Sheet feeding device and printing device

Abstract

To accurately detect separation of a sheet from a roll and perform automatic paper feeding.SOLUTION: In automatic paper feeding from a roll, a sheet feeding device detects sheet separation using a sensor installed in a position to which a sheet outer face comes close to a sheet separated from an outer periphery of the roll, and of which sensor output varies according to a distance to the sheet outer face. The sheet feeding device feeds a sheet while changing a rotation direction of the roll to a first direction opposite to a second direction when the roll is rotated in the second direction and a prescribed change occurs in the sensor output.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a sheet feeding device that draws out and feeds a continuous sheet from a roll around which the sheet is wound, and to a printing apparatus. [Background technology]

[0002] Patent Document 1 discloses a printing device that can detect the leading edge of a sheet on a loaded roll and automatically feed the sheet. In this device, the roll is rotated in the winding direction opposite to the supply direction, and an optical sensor located near the roll detects when the leading edge of the sheet peels off and separates from the roll due to its own weight. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-37557 Summary of the Invention [Problem to be solved by the invention]

[0004] The optical sensor in Patent Document 1 detects sheet peeling by obtaining an ON output due to reflected light the moment the leading edge of a sheet peeled from the roll passes through the sensor optical axis, which is parallel to the tangent of the roll. The signal strength of the sensor output at this time is nearly zero until the leading edge of the peeled sheet reaches the sensor optical axis. At the moment the leading edge of the sheet passes the sensor optical axis, a pulse-like signal is generated by reflected light from the edge of the leading edge of the sheet. After passing the sensor optical axis, the sensor light hits the inner surface of the peeled sheet. However, because the sensor optical axis and the inner surface of the sheet are nearly parallel and the distance between them rapidly increases, the reflection intensity is weak, and the signal level drops sharply after passing. In other words, the optical sensor in Patent Document 1 can basically only determine the moment the leading edge of the sheet passes the sensor optical axis during the peeling process.

[0005] However, in actual devices, the behavior of the sheet peeling from the roll (the peeling speed (the speed at which the leading edge of the sheet moves)) changes depending on various conditions, such as the stiffness of the sheet being used (the force that causes the bent sheet to return to its original shape) and static electricity. Therefore, in a configuration in which the leading edge of the sheet is detected using a momentary signal pulse during peeling, as in Patent Document 1, the timing at which the signal pulse is generated changes depending on the situation, making it difficult to detect sheet peeling with high accuracy. This timing discrepancy can then interfere with the subsequent sheet delivery operation. Patent Document 1 does not disclose any means to solve this problem.

[0006] SUMMARY OF THE INVENTION An object of the present invention is to provide a sheet feeding device and a printing apparatus that can accurately detect the separation of a sheet from a roll and perform automatic feeding. [Means for solving the problem]

[0007] The sheet feeding device of the present invention includes: a driving means for rotating a roll formed by winding a sheet in a first direction for feeding the sheet from the roll, and a driving means for rotating the roll in a second direction opposite to the first direction; a lower guide that supports the sheet fed from the roll from below; a contact member that is provided above the lower guide, moves in response to a change in the outer diameter of the roll, and comes into contact with the roll at a contact position; a detection means for detecting the leading edge of the sheet when the leading edge of the sheet on the roll rotating in the second direction passes through the contact position and the sheet approaches the detection means; a contact member that is supported by the lower guide on the upstream side of the detection means in the direction in which the sheet is fed from the roll, and that comes into contact with the roll rotating in the second direction at a contact position; a sheet supplying device that changes the rotation of the roll by the driving means from the second direction to the first direction in response to an output from the detection means, The distance between the contact position and the detection position of the detection means in the circumferential direction of the roll is shorter than the distance between the contact position and the abutment position in the circumferential direction. [Effects of the Invention]

[0008] According to the present invention, the peeling of the sheet from the roll can be accurately detected and automatic feeding can be performed. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a perspective view of a printing apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory diagram of a sheet transport path in the printing apparatus. [Figure 3] FIG. 2 is an explanatory diagram of a sheet supplying device. [Figure 4] FIG. 10 is an explanatory diagram of the sheet feeding device when the roll outer diameter is small. [Figure 5] FIG. 2 is a block diagram illustrating a control system of the printing apparatus. [Figure 6] 10 is a flowchart of a sheet supply preparation process. [Figure 7] FIG. 2 is an explanatory diagram of a sensor unit according to the first embodiment of the present invention. [Figure 8] 10 is a flowchart illustrating a sheet leading edge setting process. [Figure 9] FIG. 10 is an explanatory diagram of a change in sensor output of a sensor unit according to a second embodiment of the present invention. [Figure 10] FIG. 4 is an explanatory diagram of a sensor output of a sensor unit. [Figure 11] 10 is a flowchart illustrating a sheet leading edge setting process. [Figure 12] FIG. 10 is a block diagram of a control system of a printing apparatus according to a third embodiment of the present invention. [Figure 13] FIG. 4 is an explanatory diagram of a sensor output of a sensor unit. [Figure 14] 10 is a flowchart illustrating a process for adjusting an amplification factor of a sensor. [Figure 15] FIG. 10 is an explanatory diagram of the deployment position of the sensor unit in the fourth embodiment of the present invention. [Figure 16]FIG. 4 is an explanatory diagram of the relationship between the optical axis of the sensor unit and the outer peripheral surface of the roll. [Figure 17] FIG. 2 is an explanatory diagram of the configuration of a sensor unit. [Figure 18] FIG. 11 is an explanatory diagram of the deployment position of the sensor unit in the fifth embodiment of the present invention. [Figure 19] FIG. 13 is an explanatory diagram of a sensor output of a sensor unit according to the sixth embodiment of the present invention. [Figure 20] 10A and 10B are diagrams illustrating the behavior of the leading edge of a sheet. [Figure 21] 10 is a flowchart illustrating a sheet leading edge setting process. [Figure 22] FIG. 13 is an explanatory diagram of a stop position of the leading edge of a sheet in the seventh embodiment of the present invention. [Figure 23] 10 is a flowchart illustrating a sheet leading edge setting process. [Figure 24] FIG. 10 is an explanatory diagram of another example of the configuration of the sheet supplying device. DETAILED DESCRIPTION OF THE INVENTION

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will now be described with reference to the accompanying drawings. First, a basic configuration of the present invention will be described.

[0011] <Basic configuration> 1 to 5 are explanatory diagrams of the basic configuration of a printing apparatus according to an embodiment of the present invention. The printing apparatus according to this embodiment is an inkjet printing apparatus that includes a sheet supply device for supplying sheets as printing media and a printing unit for printing images on the sheets. For ease of explanation, coordinate axes are set as shown in the drawings. That is, the sheet width direction of the roll R is set as the X-axis direction, the direction in which the sheet is transported in the printing unit 400 (described later) is set as the Y-axis direction, and the direction of gravity is set as the Z-axis direction.

[0012] As shown in Fig. 1, in the printing apparatus 100 of this example, rolls R (roll sheets), which are long continuous sheets (sometimes called webs) wound into a roll, can be set in two roll holders, an upper one and a lower one. An image is printed on a sheet 1 selectively pulled out from the roll R. Using various switches on the operation panel 28, the user can input various commands to the printing apparatus 100, such as specifying the size of the sheet 1 and switching between online and offline.

[0013] FIG. 2 is a schematic cross-sectional view of the main components of the printing apparatus 100. Two supply devices 200 corresponding to two rolls R are arranged one above the other. The sheet 1 drawn from the rolls R by the supply devices 200 is transported by a sheet transport unit (transport mechanism) 300 along a sheet transport path to a printing unit 400 capable of printing an image. The printing unit 400 prints an image on the sheet 1 by ejecting ink from an inkjet print head 18. The print head 18 ejects ink from its ejection openings using ejection energy generating elements such as electrothermal transducers (heaters) or piezoelectric elements. The print head 18 is not limited to an inkjet type, and the printing method of the printing unit 400 is also not limited. For example, a serial scan type or a full line type may be used. In the serial scan type, an image is printed by transporting the sheet 1 and scanning the print head 18 in a direction intersecting the sheet 1 transport direction. In the case of the full-line method, an elongated print head 18 extending in a direction intersecting the conveying direction of the sheet 1 is used, and an image is printed on the sheet 1 while the sheet 1 is continuously conveyed.

