Patent Grant
9597900
Field of the Invention
The present invention relates to a printing apparatus.
Description of the Related Art
As a method of increasing the printing speed of a printing apparatus, successive overlapped conveyance of printing media has been proposed. Successive overlapped conveyance indicates a conveyance method of conveying a plurality of printing media while the leading edge of the succeeding printing medium overlaps the trailing edge of the preceding printing medium when images are successively printed on the printing media (for example, Japanese Patent Laid-Open No. 2000-15881). Successive overlapped conveyance makes it possible to further increase the printing speed, as compared with a conveyance method of starting to feed the succeeding printing medium after the end of printing of the preceding medium or a conveyance method of successively conveying the printing media while decreasing the gap between the printing media.
A pair of rollers are generally used to convey a printing medium. The pair of rollers include a driving roller and a driven roller pressed against the driving roller. The pair of rollers nip and convey a printing medium, and the conveyance amount of the printing medium is controlled by controlling the rotation amount of the driving roller.
In successive overlapped conveyance, the pair of rollers nip and convey two printing media. In this case, the thickness of a conveyance target is different from that when one printing medium is nipped and conveyed. Also, the two printing media may slip. Therefore, the conveyance accuracy of the printing media may decrease, resulting in degradation in printing quality.
The present invention provides a technique of increasing the printing speed while suppressing degradation in printing quality.
According to an aspect of the present invention, there is provided a printing apparatus comprising: a feeding unit configured to feed a printing medium stacked on a stacking unit; a pair of rollers configured to nip the printing medium and to convey the printing medium fed by the feeding unit; a printing unit configured to print on the printing medium conveyed by the pair of rollers; and a control unit configured to control the feeding unit and the conveying unit, wherein the control unit can execute successive overlapped conveyance in which the pair of rollers nip an overlapping portion between a trailing edge of a preceding printing medium and a leading edge of a succeeding printing medium and convey the preceding printing medium and the succeeding printing medium, and the control unit executes the successive overlapped conveyance at least on condition that printing of the preceding printing medium by the printing unit has ended.
Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).
Note that the term “printing” not only includes the formation of significant information such as characters and graphics, but also broadly includes the formation of images, figures, patterns, and the like on a printing medium, or the processing of the medium, regardless of whether they are significant or insignificant and whether they are so visualized as to be visually perceivable by humans. Also, sheet-like paper is assumed as a “printing medium” in this embodiment, but cloth, plastic film, and the like may be used as printing media. A sheet-like printing medium will be referred to as a printing sheet hereinafter.
Prior to a description of the operation of the printing apparatus 100, the arrangement of the printing apparatus 100 will be described with reference to a state ST1 of
The printing unit includes a printhead 7 and a carriage 10. The printhead 7 prints on the printing sheet 1. In this embodiment, the printhead 7 is an inkjet printhead which prints on the printing sheet 1 by discharging ink. A platen 8 which supports the reverse surface of the printing sheet 1 is arranged at a position facing the printhead 7. A carriage 10 incorporates the printhead 7 and moves in a direction intersecting a conveyance direction.
The conveyance apparatus is broadly divided into a feeding mechanism, conveying mechanism, and a discharging mechanism. The feeding mechanism feeds the printing sheet 1 stacked on the feeding tray 11 to the conveying mechanism. The conveying mechanism conveys the fed printing sheet 1 to the discharging mechanism. The discharging mechanism conveys the printing sheet 1 outside the printing apparatus 100. Conveyance of the printing sheet 1 being printed is mainly performed by the conveying mechanism. In this way, the printing sheet 1 is sequentially conveyed by the feeding mechanism, conveying mechanism, and discharging mechanism. The feeding mechanism side will be referred to as the upstream side of the conveyance direction and the discharging mechanism side will be referred to as the downstream side of the conveyance direction.
The feeding mechanism includes a pickup roller 2, a feeding roller 3, and a feeding driven roller 4. The pickup roller 2 abuts against the top printing sheet 1 stacked on the feeding tray 11 to pick it up. The feeding roller 3 feeds the printing sheet 1 picked up by the pickup roller 2 toward the downstream side of the conveyance direction. The feeding driven roller 4 is biased and pressed against the feeding roller 3 by an elastic member (for example, a spring) (not shown) to nip the printing sheet 1 with the feeding roller 3, thereby feeding the printing sheet 1.
As shown in
Referring back to
A conveyance guide 15 for guiding conveyance of the printing sheet 1 is provided in a conveyance section between a nip portion (to be referred to as a feeding nip portion hereinafter) formed by the feeding roller 3 and feeding driven roller 4 and a nip portion (to be referred to as a conveyance nip portion hereinafter) formed by the conveyance roller 5 and pinch roller 6.
The discharging mechanism includes a discharge roller 9 and spurs 12 and 13. The discharge roller 9 discharges the printing sheet 1 printed by the printhead 7 to the outside of the apparatus. The spurs 12 and 13 rotate while they are in contact with the printing surface of the printing sheet 1 printed by the printhead 7. The spur 13 on the downstream side is biased and pressed against the discharge roller 9 by an elastic member (for example, a spring) (not shown). No discharge roller 9 is arranged at a position facing the spur 12 on the upstream side. The spur 12 is used to prevent the floating of the printing sheet 1, and is also referred to as a pressing spur.
