Drying device

Abstract

To provide a drying device capable of quickly detecting conveyance failure of a medium.SOLUTION: A drying device 1 includes: a conveyance device 3 for conveying a medium; a heating device 5 for drying the medium conveyed by the conveyance device 3 under a high temperature environment; a roller pair 7 including a drive roller 21 rotating by being driven, and a driven roller 23 rotating following the drive roller 21, and for conveying the medium which has passed the heating device 5; a drive roller rotation detection part 51 for detecting the rotation of the drive roller 21; a driven roller rotation detection part 41 for detecting the rotation of the driven roller 23; and a control part 51 which stops the heating device 5 in the case where the rotation of the drive roller 21 is detected by the drive roller rotation detection part 51 and the rotation period of the driven roller 23 acquired from the detection result of the driven roller rotation detection part 41 becomes longer than a constant period.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a drying device that dries a medium on which an image is formed with ink in a high-temperature environment while transporting the medium. [Background technology]

[0002] An image forming system including an inkjet image forming apparatus is provided with a drying device that dries an image (ink) formed on a medium. In such drying devices, a reflective or transmissive optical sensor is often used to detect a transport failure of the medium. The drying device described in Patent Document 1 has a reflective optical sensor disposed upstream of a drying chamber, and a transmissive optical sensor disposed within the drying chamber. The upstream optical sensor detects the delivery of a sheet (medium) into the drying chamber, and the downstream optical sensor detects the delivery of the sheet from the drying chamber. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2022-147335 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in drying devices such as that described in Patent Document 1, if a media transport problem occurs after the leading edge of a long medium is discharged from the drying chamber and the medium remains within the drying chamber, there is a problem in that the media transport problem cannot be detected quickly.

[0005] SUMMARY OF THE PRESENT DISCLOSURE In consideration of the above circumstances, an object of the present invention is to provide a drying device that is capable of quickly detecting a medium transport failure. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the drying device of the present invention is characterized in that it comprises a transport device that transports a medium on which an image is formed with ink along a predetermined transport direction; a heating device that dries the ink on the medium transported by the transport device in a high-temperature environment; a transport roller pair that is arranged downstream of the heating device in the transport direction and includes a drive roller that rotates when driven and a driven roller that rotates following the drive roller, transporting the medium that has passed through the heating device; a drive roller rotation detection unit that detects the rotation of the drive roller; a driven roller rotation detection unit that detects the rotation of the driven roller; and a control unit that stops the heating device when the rotation of the drive roller is detected by the drive roller rotation detection unit and the rotation period of the driven roller obtained from the detection result of the driven roller rotation detection unit becomes longer than a certain period.

[0007] In the present invention, the certain period may be determined based on a time period during which a defect occurs in the medium due to the heating device.

[0008] In the present invention, the driven roller rotation detection unit may be a reflective sensor having an emission unit that emits light toward an end of the rotation shaft of the driven roller, and a light receiving unit that receives light emitted from the emission unit and reflected at the end.

[0009] In the present invention, the end of the rotation shaft of the driven roller may have a flat surface parallel to the axial direction of the rotation shaft and a curved surface along the circumferential direction of the rotation shaft, and the driven roller rotation detection unit may detect the rotation of the driven roller by receiving light emitted from the emission unit and reflected by the flat surface with the light receiving unit.

[0010] In the present invention, the flat surface may have a higher gloss than the curved surface.

[0011] In the present invention, the ends of the rotating shaft of the driven roller may be formed at equal intervals in the circumferential direction of the rotating shaft, and may be formed into a polygonal cross section having a plurality of flat surfaces parallel to the axial direction of the rotating shaft, and the driven roller rotation detection unit may detect the rotation of the driven roller by receiving light emitted from the emission unit and reflected by the plurality of flat surfaces with the light receiving unit. Effect of the Invention

[0012] According to the present invention, by detecting the rotation of the driven roller that rotates in response to the medium, it is possible to accurately and quickly detect a stop in medium transport and a decrease in the medium transport speed. [Brief description of the drawings]

