Paper feeder and image forming apparatus

Abstract

To accurately detect a leading end of a roll-like recording medium while reducing the processing load.SOLUTION: A paper feeder includes: a rotary driving part that rotates a roll-like recording medium; a detection part that detects a height position of an outer peripheral surface of the roll-like recording medium during rotation of the roll-like recording medium; and a controlling part that performs leading end detection processing for detecting a leading end of the roll-like recording medium based on a detection signal of the detection part. The controlling part activates the detection part at a first sampling interval when the leading end detection processing is started, performs low accuracy sampling to detect a detected part where the height position of the outer peripheral surface is displaced, and performs high accuracy sampling where the detection part is activated at a second sampling interval that is shorter than the first sampling interval based on the detected part detected by the low accuracy sampling.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] A paper feeder that feeds a roll-shaped recording medium such as roll paper rotates the set roll paper and continuously pays out the roll paper to the paper feed destination. In this type of paper feeder, a technique is known that automatically detects the leading edge of the roll paper after the roll paper is set and pays out the detected leading edge to the paper feed destination.

[0003] For example, the paper feeding device disclosed in Patent Document 1 detects the displacement of the outer surface of the rotating roll paper using a displacement change detection means (detection unit) that contacts the roll paper, and determines the point where a large displacement occurs to be the leading edge of the roll paper. Summary of the Invention [Problem to be solved by the invention]

[0004] However, in order to accurately detect the leading edge of the roll paper, this type of paper feeder must perform high-precision sampling by operating the detection unit at short sampling intervals while the roll paper is rotating, and the detection results must be continually evaluated by the control unit. In other words, the paper feeder must continuously perform high-precision sampling until the leading edge of the roll paper is detected, imposing a large processing load.

[0005] It is therefore an object of the present invention to provide a paper feeder and an image forming apparatus that accurately detect the leading edge of a roll-shaped recording medium while reducing the processing load. [Means for solving the problem]

[0006] One aspect of the present invention is a paper feeding device including a rotation drive unit that rotates a rolled recording medium, a detection unit that detects the height position of an outer circumferential surface of the rolled recording medium while the rolled recording medium is rotating, and a control unit that performs a leading edge detection process to detect the leading edge of the rolled recording medium based on a detection signal from the detection unit. At the start of the leading edge detection process, the control unit operates the detection unit at a first sampling interval to perform low-precision sampling to detect a detection point where the height position of the outer circumferential surface is displaced, and performs high-precision sampling to operate the detection unit at a second sampling interval that is shorter than the first sampling interval based on the detection point detected by the low-precision sampling. a determination is made as to whether or not a height position of the outer circumferential surface detected by the low-precision sampling is equal to or greater than a determination threshold, a location where the height position of the outer circumferential surface is equal to or greater than the determination threshold is identified as the detected location, a slope at which the detected location descends is calculated based on a plurality of plots obtained by sampling the detected location by the high-precision sampling, the angle of the slope is compared with an angle threshold, and if the angle of the slope is equal to or greater than the angle threshold, the detected location is determined to be the leading end of the rolled recording medium, and if the angle of the slope is less than the angle threshold, the detected location is determined to be not the leading end of the rolled recording medium. . Effect of the Invention

[0007] The above-described paper feeding device and image forming apparatus can accurately detect the leading end of the roll-shaped recording medium while reducing the processing load. [Brief description of the drawings]

[0008] [Figure 1] 1 is a schematic side view of a paper feeder according to a first embodiment. [Diagram 2] 11A to 11C are diagrams illustrating an example of detection of the outer circumferential surface of the roll body by a detection unit. [Diagram 3] 6 is a flowchart showing a first processing example of a control unit. [Figure 4] 13 is a flowchart showing a second processing example of the control unit. [Diagram 5] FIG. 11 is a schematic side view of a paper feeder according to a second embodiment. [Figure 6] 13 is a flowchart showing a third example of processing by the control unit. [Figure 7] FIG. 11 is a schematic side view of a paper feeder according to a third embodiment. [Figure 8] 13 is a flowchart showing a fourth processing example of the control unit. [Figure 9] 13 is a schematic side view showing another form of roll paper in the paper feeder according to the third embodiment. FIG. [Figure 10]13 is a flowchart showing a fifth processing example of the control unit. [Figure 11] 13 is a flowchart of a routine for one item in the fifth processing example. [Figure 12] 13 is a flowchart of a multiple routine in the fifth processing example. [Figure 13] FIG. 13 is a schematic side view of a paper feeder according to a fourth embodiment. [Figure 14] 13 is a flowchart showing a part of a sixth processing example of the control unit. [Figure 15] 13 is a flowchart showing another part of the sixth processing example of the control unit. [Figure 16] FIG. 1 is an explanatory diagram showing an image forming apparatus to which a paper feeder according to first to fourth embodiments is applied. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, a description will be given of an embodiment of the invention with reference to the drawings. The embodiment shown below is an example of a paper feeder for embodying the technical concept of the present invention, and the present invention is not limited to the embodiment shown below. The dimensions, materials, shapes, relative positions, etc. of the components described below are intended to be illustrative, and are not intended to limit the scope of the present invention, unless otherwise specified. Furthermore, the sizes and positional relationships of the components shown in the drawings may be exaggerated in order to clarify the explanation.

[0010] [First embodiment] Fig. 1 is a schematic side view of a paper feeding device 100 according to a first embodiment. As shown in Fig. 1, the paper feeding device 100 feeds a rolled recording medium such as paper (roll paper), cloth, other fibers, a resin sheet, or a resin film wound in a roll shape. In the following, a paper feeding device 100 that feeds roll paper RP as a rolled recording medium will be representatively described. In the following, the part of the roll paper RP that is wound in a roll shape will be referred to as the roll body R1, and the part that is unwound from the roll body R1 by the paper feeding operation will be referred to as the unwound section R2.

[0011] The paper feeder 100 includes a rotation drive unit 1 that rotates the roll body R1, a detection unit 2 that contacts the outer circumferential surface CS of the roll body R1 to detect the height position of the outer circumferential surface CS, a separation claw unit 3 that separates the leading edge of the roll paper RP, and a transport guide unit 4 that guides the payout unit R2. The paper feeder 100 also includes a control unit 5 that controls the operation of the paper feeder 100.

[0012] In this description, the "height position of the outer peripheral surface CS" refers to the height in the radial direction (normal direction, thickness direction of the roll paper RP) of the outer peripheral surface CS of the roll body R1, which has a circular shape in side view. Immediately after the roll paper RP is set in the paper feeder 100, the height position of the outer peripheral surface CS is approximately constant in the circumferential direction of the roll body R1. However, the height position of the outer peripheral surface CS displaces in the radial direction due to a step between the upper and lower layers of paper at the leading edge rt of the roll paper RP, and bending (protrusion) or undulation of the roll paper RP.

[0013] The rotation drive unit 1 includes a motor 10, a drive transmission unit 11 connected to a rotating shaft 10a of the motor 10, and a shaft unit 12 connected to the drive transmission unit 11 and on which the roll paper RP is directly attached (set). The rotation drive unit 1 can selectively rotate the roll body R1 in the direction of arrow A (clockwise direction in FIG. 1) and in the direction of arrow B (counterclockwise direction in FIG. 1).

[0014] The motor 10 is capable of controlling the rotation angle or rotation speed and rotating the rotating shaft 10a in both forward and reverse directions. The rotation drive unit 1 connects the motor 10 and the control unit 5 via a driver, and rotates the rotating shaft 10a of the motor 10 by receiving power from the driver under the control of the control unit 5. The drive transmission unit 11 is made up of gears, pulleys, belts, etc., and transmits the rotational driving force of the rotating shaft 10a of the motor 10 to the shaft unit 12. The shaft unit 12 is located on the central axis of the roll body R1, and the core of the roll body R1 is removably attached to its outer circumferential surface.

[0015] The rotation drive unit 1 may include a rotation detection sensor that detects the rotation angle and the number of rotations of the roll body R1 or the shaft unit 12. The control unit 5 can perform feedback control of the rotation drive unit 1 using the detection signal of the rotation detection sensor. Furthermore, the control unit 5 stores the rotation angle of the roll body R1 and the circumferential position of the outer circumferential surface CS (for example, at the detected point where the height position of the outer circumferential surface CS has been displaced) at an appropriate timing based on the detection signal of the rotation detection sensor. Note that the detection unit 2 may be used as the rotation detection sensor. Furthermore, the rotation drive unit 1 is not limited to the above configuration. For example, the rotation drive unit 1 may include a delivery roller that contacts the outer circumferential surface CS of the roll body R1, and the delivery roller may be rotated by the motor 10 to rotate the roll body R1.