[0014] The roll R is set in the roll holding section of the supply device 200 with the spool member 2 inserted in the hollow hole, and the spool member 2 is driven in forward and reverse rotation by a roll drive motor 33 (see FIG. 5). The supply device 200 is equipped with a drive section 3, an arm member (moving body) 4, an arm rotation shaft 5, a sensor unit 6, a swinging member 7, driven rotors (contact bodies) 8 and 9, a separation flapper (upper guide body) 10, and a flapper rotation shaft 11, as will be described later.

[0015] The conveying guide 12 guides the front and back surfaces of the sheet 1 drawn from the supply device 200, and leads the sheet 1 to the printing unit 400. The conveying roller 14 is rotated forward and backward in the directions of arrows D1 and D2 by a motor 35 (see FIG. 5) for driving the conveying roller, which will be described later. The nip roller 15 is rotatable in response to the rotation of the conveying roller 14, and can be moved toward and away from the conveying roller 14 and the nip force can be adjusted by a motor 37 (see FIG. 5) for adjusting the nip force. The conveying speed of the sheet 1 by the conveying roller 14 is set higher than the drawing speed of the sheet 1 by the rotation of the roll R, which applies back tension to the sheet 1 and allows it to be conveyed while kept taut.

[0016] A platen 17 of the printing unit 400 regulates the position of the sheet 1, and a cutter 20 cuts the sheet 1 on which an image has been printed. A cover 42 for the roll R prevents the sheet 1 on which an image has been printed from returning to the supply device 200. Such operations in the printing device 100 are controlled by a CPU 201 (see FIG. 5), which will be described later. The platen 17 is equipped with an adsorption means using negative pressure or electrostatic force, and is a platen that can adsorb the sheet onto the platen for stable support.

[0017] FIG. 3 is an explanatory diagram of the supply device 200, and in FIG. 3(a), the roll R has a relatively large outer diameter. An arm member (moving body) 4 is attached to the conveying guide 12 by an arm rotation shaft 5 so as to be rotatable in the directions of arrows A1 and A2. A guide portion 4b (lower guide body) that guides the underside of the sheet 1 pulled out from the roll R is formed on the upper part of the arm member 4. A torsion coil spring 3c that presses the arm member 4 in the direction of arrow A1 is interposed between the arm member 4 and a rotating cam 3a of the drive unit 3. The rotating cam 3a is rotated by a pressing force adjustment motor 34 (see FIG. 5), which will be described later, and the force with which the torsion coil spring 3c presses the arm member 4 in the direction of arrow A1 changes depending on the rotation position of the rotating cam 3a. When the leading end of the sheet 1 (a part of the sheet 1 including the leading end) is set in the sheet supply path through the gap between the arm member 4 and the separation flapper 10, the pressing force of the arm member 4 by the torsion coil spring 3c is switched between three stages according to the rotational position of the rotating cam 3a. That is, the pressing state can be switched between a pressing state with a relatively small force (pressing force of a weak nip), a pressing state with a relatively large force (pressing force of a strong nip), and a pressing state where no pressing force is released.

[0018] A swinging member 7 is swingably attached to the arm member 4, and first and second driven rotors (rotators) 8, 9 are rotatably attached to the swinging member 7, positioned at different positions in the circumferential direction of the roll R. These driven rotors 8, 9 move according to the outer shape of the roll R, and press against the outer periphery of the roll R from below in the direction of gravity by applying a pressing force in the direction of arrow A1 to the arm member 4. That is, the driven rotors 8, 9 press against the outer periphery of the roll R from below in the direction of gravity relative to the horizontal central axis of the roll R. The pressing force is changed according to the pressing force pressing the arm member 4 in the direction of arrow A1.

[0019] A plurality of arm members 4, each having a swinging member 7, are provided at different positions in the X-axis direction. As shown in Fig. 3(b), the swinging member 7 is provided with a bearing portion 7a and a shaft fastening portion 7b, which receive the rotation shaft 4a of the arm member 4 with a predetermined play.

[0020] The bearing 7a is located at the center of gravity of the oscillating member 7 and is supported by the rotating shaft 4a so that the oscillating member 7 maintains a stable position in the X-axis, Y-axis, and Z-axis directions. Because the rotating shaft 4a is supported with some play, the oscillating member 7, regardless of its position in the X-axis direction, is displaced along the outer periphery of the roll R by the pressing force applied to the arm member 4 in the direction of arrow A1. This configuration (equalizing mechanism) allows the first and second driven rotors 8 and 9 to change their pressing positions against the outer periphery of the roll R. As a result, the contact area between the sheet 1 and the first and second driven rotors 8 and 9 is always maximized, and the pressing force applied to the sheet 1 is equalized, thereby suppressing variations in the conveying force of the sheet 1. The pressing of the driven rotors 8 and 9 against the outer periphery of the roll R prevents the sheet 1 from sagging and increases the conveying force.

[0021] A separation flapper 10 located above the arm member 4 is attached to the main body (printer main body) of the printing device 100 so as to be rotatable around a flapper rotation shaft 11 in the directions of arrows B1 and B2. The separation flapper 10 is configured to abut against and lightly press the outer circumferential surface of the roll R by its own weight. If it is necessary to press the roll R more firmly, a biasing force from a biasing member such as a spring may be used. A driven roller 10a is rotatably provided at the contact point between the separation flapper 10 and the roll R to reduce the effect of the pressing force on the sheet 1. Furthermore, a separation portion 10b at the tip of the separation flapper 10 is formed to extend as close as possible to the surface of the roll R to make it easier to separate the leading edge of the sheet from the roll R.

[0022] The sheet 1 is pulled out from the roll R as it passes over the driven rotors 8 and 9, its underside guided by the guide portion 4b at the top of the arm member 4, and then fed through the feed path formed between the separation flapper 10 and the arm member 4. In this way, the driven rotors 8 and 9 are pressed against the outer periphery of the roll R from below, and the underside of the sheet 1 pulled out as it passes over the driven rotors 8 and 9 is guided by the guide portion 4b. This allows the sheet 1 to be fed smoothly using its own weight. Furthermore, the driven rotors 8 and 9 and the guide portion 4b move in accordance with the outer diameter of the roll R, so that the sheet 1 can be reliably pulled out and fed from the roll R regardless of the outer diameter of the roll R.

[0023] One of the features of the device in this embodiment is its automatic sheet loading function (automatic sheet feed function). In automatic loading, when a user loads an unused roll R into the device, the device detects the leading edge of the sheet while rotating the roll R in the direction opposite to the sheet supply (sheet feeding) direction (referred to as the reverse direction or second direction, the direction of arrow C2 in FIG. 3(a)). The device then rotates the roll R in the sheet supply rotation direction (referred to as the forward direction or first direction, the direction of arrow C1 in FIG. 3(a)) and automatically feeds the leading edge of the sheet separated from the roll R. The sensor unit 6 is a unit that includes a leading edge detection sensor that detects when the leading edge of the sheet 1 peels off from the outer peripheral surface of the roll R (sheet separation). The leading edge of the sheet 1 detected by the sensor unit 6 is automatically inserted into the sheet supply path between the arm member 4 and the separation flapper 10 and fed. A more detailed procedure for this automatic loading function will be described later.

[0024] Furthermore, the printing apparatus 100 of this example is equipped with two supply devices 200, one above the other, and can switch from a state in which the sheet 1 is being supplied from one supply device 200 to a state in which the sheet 1 is being supplied from the other supply device 200. In such a case, one supply device 200 rewinds the sheet 1 that it had been supplying onto the roll R. The leading edge of the sheet 1 is retracted to a position where it can be detected by the sensor unit 6 or another sheet edge sensor provided near the sensor unit 6.

[0025] FIG. 4 is an explanatory diagram of the supply device 200 when the outer diameter of the roll R is relatively small. The arm member 4 is constantly pressed in the direction of arrow A1 by the torsion coil spring 3c, and therefore rotates in the direction of arrow A1 as the outer diameter of the roll R decreases. Furthermore, by rotating the rotating cam 3a in response to changes in the outer diameter of the roll R, the pressing force of the arm member 4 by the torsion coil spring 3c can be maintained within a predetermined range regardless of changes in the outer diameter of the roll R. The separation flapper 10 is also constantly pressed in the direction of arrow B1, and therefore rotates in the direction of arrow B1 as the outer diameter of the roll R decreases. As a result, even when the outer diameter of the roll R decreases, the separation flapper 10 forms a supply path between itself and the conveying guide 12, and guides the upper surface of the sheet 1 with its lower surface 10c. In this way, the arm member 4 and the separation flapper 10 rotate in response to changes in the outer diameter of the roll R, forming a supply path of approximately constant size between them regardless of the outer diameter of the roll R.

