Patent Application
20220363081
The present invention relates to a printing apparatus.
There is known a printing apparatus that performs printing on a print medium such as paper by discharging ink from a printhead while moving a carriage mounted with the printhead. With such a printing apparatus, demands for improving the productivity and the image quality of printing are increasing in recent years. Therefore, while the weight of the printhead increases due to the tendency of the printhead to become longer and have a higher density, the carriage is demanded to move with a high velocity and improve the positional accuracy.
As a driving method of the carriage, a method is known in which the carriage is connected to an endless belt (timing belt) and the carriage is moved by causing the belt to travel by a driving force of a motor. It is conceivable to employ a large high-output motor to increase the moving velocity of the carriage, but the market distribution scale of the large high-output motor is small and the cost thereof is high. Japanese Patent No. 3604994 discloses an apparatus in which one of two pulleys for causing the belt to travel is rotated by a stepper motor and the other one is rotated by a DC motor.
While the carriage is moved, a slack of the belt may be temporarily generated. This slack may cause an unstable operation of the carriage.
The present invention provides a technique that eliminates a slack of a belt and improves the operational stability of a carriage.
According to an aspect of the present invention, there is provided a printing apparatus comprising: a carriage mounted with a printing unit configured to perform printing on a print medium; a belt configured to reciprocate the carriage in a widthwise direction of the print medium; a first motor configured to drive the belt at one end in the widthwise direction; a second motor configured to drive the belt at the other end in the widthwise direction; and a control unit configured to control the first motor and the second motor, wherein the control unit performs first control by driving the first motor in which the carriage moves from a state in which the carriage is stopped, and in the first control, an output of the second motor is controlled from a first state lower than an output of the first motor to a second state higher than the first state.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Hereinafter, embodiments will be described in detail with reference to the attached drawings. Note, the following embodiments are not intended to limit the scope of the claimed invention. Multiple features are described in the embodiments, but limitation is not made an invention that requires all such features, and multiple such features may be combined as appropriate. Furthermore, in the attached drawings, the same reference numerals are given to the same or similar configurations, and redundant description thereof is omitted.
<Outline of Printing Apparatus>
Note that “printing” includes not only forming significant information such as characters and graphics but also forming images, figures, patterns, and the like on print media in a broad sense, or processing print media, regardless of whether the information formed is significant or insignificant or whether the information formed is visualized so that a human can visually perceive it. In addition, although in this embodiment, sheet-like paper is assumed as a “print medium” serving as a print target, sheet-like cloth, a plastic film, and the like may be used as print media.
The printing apparatus 1 includes a feeding unit 4. The feeding unit 4 holds a print media to be fed into the printing apparatus 1. In this embodiment, a roll sheet 100 is used as the print medium. However, the print medium may be a cut sheet. The roll sheet 100 is obtained by winding a sheet into a roll form around a cylindrical core. The roll sheet 100 has, for example, a width of 10 to 60 inches in the X direction.
The printing apparatus 1 includes a conveying unit 7. The conveying unit 7 is a sheet conveying mechanism that includes a conveying roller 70 and a pinch roller 71 pressed against the conveying roller 70. The sheet pulled out from the roll sheet 100 is fed to the rear side in the X direction. Then, the sheet is folded to the front side and reaches the conveying unit 7. The sheet is then nipped between the conveying roller 70 and the pinch roller 71 of the conveying unit 7 and conveyed on a platen 10 to the front side in the X direction.
The printing apparatus 1 includes a printhead 2 that prints an image by discharging ink to the sheet conveyed on the platen 10 by the conveying unit 7. The printhead 2 includes a plurality of nozzles which discharge ink. An energy element that generates energy for discharging ink by supply of power is arranged in each nozzle. The energy element is, for example, an electrothermal transducer such as a heater or a piezoelectric transducer such as a piezoelectric element. The printhead 2 can discharge different kinds of ink (for example, ink of a plurality of colors such as black (K), cyan (C), magenta (M), and yellow (Y)), and multiple nozzles are formed for each kind of ink.
Ink is supplied to the printhead 2 from an ink container 5. The ink container 5 includes a tank for each kind of ink, and ink is stored in the tank. Ink is supplied from the ink container 5 to the printhead 2 via a flexible tube (not shown) supported by a chain link 5a.
The printhead 2 is mounted on a carriage 3, and the printing apparatus 1 includes a carriage apparatus described below. The carriage 3 is moved by a driving unit 6 in the widthwise direction (Y direction) of the print medium. The driving unit 6 includes guide rails 63 and 64 extended parallel to the Y direction. The carriage 3 engages with the guide rails 63 and 64 so as to be guided in movement in the Y direction. The driving unit 6 includes pulleys 60R and 60L as an example of a plurality of rotation members. The pulleys 60R and 60L are spaced apart from each other in the Y direction and have the same specifications (outer diameter, weight, and the like). A timing belt 62, which is an example of an endless belt, is wound around the pulleys 60R and 60L. The carriage 3 is connected to the timing belt 62.