[0013] [Figure 1] 1 is a front view showing a drying device according to an embodiment of the present invention; [Figure 2A] 4 is a diagram showing a pair of transport rollers and a rotation detection sensor (when an ON signal is output) in the drying device according to one embodiment of the present invention. FIG. [Figure 2B] 4 is a diagram showing a pair of transport rollers and a rotation detection sensor (when an off signal is output) in the drying device according to one embodiment of the present invention. FIG. [Figure 2C] FIG. 4 is a diagram showing an example of an output waveform of a rotation detection sensor in the drying device according to one embodiment of the present invention. [Figure 3A] 10 is a diagram illustrating a pair of transport rollers and a rotation detection sensor (when an OFF signal is output) when transport of a medium is stopped in a drying device according to an embodiment of the present invention. FIG. [Figure 3B] 11 is a diagram showing an example of an output waveform of a rotation detection sensor when medium transport is stopped in the drying device according to the embodiment of the present invention. FIG. [Figure 4A] 10 is a diagram illustrating the pair of transport rollers and the rotation detection sensor (when an ON signal is output) when the medium transport speed is reduced in the drying device according to the embodiment of the present invention. FIG. [Figure 4B]13 is a diagram illustrating the pair of transport rollers and the rotation detection sensor (when an OFF signal is output) when the medium transport speed is reduced in the drying device according to the embodiment of the present invention. FIG. [Figure 4C] 11 is a diagram showing an example of an output waveform of a rotation detection sensor when a medium transport speed decreases in the drying device according to the embodiment of the present invention. FIG. [Figure 5A] 13 is a diagram illustrating a pair of transport rollers and a rotation detection sensor (when an ON signal is output) in a modified example of a drying device according to an embodiment of the present invention. FIG. [Figure 5B] 13 is a diagram illustrating a pair of transport rollers and a rotation detection sensor (when an OFF signal is output) in a modified example of a drying device according to an embodiment of the present invention. FIG. [Figure 5C] FIG. 11 is a diagram showing an example of an output waveform of a rotation detection sensor in a modified example of the drying device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, a drying device according to an embodiment of the present invention will be described with reference to the drawings.

[0015] First, the overall configuration of the drying device 1 will be described with reference to Fig. 1. Fig. 1 is a front view showing the inside of the drying device 1. The drying device 1 includes a transport device 3 that transports a medium on which an image has been formed by an inkjet method in a transport direction (direction from right to left in Fig. 1), a heating device 5 that dries the ink on the medium transported by the transport device 3 in a high-temperature environment, and a transport roller pair 7 that transports the medium that has passed through the heating device 5.

[0016] First, a description will be given of the conveying device 3. The conveying device 3 includes a conveying belt 11 that conveys the medium, a conveying plate 13 that supports the conveying belt 11, and a suction device 15 that attracts the medium to the conveying belt 11.

[0017] The conveyor belt 11 is an endless belt, and has many through holes formed on the entire surface thereof, penetrating in the thickness direction. The conveyor belt 11 is wound around a drive roller 17 and a driven roller 19. The drive roller 17 is driven to rotate by a motor (not shown), causing the conveyor belt 11 to circulate in a counterclockwise direction in FIG. 1. The outer surface of the conveyor belt 11 along the upper track becomes the conveying surface along which the medium (cut sheets, long sheets, etc.) is conveyed.

[0018] The conveying plate 13 contacts the inner peripheral surface (the surface behind the conveying surface) of the conveying belt 11 running on the upper track to support the conveying belt 11. When the conveying belt 11 runs, the inner peripheral surface of the conveying belt 11 slides along the upper surface of the conveying plate 13. The conveying plate 13 has a large number of through holes formed all over the surface, penetrating in the thickness direction.

[0019] The suction device 15 is disposed in a hollow portion of the conveyor belt 11. When the suction device 15 is driven, air is sucked in through the through holes of the conveyor belt 11 and the through holes of the conveyor plate 13, and the medium is attracted to the conveying surface of the conveyor belt 11.

[0020] Next, the heating device 5 will be described. The heating device 5 is disposed above the transport device 3, and includes a plurality of blower fans and a heater unit (both not shown). The blower fan takes in air and generates a downward airflow. The heater unit heats the generated airflow. The heating device 5 is electrically connected to a control unit 51.

[0021] Next, the transport roller pair 7 will be described with reference to Fig. 1 as well as Fig. 2A, Fig. 2B, and Fig. 2C. Fig. 2A and Fig. 2B are diagrams showing the transport roller pair 7 and the rotation detection sensor 41, and Fig. 2C is a diagram showing an example of an output waveform of the rotation detection sensor 41.

