Sheet feeding device and image forming apparatus

Abstract

To provide a sheet supply device which stably detects a tip position regardless of the type of sheets.SOLUTION: A sheet supply device causes rotation means to rotate a spool in a take-up direction (S901), determines a passage timing at which a tip of a sheet passes through a position of a sensor on the basis of a first change rate being a signal change rate when a sensor is immersed and a second change rate being a signal change rate when the sensor protrudes (S902), causes the rotation means to rotate the spool in the take-up direction by a predetermined rotation angle from the passage timing and positions a tip of a sheet at a supply start position on the upstream side in the take-up direction with respect to the sensor and a roller and facing a guide part (S904), and causes the rotation means to rotate the spool in a delivery direction to supply the sheet along the guide part from the supply start position (S905).SELECTED DRAWING: Figure 9

Description

[Technical field]

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

[0002] Conventionally, image forming devices that form images on a long sheet (hereinafter, referred to as a "continuous sheet") wound on a spool have been known. In image forming devices that use continuous sheets, a paper feed mechanism is already known in which a user manually inserts the leading edge of the continuous sheet into a paper feed section, and the device detects the leading edge and then performs a paper feed operation.

[0003] In conventional paper feeding, it was time-consuming to manually insert the leading edge of the continuous sheet, and depending on how it was inserted, it could be inserted at an angle, causing skew and leading to a service call. To solve this problem, there is a technology that rotates the spool in the reverse direction to wind up the continuous sheet, detects the leading edge of the peeled continuous sheet with a sensor, and then rotates the spool forward in the direction to unwind the continuous sheet whose leading edge has been detected (for example, see Patent Document 1). Summary of the Invention [Problem to be solved by the invention]

[0004] However, the peeling state of the leading edge when the spool is rotated in reverse varies depending on the thickness, stiffness, and curl of the continuous sheet. Therefore, in the method of Patent Document 1, the output of the sensor becomes unstable, and the leading edge may not be detected properly.

[0005] The present invention has been made to solve such problems, and aims to provide a technology for stably detecting the leading edge position of a sheet in a sheet feeding device that supplies a long sheet wound around a spool, regardless of the type of sheet. [Means for solving the problem]

[0006] In order to solve the above technical problem, one aspect of the present invention includes a support portion that detachably supports a roll on which a long sheet is wound around a spool; a rotating means that rotates the spool supported by the support portion in a pay-out direction in which the sheet is paid out and in a take-up direction in which the sheet is taken up; a guide member having a facing portion that faces an outer circumferential surface of the roll and a guide portion that extends from the facing portion toward a downstream side in a sheet supply direction; a support shaft that rotatably supports the guide member about a downstream end of the guide member in the sheet supply direction as a rotation center in a direction that moves the facing portion toward and away from the roll; a biasing member that biases the guide member in a direction that moves the facing portion toward the roll; a sensor that protrudes from the facing portion toward the roll and is biased in a direction to abut against the outer circumferential surface of the roll, and outputs a detection signal with a signal level corresponding to the amount of protrusion; and a controller that controls the rotation means based on a signal change rate that is a change per unit time in the signal level of the detection signal, wherein the controller rotates the spool in the winding direction using the rotation means, determines a passing timing at which the leading edge of the sheet passes the position of the sensor based on a first change rate that is the signal change rate when the sensor is retracted and a second change rate that is the signal change rate when the sensor is protruding, rotates the spool in the winding direction by a predetermined rotation angle from the passing timing to position the leading edge of the sheet at a supply start position that is upstream of the sensor and the roller in the winding direction and faces the guide section, and rotates the spool in the unwinding direction using the rotation means to supply the sheet along the guide section from the supply start position. Effect of the Invention

[0007] According to the present invention, in a sheet supplying device that supplies a long sheet wound around a spool, the leading edge position can be stably detected regardless of the type of the sheet. [Brief description of the drawings]

[0008] [Figure 1] 1 is an external perspective view of an image forming apparatus according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a cross-sectional view showing the internal structure of the image forming apparatus. [Diagram 3] FIG. 2 is a schematic diagram of a sheet supplying device. [Figure 4] FIG. [Diagram 5] An enlarged view of the area surrounding the facing area. [Figure 6] 6 is a diagram showing the positional relationship between the leading end of the continuous sheet, the leading end detection sensor, and the rollers. FIG. [Figure 7] 6 is a diagram showing a transition of the signal level of a detection signal from a leading end detection sensor. FIG. [Figure 8] FIG. 2 is a diagram showing the hardware configuration of the image forming apparatus. [Figure 9] 13 is a flowchart of a sheet setting process. [Figure 10] 13 is a flowchart of a leading edge detection process. [Figure 11] 13 is a flowchart of an alternative detection process. [Figure 12] 6A and 6B are diagrams showing transitions in the signal level of a detection signal in leading edge detection processing. [Figure 13] FIG. 13 is a diagram showing an arrangement of a leading end detection sensor according to a modified example. [Figure 14] 13 is a flowchart of a skew control process. [Figure 15] 1A and 1B are diagrams illustrating a conventional method for setting roll paper. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

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

[0010] 1, the outer shape of the housing of the image forming apparatus 1 is formed by a central cover 2, a right cover 3 and a left cover 4 located on the left and right sides of the central cover 2, side plates 5 located at the ends of the right cover 3 and the left cover 4, and an operation cover 6 that opens and closes with respect to the central cover 2. The device main body covered by the covers 2 to 6 is supported by left and right legs 7 with casters.