The driving unit 6 includes carriage motors 61R and 61L. The carriage motor 61R is a motor for driving the timing belt 62 at one end in the Y direction, and is a driving source for rotating the pulley 60R. The carriage motor 61L is a motor for driving the timing belt 62 at the other end in the Y direction, and is a driving source for rotating the pulley 60L. In this embodiment, the carriage motor 61R is configured to directly rotate the pulley 60R while the pulley 60R is connected to the output shaft of the carriage motor 61R. However, the carriage motor 61R may be configured to rotate the pulley 60R via a decelerator. Similarly, the carriage motor 61L is configured to directly rotate the pulley 60L while the pulley 60L is connected to the output shaft of the carriage motor 61L. However, the carriage motor 61L may be configured to rotate the pulley 60L via a decelerator. Each of the carriage motors 61R and 61L is, for example, a brushless DC motor and, in this embodiment, the carriage motors 61R and 61L are the same product. Accordingly, the carriage motors 61R and 61L have the same performance and characteristics during driving.
The carriage 3 can be moved by driving one or both of the carriage motors 61R and 61L to cause the timing belt 62 to travel. Further, by switching the rotation directions of the carriage motors 61R and 61L, the carriage 3 can be reciprocated in the Y direction. In this embodiment, it is possible to move the carriage 3 by outputs of two carriage motors 61R and 61L, so that the higher output can be obtained than in a case of driving by one carriage motor. Therefore, even if the carriage 3 is heavy, it can be moved at a higher velocity.
An encoder sensor 9 is mounted on the carriage 3. The encoder sensor 9 reads a linear scale (encoder scale) 8 extended in the Y direction and outputs a signal indicating the Y-direction position of the carriage 3. The linear scale 8 includes, for example, transmissive portions and light shielding portions repeatedly formed at predetermined constant intervals in the Y direction. The encoder sensor 9 is, for example, an optical sensor which includes a light emitting unit and a light receiving unit. The encoder sensor 9 outputs, as a detection signal, a light-receiving result of the light receiving unit which changes depending on whether light is received from the transmissive portion or the light shielding portion.
When the carriage 3 moves in the Y direction, the encoder sensor 9 can obtain a pulsed signal. By counting the number of pulses, the Y-direction position of the carriage 3 can be calculated. Further, the moving velocity of the carriage 3 can be calculated from the number of pulses per unit time. For example, assume that the transmissive portion and the light shielding portion of the linear scale 8 are repeated in 150 cycles per inch. Each time the carriage moves 1/150 inch, the encoder sensor 9 obtains a one-pulse signal. If three pulses are counted in a time of 500 μs, the velocity v of the carriage 3 can be calculated as v=( 3/150 inch)/500 μs=40 ips.
In a printing operation, the sheet is intermittently conveyed by the conveying unit 7 (stepped conveyance). While the conveyance of the sheet is stopped, the carriage 3 is moved in the main scanning direction (Y direction) and ink is discharged from the printhead 2 onto the sheet (printing scan). When printing for one scan ends, the conveying unit 7 conveys the sheet by a predetermined amount in the subscannig direction (a direction orthogonal to the main scanning direction). Then, printing scan is performed. By repeating printing scan and stepped conveyance of the sheet, an image is printed on the sheet. The sheet where image printing is completed is cut by a cutter mechanism (not shown).
<Control Apparatus>
With reference to
The main control unit 20 includes a processing unit 21, a storage unit 22, and an interface unit (I/F unit) 23, and controls the entire printing apparatus 1. The processing unit 21 is a processor represented by a CPU, and executes a program stored in the storage unit 22. The storage unit 22 is a storage device such as a RAM or a ROM, and stores programs and data.
The conveyance control unit 24 and the printing control unit 25 perform conveyance control and printing control, respectively, by following instructions of the main control unit 20. For example, similar to the main control unit 20, each of the control units 24 and 25 includes a processing unit, a storage unit, and an I/F unit. A drive circuit for driving the motor and the like are also included.
The conveyance control unit 24 controls a conveying motor 72 that rotates the conveying roller 70 to perform conveyance control of the sheet. Note that a detection result of the sensor that detects the rotation amount of the conveying motor 72 and a detection result of the sensor that detects the conveyance position of the sheet (both sensors are not shown) are input to the conveyance control unit 24, and the conveyance control unit 24 controls the conveying motor 72 based on these detection results.
