Sheet supply device and image forming apparatus

Abstract

To provide a sheet feeder which determines a sheet setting direction by use of a detection configuration of a sheet tip.SOLUTION: A sheet feeder comprises: a sensor which projects toward a roll from a face-to-face part, is urged in a direction contacting an outer peripheral surface of the roll, and outputs a detection signal with a signal level depending on the amount of projection; and a controller which controls rotating means on the basis of a signal change ratio that is the amount of change of a signal level of the detection signal per unit time. The controller rotates a spool in a take-up direction by the rotating means, and stops the motion of the rotating means when the signal change ratio based on change in a relative positional relationship between the outer peripheral surface and the sensor when the tip of a sheet does not pass the position of the sensor does not exceed a predetermined reverse setting threshold.SELECTED DRAWING: Figure 16

Description

[Technical Field]

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

[0002] Image forming apparatuses are known that are equipped with a sheet supply device that supplies a long sheet (hereinafter referred to as "continuous sheet") wound on a winding cylinder (spool), and that form an image of the supplied continuous sheet. In sheet supply devices, a sheet supply mechanism is already known in which, after the user manually inserts the leading end of the continuous sheet (hereinafter referred to as "sheet leading end") into the supply section, the device detects the leading end and then performs the sheet supply operation.

[0003] In conventional sheet feeding mechanisms, a technique is known in which the spool is rotated in the direction of winding the continuous sheet, the leading edge of the detached sheet is detected by a sensor, and after detecting the leading edge, the spool is rotated forward in the direction of unwinding the continuous sheet (see, for example, Patent Document 1). [Overview of the project] [Problems that the invention aims to solve]

[0004] In the technology disclosed in Patent Document 1, rotation in the winding direction of the continuous sheet is called reverse rotation, and rotation in the unwinding direction of the continuous sheet is called forward rotation. In a sheet supply mechanism using the prior art, if the spool is set in the wrong direction and reversed, the sheet's leading edge cannot be detected by the reverse rotation. In this case, the reverse rotation continues without stopping because the sheet's leading edge is not detected. As a result, the leading edge of the continuous sheet is unwinded from the spool in the opposite direction to the supply direction, leading to problems such as damage to the sheet.

[0005] The present invention aims to provide a technology for determining the setting direction of a sheet using a detection configuration at the leading edge of a sheet in a sheet supply device that supplies a long sheet wound on a spool. [Means for solving the problem]

[0006] To solve the above problems, one aspect of the present invention provides a support portion for supporting a roll formed by winding a long sheet onto a spool; a rotating means for rotating the spool supported by the support portion in an unwinding direction for unwinding the sheet from the spool and in a winding direction for winding the sheet onto the spool; a guide member having a facing portion that faces the outer circumferential surface of the roll and a guide portion extending from the facing portion toward the unwinding direction for the sheet; and an end of the guide member, with the downstream end in the unwinding direction as the pivot point, in a direction that moves the facing portion toward or away from the outer circumferential surface. The Ga The rotating means comprises a support shaft that rotatably supports the side member, a biasing member that biases the rotation of the guide member in a direction that brings the facing portion closer to the roll, a sensor that protrudes from the facing portion toward the roll and is biased in a direction that contacts the outer circumferential surface of the roll, and outputs a detection signal with a signal level corresponding to the amount of protrusion, a roller supported by the facing portion and contacting the outer circumferential surface of the roll at a position different from the sensor in the circumferential direction of the roll, and a controller that controls the rotating means based on the signal change rate, which is the amount of change in the signal level of the detection signal per unit time, wherein the controller rotates the spool in the winding direction by the rotating means, and the signal change rate is based on the change in the relative positional relationship between the outer circumferential surface and the sensor when the leading edge of the sheet does not pass the position of the sensor The first rate of change, which is the rate of change of the signal due to immersion, which is the displacement of the sensor in the direction away from the rotation axis of the roll, and the second rate of change, which is the rate of change of the signal due to protrusion, which is the displacement of the sensor in the direction approaching the rotation axis of the roll, are provided between the first rate of change and the fluctuation range of the detection signal of the sensor, without exceeding the first rate of change. The operation of the rotating means is stopped when the predetermined reverse set threshold is not exceeded. [Effects of the Invention]

[0007] According to the present invention, in a sheet supply device that supplies a long sheet wound on a spool, it is possible to determine if the sheet is set in the wrong direction. [Brief explanation of the drawing]

[0008] [Figure 1] External perspective view of the image forming apparatus according to this embodiment. [Figure 2] A cross-sectional view showing the internal structure of an image forming apparatus. [Figure 3]Schematic configuration diagram of a sheet feeding device. [Figure 4] Perspective view of a guide arm. [Figure 5] Enlarged view of the periphery of the facing part. [Figure 6] Diagram showing the positional relationship between the tip of the continuous sheet, the tip detection sensor, and the roller. [Figure 7] Diagram showing the transition of the signal level of the detection signal of the tip detection sensor. [Figure 8] Diagram showing an example when the continuous sheet is reversely set and the tip detection process is started. [Figure 9] Diagram showing an example of the displacement of the detection signal of the tip detection sensor when the continuous sheet is reversely set. [Figure 10] Diagram explaining the threshold value used when detecting the reverse setting of the continuous sheet. [Figure 11] Diagram showing another example when the continuous sheet is reversely set and the tip detection process is started. [Figure 12] Diagram showing the transition of the signal level of the detection signal of the tip detection sensor when the continuous sheet is reversely set. [Figure 13] Diagram showing the positional relationship between the sheet tip, the tip detection sensor, and the roller when the continuous sheet is reversely set. [Figure 14] Hardware configuration diagram of an image forming apparatus. [Figure 15] Flowchart of sheet setting processing. [Figure 16] Flowchart of tip detection processing. [Figure 17] Diagram showing the transition of the signal level of the detection signal in tip detection processing. [Figure 18] Flowchart of alternative detection processing. [Figure 19] Flowchart of the first reverse set detection processing. [Figure 20] Flowchart of the second reverse set detection processing. [Figure 21] Diagram showing another example of the transition of the detection signal level in the second reverse set detection processing. <> [Figure 22] Diagram explaining the conventional method of setting roll paper. [Modes for carrying out the invention]

[0009] [Embodiments of the present invention] Hereinafter, a printer 1 as an embodiment of the image forming apparatus according to the present invention will be described with reference to Figures 1 and 2. Figure 1 is an external perspective view of the printer 1 according to this embodiment. Figure 2 is a cross-sectional view showing the internal structure of the printer 1.

