Conveying device, recording device

Abstract

To provide a conveying device capable of suppressing sheet conveyance failure.SOLUTION: The conveying device includes: a conveying section that conveys a sheet while applying tension to the sheet along a sheet conveying direction; and a tension detection section that detects tension of the sheet being conveyed to the conveying section. The tension detection section is configured to be switchable between a first mode capable of detecting tension of a value between a first lower limit value TL1 and a first upper limit value TU1, and a second mode capable of detecting tension between a second lower limit value TL2 greater than the first lower limit value TL1 and a second upper limit value TU2 greater than the first upper limit value TU1. The conveying device includes a control section that switches between the first mode and the second mode based on the tension detected by the tension detection section.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to a transport device and a recording device equipped with the transport device. [Background technology]

[0002] Conventionally, a conveying device that conveys a sheet as a conveying medium has been known that conveys the sheet while applying tension to the sheet along the conveying direction. Patent Document 1 discloses a configuration in which the sheet conveying speed is controlled based on the tension detected by a tension detection unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-145499 Summary of the Invention [Problem to be solved by the invention]

[0004] Various types of conveying media, such as film, plain paper, and cardboard, can be used as sheets conveyed by a conveying device. However, there is a large difference in the tension detection range between film, which must be conveyed with low tension to prevent stretching, and cardboard, which must be conveyed with high tension to prevent slack. Therefore, if a common detection circuit is used to detect the tension of multiple types of sheets, the wide tension detection range results in low resolution, making it difficult to control the tension with high precision. Low-precision tension control can lead to improper sheet conveyance, such as stretching the sheet in the conveying direction or sagging, resulting in jamming.

[0005] In order to solve the above-mentioned problems, an object of the present invention is to provide a conveying device that can suppress sheet conveyance failures. [Means for solving the problem]

[0006] In order to achieve the above object, the conveying device of the present invention comprises: a conveying unit that conveys the sheet while applying tension to the sheet along the sheet conveying direction; a tension detection unit that detects the tension of the sheet being conveyed to the conveying unit; a tension adjusting means for adjusting the tension of the sheet conveyed by the conveying section; Equipped with the tension detection unit is configured to be switchable between a first mode capable of detecting tension between a first lower limit value and a first upper limit value, and a second mode capable of detecting tension between a second lower limit value greater than the first lower limit value and a second upper limit value greater than the first upper limit value, Sheet type and The apparatus is characterized by including a control unit that switches between the first mode and the second mode based on the tension detected by the tension detection unit. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a conveying device that can suppress sheet conveyance failures. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 2 is a schematic cross-sectional view showing the configuration of the recording apparatus of the first embodiment during recording. [Figure 2] FIG. 2 is a schematic cross-sectional view showing the configuration of the recording apparatus of the first embodiment during cleaning. [Figure 3] FIG. 1 is a block diagram of a recording apparatus according to a first embodiment. [Figure 4] FIG. 2 is a block diagram of a tension control configuration according to the first embodiment. [Figure 5] FIG. 2 is a block diagram of a switching unit according to the first embodiment. [Figure 6] FIG. 4 is a tension detection characteristic diagram of the first embodiment. [Figure 7] 4 is a flowchart of tension control in the first embodiment. [Figure 8] 4 is a flowchart of tension control in the first embodiment. [Figure 9]FIG. 10 is a tension detection characteristic diagram of the second embodiment. [Figure 10] 10 is a flowchart of tension control in the second embodiment. [Figure 11] 10 is a flowchart of tension control in the second embodiment. [Figure 12] FIG. 11 is a tension detection characteristic diagram of the third embodiment. [Figure 13] 10 is a flowchart of tension control in the third embodiment. [Figure 14] 10 is a flowchart of tension control in the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] The following describes in detail exemplary embodiments of the present invention with reference to the drawings. The dimensions, materials, shapes, and relative positions of the components described in the embodiments may be changed as appropriate depending on the configuration and various conditions of the device to which the invention is applied. In other words, the scope of the present invention is not limited to the following embodiments.

[0010] The conveying device of the present invention can be applied to, for example, a recording device that records an image on a sheet as a recording medium while conveying the sheet. Hereinafter, a high-speed line printer that uses a continuous sheet wound in a roll will be described as an example of a recording device to which the present invention is applied. This type of recording device is suitable for mass printing in print laboratories, for example. However, the application of the present invention is not limited to high-speed line printers, and can be applied to various recording devices and other devices that convey sheets.

[0011] Example 1 (Recording device) First, a schematic configuration of a recording device 101 according to a first embodiment will be described with reference to Fig. 1. Fig. 1 is a schematic cross-sectional view showing the internal configuration of the recording device 101. In the following description, the up-down direction of the paper in Fig. 1 is assumed to be the up-down direction of the recording device 101. In the first embodiment, a sheet as a recording medium (conveying medium) is conveyed from right to left on the paper in Fig. 1, with the direction from the front to the back of the paper being the sheet width direction.

[0012] Inside the main body of the recording apparatus 101 of the first embodiment, a sheet supply unit 102, a sheet identification sensor 103, a first conveying roller pair 104, a meandering correction unit 105, a tension detection unit 106, and a recording unit 107 are provided in this order along a sheet conveying path S. Furthermore, downstream of the recording unit 107 in the sheet conveying direction, a post-processing unit 109, a second conveying roller pair 110, and a sheet recovery unit 111 are provided in this order along the sheet conveying path S. In addition to the above-mentioned units, the recording apparatus 101 also includes a head cleaning unit 108, a controller unit 301, and a print engine unit 302. In FIG. 1, the sheet conveying path S is indicated by a solid line. During a recording operation by the recording apparatus 101, a sheet is conveyed along the conveying path S while undergoing predetermined processing in each unit.

[0013] The sheet supply unit 102 is a unit for holding and supplying a continuous sheet wound in a roll. The sheet supply unit 102 is configured to store a roll 113 and pull out and supply a sheet. The number of rolls that can be stored is not limited to one, and the unit may store two, three, or more rolls and selectively pull out and supply a sheet. Also, the sheet is not limited to being wound in a roll, as long as it is a continuous sheet. For example, a continuous sheet with perforations at each unit length may be folded back at each perforation and stacked and stored in the sheet supply unit 102.

[0014] The sheet identification sensor 103 is used to identify a sheet (transport medium). In the first embodiment, an identification sensor is used as a means for identifying the sheet, but the sheet may also be identified by a human being who performs the identification and inputs the identification result into the operation unit 119.

[0015] The first conveying roller pair 104 is a conveying unit that feeds the sheet to a meandering correction unit 105, a tension detection unit 106, a recording unit 107, and a post-processing unit 109, which are arranged in the following order along the sheet conveying path S. The first conveying roller pair 104 is also a tension applying unit that applies sheet tension between the first conveying roller pair 104 and the second conveying roller pair 110. The first conveying roller pair 104 rotates by driving a motor (not shown) to convey the sheet with tension.

[0016] The meandering correction unit 105 is a unit for correcting meandering in the sheet width direction when the sheet is conveyed under tension. The meandering correction unit 105 is configured to include a meandering correction roller 105a and a meandering detection sensor (not shown) that detects meandering of the sheet. The meandering correction roller 105a can change its inclination relative to the sheet using a motor (not shown), and corrects meandering of the sheet based on measurements by the meandering detection sensor. At this time, the sheet is wrapped around the meandering correction roller 105a, thereby improving the meandering correction function.

[0017] The tension detection unit 106 is a unit for detecting tension during tension conveyance between the first conveyor roller pair 104 and the second conveyor roller pair 110. As the tension detection unit 106, for example, a known tension detection means that converts tension into a load and outputs the load as an electrical signal can be used as appropriate. The tension detection unit can also be of a known detection type, such as a differential transformer type or a strain gauge type, depending on the configuration of the conveyor unit.

[0018] The recording unit 107 is a sheet processing unit that performs recording processing on the conveyed sheet from above using a recording head 114 to form an image on the sheet. The conveying path S in the recording unit 107 is formed by guide rollers 115 that are arranged in an arc shape that is convex upward, and a certain tension is applied to the sheet, thereby ensuring a clearance between the sheet and the recording head 114.

[0019] In the first embodiment, multiple print heads 114 are arranged in an arc shape following the transport path S (along the transport direction). In the first embodiment, four line-type print heads corresponding to four colors, Bk (black), Y (yellow), M (magenta), and C (cyan), are provided as print heads 114. Note that the number of colors and the number of print heads 114 are not limited to four. The multiple print heads 114 are integrally held by a head holder 116. The head holder 116 is configured to be movable in the vertical direction so that the clearance between the sheet and the print heads 114 can be changed. As the inkjet method, a method using a heating element, a piezoelectric element, an electrostatic element, a MEMS element, or the like can be adopted. Ink of each color is supplied to the print head 114 from an ink tank (not shown) via an ink tube.

[0020] The head cleaning unit 108 is composed of a cleaning unit (not shown) that cleans the ink ejection surface of the recording head 114, and a cap unit 117 that moisturizes the ink ejection surface of the recording head 114. The cleaning unit is not limited to any particular unit and may be selected from a wide range of options depending on the characteristics of the ink used, the recording time, and the interval, such as wiping with an elastic blade such as urethane, or suction with a strip-shaped cloth or nonwoven fabric or rubber suction nozzle.