[0011] The image forming apparatus 1 according to this embodiment is an inkjet type image forming apparatus that forms an image on a continuous sheet P (long sheet) by ejecting ink onto the continuous sheet P. However, the image forming method of the image forming apparatus 1 is not limited to the inkjet method, and may be an electrophotographic method or the like. As shown in FIG. 2, the image forming apparatus 1 mainly includes a sheet supplying device 10, a conveying section 20, an image forming section 30, a winding section 40, and a controller 50 (see FIG. 8).

[0012] The sheet supplying device 10 supplies the continuous sheet P wound around a spool 8 to the conveying section 20 through a conveying path L. The conveying path L is a space inside the image forming apparatus 1 through which the continuous sheet P passes. More specifically, the conveying path L is a path from the sheet supplying device 10 through the conveying section 20 and the image forming section 30 to the winding section 40. Details of the sheet supplying device 10 will be described later with reference to FIGS. 3 to 7.

[0013] The conveying section 20 conveys the continuous sheet P supplied from the sheet supply device 10 through the conveying path L to the winding section 40 through a position facing the image forming section 30. The conveying section 20 mainly includes a conveying roller 21, a pressure roller 22, and a conveying motor 23. The conveying roller 21 and the pressure roller 22 rotate while sandwiching the continuous sheet P from both sides in the thickness direction. The conveying roller 21 rotates by transmitting the driving force of the conveying motor 23. The pressure roller 22 is pressed against the conveying roller 21 with a predetermined pressure, and is driven by the rotation of the conveying roller 21.

[0014] The image forming unit 30 is disposed downstream of the conveying unit 20 in the conveying 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 conveyed by the conveying unit 20. The image forming unit 30 mainly includes a carriage 31, a main scanning motor 32, and a platen 33.

[0015] The carriage 31 reciprocates in a main scanning direction perpendicular to the conveying direction of the continuous sheet P by transmitting the driving force of the main scanning motor 32. The carriage 31 is also equipped with recording heads 31k, 31c, 31m, and 31y that eject ink of each color (black, cyan, magenta, and yellow). The recording heads 31k, 31c, 31m, and 31y eject ink of each color toward the continuous sheet P supported by the platen 33 according to instructions from the controller 50. The platen 33 is disposed facing the carriage 31 in the vertical direction. The platen 33 supports the continuous sheet P conveyed by the conveying unit 20.

[0016] The winding section 40 is disposed downstream of the conveying section 20 and the image forming section 30 in the conveying direction of the continuous sheet P. The winding section 40 winds up the continuous sheet P on which an image has been formed by the image forming section 30. The winding section 40 mainly includes a winding roller 41 and a winding motor 42. The winding roller 41 rotates in a direction to wind up the continuous sheet P on which the image has been formed by transmitting the driving force of the winding motor 42.

[0017] Here, a conventional method for setting roll paper will be described. Figure 15 is a diagram for explaining a conventional method for setting roll paper. The roll paper has flanges (flange members) at the widthwise ends, and a spool is set on the roll paper. The user sets the roll paper with the spool set on the paper feed section receiver (spool bearing stand) of the device (Figure 15(A)), finds the leading edge of the roll paper, and while maintaining the leading edge, holds it down with both hands as shown in Figure 15(B), and rotates the roll paper so that the leading edge of the paper comes to the front. Next, the user positions the leading edge of the paper between the guide plates at the back of the roll paper and inserts it while rotating it (Figure 15(C)). When the user inserts the paper into the back of the guide, the paper is fixed inside and pulled into the inside of the device.

[0018] As shown in Figure 15(C), the guide plate where the leading edge of the paper is inserted is located at the back of the roll paper, so it is hidden by the roll paper and difficult to see, making it difficult to check whether the paper has been inserted properly. In addition, the leading edge of the roll paper needs to be inserted as evenly as possible, which requires careful attention. Furthermore, if the leading edge of the paper is not inserted evenly, it will be fed at an angle, causing skew, which may require retrying the operation or causing a jam.

[0019] Furthermore, as shown in Figures 15(D) and (E), in devices with a two-tiered roll paper setting section, when a roll paper is set in the upper tier and a roll paper is set in the lower tier and the leading edge is inserted between the guide plates, the guide plates are already visible because the roll paper in the upper tier is already there, making setting even more difficult and increasing the risk of inserting it at an angle.