[0010] As shown in Figure 1, the printer 1, as an embodiment of the image forming apparatus, comprises a central cover 2, right covers 3 and left covers 4 located at both ends of the elongated central cover 2, side plates 5 located at the outer ends of the right cover 3 and left cover 4, and an operation cover 6 that opens and closes relative to the central cover 2. The external shape of the printer 1 is formed by these covers (right cover 3 and left cover 4, side plates 5, and operation cover 6). The printer 1 is also supported by legs 7 provided near both ends in the elongated direction of the main body of the apparatus, which is covered by each cover. Casters are installed on the legs 7 to facilitate movement.

[0011] The printer 1 according to this embodiment is an inkjet-type image forming apparatus that ejects liquid ink onto a continuous sheet P, which is a long sheet, to form an image on the continuous sheet P. However, the image forming method of the printer 1 is not limited to the inkjet method, and may be an electrophotographic method or the like.

[0012] As shown in Figure 2, the printer 1 mainly comprises a sheet supply unit 10, a transport unit 20, an image forming unit 30, a winding unit 40, and a controller 50 as a control unit, as an embodiment of the sheet supply device according to the present invention. The detailed configuration of the controller 50 will be described later with reference to Figure 8.

[0013] The sheet supply unit 10 supplies the continuous sheet P, wound on the spool 8 (winding cylinder), to the transport unit 20 via the transport path L. The transport path L is the space inside the printer 1 through which the continuous sheet P passes. More specifically, the transport path L is the route from the sheet supply unit 10 through the transport unit 20 and the image forming unit 30 to the winding unit 40. Details of the sheet supply unit 10 will be described later with reference to Figures 3 to 7.

[0014] The transport unit 20 transports the continuous sheet P supplied from the sheet supply unit 10 through the transport path L to the winding unit 40, passing through a position facing the image forming unit 30. The transport unit 20 mainly comprises a transport roller 21, a pressure roller 22, and a transport motor 23. The transport roller 21 and the pressure roller 22 grip the continuous sheet P from both sides in the thickness direction and rotate. The transport roller 21 rotates when the driving force of the transport motor 23 is transmitted. The pressure roller 22 is pressed against the transport roller 21 with a predetermined pressure and moves in conjunction with the rotation of the transport roller 21.

[0015] The image forming unit 30 is located downstream of the transport unit 20 in the transport direction of the continuous sheet P. The image forming unit 30 forms an image on the continuous sheet P by ejecting ink onto the continuous sheet P transported by the transport unit 20. The image forming unit 30 mainly comprises a recording head 31, a carriage motor 32, a platen 33, and a main scanning carriage 34.

[0016] The main scanning carriage 34 moves back and forth in the main scanning direction, which is perpendicular to the transport direction of the continuous sheet P, by the driving force transmitted from the carriage motor 32. The main scanning carriage 34 is also equipped with recording heads 31 that eject liquid inks of black (k), cyan (c), magenta (m), and yellow (y). More specifically, it is equipped with a recording head 31k that ejects black ink, a recording head 31c that ejects cyan ink, a recording head 31m that ejects magenta ink, and a recording head 31y that ejects yellow ink.

[0017] Each of the recording heads 31 ejects liquid ink of its respective color toward the continuous sheet P supported by the platen 33, according to instructions from the controller 50. Generally, the recording heads 31 eject liquid ink toward the direction of gravity. Therefore, the positional relationship between the main scanning carriage 34 and the platen 33 is vertical in the direction of gravity. That is, the platen 33 is located below the opposing main scanning carriage 34. The platen 33 then supports the continuous sheet P transported by the transport unit 20.

[0018] The winding unit 40 is located downstream of the conveying unit 20 and the image forming unit 30 in the conveying direction of the continuous sheet P. The winding unit 40 winds up the continuous sheet P on which the image has been formed by the image forming unit 30. The winding unit 40 mainly comprises a winding roller 41 and a winding motor 42. The winding roller 41 rotates in the direction of winding up the continuous sheet P after the image has been formed, by the driving force transmitted from the winding motor 42.

[0019] Here, the conventional method of setting roll paper will be explained with reference to Figure 22. The roll paper has flanges (flange members) at the widthwise ends, and a spool is set on them. The user sets the roll paper with the spool on the paper feed receiving section (spool bearing base) of the device (Figure 22(A)), finds the leading edge of the roll paper, and while holding the edge, rotates the roll paper with both hands as shown in Figure 22(B) so that the leading edge of the paper comes towards the user. Next, the user positions the leading edge of the paper between the guide plates at the back of the roll paper and inserts the roll paper while rotating it (Figure 22(C)). Once the user inserts the paper into the guides, the paper is fixed inside and pulled into the device.

[0020] As shown in Figure 22(C), the guide plate for inserting the leading edge of the paper is located behind the roll of paper, making it difficult to see and confirm whether the paper has been inserted correctly.

[0021] Furthermore, as shown in Figures 22(D) and 22(E), in a device with a two-tiered roll paper setting section, when a roll of paper is already set in the upper tier, if a roll of paper is to be set in the lower tier and the leading edge is to be inserted between the guide plates, the guide plates become even more difficult to see because the roll of paper in the upper tier is already there, increasing the difficulty of setting the paper and the risk of inserting it at an angle.

[0022] In the conventional method of setting roll paper as described above, it was a time-consuming process because it was difficult to confirm insertion when finding the leading edge of the roll paper and inserting it in the transport direction, and it was necessary to insert the leading edge of the paper evenly. Furthermore, if the leading edge of the paper was not inserted evenly, it would be fed at an angle, causing skew, which would require repeating the operation or cause jams, adding even more hassle.

[0023] The sheet supply device according to the present invention solves the above-mentioned problems. It also solves the problem that arises when the direction in which the roll paper is set into the paper feeding receiving section (spool bearing base) of the device is reversed. The sheet supply section 10 as an embodiment of the sheet supply device according to the present invention will be described in detail below with reference to the drawings.

[0024] Figure 3 is a schematic diagram of the sheet supply unit 10. Figure 4 is a perspective view of the guide arm 13 provided by the sheet supply unit 10. As shown in Figures 2 to 4, the sheet supply unit 10 mainly comprises a support unit 11, a supply motor 12, a guide arm 13, a support shaft 14, a coil spring 15, a tip detection sensor 16, a plurality of rollers 17 (right roller 17a, left roller 17b), a cutter 18, and a guide plate 19 (upper guide plate 19a, lower guide plate 19b).

[0025] The support section 11 supports a roll 9, which is formed by winding a continuous sheet P around a shaft-shaped spool 8. The support section 11 detachably supports the roll 9. The support section 11 also rotatably supports both ends of the spool 8.