[0021] The cap unit 117 is a rubber member molded in a tub shape that covers the ejection nozzle area of ​​the ink ejection surface. By bringing the ink into contact with the outside of the area, contact between the outside air and the ejection nozzle is reduced, thereby preventing drying. The form is not limited, and a sealed space may be created by arranging rubber ribs or the like on a plate-shaped member and bringing the ribs into contact. Also, in order to make the pressure on the ejection nozzle equal to atmospheric pressure, an air communication passage may be provided within a range that does not affect the prevention of drying. Furthermore, a configuration may be adopted in which negative pressure is applied to the sealed space to suck ink out of the nozzle. In order to improve the moisture retention ability, a configuration may be adopted in which liquid is supplied into the cap to increase humidity.

[0022] A plurality of cleaning units corresponding to a plurality of recording heads 114 and a cap unit 117 are arranged in an arc shape and are integrally held by a cleaning holder 118. The head cleaning unit 108 is configured to be slidable between a facing position facing the recording heads 114 and a retracted position retracted from the position facing the recording heads 114.

[0023] During a recording operation on a sheet, the head cleaning unit 108 is located in the retracted position shown in FIG. 1. On the other hand, during a cleaning operation of the recording head 114, the head cleaning unit 108 is located in the opposing position. FIG. 2 is a schematic diagram showing the internal configuration of the recording device 101 when the head cleaning unit 108 is located in the opposing position. When the head cleaning unit 108 is located in the opposing position, each cap unit 117 is located directly below the corresponding recording head 114. When the head cleaning unit 108 slides from the retracted position (position in FIG. 1) to the opposing position (position in FIG. 2), the head holder 116 is first raised, the head cleaning unit 108 is slid, and then the head holder 116 is lowered. Note that the head cleaning unit 108 is not limited to being composed of a cleaning unit and a cap unit 117, and may be composed of only either the cleaning unit or the cap unit 117. Furthermore, the sliding direction of the head cleaning unit 108 may be along the sheet conveyance direction or the sheet width direction.

[0024] The post-processing unit 109 is a unit that reduces the liquid content contained in the ink applied onto the sheet by the recording unit 107 and improves the fixation of the ink to the sheet. The post-processing unit 109 is composed of a drying unit 121, a fixing unit 122, and a cooling unit 123.

[0025] The drying unit 121 heats the printed sheet to dry the applied ink. Inside the drying unit 121, hot air is applied to at least the upper surface of the sheet passing through to dry the ink-applied surface. Note that the drying method may be a combination of a method of applying hot air, a method of irradiating the sheet surface with electromagnetic waves (ultraviolet rays, infrared rays, etc.), and a conductive heat transfer method using contact with a heating element.

[0026] The fixing unit 122 applies a predetermined amount of heat to the sheet dried in the drying unit 121, softening and melting the ink, thereby improving fixability to the sheet. Inside the fixing unit 122, hot air equivalent to or greater than the heat amount of the drying unit 121 is applied to the sheet passing through from at least the upper surface side, thereby fixing the image (ink) to the ink-applied surface. Note that the fixing method is not limited to the method of applying hot air, but may also be a method of irradiating the sheet surface with electromagnetic waves (ultraviolet rays, infrared rays, etc.), a method of clamping the sheet between heating elements and applying heat and pressure, or a combination of these.

[0027] The cooling unit 123 cools the sheet on which the image has been fixed by the fixing unit 122, solidifying the softened ink and suppressing the amount of change in the sheet temperature in downstream processes of the recording device. Inside the cooling unit 123, air at a temperature lower than that of the sheet is blown onto at least the upper surface of the passing sheet to cool the ink application surface. Note that the cooling method is not limited to the method of blowing air, and may also be a conductive heat transfer method using contact with a heat dissipation member or a combination of these.

[0028] The second conveying roller pair 110 is a unit that conveys the sheet while applying tension to the sheet together with the first conveying roller pair 104, and adjusts the tension of the sheet. The roller pair 110 is rotated by being driven by a motor (not shown). In the first embodiment, the print engine unit 302 adjusts the tension by controlling the speed of the second conveying roller pair 110 in accordance with the tension detected by the tension detection unit 106. As described above, in the first embodiment, the conveying unit that conveys the sheet while applying tension to the sheet along the sheet conveying direction includes the first conveying roller pair 104 and the second conveying roller pair 110. The first conveying roller pair 104 and the second conveying roller pair 110 also function as tension adjustment means that can adjust the tension of the sheet.

[0029] The sheet tension adjusting means is not limited to the above-described configuration. For example, a clutch may be provided as an additional configuration for adjusting the sheet tension. A mechanism may be added in which the torque of the clutch is controlled based on the detection result of the tension detection unit 106, thereby adjusting the sheet tension. In this case, two methods are provided: a speed control method for controlling the roller speed of the second conveying roller pair, and a torque control method for controlling the torque value transmitted from the clutch. Depending on the purpose, the tension control methods can be switched or both can be used simultaneously.

[0030] The sheet recovery unit 111 is a unit for winding the recorded sheet onto a core. The number of recoverable rolls is not limited to one, and the unit may have two or three or more cores, and may be configured to selectively switch between them to recover the sheet. Depending on the content of the post-recording processing, the continuous sheet may be cut using a cutter and the cut sheets may be stacked, rather than being wound onto a core.

[0031] The controller unit 301 is a unit that controls the various parts of the entire recording device 101. The controller unit 301 has a CPU, a storage device, a controller equipped with various control units, an external interface (I / F), and an operation unit 308 through which the user performs input and output. The operation of the recording device 101 is controlled based on commands from the controller or a host device 120 such as a host computer connected to the controller via an external interface.

[0032] The print engine unit 302 is a unit that mainly controls the conveying unit and the recording unit of the recording device 101. Based on the detection result of the tension detection unit 106, the print engine unit 302 drives the first conveying roller pair 104 and the second conveying roller pair 110 to control the sheet conveying speed and tension.

[0033] (Control configuration of the entire recording device) 3 is a block diagram showing the control configuration of the recording device 101. The control section of the recording device 101 is mainly composed of a controller unit 301 that controls the entire recording device 101, and a print engine unit 302 that controls the recording section. A print controller 311 controls various mechanisms of the print engine unit 302 according to instructions from a main controller 304 of the controller unit 301.

[0034] In the first embodiment, the controller unit 301 includes an external I / F 303, a main controller 304, a ROM 305, a RAM 306, a print engine I / F 307, an operation unit 308, and an image processing unit 309. The print engine unit 302 includes a controller I / F 310, a print controller 311, a ROM 312, a RAM 313, and an image processing controller 314. The print engine unit 302 further includes a scanner control unit 315, a transport control unit 316, an ink supply control unit 317, a head carriage control unit 318, a head maintenance control unit 319, and a head I / F 320.

[0035] In the controller unit 301, a main controller 3 configured by a CPU Main controller 304 controls the entire recording device 101 using RAM 306 as a work area in accordance with programs and various parameters stored in ROM 305. For example, when a print job is input from an external host device via external I / F 303, image processing unit 309 performs predetermined image processing on the received image data in accordance with instructions from main controller 304. Then, main controller 304 transmits the processed image data to print engine unit 302 via print engine I / F 307.

[0036] The means by which the recording device 101 acquires image data is not limited to those described above. For example, image data may be acquired from another host device via wireless or wired communication. Furthermore, image data may be acquired from an image reading device connected to the recording device 101 as an external device or an image reading device connected inside the device, or from an external storage device (such as a USB memory) connected to the recording device 101. In this way, the means by which image data is acquired is not limited to communication means or a connected external device.

[0037] The operation unit 308 is used to input and output data to and from the recording device, and can be used to instruct operations such as copying and scanning, set the recording mode, and recognize information about the recording device.

[0038] In the print engine unit 302, a print controller 311, which is configured with a CPU and the like, controls various mechanisms of the recording unit in accordance with programs and various parameters stored in a ROM 312, using a RAM 313 as a work area. When various commands and image data are received via a controller I / F 310, the print controller 311 temporarily stores them in the RAM 313. The print controller 311 then causes an image processing controller 314 to convert the stored image data into recording data so that the recording head 114 can use it for recording operations. Once the recording data is generated, the print controller 311 then causes the recording head 114 to perform a recording operation based on the recording data via a head I / F 320. At this time, the print controller 311 drives a conveyance unit of the recording device 101 via a conveyance control unit 316 to convey a sheet. In accordance with instructions from the print controller 311, the recording head 114 performs a recording operation in conjunction with the sheet conveyance operation, and recording processing is performed.

[0039] A head carriage control unit 318 changes the orientation and position of the print head 114 depending on the operating state, such as the maintenance state or printing state, of the printing apparatus 101. An ink supply control unit 317 controls the pressure and density of ink supplied to the print head 114 so that they fall within appropriate ranges. A head maintenance control unit 319 controls the operation of the cap unit and wiping unit in the maintenance unit when performing maintenance operations on the print head 114.

[0040] The control configuration of the recording device 101 is not limited to the above configuration. For example, the print controller 311 may control the mechanisms of the recording units, or each control unit may have a CPU, ROM, RAM, etc., and the print controller 311 may control only the entire device.

[0041] (Tension control configuration) 4 is a block diagram of the tension control configuration of the recording apparatus 101 in the first embodiment. The transport control unit 316 performs transport control in accordance with commands from the print controller 311 via a transport control I / F 401. The transport control unit 316 includes the transport control I / F 401, a transport unit 402, an identification unit 403, a tension detection unit 106, a switching unit 405, a CPU 406, a ROM 411, and a RAM 412.