[0020] Fig. 3 is a schematic configuration diagram of the sheet supplying device 10. Fig. 4 is a perspective view of the guide arm 13. As shown in Figs. 2 to 4, the sheet supplying device 10 mainly includes a support portion 11, a supply motor 12 (rotating means), a guide arm 13 (guide member), a spindle 14, a coil spring 15 (urging member), a leading edge detection sensor 16, a plurality of rollers 17a, 17b, a cutter 18, and guide plates 19a, 19b.

[0021] The support section 11 detachably supports the roll 9. The roll 9 is formed by winding the continuous sheet P around an axial spool 8. More specifically, the support section 11 rotatably supports both ends of the spool 8. The supply motor 12 is capable of rotating the spool 8 supported by the support section 11 in a forward direction to pay out the continuous sheet P (counterclockwise in FIG. 3) and in a reverse direction to wind up the continuous sheet P (clockwise in FIG. 3).

[0022] The guide arm 13 serves to bring the leading end detection sensor 16 and the rollers 17a, 17b into contact with the roll 9, and also to guide the continuous sheet P unwound from the roll 9 between the guide plates 19a, 19b. The guide arm 13 has an outer shape of a long plate. The guide arm 13 has a facing portion 13a and a guide portion 13b.

[0023] The facing portion 13a has an arc-shaped outer shape that follows the outer peripheral surface of the roll 9. The facing portion 13a faces the outer peripheral surface of the roll 9 below a horizontal line passing through the rotation center of the spool 8. More specifically, the facing portion 13a faces an area (lower area) including the lower end of the roll 9. The guide portion 13b extends from the facing portion 13a toward the downstream side in the supply direction of the continuous sheet P. More specifically, the guide portion 13b extends from the facing portion 13a to a position between the guide plates 19a, 19b.

[0024] The spindle 14 extends in the same direction as the spool 8 supported by the support portion 11. The spindle 14 is fixed inside the covers 2 to 6. The spindle 14 is attached to the downstream end of the guide portion 13b in the supply direction of the continuous sheet P, and rotatably supports the guide arm 13. That is, the guide arm 13 is configured to be rotatable about the spindle 14 in a direction that moves the facing portion 13a toward and away from the roll 9. The coil spring 15 biases the guide arm 13 in a direction that moves the facing portion 13a closer to the roll 9.

[0025] The leading edge detection sensor 16 protrudes from the facing portion 13a toward the roll 9. The leading edge detection sensor 16 is supported in a manner that allows it to protrude into and out of the facing portion 13a. The leading edge detection sensor 16 is biased in a direction in which it abuts against the outer circumferential surface of the roll 9 (i.e., protrudes from the facing portion 13a). The leading edge detection sensor 16 outputs a detection signal having a signal level according to the amount of protrusion from the facing portion 13a to the controller 50. More specifically, the signal level of the detection signal increases as the amount of protrusion increases, and decreases as the amount of protrusion decreases.

[0026] The rollers 17a, 17b are rotatably supported by the facing portion 13a. The rotation axes of the rollers 17a, 17b extend in the same direction as the extension direction of the spool 8 and the support shaft 14. The rollers 17a, 17b are disposed in a position different from the leading edge detection sensor 16 in the circumferential direction of the roll 9. More specifically, the rollers 17a, 17b are disposed upstream of the leading edge detection sensor 16 in the winding direction. Furthermore, the rollers 17a, 17b are disposed spaced apart in the width direction perpendicular to the circumferential direction of the roll 9. More specifically, the leading edge detection sensor 16 is disposed between the rollers 17a, 17b in the width direction.

[0027] The cutter 18 cuts the leading edge of the continuous sheet P across the entire width. The cutting line cut by the cutter 18 extends in a direction perpendicular to the feed direction of the continuous sheet P. In other words, when the leading edge of the continuous sheet P is inclined (skewed) with respect to the feed direction, the leading edge of the continuous sheet P can be cut by the cutter 18 so that the leading edge of the continuous sheet P is perpendicular to the feed direction.

[0028] The guide plates 19a and 19b are disposed downstream of the guide arm 13 in the supply direction of the continuous sheet P. The guide plates 19a and 19b are disposed opposite each other across the conveying path L. The continuous sheet P traveling along the guide arm 13 passes between the guide plates 19a and 19b and is supplied to the conveying section 20. In other words, the guide plates 19a and 19b serve as a paper feeding section into which the continuous sheet P unwound from the roll 9 enters.

[0029] Next, the relationship between the position of the leading edge of the continuous sheet P and the signal level of the detection signal when the spool 8 is rotated in the winding direction will be described with reference to Figs. 5 to 7. Fig. 5 is an enlarged view of the periphery of the facing portion 13a. Fig. 6 is a diagram showing the positional relationship between the leading edge of the continuous sheet P and the leading edge detection sensor 16 and roller 17a. Fig. 7 is a diagram showing the transition of the signal level of the detection signal of the leading edge detection sensor 16.