The printing apparatus 100 includes a sheet detection sensor 16. The sheet detection sensor 16 detects the leading edge and trailing edge of the printing sheet 1, and is, for example, an optical sensor. The sheet detection sensor 16 is provided downstream of the feeding roller 3 in the conveyance direction. A sheet pressing lever 17 makes the leading edge of the succeeding printing sheet 1 (to be referred to as the succeeding printing medium or succeeding sheet hereinafter) overlap the trailing edge of the preceding printing sheet 1 (to be referred to as the preceding printing medium or the preceding sheet hereinafter) by pressing the trailing edge. Note that the leading edge and trailing edge of the printing sheet 1 indicate the edge on the downstream side and the edge on the upstream side of the conveyance direction, respectively. The sheet pressing lever 17 is biased by an elastic member (for example, a spring) (not shown) around a rotating shaft 17b in a counterclockwise direction in
An example of the arrangement of a printing system including the control unit of the printing apparatus 100 and an information processing apparatus 214 capable of transmitting printing data to the printing apparatus 100 will be described with reference to
The printing apparatus 100 includes an MPU 201. The MPU 201 can control the operation of each component of the printing apparatus 100, and performs data processing and the like. As will be described later, the MPU 201 can control conveyance of the printing sheets 1 so that the trailing edge of the preceding sheet and the leading edge of the succeeding sheet overlap each other. A ROM 202 stores data and programs to be executed by the MPU 201. A RAM 203 temporarily stores processing data to be executed by the MPU 201 and printing data received from the information processing apparatus 214. Note that other storage devices can be used instead of the ROM 202 and RAM 203.
A printhead driver 207 drives the printhead 7. A carriage motor driver 208 drives a carriage motor 204 as the driving source of a driving mechanism for moving the carriage 10. A conveyance motor 205 serves as the driving source of the driving mechanism of the conveyance roller 5 and discharge roller 9. A conveyance motor driver 209 drives the conveyance motor 205.
A feeding motor 206 serves as the driving source of the driving mechanism of the pickup roller 2 and feeding roller 3. A feeding motor driver 210 drives the feeding motor 206.
The MPU 201 controls the printing operation (discharge of ink and movement of the printhead 7) of the printhead 7 via the printhead driver 207 and carriage motor driver 208. The MPU 201 also controls conveyance of the printing sheets 1 via the conveyance motor driver 209 and feeding motor driver 210.
The information processing apparatus 214 is, for example, a personal computer or portable terminal (for example, a smartphone or tablet terminal), and functions as the host computer of the printing apparatus 100. The information processing apparatus 214 includes a CPU 214a, a storage device 214b, and an I/F unit (interface unit) 214c. The CPU 214a executes a program stored in the storage device 214b. The storage device 214b is a RAM, a ROM, a hard disk, or the like, and stores a program to be executed by the CPU 214a and various data. The storage device 214b stores a printer driver 2141 for controlling the printing apparatus 100. By executing the printer driver 2141, the information processing apparatus 214 can generate printing data. The information processing apparatus 214 and printing apparatus 100 can transmit and receive data via the I/F unit 214c and an I/F unit 213.
<Example of Successive Overlapped Conveyance>
A successive overlapped conveyance operation will be described in time series with reference to
A description will be provided with reference to the state ST1 of
When the pickup roller 2 rotates, the top printing sheet (a preceding sheet 1-A) stacked on the feeding tray 11 is picked up. The preceding sheet 1-A picked up by the pickup roller 2 is conveyed by the feeding roller 3 rotating in the same direction as that of the pickup roller 2. The feeding motor 206 also drives the feeding roller 3. This embodiment will be described by using an arrangement including the pickup roller 2 and the feeding roller 3. However, an arrangement including only a feeding roller for feeding the printing sheet stacked on the stacking unit may be adopted.
When the sheet detection sensor 16 provided on the downstream side of the feeding roller 3 detects the leading edge of the preceding sheet 1-A, the feeding motor 206 is driven to rotate at a relatively high speed. In this example, the pickup roller 2 and feeding roller 3 exemplarily rotate at 20 inches/sec.
A description will be provided with reference to a state ST2 of
A description will be provided with reference to a state ST3 of
Note that the alignment operation is performed by making the leading edge of the printing sheet 1 abut against the conveyance nip portion to temporarily position the printing sheet 1 at the position of the conveyance roller 5, and controlling the rotation amount of the conveyance roller 5 with reference to the position of the conveyance roller 5.
The printing apparatus 100 of this embodiment is a serial type printing apparatus in which the carriage 10 mounts the printhead 7. The printing operation of the printing sheet 1 is performed by repeating a conveyance operation and an image forming operation. The conveyance operation is an operation of intermittently conveying the printing sheet by a predetermined amount using the conveyance roller 5. The image forming operation is an operation of discharging ink from the printhead 7 while moving the carriage 10 incorporating the printhead 7 when the conveyance roller 5 stops.
When alignment of the preceding sheet 1-A is performed, the feeding motor 206 is switched to low-speed driving again. That is, the pickup roller 2 and feeding roller 3 rotate at 7.6 inches/sec. While the conveyance roller 5 intermittently conveys the printing sheet 1 by the predetermined amount, the feeding motor 206 also intermittently drives the feeding roller 3. That is, while the conveyance roller 5 rotates, the feeding roller 3 also rotates. While the conveyance roller 5 stops, the feeding roller 3 also stops. The rotation speed of the feeding roller 3 is lower than that of the conveyance roller 5. Consequently, the printing sheet 1 is stretched between the conveyance roller 5 and the feeding roller 3. The feeding roller 3 is rotated together with the printing sheet 1 conveyed by the conveyance roller 5.
When the feeding motor 206 is intermittently driven, the driving shaft 19 also rotates. As described above, however, the rotation speed of the pickup roller 2 is lower than that of the conveyance roller 5. Consequently, the pickup roller 2 is rotated together with the printing sheet 1 conveyed by the conveyance roller 5. The pickup roller 2 thus rotates ahead of the driving shaft 19. More specifically, the projection 19a of the driving shaft 19 is spaced apart from the first surface 2a and abuts against the second surface 2b. Therefore, the second printing sheet (a succeeding sheet 1-B) is not picked up soon after the trailing edge of the preceding sheet 1-A passes through the pickup roller 2. After the preceding sheet 1-A passes through the feeding nip portion and the driving shaft 19 is driven for a predetermined time, the projection 19a abuts against the first surface 2a. The rotation of the driving shaft 19 is transmitted to the pickup roller 2, and the pickup roller 2 starts to rotate. This operation generates a time lag until the succeeding sheet 1-B is picked up.