[0042] The CPU 406 includes a switching control unit 407, a comparison unit 408, a calculation unit 409, and a conveyance speed control unit 410. The conveyance control unit 316 controls the conveyance speed of the conveyance unit 402 using the conveyance speed control unit 410 of the CPU 406.

[0043] The ROM 411 stores a target tension Tt and a switching tension Ts for each type of sheet. The target tension Tt is the ideal tension value during sheet transport. The transport control unit 316 controls the sheet tension each time so that it approaches the target tension Tt. The switching tension Ts is a tension threshold used when switching the sheet tension detection range.

[0044] The identification unit 403 is a sheet information acquisition unit used to identify the type of sheet and acquire sheet information including the sheet type. The identification unit 403 determines the target tension Tt according to the sheet type. In the first embodiment, when a sheet is conveyed, the target tension Tt determined for each sheet type stored in the ROM 411 is set according to the identification result by the identification unit 403.

[0045] The tension detection unit 106 detects the tension of the sheet and stores a detected tension value Td in the RAM 412. In the first embodiment, the tension detection range of the tension detection unit 106 is configured to be switchable based on the detected tension value Td stored in the RAM 412 and the switching tension Ts stored in the ROM 411.

[0046] The switching unit 405 is controlled by a switching control unit 407 of the CPU 406, and the tension detection range of the tension detection unit 106 is switched depending on the switching status of the switching unit 405. The switching control unit 407 performs switching control by comparing the switching tension Ts in the ROM 411 with the tension detection value Td acquired by the tension detection unit 404 using a comparison unit 408 in the ROM 411, and performs switching control depending on the result.

[0047] The calculation unit 409 of the CPU 406 compares the target tension Tt for each type of sheet stored in the ROM 411 with the tension detection value Td acquired by the tension detection unit 404 in the comparison unit 408, and calculates the conveying speed from the comparison result.

[0048] The detailed configuration of the switching unit 405 will be described with reference to FIG. 5. The switching unit 405 is composed of a first gain unit 451, a second gain unit 452, and an offset unit 453. The tension detection value Td is gain-adjusted by the first gain unit 451, or offset-corrected by the offset unit 453 and then gain-adjusted by the second gain unit 452. The tension detection range is then switched appropriately based on the output value. In the first embodiment, the output value of the first gain unit 451 is 0 to 5 V, the output value of the second gain unit 4521 is 0 to 10 V, the output value of the offset unit 453 is 0 to 5 V, and the output value of the tension detection unit 106 is 0 to 5 mV. The offset unit 453 also performs offset correction of -5 V.

[0049] (Tension detection method) Next, a tension detection method according to the first embodiment will be described. When detecting tension using the tension detection unit 106, a wider tension detection range allows for a wider range of tension to be detected, but the resolution is lower, making it difficult to obtain a highly accurate tension value. However, if the tension detection range is narrowed in order to obtain a more accurate tension value, the tension value cannot be obtained accurately if it falls outside the tension detection range. Therefore, in the first embodiment, a switching tension Ts is provided as a threshold value, and the tension detection range is switched based on the tension detection value Td obtained each time by the tension detection unit 106.

[0050] The tension detection unit 106 according to the first embodiment is configured to be switchable between a first mode in which the tension detection range is a first detection range DR1 and a second mode in which the tension detection range is a second detection range DR2. More specifically, the tension detection unit 106 can be switched between the first mode and the second mode by the switching control unit 407 based on the tension detected by the tension detection unit 106.

[0051] The first detection range DR1 has a lower limit value of a first lower limit value TL1 and an upper limit value of a first upper limit value TU1. The second detection range DR2 has a lower limit value of a second lower limit value TL2 that is greater than the first lower limit value TL1 and less than the first upper limit value TU1, and an upper limit value of a second upper limit value TU2 that is greater than the first upper limit value TU1. In other words, an overlapping region VDR is provided between the first detection range DR1 and the second detection range DR2, where the tension detection ranges overlap. The upper limit value of the overlapping region VDR is the first upper limit value TU1, and the lower limit value is the second lower limit value TL2.

[0052] FIG. 6 shows a tension detection characteristic diagram according to the first embodiment. The tension detection characteristic diagram is a graph with tension [N] on the vertical axis and time [s] on the horizontal axis. FIG. 6 shows the target tension Tt and the switching tension Ts when the sheet is not a film. FIG. 6 also shows the overlap region VDR in etching. In the first embodiment, the target tension Tt when the sheet is not a film is a value within the second detection range DR2 and is set to a value greater than the first upper limit value TU1. The switching tension Ts is also a value within the range of the overlap region VDR.

[0053] 6, a method will be described in which the recording apparatus 101 starts conveying a sheet from a stopped state, and the tension is gradually increased to approach the target tension Tt. The left side of FIG. 6 shows the transition of the tension when the sheet tension is adjusted from 0 to the target tension Tt.

[0054] In the initial setting, the tension detection unit 106 is set to the first mode and detects tension within a first detection range DR1. When the first conveying roller pair 104 and the second conveying roller pair 110 start to be driven and the sheet begins to be conveyed, the sheet tension gradually increases as the rotation speed of the rollers of the first conveying roller pair 104 and the second conveying roller pair 110 increases, i.e., as the sheet conveying speed increases. During sheet conveyance, the tension detection unit 106 continuously acquires a tension detection value Td at least until the tension becomes equal to the target tension Tt. Then, when the tension detection value Td becomes equal to or greater than the switching tension Ts, the CPU 406 (switching control unit 407) controls the switching unit 405 to switch the tension detection range from the first detection range DR1 to the second detection range DR2. In this way, the tension detection unit 106 is switched from the first mode to the second mode.

[0055] In the first embodiment, there is an overlap region VDR between the first detection range DR1 and the second detection range DR2. This setting prevents the tension detection value Td from falling outside the first detection range DR1 during switching of the tension detection range, preventing a period of time during which the tension detection value Td is not detected correctly. Figure 6 shows a switching time Sp1 as the time required to switch the tension detection range. The switching time Sp1 is the time required for the tension to change from the switching tension Ts to the first upper limit value TU1.

[0056] When the tension detection value Td reaches the target tension Tt, the increase in tension is stopped and the tension is maintained at the target tension Tt. In this way, in the first embodiment, tension control is performed so that the tension detection range is switched while the tension is increasing.

[0057] Next, a method for gradually reducing the tension of a sheet and stopping the conveyance while the sheet is being conveyed by the recording apparatus 101 will be described with reference to Fig. 6. The right side of Fig. 6 shows the transition of the tension when the sheet tension is adjusted from the target tension Tt to 0.

[0058] When the sheet tension is at the target tension Tt, the tension detection unit 106 is set to the second mode and detects the tension within the second detection range DR2. As the rotation speeds of the rollers of the first conveying roller pair 104 and the second conveying roller pair 110 are gradually reduced, the sheet tension gradually decreases. During the sheet stopping operation, the tension detection unit 106 continues to acquire the tension detection value Td until the tension becomes zero. When the tension detection value Td becomes equal to or less than the switching tension Ts, the CPU 406 (switching control unit 407) controls the switching unit 405 to switch the tension detection range from the second detection range DR2 to the first detection range DR1. In this way, the tension detection unit 106 is switched from the second mode to the first mode.

[0059] As described above, there is an overlap region VDR between the first detection range DR1 and the second detection range DR2. This setting prevents the tension detection value Td from falling outside the second detection range DR2 during switching of the tension detection range, preventing a period of time during which the tension detection value Td is not detected correctly. Figure 6 shows a switching time Sp2 as the time required to switch the tension detection range. The switching time Sp2 is the time it takes for the tension to change from the switching tension Ts to the second lower limit value TL2.

[0060] When the tension detection value Td becomes 0, the decrease in tension is stopped and the conveyance of the sheet is stopped. In this way, in the first embodiment, tension control is executed so that the tension detection range is switched while the tension is decreasing.

[0061] In this way, in the first embodiment, the tension detection range of the tension detection unit 106 is switched based on the switching tension Ts to detect the tension both when the sheet tension is gradually increased and when it is gradually decreased. That is, according to the configuration of the first embodiment, even when performing tension control for a sheet with a large target tension Tt, the single tension detection unit 106 can detect the tension from 0 to the target tension Tt with high accuracy. Therefore, according to the configuration of the first embodiment, tension control can be performed with high accuracy using a simple configuration.

[0062] Although the above-described operational example was for a case where the sheet was not a film, for example, for a sheet such as a film that does not require strong tension, the target tension Tt may be set smaller than the switching tension Ts. In the first embodiment, the target tension Tt for the film is set smaller than the switching tension Ts, and the tension detection range is not switched during film tension control.

[0063] (Tension control method) Next, a tension control method in the recording apparatus 101 will be described. First, with reference to Fig. 7, a tension control method for increasing the sheet tension from 0 to a target tension Tt will be described. Fig. 7 shows a flowchart of tension control at the start of sheet conveyance according to the first embodiment. In the first embodiment, sheet tension control is performed by the CPU 406 of the conveyance control unit 316.