[0030] 5, the coil spring 15 biases the guide arm 13 in a direction approaching the roll 9, so that the leading edge detection sensor 16 and rollers 17a, 17b abut against the outer circumferential surface of the roll 9. When the spool 8 is rotated in the winding direction, the leading edge of the continuous sheet P in close contact with the outer circumferential surface of the roll 9 passes the leading edge detection sensor 16 after passing the rollers 17a, 17b.

[0031] 6(A) and (B), when the leading edge of the continuous sheet P passes through the rollers 17a and 17b, the guide arm 13 rotates by the thickness of the continuous sheet P, and the rollers 17a and 17b come into contact with the outer circumferential surface of the roll 9. As a result, the leading edge detection sensor 16 sinks into the facing portion 13a by the thickness of the continuous sheet P. In other words, the leading edge of the continuous sheet P passes through the rollers 17a and 17b, and the amount of protrusion of the leading edge detection sensor 16 decreases.

[0032] 7A, the detection signal of the leading edge detection sensor 16 is a High signal before the leading edge of the continuous sheet P passes the rollers 17a and 17b (region α), and becomes a Low signal after the leading edge of the continuous sheet P passes the rollers 17a and 17b (region β). Note that the High signal has a higher signal level than the Low signal. In other words, the signal level of the detection signal of the leading edge detection sensor 16 decreases as the leading edge of the continuous sheet P passes the rollers 17a and 17b.

[0033] 6(B) and (C), when the leading edge of the continuous sheet P passes the leading edge detection sensor 16, the leading edge detection sensor 16 protrudes from the facing portion 13a by the thickness of the continuous sheet P. In other words, as the leading edge of the continuous sheet P passes the leading edge detection sensor 16, the protruding amount of the leading edge detection sensor 16 increases.

[0034] 7A, after the leading edge of the continuous sheet P passes the leading edge detection sensor 16 (region γ), the detection signal of the leading edge detection sensor 16 becomes a High signal. That is, the signal level of the detection signal of the leading edge detection sensor 16 increases as the leading edge of the continuous sheet P passes the leading edge detection sensor 16.

[0035] 7B, when observing the change in the signal level of the detection signal microscopically, in the process in which the leading edge of the continuous sheet P passes through the rollers 17a and 17b, the detection signal of the leading edge detection sensor 16 drops by a signal level y1 during the time x1. Also, in the process in which the leading edge of the continuous sheet P passes through the leading edge detection sensor 16, the detection signal of the leading edge detection sensor 16 rises by a signal level y2 during the time x2.

[0036] Hereinafter, the amount of change per unit time in the signal level of the detection signal will be referred to as the "signal change rate." The signal change rate when the leading end detection sensor 16 is submerged will be referred to as the first change rate, and the signal change rate when the leading end detection sensor 16 is protruding will be referred to as the second change rate. That is, the first change rate and the second change rate have opposite directions of change in the signal level.

[0037] A first rate of change K1=|y1 / x1| when the leading edge of the continuous sheet P passes through rollers 17a and 17b exceeds a predetermined first threshold. A second rate of change K2=|y2 / x2| when the leading edge of the continuous sheet P passes through leading edge detection sensor 16 exceeds a predetermined second threshold. The first and second thresholds are thresholds for absorbing minute variations in diameter of the roll 9. The first and second thresholds may be the same value or different values.

[0038] Fig. 8 is a hardware configuration diagram of the image forming apparatus 1. As shown in Fig. 8, the image forming apparatus 1 includes a CPU (Central Processing Unit) 51 as a control means, a RAM (Random Access Memory) 52 as a storage means, a ROM (Read Only Memory) 53 as a storage means, a HDD (Hard Disk Drive) 54 as a storage means, and an I / F 55 as an interface, all of which are connected via a common bus 56 as a communication means. The CPU 51, the RAM 52, the ROM 53, and the HDD 54 are examples of a controller 50.

[0039] The CPU 51 is a calculation means and controls the overall operation of the image forming apparatus 1. The RAM 52 is a volatile storage medium capable of reading and writing information at high speed, and is used as a working area when the CPU 51 processes information. The ROM 53 is a read-only non-volatile storage medium in which programs such as firmware are stored. The HDD 54 is a non-volatile storage medium capable of reading and writing information and has a large storage capacity, and stores an OS (Operating System), various control programs, application programs, etc.

[0040] The image forming apparatus 1 processes various programs loaded from the ROM 53 or HDD 54 to the RAM 52 using a calculation function provided in the CPU 51. This processing constitutes a software control unit including various functional modules of the image forming apparatus 1. The combination of the software control unit thus constituted and the hardware resources mounted on the image forming apparatus 1 constitutes a functional block that realizes the functions of the image forming apparatus 1.