[0016] The detection unit 2 comprises a contactor 20 that contacts the outer peripheral surface CS of the roll body R1, a support 21 that supports the contactor 20, an elastic body 22 that presses the contactor 20 against the roll body R1 via the support 21, and a sensor body 23 that detects the displacement of the support 21.

[0017] The contactor 20 is formed in a cylindrical or disc shape, and is rotatably supported at one end of the support 21. The contactor 20 receives an appropriate pressing force from the support 21 and comes into contact with the outer peripheral surface CS of the roll body R1, and rolls on the outer peripheral surface CS as the roll body R1 rotates. For example, the contactor 20 comes into contact with the outer peripheral surface CS at a position slightly shifted toward the arrow X1 side with respect to the outer peripheral surface CS of the roll body R1 located at the lowest end in the vertical direction of the shaft portion 12 (gravity direction: arrow Z direction in FIG. 1).

[0018] The height position of the contact 20 is maintained or displaced depending on the height position of the outer circumferential surface CS during rotation of the roll body R1. If there is a convex portion c on the outer circumferential surface CS of the roll body R1 due to factors such as the leading edge rt of the roll paper RP, or the warping or undulation of the roll paper RP, the contact 20 displaces according to the convex portion c. Note that in FIG. 1, the leading edge rt of the roll paper RP and the warping ce occurring on the outer circumferential surface CS of the roll body R1, which are factors that cause the convex portion c, are exaggerated to make the present invention easier to understand.

[0019] On the other hand, the support 21 is formed in a rod shape extending linearly for a predetermined length from one end supporting the contact 20 to the other end, and the sensor body 23 is disposed on the other end side. The support 21 is rotatably supported by a fulcrum 24 in a position near the contact 20 (closer to the one end than the middle position in the extending direction of the support 21). The elastic body 22 is provided, for example, between the fulcrum 24 and the other end of the support 21, and serves as a force point that elastically pulls the support 21, thereby pressing one end (contact 20) of the support 21 toward the outer circumferential surface CS of the roll body R1. The support 21 amplifies the change in the height position of the contact 20 pressed by the elastic body 22 (displacement of the outer circumferential surface CS) from the fulcrum 24 as a starting point, and transmits it to the other end of the support 21.

[0020] A displacement sensor capable of detecting the displacement of the other end of the support 21 is applied to the sensor body 23. Examples of the displacement sensor include an encoder, a scale sensor, and a micrometer. The sensor body 23 is communicatively connected to the control unit 5, detects the position of the other end of the support 21 in response to a detection command (including a bias voltage) from the control unit 5, and transmits the detection signal to the control unit 5. The control unit 5 appropriately processes the received detection signal to recognize the maintenance or displacement of the height position of the contactor 20, that is, the height position of the outer circumferential surface CS of the roll body R1.

[0021] Furthermore, the paper feeder 100 has the separation claw 3 fixed at a position slightly offset toward the arrow X2 side with respect to the outer circumferential surface CS of the roll body R1 located at the vertically lowest end of the shaft 12 (a position sandwiching a line in the vertical direction of the shaft 12 with respect to the detector 2). The separation claw 3 has a separation end 3a that forms an acute angle toward the arrow X1 side. When the roll paper RP (feed-out section R2) rotates in the direction of the arrow B, the leading edge rt of the roll paper RP is separated vertically downward from the outer circumferential surface CS of the roll body R1, basically due to its own weight. The separation claw 3 promotes the separation of the leading edge rt of the roll paper RP from the roll body R1. The separation claw 3 may have the separation end 3a in contact with the outer circumferential surface CS of the roll body R1, or may have the separation end 3a positioned at a position slightly separated from the outer circumferential surface CS of the roll body R1.

[0022] The transport guide unit 4 is in the form of a plate capable of supporting the payout portion R2 of the roll paper RP, and one end of the transport guide unit 4 on the arrow X1 side is connected to the detection unit 2. The transport guide unit 4 extends at an angle from the detection unit 2 toward the arrow X2 side and vertically downward, so that it intersects the vertical direction of the shaft unit 12 and is located at a predetermined distance vertically downward from the separation claw unit 3. This transport guide unit 4 can guide the tip rt of the payout portion R2, which has separated from the outer circumferential surface CS of the roll body R1, so that it moves smoothly toward the arrow X2 side.

[0023] The control unit 5 includes one or more processors 50, a memory 51, an input / output interface, and an electronic circuit. The one or more processors 50 are one or a combination of a CPU, an ASIC, an FPGA, a circuit made of a plurality of discrete semiconductors, and execute a program stored in the memory 51. The memory 51 includes a non-volatile memory and a volatile memory, and forms a storage unit of the control unit 5. Note that a part of the memory 51 may be built into the one or more processors 50.

[0024] The control unit 5 performs leading edge detection processing to determine the leading edge rt of the roll paper RP when the user sets the roll paper RP in the paper feeding device 100 and before starting to feed the roll paper RP. For example, it is preferable that the control unit 5 automatically starts the leading edge detection processing when it recognizes that the roll paper RP has been set.

[0025] In the leading edge detection process, the control unit 5 operates the rotation drive unit 1 to rotate the roll body R1 in the direction of arrow A (leading edge detection rotation direction). When the leading edge rt of the roll paper RP rotates in the direction of arrow A, it rotates along the outer circumferential surface CS of the roll body R1. While the roll body R1 is rotating, the control unit 5 detects the height position of the outer circumferential surface CS of the roll body R1 using the detection unit 2. The control unit 5 then associates the height position of the outer circumferential surface CS of the roll body R1 obtained from the detection unit 2 with the measured time information and stores them in the memory 51.

[0026] Furthermore, when the leading edge detection process is started, the control unit 5 first performs low-precision sampling to detect the height position of the outer circumferential surface CS at a long sampling interval (hereinafter referred to as the first sampling interval). The first sampling interval depends on the expected size of the convex portion c and the rotation speed of the roll body R1, but may be set in the range of about 50 ms to 500 ms, for example. By detecting the height position of the outer circumferential surface CS at the first sampling interval, the control unit 5 can reduce the processing load.

[0027] 2 is a diagram illustrating detection of the outer peripheral surface CS of the roll body R1 by the detection unit 2, where Fig. 2(a) shows a case where low-precision sampling and high-precision sampling are performed, and Fig. 2(b) shows a case where only low-precision sampling is performed. As shown in Fig. 2(a), during rotation of the roll body R1, the control unit 5 detects a period in which the height position of the outer peripheral surface CS remains approximately constant, and a period in which the height position of the outer peripheral surface CS rises and falls according to the convex portion c of the outer peripheral surface CS. That is, the detection signal (height position of the outer peripheral surface CS) detected by the detection unit 2 shows a mountain-shaped shape that rises once at the convex portion c of the outer peripheral surface CS, and then falls after passing the top of the convex portion c.

[0028] Therefore, the control unit 5 judges the convex portion c where the height position of the outer circumferential surface CS becomes high based on the detection signal of low-precision sampling. For example, the control unit 5 stores a judgment threshold Th for judging the convex portion c occurring on the outer circumferential surface CS of the roll body R1 in the memory 51, and compares the height position of the outer circumferential surface CS with the judgment threshold Th. Then, when the height position of the outer circumferential surface CS is less than the judgment threshold Th, the control unit 5 judges that the convex portion c does not occur on the outer circumferential surface CS, and when the height position of the outer circumferential surface CS is equal to or greater than the judgment threshold Th, the control unit 5 judges that the convex portion c occurs on the outer circumferential surface CS.

[0029] The judgment threshold Th for judging the height position of the outer peripheral surface CS may be a fixed value or a variable value. For example, the control unit 5 may set the judgment threshold Th based on at least one of the parameters of past sampling data, paper type, temperature, and humidity. The past sampling data is the detection result when the leading edge of the roll paper RP was detected in the past, and the displacement amount and displacement time of the detected part Dc. The paper type is the type of roll paper RP (including differences in thickness, number of rolls, and width). The temperature is the temperature of the surrounding environment of the paper feeder, and the paper feeder is equipped with a temperature sensor and detects the temperature. The humidity is the humidity of the surrounding environment of the paper feeder or the setting position of the roll paper RP, and the paper feeder is equipped with a humidity sensor and detects the humidity. The control unit 5 has multiple judgment thresholds Th or correction values ​​associated with these parameters, and sets the judgment threshold Th based on the judgment threshold Th or correction value of the parameter close to the condition of the roll paper RP to be actually detected.

[0030] However, the convex portion c occurring on the outer peripheral surface CS of the roll body R1 is caused not only by the leading edge rt of the roll paper RP, but also by the deflection ce and undulation occurring on the outer peripheral surface CS of the roll body R1. In other words, the control unit 5 cannot determine whether the convex portion c is caused by the leading edge rt of the roll paper RP or a factor other than the leading edge rt just by recognizing the convex portion c based on the height position of the outer peripheral surface CS being equal to or greater than the judgment threshold Th. For this reason, the control unit 5 performs a detailed analysis of the height position of the outer peripheral surface CS at the point where the convex portion c was detected to determine whether it is the leading edge rt of the roll paper RP.

