Printing device

Abstract

[Problem] To apply proper tension to a medium with a simple configuration. [Solution] A printing device according to the present disclosure comprises: a conveyance unit having a movable head for discharging a liquid to a medium, a conveyance member, and a conveyance motor for conveying the medium by rotating the conveyance member; a winding unit having a winding member for winding the medium to which the liquid has been discharged, and a winding motor for winding the medium by rotating the winding member; and a control part for alternately repeating a liquid discharge operation for discharging the liquid from the head and a conveyance operation for conveying the medium by the conveyance unit. The control part changes a current flowing to the winding motor on the basis of a current value of the conveyance motor at a timing when the conveyance unit is not conveying the medium.

Description

printing device

[0001] The present invention relates to a printing device.

[0002] Japanese Patent Application Laid-Open No. 2003-144992 describes a media take-up device that takes up a long strip of media (medium) fed from a printer into a roll.

[0003] Japanese Patent Application Laid-Open No. 2006-347640

[0004] Patent Document 1 describes that in order to apply an appropriate tension to the medium, the rotation of the winding tube that winds the medium is detected by a rotation sensor, and the torque applied to the winding tube from the motor is adjusted via a torque limiter. However, providing a rotation sensor or torque limiter increases the cost of the device.

[0005] An object of the present invention is to apply appropriate tension to a medium with a simple configuration.

[0006] The main invention for achieving the above object is a printing device comprising: a movable head that ejects liquid onto a medium; a transport unit having a transport member and a transport motor for rotating the transport member to transport the medium; a winding unit having a winding member that winds up the medium onto which the liquid has been ejected and a winding motor for rotating the winding member to wind up the medium; and a control unit that alternately repeats a liquid ejection operation in which the liquid is ejected from the head and a transport operation in which the transport unit transports the medium, wherein the control unit changes the current flowing to the winding motor based on the current value of the transport motor at a time when the transport unit is not transporting the medium.

[0007] Other features of the present invention will become apparent from the description of this specification.

[0008] According to the present invention, it is possible to apply an appropriate tension to a medium with a simple configuration.

[0009] FIG. 1 is a schematic diagram of the overall configuration of the printing device 1. FIG. 2 is a block diagram of the printing device 1. FIGS. 3A to 3F are explanatory diagrams of the printing operation. FIGS. 4A and 4B are explanatory diagrams of a reference example in which the current of the winding motor 52 is kept constant. FIG. 5 is a control block diagram of the transport motor 42 and the winding motor 52. FIG. 6 is an explanatory diagram of the control flow of the winding motor 52. FIG. 7 is an explanatory diagram of changes in the current of the winding motor 52. FIG. 8 is an explanatory diagram of the control flow of a modified example of the winding motor 52.

[0010] 1 is a schematic explanatory diagram of the overall configuration of a printing device 1. FIG. 2 is a block diagram of the printing device 1.

[0011] The printing device 1 is a device that prints on a medium 5. In this example, the printing device 1 is an inkjet printer. The printing device 1 has a supply unit 10, a head 20, a carriage unit 30, a transport unit 40, a winding unit 50, and a control unit 60.

[0012] The supply unit 10 is a member that supplies the medium 5. The medium 5 is a long, strip-shaped sheet member, and is the member to be printed on (printed medium). In this example, the medium 5 is paper (roll paper), but it is not limited to paper and can also be, for example, film or cloth. Roll paper, which is formed by previously winding the medium 5 into a roll, is set in the supply unit 10, and paper pulled from the roll paper is supplied to the head 20.

[0013] The head 20 ejects liquid onto the medium 5. The head 20 is mounted on a carriage 31 and is movable in the scanning direction (the direction perpendicular to the plane of the paper in FIG. 1 ). A plurality of nozzle rows 21 (not shown in FIGS. 1 and 2 ; see FIG. 3 ) are provided on the underside of the head 20 (the surface facing the medium 5). The nozzle rows 21 have a plurality of nozzles aligned along the transport direction, and the plurality of nozzle rows 21 are aligned along the scanning direction. In this example, the liquid ejected from the nozzles is ink, and the ink ejected from the nozzles lands on the medium 5 to form dots on the medium 5, thereby forming an image on the medium 5. However, the liquid ejected from the nozzles does not have to be ink; for example, it may be a treatment liquid for performing surface treatment on the medium 5.