A description will be provided with reference to a state ST4 of
That is, it is necessary to separate the leading edge of the succeeding sheet 1-B from the trailing edge of the preceding sheet 1-A by a predetermined distance to provide a predetermined time interval from when the sheet detection sensor 16 detects the trailing edge of the preceding sheet 1-A until it detects the leading edge of the succeeding sheet 1-B. To achieve this, the angle of the concave portion 2c of the pickup roller 2 is set to about 70°.
A description will be provided with reference to a state ST5 of
A description will be provided with reference to a state ST6 of
A description will be provided with reference to a state ST7 of
The position of the leading edge of the succeeding sheet 1-B is calculated from the rotation amount of the feeding roller 3 after the sheet detection sensor 16 detects the leading edge of the succeeding sheet 1-B, and controlled based on the calculation result. At this time, the preceding sheet 1-A undergoes an image forming operation based on the printing data by the printhead 7.
A description will be provided with reference to a state ST8 of
A description will be provided with reference to a state ST9 of
When alignment of the succeeding sheet 1-B is performed, the feeding motor 206 is switched to low-speed driving again. That is, the pickup roller 2 and feeding roller 3 rotate at 7.6 inches/sec. If there is printing data even after the succeeding sheet 1-B, the process returns to the state ST4 of
As described above, it is possible to continuously perform a printing operation for the plurality of printing sheets 1 while performing successive overlapped conveyance.
An example of processing by the MPU 201 to execute successive overlapped conveyance described above will be explained.
In step S1, when the information processing apparatus 214 transmits a printing start instruction via the I/F unit 213, a printing operation starts. In step S2, the feeding operation of the preceding sheet 1-A starts. More specifically, the feeding motor 206 is driven at low speed. The pickup roller 2 rotates at 7.6 inches/sec. The pickup roller 2 picks up the preceding sheet 1-A, and the feeding roller 3 feeds the preceding sheet 1-A toward the printhead 7.
In step S3, the sheet detection sensor 16 detects the leading edge of the preceding sheet 1-A. When the sheet detection sensor 16 detects the leading edge of the preceding sheet 1-A, the feeding motor 206 is switched to high-speed driving in step S4. That is, the pickup roller 2 and feeding roller 3 rotate at 20 inches/sec. In step S5, by controlling the rotation amount of the feeding roller 3 after the sheet detection sensor 16 detects the leading edge of the preceding sheet 1-A, the leading edge of the preceding sheet 1-A is made to abut against the conveyance nip portion to perform the skew correction operation of the preceding sheet 1-A.
In step S6, alignment of the preceding sheet 1-A is performed based on the printing data. That is, the preceding sheet 1-A is conveyed to a printing start position with reference to the position of the conveyance roller 5 based on the printing data by controlling the rotation amount of the conveyance roller 5. In step S7, the feeding motor 206 is switched to low-speed driving. In step S8, a printing operation starts when the printhead 7 discharges ink to the preceding sheet 1-A.
More specifically, the printing operation of the preceding sheet 1-A is performed by repeating a conveyance operation of intermittently conveying the preceding sheet 1-A by the conveyance roller 5 and an image forming operation (ink discharge operation) of discharging ink from the printhead 7 by moving the carriage 10. The feeding motor 206 is intermittently driven at low speed in synchronization with the operation of intermittently conveying the preceding sheet 1-A by the conveyance roller 5. That is, the pickup roller 2 and feeding roller 3 intermittently rotate at 7.6 inches/sec.
In step S9, it is determined whether there is printing data of the next page. If there is no printing data of the next page, the process advances to step S25. Upon completion of the printing operation of the preceding sheet 1-A in step S25, the preceding sheet 1-A is discharged in step S26, thereby terminating the printing operation.
If there is printing data of the next page, the feeding operation of the succeeding sheet 1-B starts in step S10. More specifically, the pickup roller 2 picks up the succeeding sheet 1-B, and the feeding roller 3 feeds the succeeding sheet 1-B toward the printhead 7. The pickup roller 2 rotates at 7.6 inches/sec. As described above, since the large concave portion 2c of the pickup roller 2 is provided with respect to the projection 19a of the driving shaft 19, the succeeding sheet 1-B is fed while having a predetermined interval with respect to the trailing edge of the preceding sheet 1-A.
In step S11, the sheet detection sensor 16 detects the leading edge of the succeeding sheet 1-B. When the sheet detection sensor 16 detects the leading edge of the succeeding sheet 1-B, the feeding motor 206 is switched to high-speed driving in step S12. That is, the pickup roller 2 and feeding roller 3 rotate at 20 inches/sec. In step S13, by controlling the rotation amount of the feeding roller 3 after the sheet detection sensor 16 detects the leading edge of the succeeding sheet 1-B, the succeeding sheet 1-B is conveyed so that its leading edge is at a position a predetermined amount before the conveyance nip portion. The preceding sheet 1-A is intermittently conveyed based on the printing data. Continuously driving the feeding motor 206 at high speed forms the overlap state in which the leading edge of the succeeding sheet 1-B overlaps the trailing edge of the preceding sheet 1-A.
In step S14, it is determined whether predetermined conditions are satisfied. The predetermined conditions are conditions for determining the skew correction state of the succeeding sheet 1-B (whether to execute successive overlapped conveyance). Details will be described later.