[0041] The I / F 55 is an interface that connects the sheet supply device 10, the conveying unit 20, the image forming unit 30, the winding unit 40, and the operation panel (input unit) 57 to the common bus 56. That is, the controller 50 controls the sheet supply device 10, the conveying unit 20, the image forming unit 30, the winding unit 40, and the operation panel 57 through the I / F 55.

[0042] The operation panel 57 is a user interface that includes a display that displays various information to be notified to the operator, and buttons, switches, dials, etc. that accept operations by the operator. The operation panel 57 may also include a touch panel superimposed on the display. Upon accepting an operation by the operator, the operation panel 57 outputs an operation signal corresponding to the accepted operation to the controller 50.

[0043] Next, the sheet setting process will be described with reference to Fig. 9. Fig. 9 is a flowchart of the sheet setting process. The sheet setting process is a process in which, when a new roll 9 is attached to the support section 11, the continuous sheet P of the roll 9 is supplied to the conveying section 20 through between the guide plates 19a, 19b. The controller 50 controls the supply motor 12 based on the signal change rate of the leading edge detection sensor 16. The sheet setting process is started, for example, when the sensor detects that the roll 9 has been attached, or when an operation indicating that the roll 9 has been replaced is received through the operation panel 57.

[0044] First, the controller 50 rotates the spool 8 in the winding direction by rotating the supply motor 12 in the reverse direction (S901). The controller 50 also executes a leading edge detection process (to be described later) while rotating the supply motor 12 in the reverse direction (S902). Then, the controller 50 determines whether or not the leading edge of the continuous sheet P has been successfully detected in the leading edge detection process (S903).

[0045] When the controller 50 determines that the leading edge of the continuous sheet P has been successfully detected (S903: Yes), it rotates the supply motor 12 in the reverse direction to rotate the spool 8 in the winding direction by a predetermined rotation angle (for example, about 355°) from the passing timing determined in the leading edge detection process (S904). As a result, the leading edge of the continuous sheet P reaches the supply start position.

[0046] The passing timing refers to the timing when the leading edge of the continuous sheet P passes the leading edge detection sensor 16. The supply start position is a position upstream of the leading edge detection sensor 16 and the rollers 17a, 17b in the winding direction and facing the guide section 13b. In other words, the supply start position is a position where the continuous sheet P is supplied along the guide section 13b in the direction of the guide plates 19a, 19b by rotating the spool 8 in the unwinding direction.

[0047] Next, the controller 50 rotates the supply motor 12 in the forward direction to supply the continuous sheet P from the supply start position along the guide portion 13b (S905). As a result, the continuous sheet P passes between the guide plates 19a and 19b and is sandwiched between the conveying roller 21 and the pressure roller 22.

[0048] After the sheet setting process is normally completed, the image forming apparatus 1 can execute the image forming process to form an image on the continuous sheet P. That is, the controller 50 drives the conveying motor 23 to convey the continuous sheet P to a position facing the recording heads 31k, 31c, 31m, and 31y. Next, the controller 50 drives the main scanning motor 32 to move the carriage 31 in the main scanning direction and causes the recording heads 31k, 31c, 31m, and 31y to eject ink. By repeating this process, an image is recorded on the continuous sheet P. Furthermore, the controller 50 drives the winding motor 42 to wind the continuous sheet P on which the image has been recorded onto the winding roller 41.

[0049] On the other hand, when the controller 50 determines that it has failed to detect the leading edge of the continuous sheet P (S903: No), it stops the supply motor 12 and displays an error on the operation panel 57 (S906). This allows the operator to perform an appropriate operation (e.g., re-attaching the roll 9, etc.) according to the content of the error displayed on the operation panel 57.

[0050] Next, the process of detecting the leading edge of the continuous sheet P in step S902 in Fig. 9 will be described with reference to Figs. 10 to 12. Fig. 10 is a flowchart of the leading edge detection process. Fig. 11 is a flowchart of the alternative detection process. Fig. 12 is a diagram showing the transition of the signal level of the detection signal in the leading edge detection process. Note that while the leading edge detection process and the alternative detection process are being executed, the spool 8 rotates in the winding direction.

[0051] The leading edge detection process shown in Fig. 10 is a process for determining the passing timing based on both the first change rate K1 and the second change rate K2. On the other hand, the alternative detection process shown in Fig. 11 is a process for determining the passing timing based only on the second change rate K2. In this embodiment, the passing timing is first determined by the leading edge detection process, and the alternative detection process is executed if the passing timing cannot be determined by the leading edge detection process. However, the leading edge detection process and the alternative detection process may be executed independently.

[0052] First, the controller 50 initializes (=1) variables R and N stored in the RAM 52 (S1001). The variable R indicates the number of times the spool 8 has been rotated in the leading edge detection process. The variable N indicates the number of times the passing timing has been determined in the leading edge detection process.