[0064] In controlling the tension of the sheet, first, in step S501, the type of sheet (transport medium) is identified. Next, in step S502, it is determined whether the sheet is a film. If the sheet is a film (YES in S502), the process proceeds to step S503, where 0 is substituted into Flag, and Flag=0 is set. On the other hand, if the sheet is If the sheet is not film (NO in S502), the process proceeds to step S504, where 1 is assigned to Flag, and Flag = 1 is set. Flag is used in a later step to determine whether to switch the tension detection range. In the first embodiment, Flag = 0 indicates that the sheet is film, and Flag = 1 indicates that the sheet is a transport medium other than film.

[0065] After a value is assigned to Flag in step S503 or step S504, the process proceeds to step S505, where SW is set to 0. SW is used to set the tension detection range. In the first embodiment, when SW = 0, the tension detection unit 106 is in the first mode, and the tension detection range is set to the first detection range DR1. When SW = 1, the tension detection unit 106 is in the second mode, and the tension detection range is set to the second detection range DR2. That is, in step S505, first, as an initial setting, the tension detection unit 106 is set to the first mode, and the tension detection range is set to the first detection range DR1.

[0066] After SW=0 is set in step S505, sheet conveyance is started in step S506. After sheet conveyance is started, the latest detected tension value Td is compared with the target tension Tt in step S507, and it is determined whether the detected tension value Td is less than the target tension Tt.

[0067] If Tt≦Td (NO in S507), the process proceeds to step S512 to reduce the tension, and the sheet conveying speed is reduced. Note that if the detected tension value Td is equal to the target tension Tt, tension control ends in the subsequent step S513, so in principle, Td=Tt does not occur when determining in step S507. After step S512, the process proceeds to step S513.

[0068] If Tt>Td (YES in S507), processing to increase the tension is performed. Specifically, first, in step S508, it is determined whether Flag=0.

[0069] If Flag=0 (YES in S508), the process proceeds to step S511, where the conveying speed is increased. At this time, the sheet is a film, and the target tension Tt is set lower than the switching tension Ts. Therefore, there is no need to switch the tension detection range of the tension detection unit 106, and the conveying speed is increased in step S511 without comparing the tension detection value Td with the switching tension Ts, etc.

[0070] If Flag=0 is not satisfied (NO in S508), the process proceeds to step S509, where it is determined whether or not the tension detection value Td is equal to or greater than the switching tension Ts.

[0071] If Ts>Td (NO in S509), the process proceeds to step S511, where the conveying speed is increased. That is, the conveying speed is increased in step S511 while the tension detection range remains set to the first detection range DR1. At this time, although the sheet is not a film, tension control continues with the tension detection range remaining at the first detection range DR1 because the tension is still small.

[0072] If Ts≦Td (YES in S509), the process moves to step S510, where SW=1 is set. Then, the tension detection unit 106 is switched from the first mode to the second mode, and the tension detection range is set from the first detection range DR1 to the second detection range DR2. At this time, since the target tension Tt is set to be greater than the switching tension Ts for a sheet other than film, and the tension detection value Td is approaching the first upper limit value TU1 of the first detection range DR1, the tension detection range is switched to the second detection range DR2. Then, in step S510, The process proceeds from step S510 to step S511, where the conveying speed is increased.

[0073] After the conveying speed is increased in step S511 or decreased in step S512, the process proceeds to step S513. In step S513, a new tension detection value Td is acquired, and it is determined whether the tension detection value Td has reached the target tension Tt. If Tt=Td is not true (NO in S513), the process proceeds again to step S507, and tension control continues. Then, the operations from step S507 to step S513 are repeatedly executed until the tension detection value Td reaches the target tension Tt. On the other hand, if Tt=Td is true (YES in S513), it is determined that the tension has reached the target tension Tt, and tension control ends.

[0074] With this configuration, when controlling to gradually increase the tension of a sheet with a relatively high target tension Tt, the tension detection range is switched from the second detection range DR2 to the first detection range DR1 when the tension detection value Td becomes equal to or greater than a predetermined threshold value. Therefore, with the configuration of the first embodiment, it is possible to always detect the sheet tension with high resolution.

[0075] Note that tension control does not necessarily require all steps to be performed as described above; the execution content and order of each step can be changed as appropriate. For example, once it is determined that Flag = 0 in step S508, the operation of subsequent step S508 may be omitted, and the process may proceed directly from step S507 to step S511. Furthermore, once SW = 1 is set in step S510, the operations from step S508 to step S510 may be omitted, and only the operations of steps S507, S511 (S512), and S513 may be repeated. Furthermore, in the above control example, tension control is terminated when Tt = Td, but tension control may also be terminated when the difference between the detected tension value Td and the target tension Tt is equal to or less than a predetermined value.

[0076] Next, a tension control method for reducing the sheet tension to 0 will be described with reference to Fig. 8. Fig. 8 shows a flowchart of tension control when sheet conveyance is stopped according to the first embodiment. Even when the tension is reduced, the CPU 406 of the conveyance control unit 316 controls the sheet tension.

[0077] When stopping the conveyance of the sheet, first, in step S601, it is determined whether or not the tension detection value Td is 0. If Td=0 (YES in S601), the conveyance of the sheet is stopped and tension control is also ended.

[0078] If Td=0 is not true (NO in S601), the process proceeds to step S602, where it is determined whether Flag=0 is true.

[0079] When Flag = 0 (YES in S602), the process proceeds to step S605, and the conveyance speed is decreased. At this time, since the sheet is a film, the tension detection unit 106 is set in the first mode, and the tension detection range is the first detection range DR1. When the sheet is a film, there is no need to switch the tension detection range of the tension detection unit 106, and the conveyance speed is decreased in step S605 without comparing the tension detection value Td with the switching tension Ts.

[0080] When Flag ≠ 0 (NO in S602), the process proceeds to step S603, and it is determined whether the tension detection value Td is less than or equal to the switching tension Ts. When the sheet is other than a film, when starting the conveyance stop control of the sheet, the tension detection unit 106 is set in the second mode, and the tension detection range is the second detection range DR2. Therefore, it is determined by comparing the tension detection value Td with the switching tension Ts whether it is necessary to switch the tension detection range of the tension detection unit 106.

[0081] When Ts < Td (NO in S603), the process proceeds to step S605, and the conveyance speed is decreased. That is, the conveyance speed is decreased in step S605 while the tension detection range remains set to the second detection range DR2.

[0082] When Ts ≥ Td (YES in S603), the process proceeds to step S604, and SW = 0. Then, the tension detection unit 106 is switched from the second mode to the first mode, and the tension detection range is set from the second detection range DR2 to the first detection range DR1. At this time, since the sheet is other than a film, the target tension Tt is set larger than the switching tension Ts, and the tension detection value Td is approaching the second lower limit value TL2 of the second detection range DR2, the tension detection range is switched to the first detection range DR1. Then, the process proceeds from step S604 to step S605, and the conveyance speed is increased.

[0083] If the conveying speed is reduced in step S605, the process returns to step S601. Then, the operations from step S601 to step S605 are repeatedly executed until the tension detection value Td becomes 0.

[0084] With this configuration, when controlling to gradually reduce the tension of a sheet with a relatively high target tension Tt, the tension detection range is switched from the second detection range DR2 to the first detection range DR1 when the tension detection value Td becomes equal to or less than a predetermined threshold value. Therefore, with the configuration of the first embodiment, it is possible to always detect the sheet tension with high resolution.

[0085] Note that in tension control, not all steps necessarily need to be performed as described above, and the execution content and execution order of each step can be changed as appropriate. For example, once SW=0 is set in step S604, the subsequent operations of steps S603 and S604 may be omitted. Also, in the above control example, the tension is set to 0, but the same control as the above control example can also be used when lowering the tension to a predetermined target value.

[0086] As described above, according to the configuration of the first embodiment, tension control is performed while the tension detection range is appropriately switched depending on the sheet tension. In the first embodiment, when a conveyed medium is used whose target tension Tt, which is set depending on the sheet type, is smaller than the second lower limit TL2, the tension detection unit 106 always detects the tension within the first detection range DR1. On the other hand, when a conveyed medium whose target tension Tt is larger than the second lower limit TL2 is used, the tension detection range is switched from the first detection range DR1 to the second detection range DR2 when the tension is gradually increased. Furthermore, when a conveyed medium whose target tension Tt is larger than the second lower limit TL2 is used, the tension detection range is switched from the second detection range DR2 to the first detection range DR1 when the tension is gradually decreased.

[0087] As described above, the configuration of the first embodiment makes it possible to switch the tension detection range of the tension detection unit 106 depending on the type of sheet and the detected tension value Td, both in cases where the sheet tension is gradually increased and decreased. In other words, since the tension can be constantly detected and controlled with high resolution and high accuracy, it is possible to suppress the occurrence of sheet stretching or bending, thereby suppressing sheet transport failures. Furthermore, it is possible to suppress image quality degradation caused by sheet transport failures.

[0088] In the first embodiment, the target tension Tt is set individually according to sheet information such as the type of sheet. However, the switching tension Ts and tension detection range may also be set individually according to the sheet information. For example, the first upper limit value TU1, the first lower limit value TL1, the second upper limit value TU2, the second lower limit value TL2, and the switching tension Ts may be individually determined for each predetermined sheet information. By configuring the tension detection range to be switched according to the sheet information, including the thickness and material of the sheet, and the tension detection value Td, tension can be detected and controlled with higher accuracy. Furthermore, in the first embodiment, the control to increase the sheet tension and the control to decrease the sheet tension were distinguished as separate controls. However, they may be combined into a single tension control from the start to the stop of sheet transport in the recording apparatus 101.

