and in terms of actual hardware, a processor such as a CPU (Central Processing Unit) reads the program from the ROM and executes it, thereby loading each of the above-mentioned parts into a main memory device and generating the control unit 100 on the main memory device.

[0108] In the above embodiment, the image forming apparatus of the present invention is described as being applied to a multifunction peripheral having at least two of the functions of a copy function, a printer function, a scanner function, and a facsimile function. However, the image forming apparatus can be applied to any image forming apparatus such as a copier, a printer, a scanner device, or a facsimile device.

[0109] For example, aspects of the present invention are as follows.

[0110] <1> A paper feeder that rotates a roll of paper forward and backward and feeds the roll of paper, Coro and a sensor for detecting a step at an end of the roll paper; a support member that disposes the sensor and the roller at positions offset from each other in the circumferential direction of the roll paper toward approximately the center of the roll paper and supports the sensor and the roller so that they abut against the surface of the roll paper; a control unit that controls the rotation of the roll paper based on a sensor signal output from the sensor, The control unit rotates the roll paper in a paper feed direction and detects the paper core of the roll paper by comparing a slope of the change in the sensor signal with a threshold value. <2> The control unit detects the paper tube by comparing an integrated value of an absolute value of a gradient of a change in the sensor signal per predetermined time with the threshold value. <1> The paper feeding device described in <3> the predetermined time is equal to or less than the time required for the end of the roll paper to separate from the paper core from the position of the sensor in the paper feed direction. <2> The paper feeding device described in <4> A setting unit for setting the threshold value is further provided. <1> from <3> 13. A paper feeding device according to any one of claims 1 to 12. <5> When the control unit detects the paper core, the control unit determines that the roll end, which is the rear end of the roll paper, has occurred. <1> from <4> 13. A paper feeding device according to any one of claims 1 to 12. <6> The control unit stops the feeding operation of the roll paper after determining that the roll end has occurred. <5> The paper feeding device described in <7> A display unit that displays the feeding state of the roll paper is further provided, After determining that the roll end has occurred, the front control unit causes the display unit to display that the roll paper has run out. <5> or <6> The paper feeding device described in <8> the control unit determines that the roll end has occurred when it detects the rear end of the roll paper by rotating the roll paper in the paper feed direction and detecting the slope of the change in the sensor signal when the rear end of the roll paper passes the sensor and the slope of the change in the sensor signal when the rear end of the roll paper passes the roller, or when it detects the paper core by rotating the roll paper in the paper feed direction and comparing the slope of the change in the sensor signal with the threshold value. <5> The paper feeding device described in <9> the control unit determines that the roll end has occurred when it detects the rear end of the roll paper by rotating the roll paper in the paper feed direction and detecting the slope of the change in the sensor signal when the rear end of the roll paper passes the sensor and the slope of the change in the sensor signal when the rear end of the roll paper passes the roller, and when it detects the paper core by rotating the roll paper in the paper feed direction and comparing the slope of the change in the sensor signal with the threshold value. <5> The paper feeding device described in <10> the control unit determines that the paper core has been set when, in a leading edge detection operation for the roll paper after the roll paper has been set, a slope of the change in the sensor signal after the leading edge detection operation has started exceeds the threshold value. <1> from <9> 13. A paper feeding device according to any one of claims 1 to 12. <11> When the control unit determines that the paper tube has been set, the control unit stops the leading end detection operation and notifies the user that the paper tube has been set. <10> The paper feeding device described in <12> the control unit detects the leading edge of the roll paper by rotating the roll paper in a direction opposite to a paper feed direction and detecting a slope of the change in the sensor signal when the leading edge of the roll paper passes the roller and a slope of the change in the sensor signal when the leading edge of the roll paper passes the sensor. <1> from <11> 13. A paper feeding device according to any one of claims 1 to 12. <13> A paper feeding method executed by a paper feeding device including a transport unit that rotates roll paper forward and backward and feeds the roll paper, a roller, a sensor that detects a step at an end of the roll paper, and a support member that positions the sensor and the roller in positions offset from each other in a circumferential direction of the roll paper toward approximately the center of the roll paper and supports the sensor and the roller so that they abut against a surface of the roll paper, controlling rotation of the roll paper based on a sensor signal output from the sensor; a step of rotating the roll paper in a paper feed direction and detecting a paper core of the roll paper by comparing a slope of the change in the sensor signal with a threshold value; A paper feeding method including: <14> a computer that controls a paper feeder that includes a transport section that rotates a roll paper forward and backward and feeds the roll paper, a roller, a sensor that detects a step at an end of the roll paper, and a support member that positions the sensor and the roller in positions offset from each other in the circumferential direction of the roll paper toward approximately the center of the roll paper and supports the sensor and the roller so that they abut against the surface of the roll paper, a control unit that controls the rotation of the roll paper based on a sensor signal output from the sensor; The control unit rotates the roll paper in a paper feed direction, and detects the paper core of the roll paper by comparing a slope of the change in the sensor signal with a threshold value. <15> <1> from <12> 2. An image forming apparatus comprising the paper feeder according to claim 1 . [Explanation of symbols]