If the predetermined conditions are satisfied, it is determined in step S15 whether the image forming operation of the last row of the preceding sheet 1-A has started. If it is determined that the image forming operation of the last row of the preceding sheet 1-A has started, the process advances to step S16; otherwise, the process stands by until the image forming operation starts. In step S16, the leading edge of the succeeding sheet 1-B is made to abut against the conveyance nip portion while keeping the overlap state, thereby performing the skew correction operation of the succeeding sheet 1-B. If it is determined in step S17 that the image forming operation of the last row of the preceding sheet 1-A has ended, in step S18 the preceding printing sheet 1-A and the succeeding printing sheet 1-B are conveyed while keeping the overlap state, thereby performing alignment of the succeeding sheet 1-B. That is, the preceding sheet 1-A and the succeeding sheet 1-B are nipped and conveyed while the overlapping portion between the trailing edge of the preceding sheet 1-A and the leading edge of the succeeding sheet 1-B is nipped by the conveyance nip portion.
If it is determined in step S14 that the predetermined conditions are not satisfied, the overlap state is canceled to perform alignment of the succeeding sheet 1-B. More specifically, if it is determined in step S27 that the image forming operation of the last row of the preceding sheet 1-A has ended, the discharge operation of the preceding sheet 1-A is performed in step S28. During this operation, the feeding motor 206 is not driven, and thus the succeeding sheet 1-B stops while its leading edge is at the position the predetermined amount before the conveyance nip portion. Since the preceding sheet 1-A is discharged, the overlap state is canceled. In step S29, the leading edge of the succeeding sheet 1-B is made to abut against the conveyance nip portion to perform the skew correction operation of the succeeding sheet 1-B. In step S18, alignment of the succeeding sheet 1-B is performed. In this way, the preceding sheet and the succeeding sheet are nipped and conveyed without making them overlap each other.
In step S19, the feeding motor 206 is switched to low-speed driving. In step S20, a printing operation starts by discharging ink from the printhead 7 to the succeeding sheet 1-B. More specifically, the printing operation of the succeeding sheet 1-B is performed by repeating a conveyance operation of intermittently conveying the succeeding sheet 1-B by the conveyance roller 5 and an image forming operation (ink discharge operation) of discharging ink from the printhead 7 by moving the carriage 10. The feeding motor 206 is intermittently driven at low speed in synchronization with the operation of intermittently conveying the succeeding sheet 1-B by the conveyance roller 5. That is, the pickup roller 2 and feeding roller 3 intermittently rotate at 7.6 inches/sec.
In step S21, it is determined whether there is printing data of the next page. If there is printing data of the next page, the process returns to step S10. If there is no printing data of the next page, when the image forming operation of the succeeding sheet 1-B is complete in step S22, the discharge operation of the succeeding sheet 1-B is performed in step S23 and the printing operation ends in step S24.
The operation, described in steps S12 and S13 of
Three states in a process of conveying the printing sheets 1 by the conveyance roller 5 and feeding roller 3 will be sequentially described. The first state in which an operation of making the succeeding sheet 1-B chase the preceding sheet 1-A is performed will be described with reference to states ST11 and ST12 of
In the state ST11 of
In the first state, the chasing operation may stop in the first section A1. If, as shown in the state ST12 of
In the state ST13 of
In the second state, the operation of making the succeeding sheet overlap the preceding sheet may stop in the second section A2. If, as shown in the state ST14 of
In the state ST15 of
The operation of determining whether to perform the first skew correction operation or the second skew correction operation will be described. The first skew correction operation is an operation of performing skew correction by making the leading edge of the succeeding sheet 1-B abut against the conveyance nip portion while keeping the overlap state between the preceding sheet 1-A and the succeeding sheet 1-B. The second skew correction operation is an operation of performing skew correction by canceling the overlap state between the preceding sheet 1-A and the succeeding sheet 1-B and then making the leading edge of the succeeding sheet 1-B abut against the conveyance nip portion.
In step S101, the operation starts. In step S102, it is determined whether the leading edge of the succeeding sheet 1-B has reached a determination position (the position P3 in the state ST15 of
On the other hand, if it is determined that the leading edge of the succeeding sheet 1-B has reached the determination position P3 (YES in step S102), it is determined whether the trailing edge of the preceding sheet 1-A has passed through the conveyance nip portion (step S105). If it is determined that the trailing edge of the preceding sheet 1-A has passed through the conveyance nip portion (YES in step S105), the succeeding sheet does not overlap the preceding sheet. Thus, a skew correction operation for only the succeeding sheet 1-B is decided (step S106). That is, only the succeeding sheet 1-B is made to abut against the conveyance nip portion to perform a skew correction operation, and then alignment of only the succeeding sheet 1-B is performed.
On the other hand, if it is determined that the trailing edge of the preceding sheet 1-A has not passed through the conveyance nip portion (NO in step S105), it is determined whether the overlap amount of the trailing edge of the preceding sheet 1-A and the leading edge of the succeeding sheet 1-B is smaller than a threshold (step S107). The position of the trailing edge of the preceding sheet 1-A is updated along with the printing operation of the preceding sheet 1-A. The position of the leading edge of the succeeding sheet 1-B is at the above-described determination position. That is, the overlap amount decreases along with the printing operation of the preceding sheet 1-A. If it is determined that the overlap amount is smaller than the threshold (YES in step S107), the overlap state is canceled, and a skew correction operation for only the succeeding sheet 1-B is decided (step S108). That is, after the image forming operation of the preceding sheet 1-A ends, the succeeding sheet 1-B is not conveyed together with the preceding sheet 1-A. More specifically, the conveyance motor 205 drives the conveyance roller 5 to convey the preceding sheet 1-A. However, the feeding roller 3 is not driven. Therefore, the overlap state is canceled. Furthermore, only the succeeding sheet 1-B is made to abut against the conveyance nip portion to perform a skew correction operation, and then alignment of only the succeeding sheet 1-B is performed.