[0089] <Second Example> Next, a second embodiment of the present invention will be described. The second embodiment differs from the first embodiment in that two switching tensions are set for switching the tension detection range. By providing two switching tensions for the tension detection range, it is possible to reduce overlapping areas of the tension detection range and improve the accuracy of tension detection. Below, only the differences between the configuration of the second embodiment and the configuration of the first embodiment will be described. Components in the second embodiment that are similar to those in the first embodiment will be assigned the same reference numerals and will not be described again.

[0090] (Tension detection method) A tension detection method according to the second embodiment will be described. The tension detection unit 106 according to the second embodiment is configured to be switchable between a first mode in which the tension detection range is a first detection range DR1 and a second mode in which the tension detection range is a second detection range DR2. More specifically, the tension detection unit 106 can be switched between the first mode and the second mode by a switching control unit 407 based on the tension detected by the tension detection unit 106.

[0091] The first detection range DR1 has a lower limit of a first lower limit TL1 and an upper limit of a first upper limit TU1. The second detection range DR2 has a lower limit of a second lower limit TL2 that is greater than the first lower limit TL1 and less than the first upper limit TU1, and an upper limit of a second upper limit TU2 that is greater than the first upper limit TU1. That is, the first detection range DR1 and the second detection range DR2 have an overlapping region VDR where the tension detection ranges overlap.

[0092] In the second embodiment, a first switching tension Ts1, which is a first threshold, and a second switching tension Ts2, which is a second threshold, are set as tension thresholds used when switching the tension detection range. The first switching tension Ts1 is the same as the second lower limit TL2 of the second detection range DR2, and the second switching tension Ts2 is the same as the first upper limit TU1 of the first detection range DR1, but is greater than the first switching tension Ts1. In other words, the upper limit of the overlap region VDR in the second embodiment is the second switching tension Ts2, and the lower limit is the first switching tension Ts1. Therefore, the range of the overlap region VDR in the second embodiment is narrower than the overlap region VDR in the first embodiment.

[0093] In the second embodiment, because there is an overlap region VDR, the tension detection value Td does not fall outside the tension detection range during switching of the tension detection range, preventing a period of time during which the tension detection value Td is not detected correctly. Figure 9 shows switching times Sp1 and SP2 as the time required to switch the tension detection range. Switching time Sp1 is the time required for the tension to change from the first switching tension Ts1 to the first upper limit value TU1. Switching time Sp2 is the time required for the tension to change from the second switching tension Ts2 to the second lower limit value TL2.

[0094] FIG. 9 shows a tension detection characteristic diagram according to the second embodiment. 9 is a graph showing tension [N] on the axis and time [s] on the horizontal axis. Fig. 9 shows the target tension Tt, first switch tension Ts1, and second switch tension Ts2 when the sheet is not a film. Fig. 9 also shows the overlap region VDR etched. In the second embodiment, the target tension Tt when the sheet is not a film is a value within the second detection range DR2 and is set to a value greater than the first upper limit value TU1.

[0095] 9, a method will be described in which, from a stopped state of the recording apparatus 101, sheet conveyance is started and the tension is gradually increased to approach the target tension Tt. The left side of FIG. 9 shows the transition of the tension when the sheet tension is adjusted from a state where the tension is 0 to the target tension Tt.

[0096] In the initial setting, the tension detection unit 106 is set to the first mode and detects tension within a first detection range DR1. When sheet conveyance begins and the sheet conveyance speed increases, the sheet tension gradually increases. In the second embodiment, when the tension detection value Td becomes equal to or greater than the first switching tension Ts1, the CPU 406 (switching control unit 407) controls the switching unit 405 to switch the tension detection range from the first detection range DR1 to the second detection range DR2. In this way, the tension detection unit 106 is switched from the first mode to the second mode. Then, when the tension detection value Td reaches the target tension Tt, the increase in tension is stopped and the tension is maintained at the target tension Tt.

[0097] Next, a method for gradually reducing the tension of a sheet and stopping the conveyance while the sheet is being conveyed by the recording apparatus 101 will be described with reference to Fig. 9. The right side of Fig. 9 shows the transition of the tension when the sheet tension is adjusted from the target tension Tt to 0.

[0098] When the sheet tension is at the target tension Tt, the tension detection unit 106 is set to the second mode and detects the tension within the second detection range DR2. As the sheet conveying speed gradually decreases, the sheet tension gradually decreases. In the second embodiment, when the tension detection value Td becomes equal to or less than the second switching tension Ts2, the CPU 406 (switching control unit 407) controls the switching unit 405 to switch the tension detection range from the second detection range DR2 to the first detection range DR1. In this way, the tension detection unit 106 is switched from the second mode to the first mode. Then, when the tension detection value Td becomes 0, the decrease in tension stops and sheet conveyance is stopped.

[0099] Thus, in the second embodiment, the tension detection range of the tension detection unit 106 is switched based on the switching tension Ts to detect the tension both when the sheet tension is gradually increased and when it is gradually decreased. Furthermore, in the second embodiment, the overlapping area VDR between the first detection range DR1 and the second detection range DR2 can be set narrower than in the first embodiment. This makes it possible to set the respective ranges of the first detection range DR1 and the second detection range DR2 narrower, thereby further improving the resolution in each detection range. Consequently, since the tension can be detected and controlled with high accuracy, sheet conveyance problems can be suppressed.

[0100] (Tension control method) Next, a tension control method for the recording device 101 according to the second embodiment will be described. The tension control method according to the second embodiment has many overlapping parts with the tension control method according to the first embodiment, so a description of the overlapping parts will be omitted and the explanation will focus on the differences.

[0101] First, a tension control method for increasing the sheet tension from 0 to the target tension Tt will be described with reference to Fig. 10. Fig. 10 shows the tension control method for increasing the sheet tension from 0 to the target tension Tt at the start of sheet conveyance according to the second embodiment. 10 shows a flowchart of tension control in the second embodiment. In the second embodiment, the CPU 406 of the conveyance control unit 316 controls the tension of the sheet.

[0102] The processes from step S801 to step S806 are the same as the processes from step S501 to step S506 according to Example 1. That is, in controlling the tension of the sheet, the following steps are performed: identifying the type of sheet (S801), determining the type of sheet (S802), substituting a value into Flag (S803, S804), setting SW=0 (S805), and starting conveyance of the sheet (S806).

[0103] Furthermore, steps S807 to S813 are generally similar to steps S507 to S513 in the first embodiment. Of these steps, the second embodiment differs from the first embodiment in that the threshold value compared with the tension detection value Td in step S809 is the first switch tension Ts1. That is, while the tension detection value Td is smaller than the first switch tension Ts1, the tension in the second embodiment is controlled in the same way as in the first embodiment.

[0104] If it is determined in step S807 that Tt≦Td (NO in S807), the process proceeds to step S812 where the sheet conveying speed is reduced in order to reduce the tension, and then in step S813 it is determined whether or not to end the tension control.

[0105] If it is determined in step S807 that Tt>Td (YES in S807), and Flag=0 and the sheet is a film (YES in S808), the process proceeds to step S811, where the sheet conveying speed is increased. Thereafter, it is determined in step S813 whether or not to end tension control.

[0106] If it is determined in step S807 that Tt>Td (YES in S807), and Flag is not 0 and the sheet is not a film (NO in S808), the process proceeds to step S809. In step S809, it is determined whether the tension detection value Td is equal to or greater than the first switching tension Ts1. If Ts1>Td (NO in S809), the process proceeds to step S811, where the conveying speed is increased. If Ts1≦Td (YES in S809), the process proceeds to step S810, where SW=1 is set, and the tension detection range is switched from the first detection range DR1 to the second detection range DR2. Thereafter, the process proceeds to step S811, where the conveying speed is increased, and in step S813, it is determined whether or not to end tension control.

[0107] In step S813, it is determined whether the newly obtained tension detection value Td has reached the target tension Tt, and the operations from step S807 to step S813 are repeatedly executed until the tension detection value Td reaches the target tension Tt.

[0108] Subsequently, referring to FIG. 11, a tension control method for lowering the tension of the sheet to 0 will be described. FIG. 11 shows a flowchart of the tension control when the sheet conveyance stops according to the second embodiment. Even when the tension is decreasing, the CPU 406 of the conveyance control unit 316 controls the tension of the sheet.

[0109] The steps from step S901 to step S905 are generally the same as the steps from step S601 to step S605 according to the first embodiment. Among these steps, the second embodiment is different from the first embodiment in that the threshold value compared with the tension detection value Td in step S903 is the second switching tension Ts2. That is, while the tension detection value Td is greater than the second switching tension Ts2, the tension is controlled in the same manner as in the first embodiment in the second embodiment.

[0110] The steps of step S901, S902, and S905 are the same as the steps of step S601, S602, and S605 according to the first embodiment, respectively. That is, when the sheet is a film, after determining whether the tension detection value Td is 0 (S901) and determining whether the sheet is a film (S902), the conveyance speed of the sheet is decreased (S905), and the process returns to step S901 again.

[0111] When the sheet is other than a film (NO in S902), the process proceeds to step S903, and it is determined whether the tension detection value Td is less than or equal to the second switching tension Ts2. When Ts2 < Td (NO in S903), the process proceeds to step S905 to decrease the conveyance speed, and then returns to step S901 again.