[0022] 1, the transport roller pair 7 is disposed downstream of the heating device 5 in the medium transport direction. The transport roller pair 7 includes a drive roller 21 and a driven roller 23. The drive roller 21 is connected to a motor 25 and is driven to rotate by the motor 25. The motor 25 is electrically connected to the control unit 51.

[0023] The driven roller 23 rotates by being driven by the rotation of the driving roller 21 or the medium transported by the rotation of the driving roller 21. As shown in Figures 2A and 2B, an end 31 of the rotation shaft of the driven roller 23 is formed in a D-cut shape. That is, the end 31 has a flat surface 31a parallel to the rotation shaft and a curved surface 31b along the circumferential direction of the rotation shaft.

[0024] The rotation of the driven roller 23 is detected by a rotation detection sensor 41. The rotation detection sensor 41 is an optical sensor having an emission part that emits light and a light receiving part that receives light. The rotation detection sensor 41 is disposed below the end 31 of the rotation shaft of the driven roller 23 so that the light emitted from the emission part is incident on the end 31 of the rotation shaft of the driven roller 23. The rotation detection sensor 41 is electrically connected to a control unit 51 (see FIG. 1 ), and transmits an ON signal or OFF signal to the control unit 51 based on the detection result.

[0025] That is, as shown in Fig. 2A, when the light emitted from the emission unit is incident on the flat surface 31a approximately perpendicularly, the light is reflected on the flat surface 31a approximately perpendicularly and is received by the light receiving unit. Then, the rotation detection sensor 41 outputs an ON signal. On the other hand, as shown in Fig. 2B, when the light emitted from the emission unit is not incident on the flat surface 31a approximately perpendicularly or is incident on the curved surface 31b, the light is reflected in a direction different from the light receiving unit and is not received by the light receiving unit, so the rotation detection sensor 41 outputs an OFF signal. Note that the light receiving unit of the rotation detection sensor 41 can receive not only light reflected perpendicularly on the flat surface 31a, but also light reflected at a predetermined angle on the flat surface 31a.

[0026] As a result, each time driven roller 23 rotates once, a "1" indicating an ON signal and a "0" indicating an OFF signal appear in the output waveform of rotation detection sensor 41. Therefore, when driven roller 23 rotates, "1" and "0" appear at a constant cycle P, as shown in FIG.

[0027] 1, a medium detection sensor 43 is disposed downstream in the transport direction from the transport roller pair 7. The medium detection sensor 43 is an optical sensor having an emission section that emits light and a light receiving section that receives light emitted from the emission section and reflected by the medium transported by the transport roller pair 7. The medium detection sensor 43 is electrically connected to the control section 51, and transmits an on signal or an off signal to the control section 51 based on the detection result.

[0028] Next, the control unit 51 will be described with reference to Fig. 1. The control unit 51 controls the heating device 5 (blower fan, heater unit) to drive or stop driving the heating device 5.

[0029] The control unit 51 drives or stops the driving of the motor 25 that rotates the drive roller 21 of the transport roller pair 7. Furthermore, an on signal or an off signal is input to the control unit 51 from the rotation detection sensor 41. The control unit 51 calculates the rotation period of the driven roller 19 based on the input signal. Note that the control unit 51 stores in advance a reference rotation period of the driven roller 19 when the medium is normally transported by the transport roller pair 7. The reference rotation period is determined based on the time at which a malfunction occurs in the medium due to the heating device 5. Furthermore, an on signal or an off signal is input to the control unit 51 from the medium detection sensor 43.

[0030] The drying operation of the drying device 1 having the above configuration will be described with reference to Fig. 1, Fig. 3A, Fig. 3B, Fig. 4A, Fig. 4B, and Fig. 4C. Fig. 3A shows the pair of transport rollers 7 and the rotation detection sensor 41 when the medium transport is stopped, and Fig. 3B shows an example of an output waveform of the rotation detection sensor 41 when the medium transport is stopped. Figs. 4A and 4B show the pair of transport rollers 7 and the rotation detection sensor 41 when the medium transport speed is reduced, and Fig. 4C shows an example of an output waveform of the rotation detection sensor 41 when the medium transport speed is reduced.