If it is determined that the overlap amount is equal to or larger than the threshold (NO in step S107), it is determined whether there is a gap between the last row of the preceding sheet and the row immediately preceding the last row (step S109). If it is determined that there is no gap (NO in step S109), the overlap state is canceled and a skew correction operation for only the succeeding sheet 1-B is decided (step S110). The skew correction operation of the succeeding sheet 1-B may influence the image forming operation of the preceding sheet 1-A. If there is no gap, the influence may be conspicuous, and thus the overlap state is canceled to perform a skew correction operation for only the succeeding sheet 1-B.
If it is determined that there is a gap (YES in step S109), the skew correction operation of the succeeding sheet 1-B is performed while keeping the overlap state (step S111), and then alignment of the succeeding sheet 1-B is performed. That is, after the start of the image forming operation of the last row of the preceding sheet 1-A, the succeeding sheet 1-B is made to abut against the conveyance nip portion while the succeeding sheet 1-B overlaps the preceding sheet 1-A. Upon end of the image forming operation of the last row, the conveyance roller 5 and the feeding roller 3 are rotated by driving the feeding motor 206 together with the conveyance motor 205, and alignment of the succeeding sheet 1-B is performed while it overlaps the preceding sheet 1-A. As described above, the operation of determining whether to keep or cancel the overlap state between the preceding sheet 1-A and the succeeding sheet 1-B is performed.
As described above, according to this embodiment, successive overlapped conveyance is executed by nipping and conveying the trailing edge of the preceding sheet 1-A and the leading edge of the succeeding sheet 1-B at least on condition that printing of the preceding sheet 1-A has ended (steps S17 and S18). In this case, during the printing operation of the preceding sheet 1-A, only the preceding sheet 1-A is nipped and conveyed by the conveyance nip portion. Therefore, the conveyance accuracy never decreases or the printing quality never degrades. Since successive overlapped conveyance is executed after the end of printing of the preceding sheet 1-A, the printing speed can be increased.
According to the above embodiment, at the start of feeding of the succeeding sheet 1-B, it is not necessary to confirm whether to execute successive overlapped conveyance. This is advantageous in that even if the marginal amount of the succeeding sheet 1-B is uncertain at the start of feeding of the succeeding sheet 1-B, it is possible to execute successive overlapped conveyance when the marginal amount is confirmed.
Furthermore, according to the above embodiment, the synchronous and asynchronous operations of the feeding motor 206 and the conveyance motor 205 are switched when performing the printing operation of the preceding sheet 1-A by the printhead 7. More specifically, before the sheet detection sensor 16 detects the leading edge of the succeeding sheet 1-B, the feeding motor 206 is driven in synchronism with the conveyance motor 205. On the other hand, after the sheet detection sensor 16 detects the leading edge of the succeeding sheet, the feeding motor 206 is continuously driven. Continuously driving the feeding motor makes it possible to perform a chasing operation to make the succeeding sheet 1-B overlap the preceding sheet 1-A, and to adjust the overlap amount of the preceding and succeeding printing sheets 1 in successive overlapped conveyance. The overlap amount is set by referring to the printing data of the preceding sheet 1-A and that of the succeeding sheet 1-B.
Note that in the above embodiment, the preceding sheet 1-A and the succeeding sheet 1-B are fed while having an interval there between. An arrangement of conveying the sheets while they overlap each other at the time of feeding can be adopted.
The second embodiment of the present invention will be described below. Note that an arrangement is the same as in the first embodiment, unless otherwise specified. The first embodiment has exemplifies a case in which only the preceding sheet 1-A is nipped and conveyed by the conveyance nip portion during the printing operation of the preceding sheet 1-A. In this embodiment, a case in which only a succeeding sheet 1-B is nipped and conveyed by a conveyance nip portion during the printing operation of the succeeding sheet 1-B will be explained.
In this embodiment, if it is determined in step S107 that an overlap amount is equal to or larger than a threshold, processing in step S201 is executed. If YES is determined in the processing in step S201, the process advances to step S109; otherwise, the process advances to step S202.
In step S201, it is determined whether the trailing edge of a preceding sheet 1-A has passed through the conveyance nip portion when successive overlapped conveyance is executed to perform alignment of the succeeding sheet 1-B. A determination method will be described with reference to
In a state ST21 of
In a state ST22 of
These values are used. Only if L≦Q−x is satisfied, the preceding sheet 1-A has passed through the conveyance nip portion at the time of alignment of the succeeding sheet 1-B. It is determined in step S201 whether this condition is satisfied. Note that methods of calculating the values L and Q will be described later.
If it is determined that the trailing edge of the preceding sheet 1-A has not passed through the conveyance nip portion, the process advances to step S202 to cancel the overlap state and decide a skew correction operation for only the succeeding sheet 1-B. That is, after the image forming operation of the preceding sheet 1-A ends, the succeeding sheet 1-B is not conveyed together with the preceding sheet 1-A. More specifically, the conveyance motor 205 drives the conveyance roller 5 to convey the preceding sheet 1-A. However, the feeding roller 3 is not driven. Therefore, the overlap state is canceled. Furthermore, only the succeeding sheet 1-B is made to abut against the conveyance nip portion to perform a skew correction operation, and then alignment of only the succeeding sheet 1-B is performed.
If it is determined that the trailing edge of the preceding sheet 1-A has passed through the conveyance nip portion when alignment of the succeeding sheet 1-B is performed (YES in step S202), the process advances to step S111. The following processing is the same as in the first embodiment.
An example of processing of calculating the length L will be described with reference to
In step S303, calculation of the length L shown in
In step S304, it is determined whether the image forming operation of the preceding sheet 1-A is performed for the last row. If the image forming operation of the preceding sheet 1-A is not performed for the last row (NO in step S304), the processing of calculating the length L which has started in step S303 described above continues. As the conveyance amount N increases, the length L decreases. If the image forming operation of the preceding sheet 1-A is performed for the last row (YES in step S304), the process advances to step S305.