[0112] If Ts2≧Td (YES in S903), the process proceeds to step S904, where SW is set to 0, and the tension detection range is switched from the second detection range DR2 to the first detection range DR1. After that, the process proceeds to step S905, where the conveying speed is reduced, and the process returns to step S901.

[0113] In step S901, it is determined whether the newly acquired tension detection value Td has become 0, and the operations from step S901 to step S905 are repeatedly executed until the tension detection value Td becomes 0.

[0114] As described above, according to the configuration of the second embodiment, tension control is performed while the tension detection range is appropriately switched depending on the sheet tension. In the second embodiment, when a conveyed medium is used whose target tension Tt, which is set depending on the sheet type, is smaller than the second lower limit TL2, the tension detection unit 106 always detects the tension within the first detection range DR1. On the other hand, when a conveyed medium whose target tension Tt is larger than the first upper limit TU1 is used, the tension detection range is switched from the first detection range DR1 to the second detection range DR2 when the tension is gradually increased. Furthermore, when a conveyed medium whose target tension Tt is larger than the first upper limit TU1 is used, the tension detection range is switched from the second detection range DR2 to the first detection range DR1 when the tension is gradually decreased. Note that each detection range is set so that the target tension Tt of each conveyed medium does not lie within the overlap region VDR.

[0115] As described above, according to the configuration of the second embodiment, the tension detection range of the tension detection unit 106 can be switched depending on the type of sheet and the tension detection value Td, both in the cases where the sheet tension is gradually increased and decreased. Furthermore, compared to the first embodiment, the first detection range DR1 and the second detection range DR2 can each be set narrower, so that tension can be detected and controlled with higher accuracy, thereby preventing sheet conveyance failures.

[0116] <Third Example> Next, a third embodiment of the present invention will be described. The third embodiment differs from the first embodiment in that three types of tension detection ranges are provided and four switching tensions are set for switching the tension detection ranges. By increasing the number of tension detection ranges, overlapping areas of the tension detection ranges can be reduced, improving the accuracy of tension detection. Below, only the differences between the configuration of the third embodiment and the configuration of the first embodiment will be described. Components in the third embodiment that are similar to those in the first embodiment will be assigned the same reference numerals and will not be described again.

[0117] (Tension detection method) A tension detection method according to the third embodiment will be described. The detection unit 106 is configured to be switchable between a first mode in which the tension detection range is a first detection range DR1, a second mode in which the tension detection range is a second detection range DR2, and a third mode in which the tension detection range is a third detection range DR3. More specifically, the tension detection unit 106 can be switched between the first mode and the second mode by the switching control unit 407 based on the tension detected by the tension detection unit 106. Furthermore, the tension detection unit 106 can be switched between the second mode and the third mode by the switching control unit 407 based on the tension detected by the tension detection unit 106.

[0118] The first detection range DR1 has a lower limit value of a first lower limit value TL1 and an upper limit value of a first upper limit value TU1. The second detection range DR2 has a lower limit value of a second lower limit value TL2 that is greater than the first lower limit value TL1 and less than the first upper limit value TU1, and an upper limit value of a second upper limit value TU2 that is greater than the first upper limit value TU1. The third detection range DR3 has a lower limit value of a third lower limit value TL3 that is greater than the first upper limit value TU1 and the second lower limit value TL2 and less than the second upper limit value TU2, and an upper limit value of a third upper limit value TU3 that is greater than the second upper limit value TU2.

[0119] The first detection range DR1 and the second detection range DR2 define a first overlapping region VDR1 where the tension detection ranges overlap. The upper limit of the overlapping region VDR is a first upper limit value TU1, and the lower limit is a second lower limit value TL2. The second detection range DR2 and the third detection range DR3 define a second overlapping region VDR2 where the tension detection ranges overlap. The upper limit of the overlapping region VDR is a second upper limit value TU2, and the lower limit is a third lower limit value TL3.

[0120] In the third embodiment, because there is a first overlap region VDR1 and a second overlap region VDR2, the tension detection value Td does not fall outside the tension detection range during switching of the tension detection range, preventing a period of time during which the tension detection value Td is not detected correctly. FIG. 12 shows switching times Sp1, SP2, SP3, and SP4 as the time required to switch the tension detection range. Switching time Sp1 is the time required for the tension to change from the first switching tension Ts1 to the first upper limit value TU1. Switching time Sp2 is the time required for the tension to change from the second switching tension Ts2 to the second lower limit value TL2. Switching time Sp3 is the time required for the tension to change from the third switching tension Ts3 to the second upper limit value TU2. Switching time Sp4 is the time required for the tension to change from the fourth switching tension Ts4 to the third lower limit value TL3.

[0121] In the third embodiment, four thresholds are set as tension thresholds used when switching the tension detection range. Specifically, a first threshold, a first switching tension Ts1, a second threshold, a second threshold, a third threshold, a third threshold, a fourth threshold, a fourth threshold, a fourth switching tension Ts4, are set. The first switching tension Ts1 is the same as the second lower limit TL2 of the second detection range DR2, and the second switching tension Ts2 is the same as the first upper limit TU1 of the first detection range DR1 but is greater than the first switching tension Ts1. The third switching tension Ts3 is the same as the third lower limit TL3 of the third detection range DR3, and the fourth switching tension Ts4 is the same as the second upper limit TU2 of the second detection range DR2 but is greater than the third switching tension Ts3. That is, the upper limit of the first overlap region VDR1 in the third embodiment is the second switching tension Ts2, and the lower limit is the first switching tension Ts1. The upper limit of the second overlap region VDR2 is the fourth switch tension Ts4, and the lower limit is the third switch tension Ts3.

[0122] FIG. 12 shows a tension detection characteristic diagram according to the third embodiment. The tension detection characteristic diagram is a graph with tension [N] on the vertical axis and time [s] on the horizontal axis. FIG. 12 shows the target tension Tt when the sheet has the largest target tension Tt among the selectable sheet types. FIG. 12 also shows a first switch tension Ts1, a second switch tension Ts2, a third switch tension Ts3, and a fourth switch tension Ts4, and the first overlap The region VDR1 and the second overlap region VDR2 are indicated by etching. In this control example, the target tension Tt is set to a value within the third detection range DR3 and greater than the second upper limit value TU2.

[0123] 12, a method will be described in which, from a stopped state of the recording apparatus 101, sheet conveyance is started and the tension is gradually increased to approach the target tension Tt. The left side of FIG. 12 shows the transition of the tension when the sheet tension is adjusted from a state where the tension is 0 to the target tension Tt.

[0124] In the initial setting, the tension detection unit 106 is set to the first mode and detects tension within the first detection range DR1. When sheet conveyance begins and the sheet conveyance speed increases, the sheet tension gradually increases. In the third embodiment, when the tension detection value Td becomes equal to or greater than the first switching tension Ts1, the CPU 406 (switching control unit 407) controls the switching unit 405 to switch the tension detection range from the first detection range DR1 to the second detection range DR2. In this way, the tension detection unit 106 is switched from the first mode to the second mode.

[0125] Tension control continues with the tension detection unit 106 in the second mode, and when the tension detection value Td becomes equal to or greater than the third switching tension Ts3, the tension detection range is switched from the second detection range to the third detection range DR3. The tension detection unit 106 is then switched from the second mode to the third mode. Tension control continues thereafter with the tension detection unit 106 in the third mode, and when the tension detection value Td reaches the target tension Tt, the increase in tension is stopped and the tension is maintained at the target tension Tt.

[0126] Next, a method for gradually reducing the sheet tension and stopping the conveyance while the sheet is being conveyed by the recording apparatus 101 will be described with reference to Fig. 12. The right side of Fig. 12 shows the transition of the tension when the sheet tension is adjusted from the target tension Tt to 0.

[0127] When the sheet tension is at the target tension Tt, the tension detection unit 106 is set to the third mode and detects the tension within the third detection range DR3. As the sheet conveying speed gradually decreases, the sheet tension gradually decreases. In the third embodiment, when the tension detection value Td becomes equal to or less than the fourth switching tension Ts4, the CPU 406 (switching control unit 407) controls the switching unit 405 to switch the tension detection range from the third detection range DR3 to the second detection range DR2. In this way, the tension detection unit 106 is switched from the third mode to the second mode.

[0128] Tension control continues with the tension detection unit 106 in the third mode, and when the tension detection value Td becomes equal to or less than the second switching tension Ts2, the tension detection range is switched from the second detection range to the first detection range DR1. Then, the tension detection unit 106 is switched from the second mode to the first mode. After that, tension control continues with the tension detection unit 106 in the first mode, and when the tension detection value Td becomes 0, the decrease in tension stops and sheet conveyance is stopped.

[0129] In this way, in the third embodiment, the tension detection range is divided into a greater number of sections than in the first embodiment, which increases the resolution in each detection range. As a result, tension can be detected and controlled with higher accuracy, which reduces stretching and bending of the sheet and prevents sheet conveyance problems.

[0130] (Tension control method) Next, we will explain the tension control method in the recording device 101. The tension control method according to the third embodiment has many overlapping parts with the tension control method according to the first embodiment, so we will omit explanation of the overlapping parts and focus on the differences.

[0131] First, a tension control method for increasing the sheet tension from 0 to the target tension Tt will be described with reference to Fig. 13. Fig. 13 shows a flowchart of tension control at the start of sheet conveyance according to the third embodiment. In the third embodiment, the sheet tension control is performed by the CPU 406 of the conveyance control unit 316.