[0026] The supply motor 12, acting as a rotating means, rotates the spool 8, supported by the support section 11, in a predetermined rotational direction. The rotation of the spool 8 by the supply motor 12 is distinguished into "forward rotation," which rotates the spool in the direction of the feed direction R1, which feeds out the continuous sheet P, and "reverse rotation," which rotates the spool in the direction of the winding direction R2, which winds up the continuous sheet P.

[0027] The guide arm 13, acting as a guide member, brings the tip detection sensor 16 and rollers 17 (right roller 17a, left roller 17b) into contact with the roll 9, and also guides the continuous sheet P unwound from the roll 9 between the guide plates 19. The guide arm 13 has an elongated plate-like outer shape. The guide arm 13 has a facing portion 13a and a guiding portion 13b.

[0028] The opposing portion 13a has an arc shape that follows the outer circumferential surface of the roll 9. The opposing portion 13a faces the outer circumferential surface of the roll 9 below the horizontal line passing through the rotation center of the spool 8. The guide portion 13b extends from the opposing portion 13a downstream in the direction of continuous sheet P supply. More specifically, the opposing portion 13a is positioned to face the region including the lower end of the roll 9 (lower region), and the guide portion 13b extends from the opposing portion 13a to a position between the guide plate 19.

[0029] The support shaft 14 extends in the same direction as the extension direction of the spool 8 supported by the support portion 11. The support shaft 14 is fixed inside each cover. The support shaft 14 is also attached to the downstream end of the guide portion 13b in the direction of continuous sheet P supply, and rotatably supports the guide arm 13. That is, the guide arm 13 is configured to rotate around the support shaft 14 as the pivot point, in a direction that brings the opposing portion 13a into contact with or away from the roll 9.

[0030] Furthermore, the coil spring 15, acting as a biasing member, biases the guide arm 13 in a direction that brings the opposing portion 13a closer to the roll 9.

[0031] The tip detection sensor 16 protrudes from the opposing portion 13a toward the roll 9. Furthermore, the tip detection sensor 16 is supported such that the amount of protrusion from the opposing portion 13a changes as the relative positional relationship between the opposing portion 13a and the opposing surface of the roll 9 changes. In addition, the tip detection sensor 16 is biased toward contacting the outer circumferential surface of the roll 9 (i.e., protruding from the opposing portion 13a). The tip detection sensor 16 outputs a detection signal to the controller 50 with a signal level corresponding to the amount of protrusion from the opposing portion 13a. More specifically, the greater the amount of protrusion of the tip detection sensor 16 toward the roll 9 relative to the opposing portion 13a, the greater the signal level of the detection signal. Conversely, the less the amount of protrusion of the tip detection sensor 16 relative to the opposing portion 13a (the greater the amount of immersion in the opposing portion 13a), the smaller the signal level of the detection signal.

[0032] Multiple rollers 17 are rotatably supported on the opposing section 13a. The rotation axis of each roller 17 extends in the same direction as the extension direction of the spool 8 and the support shaft 14. The rollers 17 are positioned in a different location from the tip detection sensor 16 in the circumferential direction of the roll 9. For example, in the example in Figure 3, the rollers 17 are positioned upstream of the tip detection sensor 16 in the winding direction R2. Furthermore, the rollers 17 are spaced apart in the width direction perpendicular to the circumferential direction of the roll 9, with the tip detection sensor 16 positioned between the right roller 17a and the left roller 17b.

[0033] Although not shown in Figure 3, the cutter 18 cuts the leading edge of the continuous sheet P across its entire width. The cutting line made by the cutter 18 extends in a direction perpendicular to the supply direction of the continuous sheet P. In other words, when the leading edge of the continuous sheet P is skewed relative to the supply direction, cutting the leading edge of the continuous sheet P with the cutter 18 makes the leading edge of the continuous sheet P perpendicular to the supply direction.

[0034] The guide plates 19 (upper guide plate 19a, lower guide plate 19b) are positioned downstream of the guide arm 13 in the direction of continuous sheet P supply. The upper guide plate 19a and the lower guide plate 19b are positioned opposite each other across the transport path L. The continuous sheet P, moving along the guide arm 13, passes between the upper guide plate 19a and the lower guide plate 19b and is supplied to the transport section 20. In other words, the guide plates 19 serve as a paper feed section into which the continuous sheet P unwound from the roll 9 enters.

[0035] [Explanation of setting Roll 9 in the correct orientation] First, we will explain the detection operation of the leading edge of the continuous sheet P (hereinafter referred to as "sheet leading edge") when the roll 9 is set in the correct orientation and then the spool 8 is rotated in the winding direction R2. Figures 5 to 7 are a series of diagrams illustrating the relationship between the position of the sheet leading edge and the signal level of the detection signal output by the leading edge detection sensor 16. Figure 5 is an enlarged view of the area around the facing portion 13a. Figure 6 is a diagram showing the positional relationship between the sheet leading edge and the leading edge detection sensor 16 and roller 17. Figure 7 is a diagram showing the change in the signal level of the detection signal from the leading edge detection sensor 16 over time.

[0036] Since the guide arm 13 is biased toward the roll 9 by the coil spring 15 acting as a biasing member, the tip detection sensor 16 and the roller 17 are in contact with the outer circumferential surface of the roll 9, as shown in Figure 5. Furthermore, when the spool 8 is rotated in the winding direction R2, the leading edge of the sheet, which is in close contact with the outer circumferential surface of the roll 9, passes the roller 17, and then, due to further rotation in the winding direction R2, passes the tip detection sensor 16. In the following description, as shown in Figure 5, the area before the leading edge of the sheet passes the roller 17 is referred to as "region α". The area after the leading edge of the sheet passes the roller 17 and before it passes the tip detection sensor 16 is referred to as "region β". The area after the leading edge of the sheet passes the tip detection sensor 16 is referred to as "region γ".

[0037] Figure 6(A) shows the state where the leading edge of the sheet is in region α. ​​Figure 6(B) shows the state where the leading edge of the sheet is in region β. First, as shown in Figures 6(A) and 6(B), when the leading edge of the sheet passes the roller 17, the guide arm 13 rotates by the thickness of the continuous sheet P in the direction in which the roller 17 contacts the outer surface of the roll 9. As a result, the leading edge detection sensor 16 retracts into the opposite portion 13a by the thickness of the continuous sheet P. In other words, the amount of protrusion of the leading edge detection sensor 16 decreases as the leading edge of the sheet passes the roller 17.

[0038] Figure 6(C) shows the state when the leading edge of the sheet reaches region γ. As shown in Figures 6(B) and 6(C), when the leading edge of the sheet passes the leading edge detection sensor 16, the roller 17 comes into contact with the outer surface of the continuous sheet P, creating a gap equivalent to the thickness of the continuous sheet P. As a result, the leading edge detection sensor 16 protrudes from the opposite portion 13a by an amount equivalent to the thickness of the continuous sheet P. In other words, the amount of protrusion of the leading edge detection sensor 16 increases as the leading edge of the sheet passes the leading edge detection sensor 16.