In step S305, calculation of the length L ends, and the current value of the length L is set as a confirmed value. The confirmed value of the length L is saved in, for example, a RAM 203. After that, the processing of one unit ends (step S306).
An example of processing of calculating the length Q will be described with reference to
The first printing data to be printed on the succeeding printing sheet 1-B is loaded (step S404). The first printing data indicates that requiring an ink discharge operation. That is, the printing data includes no blank. With this processing, the position of the first printing data from the leading edge of the sheet is specified. In other words, a non-printing area is specified. It is determined whether the distance between the leading edge of the succeeding printing sheet 1-B and the first printing data is larger than the previously, temporarily set length Q (step S405). If the distance is larger than the length Q, the process advances to step S406; otherwise, the process advances to step S407. In step S406, the length Q is updated by the distance between the leading edge of the succeeding printing sheet 1-B and the first printing data.
Next, the first carriage movement instruction is generated (step S407). Generating a carriage movement instruction decides a nozzle to be used to print the first printing data. In step S408, the length Q is updated, as needed, and is confirmed so that the position of the decided nozzle coincides with the printing start position of the succeeding printing sheet 1-B. The confirmed value of the length Q is saved in, for example, the RAM 203 (step S409), thereby terminating the process (step S410).
Note that the step of calculating the leading edge position after alignment of the succeeding sheet corresponds to step S9 of the flowchart illustrating the successive overlapped conveyance operation shown in
The determination processing in step S109 of
As described above, according to this embodiment, the lengths L and Q are calculated based on the printing data of the preceding sheet and succeeding sheet. The length L indicates the position of the trailing edge of the preceding sheet 1-A at the time of the image forming operation of the last row of the preceding sheet 1-A. The length Q indicates the position of the leading edge of the succeeding sheet 1-B at the time of alignment of the succeeding sheet 1-B.
The preceding sheet 1-A and succeeding sheet 1-B are controlled to be conveyed to the printhead 7 while they overlap each other based on the calculation results so that the trailing edge of the preceding sheet 1-A has passed through the conveyance nip portion at the time of alignment of the succeeding sheet 1-B.
This prevents the conveyance nip portion from nipping the preceding sheet 1-A and the succeeding sheet 1-B while they overlap each other at the time of the printing operation of the succeeding sheet 1-B. As a result, the conveyance accuracy of the preceding sheet 1-A and succeeding sheet 1-B never decreases or the printing quality never degrades. Since successive overlapped conveyance is executed after the end of printing of the preceding sheet 1-A, the printing speed can be increased.
Note that in the first and second embodiments, the arrangement in which successive overlapped conveyance is performed by making the succeeding sheet 1-B overlap the preceding sheet 1-A on the side of the printhead 7 is adopted. As described in the first embodiment, it is possible to prevent the succeeding sheet 1-B from entering between the preceding sheet 1-A and the printhead 7 at the time of the printing operation of the preceding sheet 1-A by starting successive overlapped conveyance after the end of printing of the preceding sheet 1-A.
If the printing speed is prioritized, only the control operation according to the first embodiment may be performed. Conversely, as described in the second embodiment, during the printing operation of the succeeding sheet 1-B, the conveyance nip portion may be controlled to nip and convey only the succeeding sheet 1-B. That is, it is possible to execute successive overlapped conveyance at least on condition that the conveyance nip portion does not nip and convey the overlapping portion between the preceding sheet 1-A and the succeeding sheet 1-B during at least one of the printing operation of the preceding sheet 1-A or the printing operation of the succeeding sheet 1-B.
In the above-described first and second embodiments, a case in which the printing sheet 1 is made to abut against the conveyance nip portion to perform a skew correction operation has been explained. In this embodiment, a case in which no skew correction operation is performed will be described. Note that it is possible to manage the conveyance position of a printing sheet 1 based on a detection result of a sheet detection sensor 16 and a conveyance amount from the detection result as the starting point.
Upon receiving the printing data, a preceding sheet 1-A is fed (step S501), alignment is performed (step S502), and then a printing operation starts (step S503). In step S504, it is determined whether the trailing edge of the preceding sheet 1-A has passed through the sheet detection sensor 16. If the trailing edge has not passed through the sheet detection sensor 16, the processing in step S504 is repeated until the trailing edge passes through the sheet detection sensor 16.
If the trailing edge of the preceding sheet 1-A has passed through the sheet detection sensor 16, it is determined in step S505 whether there is the next page. If there is no next page, the printing operation continues. If the printing operation ends, the preceding sheet 1-A is conveyed to a discharge roller 9 to perform discharge processing, thereby terminating the processing of one unit (step S506). If there is the next page, control operations associated with successive overlapped conveyance in step S507 and subsequent steps are performed.
In step S507, a succeeding sheet 1-B is fed. In step S508, the succeeding sheet 1-B is conveyed until its leading edge is set at a position a predetermined distance y away from a conveyance nip portion, and the process stands by. This corresponds to the state shown in
In step S509, a distance R is calculated based on the printing data of the succeeding sheet 1-B. The distance R is the distance between the conveyance nip portion and the leading edge of the succeeding sheet 1-B at the time of alignment of the succeeding sheet 1-B.
In this embodiment, it is required that the trailing edge of the preceding sheet 1-A has passed through the conveyance nip portion at the time of alignment of the succeeding sheet 1-B. This is because if the trailing edge has not passed the conveyance nip portion, the preceding sheet 1-A and the succeeding sheet 1-B overlap each other at the conveyance nip portion and thus the conveyance accuracy may decrease. As shown in
In step S510, it is determined whether the printing operation of the preceding sheet 1-A has ended. This is a step of determining whether the leading edge of the succeeding sheet 1-B enters the conveyance nip portion before the end of the printing operation of the preceding sheet 1-A. If the printing operation has not ended, the processing in step S510 is repeated until the printing operation ends.