[0031] Specifically, the control unit 5 performs high-precision sampling to detect the height position of the outer circumferential surface CS at a sampling interval (hereinafter referred to as a second sampling interval) shorter than the first sampling interval for the detection points Dc of the convex portions c detected by the low-precision sampling. The second sampling interval depends on the expected size of the convex portions c and the rotation speed of the roll body R1, but may be set to, for example, in the range of about 1 / 10 to 1 / 2 of the first sampling interval.

[0032] The control unit 5 continues this high-precision sampling until the cause of the convex portion c is determined by the process described below. The period during which the high-precision sampling is performed may be set to a predetermined period from the timing when the height position of the outer peripheral surface CS becomes equal to or greater than the judgment threshold Th. The predetermined period is a period during which the height position of the outer peripheral surface CS of the convex portion c is in a generally lowered position, and may be determined by experiment or simulation. Alternatively, the period during which the high-precision sampling is performed may be set to include a surplus period from the timing when the height position of the outer peripheral surface CS, which became equal to or greater than the judgment threshold Th, becomes less than the judgment threshold Th again.

[0033] When the control unit 5 determines that the height position of the outer peripheral surface CS is equal to or greater than the determination threshold Th during low-precision sampling, the control unit 5 switches to high-precision sampling. In high-precision sampling, the control unit 5 detects the height position of the outer peripheral surface CS at the second sampling interval, thereby enabling detailed recognition of changes in the height position of the outer peripheral surface CS at the convex portion c.

[0034] That is, if there is a deflection ce or waviness in the outer peripheral surface CS, the height position of the outer peripheral surface CS will decrease at a gradual rate as it descends from the top of the convex portion c. On the other hand, if the convex portion c is the leading edge rt of the roll paper RP, the height position of the outer peripheral surface CS will decrease at a steeper rate as it descends from the top of the convex portion c. Therefore, by detecting the slope of the point where the height position of the outer peripheral surface CS descends from the top of the convex portion c, it is possible to distinguish between the leading edge rt of the roll paper RP and the deflection or waviness of the outer peripheral surface CS.

[0035] For example, the control unit 5 connects the plots of the height positions of the outer peripheral surface CS detected by high-precision sampling to virtually form a continuous change line, and compares the inclination angle θ of the change line as it descends from the apex of the convex portion c with an angle threshold Tθ pre-stored in the memory 51. As an example, the inclination angle θ may be set to the inclination of a tangent line at the point where the change line intersects with the determination threshold Th. If the inclination angle θ of the change line is equal to or greater than the angle threshold Tθ, the control unit 5 determines that the change line is the leading edge rt of the roll paper RP, and if the inclination angle θ of the change line is less than the angle threshold Tθ, the control unit 5 determines that the change line is due to a deflection ce or undulation of the outer peripheral surface CS of the roll paper RP (a factor other than the leading edge rt of the roll paper RP).

[0036] Here, referring to the detection result of the detection unit 2 using only low-precision sampling shown in Fig. 2(b), it can be said that, due to low-precision sampling, even if the control unit 5 recognizes that the height position of the outer circumferential surface CS is equal to or higher than the judgment threshold value Th, there is a possibility that the shape of the descending part of the convex portion c may be overlooked. In other words, by combining low-precision sampling and high-precision sampling, the control unit 5 can accurately detect the height position of the outer circumferential surface CS as shown in Fig. 2(a).

[0037] The determination of whether the roll paper RP is at the leading edge rt is not limited to the inclination at the time when the height position of the detected outer peripheral surface CS changes. As an example, the control unit 5 may measure the time length from the timing when the height position of the outer peripheral surface CS becomes equal to or greater than the determination threshold Th until the height position of the outer peripheral surface CS becomes less than the determination threshold Th, and compare the time length with a pre-stored time threshold. The control unit 5 may determine that the roll paper RP is at the leading edge rt when the time length is less than the time threshold, and may determine that a factor other than the leading edge rt of the roll paper RP is the cause when the time length is equal to or greater than the time threshold. Alternatively, the reference shape of the change line corresponding to the leading edge rt of the roll paper RP (or the reference shape of the deflection or waviness of the outer peripheral surface CS) may be obtained by experiment or the like, and the control unit 5 may correlate the shape of the change line of the outer peripheral surface CS during the period when high-precision sampling is performed with the reference shape. For example, the control unit 5 calculates the correlation coefficient between the shape of the change line of the outer peripheral surface CS and the reference shape of the tip rt of the roll paper RP, and if the correlation coefficient is greater than or equal to a predetermined coefficient, it determines that the tip rt of the roll paper RP is the cause, and if the correlation coefficient is less than the predetermined coefficient, it determines that the cause is a factor other than the tip rt of the roll paper RP.

[0038] When the control unit 5 determines the leading edge rt of the roll paper RP, it ends the leading edge detection process. Then, the control unit 5 rotates the roll body R1 in the direction of the arrow A using the rotation drive unit 1, and places the detected leading edge rt of the roll paper RP on the outer peripheral surface CS of the vertically lowermost end of the shaft unit 12. The leading edge rt of the roll paper RP moves away from the outer peripheral surface CS of the roll body R1 due to its own weight. Then, the paper feeder 100 rotates the roll body R1 in the direction of the arrow B (paper feed rotation direction) to start the paper feed operation of the roll paper RP. When the roll paper RP rotates in the direction of the arrow B, the leading edge rt of the roll paper RP moves away from the outer peripheral surface CS of the roll body R1 on the vertically lower side of the roll paper RP. At this time, the separation claw unit 3 may separate the leading edge of the roll paper RP. This allows the paper feeder 100 to smoothly send out the feed unit R2 of the roll paper RP between the separation claw unit 3 and the conveyance guide unit 4.

[0039] The sheet feeding device 100 according to this embodiment is basically configured as described above, and the flow of the leading edge detection process by the control unit 5 will be described in detail below.

[0040] Fig. 3 is a flowchart showing a first processing example of the control unit 5. As shown in Fig. 3, when the control unit 5 of the paper feeding device 100 starts the leading edge detection process, it first operates the rotation drive unit 1 to rotate the roll paper RP in the direction of arrow A (step S10).

[0041] Then, while the roll paper RP is rotating in the direction of arrow A, the control unit 5 performs low-precision sampling to detect the height position of the outer circumferential surface CS of the roll body R1 at a first sampling interval using the detection unit 2 (step S11).

[0042] In this low-precision sampling, the control unit 5 judges whether the height position of the outer circumferential surface CS of the roll body R1 is equal to or greater than the judgment threshold Th (step S12). If the height position of the outer circumferential surface CS is less than the judgment threshold Th (step S12: NO), the control unit 5 returns to step S11 and repeats the same process thereafter. On the other hand, if the height position of the outer circumferential surface CS is equal to or greater than the judgment threshold Th (step S12: YES), the control unit 5 proceeds to step S13.

[0043] In step S13, the control unit 5 performs high-precision sampling by detecting the height position of the outer circumferential surface CS of the roll body R1 with the detection unit 2 at second sampling intervals.

[0044] In this high-precision sampling, the control unit 5 determines whether the inclination angle θ of the outer peripheral surface CS of the convex portion c that exceeds the judgment threshold Th is greater than or equal to the angle threshold Tθ End It is determined whether the inclination angle θ is equal to or smaller than the angle threshold Tθ (step S14). less than In this case (step S14: NO), the convex portion c captured by high-precision sampling is the cause of the bending or waviness of the outer circumferential surface CS. Therefore, the control unit 5 returns to step S11 and performs low-precision sampling again.

[0045] On the other hand, the inclination angle θ is the angle threshold Tθ EndIf this is the case (step S14: YES), the convex portion c captured by high-precision sampling is the leading edge rt of the roll paper RP. Therefore, the control unit 5 proceeds to step S15, stores the determined circumferential position of the leading edge rt of the roll paper RP in the memory 51, and places the leading edge rt of the roll paper RP on the outer peripheral surface CS of the vertically lowest end of the shaft portion 12 (step S15).

[0046] When feeding paper from the paper feeding device 100, the control unit 5 operates the rotation drive unit 1 to rotate the roll paper RP in the direction of arrow B. This enables the paper feeding device 100 to smoothly guide the leading edge rt of the roll paper RP separated from the roll body R1 to the transport guide unit 4.

[0047] As described above, the paper feeding device 100 captures the change in the height position of the outer circumferential surface CS of the roll body R1 by low-precision sampling while the roll body R1 rotates once in the direction of arrow A, and then performs high-precision sampling at that timing. This enables the paper feeding device 100 to accurately detect the leading edge rt of the roll paper RP while reducing the processing load on the control unit 5.