[0014] The carriage unit 30 moves the carriage 31 in the scanning direction. The carriage unit 30 has a carriage 31 and a carriage motor 32. The carriage 31 is equipped with the head 20 and is configured to be movable in the scanning direction. The carriage motor 32 is a drive source that moves the carriage 31. The carriage unit 30 has a transmission mechanism (not shown; for example, a gear, pulley, belt, etc.) for transmitting the driving force of the carriage motor 32 to the carriage 31. When the carriage unit 30 moves the carriage 31 in the scanning direction, the head 20 moves in the scanning direction.

[0015] The transport unit 40 transports the medium 5. The transport unit 40 has a transport member 41 and a transport motor 42. The transport member 41 is a member that transports the medium 5 by rotating, such as a transport roller. The transport motor 42 is a drive source that rotates the transport member 41. The transport unit 40 has a transmission mechanism (not shown; for example, a gear) for transmitting the driving force of the transport motor 42 to the transport member 41. The transport unit 40 rotates the transport member 41, thereby transporting the medium 5 in the transport direction.

[0016] In the following description, the direction in which the medium 5 is transported is referred to as the "transport direction," the side that supplies the medium 5 is referred to as the "upstream (upstream side)," and the opposite side is referred to as the "downstream (downstream side)." The transport direction is also referred to as the "sub-scanning direction."

[0017] The winding unit 50 winds up the printed medium 5. The winding unit 50 has a winding member 51 and a winding motor 52. The winding member 51 is a member that rotates, such as a winding tube, to wind up the medium 5. The winding motor 52 is a drive source that rotates the winding member 51. The winding unit 50 also has a transmission mechanism (not shown; for example, a gear) that transmits the driving force of the winding motor 52 to the winding member 51. When the winding unit 50 rotates the winding member 51, the printed medium 5 is wound into a roll around the winding member 51. When the winding unit 50 rotates the winding member 51, tension is applied to the medium 5, preventing slack from occurring in the medium 5. The winding motor 52 is controlled to apply an appropriate tension to the medium 5. Control of the winding motor 52 will be described later.

[0018] The control unit 60 is responsible for controlling the printing device 1. The control unit 60 has, for example, an arithmetic processing unit and a storage device (not shown), and the arithmetic processing unit executes programs stored in the storage device. The control unit 60 controls each part of the printing device 1 based on print commands from an external computer, causing the printing device 1 to perform a printing operation.

[0019] 3A to 3F are explanatory diagrams of the printing operation. Note that the head 20 has multiple nozzle rows 21 aligned in the scanning direction, but for the sake of explanation, only one nozzle row 21 is shown here.

[0020] The control unit 60 moves the carriage 31 in the scanning direction, thereby ejecting liquid from the nozzles while moving the head 20 (nozzle row 21) in the scanning direction, thereby forming dots on the medium 5. In the following description, the operation of ejecting liquid from the head 20 may be referred to as the "liquid ejection operation." In FIG. 3B, the area where dots can be formed in one liquid ejection operation (printable area) is hatched. Note that while the liquid ejection operation is being performed, the control unit 60 controls the transport unit 40 so that the medium 5 does not move in the transport direction. In the following description, controlling the transport unit 40 so that the medium 5 does not move in the transport direction may be referred to as "stationary control."

[0021] After the liquid ejection operation, the control unit 60 transports the medium 5 in the transport direction by a predetermined transport distance, as shown in Figures 3C and 3D. In the following description, the operation of transporting the medium 5 in the transport direction may be referred to as the "transport operation." The transport operation moves the downstream end of the printable area of ​​the previous liquid ejection operation downstream of the printable area of ​​the next liquid ejection operation (see Figures 3E and 3F). The transport operation also supplies unused areas of the medium 5 to the printable area of ​​the next liquid ejection operation. In the following description, controlling the transport unit 40 so that the medium 5 is transported in the transport direction may be referred to as "transport control."