[0132] The processes of steps S1101, S1102, and S1104 are the same as the processes up to steps S501, S502, and S503 in Example 1. That is, when controlling the tension of a sheet, first, the type of sheet is identified (S1101), and it is determined whether the sheet is a film (S1102).If the sheet is a film, 0 is assigned to Flag, and Flag = 0 is established (S1104).

[0133] If the sheet is not film (NO in S1102), the process proceeds to step S1103, where it is determined whether the sheet is cardboard. In the third embodiment, the detection ranges are set so that the target tension Tt for cardboard is greater than the second upper limit value TU2 of the second detection range DR2, and the target tension Tt for sheets other than film and cardboard is a value within the second detection range DR2.

[0134] If the sheet is film (YES in S1103), the process proceeds to step S1105, where 2 is assigned to Flag, and Flag = 2. On the other hand, if the sheet is not cardboard (NO in S1103), the process proceeds to step S1106, where 1 is assigned to Flag, and Flag = 1. In the third embodiment, Flag = 0 indicates that the sheet is film, Flag = 1 indicates that the sheet is a transport medium other than film or cardboard, and Flag = 2 indicates that the sheet is cardboard.

[0135] After a value is assigned to Flag in any one of steps S1104, S1105, and S1106, the process proceeds to step S1107. Steps S1107 to S1109 are the same as steps S505 to S507 in the first embodiment. That is, SW is set to 0 (S1107), sheet conveyance is started (S1108), and it is determined whether the tension detection value Td is less than the target tension Tt (S1109). Note that in the third embodiment, when SW=0, the tension detection unit 106 is in the first mode, and the tension detection range is set to the first detection range DR1. When SW=1, the tension detection unit 106 is in the second mode, and the tension detection range is set to the second detection range DR2. When SW=2, the tension detection unit 106 is in the third mode, and the tension detection range is set to the third detection range DR3.

[0136] If it is determined in step S1109 that Tt≦Td (NO in S1109), the process proceeds to step S1117 to reduce the sheet conveying speed in order to reduce the tension, and then in step S1118 it is determined whether or not to end the tension control.

[0137] If it is determined in step S1109 that Tt>Td (YES in S1109), the process proceeds to step S1110, where it is determined whether Flag=0, i.e., whether the sheet is film. If Flag=0 and the sheet is film (YES in S1110), the process proceeds to step S1116, where the sheet conveying speed is increased.

[0138] On the other hand, if Flag=0 and the sheet is not film (NO in S1110), The process proceeds to step S1111, where it is determined whether the detected tension value Td is equal to or greater than the first switch tension Ts1.

[0139] If Ts1>Td (NO in S1111), the process proceeds to step S1116, where the conveying speed is increased. That is, tension control continues with the tension detection unit 106 in the first mode and the tension detection range being the first detection range DR1.

[0140] If Ts1≦Td (YES in S1111), the process proceeds to step S1112, where it is determined whether Flag=1, that is, whether the sheet is a conveying medium other than film or cardboard.

[0141] If Flag=1 (YES in S1112), the sheet is a conveying medium other than film or cardboard, and the process proceeds to step S1114, where SW=1 is set. Then, the tension detection unit 106 switches from the first mode to the second mode, and the tension detection range is set from the first detection range DR1 to the second detection range DR2. Then, the process proceeds from step S1114 to step S1116, and the conveying speed is increased. In this case, subsequent tension control is performed with the tension detection unit 106 in the second mode and the tension detection range in the second detection range DR2.

[0142] If Flag=1 is not true (NO in S1112), the sheet is cardboard, so the process proceeds to step S1113, where it is determined whether the tension detection value Td is equal to or greater than the third switch tension Ts3.

[0143] If Ts3>Td (NO in S1113), the process proceeds to step S1114, where SW=1 is set, and the process proceeds to step S1116, where the conveying speed is increased. In this case, the tension detection unit 106 is in the second mode, and the subsequent tension control is performed with the tension detection range being the second detection range DR2.

[0144] If Ts3≦Td (YES in S1113), the process proceeds to step S1115, where SW is set to 2. Then, the tension detection unit 106 is switched to the third mode, and the tension detection range is set to the third detection range DR3. After that, the process proceeds from step S1115 to step S1116, and the conveying speed is increased. In this case, subsequent tension control is performed with the tension detection unit 106 in the third mode and the tension detection range set to the third detection range DR3.

[0145] After the conveying speed is increased in step S1116 or decreased in step S1117, the process proceeds to step S1118. The process of step S1118 is similar to the process of step S513 in the first embodiment. Then, the operations from step S1109 to step S1118 are repeatedly executed until the tension detection value Td reaches the target tension Tt.

[0146] It should be noted that in tension control, it is not necessary for all steps to be performed as described above, and the execution content and order of each step can be changed as appropriate. For example, if it is determined once in step S1110 that Flag = 0, or once in step S1112 that Flag = 1, the operations of subsequent steps S1110 and S1112 may be omitted. Also, for example, if SW = 2 is set once in step S1115, the operations from subsequent steps S1110 to S1115 may be omitted, and only the operations of steps S1110, S1116 (S1117), and S1118 may be repeated. Also, in the above control example, tension control was terminated when Tt = Td, but it may also be terminated when the difference between the tension detection value Td and the target tension Tt is equal to or less than a predetermined value. If this occurs, tension control may be terminated.

[0147] Next, referring to FIG. 14, a tension control method for reducing the tension of the sheet to 0 will be described. FIG. 14 shows a flowchart of the tension control when the sheet conveyance stops according to the third embodiment. Even when the tension is decreasing, the CPU 406 of the conveyance control unit 316 controls the tension of the sheet.

[0148] The steps of steps S1201, S1202, and S1208 are the same as the steps of steps S601, S602, and S605 according to the first embodiment, respectively. That is, when the sheet is a film, it is determined whether the tension detection value Td is 0 (S1201), and it is determined whether the sheet is a film (S1202). Then, the conveyance speed of the sheet is decreased (S1208), and the process returns to step S1201 again.

[0149] If Flag≠0 (NO in S1202), the sheet is a conveyance medium other than a film, and the process proceeds to step S1203 to determine whether the tension detection value Td is less than or equal to the fourth switching tension Ts4. If Ts4<Td (NO in S1203), the process proceeds to step S1208 to decrease the conveyance speed, and then the process returns to step S1201 again.

[0150] If Ts4≥Td (YES in S1203), the process proceeds to step S1204 to determine whether the tension detection value Td is less than or equal to the second switching tension Ts2.

[0151] If Ts2≥Td (YES in S1204), the process proceeds to step S1206 to set SW = 0, and the tension detection range is switched to the first detection range DR1. At this time, regardless of whether the sheet is cardboard or a conveyance medium other than film and cardboard, the same processing is performed. Then, the process proceeds to step S1208 to decrease the conveyance speed, and then the process returns to step S1201 again.

[0152] If Ts2<Td (NO in S1204), the process proceeds to step S1205 to determine whether Flag = 1, that is, whether the sheet is a conveyance medium other than film and cardboard.

[0153] If it is determined in step S1205 that Flag = 1 is not true (NO in S1205), the sheet is cardboard (Flag = 2), and the tension detection value Td should be within the range of Ts2 < Td ≤ Ts4. Therefore, the process proceeds to step S1207, where SW = 1 is set, and the tension detection range is switched to the second detection range DR2. Then, the process proceeds to step S1208, where the conveyance speed is decreased, and the process returns to step S1201 again.

[0154] On the other hand, if it is determined in step S1205 that Flag = 1 is true (YES in S1205), the sheet is a conveyance medium other than film and cardboard, and the tension detection value Td should be within the range of Ts2 < Td ≤ Ts4. In this case, the tension detection range is already the second detection range DR2 at the start of tension control. Therefore, thereafter, the process proceeds to step S1208, where the conveyance speed is decreased, and the process returns to step S1201 again.

[0155] In step S1201, it is determined whether the newly obtained tension detection value Td has become 0, and the operations from step S1201 to step S1208 are repeatedly executed until the tension detection value Td becomes 0.

[0156] Note that in tension control, it is not always necessary for all steps to be performed as described above, and the execution details and execution order of each step can be changed as appropriate. For example, After SW = 1 is set once in step S1205, the operations of subsequent steps S1205 and S1207 may be omitted.

[0157] As described above, according to the configuration of the third embodiment, tension control is performed while the tension detection range is appropriately switched depending on the sheet tension. In the second embodiment, when a conveyed medium is used whose target tension Tt, which is set depending on the sheet type, is smaller than the second lower limit TL2, the tension detection unit 106 always detects the tension within the first detection range DR1. On the other hand, when a conveyed medium whose target tension Tt is larger than the first upper limit TU1 and smaller than the third lower limit TL3 is used, the tension detection range is switched from the first detection range DR1 to the second detection range DR2 when the tension is gradually increased. Also, when a conveyed medium whose target tension Tt is larger than the first upper limit TU1 and smaller than the third lower limit TL3 is used, the tension detection range is switched from the second detection range DR2 to the first detection range DR1 when the tension is gradually decreased. Also, when a conveyed medium whose target tension Tt is larger than the second upper limit TU2 is used, the tension detection range is switched in the order of the first detection range DR1, the second detection range DR2, and the third detection range DR3 when the tension is gradually increased. Furthermore, when using a conveyed medium whose target tension Tt is greater than the second upper limit TU2 and the tension is gradually reduced, the tension detection range is switched in the order of the third detection range DR3, the second detection range DR2, and the first detection range DR1. Note that each detection range is set so that the target tension Tt of each conveyed medium is not located within the range of the overlap region VDR.