[0048] The operation of the sheet feeding device 100 is not limited to the above process flow, and various modifications are possible. For example, the sheet feeding device 100 may continue low-accuracy sampling during the first rotation of the roll body R1 in the direction of arrow B, and perform high-accuracy sampling on one or more detection points Dc where the height position of the outer circumferential surface CS is equal to or greater than the judgment threshold value Th from the second rotation onward. The process flow of the control unit 5 in this case will be described below with reference to FIG. 4. FIG. 4 is a flowchart showing a second process example of the control unit 5.

[0049] The control unit 5 of the sheet feeding device 100 performs the same processes as steps S10 to S12 in Fig. 3 from step S20 to step S22 of the second processing example shown in Fig. 4. Then, when the height position of the outer peripheral surface CS becomes equal to or greater than the judgment threshold value Th (step S22: YES), the control unit 5 stores the detected point Dc of the outer peripheral surface CS of the roll body R1 that has become equal to or greater than the judgment threshold value Th in the memory 51 (step S23).

[0050] Thereafter, the control unit 5 determines whether the first rotation of the roll body R1 has been completed (one revolution) (step S24). If the first rotation of the roll body R1 has not been completed (step S24: NO), the control unit 5 returns to step S21 and repeats the same process flow. On the other hand, if the first rotation of the roll body R1 has been completed (step S24: YES), the control unit 5 proceeds to step S25, where the control unit 5 stops detecting the height position of the outer circumferential surface CS of the roll body R1 by low-precision sampling. At this time, the control unit 5 moves to the second rotation of the roll body R1.

[0051] In the second rotation, the control unit 5 determines whether the detection unit 2 has reached the vicinity of the detection point Dc where the height position of the outer circumferential surface CS became equal to or greater than the determination threshold Th in the first rotation (step S26). If the detection unit 2 has not reached the vicinity of the detection point Dc (step S26: NO), the control unit 5 repeats step S26, whereas if the detection unit 2 has reached the vicinity of the detection point Dc (step S26: YES), the control unit 5 proceeds to step S27.

[0052] In step S27, the control unit 5 performs high-precision sampling by using the detection unit 2 to detect the height position of the outer circumferential surface CS of the roll body R1 at the second sampling interval.

[0053] In this high-precision sampling, the control unit 5 determines whether the inclination angle θ of the outer peripheral surface CS of the convex portion c that exceeds the judgment threshold Th is greater than or equal to the angle threshold Tθ End It is determined whether the inclination angle θ is equal to or smaller than the angle threshold Tθ (step S28). less than If the tilt angle θ is equal to or smaller than the angle threshold Tθ (step S28: NO), the control unit 5 returns to step S25 and repeats the same process flow. EndIf so (Step S28: YES), the control unit 5 proceeds to Step S29. The control unit 5 then stores the determined circumferential position of the leading edge rt of the rolled paper RP in the memory 51, and positions the leading edge rt of the rolled paper RP on the outer peripheral surface CS of the vertically lowermost end of the shaft unit 12 (Step S29). Thereafter, when performing paper feeding by the paper feeding device 100, the control unit 5 operates the rotation drive unit 1 to rotate the rolled paper RP in the direction of arrow B.

[0054] As described above, the paper feeding device 100 performs low-precision sampling during the first rotation of the roll body R1, and then performs high-precision sampling on the detection location Dc during the second and subsequent rotations of the roll body R1. Even in this case, the paper feeding device 100 can reduce the processing load and accurately detect the leading edge rt of the roll paper RP.

[0055] Second Embodiment Fig. 5 is a schematic side view of sheet feeding device 100A according to the second embodiment. As shown in Fig. 5, sheet feeding device 100A may be configured to have two sensors (low-accuracy detection unit 2A that performs low-accuracy sampling and high-accuracy detection unit 2B that performs high-accuracy sampling) separately as detection unit 2. Note that the configuration of sheet feeding device 100A other than detection unit 2 is the same as the configuration of sheet feeding device 100 according to the first embodiment, and detailed description thereof will be omitted (the same applies to the following embodiments).

[0056] Specifically, the low-accuracy detection unit 2A is provided vertically above the separation claw portion 3 and on the arrow X1 side of the separation claw portion 3 (on the side farther away from the shaft portion 12 than the separation claw portion 3 along the horizontal direction). The low-accuracy detection unit 2A is connected to the control unit 5, and upon receiving a detection command from the control unit 5, detects the height position of the outer circumferential surface CS of the roll body R1 at a first sampling interval and transmits a detection signal to the control unit 5.

[0057] On the other hand, the high accuracy detection unit 2B is provided at the same position as the detection unit 2 according to the first embodiment. That is, the high accuracy detection unit 2B is provided at a position slightly shifted toward the arrow X1 side with respect to the outer peripheral surface CS at the lowermost end of the shaft portion 12 in the vertical direction (gravity direction). The high accuracy detection unit 2B is connected to the control unit 5, and upon receiving a detection command from the control unit 5, detects the height position of the outer peripheral surface CS of the roll body R1 at a second sampling interval and transmits the detection signal to the control unit 5. The low accuracy detection unit 2A and the high accuracy detection unit 2B may be the same type of sensor, or different types of sensors (for example, the high accuracy detection unit 2B having a resolution higher than that of the low accuracy detection unit 2A) may be applied.

[0058] The sheet feeding device 100A according to the second embodiment is basically configured as described above, and the flow of the leading edge detection process by the control unit 5 will be described below.

[0059] Fig. 6 is a flowchart showing a third processing example of the control unit 5. As shown in Fig. 6, when the control unit 5 of the paper feeder 100A starts the leading edge detection process, it first operates the rotation drive unit 1 to rotate the roll paper RP in the direction of arrow A (step S30).

[0060] Then, while the roll paper RP is rotating in the direction of arrow A, the control unit 5 performs low-precision sampling to detect the height position of the outer circumferential surface CS of the roll body R1 at a first sampling interval using the low-precision detection unit 2A (step S31).

[0061] In this low-precision sampling, the control unit 5 judges whether or not the height position of the outer circumferential surface CS of the roll body R1 is equal to or greater than the judgment threshold Th (step S32). If the height position of the outer circumferential surface CS is less than the judgment threshold Th (step S32: NO), the control unit 5 returns to step S31 and repeats the same process. On the other hand, if the height position of the outer circumferential surface CS is equal to or greater than the judgment threshold Th (step S32: YES), the control unit 5 stores the circumferential position of the outer circumferential surface CS equal to or greater than the judgment threshold Th as a detection point Dc in the memory 51, and proceeds to step S33.

[0062] In step S33, the control unit 5 performs high-precision sampling by the high-precision detection unit 2B on the detection point Dc where the height position of the outer circumferential surface CS detected by the low-precision detection unit 2A is equal to or higher than the judgment threshold value Th. Note that during this time, the low-precision detection unit 2A continues the low-precision sampling.

[0063] In this high-precision sampling, the control unit 5 determines whether the inclination angle θ of the outer peripheral surface CS of the convex portion c that exceeds the judgment threshold Th is greater than or equal to the angle threshold Tθ End It is determined whether the inclination angle θ is equal to or smaller than the angle threshold Tθ (step S34). less than If so (step S34: NO), the control unit 5 proceeds to step S35. In step S35, the control unit 5 stops detection (high accuracy sampling) by the high accuracy detection unit 2B, returns to step S32, and repeats the same processes thereafter.

[0064] On the other hand, the inclination angle θ is the angle threshold Tθ End If this is the case (step S34: YES), the convex portion c captured by high-precision sampling is the leading edge rt of the roll paper RP. Therefore, the control unit 5 proceeds to step S36 and stops detection by the low-precision detection unit 2A and the high-precision detection unit 2B. The control unit 5 also stores the determined circumferential position of the leading edge rt of the roll paper RP in the memory 51 and places the leading edge rt of the roll paper RP at the vertical lower end of the shaft unit 12 (step S37). Then, when the paper feeder 100A is to feed paper, the control unit 5 operates the rotation drive unit 1 to rotate the roll paper RP in the direction of arrow B. This allows the paper feeder 100A to smoothly guide the leading edge rt of the roll paper RP, which has separated from the roll body R1, to the transport guide unit 4.

[0065] As described above, even with a configuration including a low-precision detector 2A and a high-precision detector 2B, the paper feeder 100A can accurately detect the leading edge rt of the roll paper RP while reducing the processing load. In particular, the paper feeder 100A performs low-precision sampling with the low-precision detector 2A on the upstream side in the direction of the arrow A, and then performs high-precision sampling with the high-precision detector 2B on the downstream side in the direction of the arrow A. This allows the paper feeder 100A to capture the overall displacement shape of the detection point Dc of the roll body R1 with higher precision. It goes without saying that the paper feeder 100A according to the second embodiment can also perform the second processing example described above (operation in which low-precision sampling is performed on the first rotation and high-precision sampling is performed on the second rotation).