[0022] After the transport operation, the control unit 60 causes the next liquid ejection operation to be performed, as shown in Figures 3E and 3F. In this way, the control unit 60 performs printing on the medium 5 by alternately repeating the liquid ejection operation and the transport operation. In the following description, the operation of alternately repeating the liquid ejection operation and the transport operation may be referred to as a "printing operation." During the printing operation, the control unit 60 controls the transport unit 40 so as to alternately repeat stationary control and transport control.

[0023] 4A and 4B are explanatory diagrams of a reference example in which the current of the winding motor 52 is constant. Fig. 4A is an explanatory diagram in the case where the winding amount is small. Fig. 4B is an explanatory diagram in the case where the winding amount is large.

[0024] As a reference example, the current of the winding motor 52 is kept constant (I０ ) will be described. The torque of the take-up motor 52 is approximately proportional to the current. On the other hand, as shown in FIG. 4B , as the amount of medium 5 wound around the take-up member 51 (take-up amount) increases, the diameter of the medium 5 wound around the take-up member 51 (take-up diameter) increases, and as a result, the force required to rotate the take-up member 51 increases (in other words, the moment of inertia increases). Therefore, when the current of the take-up motor 52 is constant, as the amount of medium 5 wound around the take-up member 51 (take-up amount) increases, the tension of the medium 5 applied by the take-up motor 52 decreases. In other words, the tension F' of the medium 5 shown in FIG. 4B is smaller than the tension F of the medium 5 shown in FIG. 4A (F'<F).

[0025] To maintain a constant tension applied to the medium 5 by the winding unit 50, it is necessary to increase the current of the winding motor 52 as the winding amount increases. However, if an additional sensor is added to detect the winding amount in order to determine the current value to increase as the winding amount increases, the cost of the winding unit 50 increases.

[0026] 4A and 4B , when the control unit 60 controls the transport unit 40 to remain stationary so that the medium 5 does not move in the transport direction, the control unit 60 controls the transport motor 42 to balance the tension of the medium 5. Therefore, when the tension of the medium 5 changes as the take-up amount changes, the current of the transport motor 42 changes. Utilizing this phenomenon, the control unit 60 of this embodiment controls the current of the take-up motor 52 so that the appropriate tension is applied to the medium 5.

[0027] <Winding Control> FIG. 5 is a control block diagram of the conveyance motor 42 and the winding motor 52. As shown in FIG.

[0028] The control unit 60 includes a main control unit 61 , a transport control unit 62 , and a winding control unit 63 .

[0029] The main control unit 61 outputs command signals to each part of the printing device 1 to control each part. Here, the main control unit 61 outputs a command signal to the transport control unit 62 to control the transport unit 40 (also, although not shown, the main control unit 61 also outputs command signals to the head 20 and carriage unit 30 to execute printing operations, thereby controlling the head 20 and carriage unit 30). The main control unit 61 also outputs a reset signal to the take-up control unit 63. Note that when the user removes the medium 5 from the take-up member 51 (when the take-up member 51 begins to rewind the medium 5), the main control unit 61 outputs a reset signal to the take-up control unit 63.

[0030] The transport control unit 62 controls the transport motor 42. For example, the transport control unit 62 is a driver that controls the transport motor 42. The transport control unit 62 controls the current of the transport motor 42 based on a command signal from the main control unit 61. The transport motor 42 (or the transport member 41) is provided with a rotary encoder 43. The rotary encoder 43 detects the rotation position and rotation speed of the transport motor 42 (or the transport member 41) and outputs a detection signal to the transport control unit 62. The transport control unit 62 feedback-controls the current of the transport motor 42 based on the command signal from the main control unit 61 and the detection signal from the rotary encoder 43.

[0031] For example, when transport control is performed, the main control unit 61 outputs a command signal to the transport control unit 62 to rotate the transport member 41 by a predetermined rotation amount. As a result, the transport control unit 62 controls the current of the transport motor 42 so that the transport member 41 rotates by the predetermined rotation amount (so that the medium 5 is transported by a predetermined transport amount) based on the command signal from the main control unit 61 and the detection signal from the rotary encoder 43. In the following description, the command signal that the main control unit 61 outputs to the transport control unit 62 during transport control may be referred to as a "transport command signal."