[0039] Figure 7(A) shows the change in the detection signal of the tip detection sensor 16 when the roll 9 rotates in the winding direction R2 so that the sheet tip moves from Figure 6(A) to Figures 6(B) and 6(C). That is, as shown in Figure 7(A), the detection signal of the tip detection sensor 16 is a High signal before the sheet tip passes the roller 17 (region α), and a Low signal after the sheet tip passes the roller 17 (region β). Note that the High signal has a higher signal level than the Low signal. In other words, the detection signal of the tip detection sensor 16 decreases in signal level when the sheet tip passes the roller 17 (right roller 17a, left roller 17b).

[0040] Furthermore, after the leading edge of the sheet passes the leading edge detection sensor 16 (region γ), the detection signal of the leading edge detection sensor 16 changes from a LOW signal to a High signal. In other words, the detection signal of the leading edge detection sensor 16 increases in level as a result of the leading edge of the sheet passing the leading edge detection sensor 16.

[0041] Here, as shown in Figure 7(B), when we microscopically observe the change in the signal level of the detection signal, we see that as the sheet tip passes through roller 17, the detection signal of the tip detection sensor 16 decreases by signal level y1 during time x1. Also, as the sheet tip passes through tip detection sensor 16, the detection signal of tip detection sensor 16 increases by signal level y2 during time x2.

[0042] Hereinafter, the rate of change per unit time of the signal level of the detection signal will be referred to as the "rate of change of signal". The rate of change of signal when the tip detection sensor 16 is submerged will be referred to as the first rate of change, and the rate of change of signal when the tip detection sensor 16 is protruding will be referred to as the second rate of change. Furthermore, as will be described in detail later, the rate of change per unit time of the signal level of the detection signal generated when the roll 9 is rotated in the winding direction R2 with the roll 9 incorrectly set will be referred to as the reverse set rate of change.

[0043] Furthermore, the first signal change rate K1 = |y1 / x1| when the leading edge of the sheet passes the roller 17 exceeds a predetermined first threshold when the roll 9 is rotated in the winding direction R2, provided that the roll 9 is properly set. Also, the second signal change rate K2 = |y2 / x2| when the leading edge of the sheet passes the leading edge detection sensor 16 exceeds a predetermined second threshold when the roll 9 is rotated in the winding direction R2, provided that the roll 9 is properly set. The first and second thresholds may be the same value or different values.

[0044] [Explanation of what happens when Roll 9 is set in the opposite direction to its correct orientation] As described above, when the roll 9 is set in the correct orientation, the continuous sheet P is wound onto the spool 8 in the opposite direction to the winding direction R2. In this case, the leading edge of the sheet is facing the opposite direction to the winding direction R2, resulting in the change in the detection signal shown in Figure 7.

[0045] In contrast, if roll 9 is set in the opposite direction to its correct orientation, the leading edge of the sheet will be facing the winding direction R2 of roll 9. This state is referred to as "reverse setting." When the reverse-set roll 9 is rotated in the winding direction R2, the change in the detection signal of the leading edge detection sensor 16 does not occur in the same way as in Figure 7, which has already been explained. Therefore, the leading edge detection process, which is based on the signal change sequence in Figure 7, cannot be performed while the roll is in the reverse setting.

[0046] Furthermore, it is possible to detect a reverse set using the change in the detection signal of the tip detection sensor 16 when the roll 9 is rotated in the winding direction R2. Therefore, by also detecting a reverse set when performing the tip detection processing of the roll 9, it is possible to address the issue and ensure that the tip detection processing can be executed normally.

[0047] Figure 8 shows an example of the state when roll 9 is rotated in the winding direction R2 with the roll set in reverse. When roll 9 is rotated in the winding direction R2 with the roll set in reverse, unlike when it is set in the correct orientation, the method of detecting the first signal change rate K1 and then the second signal change rate K2, as shown in Figure 7, cannot detect that the leading edge of the sheet has passed the leading edge sensor 16. As a result, the reverse rotation of roll 9 (rotation in the winding direction R2) continues without stopping.

[0048] If the sheet's leading edge passes the leading edge detection sensor 16 but the rotation in the winding direction R2 continues, the leading edge of the continuous sheet P will protrude outside the guide arm 13, as illustrated in Figure 8. As a result, the continuous sheet P may be bent or damaged, forcing it to be discarded, leading to waste. To avoid such waste, when detecting the leading edge of the sheet, it is necessary to also detect reverse setting.

[0049] Even if the roll 9 is set up in reverse, the detection signal of the tip detection sensor 16 changes according to the rotation of the roll 9. Figure 9 shows an example of the change in the detection signal of the tip detection sensor 16 when rotation in the winding direction R2 continues even in the state shown in Figure 8. When the reversed roll 9 continues to rotate in the winding direction R2, the sheet tip does not pass the roller 17 or the tip detection sensor 16, so the first signal change rate K1 is not detected as in the case of a proper setup.

[0050] Instead, as shown in Figure 9, the change is within a range corresponding to the width of the irregularities on the outer surface of the continuous sheet P. Furthermore, this range of change is not a rate of change corresponding to the first signal change rate K1 or the second signal change rate K2, but rather a rate of change smaller than these.

[0051] Therefore, as shown in Figure 10, a threshold (reverse set threshold KR) for detecting a reverse set is provided between the rate of change of the detection signal of the tip detection sensor 16 (first signal change rate K1) when the tip of the sheet passes the roller 17 when it is set in the correct orientation (when the tip of the sheet moves from region α to region β), and the fluctuation range of the detection signal of the tip detection sensor 16, which corresponds to the width of the unevenness of the outer surface of the sheet as illustrated in Figure 9.

[0052] For example, when the sheet is rotated in the winding direction R2, if the rate of change of the detection signal of the tip detection sensor 16 is not detected at a level corresponding to the first signal change rate K1 or the second signal change rate K2, and the reverse set threshold KR is also not exceeded, it is determined that the sheet is reversed. By providing a reverse set threshold KR, the reverse set can be detected with a single rotation in the winding direction R2 without having to repeatedly rotate the sheet in the winding direction R2 to detect the sheet tip.

[0053] Furthermore, as illustrated in Figure 11, it is conceivable that when the roll 9 is set in reverse, the leading edge of the continuous sheet P may be in close contact with the outer surface. In this case, Figure 12 illustrates the displacement of the detection signal output by the leading edge detection sensor 16 during rotation in the winding direction R2.