[0053] Next, the controller 50 waits until the first change rate K1 of the detection signal exceeds the first threshold value (S1002) or until the second time t2 has elapsed (S1003) before executing the subsequent processes. Then, the controller 50 determines that the leading edge of the continuous sheet P has passed the rollers 17a and 17b if the first change rate K1 exceeds the first threshold value within a third time range t3 determined in advance (S1002: Yes) before the second time t2 has elapsed (S1003: No).

[0054] Next, when the controller 50 determines that the leading edge of the continuous sheet P has passed the rollers 17a and 17b (S1002: Yes), it waits to execute the following process until the second change rate K2 of the detection signal exceeds the second threshold value (S1004) or the first time t1 has elapsed (S1005). Then, when the second change rate K2 exceeds the second threshold value (S1004: Yes) before the first time t1 has elapsed (S1005: No), the controller 50 determines that the leading edge of the continuous sheet P has passed the leading edge detection sensor 16.

[0055] As shown in FIG. 12, the first time t1 is a predetermined time corresponding to the distance between the rollers 17a, 17b and the leading edge detection sensor 16. More specifically, the first time t1 is a time required for the roll 9 to rotate by the distance plus a margin. The second time t2 is a time required for the roll 9 to rotate once plus a plus 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 a time range that goes back a predetermined time from the timing at which the second time t2 elapses (the end of the second time t2). More specifically, the third time range t3 is a range of time that includes a plus or minus margin from the timing at which the leading edge of the continuous sheet P is assumed to pass the leading edge detection sensor 16 within the second time t2.

[0056] The controller 50 determines, as the passing timing, the timing at which the second rate of change K2 exceeds the second threshold (S1004: Yes) after the first rate of change K1 exceeds the first threshold (S1002: Yes) and before the first time t1 has elapsed (S1005: No). When determining the passing timing, the controller 50 calculates the variable N and the determination threshold X th and compare (S1006).

[0057] Next, the controller 50 calculates whether the variable N is equal to or smaller than the decision threshold X th If it is less than the threshold value X (S1006: No), the variable N is incremented by 1 (S1007) and the process from step S1002 onward is executed again. Then, the controller 50 checks whether the variable N is greater than the threshold value X thIf it is determined that the detection of the leading edge of the continuous sheet P has been successful (S1006: Yes), the leading edge detection process ends.

[0058] That is, the controller 50 determines whether the second time t2 is X th During the time that elapses (S1006: No), th When the passing timing is determined to be within the third time range t3 included in each of the second times (S1004: Yes), th The process of step S904 is executed at the timing of the th pass. th is a value for determining whether the number of times the leading edge of the continuous sheet P is detected exceeds a predetermined number. th may be a predetermined fixed value, or may be an input of the value of N through the operation panel 57. th It may be 1 or 2 or more.

[0059] On the other hand, if the second time t2 has elapsed before the first change rate K1 exceeds the first threshold (S1002: No & S1003: Yes), or if the first change rate K1 exceeds the first threshold outside the third time range t3, the controller 50 th Similarly, before the second rate of change K2 exceeds the second threshold (S1004: No), if the first time t1 has elapsed (S1005: Yes), the controller 50 compares the variable R with the rotation threshold R th and compare (S1008).

[0060] The controller 50 then calculates the rotation threshold R th If the rotation speed is less than the rotation threshold R (S1008: No), the variable R is incremented by 1 (S1009), and the process from step S1002 onward is executed again. Next, the controller 50 checks whether the variable R is equal to or smaller than the rotation threshold R th If it has reached this number (S1008: Yes), it is determined that the leading edge detection process has failed to detect the leading edge of the continuous sheet P, and an alternative detection process is executed (S1010).

[0061] That is, the controller 50 rotates the roll 9 in the winding direction R th If the first change rate and the second change rate cannot be detected before the rotation (S1008: No) (S1002: No & S1004: No), an alternative detection process is executed (S1010). th is a value for determining whether the number of times that the leading edge detection of the continuous sheet P has failed exceeds a predetermined number of times from the start of the leading edge detection process (S1001) to the alternative detection process (S1010). th may be a predetermined fixed value, or may be an input of the value of R via the operation panel 57. th It may be 1 or 2 or more.

[0062] 11, the controller 50 initializes (=1) the variables R and N stored in the RAM 52 (S1101). th , and the rotation threshold R th The definition of is the same as in the leading edge detection process.

[0063] Next, the controller 50 waits to execute the subsequent process until the second change rate K2 of the detection signal exceeds the second threshold value (S1102) or until the second time t2 has elapsed (S1103). Then, if the second change rate K2 exceeds the second threshold value within a third time range t3 determined in advance (S1102: Yes) before the second time t2 has elapsed (S1103: No), the controller 50 determines that the leading edge of the continuous sheet P has passed the leading edge detection sensor 16 (i.e., the passing timing).