[0026] FIG. 5 is a block diagram illustrating an example of the configuration of a control system in the printing apparatus 100. The CPU 201 of the printing apparatus 100 controls each section of the printing apparatus 100, including the supply device 200, the sheet conveying section 300, and the printing section 400, in accordance with a control program stored in the ROM 204. The type, width, and various setting information of the sheet 1 are input to the CPU 201 from the operation panel 28 via the input / output interface 202. The CPU 201 is also connected to various external devices 29, including host devices such as personal computers, via the external interface 205, and exchanges various information, such as print data, with the external devices 29. The CPU 201 also writes and reads information related to the sheet 1 to and from the RAM 203. The motor 33 is a roll drive motor for rotating the roll R forward and backward via the spool member 2, and constitutes a drive mechanism (rotation mechanism) capable of rotating the roll R. The pressing force adjustment motor 34 is a motor that rotates the rotating cam 3a to adjust the pressing force on the arm member 4, and the transport roller drive motor 35 is a motor that rotates the transport roller 14 forward and reverse. The roll sensor 32 is a sensor that detects the spool member 2 of the roll R when the roll R is set in the supply device 200. The roll rotation amount sensor 36 is a sensor (rotation angle detection sensor) that detects the rotation amount of the spool member 2, i.e., the roll R, and is, for example, a rotary encoder that outputs a number of pulses corresponding to the rotation amount of the roll R.

[0027] <Sheet supply preparation process> FIG. 6 is a flowchart for explaining the supply preparation process for the sheet 1, which starts with setting the roll R.

[0028] The CPU 201 of the printing apparatus 100 waits in a state in which the arm member 4 is pressed in the direction of arrow A1 with a "weak nip pressure" (weak nip state), and first determines whether the roll R has been set (step S1). In this example, when the roll sensor 32 detects the spool member 2 of the roll R, it determines that the roll R has been set. After the roll R has been set, the CPU 201 switches the arm member 4 to a state in which the arm member 4 is pressed in the direction of arrow A1 with a "strong nip pressure" (strong nip state) (step S2). Next, the CPU 201 executes a sheet leading edge setting process to set the leading edge of the sheet 1 between the arm member 4 and the separation flapper 10 into the sheet supply path (step S3). This sheet leading edge setting process (automatic loading) sets (inserts) the leading edge of the sheet 1 into the sheet supply path. The sheet leading edge setting process will be described in detail later.

[0029] Thereafter, the CPU 201 rotates the roll R in the direction of arrow C1 using the roll drive motor 33 to start feeding the sheet 1 (step S4). When the leading edge of the sheet 1 is detected by the sheet sensor 16 (step S5), the CPU 201 rotates the conveying roller 14 forward in the direction of arrow D1 to pick up the leading edge of the sheet 1, and then stops the motors 33 and 35 (step S6). Thereafter, the CPU 201 releases the pressing force that presses the arm member 4 in the direction of arrow A1, and separates the first and second driven rotors 8 and 9 from the roll R (nip release state) (step S7).

[0030] Thereafter, the CPU 201 determines whether the sheet 1 was conveyed in the sheet conveying section 300 while being skewed (skewed). Specifically, the sheet 1 is conveyed a predetermined distance in the sheet conveying section 300, and the amount of skew occurring at that time is detected by a carriage carrying the print head 18 or a sensor provided in the sheet conveying section 300. If the amount of skew is greater than a predetermined allowable amount, the sheet 1 is repeatedly fed and back-fed by applying back tension to the sheet 1 and rotating the conveying roller 14 and the roll R forward and backward. This operation corrects the skew of the sheet 1 (step S8). In this way, by setting the feeder 200 to a nip release state during the correction of the skew of the sheet 1 and the operation of printing an image on the sheet 1, it is possible to prevent the influence of the driven rotors 8 and 9 on the accuracy of correcting the skew of the sheet 1 and the accuracy of printing an image. Thereafter, the CPU 201 causes the sheet conveying unit 300 to move the leading edge of the sheet 1 to a standby position (fixed position) in the printing unit 400 before printing starts (step S9). This completes preparations for supplying the sheet 1. Thereafter, the sheet 1 is pulled out from the roll R as the roll R rotates, and is conveyed to the printing unit 400 by the sheet conveying unit 300.

[0031] Hereinafter, as an embodiment of the present invention, the sheet leading edge setting process (step S20) in FIG. 5 in the basic configuration of the printing apparatus 100 will be described.

[0032] (First embodiment) In this embodiment, an optical sensor whose output changes depending on the distance between the sensor unit 6 and the surface (outer surface) of the sheet 1 is used as the sensor unit 6. Then, based on the change in the output of the sensor unit 6 while the roll R is rotating in the reverse direction (the direction of arrow C2), it is detected that the leading edge of the sheet 1 has peeled off and separated from the outer peripheral surface of the roll R, and then the roll R is rotated in the forward direction of arrow C1 to supply the sheet 1.

[0033] As shown in FIG. 7 , the sensor unit 6 of this example incorporates a light-emitting element 6c such as an LED and a light-receiving element 6d such as a photodiode. Light emitted from the light-emitting element 6c toward the roll R is reflected by the surface of the sheet 1 on the roll R and then detected by the light-receiving element 6d. The light emitted from the light-emitting element 6c and detected by the light-receiving element 6d includes specularly reflected light reflected from the surface of the sheet 1 on the roll R. The output value of the light-receiving element 6b varies depending on the distance between the sensor unit 6 and the downward-facing surface of the sheet 1 (the outer surface of the sheet that was the outer peripheral surface of the roll and is the surface to be printed by the printing unit). In other words, the output value of the light-receiving element 6b increases as the distance (spacing) between the sensor unit 6 and the surface of the sheet 1 decreases, and decreases as the distance (spacing) increases. The sensor unit 6 may be configured such that the output value of the detection signal changes depending on the distance between the sensor unit 6 and the surface of the sheet 1. The light-emitting element 6c and the light-receiving element 6d are not limited to LEDs and photodiodes. Furthermore, the light detected by the light-receiving element 6d is not limited to specularly reflected light. The sensor unit 6 is connected to a CPU 201 (see FIG. 5), and the CPU 201 acquires the detection result of the sensor unit 6 at any timing.

[0034] 8 and 9 are explanatory diagrams of the sheet leading edge setting process (step S3 in FIG. 6) using the sensor unit 6. As described above, the sheet leading edge setting process (automatic loading) is a process in which, after the roll R is set, the leading edge of the sheet 1 on the roll R is automatically inserted into the sheet supply path between the arm member 4 and the separation flapper 10 and fed out. The arm member 4 faces the front surface of the sheet 1 (the outer surface of the sheet), and the separation flapper 10 faces the back surface of the sheet 1 (the inner surface of the sheet).

[0035] Prior to starting the sheet leading edge setting process, the CPU 201 first determines whether the roll R has been set (step S1 in FIG. 6). In this example, when the roll sensor 32 detects the spool member 2 of the roll R, it determines that the roll R has been set. After the roll R has been set, the CPU 201 switches the arm member 4 to a state in which it presses in the direction of arrow A1 with a "strong nip pressing force" (strong nip state) (step S2 in FIG. 6).

[0036] In the subsequent sheet leading edge setting process (step S3 in FIG. 6), the CPU 201 first rotates the roll R in the opposite direction of the arrow C2 (reverse rotation) (step S11). Then, during the reverse rotation of the roll R, it is determined whether the output of the detection signal (sensor signal level) of the sensor unit 6 has changed so as to drop from the H level range (within the first level range) to the L level range (within the second level range) (step S12).

[0037] FIG. 9(a) is an explanatory diagram of an example of a waveform of the sensor output, in which the rotation angle of the roll R at the start of reverse rotation is set to 0 degrees. Normally, the sensor output is at L level. When the roll R rotates 170 degrees reversely, as shown in FIG. 9(b), the outer surface of the leading edge of the sheet 1 approaches the detection position of the sensor unit 6, and the sensor output rises (increases) from L level to H level, as shown in FIG. 9(a).