[0054] As shown in Figure 12, this is the reverse of the example in Figure 7(A). In this case, the leading edge of the sheet is not detected, so the rotation of the roll 9 in the winding direction R2 continues.

[0055] Figure 13 shows the positional relationship between the leading edge of the continuous sheet P, the leading edge detection sensor 16, and the roller 17 when the roll 9 is set in reverse. Figure 13(A) shows the state where the leading edge of the sheet is in region α. ​​Figure 13(B) shows the state where the leading edge of the sheet is in region β. First, from the state before the leading edge of the sheet passes the roller 17 (Figure 13(A)), when the leading edge of the sheet passes the roller 17 (Figure 13(B)), the position of the roller 17 relative to the outer surface of the roll 9 is displaced by the thickness of the continuous sheet P in the direction away from the outer surface of the roll 9. As a result, the guide arm 13 rotates by the thickness of the continuous sheet P, and the leading edge detection sensor 16 protrudes from the opposite part 13a by the thickness of the continuous sheet P. In other words, the amount of protrusion of the leading edge detection sensor 16 increases as the leading edge of the sheet passes the roller 17.

[0056] Up to Figure 13(B), the tip detection sensor 16 is in contact with the outer surface of the roll 9. As the roll 9 rotates in this state, the tip detection sensor 16 outputs a detection signal corresponding to the minute displacement of the outer surface.

[0057] Next, Figure 13(C) shows the state where the leading edge of the sheet has reached region γ. As the roll 9 rotates in the winding direction R2 from the state in Figure 13(B) to the state in Figure 13(C), the leading edge of the sheet passes the leading edge detection sensor 16. As a result, the leading edge detection sensor 16 is retracted into the opposite portion 13a by an amount equivalent to the thickness of the continuous sheet P. In other words, the amount of protrusion of the leading edge detection sensor 16 decreases as the leading edge of the sheet passes the leading edge detection sensor 16.

[0058] Therefore, when the roll 9 is rotated in the winding direction R2 with the roll set in reverse, the detection signal of the tip detection sensor 16 does not change as it would in the correct set state, but changes in the opposite direction. However, since the first signal change rate K1 and the second signal change rate K2, which represent the rate of change, are treated as absolute values, a comparison is made between these absolute values ​​and the reverse set threshold KR to determine whether the rate of change corresponding to the first signal change rate K1 and the second signal change rate K2 exceeds the reverse set threshold KR. By making this determination, it is possible to determine if the roll is set in reverse even if the leading edge of the continuous sheet P is in close contact with the outer surface.

[0059] [Hardware configuration of Printer 1] Next, the hardware configuration of printer 1, which performs the processes that enable sheet leading edge detection and reverse set detection as described above, will be explained using Figure 14. As shown in Figure 14, printer 1 has a configuration in which a CPU (Central Processing Unit) 51 as a control means, RAM (Random Access Memory) 52 as a storage means, ROM (Read Only Memory) 53 as a storage means, HDD (Hard Disk Drive) 54 as a storage means, and an I / F 55 as an interface are connected via a common bus 56 as a communication means. The CPU 51, RAM 52, ROM 53, and HDD 54 are examples of controllers 50.

[0060] The CPU 51 is the processing unit and controls the overall operation of the printer 1. The RAM 52 is a volatile storage medium that allows for high-speed reading and writing of information and is used as a workspace for the CPU 51 when processing information. The ROM 53 is a read-only, non-volatile storage medium that stores programs such as firmware. The HDD 54 is a non-volatile storage medium that allows for reading and writing of information and has a large storage capacity, and stores the OS (Operating System), various control programs, application programs, etc.

[0061] Printer 1 processes various programs loaded from ROM 53 and HDD 54 into RAM 52 using the arithmetic functions of the CPU 51. This processing constitutes a software control unit that includes various functional modules of Printer 1. The combination of this software control unit and the hardware resources installed in Printer 1 constitutes a functional block that realizes the functions of Printer 1.

[0062] I / F55 is an interface that connects the sheet supply unit 10, transport unit 20, image forming unit 30, winding unit 40, and operation panel (input unit) 57 to the common bus 56. In other words, the controller 50 controls the sheet supply unit 10, transport unit 20, image forming unit 30, winding unit 40, and operation panel 57 through I / F55.

[0063] The control panel 57 is a user interface equipped with a display that shows various information to be communicated to the operator, and buttons, switches, dials, etc., that accept operations from the operator. The control panel 57 may also be equipped with a touch panel superimposed on the display. It accepts operations from the operator and outputs an operation signal corresponding to the accepted operation to the controller 50.

[0064] [Sheet setting process in Printer 1] Next, with reference to Figure 15, the sheet setting process that can be performed in printer 1 will be explained. Figure 9 is a flowchart of the sheet setting process. The sheet setting process is the process of preparing the continuous sheet P wound on the roll 9 so that it can be supplied to the transport unit 20 through the guide plates 19 when a new roll 9 is attached to the support unit 11.

[0065] During the sheet setting process, the roll 9 is rotated in the winding direction R2 (the roll 9 is rotated in the reverse direction). As previously explained, the controller 50 controls the rotational operation and direction of the supply motor 12 based on the rate of change of the signal from the tip detection sensor 16 when the roll 9 rotates in the reverse direction. The sheet setting process is initiated, for example, when the installation of the roll 9 is detected, or when an operation indicating that the roll 9 has been replaced is received through the operation panel 57. The timing of the installation of the roll 9 is based on the detection signal from the sensor that detects the installation of the roll 9.

[0066] When the sheet setting process begins, the tip detection process is executed (S1501). Details of the tip detection process will be described later. The controller 50 then determines whether or not the tip of the sheet was successfully detected in the tip detection process (S1502).

[0067] If the controller 50 determines that it has successfully detected the leading edge of the sheet (S1502: YES), it reverses the rotation of the supply motor 12, thereby rotating the spool 8 in the winding direction R2 by a predetermined rotation angle (for example, about 355°) from the passing timing determined by the leading edge detection process (S1503). As a result, the leading edge of the sheet reaches the supply start position.

[0068] The passing timing refers to the timing when the leading edge of the sheet passes the leading edge detection sensor 16. The supply start position is the position upstream of the leading edge detection sensor 16 and roller 17 in the winding direction and facing the guide section 13b. In other words, the supply start position is the position where, by rotating the spool 8 in the unwinding direction, the continuous sheet P is supplied along the guide section 13b toward the guide plate 19.

[0069] Next, the controller 50 rotates the supply motor 12 in the forward direction to supply the continuous sheet P along the guide section 13b from the supply start position (S1504). As a result, the continuous sheet P passes between the guide plates 19 and is held between the transport roller 21 and the pressure roller 22.