[0032] Furthermore, for example, when stillness control is performed, the main control unit 61 outputs a command signal to the transport control unit 62 to prevent the transport member 41 from rotating. As a result, the transport control unit 62 controls the current of the transport motor 42 based on the command signal and the detection signal from the rotary encoder 43 so that the transport member 41 is held at a predetermined rotational position without rotating (so that the medium 5 does not move in the transport direction). In the following description, the command signal output by the main control unit 61 to the transport control unit 62 during stillness control may be referred to as a "stillness command signal."

[0033] The winding control unit 63 controls the winding motor 52. The winding control unit 63 is, for example, a driver that controls the winding motor 52. As will be described later, the winding control unit 63 changes the current flowing through the winding motor 52 based on the current of the conveyance motor 42. The winding control unit 63 stores an initial value, an additional value, and a set value. The winding control unit 63 sets the set value based on the initial value and the additional value (described later).

[0034] The winding control unit 63 has a setting unit 63A. A setting value is set in the setting unit 63A. The winding control unit 63 is configured to cause a current corresponding to the setting value set in the setting unit 63A to flow to the winding motor 52. The setting unit 63A holds the setting value until it is updated. Therefore, a current corresponding to the setting value set in the setting unit 63A continues to flow to the winding motor 52. The winding control unit 63 changes the setting value set in the setting unit 63A to change the current flowing to the winding motor 52. Note that other methods for changing the current flowing to the winding motor 52 may also be used.

[0035] As shown in FIG. 5 , the transport unit 40 is provided with a current detection unit 44. The current detection unit 44 detects the current of the transport motor 42. For the sake of explanation, in FIG. 5 , the current detection unit 44 is shown as a separate block from the transport control unit 62 and the transport motor 42; however, the current detection unit 44 is typically built into the transport control unit 62 (driver) or the transport motor 42. This makes it possible to detect the current of the transport motor 42 without increasing costs. The current detection unit 44 outputs the detection result (the current value of the transport motor 42) to the rewinding control unit 63. Note that the current value of the transport motor 42 that the current detection unit 44 outputs to the rewinding control unit 63 may be an analog value or a digital value.

[0036] 5, the main control unit 61 also outputs the command signal (convey command signal or stationary command signal) that is output to the transport control unit 62 to the rewinding control unit 63. The rewinding control unit 63 can detect the timing when transport control or stationary control is being performed based on the command signal from the main control unit 61. As will be described later, the rewinding control unit 63 detects the timing when the medium 5 is not being transported based on the command signal (stationary command signal). As long as the rewinding control unit 63 can detect the timing when the medium 5 is not being transported, a signal other than the command signal may be input to the rewinding control unit 63.

[0037] 6 is an explanatory diagram of the control flow of the take-up motor 52. Each process in the diagram is executed by the take-up control unit 63. The main control unit 61 executes the printing operation (see FIG. 3) described above in parallel with the control flow of the take-up motor 52 in the diagram. When the take-up control unit 63 receives a reset signal from the main control unit 61, it starts each process in the diagram.

[0038] First, the take-up control unit 63 sets the setting value to an initial value (S001). That is, the take-up control unit 63 sets the initial value in the setting unit 63A. The initial value is a pre-stored default value. The take-up control unit 63 is configured to output a current to the take-up motor 52 according to the setting value set in the setting unit 63A. Therefore, a current according to the initial value (setting value) continues to flow to the take-up motor 52 until the setting value is updated. When the medium 5 is hardly wound around the take-up member 51, an appropriate tension is applied to the medium 5 when a current according to the initial value flows to the take-up motor 52. In other words, the initial value is set so that an appropriate tension is applied to the medium 5 when the medium 5 is hardly wound around the take-up member 51.

[0039] After a predetermined time has elapsed (YES in S002), the take-up control unit 63 detects the current value of the transport motor 42 when the medium 5 is not being transported (S003). In S003, the take-up control unit 63 obtains the current value of the transport motor 42 from the current detection unit 44 when the main control unit 61 outputs a stop command signal (when the liquid ejection operation is being performed).