[0038] More specifically, when the roll R rotates 170 degrees in the reverse direction, the leading edge of the sheet 1 passes the contact position of the driven roller 10a of the separation flapper 10. The leading edge of the sheet 1 then leaves the contact position, begins to peel from the outer circumferential surface of the roll, and falls onto the arm member 4 due to its own weight and the return force of the bent sheet. At this time, as shown in FIG. 9(b), the sheet moves so that the outer surface of the leading edge of the sheet 1 gradually approaches the detection position of the sensor unit 6. When the roll R rotates another 200 degrees in the reverse direction, the outer surface of the leading edge of the sheet 1 passes the detection position on the sensor unit 6, as shown in FIG. 9(c). The strong reflected light from the outer surface of the sheet disappears, and only weak reflected light is received from the surface of the roll R, which is farther away. The sensor output then drops (decreases) from H level to L level. After that, when the roll R rotates further in the reverse direction by an angle θ, the leading edge of the sheet 1 reaches the contact position of the driven rotor 8. The H level and L level are the two levels obtained by dividing the output intensity of the sensor unit 6. The H level occurs when the distance between the sensor unit 6 and the sheet 1 on the roll R is small, and the L level occurs when the distance is large. A threshold value TH, which serves as the boundary between these levels, is preset and stored in a nonvolatile memory in the printer or the sensor unit 6. The threshold value TH is set based on the sensor outputs L0 and H0. That is, the threshold value TH is set based on the intermediate value between the minimum and maximum levels of the sensor output when the roll R is rotated one or more times (e.g., multiple times). For example, if the minimum level sensor output is L0 and the maximum level sensor output is H0, the threshold value TH can be set as the intermediate value between these sensor outputs L0 and H0 (TH = (H0 + L0) / 2). Because the threshold value TH varies due to variations in the sensor unit 6, it is desirable to measure the sensor outputs L0 and H0 for each sensor unit 6 and set the threshold value TH based on the measured values.

[0039] As described above, the sensor output increases in response to the movement of the outer surface of the sheet peeled from the roll R toward the sensor detection position. Then, the sensor output decreases in response to the movement of the outer surface of the sheet away from the sensor detection position due to the subsequent rotation of the roll in the second direction. By capturing this change in sensor output (predetermined change), it is possible to accurately determine the timing when the sheet peeled from the roll reaches the guide surface and sheet peeling is completed.

[0040] As shown in FIG. 9B, when the leading edge 1 of the sheet 1 passes the sensor unit 6, the sensor output changes from H level to L level. If the sensor output remains at L level for a certain period of time, the rotation of the roll R is stopped (steps S13 and S14). Specifically, the system determines whether the sensor output remains at L level for a certain period of time during which the roll R rotates in the reverse direction by a certain angle A after the sensor output changes from H level to L level. If this state continues, the rotation of the roll R is stopped. The certain angle A is an angle smaller than the angle θ, and in this example, it is half the angle θ (A=θ / 2). When the rotation of the roll R is stopped in step S14, the leading edge of the sheet 1 is positioned on the arm member 4 between the sensor unit 6 and the driven rotor 8. Therefore, by subsequently rotating the roll R forward in the direction of arrow C1 (step S15), the leading edge of the sheet 1 can be automatically inserted into the sheet feeding path between the arm member 4 and the separation flapper 10 and fed (automatic loading).

[0041] If the sensor output does not change from H level to L level even after the roll R has rotated in the reverse direction one or more times (a predetermined amount of 360 degrees or more), the process proceeds from step S16 to step S17. Furthermore, if the sensor output does not remain at L level for a certain period of time even after the roll R has rotated in the reverse direction one or more times, the process proceeds from step S16 to step S17. If the leading edge of the sheet 1 does not separate from the outer surface of the roll R during one rotation of the roll R, it is considered that the sheet was not properly separated from the outer surface of the roll R. Furthermore, if the leading edge of the sheet 1 that separated from the outer surface of the roll R does not leave the sensor unit 6 during one rotation of the roll R, it is considered that the separated sheet has jammed on the sensor. In either case, automatic sheet feeding cannot be performed. In step S17, the rotation of the roll R is stopped, and the user is notified that automatic loading (automatic sheet feeding) could not be performed, and the user is prompted to manually insert the leading edge of the sheet 1 into the sheet feed path (manual sheet feeding). After inserting the leading edge of the sheet, the user instructs the device to feed the sheet. Based on this instruction, roll R begins to rotate in the forward direction and feeds the inserted sheet into the device. As described above, in this embodiment, after roll R is set, the leading edge of sheet 1 can be automatically inserted into the sheet supply path and fed out. Therefore, the user does not need to manually insert the leading edge of sheet 1 into the sheet supply path after setting roll R, which reduces the workload when setting roll R.

[0042] (Second embodiment) 10 and 11 are explanatory diagrams of a second embodiment of the present invention. As in the previously described embodiment, the output of the sensor unit 6 varies depending on the distance between the sensor unit 6 and the surface of the sheet 1. For example, in the case of a sheet 1 with a large amount of cavities and a high stiffness, when the roll R is rotated in the reverse direction of arrow C2, the sensor output may vary during the period from when the leading edge 1 of the sheet 1 passes the driven rotor 9 to when it passes the driven roller 10a. That is, during that period, the output of the sensor unit 6 may temporarily rise from L level to H level and then return to L level.

[0043] FIG. 10 is an explanatory diagram of the output waveform of the sensor unit 6 and the behavior of the leading edge of the sheet 1 when a roll R of sheet 1 with a large amount of voids is rotated in reverse. When the leading edge of the sheet 1 is near the driven roller 10a, the roll R starts rotating in the direction of arrow C2. When the roll R rotates approximately 45 degrees from the rotation start position, the leading edge 1 of the sheet 1 passes through the driven roller 10a and falls onto the arm member 4, as shown in FIG. 9B. As a result, as shown in FIG. 10A, the output of the sensor unit 6 rises from L level to H level when the rotation angle of the roll R is approximately 45 degrees. After that, when the roll R rotates approximately 90 degrees from the rotation start position, the leading edge 1 of the sheet 1 passes over the sensor unit 6, as shown in FIG. 9C. As a result, as shown in FIG. 10A, the output of the sensor unit 6 falls from H level to L level when the rotation angle of the roll R is approximately 90 degrees.

[0044] When the roll R continues to rotate in the reverse direction and rotates approximately 270 degrees from the rotation start position, the leading edge of the sheet 1 may be positioned above the roll R, and the weight of the leading edge 1 may cause the sheet 1 to bend as shown in FIG. 10(b). When such a bend occurs, the outer surface of the sheet 1 approaches the sensor unit 6 as shown in FIG. 10(b). As a result, as shown in FIG. 10(a), the output of the sensor unit 6 rises from L level to H level when the rotation angle of the roll R is approximately 270 degrees. Thereafter, as the roll R continues to rotate in the reverse direction, the bent portion of the sheet 1 is taken up by the roll R, and the sheet 1 moves away from the sensor unit 6 as shown in FIG. 10(c). As a result, as shown in FIG. 10(a), the output of the sensor unit 6 returns from H level to L level when the rotation angle of the roll R is approximately 350 degrees.

[0045] If the reverse rotation of the roll R continues, such a change in the output of the sensor unit 6 is repeated. In this embodiment, even when the sensor output changes in this way, the position of the leading edge of the sheet 1 can be identified, and the leading edge can be automatically inserted into the sheet supply path between the arm member 4 and the separation flapper 10 and fed out (sheet leading edge setting process).

[0046] FIG. 11 is a flowchart for explaining the sheet leading edge setting process (automatic loading) in this embodiment.

[0047] Before starting the sheet leading edge setting process, the CPU 201 first determines whether the roll R has been set (step S1 in FIG. 6). After the roll R has been set, the CPU 201 switches the arm member 4 to a state in which it presses in the direction of arrow A1 with the "strong nip pressing force" (strong nip state) (step S2 in FIG. 6).

[0048] In the sheet leading edge setting process (step S3 in FIG. 6), the CPU 201 rotates the roll R in the opposite direction of the arrow C2 (reverse rotation) (step S21) and saves the sensor output (step S22). For example, the CPU 201 may rotate the roll R at a constant speed and save the sensor output at regular time intervals. To more accurately identify the position of the leading edge of the sheet 1, the sensor output may be saved in synchronization with pulses from the roll rotation amount sensor 36 (see FIG. 5), which is output in accordance with the amount of rotation of the roll R. In this case, the rotation of the roll R does not need to be constant. It is sufficient for the sensor output to collect data during one rotation of the roll R. However, taking into account the slack in the sheet 1 when the roll R is set, the roll R is rotated one or more times (one and a half rotations (540 degrees) or more in this example) to collect data (step S23).