If the printing operation of the preceding sheet 1-A has ended, the above-described distance R of the leading edge at the time of alignment of the succeeding sheet 1-B is compared with a predetermined amount T in step S511.
If the distance R is smaller than the predetermined amount T, the process advances to step S519 to control not to make the succeeding sheet 1-B overlap the preceding sheet 1-A. This avoids a malfunction which may occur when the distance R, that is, the overlap amount R-z is small. As an example of the malfunction, the sheets do not overlap each other due to a conveyance error. As another example, since the overlap amount is small, the influence of the warp or deformation of the printing sheet 1 becomes large, thereby causing a failure in nipping by the conveyance nip portion.
In step S519, a conveyance roller 5 is driven to convey only the preceding sheet 1-A. In step S520, it is determined whether the trailing edge of the preceding sheet 1-A has passed through the conveyance nip portion, and conveyance of only the preceding sheet 1-A by the conveyance roller 5 is repeated until the trailing edge of the preceding sheet 1-A passes through the conveyance nip portion. If the trailing edge of the preceding sheet 1-A has passed through the conveyance nip portion, the process advances to step S521 to drive a feeding roller 3 and the conveyance roller 5 in synchronism with each other. This conveys the succeeding sheet 1-B to the printhead 7 and conveys the preceding sheet 1-A to the discharge roller 9. In step S518, the printing operation of the succeeding sheet 1-B starts. Processes in step S518 and subsequent steps are the same as those for the preceding sheet 1-A and a detailed description thereof will be provided later.
If it is determined in step S511 that the distance R is larger than the predetermined amount T, the process advances to step S512. In this example, a distance S between the conveyance nip portion and the trailing edge of the preceding sheet 1-A is calculated.
In step S513, the distance S is compared with a predetermined amount U. If the distance S is smaller than the predetermined amount U, the process advances to step S519 to control not to make the succeeding sheet 1-B overlap the preceding sheet 1-A. This avoids a malfunction which may occur when the distance S, that is, the overlap amount S-y is small, similarly to the above-described distance R. An operation when the sheets are not made to overlap each other is the same as the above-described one and a description thereof will be omitted.
If the distance S is larger than the predetermined amount U, the process advances to step S514 to compare overlap amounts R−y and S−z. If the overlap amount R−y is larger than the overlap amount S−z, when the succeeding sheet 1-B is conveyed, the trailing edge of the preceding sheet 1-A is kept nipped by the conveyance nip portion at the time of alignment of the succeeding sheet 1-B. To avoid this, if the overlap amount R−y is larger than the overlap amount S−z, the process advances to step S515 to convey only the preceding sheet 1-A without conveying the succeeding sheet 1-B. In step S516, the conveyance amount of the preceding sheet 1-A in step S515 is subtracted from the distance S, thereby updating the distance S. The process then returns to step S514 to repeat the step of conveying only the preceding sheet 1-A without conveying the succeeding sheet 1-B until the overlap amount S−z becomes smaller than the overlap amount R−y. When the overlap amount S−z becomes smaller than the overlap amount R−y, the process advances to step S517.
In step S517, the preceding sheet 1-A and succeeding sheet 1-B are conveyed to the printhead 7 while they overlap each other. In step S518, the printing operation of the succeeding sheet 1-B starts. As described above, at the start of the printing operation of the succeeding sheet 1-B, the state is that shown in
In this embodiment, as described above, the distance S associated with the position of the preceding sheet 1-A and the distance R associated with the position of the succeeding sheet 1-B at the time of alignment of the succeeding sheet 1-B are calculated based on the printing data of the printing sheet 1.
When the two printing sheets 1 are conveyed while they overlap each other in successive overlapped conveyance, it is controlled so that the succeeding sheet 1-B does not enter the conveyance nip portion at the time of printing of the last row of the preceding sheet 1-A. Also, it is controlled so that the trailing edge of the preceding sheet 1-A has passed through the conveyance nip portion at the time of the printing operation of the succeeding sheet 1-B.
This prevents printing on the preceding sheet 1-A or succeeding sheet 1-B while the two printing sheets overlap each other at the conveyance nip portion. Therefore, the conveyance accuracy of the preceding sheet 1-A and succeeding sheet 1-B never decreases or the printing quality never degrades. Since successive overlapped conveyance is executed after the end of printing of the preceding sheet 1-A, the printing speed can be increased.
When executing successive overlapped conveyance, if it is first determined that the condition is not satisfied, only the preceding sheet 1-A is conveyed. Then, as soon as the condition is satisfied, the preceding sheet 1-A and succeeding sheet 1-B are conveyed in synchronism with each other (steps S515 and S516). This makes it possible to convey the succeeding sheet 1-B to the printhead 7 not only while the preceding sheet 1-A stops, that is, the conveyance roller 5 stops, but also during conveyance of the preceding sheet 1-A. It is possible to further decrease the interval between the preceding sheet 1-A and the succeeding sheet 1-B, thereby increasing the printing speed.
In the first to third embodiments, it is assumed that the sheets are made to overlap each other in successive overlapped conveyance so that the succeeding sheet 1-B is at a position on the side of the printhead 7 with respect to the preceding sheet 1-A. However, the positional relationship may be reversed. That is, the sheets may be made to overlap each other so that the preceding sheet 1-A is at a position on the side of the printhead 7 with respect to the succeeding sheet 1-B. Such overlap state can be implemented by, for example, providing a lever for pushing the trailing edge of the preceding sheet 1-A upward as a lever corresponding to the sheet pressing lever 17.