The printing control unit 25 performs driving control of the carriage motors 61R and 61L (movement control of the carriage 3) and driving control of the printhead 2 (ink discharge control) based on a detection result of the encoder sensor 9.
<Movement Control of Carriage>
The carriage motors 61R and 61L are controlled independently. In this embodiment, driving control of the carriage motors 61R and 61L is PWM (Pulse Width Modulation) control. In PWM control, the output power is controlled by the ratio (duty ratio) of the energization time (ON time) per unit time.
The movement direction in the forward movement of the carriage 3 may be referred to as the forward direction, and the movement direction in the backward movement may be referred to as the backward direction. For the movement of the carriage 3 as described above, in this embodiment, it is possible to select the movement by the driving force of the carriage motor 61R alone, the movement by the driving force of the carriage motor 61L alone, and the movement by the driving forces of both of the carriage motors 61R and 61L.
The movement control of the carriage 3 in this embodiment is feedback control. At each of a large number of Y-direction positions of the carriage 3, a target velocity at the position is set in advance.
The acceleration start position, the stop target position, and the deceleration start position of the carriage 3 are determined in advance. In this embodiment, the Y-direction positions of the carriage 3 are roughly classified into an acceleration range, a constant velocity range, and a deceleration range. The carriage 3 is accelerated to a predetermined velocity V2, performs printing scan during the constant velocity range of the velocity V2, and then is decelerated and stops. The target velocity for each position can be set such that the velocity and operation of the carriage 3 moderately change without a sharp change.
During the movement of the carriage 3, the printing control unit 25 calculates the actual position and actual velocity of the carriage 3 from the detection results of the encoder sensor 9. The printing control unit 25 increases or decreases the duty ratio in accordance with the difference between the target velocity at the actual position and the actual velocity. For example, if the actual velocity has not reached the target velocity, the duty ratio is increased. To the contrary, if the actual velocity exceeds the target velocity, the duty ratio is decreased.
The rotation speed/torque characteristics of the carriage motors 61R and 61L shown in
A line L3 corresponds to the acceleration in a case of driving both the carriage motors 61R and 61L to accelerate the carriage 3 to the velocity V2. Even when the carriage motor 61R or 61L is solely driven, the carriage 3 can be accelerated up to the velocity V1 with the same acceleration. This also applies to a case of deceleration.
<Elimination of Slack of Belt>
When moving the carriage 3 from a stop state, a slack can be generated in the timing belt 62. This slack may cause an unstable operation of the carriage 3. A specific example will be described. As shown in
Assume a case in which, when the carriage 3 is moved forward as shown in
This also applies to a case in which the carriage 3 is moved backward as shown in
To prevent this, when starting the forward movement shown in
As exemplarily shown in
In step S1 of
In step S2 of
After switching driving of the carriage motor 61R alone to driving of both the carriage motors 61R and 61L in step S3, the duty ratio of PWM control of the carriage motor 61R may be equal to that of the carriage motor 61L. Upon the switching, for example, if the duty ratio of PWM control of the carriage motor 61R before the switching is α %, the duty ratio of each of the carriage motors 61R and 61L may be set to α/2%. Then, in accordance with the target velocity and the actual velocity of the carriage 3 thereafter, the duty ratios of the carriage motors 61R and 61L may be similarly increased or decreased.
With the control as described above, the velocity of the carriage 3 reaches the velocity V2. Then, the carriage 3 is moved at a constant velocity, and printing scan is performed. After that, if the position of the carriage 3 reaches the deceleration position, deceleration of the carriage 3 is started. In step S4 of
When switching driving of both the carriage motors 61R and 61L to driving of the carriage motor 61R alone in step S5, the duty ratio of PWM control of the carriage motor 61R may be doubled. For example, if the duty ratio of each of the carriage motors 61R and 61L is β %, the duty ratio of the carriage motor 61R may be set to 2×β %.
In step S6, based on a detection result of the encoder sensor 9, it is determined whether the carriage 3 has reached the stop position. If the carriage 3 has reached the stop position, the process advances to step S7 and the carriage motor 61R is stopped. After the deceleration of the carriage 3 is started, during the period from the velocity V1 to the stop, the pulley 60R is driving-rotated and the pulley 60L is driven-rotated. Therefore, upon the stop, the timing belt 62 stops while an appropriate tension is applied to the travel region 62a. In the next backward movement, generation of a slack in the travel region 62a can be suppressed and the responsiveness of the carriage 3 can be improved.