[0049] After data collection is complete, the CPU 201 stops the rotation of the roll R (step S24) and extracts the maximum value Hd and minimum value Ld of the sensor output from the sensor output data stored in the RAM 203 (step S25). Then, it determines whether the difference between the maximum value Hd and the minimum value Ld (Hd-Ld) exceeds a value (THa) required to identify the position of the leading edge of the sheet 1 (step S26). The threshold value THa may be a fixed value, or may be set for each type of sheet 1. Furthermore, the value THa may be changed depending on the high humidity environment in which the sheet 1 swells, or the low temperature and low humidity environment in which the sheet 1 becomes stiff.

[0050] If the difference (Hd-Ld) exceeds the value (THa), the CPU 201 calculates thresholds THd1 and THd2 for determining whether the sensor output is at an H level or an L level based on the maximum value Hd and the minimum value Ld (steps S26 and S27). The thresholds THd1 and THd2 are set as independent thresholds with hysteresis, taking into account noise fluctuations wn due to signal disturbances and the like. A change in the sensor output from an H level to an L level is determined using the threshold THd1, and a change from an L level to an H level is determined using the threshold THd2. The reason for setting the thresholds THd1 and THd2 based on the sensor output data obtained when the roll R is rotated is that the light reflection characteristics vary depending on the type of sheet, which may cause fluctuations in the sensor output value of the sensor unit 6. When identifying the leading edge position of a known sheet, values ​​previously stored in the ROM 204 (see FIG. 5) may be set as the thresholds THd1 and THd2. If the signal-to-noise ratio of the acquired maximum value Hd and minimum value Ld is sufficiently large, a single value intermediate between the maximum value Hd and the minimum value LdHd may be set as the threshold for determining whether the sensor output changes from H level to L level and from L level to H level.

[0051] The CPU 201 then analyzes the sensor output data stored in the RAM 203 and, based on the data for one revolution of the roll R, determines the duration PL of the L level after the change from H level to L level (step S28). The rotation angle of the roll R corresponding to this L level duration PL may be calculated based on the output pulse of the roll rotation amount sensor 36 (see FIG. 5) or data obtained at regular intervals. If the sensor output changes multiple times so that there are multiple durations PLA corresponding to the L level duration PL that are equal to or greater than the rotation angle A of the roll R, the CPU 201 selects the longest duration PLAmax among them (steps S29 and S30). The CPU 201 then identifies the separation position where the leading edge of the sheet 1 peels off and separates from the surface of the roll R (step S31), as shown in FIG. 9(b) above. Specifically, the CPU 201 identifies the change point Pa of the sensor output immediately before the longest duration PLAmax, as shown in FIG. 10(a). 9(b), the change point Pa corresponds to the rotation position (separation position) when the leading edge 1 of the sheet 1 peels off and separates from the surface of the roll R. If there is only one duration PLA corresponding to a rotation angle A or more, the separation position of the leading edge of the sheet 1 is identified from the change point Pa of the sensor output immediately before that duration PLA (steps S32 and S33).

[0052] After the separation position of the leading edge of the sheet 1 is identified in step S31 or S33, the CPU 201 reverses the rotation of the roll R in the direction of arrow C2 to the separation position (step S34). As a result, the leading edge 1 of the sheet 1 is peeled off and separated from the surface of the roll R as shown in FIG. 9(b) above, and is positioned on the arm member 4 between the sensor unit 6 and the driven rotor 8. Therefore, by subsequently rotating the roll R forward in the direction of arrow C1 (step S35), the leading edge of the sheet 1 can be automatically inserted into the sheet supply path between the arm member 4 and the separation flapper 10 and fed out (automatic loading).

[0053] If it is determined in the previous step S26 that the difference (Hd-Ld) does not exceed the threshold value THa, and if it is determined in the previous step S22 that there is no duration PLA corresponding to a rotation angle A or greater, the process proceeds to step S36. In step S36, the rotation of the roll R is stopped, and the user is notified that automatic loading could not be performed, and the user is prompted to manually insert the leading edge of the sheet 1 into the sheet supply path.

[0054] As described above, in this embodiment, even if a temporary fluctuation occurs in the output of the sensor unit 6, it is possible to identify the rotational position (separation position) of the roll R when the leading edge of the sheet 1 separates from the roll R based on the sensor output when the roll R is rotated in reverse. After that, by rotating the roll R in reverse to the separation position and then rotating the roll R in the forward direction, the leading edge of the sheet 1 can be automatically inserted into the sheet supply path and fed out.

[0055] (Third embodiment) FIG. 12 is a block diagram of a control system in a third embodiment of the present invention. The sensor unit 6 is a sensor whose output changes depending on the distance between the sensor unit 6 and the surface of the roll R, as in the first embodiment. In this embodiment, an LED driver 6e with a dimming function under the control of the CPU 201 is connected to the LED light-emitting element 6c. The amplification factor of the light-emitting intensity of the light-emitting element 6c can be changed by adjusting the current flowing through the light-emitting element 6c. A current-voltage conversion circuit 6h and an amplifier circuit 6i are connected to the photodiode light-receiving element 6d. The amplification factor of the light-receiving sensitivity of the light-receiving element 6d can be changed by adjusting the resistance value of a digital potential meter 6f under the control of the CPU 201. The sensor unit 6 also includes a nonvolatile memory, EEPROM 6g, for storing the amplification factors of the sensor unit 6 (the amplification factor of the light-emitting intensity of the light-emitting element 6c and the amplification factor of the light-receiving sensitivity of the light-receiving element 6d).

[0056] FIG. 13 is an explanatory diagram of the output waveform of the sensor unit 6 when the roll R is rotated in the reverse direction. When the maximum value Hd of the sensor output of the sensor unit 6 is greater than the upper limit judgment value THmax, the sensor output may be saturated. When the minimum value Ld of the sensor output of the sensor unit 6 is smaller than the lower limit judgment value THmin, the sensitivity of the sensor unit 6 may be insufficient. Furthermore, if the difference between the maximum value Hd and the minimum value Ld is less than a predetermined value, the sensor output may be affected by stationary noise, making it difficult to detect the position of the leading edge of the sheet 1. Therefore, a judgment value is also set to determine whether the difference between the maximum value Hd and the minimum value Ld is sufficient.

[0057] In this embodiment, in the initial stage of the sheet leading edge setting process (automatic loading) similar to the embodiment described above, the roll R is rotated in reverse, and the amplification factor of the sensor unit 6 is adjusted based on the output (sensor output) of the detection signal of the sensor unit 6 at that time.

[0058] FIG. 14 is a flowchart for explaining the amplification factor adjustment process for adjusting the amplification factor of the sensor unit 6 (sensor amplification factor).

[0059] First, the CPU 201 initializes the data processing area to secure an area for processing output data from the sensor unit 6 (step S41), and then sets an initial value for the sensor gain (step S42). The sensor gain adjusted in the previous gain adjustment process is stored in the EEPROM 6g, and the stored gain is set as the initial value. If no gain is stored, a predetermined gain is set as the initial value. In this case, the initial gain may be set according to the type, diameter, width, etc. of the roll R input in advance via the operation panel 28. The diameter and width of the roll R may be set in the printing device itself, or may be set by a driver on a terminal such as a personal computer connected to the printing device by wire or wirelessly. Furthermore, a temperature and humidity sensor may be provided to set the initial gain according to the environmental temperature and humidity when the roll R is set.

[0060] Next, the CPU 201 rotates the roll R in the direction of arrow C2 one or more times, acquires the sensor output at that time (step S43), and calculates a moving average for each predetermined rotation angle of the roll R from the sensor output (step S44). In this example, the sensor output for two rotations of the roll R is acquired, and a moving average is calculated for each predetermined rotation angle of the roll R. The maximum value Hd and minimum value Ld of the moving average data are extracted (step S45), and it is determined whether the maximum value Hd is equal to or greater than the upper limit judgment value THmax in FIG. 13 (step S46). If the maximum value Hd is equal to or greater than the upper limit judgment value THmax, the CPU 201 determines whether the amplification factor of the light emission intensity of the light-emitting unit 6c is within a predetermined range (first allowable range) (step S47). If the amplification factor of the light emission intensity of the light-emitting unit 6c is within the predetermined range, the CPU 201 reduces the amplification factor of the light emission intensity (step S48). If it is outside the predetermined range, the CPU 201 reduces the amplification factor of the light reception intensity of the light-receiving unit 6d (step S49). This makes it possible to prevent the sensor output from becoming saturated.