An example of conveyance control when a preceding sheet 1-A is at a position on the side of the printhead 7 will be described below. A case in which no skew correction operation is performed as described in the third embodiment will be explained. This embodiment, however, is also applicable to a case in which a skew correction operation is performed.
In steps S609 and S610, distances V and W are calculated based on the printing data. In step S609, the distance V between a conveyance nip portion and the leading edge of the succeeding sheet 1-B at the time of alignment of the succeeding sheet 1-B is calculated. In step S610, the distance W between the conveyance nip portion and the trailing edge of the preceding sheet 1-A at the time of alignment of the succeeding sheet 1-B is calculated. At the time of alignment of the succeeding sheet 1-B, the trailing edge of the preceding sheet 1-A needs to have passed through not only the conveyance nip portion but also the printhead 7. That is, the preceding sheet 1-A needs to be at a position which has no influence on the printing operation of the succeeding sheet 1-B. In step S611, based on the two distances V and W, a largest overlap amount G of the two printing sheets at the time of alignment of the succeeding sheet 1-B is calculated. As shown in
In step S612, it is determined whether the printing operation of the preceding sheet 1-A has ended. This is a step of determining whether the leading edge of the succeeding sheet 1-B enters the conveyance nip portion before the end of the printing operation of the preceding sheet 1-A. If the printing operation has not ended, the processing in step S612 is repeated until the printing operation ends.
If the printing operation of the preceding sheet 1-A has ended, the above-described largest overlap amount G of the preceding sheet 1-A and succeeding sheet 1-B at the time of alignment of the succeeding sheet 1-B is compared with a predetermined amount H in step S613.
If the largest overlap amount G is smaller than the predetermined amount H, the process advances to step S621 to control not to make the succeeding sheet 1-B overlap the preceding sheet 1-A. This avoids a malfunction which may occur when the largest overlap amount G is small. As an example of the malfunction, the sheets do not overlap each other due to a conveyance error. As another example, since the overlap amount is small, the influence of the warp or deformation of the printing sheet 1 becomes large, thereby causing a failure in nipping by the conveyance nip portion.
In step S621, a conveyance roller 5 is driven to convey only the preceding sheet 1-A. In step S622, it is determined whether the trailing edge of the preceding sheet 1-A has passed through the conveyance nip portion, and conveyance of only the preceding sheet 1-A by the pair of conveyance rollers is repeated until the trailing edge of the preceding sheet 1-A passes through the conveyance nip portion.
If the trailing edge of the preceding sheet 1-A has passed through the conveyance nip portion, the process advances to step S623 to drive a feeding roller 3 and the conveyance roller 5 in synchronism with each other. This conveys the succeeding sheet 1-B to the printhead 7 and conveys the preceding sheet 1-A to a discharge roller 9. In step S620, the printing operation of the succeeding sheet 1-B starts. Processes in step S620 and subsequent steps are the same as those for the preceding sheet 1-A and a detailed description thereof will be provided later.
If the largest overlap amount G is larger than the predetermined amount H, the process advances to step S614. In this example, a distance J between the conveyance nip portion and the trailing edge of the preceding sheet 1-A is calculated.
In step S615, the distance J is compared with a predetermined amount K. If the distance J is smaller than the predetermined amount K, the process advances to step S621 to control not to make the succeeding sheet 1-B overlap the preceding sheet 1-A. This avoids a malfunction which may occur when the distance J, that is, the overlap amount J-y is small, similarly to the above-described largest overlap amount G. An operation when the sheets are not made to overlap each other is the same as the above-described one and a description thereof will be omitted.
If the distance J is larger than the predetermined amount K, the process advances to step S616 to compare the largest overlap amount G with the overlap amount J-y. If the largest overlap amount G is larger than the overlap amount J-y, when the succeeding sheet 1-B is conveyed, the trailing edge of the preceding sheet 1-A does not pass through the printhead 7 at the time of the image forming operation of the succeeding sheet 1-B. To avoid this, if the largest overlap amount G is larger than the overlap amount J-y, the process advances to step S617 to convey only the preceding sheet 1-A without conveying the succeeding sheet 1-B. In step S618, the conveyance amount of the preceding sheet 1-A in step S617 is subtracted from the distance J, thereby updating the distance J. The process then returns to step S616 to repeat the step of conveying only the preceding sheet 1-A without conveying the succeeding sheet 1-B until the overlap amount J-y becomes smaller than the largest overlap amount G. When the overlap amount J-y becomes smaller than the largest overlap amount G, the process advances to step S619.
In step S619, the preceding sheet 1-A and succeeding sheet 1-B are conveyed to the printhead 7 while they overlap each other. In step S620, the printing operation of the succeeding sheet 1-B starts. As described above, when the printing operation of the succeeding sheet 1-B is performed, the state is that shown in
As described above, even if the preceding sheet 1-A and the succeeding sheet 1-B are made to overlap each other so that the preceding sheet 1-A is at a position on the side of the printhead 7 with respect to the succeeding sheet 1-B, successive overlapped conveyance can be implemented.
As another example of the arrangement, a method of making the succeeding sheet 1-B overlap the preceding sheet 1-A (which of the preceding sheet 1-A and the succeeding sheet 1-B is at a position on the side of the printhead 7) may be selectable. In this case, calculated overlap amounts may be compared, thereby controlling to select a more appropriate method of making the sheets overlap each other.
Embodiments 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 a ‘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 embodiments, 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 embodiments and/or controlling the one or more circuits to perform the functions of one or more of the above-described embodiments. 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 benefits of Japanese Patent Application No. 2014-116205, filed Jun. 4, 2014, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
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| 2014-116205 | Jun 2014 | JP | national |
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| Number | Date | Country | |
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| 20150352866 A1 | Dec 2015 | US |