Next,
In step S11 of
In step S12 of
With the control as described above, the velocity of the carriage 3 reaches the velocity V2. Then, the carriage 3 is moved at a constant velocity, and printing scan is performed. After that, if the position of the carriage 3 reaches the deceleration position, deceleration of the carriage 3 is started. In step S14 of
In step S16, based on a detection result of the encoder sensor 9, it is determined whether the carriage 3 has reached the stop position. If the carriage 3 has reached the stop position, the process advances to step S17 and the carriage motor 61L is stopped (
In the above-described embodiment, when accelerating the carriage 3, switching from driving of one carriage motor alone to driving of both two carriage motors on condition that the velocity of the carriage 3 has reached V1. However, the threshold velocity is not limited to V1, and a velocity lower than V1 may be used. Similarly, when decelerating the carriage 3, the threshold velocity for switching from driving of both two carriage motors to driving of one carriage motor alone is not limited to V1, and a velocity lower than V1 may be used. Different threshold velocities may be used for the acceleration and the deceleration. For example, if the responsiveness of the carriage 3 at the time of acceleration is low, the threshold velocity for the acceleration may be higher than the threshold velocity for the deceleration.
In the above-described embodiment, when accelerating the carriage 3, driving of one carriage motor alone is performed until the velocity of the carriage 3 reaches V1. However, driving of both two carriage motors may be performed from the start of movement of the carriage 3. In forward movement, the output (torque here) of the carriage motor 61L may be controlled from a state lower than the output of the carriage motor 61R to a state higher than the lower state. Switching from the low state to the high state may be performed based on the velocity of the carriage 3. If the velocity of the carriage 3 has reached V1, the switching may be performed. In the low state, for example, the duty ratio of PWM control of the carriage motor 61L may be set equal to or lower than half the duty ratio of the carriage motor 61R. In the high state, for example, the duty ratio of PWM control of the carriage motor 61L may be set equal to the duty ratio of the carriage motor 61R. Similarly, in backward movement, the output of the carriage motor 61R may be controlled from a state lower than the output of the carriage motor 61L to a state higher than the lower state.
In the above-described embodiment, when decelerating the carriage 3, driving of one carriage motor alone is performed until the velocity of the carriage 3 reaches V1. However, driving of both two carriage motors may be performed until the carriage 3 stops. In forward movement, from the start of deceleration of the carriage 3 to the stop, the output (torque here) of the carriage motor 61L may be controlled to a state lower than the output of the carriage motor 61R. The timing of setting the output of the carriage motor 61L in the lower state may be based on whether the carriage 3 has decelerated to the above-described threshold velocity. The lower state may be a state in which the rotation direction of the carriage motor 61L is set in the reverse direction (the direction for moving the carriage 3 in the backward direction). Similarly, in backward movement, from the start of deceleration of the carriage 3 to the stop, the output (torque here) of the carriage motor 61R may be controlled to a state lower than the output of the carriage motor 61L. The timing of setting the output of the carriage motor 61R in the lower state may be based on whether the carriage 3 has decelerated to the above-described threshold velocity. Further, the lower state may be a state in which the rotation direction of the carriage motor 61R is set in the reverse direction (the direction for moving the carriage 3 in the forward direction).
In the above-described embodiment, an example has been described in which, as forward movement, the carriage 3 moves from the right end of the movement range to the left end, but similar control can also be employed in a case in which the carriage 3 moves from a midpoint of the movement range to the left end or a case in which the carriage 3 moves from the right end of the movement range to a midpoint. Similarly, an example has been described in which, as backward movement, the carriage 3 moves from the left end of the movement range to the right end, but similar control can also be employed in a case in which the carriage 3 moves from a midpoint of the movement range to the right end or a case in which the carriage 3 moves from the left end of the movement range to a midpoint.
Embodiment(s) of the present invention can also be realized by a computer of a system or apparatus that reads out and executes computer executable instructions (e.g., one or more programs) recorded on a storage medium (which may also be referred to more fully as ‘non-transitory computer-readable storage medium’) to perform the functions of one or more of the above-described embodiment(s) and/or that includes one or more circuits (e.g., application specific integrated circuit (ASIC)) for performing the functions of one or more of the above-described embodiment(s), and by a method performed by the computer of the system or apparatus by, for example, reading out and executing the computer executable instructions from the storage medium to perform the functions of one or more of the above-described embodiment(s) and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiment(s). The computer may comprise one or more processors (e.g., central processing unit (CPU), micro processing unit (MPU)) and may include a network of separate computers or separate processors to read out and execute the computer executable instructions. The computer executable instructions may be provided to the computer, for example, from a network or the storage medium. The storage medium may include, for example, one or more of a hard disk, a random-access memory (RAM), a read only memory (ROM), a storage of distributed computing systems, an optical disk (such as a compact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™), a flash memory device, a memory card, and the like.
While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2021-081835, filed May 13, 2021, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2021-081835 | May 2021 | JP | national |