[0061] On the other hand, if the maximum value Hd is less than the upper limit judgment value THmax, the CPU 201 determines whether the minimum value Ld is less than the lower limit judgment value THmin (step S50). If the minimum value Ld is less than the lower limit judgment value THmin, the CPU 201 determines whether the amplification factor of the light-emitting intensity of the light-emitting unit 6c is within a predetermined range (step S51). If the amplification factor of the light-emitting intensity of the light-emitting unit 6c is within the predetermined range, the CPU 201 increases the amplification factor of the light-emitting intensity (step S52). If the amplification factor is outside the predetermined range, the CPU 201 increases the amplification factor of the light-receiving unit 6d (step S53). This increases the detection sensitivity of the sensor unit 6.

[0062] Furthermore, if the minimum value Ld is equal to or greater than the lower limit judgment value THmin, the CPU 201 determines whether the difference (Hd-Ld) between the maximum value Hd and the minimum value Ld is less than a predetermined judgment value (step S51). If the difference (Hd-Ld) is less than the predetermined judgment value, the sensor output may be affected by stationary noise, making it difficult to detect the position of the leading edge of the sheet 1. In this case, the process proceeds from step S4 to step S51 to increase the amplification factor of the light emission intensity or the received light intensity of the sensor unit 6. If the difference (Hd-Ld) is equal to or greater than the predetermined judgment value, it is determined that the amplification factors of the light emission intensity and the received light intensity of the sensor unit 6 have been appropriately adjusted, and the adjustment process of the amplification factor is terminated.

[0063] After adjusting the amplification factors of the light-emission intensity or the received light intensity in steps S48, S49, S52, and S53, the CPU 201 determines whether the amplification factors are within a predetermined range (step S55). That is, it determines whether the light-emission intensity is within a predetermined range (first tolerance range) and whether the received light intensity is within a predetermined range (second tolerance range). If the amplification factors of the light-emission intensity and the received light intensity are within the predetermined range, the CPU 201 returns to step S41 to reconfirm whether the amplification factors are appropriate. If the amplification factors of the light-emission intensity and the received light intensity are not within the predetermined range, the CPU 201 determines that the amplification factors have exceeded the adjustment limit and executes error processing, such as outputting an error message. If the amplification factors of the light-emission intensity and the received light intensity are within the predetermined range, the CPU 201 may count the number of times the amplification factors are increased and decreased in steps S48, S49, S52, and S53, and execute error processing if the count value is equal to or greater than a certain number.

[0064] In this embodiment, the output of the sensor unit 6 can be optimized by adjusting the amplification factor of the light emission intensity and the light reception intensity of the sensor unit 6 based on the sensor output when the roll R is rotated in the reverse direction one or more times. Therefore, the position of the leading edge of various sheets 1 with different reflectances can be reliably identified.

[0065] (Fourth embodiment) 15 to 17 are diagrams for explaining the fourth embodiment of the present invention.

[0066] 15A and 15B are diagrams illustrating the position of the sensor unit 6 disposed on the arm member of the sheet supplying device 200; in FIG. 15A, a roll R with a large winding diameter is set, and in FIG. 15B, a roll R with a small winding diameter is set. In this embodiment, the sensor unit 6 is disposed so as to satisfy the positional relationship of the following formula (1) regardless of the winding diameter of the roll R as shown in FIGS. 15A and 15B. Furthermore, when the roll R is formed by winding the sheet 1 around a tube such as a cardboard tube, the positional relationship of the following formula (1) is satisfied even when only the tube such as the cardboard tube is set and the roll R has the smallest winding diameter. α>β(α1>β1, α2>β2) (1)

[0067] In FIG. 15(a), α1 denotes the distance between position P1 (the contact position of the upper guide against the roll R) where the roll R and the separation flapper 10a contact each other, and position P2 (the contact position of the lower guide against the roll) where the roll R and the rotation follower 8 contact each other. Also, in FIG. 15(b), α2 denotes the distance between position P1 and position P2. These distances α1 and α1 are collectively referred to as distance α. Also, in FIG. 15(a), β1 denotes the distance between the detection position of the sensor unit 6 and position P2, and in FIG. 15(b), β2 denotes the distance between the detection position of the sensor unit 6 and position P2. These distances β1 and β1 are collectively referred to as distance β. The detection position of the sensor unit 6 is the position of a detection unit of the sensor unit 6 that can detect the position of the tip, and corresponds to the positions of the light-emitting unit 6c and the light-receiving unit 6d, for example.

[0068] In this way, the sensor unit 6 is disposed at a position on the arm member so as to satisfy the conditions that the distance β1 is smaller than the distance α1 as shown in Figure 15(a) and the distance β2 is smaller than the distance α2 as shown in Figure 15(b). In other words, regardless of the winding diameter of the roll R, the position at which the sensor unit 6 is disposed is set so as to satisfy the relationship α>β.

[0069] Figure 16 is an explanatory diagram of the light-emitting optical axis of light-emitting unit 6c in sensor unit 6, with a roll R with a large winding diameter set in Figure 16(a) and a roll R with a small winding diameter set in Figure 16(b). Angle γ1 between light-emitting optical axis I1 of light-emitting unit 6c and vector Q1 in Figure 16(a) and angle γ2 between light-emitting optical axis I2 of light-emitting unit 6c and vector Q2 in Figure 16(b) both satisfy the relationship of the following formula (2). 0°<γ(γ1, γ2)<90° (2)

[0070] Vector Q1 is a vector that faces in the normal rotation direction of roll R (direction of arrow C1) along a tangent to intersection P3 between optical axis I1 and roll R. Similarly, vector Q2 is a vector that faces in the normal rotation direction of roll R along a tangent to intersection P3 between optical axis I2 and roll R. The optical axes I1 and I2 are collectively referred to as optical axis I, vectors Q1 and Q2 are collectively referred to as vector Q, and angles γ1 and γ2 are collectively referred to as angle γ.

[0071] In this way, the sensor unit 6 is positioned so that the angle γ (γ1, γ2) between an imaginary line extending the optical axis I (I1, I2) inside the roll R and the vector Q (Q1, Q2) is an acute angle.

[0072] Fig. 17 is an explanatory diagram of the positional relationship between the light-emitting unit 6c and the light-receiving unit 6d in the sensor unit 6. Fig. 17(a) is a diagram of the main part of the sheet supply device 200 as seen from the X-axis direction, and Fig. 17(b) is a diagram of the same as seen from the Z-axis direction.

[0073] In this embodiment, the light-emitting unit 6c and the light-receiving unit 6d are arranged side by side in the axial direction (X-axis direction) of the roll R. By arranging the light-emitting unit 6c and the light-receiving unit 6d next to each other in the axial direction of the roll R, the light-emitting optical axis of the light-emitting unit 6c and the light-receiving optical axis of the light-receiving unit 6d are substantially opposed in the axial direction of the roll R. By arranging the light-emitting unit 6c and the light-receiving unit 6d in this manner, the distance between the leading edge of the sheet 1 and the sensor unit 6 can be detected regardless of the winding diameter of the roll R. In other words, when the leading edge of the sheet 1 passes the driven roller 10a of the separation flapper and falls onto the arm member 4 under its own weight due to the reverse rotation of the roll R, the position of the leading edge of the sheet 1 can be detected.

[0074] Furthermore, by setting the angle γ to an acute angle, a state exists in which the light-emitting optical axis I and the surface of the leading edge of the sheet 1 are perpendicular to each other during the period from when the leading edge 1 of the sheet 1 falls under its own weight onto the arm member 4 until it passes over the sensor unit 6 due to the reverse rotation of the roll R. That is, the light-emitting optical axis I and the surface of the leading edge of the sheet 1 are perpendicular to each other at least temporarily during the period from when the leading edge of the sheet 1 passes the driven roller 10a of the separation flapper until it falls under its own weight onto the arm member 4. In this perpendicular state, the light emitted from the light-emitting unit 6c and reflected by the surface of the leading edge of the sheet 1 is detected by the light-receiving unit 6d as the strongest specularly reflected light. Furthermore, by setting the angle between the light-emitting optical axis I and the surface of the arm member 4 onto which the leading edge of the sheet 1 falls to 90 degrees, when the leading edge of the sheet 1 is aligned with the surface of the arm member 4, the light-emitting optical axis I and the surface of the leading edge of the sheet 1 are perpendicular to each other.