[0066] Third Embodiment 7 is a schematic side view of a paper feeder 100B according to the third embodiment. As shown in Fig. 7, the paper feeder 100B includes an arrival detector 6 in a conveyance guide 4, and a controller 5 detects the leading edge rt of the roll paper RP based on a detection signal from the detector 2 and a detection signal from the arrival detector 6.

[0067] Specifically, the reach detection unit 6 is provided vertically below the separation claw unit 3 and on the arrow X1 side of the transport guide unit 4. The reach detection unit 6 can be, for example, a non-contact sensor such as an optical sensor, or a contact sensor that detects the roll paper RP based on whether or not it is in contact with the roll paper RP.

[0068] The control unit 5 continuously performs low-precision sampling from the start of the leading edge detection process, and performs control to switch to high-precision sampling as necessary based on the detection result of the reach detection unit 6. Fig. 8 is a flowchart showing a fourth processing example of the control unit 5. Hereinafter, an example of the leading edge detection process of the control unit 5 using the reach detection unit 6 will be described with reference to Fig. 8.

[0069] The control unit 5 of the paper feeding device 100B performs the same processes as steps S10 to S12 in Fig. 3 from step S40 to step S42 of the fourth processing example. That is, the control unit 5 monitors the displacement of the height position of the outer circumferential surface CS of the roll paper RP by low-precision sampling after the start of the leading edge detection process. Then, when the height position of the outer circumferential surface CS becomes equal to or greater than the judgment threshold value Th (step S42: YES), the control unit 5 rotates the roll body R1 in the direction of arrow A, and positions the detection point Dc equal to or greater than the judgment threshold value Th on the outer circumferential surface CS at the vertically lowest end of the shaft portion 12 (step S43).

[0070] Thereafter, the control unit 5 rotates the rotation drive unit 1 in the reverse direction to rotate the roll body R1 in the direction of the arrow B (step S44).

[0071] During this rotation of the roll body R1 in the direction of arrow B, the control unit 5 determines whether the leading edge rt of the payout part R2 has reached the arrival detection unit 6 (step S45). Here, if the detected point Dc detected by low-precision sampling is the leading edge rt of the payout part R2, the arrival detection unit 6 detects the leading edge rt of the payout part R2 moving along the transport guide within a predetermined time. Therefore, when the arrival detection unit 6 detects the leading edge rt of the payout part R2 (step S45: YES), the control unit 5 ends the leading edge detection process and proceeds directly to the paper feed operation of the roll paper RP.

[0072] On the other hand, when the detection point Dc detected by low-accuracy sampling is a sagging or waviness of the outer peripheral surface CS, the arrival detection unit 6 does not detect the leading end rt of the unwinding portion R2. Therefore, when the arrival detection unit 6 does not detect the leading end rt of the unwinding portion R2 within a predetermined time (step S45: NO), the control unit 5 proceeds to step S46 and rotates the roll body R1 again in the direction of arrow A. Then, during the rotation of the roll body R1 in step S46, the control unit 5 performs high-accuracy sampling (step S47).

[0073] When high-precision sampling is performed, there is a point where the height position of the outer peripheral surface CS becomes equal to or greater than the judgment threshold Th before the arrival of the previously detected detection point Dc. Therefore, the control unit 5 determines whether the inclination angle θ of the outer peripheral surface CS is equal to or greater than the angle threshold Tθ for the point where the height position of the outer peripheral surface CS becomes equal to or greater than the judgment threshold Th in high-precision sampling. End It is determined whether the inclination angle θ is equal to or smaller than the angle threshold Tθ (step S48). less than If so (step S48: NO), the control unit 5 returns to step S47 and continues the high-precision sampling.

[0074] On the other hand, the inclination angle θ is the angle threshold Tθ End If so (Step S48: YES), the control unit 5 proceeds to Step S49. In Step S49, the control unit 5 stores the determined circumferential position of the leading edge rt of the rolled paper RP in the memory 51, and positions the leading edge rt of the rolled paper RP at the vertical bottom end of the shaft portion 12.

[0075] As described above, sheet feeding device 100B may be configured to perform sheet feeding operations by taking advantage of low-precision sampling, and to perform high-precision sampling if it determines that an abnormality has occurred in which the leading edge rt of roll sheet RP has not been conveyed to the conveyance guide section 4. In particular, when using roll sheet RP that is less prone to bending ce or undulation, sheet feeding device 100B can efficiently perform the sheet feeding operation of roll sheet RP. Of course, sheet feeding device 100B according to the third embodiment can also perform the first and second process examples described above.

[0076] 9 is a schematic side view showing another form of roll paper RP in paper feeder 100B according to the third embodiment. As shown in FIG. 9(a), when roll paper RP is set in paper feeder 100B, static electricity or the like may cause the leading edge rt to adhere to the outer peripheral surface CS of roll body R1, which may prevent it from being detected as a convex portion c by detector 2 and prevent it from being separated by separation claw 3. FIG. 9(a) illustrates a case where leading edge rt of roll paper RP adheres to outer peripheral surface CS and one convex portion c (deflection ce or undulation) is generated. Meanwhile, FIG. 9(b) illustrates a case where leading edge rt of roll paper RP adheres to outer peripheral surface CS and multiple convex portions c (deflection ce or undulation) are generated.

[0077] Considering the state of Fig. 9(a) or Fig. 9(b), it is preferable that the control unit 5 issues a warning and stops the paper feeding operation when the leading edge rt cannot be detected for a long time based on the detection signal of the detection unit 2 and the detection signal of the reach detection unit 6. The process flow of the control unit 5 in this case will be described below with reference to Figs. 10 to 12. Fig. 10 is a flowchart showing a fifth processing example of the control unit 5. Fig. 11 is a flowchart of a single-item routine in the fifth processing example. Fig. 12 is a flowchart of a multiple-item routine in the fifth processing example.

[0078] The control unit 5 of paper feeding device 100B performs steps S50 to S52 of the fifth processing example similar to steps S10 to S12 in Fig. 3. That is, after the start of the leading edge detection process, the control unit 5 monitors the displacement of the height position of the outer circumferential surface CS of the roll paper RP by low-precision sampling. Then, when the height position of the outer circumferential surface CS becomes equal to or greater than the judgment threshold value Th (step S52: YES), the control unit 5 stores the detected point Dc in the memory 51 (step S53).

[0079] The control unit 5 determines whether the first rotation of the roll body R1 has been completed (one revolution) (step S54). If the first rotation of the roll body R1 has not been completed (step S54: NO), the control unit 5 returns to step S51 and repeats the same process flow. On the other hand, if the first rotation of the roll body R1 has been completed (step S54: YES), the control unit 5 proceeds to step 55, where the control unit 5 determines whether the number of detection points Dc is one or multiple (step S55). If there is one detection point Dc (step S55: YES), the control unit 5 performs a routine for one detection point, and if there are multiple detection points Dc (step S55: NO), the control unit 5 performs a routine for multiple detection points Dc.

[0080] 11, the control unit 5 rotates the roll paper RP in the direction of arrow A and positions the detection point Dc of the roll paper RP on the outer peripheral surface CS of the vertically lowermost end of the shaft unit 12 (step S60). Next, the control unit 5 rotates the rotation drive unit 1 in the reverse direction to rotate the roll body R1 in the direction of arrow B (step S61).

[0081] During this rotation of the roll body R1 in the direction of arrow B, the control unit 5 determines whether or not the leading edge rt of the payout portion R2 has reached the arrival detection unit 6 (step S62). If the arrival detection unit 6 detects the leading edge rt of the payout portion R2 (step S62: YES), the control unit 5 ends the leading edge detection process and proceeds directly to the paper feed operation of the roll paper RP. On the other hand, if the arrival detection unit 6 does not detect the leading edge rt of the payout portion R2 within a predetermined time (step S62: NO), the control unit 5 proceeds to step S63 and again rotates the roll body R1 in the direction of arrow A. Then, during the rotation of the roll body R1 in step S63, the control unit 5 performs high-precision sampling (step S64).

[0082] During the high-precision sampling, the control unit 5 determines whether or not there is a location where the height position of the outer peripheral surface CS is equal to or greater than the judgment threshold Th (step S65). If there is a location where the height position of the outer peripheral surface CS is equal to or greater than the judgment threshold Th (step S65: YES), the control unit 5 determines whether the inclination angle θ of the outer peripheral surface CS is equal to or greater than the angle threshold Tθ for that location. EndIt is determined whether the inclination angle θ is equal to or smaller than the angle threshold Tθ (step S66). less than If so (step S66: NO), the control unit 5 returns to step S65 and continues high-precision sampling. End If so (Step S66: YES), the control unit 5 proceeds to Step S67. In Step S67, the control unit 5 stores the determined circumferential position of the leading edge rt of the rolled paper RP in the memory 51, and positions the leading edge rt of the rolled paper RP on the outer peripheral surface CS of the vertically lowermost end of the shaft portion 12 (Step S67).