[0031] In the conveying device 3, the driving roller 17 is driven to rotate and the conveying belt 11 runs. Thereafter, the medium on which an image has been formed by the inkjet method is conveyed to the conveying surface of the conveying belt 11. In addition, the suction device 15 is driven. As a result, air is sucked into the through holes of the conveying belt 11 and the through holes of the conveying plate 13 as described above, and a negative pressure is created above the conveying surface of the conveying belt 11. Then, the medium is attracted to the conveying surface. In this way, the medium is conveyed along the conveying direction while being attracted to the conveying surface of the conveying belt 11.

[0032] Furthermore, the control unit 51 drives the heating device 5. As a result, air taken in by the blower fan is blown downward. The blown air is heated by the heater unit, and the heated air is blown onto the medium being transported by the transport device 3. This dries the ink on the medium. The medium with the dried ink is transported from the transport belt 11 to the transport roller pair 7, and is transported downstream by the transport roller pair 7. That is, the motor 25 is driven to rotate the drive roller 21, and the driven roller 23 rotates in response to the medium being transported by the rotation of the drive roller 21. The rotation of the driven roller 23 is detected by the rotation detection sensor 41. The detection result of the rotation detection sensor 41 is sent to the control unit 51.

[0033] The control unit 51 calculates the rotation period of the driven roller 23 based on the detection result of the rotation detection sensor 41. The control unit 51 compares the calculated rotation period with a stored reference rotation period P. Furthermore, the control unit 51 determines whether the motor 25 that drives the drive roller 21 is driven. If the control unit 51 determines that the calculated rotation period is longer than the reference rotation period P and that the motor 25 is driven, it stops driving the heating device 5.

[0034] That is, as shown in Fig. 3B, when the output waveform of rotation detection sensor 41 shows a "1" indicating an on signal followed by a "0" indicating an off signal, control unit 51 determines that driven roller 23 is not rotating. As shown in Fig. 3A, when driven roller 23 is not rotating even though drive roller 21 is rotating, it is determined that driven roller 23 is not rotating driven by the medium, and medium S is not being transported. In this case, medium S remains inside heating device 5, so driving of heating device 5 is stopped.

[0035] The case where the calculated rotation period is longer than the reference rotation period P (the rotation period during normal conveying operation) includes the above-mentioned case where "1" indicating an ON signal appears followed by "0" indicating an OFF signal. Alternatively, the output waveform of the rotation detection sensor 41 may continue at "1". In this case, the rotation of the driven roller 23 stops with the light emitted from the rotation detection sensor 41 being incident on the flat surface 31a of the end 31 of the rotation shaft of the driven roller 23 substantially perpendicularly. This case is also included in the case where the calculated rotation period is longer than the reference rotation period P.

[0036] In this way, the control unit 51 is an example of a drive roller rotation detection unit that detects the rotation of the drive roller 21 in the present invention, and the rotation detection sensor 41 is an example of a driven roller rotation detection unit that detects the rotation of the driven roller 23.

[0037] 4C, when the control unit 51 determines that the rotation period P1 of the rotation detection sensor 41 is longer than the reference rotation period P and that the motor 25 is driving, the control unit 51 stops driving the heating device 5. That is, when the rotation period P1 of the rotation detection sensor 41 is longer than the reference rotation period P, as shown in FIGS. 4A and 4B, even if the drive roller 21 is rotating, the rotation speed of the driven roller 23 that rotates following the medium S is slow, and it can be determined that the transport speed of the medium S is slow. In this case, for a long medium S, the time required for the medium S to be transported inside the heating device 5 becomes long, so the control unit 51 stops driving the heating device 5.

[0038] As is clear from the above description, the drying device 1 of the present invention can accurately and quickly detect a stop in medium transport and a decrease in the medium transport speed by detecting the rotation of the driven roller 23 that rotates following the medium. Furthermore, when such a transport failure is detected, the heating device 5 is quickly stopped, thereby preventing the medium from remaining in the heating device 5 at a high temperature.

[0039] In addition, the end 31 of the driven roller 23 may be processed so that the glossiness of the flat surface 31a is higher than that of the curved surface 31b. For example, a paint with a high glossiness may be applied to the flat surface 31a, and a paint with a lower glossiness may be applied to the curved surface 31b. In this case, the difference in the amount of light received by the light receiving unit of the rotation detection sensor 41 between the flat surface 31a and the curved surface 31b becomes large, so that the rotation of the driven roller 23 can be grasped more accurately.