[0070] Once the sheet setting process is successfully completed, the printer 1 can perform an image formation process to form an image on the continuous sheet P. Specifically, the controller 50 drives the transport motor 23 to transport the continuous sheet P to a position facing the recording head 31. Next, the controller 50 drives the carriage motor 32 to move the main scanning carriage 34 in the main scanning direction and simultaneously ejects liquid ink of each color from the recording head 31. By repeating this process, an image is recorded on the continuous sheet P. Furthermore, the controller 50 drives the take-up motor 42 to wind the continuous sheet P with the recorded image onto the take-up roller 41.

[0071] On the other hand, if the controller 50 determines that it has failed to detect the leading edge of the sheet (S1502: NO), it stops the supply motor 12 and displays an error on the control panel 57, which acts as a notification unit (S1505). As a result, the operator performs the appropriate task (for example, reattaching the roll 9) according to the content of the error displayed on the control panel 57.

[0072] [Front-end detection process in printer 1] Next, the details of the leading edge detection process included in the sheet setting process will be explained with reference to Figures 16 to 21, describing the details of the leading edge detection process that is performed in step S1501 of Figure 15 to detect the leading edge of the sheet. Figure 16 is a flowchart of the leading edge detection process. Figure 17 is a diagram showing the change in the signal level of the detection signal when the roll 9 is set in the correct orientation. Figure 21 is a diagram showing the change in the signal level of the detection signal when the roll 9 is set in the wrong direction. Figure 18 is a flowchart of the alternative detection process. Figure 19 is a flowchart of an example of the reverse set detection process performed during the execution of the leading edge detection process. Figure 20 is a flowchart of another example of the reverse set detection process performed during the execution of the leading edge detection process. Note that during the execution of the leading edge detection process and the alternative detection process, the roll 9 rotates in the winding direction R2.

[0073] The tip detection process shown in Figure 16 is a process that determines the passing timing based on both the first signal change rate K1 and the second signal change rate K2. Furthermore, if the roll 9 is set in reverse, the process of detecting the sheet tip will be executed repeatedly, and the stop condition will not be met. Therefore, in the tip detection process according to this embodiment, it is first determined whether or not the roll 9 is set in reverse, and if it is not set in reverse, the sheet tip detection is performed, and if it is set in reverse, the process of stopping the rotation of the roll 9 is executed.

[0074] The alternative detection process shown in Figure 18 is a process that determines the passage timing based solely on the second signal change rate K2. In this embodiment, the passage timing is first determined by the tip detection process, and if the passage timing cannot be determined by the tip detection process, the alternative detection process is executed. However, the tip detection process and the alternative detection process may be executed independently.

[0075] Returning to Figure 16, in the tip detection process, first the controller 50 initializes (=1) the variables R and N stored in the RAM 52 (S1601). Variable R indicates the number of times the spool 8 was rotated in the tip detection process. Variable N indicates the number of times the passing timing was determined in the tip detection process.

[0076] Next, the controller 50 executes the first reverse set detection process (S1602). If it is determined in S1602 that the roll 9 is in a reverse set state, the tip detection process is stopped (terminated). If it is determined in the first reverse set detection process (S1602) that the roll 9 is not in a reverse set state, then the roll 9 is in a normal set state, and the process moves from S1602 to S1603. Details of the process in S1602 will be described later.

[0077] Next, the controller determines whether the change in the detected signal corresponds to the first signal change rate K1 (S1603). The controller 50 repeats S1603 until it detects the first signal change rate K1 (S1603: NO) and until the second time t2 has elapsed (S1604: NO).

[0078] Next, when the controller 50 detects the first signal change rate K1 (S1603:Yes), it executes a process to detect the second signal change rate K2 (S1605). At this time, the detection of the first signal change rate K1 indicates that the leading edge of the sheet is passing the roller 17 or the leading edge detection sensor 16. However, there is a possibility that the leading edge of the sheet is in an inverted state without peeling off from the outer surface of the roll 9. Therefore, after detecting K1, the controller executes a second inverted set detection process until K2 is detected (S1605:NO) (S1606). If the second inverted set detection process (S1606) does not detect that the roll 9 is in an inverted set state, the controller waits for the first time t1 to elapse (S1607:NO) before executing subsequent processes. Details of the second inverted set detection process will be described later.

[0079] The controller 50 determines that the leading edge of the sheet has passed the leading edge detection sensor 16 if the second signal change rate K2 exceeds the second threshold before the first time t1 has elapsed (S1607: NO) (S1605: YES).

[0080] Here, we will explain the monitoring in the first time t1 and the second time t2 using Figure 17. As shown in Figure 17, the first time t1 is a predetermined time corresponding to the distance between the roller 17 and the tip detection sensor 16. More specifically, the first time t1 is the time required for the roll 9 to rotate by the distance between them, plus a margin. The second time t2 is the time required for the roll 9 to complete one rotation, plus a positive margin. The third time range t3 is a predetermined time range included in the second time t2. More specifically, the third time range t3 is the time range that goes back a predetermined amount of time from the timing when the second time t2 has elapsed (the end of the second time t2). Even more specifically, the third time range t3 is a time range within the second time t2 that includes a ± margin around the timing when the sheet tip is expected to pass the tip detection sensor 16.

[0081] Return to Figure 16. When the second signal change rate K2 is detected (S1605: YES), the controller 50 interacts with the variable N and the judgment threshold X. thCompare them (S1608).

[0082] Next, when the variable N is less than the determination threshold value X th (S1608: NO), the controller 50 increments the variable N by 1 (S1609) and executes the processing after step S1603 again. Then, when the variable N reaches the determination threshold value X th (S1608: YES), the controller 50 ends the leading edge detection process assuming that the leading edge of the sheet has been successfully detected.

[0083] That is, while the second time t2 elapses X th times (S1608: No), when the passing timing is determined within the third time range t3 included in each of the X th times of the second time t2 (S1605: Yes), the process of step S1603 is executed at the X th th passing timing. The determination threshold value X th is a value for determining whether the number of times of detecting the leading edge of the sheet exceeds a predetermined number of times. The determination threshold value X th may be a predetermined fixed value, or an operation of inputting the value of N may be received through the operation panel 57. The determination threshold value X th may be 1 or may be 2 or more.

[0084] On the other hand, before the first signal change rate K1 is detected, when the second time t2 has elapsed (S1603: NO & S1604: YES), or when the first signal change rate K1 is detected outside the third time range t3, the controller 50 compares the variable R with the rotation threshold value R th (S1610). Similarly, before the second signal change rate K2 is detected (S1605: NO), when the first time t1 has elapsed without being stopped by the reverse set (S1607: YES), the controller 50 compares the variable R with the rotation threshold value R th (S1610).