[0083] Conversely, if there is no point where the height position of the outer circumferential surface CS is equal to or greater than the judgment threshold Th (step S65: NO), the control unit 5 determines that the leading edge rt of the roll paper RP is in contact with the outer circumferential surface CS. In this case, the control unit 5 outputs a warning via the notification unit (monitor, speaker, etc.) of the paper feeder 100B and stops the rotation of the roll paper RP (step S68). This allows the user of the paper feeder 100B to easily recognize that the leading edge rt of the roll paper RP is in contact with the outer circumferential surface CS.

[0084] 12, the control unit 5 first determines whether the detection point Dc closest to the conveying guide unit 4 is located downstream in the direction of arrow B (downstream in the direction of arrow A) (step S70). If the detection point Dc is located downstream in the direction of arrow B (step S70: YES), the control unit 5 rotates the roll body R1 in the direction of arrow A (step S71). On the other hand, if the detection point Dc is located downstream in the direction of arrow A (step S70: NO), the control unit 5 rotates the roll body R1 in the direction of arrow B (step S72).

[0085] The control unit 5 continuously performs high-precision sampling during the rotation in the direction of the arrow A or during the rotation in the direction of the arrow B (step S73).

[0086] Then, the control unit 5 judges whether or not there is a location where the height position of the outer peripheral surface CS is equal to or greater than the judgment threshold Th (step S74). If there is a location where the height position of the outer peripheral surface CS is equal to or greater than the judgment threshold Th (step S74: YES), the control unit 5 judges whether the inclination angle θ of the outer peripheral surface CS in that location is greater than or equal to the angle threshold Tθ. End It is determined whether the inclination angle θ of the outer peripheral surface CS is equal to or smaller than the angle threshold value Tθ less than If the inclination angle θ is equal to or smaller than the angle threshold Tθ (step S74: NO), the process returns to step S73 and the same process flow is repeated. End If this is the case (step S75: YES), the control unit 5 proceeds to step S76, stores the determined circumferential position of the leading edge rt of the roll paper RP in the memory 51, and positions the leading edge rt of the roll paper RP at the circumferential position of the vertically lowest end of the shaft portion 12.

[0087] On the other hand, if there is no point where the height position of the outer circumferential surface CS is equal to or greater than the judgment threshold Th (step S74: NO), the control unit 5 proceeds to step S77 and judges whether the roll paper RP being sampled with high accuracy has made one revolution (step S77). If the roll paper RP has not made one revolution (step S77: NO), the control unit 5 returns to step S73 and repeats the same process flow.

[0088] Conversely, if high-precision sampling of all detection points Dc is completed (step S77: YES), the leading edge rt of the roll paper RP cannot be found in all of the convex parts c that have appeared on the outer peripheral surface CS, meaning that the leading edge rt is in contact with the outer peripheral surface CS. Therefore, the control unit 5 outputs a warning via the notification unit (monitor, speaker, etc.) of the paper feeder 100B and stops the rotation of the roll paper RP (step S78). This allows the user of the paper feeder 100B to easily recognize that the leading edge rt of the roll paper RP is in contact with the outer peripheral surface CS.

[0089] As in the fifth processing example above, the control unit 5 can find the leading edge rt of the roll paper RP by performing high-precision sampling of the convex portion c of the outer circumferential surface CS. If the leading edge rt of the roll paper RP cannot be found even with high-precision sampling, the control unit 5 can output a warning to prompt the user to reset the roll paper RP or peel off the leading edge rt of the roll paper RP. The process of outputting a warning when the leading edge rt of the roll paper RP cannot be found can also be applied to the paper feeding devices 100 and 100A according to the first and second embodiments.

[0090] [Fourth embodiment] Fig. 13 is a schematic side view of sheet feeding device 100C according to the fourth embodiment. As shown in Fig. 13, sheet feeding device 100C has a detection unit 2 disposed at a position different from the position of detection unit 2 of sheet feeding device 100 according to the first embodiment. Furthermore, sheet feeding device 100C includes a reach detection unit 6, similar to sheet feeding device 100B according to the third embodiment.

[0091] Specifically, in paper feeding device 100C, detection unit 2 is located on the X1 side of roll paper RP and vertically above the center of roll paper RP. Even if detection unit 2 is located in this position, detection unit 2 can detect the leading edge rt of roll paper RP based on the change in thickness of the leading edge rt of roll paper RP relative to the thickness of the upper layer of roll paper RP relative to the thickness of the lower layer of roll paper RP at the leading edge rt of roll paper RP. In short, there is no particular limitation on the location of detection unit 2, which detects the height position of outer circumferential surface CS of roll paper RP.

[0092] The control unit 5 according to this embodiment continues low-precision sampling during the first rotation in the leading edge detection process, and determines whether to perform a second rotation in the direction of arrow A, or to rotate the roll paper RP in the direction of arrow B to feed the feed unit R2, depending on the position of the detected point Dc at this time. Figure 14 is a flowchart showing part of the sixth processing example of the control unit 5. Figure 15 is a flowchart showing the other part of the sixth processing example of the control unit 5.

[0093] The control unit 5 of paper feeding device 100C performs the same processes as steps S10 to S12 in Fig. 3 from step S80 to step S82 of the sixth processing example shown in Fig. 14. That is, after the start of the leading edge detection process, the control unit 5 monitors the displacement of the height position of the outer circumferential surface CS of the roll paper RP by low-precision sampling. Then, when the height position of the outer circumferential surface CS becomes equal to or greater than the judgment threshold value Th (step S82: YES), the control unit 5 stores the detected point Dc in the memory 51 (step S83).

[0094] The control unit 5 determines whether the first rotation of the roll body R1 has been completed (one revolution) (step S84). If the first rotation of the roll body R1 has not been completed (step S84: NO), the control unit 5 returns to step S81 and repeats the same process flow thereafter. On the other hand, if the first rotation of the roll body R1 has been completed (step S84: YES), the control unit 5 proceeds to step S85.

[0095] In step S85, the control unit 5 determines whether the number of detection points Dc is more than one. If the number of detection points Dc is one (step S85: NO), the control unit 5 executes the routine for one point shown in FIG. 11 (step S86). On the other hand, if the number of detection points Dc is more than one (step S85: YES), the control unit 5 proceeds to step S87.

[0096] In step S87, it is determined whether or not there is a detected point Dc among the multiple detected points Dc that is closer to the transport guide section 4 than the detection unit 2. If there is a detected point Dc that is closer to the transport guide section 4 than the detection unit 2 (step S87: YES), it is more efficient to feed paper to the transport guide section 4 for that detected point Dc. For this reason, as shown in FIG. 15, the control unit 5 places the detected point Dc that is closer to the transport guide section 4 on the outer peripheral surface CS at the lowermost vertical end of the shaft section 12 (step S88), and further rotates the roll paper RP in the direction of arrow B (step S89).

[0097] Then, the control unit 5 determines whether the leading edge rt of the payout unit R2 has reached the arrival detection unit 6 (step S90). If the arrival detection unit 6 detects the leading edge rt of the payout unit R2 (step S90: YES), the control unit 5 ends the leading edge detection process and proceeds directly to the feeding operation of the roll paper RP. On the other hand, if the arrival detection unit 6 does not detect the leading edge rt of the payout unit R2 within a predetermined time (step S90: NO), the control unit 5 proceeds to step S91 and rotates the roll body R1 in the direction of arrow A again.

[0098] During the rotation of the roll body R1 in step S91, the control unit 5 performs high-precision sampling (step S92). When high-precision sampling is performed, there is a point where the height position of the outer circumferential surface CS becomes equal to or greater than the judgment threshold value Th before the detection point Dc where the paper is fed arrives. Therefore, the control unit 5 determines whether the inclination angle θ of the outer circumferential surface CS is equal to or greater than the angle threshold value Tθ for the point where the height position of the outer circumferential surface CS becomes equal to or greater than the judgment threshold value Th in the high-precision sampling. End It is determined whether or not (step S93).

[0099] The tilt angle θ is the angle threshold Tθ less than If this is the case (step S93: NO), the control unit 5 proceeds to step S94 and determines whether or not the roll paper RP has rotated one revolution in the second rotation. If the roll paper RP has not rotated one revolution (step S94: NO), the control unit 5 returns to step S92 and continues high-precision sampling. On the other hand, if the roll paper RP has rotated one revolution, the control unit 5 determines that it was unable to find the leading edge rt of the roll paper RP, and outputs a warning via the notification unit of the paper feeder 100C (step S95).