[0040] Next, the take-up control unit 63 compares the current value of the transport motor 42 with a predetermined threshold value (S004). The threshold value is set so that the current value of the transport motor 42 during stationary control when an appropriate tension is applied to the medium 5 is greater than the threshold value.

[0041] If the current value of the transport motor 42 is greater than the threshold value (NO in S004), the take-up control unit 63 returns to S002 without updating the setting value. Note that if the current value of the transport motor 42 is greater than the threshold value (NO in S004), it is considered that the take-up unit 50 is applying appropriate tension to the medium 5.

[0042] On the other hand, if the current value of the carry motor 42 is less than the threshold value (YES in S004), the take-up control unit 63 adds a predetermined additional value to the current setting value to update the setting value (S005), and returns to S002. Increasing the setting value in the process of S005 increases the current flowing to the take-up motor 52, increasing the tension applied to the medium 5, and as a result, an appropriate tension is applied to the medium 5. When the setting value is updated, a current corresponding to the setting value continues to flow to the take-up motor 52 until the next setting value update.

[0043] The rewinding control unit 63 repeats the processes of S002 to S005 at predetermined time intervals. The predetermined time for S002 is set to "1 minute," and the rewinding control unit 63 repeats the processes from S003 onward at one minute intervals. However, the predetermined time for S002 may be another time interval.

[0044] 7 is an explanatory diagram of changes in the current of the take-up motor 52 when the control flow shown in FIG. 6 is executed. The horizontal axis in the diagram represents the amount of medium 5 taken up by the take-up member 51 (take-up amount). The vertical axis in the diagram represents the magnitude of the current flowing through the take-up motor 52 (the current value of the take-up motor 52). Note that the horizontal axis in the diagram can also be considered to represent the diameter of the medium 5 taken up by the take-up member 51 (the take-up diameter). Furthermore, because the torque of the take-up motor 52 is approximately proportional to the current, the vertical axis in the diagram can also be considered to represent the torque of the take-up motor 52.

[0045] The control unit 60 controls the printing operation shown in FIG. 3 (an operation in which a liquid ejection operation and a transport operation are alternately repeated) in parallel with the control flow of the take-up motor 52 shown in FIG. 6 . While the liquid ejection operation is being performed, the control unit 60 controls the transport unit 40 to remain stationary so that the medium 5 does not move in the transport direction, and the take-up unit 50 applies appropriate tension to the medium 5. This allows dots to be formed on the medium 5 to which appropriate tension has been applied. During the transport operation, when the transport unit 40 transports the medium 5 by a predetermined transport amount, the drive force of the take-up motor 52 rotates the take-up member 51 in the take-up direction, and a length of the medium 5 corresponding to the transport amount is taken up by the take-up member 51. As the transport operation is repeated, the amount of medium 5 taken up by the take-up member 51 (take-up amount) gradually increases.

[0046] As the amount of medium 5 wound around the winding member 51 (winding amount) gradually increases, the force required to rotate the winding member 51 increases, and the tension applied to the medium 5 by the winding motor 52 gradually decreases (see FIG. 4B ). However, by repeating steps S002 through S005 at predetermined intervals, the winding control unit 63 updates the set value before the tension of the medium 5 becomes insufficient, and increases the current flowing to the winding motor 52 by an amount corresponding to the additional value. As shown in FIG. 7 , the current value of the winding motor 52 (torque of the winding motor 52) increases stepwise as the winding amount (winding diameter) increases. The increase in the current value of the winding motor 52 corresponds to the additional value added in S005. In this embodiment, the current of the winding motor 52 can be increased as the winding amount increases, thereby maintaining an appropriate tension applied to the medium 5.

[0047] Because liquid ejection operations are frequently and repeatedly performed during printing operations, the take-up control unit 63 can execute the process of S003 (processing to detect the current of the transport motor 42 when the transport unit 40 is not transporting the medium 5) at the timing when liquid ejection operations are performed. This allows the setting value to be updated during printing operations, and the tension applied to the medium 5 during printing operations can be maintained appropriately. Note that the timing when the transport unit 40 is not transporting the medium 5 refers to when the head 20 is performing a liquid ejection operation while the carriage 31 is moving in the scanning direction. When performing liquid ejection operations, the tension applied to the medium 5 is maintained appropriately, so the process of S003 (processing to detect the current of the transport motor 42 when the transport unit 40 is not transporting the medium 5) is executed at the timing when liquid ejection operations are performed.