[0075] In this way, there is a state in which the light receiving unit 6d receives the strongest specularly reflected light between the time when the leading edge 1 of the sheet 1 falls under its own weight onto the arm member 4 and the time when it passes over the sensor unit 6. Therefore, when the leading edge 1 of the sheet 1 falls under its own weight onto the arm member 4, the sensor output of the sensor unit 6 becomes H level more reliably, and the sensor output required to identify the position of the leading edge of the sheet 1 can be obtained more reliably.

[0076] Furthermore, the light-emitting unit 6c and the light-receiving unit 6d are arranged in line in the axial direction of the roll R, with the light-emitting optical axis and the light-receiving optical axis substantially facing each other. This minimizes the effects on the sensor output of factors such as the type of sheet 1, changes in the roll diameter, and changes in the behavior of the leading edge of the sheet 1. Furthermore, by increasing the proportion of the sensor output when the light-receiving unit 6d receives specularly reflected light, noise caused by external light can be minimized. If the relationship between the above formulas (1) and (2) is not satisfied and α<β,γ>90°, the optical axis of the sensor unit 6 always faces the separation flapper 10, making it impossible to obtain a sensor output that corresponds to the distance from the leading edge of the sheet 1.

[0077] The position where the sensor unit 6 is installed is not limited to the arm member, and the sensor unit 6 may be installed at a position other than the arm member, taking into consideration the optical characteristics of the sensor unit 6 and the like.

[0078] (Fifth embodiment) Figure 18 is an explanatory diagram of the configuration of a sheet supplying device 200 in a fifth embodiment of the present invention, where a roll R with a large winding diameter is set in Figure 18(a), and a roll R with a small winding diameter is set in Figure 18(b).

[0079] In this embodiment, the relationship between the arm member 4 and the vector W (W1, W2) that faces in the forward rotation direction of the roll R along a tangent at the contact point between the roll R and the rotation follower 8 is specified. That is, the supply device 200 is configured so that an intersection P4 between the vector W (W1, W2) and the surface of the arm member 4 exists regardless of the winding diameter of the roll R. Furthermore, this intersection P4 is located upstream in the conveyance direction of the sheet 1 (left side in FIG. 18 ) of an intersection P5 between the light-emitting optical axis I of the sensor unit 6 and the surface of the arm member 4.

[0080] By configuring the supply device 200 in this manner, when the roll R is rotated forward in the direction of arrow C1 to convey the sheet 1, the leading edge of the sheet 1 moves toward the arm member 4 along the vector W. Therefore, the leading edge of the sheet 1 is conveyed while contacting the arm member 4, regardless of the winding diameter of the roll R. Furthermore, because the intersection P4 is located upstream of the intersection P5 in the conveying direction, the leading edge of the sheet 1 passes over the sensor unit 6 during conveyance, regardless of the winding diameter of the roll R. Therefore, the sensor unit 6 can more reliably detect the distance between the leading edge of the sheet 1 and the sensor unit 6, regardless of the winding diameter of the roll R.

[0081] (Sixth embodiment) 19 and 21 are explanatory diagrams of a sixth embodiment of the present invention. FIG. 19(a) is an explanatory diagram of the output waveform of the sensor unit 6. FIG. 19(b) is an explanatory diagram of a state in which the leading edge of the sheet 1 has been properly peeled off from the surface of the roll R, and FIG. 19(c) is an explanatory diagram of a state in which the amount of peeling of the leading edge of the sheet 1 from the surface of the roll R is smaller than normal due to the influence of static electricity or the like. FIGS. 20(a), (b), and (c) are explanatory diagrams of the state in which the roll R is rotated forward in the direction of arrow C1 from the state in FIG. 19(c). FIG. 21 is a flowchart for explaining the sheet leading edge setting process (automatic loading) in this embodiment.

[0082] As shown in FIG. 19(b), when the leading edge of the sheet 1 is properly peeled off from the surface of the roll R, the sensor output of the sensor unit 6 changes to the waveform W1 in FIG. 19(a). That is, when the leading edge of the sheet 1 is near the driven roller 10a, the roll R starts to rotate in the reverse direction of the arrow C2. When the roll R rotates about 45 degrees, the leading edge of the sheet 1 passes through the driven roller 10a and falls. This causes the sensor output to change from the L level to the H2 level. Furthermore, when the roll R rotates about 90 degrees after starting to rotate, the leading edge of the sheet 1 passes over the sensor unit 6, as shown in FIG. 19(b), and the sensor output changes from the H level to the L level. Thereafter, by rotating the roll R forward in the direction of the arrow C1, the leading edge of the sheet 1 can be automatically inserted into the sheet feeding path and fed out.

[0083] On the other hand, as shown in FIG. 19(c), when the amount of peeling at the leading edge of the sheet 1 is smaller than normal, the sensor output of the sensor unit 6 changes as shown by waveform W2 in FIG. 19(a). That is, when the roll R starts to rotate in the reverse direction of arrow C2 from a state in which the leading edge of the sheet 1 is near driven roller 10a, and the roll R rotates approximately 45 degrees, the leading edge of the sheet 1 passes through driven roller 10a and falls. Furthermore, when the roll R rotates approximately 90 degrees from the start of rotation, the leading edge of the sheet 1 passes over the sensor unit 6, as shown in FIG. 19(c), and the sensor output changes from H level to L level. Thereafter, when the roll R is rotated forward in the direction of arrow C1, the amount of peeling at the leading edge of the sheet 1 is small as shown in FIG. 20(a), so the leading edge of the sheet 1 may collide with driven roller 10a as shown in FIG. 20(b), and a jam of the sheet 1 may occur as shown in FIG. 20(c).

[0084] The sheet leading edge setting process (automatic loading) in this embodiment prevents such jams from occurring. The same steps as those in the flowchart in FIG. 8 of the above-described embodiment are given the same step numbers and will not be described again.

[0085] Before starting the sheet leading edge setting process, the CPU 201 first determines whether the roll R has been set (step S1 in FIG. 6). After the roll R has been set, the CPU 201 switches the arm member 4 to a state in which it presses in the direction of arrow A1 with the "strong nip pressing force" (strong nip state) (step S2 in FIG. 6).

[0086] In the sheet leading edge setting process, the CPU 201 rotates the roll R one or more times in the direction opposite to the arrow C2 (reverse rotation) (step S11).

[0087] The CPU 201 calculates the amount of change (level change) when the sensor output of the sensor unit 6 changes from H level to L level during reverse rotation of the roll R, and determines whether the amount of level change is greater than a predetermined threshold ΔH1 (=H1-L) (step S61). If the amount of level change does not exceed the predetermined threshold ΔH1 (=H1-L) even after the roll R has rotated reversely one or more times, it is determined that the leading edge of the sheet 1 has not peeled off from the surface of the roll R, and the process proceeds to step S17. As described above, in step S17, the user is prompted to manually insert the leading edge of the sheet 1 into the sheet supply path. Therefore, the threshold ΔH1 serves as a criterion for determining whether the leading edge of the sheet 1 has peeled off from the surface of the roll R. L is the minimum level of the sensor output.