[0100] The tilt angle θ is the angle threshold Tθ End If this is the case (step S93: YES), the control unit 5 proceeds to step S96, stores the determined circumferential position of the leading edge rt of the roll paper RP in the memory 51, and positions the leading edge rt of the roll paper RP at the vertical lower end of the shaft portion 12 (step S96).

[0101] Returning to step S87, if there is no detected point Dc closer to the transport guide unit 4 than the detection unit 2 (step S87: NO), the control unit 5 proceeds to step S97. In step S97, the control unit 5 performs high-precision sampling with the detection unit 2 while rotating the roll paper RP in the direction of arrow A from the beginning (while performing the second rotation).

[0102] In this high-precision sampling, the control unit 5 determines whether the inclination angle θ of the outer peripheral surface CS of the convex portion c that exceeds the judgment threshold Th is greater than or equal to the angle threshold Tθ End It is determined whether the inclination angle θ is equal to or smaller than the angle threshold Tθ (step S98). less than If so (step S98: NO), the control unit 5 proceeds to step S97, and thereafter repeats the same processing.

[0103] On the other hand, the inclination angle θ is the angle threshold Tθ End If so (Step S98: YES), the control unit 5 determines the leading edge rt of the rolled paper RP and proceeds to Step S99. The control unit 5 then places the leading edge rt of the rolled paper RP on the outer peripheral surface CS of the vertically lowermost end of the shaft portion 12 (Step S99).

[0104] In this way, sheet feeding device 100C can increase the possibility of performing a sheet feeding operation early by changing the operation for detection point Dc detected by low-precision sampling depending on the proximity between detection unit 2 and transport guide unit 4. Note that the sixth processing example is also applicable to sheet feeding devices 100, 100A, and 100B according to the first to third embodiments.

[0105] Fig. 16 is an explanatory diagram showing an image forming apparatus 200 to which the paper feeders 100, 100A to 100C according to the first to fourth embodiments are applied. As shown in Fig. 16, the image forming apparatus 200 has a conveying section 210, a first image forming section 220, a turn bar 230, a second image forming section 240, a sensor section 250, and a control device 260. While conveying the roll paper RP by the conveying section 210, the image forming apparatus 200 forms a full-color image on a first side of the roll paper RP by the first image forming section 220, and forms a full-color image on a second side of the roll paper RP opposite to the first side by the second image forming section 240.

[0106] The transport section 210 has any one of the paper feeding devices 100, 100A-100C according to the first to fourth embodiments (paper feeding device 100 will be described below as an example), as well as a winding section 211, and transports the payout portion R2 of the roll paper RP. Paper feeding device 100 pays out the payout portion R2 of the roll paper RP, causing the payout portion R2 to run and transport the roll paper RP toward the first image forming unit 220. The winding section 211 winds the payout portion R2 around a rotated roll to wind it up, and transports the payout portion R2 from the second image forming unit 240 toward the winding section 211.

[0107] The first image forming section 220 has a first liquid ejection unit 221 and a first drying unit 222. The first liquid ejection unit 221 ejects yellow (Y), magenta (M), cyan (C) and black (K) liquids individually. The first drying unit 222 dries the liquid applied to the first surface of the feed section R2 by rotating the first heating drum while contacting the second surface of the feed section R2 with the surface of the first heating drum having a built-in heater. That is, the first image forming section 220 ejects liquid from the first liquid ejection unit 221 to the feed section R2 being conveyed based on image data input to the image forming apparatus 200. Then, the liquid applied to the feed section R2 is dried by the first drying unit 222 to form a full-color image on the first surface of the feed section R2.

[0108] The turn bar 230 turns over the face of the pay-out portion R2 after it has been sent out from the outlet portion of the first drying unit 222, and sends the pay-out portion R2 into the inlet portion of the second image forming portion 240.

[0109] The second image forming section 240 has a second liquid ejection unit 241 and a second drying unit 242. The second liquid ejection unit 241 ejects yellow (Y), magenta (M), cyan (C) and black (K) liquids individually. The second drying unit 242 dries the liquid applied to the second surface of the feed section R2 by rotating the second heating drum while contacting the first surface of the feed section R2 with the surface of the second heating drum having a built-in heater. That is, the second image forming section 240 ejects liquid from the second liquid ejection unit 241 to the feed section R2 being conveyed based on image data input to the image forming apparatus 200. Then, the liquid applied to the feed section R2 is dried by the second drying unit 242 to form a full-color image on the second surface of the feed section R2.

[0110] The sensor section 250 has a first transmissive optical sensor 251, a second transmissive optical sensor 252, and a third transmissive optical sensor 253, and outputs a detection signal according to the state of the feed section R2 being transported.

[0111] The control device 260 has a processor, a memory, an electric circuit board, etc., and controls the conveyance by the conveying unit 210 and the image formation operations of the first image forming unit 220 and the second image forming unit 240. For example, the control device 260 controls the conveyance and stop of conveyance of the pay-out unit R2 by the conveying unit 210 based on detection signals outputted from each of the first transmissive optical sensor 251, the second transmissive optical sensor 252, and the third transmissive optical sensor 253. The control device 260 may include the control unit 5 of the sheet feeding device 100, or may be provided separately from each other.

[0112] In the image forming apparatus 200 described above, the feeding unit R2 is fed by the feeding operation of the sheet feeding device 100, so that an image can be formed while the feeding unit R2 is being transported.

[0113] Although the embodiments have been described above, the present invention is not limited to the above specifically disclosed embodiments, and various modifications and changes are possible without departing from the scope of the claims.

[0114] As described above, by performing low-precision sampling at the start of leading edge detection processing, paper feeder 100C can narrow down detection points Dc where the height position of the outer circumferential surface CS of roll paper RP changes while reducing the processing load. Then, paper feeder 100C can accurately detect the leading edge rt of roll paper RP by performing high-precision sampling based on detection points Dc detected by low-precision sampling.

[0115] The control unit 5 also determines whether the height position of the outer peripheral surface CS detected by low-precision sampling is equal to or greater than the judgment threshold Th, and identifies the location where the height position of the outer peripheral surface CS is equal to or greater than the judgment threshold Th as the detection location Dc. This allows the sheet feeding device 100 to easily extract the convex portion c where the height position of the outer peripheral surface CS is displaced.

[0116] Furthermore, the control unit 5 calculates the slope of the drop in the detection point Dc based on multiple plots obtained by sampling the detection point Dc using high-precision sampling, and determines whether the detection point Dc is the leading edge rt of the roll paper RP based on the slope, which allows the paper feeder 100C to detect the leading edge rt of the roll paper RP with even greater accuracy.

[0117] Furthermore, the control unit 5 sets the determination threshold value Th based on at least one of the parameters of past sampling data, paper type, temperature, and humidity, thereby enabling the control unit 5 to appropriately set the determination threshold value Th and to more accurately determine the height position of the outer circumferential surface CS.

[0118] Furthermore, when the control unit 5 detects the detection point Dc by low-precision sampling, the control unit 5 immediately performs high-precision sampling on the detection point Dc, thereby enabling the paper feeding device 100C to shorten the time it takes to detect the leading edge rt of the roll paper RP.

[0119] Furthermore, the control unit 5 performs low-precision sampling during the first rotation of the roll paper RP by the rotation drive unit 1, and performs high-precision sampling on the detection point Dc detected by the low-precision sampling during the first rotation onward during the second rotation of the roll paper RP by the rotation drive unit 1. This enables the paper feeding device 100C to detect the leading edge rt of the roll paper RP with even greater accuracy.

[0120] Further, the detection unit 2 includes a low-accuracy detection unit 2A that performs low-accuracy sampling and a high-accuracy detection unit 2B that performs high-accuracy sampling, and performs high-accuracy sampling by the high-accuracy detection unit 2B on the detection point Dc detected by the low-accuracy detection unit 2A. This allows the sheet feeding device 100C to operate the low-accuracy detection unit 2A and the high-accuracy detection unit 2B individually at appropriate timing, thereby enabling the detection point Dc to be monitored more accurately.

[0121] Also, there is provided an arrival detection unit 6 that detects the arrival of the roll paper RP when the roll paper RP is fed to the transport guide unit 4, and when the control unit 5 detects the detection point Dc in the low-precision sampling, it starts a feeding operation to pay out the roll paper RP based on the detected detection point Dc before high-precision sampling, and if the arrival detection unit 6 does not detect the arrival of the roll paper RP after the feeding operation, it performs high-precision sampling. As a result, paper feeding device 100C performs high-precision sampling when the roll paper RP does not reach the arrival detection unit 6, thereby improving the efficiency of the feeding operation of the roll paper RP.