[0111] 90 Paper feeder 91 Arm 92 Coro 93 Sensors 100 Control section 120 Motor drive circuit section 130 Roll paper drive unit 140 Motor drive circuit section 150 Conveyor drive unit 160 Conveyor 170 Display section Pr Roll Paper Ps paper tube [Prior art documents] [Patent documents]

[0112] [Patent Document 1] Patent No. 4133163

Claims

1. A paper feeding device for rotating a roll paper forward and backward and feeding the roll paper, comprising: a roller; a sensor for detecting a step at an end of the roll paper; a support member that arranges the sensor and the roller at positions offset from each other in the circumferential direction of the roll paper toward the approximate center of the roll paper, and supports the sensor and the roller so as to be in contact with the surface of the roll paper; a control unit that controls the rotation of the roll paper based on a sensor signal output from the sensor; The control unit rotates the roll paper in the paper feeding direction, compares the slope of the change in the sensor signal with a threshold value, and detects the paper tube of the roll paper. A paper feeding device.

2. The control unit compares an integrated value of an absolute value of a slope of a change in the sensor signal per a predetermined time with the threshold value to detect the paper tube. The paper feeding device according to claim 1.

3. The predetermined time is equal to or less than the time required for a range from a position of the sensor in the paper feeding direction until an end of the roll paper is separated from the paper tube. The paper feeding device according to claim 2.

4. The paper feeding device according to any one of claims 1 to 3, further comprising a setting unit that sets the threshold value.

5. When the control unit detects the paper tube, it determines that it is a roll end which is a rear end of the roll paper. The paper feeding device according to claim 1.

6. After determining that it has become the roll end, the control unit stops the paper feeding operation of the roll paper. The paper feeding device according to claim 5.

7. The paper feeding device further includes a display unit that displays a paper feeding state of the roll paper, After determining the roll end, the pre-control unit displays on the display unit that the roll paper has run out. The paper feeding device according to claim 5 or 6.

8. The control unit rotates the roll paper in the paper feeding direction, and when detecting the rear end of the roll paper by detecting the slope of the change in the sensor signal when the rear end of the roll paper passes through the sensor and the slope of the change in the sensor signal when the rear end of the roll paper passes through the roller, or when the roll paper is rotated in the paper feeding direction and the paper tube is detected by comparing the slope of the change in the sensor signal with the threshold value, it determines that it is the roll end. The paper feeding device according to claim 5.

9. When the control unit rotates the roll paper in the paper feeding direction and detects the slope of the change in the sensor signal when the rear end of the roll paper passes through the sensor and the slope of the change in the sensor signal when the rear end of the roll paper passes through the roller, and thereby detects the rear end of the roll paper, and when the control unit rotates the roll paper in the paper feeding direction and compares the slope of the change in the sensor signal with the threshold value to detect the paper tube, it determines that it is a roll end. The paper feeding device according to claim 5.

10. In the leading end detection operation of the roll paper after the roll paper is set, when the slope of the change in the sensor signal after the start of the leading end detection operation exceeds the threshold value, the control unit determines that the paper tube is set. The paper feeding device according to claim 1.

11. When the control unit determines that the paper tube is set, it stops the leading end detection operation and notifies that the paper tube is set. The paper feeding device according to claim 10.

12. The control unit rotates the roll paper in a direction opposite to the paper feeding direction and detects the leading end of the roll paper by detecting the slope of the change in the sensor signal when the leading end of the roll paper passes through the roller and the slope of the change in the sensor signal when the leading end of the roll paper passes through the sensor. The paper feeding device according to claim 1.

13. A paper feeding method executed by a paper feeding device including a conveyance unit that rotates the roll paper forward and backward and feeds the roll paper, a roller, a sensor that detects a step at an end of the roll paper, and a support member that arranges the sensor and the roller at positions offset from each other in the circumferential direction of the roll paper toward the approximate center of the roll paper and supports the sensor and the roller so as to be in contact with the surface of the roll paper, the method comprising: Controlling the rotation of the roll paper based on a sensor signal output from the sensor; Rotating the roll paper in the paper feeding direction and comparing the slope of the change in the sensor signal with a threshold value to detect a paper tube of the roll paper; A paper feeding method including.

14. A computer that controls a paper feeding device comprising: a conveyance unit that rotates a roll paper forward and backward and feeds the roll paper; a roller; a sensor that detects a step at an end of the roll paper; and a support member that arranges the sensor and the roller at positions offset from each other in the circumferential direction of the roll paper toward the approximate center of the roll paper and supports the sensor and the roller so as to be in contact with the surface of the roll paper. Function as a control unit that controls the rotation of the roll paper based on a sensor signal output from the sensor. The control unit rotates the roll paper in the paper feeding direction, compares the slope of the change in the sensor signal with a threshold value, and detects a paper tube of the roll paper. A program.

15. An image forming apparatus comprising the paper feeding device according to claim 1.

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