[0040] Next, a modified example of the driven roller 23 will be described with reference to Fig. 5A and Fig. 5B. In this modified example, as shown in Fig. 5A and Fig. 5B, the end 31 of the rotation shaft of the driven roller 23 is formed in a polygonal shape (square in this example) in a cross-sectional view. That is, four flat surfaces 31a are formed at equal central angles along the circumferential direction on the end 31. In this case, as shown in Fig. 4A, when the light emitted from the rotation detection sensor 41 is reflected approximately perpendicularly by the flat surface 31a, the rotation detection sensor 41 outputs an ON signal, and as shown in Fig. 4B, when the light emitted from the rotation detection sensor 41 is not reflected approximately perpendicularly by the flat surface 31a, the rotation detection sensor 41 outputs an OFF signal.

[0041] In this example, as shown in Fig. 5C, an ON signal is output four times for each rotation of the driven roller 23, so the rotation period P2 is ¼ of the reference rotation period P. Therefore, medium transport defects determined from the rotation period can be detected more quickly.

[0042] In this embodiment, the rotation detection sensor 41 receives light reflected by the D-cut flat surface 31a at the end 31 of the rotation shaft of the driven roller 23. However, a pulse plate may be provided on the rotation shaft of the driven roller 23, and the rotation detection sensor 41 may receive light reflected by the reflective surface of the pulse plate. However, by receiving light reflected by the D-cut flat surface 31a as in this embodiment, the rotation detection sensor 41 can be installed in a relatively narrow space within the length range of the rotation shaft of the driven roller 23.

[0043] Although the present invention has been described with respect to a specific embodiment, the present invention is not limited to the above embodiment. The above embodiment may be variously changed, substituted, or modified without departing from the scope and spirit of the present invention, and the claims include all embodiments that may be included within the scope of the technical idea. [Explanation of symbols]

[0044] 1 Drying device 3. Conveyor 5 Heating device 7 Transport roller pair 21 Drive roller 23 Driven roller 25 Motor 41 Rotation detection sensor (driven roller rotation detection part) 51 Control unit (driving roller rotation detection unit)

Claims

1. a conveying device that conveys a medium on which an image is formed with ink along a predetermined conveying direction; a heating device that dries the ink on the medium transported by the transport device in a high-temperature environment; a conveying roller pair that is disposed downstream of the heating device in the conveying direction and includes a driving roller that is driven to rotate and a driven roller that is driven to rotate by the driving roller, and conveys the medium that has passed through the heating device; A drive roller rotation detection unit that detects the rotation of the drive roller; a driven roller rotation detection unit that detects rotation of the driven roller; a control unit that stops the heating device when the rotation of the drive roller is detected by the drive roller rotation detection unit and the rotation period of the driven roller obtained from the detection result of the driven roller rotation detection unit becomes longer than a certain period.

2. 2. The drying device according to claim 1, wherein the fixed period is determined based on a time period during which the medium is damaged by the heating device.

3. The drying device according to claim 1, characterized in that the driven roller rotation detection unit is a reflective sensor having an emission unit that emits light toward an end of the rotation shaft of the driven roller, and a light receiving unit that receives light emitted from the emission unit and reflected at the end.

4. The end of the rotation shaft of the driven roller has a flat surface parallel to the axial direction of the rotation shaft and a curved surface along the circumferential direction of the rotation shaft, The drying device according to claim 3 , wherein the driven roller rotation detection unit detects the rotation of the driven roller by receiving, with the light receiving unit, the light emitted from the emitting unit and reflected by the flat surface.

5. 5. The drying device according to claim 4, wherein the flat surface has a higher gloss than the curved surface.

6. The end of the rotating shaft of the driven roller is formed at equal intervals in the circumferential direction of the rotating shaft, has a plurality of flat surfaces parallel to the axial direction of the rotating shaft, and has a polygonal cross section; The drying device according to claim 3 , wherein the driven roller rotation detection unit detects the rotation of the driven roller by receiving light emitted from the emission unit and reflected by the plurality of flat surfaces with the light receiving unit.

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