[0048] 8 is an explanatory diagram of a control flow of a modified example of the winding motor 52. The processes in S001 to S003 and S005 in the diagram are the same as the processes in the control flow shown in FIG.

[0049] In this modification, after detecting the current value of the transport motor 42 (S003), the tension of the medium 5 is calculated (S004A) based on the current value of the transport motor 42. Note that the take-up control unit 63 has a predefined function that uses the current value of the transport motor 42 as an input value and the tension of the medium 5 as an output value.

[0050] Next, the rewinding control unit 63 compares the tension of the medium 5 calculated in S004A with a predetermined threshold value (S004B). If the tension of the medium 5 is greater than the threshold value (YES in S004B), the process returns to S002 without updating the set value. On the other hand, if the tension of the medium 5 is less than the threshold value (NO in S004B), the rewinding control unit 63 adds a predetermined additional value to the current set value to update the set value (S005), and the process returns to S002. Increasing the set value in S005 increases the current flowing through the rewinding motor 52, and increases the tension applied to the medium 5. In this modified example, as shown in FIG. 7, the current to the rewinding motor 52 can be increased as the rewinding amount increases, thereby maintaining an appropriate tension applied to the medium 5.

[0051] Summary The printing device 1 includes a head 20, a transport unit 40 having a transport member 41 and a transport motor 42, a winding unit 50 having a winding member 51 and a winding motor 52, and a control unit 60 that alternately repeats a liquid ejection operation and a transport operation. In a printing device 1 configured as described above, if the current of the winding motor 52 is constant, as the amount of medium 5 wound around the winding member 51 (winding amount) increases, the tension applied to the medium 5 by the winding motor 52 decreases, and the medium 5 is no longer imparted with appropriate tension. Therefore, the control unit 60 of this embodiment changes the current flowing to the winding motor 52 based on the current value of the transport motor 42 when the transport unit 40 is not transporting the medium 5. This makes it possible to impart appropriate tension to the medium 5 by utilizing the phenomenon that the current to the transport motor 42 changes when the tension of the medium 5 changes with a change in the winding amount.

[0052] ===Other Embodiments===The above embodiments are presented as examples and do not limit the scope of the invention. The above configurations can be implemented in appropriate combinations, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The above embodiments and their modifications are included in the scope and spirit of the invention, as well as in the inventions described in the claims and their equivalents.

[0053] REFERENCE SIGNS LIST 1 Printing device, 5 Medium, 10 Supply unit, 20 Head, 21 Nozzle row, 30 Carriage unit, 31 Carriage, 32 Carriage motor, 40 Transport unit, 41 Transport member, 42 Transport motor, 43 Rotary encoder, 44 Current detection unit, 50 Winding unit, 51 Winding member, 52 Winding motor, 60 Control unit, 61 Main control unit, 62 Transport control unit, 63 Winding control unit, 63A Setting unit

Claims

1. A printing device comprising: a movable head which ejects liquid onto a medium; a transport unit having a transport member and a transport motor for rotating the transport member to transport the medium; a winding unit having a winding member which winds up the medium onto which the liquid has been ejected, and a winding motor for rotating the winding member to wind up the medium; and a control unit which alternately repeats a liquid ejection operation of ejecting the liquid from the head and a transport operation of transporting the medium by the transport unit, wherein the control unit changes the current flowing to the winding motor based on the current value of the transport motor at a time when the transport unit is not transporting the medium.

2. A printing device according to claim 1, wherein the control unit increases the current flowing to the take-up motor when the current value of the transport motor is smaller than a predetermined threshold value.

3. A printing device as described in claim 1, wherein the control unit calculates the tension of the medium based on the current value of the transport motor at a time when the transport unit is not transporting the medium, and increases the current flowing to the winding motor when the tension is smaller than a predetermined threshold value.

4. A printing device according to any one of claims 1 to 3, characterized in that the control unit detects the current value of the transport motor at the timing when the liquid ejection operation is performed.

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