[0064] Next, when the controller 50 determines that the passing timing has occurred (S1102: Yes), the controller 50 calculates the variable N and the determination threshold value X th Next, the controller 50 compares the variable N with the determination threshold value X th If it is less than the threshold value X (S1104: No), the variable N is incremented by 1 (S1105) and the process from step S1102 onward is executed again. Then, the controller 50 checks whether the variable N is greater than the threshold value X thIf the second time t2 reaches X (S1104: Yes), it is determined that the detection of the leading edge of the continuous sheet P has been successful and the alternative detection process is terminated. th During the time that elapses (S1104: No), th When the second rate of change exceeds the second threshold within a third time range t3 included in each of the second times t2, X th The timing at which the second rate of change exceeds the second threshold value for the first time is determined as the passing timing.

[0065] On the other hand, if the second time t2 has elapsed before the second change rate K2 exceeds the second threshold (S1102: No & S1103: Yes), or if the second change rate K2 exceeds the second threshold outside the third time range t3, the controller 50 th Next, the controller 50 compares the variable R with the rotation threshold value R th If the variable R is less than the rotation threshold R (S1106: No), the controller 50 increments the variable R by 1 (S1007) and executes the processes from step S1102 onward again. th If it is determined that the detection of the leading edge of the continuous sheet P by the alternative detection process has failed (S1106: Yes), the alternative detection process is terminated.

[0066] According to the above embodiment, for example, the following advantageous effects are achieved.

[0067] According to the above embodiment, the leading edge of the continuous sheet P is detected while it is in close contact with the outer peripheral surface of the roll 9, so that the leading edge of the continuous sheet P can be stably detected regardless of the thickness, stiffness, curl state, etc. of the continuous sheet P. Furthermore, by simply mounting the roll 9 on the support portion 11, the leading edge is automatically detected and inserted between the guide plates 19a, 19b, so that the continuous sheet P can be stably inserted between the guide plates 19a, 19b compared to the case where the continuous sheet P is manually inserted by an operator.

[0068] According to the above embodiment, the timing at which the second change rate K2 exceeds the second threshold before the first time t1 has elapsed since the first change rate K1 exceeded the first threshold is determined as the passing timing, which makes it possible to prevent the unevenness of the roll 9 from being erroneously detected as the leading edge of the continuous sheet P.

[0069] According to the above embodiment, the leading edge of the continuous sheet P is th Since the detection is repeated times, the detection accuracy is improved. th By having the operator set the threshold value X th When the continuous sheet P is thick, the judgment threshold value X th As a result, it is possible to achieve both high detection accuracy and high throughput.

[0070] In addition, when the leading edge of the continuous sheet P is inclined with respect to the feeding direction, the first change rate K1 when the leading edge of the continuous sheet P passes through the rollers 17a and 17b tends to be small. Therefore, as in the above embodiment, when the leading edge of the continuous sheet P cannot be properly detected by the leading edge detection process, the alternative detection process is executed, so that the leading edge of the continuous sheet P can be properly detected regardless of the degree of inclination of the continuous sheet P.

[0071] [Variations] The skew control process according to the modified example will be described with reference to Fig. 13 and Fig. 14. Fig. 13 is a diagram showing the arrangement of leading edge detection sensors 16a, 16b according to the modified example. Fig. 14 is a flowchart of the skew control process. Note that a detailed description of the commonalities with the above embodiment will be omitted, and the description will focus on the differences.

[0072] The facing section 13a according to the modified example differs from the above embodiment in that it has a plurality of leading edge detection sensors 16a, 16b. The leading edge detection sensors 16a, 16b are arranged to face the outer peripheral surface of the roll 9 at positions spaced apart in the width direction of the continuous sheet P. The controller 50 according to the modified example determines the passing timing using the leading edge detection sensors 16a, 16b in the leading edge detection process and the alternative detection process. The controller 50 also executes the skew control process shown in FIG. 14 instead of the process after step S904 in FIG. 9.

[0073] As shown in Fig. 13, when the leading edge of the continuous sheet P is inclined with respect to the feeding direction, a time difference ΔT occurs between the passing timings determined by the leading edge detection sensors 16a and 16b. Therefore, as shown in Fig. 14, when the leading edge of the continuous sheet P is successfully detected (S903: Yes), the controller 50 calculates the time difference ΔT (S1401). Next, the controller 50 compares the calculated time difference ΔT with the threshold time T th1 , T th2 (S1402, S1403). th1 <T th2 It is.

[0074] Then, the controller 50 determines whether the time difference ΔT is a threshold time T th1 If the time difference Δ is less than the threshold time T th1 Above threshold time T th2 If the time difference Δ is less than the threshold time T th2 In the above cases (S1402: No & S1403: No), the processes of steps S904 and S905 are not executed, and an error is displayed on operation panel 57 (S1405).