[0088] If the amount of change in the level of the sensor output is greater than the threshold ΔH1, the CPU 201 determines that the leading edge of the sheet 1 has peeled off from the surface of the roll R, as shown in FIG. 19(b) or (c). Then, if the L level of the sensor output continues for a certain period of time, the CPU 201 stops the rotation of the roll R (steps S13 and S14). After that, the CPU 201 determines whether the amount of change in the level of the sensor output is greater than a predetermined threshold ΔH2 (=H2-L) (step S62). If the amount of change in the level is greater than the threshold ΔH2, the CPU 201 determines that the leading edge has peeled off normally from the surface of the roll R, as shown in FIG. 19(b), and executes automatic loading (step S15). On the other hand, if the amount of change in the level is not greater than the threshold ΔH2, the CPU 201 determines that the amount of peeling of the leading edge of the sheet 1 from the surface of the roll R is smaller than normal, as shown in FIG. 19(c). In this way, if the peeling amount of the leading edge of the sheet 1 is smaller than normal, automatic loading of the sheet 1 may be possible depending on the stiffness of the sheet 1, so it is determined whether the stiffness of the sheet 1 is equal to or greater than a predetermined value (step S63). The stiffness of the sheet 1 is determined, for example, based on information about the type of sheet 1 input by the user. The criteria for determining the stiffness of the sheet 1 may be set based on the information about the type of sheet 1, as well as the width of the sheet 1, the usage state of the sheet 1, the usage environment of the printing device, and the like. If the stiffness of the sheet 1 is equal to or greater than the predetermined value, the process proceeds to step S15 to execute automatic loading, and if the stiffness of the sheet 1 is less than the predetermined value, the process proceeds to step S17 to prompt the user to manually insert the leading edge of the sheet 1 into the sheet supply path.

[0089] In this way, the peeling amount at the leading edge of the sheet 1 is detected according to the sensor output of the sensor unit 6, and automatic loading is performed on the premise that the peeling amount and the stiffness of the sheet 1 satisfy predetermined conditions. This makes it possible to prevent the sheet 1 from jamming inside the printing device.

[0090] (Seventh embodiment) 22 and 23 are explanatory diagrams of a seventh embodiment of the present invention. In this embodiment, when the leading edge of sheet 1 cannot be automatically fed into the sheet supply path, that is, when automatic loading cannot be performed, the leading edge of sheet 1 is positioned within a predetermined range for manual feeding. Fig. 22 is an explanatory diagram of the stopping position of the leading edge of sheet 1, and Fig. 23 is a flowchart for explaining the sheet leading edge setting process (automatic loading) in this embodiment.

[0091] If the leading edge of the sheet 1 cannot be automatically fed into the sheet supply path, the roll R is rotated in the reverse direction of the arrow C2 so that the leading edge of the sheet 1 is positioned within the range θ1 (visible range) between the driven roller 10a and the driven rotor 9, as shown in Figure 22. This range θ1 includes the range of the circumferential surface of the roll R that is visible to the user when the roll R is attached to or detached from the printing device. Positioning the leading edge of the sheet 1 within this range θ1 allows the user to visually recognize the leading edge of the sheet 1, improving the operability of the manual operation of inserting the leading edge of the sheet 1 into the sheet supply path.

[0092] In the sheet leading edge setting process of this embodiment, as shown in FIG. 23, an operation for stopping the leading edge of the sheet 1 at a position within a predetermined range θ1 (step S71) is added to the sheet leading edge setting process of FIG. 21 in the sixth embodiment. The CPU 201 identifies the position of the leading edge of the sheet 1 based on the processing information of steps S61, S13, and S16, then stops the rotation of the roll R (step S14), and compares the level change amount of the sensor output with a threshold ΔH2 (step S62). If the level change amount is greater than the threshold ΔH2, as described above, it is determined that the leading edge of the sheet 1 has normally peeled off the surface of the roll R, and automatic loading is executed (step S15). If the level change amount is not greater than the threshold ΔH2, automatic loading is executed on the condition that the stiffness of the sheet 1 is equal to or greater than a predetermined value, as described above (steps S63 and S15). If the stiffness of the sheet 1 is less than the predetermined value, the stiffness of the sheet 1 is low and there is a risk of a jam occurring, so the roll R is rotated in the direction of the arrow C2 in reverse so that the leading edge of the sheet 1, whose position was identified in the previous steps S61, S13, and S16, is positioned within the range θ1. Then, the process proceeds to step S17, where the user is prompted to manually insert the leading edge of the sheet 1 into the sheet supply path.

[0093] In this way, by positioning the leading edge of the sheet 1 within a predetermined range that is visible to the user, it is possible to improve the visibility of the leading edge of the sheet 1 to the user. Furthermore, by combining this with a warning displayed on a panel or the like, the user can smoothly insert the leading edge of the sheet 1 into the sheet feeding path. This allows the user to easily perform manual paper feeding.

[0094] In this example, from the viewpoint of the user's visibility of the leading edge of the sheet 1, the leading edge of the sheet 1 is set to stop within the range θ1 between the driven roller 10a and the driven rotor 9, as shown in Fig. 22. However, in order to reduce the amount of rotation of the roll R and shorten the time required for the manual insertion operation of the leading edge of the sheet 1, the leading edge of the sheet 1 may be stopped within a range between the driven roller 10a and the driven rotor 9 that is different from the range θ1.

[0095] (Variation) The sensor unit 6 is not limited to an optical sensor, and any distance sensor other than an optical sensor can be used as long as the sensor's output value changes depending on the distance to the outer surface of the sheet, which is the detection target. For example, distance sensors such as ultrasonic sensors or electrostatic sensors that detect the distance to the target without contact can also be used.

[0096] The printing apparatus is not limited to a configuration having two sheet feeders corresponding to two roll sheets, but may also be configured to have one or three or more sheet feeders. Furthermore, the printing apparatus is not limited to inkjet printing apparatuses as long as it is configured to print images on sheets fed from the sheet feeders. The printing apparatus may also use any printing method and configuration. For example, it may use either a serial scan method, in which an image is printed by repeating the scanning of the print head and the transport of the sheet, or a full-line method, in which an image is printed by continuously transporting a sheet opposite a long print head.

[0097] The present invention can be applied to various sheet supplying devices in addition to sheet supplying devices that supply sheets as print media to printing devices. For example, the present invention can be applied to devices that supply sheets to be read to reading devices such as scanners and copiers, and devices that supply sheet-like processing materials to processing devices such as cutting devices. Such sheet supplying devices can be configured separately from devices such as printing devices, reading devices, and processing devices, and may also include a control unit (CPU) for the sheet supplying device.

[0098] As described above, the sheet supplying device is not limited to a configuration in which driven rotors 8 and 9 connected to arm member 4 are pressed against roll R from below the roll R, and the position of the leading edge of roll R is detected using sensor unit 6 mounted on arm member 4. For example, as shown in FIG. 24 , a configuration is also possible in which driven rotors 8 and 9 and sensor unit 6 are disposed on fixed structure 40 provided below roll R, and roll R is pressed against driven rotors 8 and 9 by its own weight, regardless of the winding diameter of roll R. Alternatively, roll R may be pressed against driven rotors 8 and 9 using a drive mechanism (not shown).

[0099] The present invention can be widely applied to various sheet supply devices, including paper, film, and cloth, and various sheet processing devices, such as printing devices and image reading devices, that include the supply devices. The image reading device reads the image recorded on the sheet supplied from the supply device using a reading head. Furthermore, the sheet processing device is not limited to printing devices and image reading devices, but may be any device that performs various processes (e.g., processing, coating, irradiation, inspection) on the sheet supplied from the supply device. When the sheet supply device is configured as an independent device, the device may be equipped with a control unit including a CPU. Furthermore, when the sheet supply device is included in a sheet processing device, at least one of the sheet supply device and the sheet processing device may be equipped with a control unit including a CPU. [Explanation of symbols]

[0100] 1 sheet 6 Sensor unit (sensor) 6c Light-emitting part 6d Light receiving part 4b Guide part (lower guide) 10 Separation flapper (upper guide) 100 Printing Device 200 Sheet Feeder 400 Printing Unit R Roll

Claims

[Claim 1] a driving means for rotating the roll in a first direction for feeding the sheet from the roll formed by winding the sheet, and in a second direction opposite to the first direction; a lower guide that supports the sheet fed from the roll from below; a contact member that is provided above the lower guide, moves in response to a change in the outer diameter of the roll, and comes into contact with the roll at a contact position; a detection means for detecting the leading edge of the sheet when the leading edge of the sheet on the roll rotating in the second direction passes through the contact position and the sheet approaches the detection means; a contact member that is supported by the lower guide on the upstream side of the detection means in a direction in which the sheet is fed from the roll, and that comes into contact with the roll rotating in the second direction at a contact position; a sheet supplying device that changes the rotation of the roll by the driving means from the second direction to the first direction in response to an output from the detection means, A sheet feeding device, characterized in that the distance between the contact position and the detection position of the detection means in the circumferential direction of the roll is shorter than the distance between the contact position and the abutment position in the circumferential direction.

Images