[0085] Then, the controller 50 determines that the variable R is the rotation threshold value R thIf the value is less than (S1610: NO), the variable R is incremented by 1 (S1611), and the processing from step S1603 onwards is executed again.

[0086] Next, the controller 50 sets the variable R to the rotation threshold R. th If this condition is reached (S16010:YES), the detection of the sheet tip by the tip detection process is deemed to have failed, and an alternative detection process is executed (S1612).

[0087] In other words, the controller 50 controls the roll 9 in the winding direction R th If the first and second rate of change cannot be detected before rotation (S1610:NO), and the reversed set state is not determined, then the alternative detection process is executed (S1612). Rotation threshold R th This value is used to determine whether the number of sheet tip detection failures from the start of tip detection processing to the alternative detection processing (S1612) exceeds a predetermined number. Rotation threshold R th The rotation threshold R may be a predetermined fixed value, or the operator may accept input of the value of R through the control panel 57. th It can be 1, or 2 or more.

[0088] [Alternate detection process in printer 1] Next, the details of the substitution detection process (S1611) will be explained. As shown in Figure 18, the controller 50 initializes (=1) the variables R and N stored in RAM 52 (S1801). Note that the variables R and N, and the judgment threshold X th , and rotation threshold R th The definition is the same as that for tip detection processing.

[0089] Next, the controller 50 waits to execute subsequent processes until the second signal change rate K2 of the detection signal exceeds the second threshold (S1802) or until the second time t2 has elapsed (S1803). Then, during the period until the second time t2 has elapsed (S1803: NO), if the second signal change rate K2 exceeds the second threshold within a predetermined third time range t3 (S1802: YES), the controller 50 determines that the leading edge of the sheet has passed the leading edge detection sensor 16 (i.e., the passing timing has occurred).

[0090] Next, when the controller 50 determines the timing of passage (S1802:YES), it sets the variable N and the determination threshold X. th The following is compared (S1804). Next, the controller 50 determines that the variable N is the judgment threshold X. th If it is less than (S1804: NO), the variable N is incremented by 1 (S1805), and the process from step S1802 onwards is executed again. Then, the controller 50 determines that the variable N is less than the judgment threshold X th If the second time t2 is X (S1804:YES), the alternative detection process is terminated, indicating that the detection of the sheet tip was successful. That is, the controller 50 determines that the second time t2 is X th During the time elapsed (S1804:NO), X th If the second rate of change exceeds the second threshold within the third time range t3 included in each of the second time intervals t2, then X th The timing at which the second rate of change exceeds the second threshold is determined as the passing timing.

[0091] On the other hand, if the second time t2 has elapsed before the second signal rate of change K2 exceeds the second threshold (S1802: NO & S1803: YES), or if the second signal rate of change K2 exceeds the second threshold outside the third time range t3, the controller 50 will check the variable R and the rotation threshold R th This is compared (S1806). Next, the controller 50 sets the variable R to the rotation threshold R. th If it is less than (S1806: NO), the variable R is incremented by 1 (S1807), and the processing from step S1802 onwards is executed again. Then, the controller 50 determines that the variable R is less than the rotation threshold R thIf this condition is reached (S1806:YES), the detection of the leading edge of the sheet by the alternative detection process fails, and the alternative detection process is terminated.

[0092] [First process for detecting reverse set in printer 1] Next, the details of the first reverse set detection process (S1602) will be explained with reference to Figure 19. First, the controller 50 determines whether the rate of change of the detection signal exceeds the reverse set threshold KR (see Figure 10) (S1901). If the rate of change of the detection signal exceeds the reverse set threshold KR (S1901: NO), the roll 9 is properly set, so the first reverse set detection process ends in order to return to the sheet tip detection process.

[0093] When the rate of change of the detection signal does not exceed the inverse set threshold KR (S1901: YES), the presence or absence of a detection signal is determined from the tip detection sensor 16 (S1902).

[0094] If a detection signal is output from the tip detection sensor 16 (S1902: YES), the roll 9 is in the reversed set state, so the controller 50 stops the operation of the transport drive system including the supply motor 12 (S1903). Then, the controller 50 outputs warning information to the operation panel 57 to notify it that the roll is in the reversed set state (S1904).

[0095] If no detection signal is output from the tip detection sensor 16 (S1902: NO), the tip detection sensor 16 may be malfunctioning, so the controller 50 stops the operation of the transport drive system including the supply motor 12 (S1905). The controller 50 then outputs warning information to the operation panel 57 to notify it of "tip detection sensor malfunction" (S1906).

[0096] [Second process for detecting reverse set in printer 1] Next, the details of the second reverse set detection process (S1606) will be explained with reference to Figure 20. First, the controller 50 determines whether or not the second signal change rate K2 has been detected between the time the first signal change rate K1 is detected (S1603: YES) and the third time range t3 has elapsed (S2001).

[0097] Here, the third time range t3 in the second reverse set detection process will be explained using Figure 21. As shown in Figure 21, the third time range t3 is a predetermined time range included in the second time t2, which is the time from when the roll 9 rotates and the first signal change rate K1 is detected until the second signal change rate K2 is detected, with a positive margin added. More specifically, the third time range t3 is the time range that goes back a predetermined amount of time from the timing when the second time t2 has elapsed (the end of the second time t2). Even more specifically, the third time range t3 is also a time range within the second time t2 that has a ± margin added to the timing when the leading edge of the sheet is expected to pass the leading edge detection sensor 16.

[0098] Therefore, if the second signal change rate K2 is detected between the time the first signal change rate K1, which is detected when the leading edge of the sheet passes the roller 17, is detected and the third time range t3 has elapsed (S2001: YES), it is determined that the roll 9 is in the reversed set state. In this case, the controller 50 stops the operation of the transport drive system, including the supply motor 12 (S2002). The controller 50 then outputs warning information to the operation panel 57 to notify it that the roll is in the reversed set state (S2003).

[0099] If the second signal change rate K2 is not detected (S2001: NO), it is determined that roll 9 is in a normal state and not in an inverted set state. In this case, the second inverted set detection process is terminated (S2004), and the process moves to S1607.

[0100] According to the above embodiment, for example, the following effects are achieved.

[0101] According to the above embodiment, the problem that occurs when the roll 9 is set in the reverse position during the process of detecting the leading edge of the continuous sheet P can be resolved. More specifically, in the sheet leading edge detection process, regardless of whether the leading edge of the sheet is peeling away from the outer surface of the roll 9 or in close contact with it, the process is stopped if the reverse position is determined before the sheet is rotated multiple times during the sheet leading edge detection process.