[0075] As in the above modification, by arranging the leading edge detection sensors 16a, 16b spaced apart in the width direction of the continuous sheet P, the degree of inclination of the leading edge of the continuous sheet P can be determined based on the time difference ΔT between the passing timings. According to the above modification, if the time difference ΔT is relatively large (the skew is not so large), the leading edge is cut off by the cutter 18, and if the time difference ΔT is very large (the skew is large), the supply of the continuous sheet P is stopped and an error is displayed. This makes it possible to execute one of several machine operations depending on the degree of skew.

[0076] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the technical gist of the present invention. The present invention covers all technical matters included in the technical ideas described in the claims. The above-described embodiment shows a preferred example, but a person skilled in the art can realize various modifications from the disclosed contents. Such modifications are also included in the technical scope described in the claims. [Explanation of symbols]

[0077] 1: Image forming device 2: Center cover 3: Right cover 4: Left cover 5: Side plate 6: Operation cover 7: Caster legs 8: Spool 9: Roll 10: Sheet feeder 11: Support part 12: Supply motor 13: Guide arm 13a: Facing part 13b: Information department 14: Support shaft 15: Coil spring 16, 16a, 16b: Tip detection sensor 17a, 17b: Coro 18: Cutter 19a, 19b: Guide plate 20: Transport section 21: Transport roller 22: Pressure roller 23: Transport motor 30: Image forming section 31: Carriage 31c, 31k, 31m, 31y: Recording head 32: Main scanning motor 33: Platen 40: Winding section 41: Winding roller 42: Winding motor 50: Controller 51: CPU 52: RAM 53: ROM 54: HDD 55: Interface 56: Common bus 57: Operation panel [Prior art documents] [Patent documents]

[0078] [Patent Document 1] JP 2018-150107 A

Claims

1. A support portion that detachably supports a roll in which a long sheet is wound around a spool; a rotating means for rotating the spool supported by the support portion in a pay-out direction for paying out a sheet and in a take-up direction for taking up the sheet; a guide member having a facing portion facing an outer peripheral surface of the roll and a guide portion extending from the facing portion toward a downstream side in a sheet supply direction; a support shaft that rotatably supports the guide member in a direction in which the facing portion is brought into contact with and separated from the roll, the support shaft being configured to rotate around a downstream end of the guide member in a sheet supply direction as a rotation center; a biasing member that biases the guide member in a direction to bring the facing portion closer to the roll; a sensor that protrudes from the facing portion toward the roll, is biased in a direction to abut against an outer circumferential surface of the roll, and outputs a detection signal with a signal level corresponding to an amount of protrusion; a roller supported by the facing portion and in contact with the outer circumferential surface of the roll at a position different from the position of the sensor in the circumferential direction of the roll; a controller for controlling the rotating means based on a signal change rate which is a change amount per unit time of a signal level of the detection signal, The controller: The spool is rotated in the winding direction by the rotating means; determining a passing timing when the leading edge of the sheet passes the position of the sensor based on a first rate of change, which is the signal change rate when the sensor is retracted, and a second rate of change, which is the signal change rate when the sensor is protruding; the spool is rotated in the winding direction by the rotating means by a predetermined rotation angle from the passing timing, and the leading end of the sheet is positioned at a supply start position upstream of the sensor and the roller in the winding direction and facing the guide section; the rotating means rotates the spool in the payout direction to supply the sheet from the supply start position along the guide portion.

2. The roller is disposed upstream of the sensor in the winding direction, The sheet supplying device according to claim 1, characterized in that the controller determines the passing timing as the timing at which the second rate of change exceeds a second threshold value within a first time period corresponding to the distance between the roller and the sensor after the first rate of change exceeds a first threshold value.

3. The sheet supply device according to claim 2, characterized in that when the controller determines that the passing timing is within a third time range included in each of N second times (N is an integer equal to or greater than 2) that correspond to one rotation of the roll, the controller causes the rotation means to rotate the spool in the winding direction by a predetermined rotation angle from the Nth passing timing.

4. The sheet supplying device according to any one of claims 1 to 3, characterized in that the controller determines the passing timing based only on the second rate of change when the first rate of change cannot be detected until the roll has rotated R (R is an integer greater than or equal to 1) in the winding direction.

5. The sheet supplying device described in claim 4, characterized in that when the second change rate exceeds the second threshold within a third time range included in each of N second times (N is an integer greater than or equal to 2) during which N second times corresponding to one rotation of the roll have elapsed, the controller determines the timing at which the second change rate exceeds the second threshold for the Nth time as the passing timing.

6. 6. The sheet supplying apparatus according to claim 3, further comprising an input unit that accepts an operation to input the value of N.

7. 7. The sheet supplying device according to claim 1, wherein the facing portion is provided with a plurality of the sensors spaced apart in a width direction of the sheet.

8. 8. The sheet supplying apparatus according to claim 7, wherein the controller executes one of a plurality of machine operations depending on a time difference between the passage timings determined by using each of the plurality of sensors.

9. A sheet feeding device according to any one of claims 1 to 8, an image forming unit that forms an image on the sheet fed by the sheet feeding device.

Images