[0122] Furthermore, when multiple detection points Dc are detected by performing low-precision sampling during the first rotation of the roll paper RP, the control unit 5 determines whether or not the detection point Dc is located closer to the transport guide unit 4 than the detection unit 2, and starts the paper feeding operation if the detection point Dc is located closer to the transport guide unit 4 than the detection unit 2. If the arrival detection unit 6 does not detect the arrival of the roll paper RP after the paper feeding operation, high-precision sampling is performed. This allows paper feeding device 100C to start feeding paper in a shorter time if the roll paper RP can be fed by the feeding operation of the detection point Dc that is closer to the transport guide unit 4 than the detection unit 2. On the other hand, if the roll paper RP cannot be fed, paper feeding device 100C can detect the leading edge rt of the roll paper RP by high-precision sampling.

[0123] Furthermore, when control unit 5 detects one detection point Dc by performing low-precision sampling during the first rotation of roll paper RP, it starts the paper feeding operation, and when arrival detection unit 6 does not detect the arrival of roll paper RP after the paper feeding operation, it performs high-precision sampling. Even in this case, paper feeding device 100C can start paper feeding in a shorter time.

[0124] Furthermore, when control unit 5 detects multiple detection points Dc by performing low-precision sampling during the first rotation of roll paper RP, it guides the detection point Dc closest to transport guide unit 4 to transport guide unit 4 to start the paper feeding operation, and performs high-precision sampling if arrival detection unit 6 does not detect the arrival of roll paper RP after the paper feeding operation. Even in this case, paper feeding device 100C can accurately detect the leading edge rt of roll paper RP while reducing the processing load.

[0125] Another aspect of the present invention is an image forming apparatus 200 having the above-mentioned paper feeders 100, 100A to 100C. In the image forming apparatus 200, the leading edge of the roll paper RP is accurately detected by the paper feeders 100, 100A to 100C, so that the conveyance of the payout section R2 can be stably performed. [Explanation of symbols]

[0126] 1 Rotation drive unit 10 Motor 11 Drive transmission section 12 Shaft 2. Detection section 2A Low-precision detector 2B High-precision detector 20 Contact 21 Support 22 Elastic Body 23 Sensor body 3 Separation claw part 4 Transport guide section 5. Control section 50 processors 51 Memory 6 Arrival detection unit c Convex part ce Deflection CS outer surface Dc Detection point RP Roll Paper R1 Roll body R2 Payout section rt tip [Prior art documents] [Patent documents]

[0127] [Patent Document 1] JP 2006-273446 A

Claims

1. A rotation drive unit that rotates the roll-shaped recording medium; a detection unit that detects a height position of an outer peripheral surface of the rolled recording medium while the rolled recording medium is rotating; a control unit that performs a leading edge detection process to detect a leading edge of the rolled recording medium based on a detection signal from the detection unit, The control unit is At the start of the leading end detection process, the detection unit is operated at a first sampling interval to perform low-precision sampling to detect a detection point where a height position of the outer circumferential surface is displaced; performing high-precision sampling by operating the detection unit at a second sampling interval that is shorter than the first sampling interval, based on the detection location detected by the low-precision sampling; determining whether or not the height position of the outer circumferential surface detected by the low-precision sampling is equal to or greater than a determination threshold, and identifying a location where the height position of the outer circumferential surface is equal to or greater than the determination threshold as the detection location; Based on a plurality of plots obtained by sampling the detected portion by the high-precision sampling, a slope at which the detected portion descends is calculated, and the angle of the slope is compared with an angle threshold. If the angle of the slope is equal to or greater than the angle threshold, the detected portion is determined to be the leading end of the rolled recording medium, and if the angle of the slope is less than the angle threshold, the detected portion is determined to be not the leading end of the rolled recording medium. A paper feeding device characterized by:

2. The detection unit includes a low-precision detection unit that performs the low-precision sampling and a high-precision detection unit that performs the high-precision sampling, The high-precision detection unit performs the high-precision sampling on the detection target portion detected by the low-precision detection unit.

2. The paper feeder according to claim 1.

3. A reach detection unit that detects when the rolled recording medium has arrived at a conveying guide unit when the rolled recording medium is fed to the conveying guide unit, The control unit is when the detection target portion is detected in the low-precision sampling, a paper feed operation for unwinding the roll-shaped recording medium based on the detected detection target portion is started prior to the high-precision sampling; When the arrival detection unit does not detect the arrival of the roll-shaped recording medium after the paper feeding operation, the high-precision sampling is performed.

2. The paper feeder according to claim 1.

4. The control unit sets the determination threshold value based on at least one parameter selected from past sampling data, paper type, temperature, and humidity parameters.

4. The paper feeder according to claim 1, wherein the paper feeder is a paper feeder having a paper feed mechanism.

5. The control unit is When the detection portion is detected by the low-precision sampling, the high-precision sampling is immediately performed on the detection portion.

5. The paper feeder according to claim 1, wherein the paper feeder is a paper feeder having a paper feed mechanism.

6. A rotation drive unit that rotates a roll-shaped recording medium; a detection unit that detects a height position of an outer peripheral surface of the rolled recording medium while the rolled recording medium is rotating; a control unit that performs a leading edge detection process to detect a leading edge of the rolled recording medium based on a detection signal from the detection unit, The control unit is At the start of the leading end detection process, the detection unit is operated at a first sampling interval to perform low-precision sampling to detect a detection location where a height position of the outer circumferential surface is displaced during a first rotation of the rolled recording medium by the rotation drive unit; After the second rotation of the roll-shaped recording medium by the rotation drive unit, high-precision sampling is performed by operating the detection unit at a second sampling interval shorter than the first sampling interval for the detection location detected by the low-precision sampling in the first rotation. A paper feeding device characterized by:

7. A rotation drive unit that rotates a roll-shaped recording medium; a detection unit that detects a height position of an outer peripheral surface of the rolled recording medium while the rolled recording medium is rotating; a control unit that performs a leading edge detection process to detect a leading edge of the rolled recording medium based on a detection signal from the detection unit, The control unit is At the start of the leading end detection process, the detection unit is operated at a first sampling interval to perform low-precision sampling to detect a detection point where a height position of the outer circumferential surface is displaced; performing high-precision sampling by operating the detection unit at a second sampling interval that is shorter than the first sampling interval, based on the detection location detected by the low-precision sampling; the detection unit includes a low-precision detection unit that performs the low-precision sampling and a high-precision detection unit that performs the high-precision sampling, The high-precision detection unit performs the high-precision sampling on the detection target portion detected by the low-precision detection unit. A paper feeding device characterized by:

8. A rotation drive unit that rotates a roll-shaped recording medium; a detection unit that detects a height position of an outer peripheral surface of the rolled recording medium while the rolled recording medium is rotating; a control unit that performs a leading edge detection process to detect a leading edge of the rolled recording medium based on a detection signal from the detection unit, an arrival detection unit that detects arrival of the rolled recording medium when the rolled recording medium is fed to a transport guide unit; The control unit is At the start of the leading end detection process, the detection unit is operated at a first sampling interval to perform low-precision sampling to detect a detection point where a height position of the outer circumferential surface is displaced; performing high-precision sampling by operating the detection unit at a second sampling interval that is shorter than the first sampling interval, based on the detection location detected by the low-precision sampling; when the detection target portion is detected in the low-precision sampling, a paper feed operation for unwinding the roll-shaped recording medium based on the detected detection target portion is started prior to the high-precision sampling; When the arrival detection unit does not detect the arrival of the roll-shaped recording medium after the paper feeding operation, the high-precision sampling is performed. A paper feeding device characterized by:

9. The control unit is When a plurality of detection points are detected by performing the low-precision sampling during a first rotation of the roll-shaped recording medium, it is determined whether or not the detection point is located closer to the transport guide unit than the detection unit; starting the paper feeding operation when the detected portion is located closer to the conveying guide portion than the detection portion; When the arrival detection unit does not detect the arrival of the roll-shaped recording medium after the paper feeding operation, the high-precision sampling is performed.

9. The paper feeder according to claim 8.

10. The control unit is when one of the detection points is detected by performing the low-precision sampling during a first rotation of the roll-shaped recording medium, the paper feeding operation is started; When the arrival detection unit does not detect the arrival of the roll-shaped recording medium after the paper feeding operation, the high-precision sampling is performed.

9. The paper feeder according to claim 8.

11. The control unit is When a plurality of detection points are detected by performing the low-precision sampling during a first rotation of the roll-shaped recording medium, The detected portion closest to the transport guide portion is guided to the transport guide portion to start the paper feeding operation. When the arrival detection unit does not detect the arrival of the roll-shaped recording medium after the paper feeding operation, the high-precision sampling is performed.

9. The paper feeder according to claim 8.

12. An image forming apparatus comprising the paper feeder according to any one of claims 1 to 11.

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