[0158] As described above, according to the configuration of the third embodiment, the tension detection range of the tension detection unit 106 can be switched depending on the type of sheet and the tension detection value Td, both in the cases where the sheet tension is gradually increased and decreased. Furthermore, compared to the first embodiment, the tension detection range is divided into a greater number of parts, so that the tension can be detected and controlled with higher accuracy, thereby suppressing sheet conveyance failures.

[0159] The disclosure of this embodiment includes the following configuration. (Configuration 1) a conveying unit that conveys the sheet while applying tension to the sheet along the sheet conveying direction; a tension detection unit that detects the tension of the sheet being conveyed to the conveying unit; Equipped with the tension detection unit is configured to be switchable between a first mode capable of detecting tension between a first lower limit value and a first upper limit value, and a second mode capable of detecting tension between a second lower limit value greater than the first lower limit value and a second upper limit value greater than the first upper limit value, A conveying device comprising: a control unit that switches between the first mode and the second mode based on the tension detected by the tension detection unit. (Configuration 2) the conveying unit has a tension adjusting means for adjusting the tension applied to the sheet, The control unit is configured to switch the tension detection unit to the second mode when the tension detected by the tension detection unit becomes equal to or greater than a threshold value while the tension detection unit is in the first mode and the tension of the sheet is increased toward a target value by the tension adjustment means. (Configuration 3) 3. The conveying device according to configuration 2, wherein the threshold value is greater than the second lower limit value and less than the first upper limit value. (Configuration 4) the conveying unit has a tension adjusting means for adjusting the tension applied to the sheet, When the control unit is in the second mode and the tension adjustment unit reduces the tension of the sheet toward the target value, the control unit 4. The conveying device according to any one of configurations 1 to 3, wherein the tension detector switches to the first mode when the tension becomes equal to or less than a threshold value. (Configuration 5) 5. The conveying device according to configuration 4, wherein the threshold value is greater than the second lower limit value and less than the first upper limit value. (Configuration 6) the conveying unit has a tension adjusting means for adjusting the tension applied to the sheet, The control unit when the tension detected by the tension detection unit becomes equal to or greater than a first threshold value in a case where the tension detection unit is in the first mode and the tension of the sheet is increased toward a target value by the tension adjustment unit, the tension detection unit is switched to the second mode; The conveying device described in configuration 1 is characterized in that, when the tension detection unit is in the second mode and the tension adjustment means is reducing the sheet tension toward a target value, the tension detection unit switches to the first mode when the tension detected by the tension detection unit becomes equal to or less than a second threshold value that is greater than the first threshold value. (Configuration 7) the first threshold value is the same as the second lower limit value, 7. The conveying device according to configuration 6, wherein the second threshold value is the same as the first upper limit value. (Configuration 8) the tension detection unit is configured to be switchable to a third mode in which tension between a third lower limit value that is greater than the first upper limit value and less than the second upper limit value, and a third upper limit value that is greater than the second upper limit value, and The conveying device according to configuration 1, wherein the control unit is capable of switching between the second mode and the third mode based on the tension detected by the tension detection unit. (Configuration 9) the conveying unit has a tension adjusting means for adjusting the tension applied to the sheet, The control unit when the tension detected by the tension detection unit becomes equal to or greater than a first threshold value in a case where the tension detection unit is in the first mode and the tension of the sheet is increased toward a target value by the tension adjustment unit, the tension detection unit is switched to the second mode; when the tension detection unit is in the second mode and the tension adjustment unit is reducing the tension of the sheet toward a target value, and when the tension detected by the tension detection unit becomes equal to or less than a second threshold value that is greater than the first threshold value, the tension detection unit is switched to the first mode; when the tension detection unit is in the second mode and the tension adjustment unit is increasing the tension of the sheet toward a target value, and when the tension detected by the tension detection unit becomes equal to or greater than a third threshold value that is greater than the second threshold value, the tension detection unit is switched to the third mode; The conveying device described in configuration 8 is characterized in that, when the tension detection unit is in the third mode and the tension adjustment means is reducing the sheet tension toward a target value, the tension detection unit switches to the second mode when the tension detected by the tension detection unit becomes equal to or less than a fourth threshold value that is greater than the third threshold value. (Configuration 10) the first threshold value is the same as the second lower limit value, the second threshold is the same value as the first upper limit value, the third threshold value is the same value as the third lower limit value, 10. The conveying device according to configuration 9, wherein the fourth threshold value is the same value as the second upper limit value. (Configuration 11) a sheet information acquisition unit that acquires predetermined sheet information of the sheet being conveyed; A conveying device described in any one of configurations 1 to 10, characterized in that the first lower limit value, the first upper limit value, the second lower limit value, and the second upper limit value are individually determined in advance for each of the specified sheet information. (Configuration 12) A conveying device according to any one of configurations 1 to 11, a recording unit that records an image on a sheet; A recording device comprising: [Explanation of symbols]

[0160] 106... tension detection unit, 407... switching control unit (control unit), TL1... first lower limit value, TU1... first upper limit value, TL2... second lower limit value, TU2... second upper limit value

Claims

1. a conveying unit that conveys the sheet while applying tension to the sheet along the sheet conveying direction; a tension detection unit that detects the tension of the sheet being conveyed to the conveying unit; a tension adjusting means for adjusting the tension of the sheet conveyed by the conveying section; Equipped with the tension detection unit is configured to be switchable between a first mode capable of detecting tension between a first lower limit value and a first upper limit value, and a second mode capable of detecting tension between a second lower limit value greater than the first lower limit value and a second upper limit value greater than the first upper limit value, A conveying device comprising: a control unit that switches between the first mode and the second mode based on the type of sheet and the tension detected by the tension detection unit.

2. The control unit of the conveying device described in Claim 1 is characterized in that when the tension detection unit is in the first mode and the tension of the sheet is increased toward a target value by the tension adjustment means, the control unit switches the tension detection unit to the second mode when the tension detected by the tension detection unit becomes equal to or greater than a threshold value.

3. 3. The conveying device according to claim 2, wherein the threshold value is greater than the second lower limit value and less than the first upper limit value.

4. The control unit of the conveying device described in Claim 1 is characterized in that when the control unit is in the second mode and the tension of the sheet is reduced toward a target value by the tension adjustment means, the control unit switches the tension detection unit to the first mode when the tension detected by the tension detection unit falls below a threshold value.

5. The conveying device according to claim 4 , wherein the threshold value is greater than the second lower limit value and less than the first upper limit value.

6. The control unit when the tension detected by the tension detection unit becomes equal to or greater than a first threshold value in a case where the tension detection unit is in the first mode and the tension of the sheet is increased toward a target value by the tension adjustment unit, the tension detection unit is switched to the second mode; The conveying device according to claim 1, characterized in that, when the tension detection unit is in the second mode and the tension adjustment means is used to reduce the sheet tension toward a target value, the tension detection unit is switched to the first mode when the tension detected by the tension detection unit becomes equal to or less than a second threshold value that is greater than the first threshold value.

7. the first threshold value is the same as the second lower limit value, The transport device according to claim 6 , wherein the second threshold value is the same as the first upper limit value.

8. the tension detection unit is configured to be switchable to a third mode in which tension between a third lower limit value that is greater than the first upper limit value and less than the second upper limit value, and a third upper limit value that is greater than the second upper limit value, is detectable; The conveying device according to claim 1 , wherein the control unit is capable of switching between the second mode and the third mode based on the tension detected by the tension detection unit.

9. The control unit when the tension detected by the tension detection unit becomes equal to or greater than a first threshold value in a case where the tension detection unit is in the first mode and the tension of the sheet is increased toward a target value by the tension adjustment unit, the tension detection unit is switched to the second mode; when the tension detected by the tension detection unit is equal to or less than a second threshold value that is greater than the first threshold value, and when the tension detection unit is in the second mode and the tension of the sheet is reduced toward a target value by the tension adjustment unit, the tension detection unit is switched to the first mode; when the tension detected by the tension detection unit is equal to or greater than a third threshold value that is greater than the second threshold value, the tension detection unit is switched to the third mode; and The conveying device according to claim 8, characterized in that, when the tension detection unit is in the third mode and the tension adjustment means is used to reduce the sheet tension toward a target value, the tension detection unit is switched to the second mode when the tension detected by the tension detection unit becomes equal to or less than a fourth threshold value that is greater than the third threshold value.

10. the first threshold value is the same as the second lower limit value, the second threshold value is the same as the first upper limit value, the third threshold value is the same value as the third lower limit value, The conveying device according to claim 9 , wherein the fourth threshold value is the same value as the second upper limit value.

11. a sheet information acquisition unit that acquires the type of sheet being conveyed; 2. The conveying device according to claim 1, wherein the first lower limit value, the first upper limit value, the second lower limit value, and the second upper limit value are individually determined in advance for each type of the sheet.

12. The conveying section includes a first pair of conveying rollers and a second pair of rollers downstream of the first pair of conveying rollers.

2. The conveying device according to claim 1, wherein the tension adjusting means adjusts the sheet tension by adjusting the speed of the second conveying roller pair.

13. A conveying device according to any one of claims 1 to 12; a recording unit that records an image on a sheet; A recording device comprising:

Images