[0102] This prevents the leading edge of the sheet from coming out in the opposite direction to the feeding direction, which would make the continuous sheet difficult to use. It also prevents damage to the leading edge of the sheet from repeated rotation while in close contact with the outer surface.

[0103] The printer 1 according to this embodiment can also detect the leading edge of the sheet while it is in close contact with the outer surface of the roll 9, so it can reliably detect the leading edge of the sheet regardless of the thickness, stiffness, curling condition, etc. of the continuous sheet P. Furthermore, simply by attaching the roll 9 to the support unit 11, the leading edge is automatically detected and inserted between the guide plates 19, so the continuous sheet P can be reliably inserted between the guide plates 19 compared to when the operator manually inserts the continuous sheet P.

[0104] Furthermore, according to the above embodiment, the timing at which the second signal change rate K2 exceeds the second threshold is determined as the passing timing, before the first time t1 has elapsed after the first signal change rate K1 exceeds the first threshold. This prevents the unevenness of the roll 9 from being mistakenly detected as the leading edge of the sheet.

[0105] Furthermore, according to the above embodiment, the leading edge of the sheet is X th Since detection is repeated multiple times, the detection accuracy improves. Also, the judgment threshold X th By having the operator set this, for example, if the continuous form sheet P is thin, the judgment threshold X th Increase the threshold X if the continuous sheet P is thick. th This allows for a reduction in size. As a result, both detection accuracy and throughput can be achieved.

[0106] Furthermore, when the leading edge of the sheet is inclined with respect to the supply direction, the rate of change of the first signal K1 when the leading edge of the sheet passes through the roller 17 tends to be smaller. Therefore, as in the above embodiment, when the leading edge of the sheet cannot be properly detected by the leading edge detection process, an alternative detection process is performed, making it possible to properly detect the leading edge of the continuous sheet P regardless of the degree of inclination.

[0107] Furthermore, the reverse set detection process in the printer 1 according to this embodiment can automatically detect reverse set of the roll 9 by setting a threshold value for the amount of change in the sensor output per unit time of the sensor signal for reverse set detection to detect reverse set of the continuous sheet P. When reverse set is detected, the printer 1 stops operating and a warning is displayed on the operation panel 57, so that the operator can take timely action and prevent waste of continuous sheet P. In addition, even when the leading edge of the continuous sheet P is set in reverse on the roll 9 while in close contact with the outer surface, this can be detected. In this case, the operator's work efficiency can be improved without unnecessarily continuing the leading edge detection process.

[0108] It should be noted that the present invention is not limited to the embodiments described above, and various modifications are possible without departing from the technical essence, and all technical matters included in the technical concept described in the claims are subject to the present invention. The above embodiments are shown as preferred examples, but those skilled in the art can realize various modifications from the disclosed content. Such modifications are also included in the technical scope described in the claims. [Explanation of symbols]

[0109] 1: Printer 8: Spool 9: Roll 10: Sheet supply unit 11: Support part 12: Supply motor 13: Guide Arm 13a: Face-to-face section 13b: Information department 14: Support shaft 15: Coil spring 16: Advanced detection sensor 17: Koro 18: Cutter 19: Guide board 20: Conveyor Unit 21: Conveyor roller 22: Pressure roller 23: Conveyor motor 30: Image forming unit 31: Recording head 32: Carriage Motor 33: Platen 34: Main scanning carriage 40: Winding section 41: Winding roller 42: Rewinding motor 50: Controller 51: CPU 52: RAM 53: ROM 54: HDD 55: I / F 56: Common Bus 57: Control Panel [Prior art documents] [Patent Documents]

[0110] [Patent Document 1] Japanese Patent Publication No. 2018-150107

Claims

1. A support section that supports a roll formed by winding a long sheet onto a spool, Rotating means for rotating the spool supported by the support portion in the unwinding direction for unwinding the sheet from the spool and in the winding direction for winding the sheet onto the spool, A guide member having a facing portion that faces the outer circumferential surface of the roll, and a guide portion that extends from the facing portion toward the direction of the sheet being fed out, The end portion of the guide member, with the downstream end in the dispensing direction as the pivot point, supports the guide member so that it can rotate in a direction that moves the opposing portion closer to or further away from the outer circumferential surface, A biasing member that biases the rotation of the guide member in a direction that brings the opposing portion closer to the roll, A sensor that protrudes from the opposing portion toward the roll and is biased in a direction to contact the outer circumferential surface of the roll, and outputs a detection signal with a signal level corresponding to the amount of protrusion, A roller supported by the aforementioned opposing portion and in contact with the outer circumferential surface of the roll at a position different from the sensor in the circumferential direction of the roll, The system includes a controller that controls the rotation means based on the signal change rate, which is the amount of change per unit time in the signal level of the detection signal, The aforementioned controller, A sheet supply device characterized in that the rotating means rotates the spool in the winding direction, and when the rate of change of the signal based on the change in the relative positional relationship between the outer surface and the sensor when the leading edge of the sheet does not pass the position of the sensor, the operation of the rotating means is stopped when the rate of change of the signal based on the change in the relative positional relationship between the outer surface and the sensor does not exceed a first rate of change which is the rate of change of the signal due to immersion, which is the displacement of the sensor in the direction away from the rotation axis of the roll, or a second rate of change which is the rate of change of the signal due to protrusion, which is the displacement of the sensor in the direction approaching the rotation axis of the roll, and does not exceed a predetermined inverse set threshold set between the first rate of change and the fluctuation range of the detection signal of the sensor.

2. The aforementioned controller, When the spool is rotated in the winding direction by the rotating means, and the signal change rate exceeds the reverse set threshold and the first change rate exceeds a predetermined threshold, the timing at which the leading edge of the sheet passes the position of the sensor is determined based on the first change rate and the second change rate. From the aforementioned passing timing, the spool is rotated by the rotating means by a predetermined rotation angle to position the leading edge of the sheet at the supply start position upstream of the sensor and the roller in the winding direction and facing the guide portion. The sheet supply device according to claim 1, wherein the spool is rotated in the dispensing direction by the rotating means to supply a sheet along the guide from the supply start position.

3. The aforementioned controller, The sheet supply device according to claim 2, wherein the operation of the rotating means is stopped when the rate of change of the signal exceeds the inverse set threshold and the first rate of change does not exceed a predetermined threshold.

4. The sheet supply device according to any one of claims 1 to 3, further comprising an input unit for receiving an operation to input the value of the inverse set threshold.

5. The sheet supply device according to any one of claims 1 to 4, further comprising a notification unit that outputs warning information when the controller stops the operation of the rotating means based on the determination of the signal change rate.

6. A sheet supply device according to any one of claims 1 to 5, An image forming apparatus comprising an image forming unit that forms an image on a sheet supplied by the sheet supply device.

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