Printing apparatus and method of controlling the same

A printing apparatus comprises a first roller for conveying sheets, a first motor for driving the first roller, a second roller for conveying sheets, a second motor for driving the second roller, and a conveyance controller that controls conveyance to be able to execute a first conveyance operation for conveying sheets such that the trailing edge of a preceding sheet and the leading edge of a succeeding sheet overlap, and a second conveyance operation for conveying sheets by arranging a distance between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet. The conveyance controller, based on information indicating whether the second motor is in a temperature rising state, controls whether to execute the first conveyance operation or to execute the second conveyance operation.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a printing apparatus for printing on a sheet by a printing head, and more particularly, to a printing apparatus for conveying a sheet to a printing area facing the printing head in a state in which a part of a preceding sheet and a part of a succeeding sheet overlap with each other.

Description of the Related Art

Japanese Patent Laid-Open No. 2015-168237 describes a printing apparatus in which, in order to improve the throughput of continuous printing for a plurality of printing sheets, a preceding sheet and a succeeding sheet are fed with predetermined intervals therebetween, and thereafter an operation is performed so that the leading edge of the succeeding sheet overlaps the preceding sheet and the succeeding sheet is conveyed to a position facing the printing head.

Further, Japanese Patent No. 4921055 discloses a printing apparatus that detects a temperature rise of a conveyance motor during printing of a printing sheet and lowers the speed of the conveyance motor.

Here, in the configuration of Japanese Patent Laid-Open No. 2015-168237, when the leading edge of the succeeding sheet being conveyed by the feeding roller passes through a predetermined position, in order to overlap the succeeding sheet on the trailing edge of the preceding sheet, the feeding roller uniformly switches to high-speed driving, regardless of the position of the trailing edge of the preceding sheet. Therefore, after the high-speed driving of the feeding roller is started, when the speed of the conveyance motor for conveying the preceding sheet is lowered due to the temperature rise or the like of the conveyance motor, the succeeding sheet may collide with the trailing edge of the preceding sheet. When an attempt is made to avoid a collision with the preceding sheet whose speed is decreased while the succeeding sheet is being conveyed at a high speed, the feeding roller for conveying the succeeding sheet is repeatedly driven and stopped. At this time, there is a problem that a conveyance deviation of the succeeding sheet is caused by influence of the backlash of the driving unit.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-mentioned problems, and in a case where a preceding sheet and a succeeding sheet are conveyed, the succeeding sheet is conveyed so as to suppress conveyance deviation even in a case where the speed of the conveyance roller is reduced.

According to a first aspect of the present invention, there is provided a printing apparatus, comprising: a first roller configured to convey sheets; a first motor configured to drive the first roller; a second roller configured to convey sheets conveyed by the first roller; a second motor configured to drive the second roller; and a conveyance controller configured to be able to execute a first conveyance operation for conveying sheets such that the trailing edge of a preceding sheet and the leading edge of a succeeding sheet, which is a sheet conveyed after the preceding sheet, overlap, and a second conveyance operation for conveying sheets by arranging a distance between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet, wherein the conveyance controller, based on information indicating that the second motor is in a temperature rising state, controls whether to execute the first conveyance operation or to execute the second conveyance operation.

According to a second aspect of the present invention, there is provided a printing apparatus, comprising: a first roller configured to convey sheets; a first motor configured to drive the first roller; a second roller configured to convey sheets conveyed by the first roller; a second motor configured to drive the second roller; and a conveyance controller configured to be able to execute a first conveyance operation for conveying sheets such that the trailing edge of a preceding sheet and the leading edge of a succeeding sheet, which is a sheet conveyed after the preceding sheet, overlap, and a second conveyance operation for conveying sheets by arranging a distance between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet, wherein the conveyance controller, based on temperature information of the second motor, controls whether to execute the first conveyance operation or to execute the second conveyance operation.

According to a third aspect of the present invention, there is provided a method of controlling a printing apparatus comprising a first roller for conveying sheets, a first motor for driving the first roller, a second roller for conveying sheets conveyed by the first roller, and a second motor for driving the second roller, the method comprising: controlling conveyance to be able to execute a first conveyance operation for conveying sheets such that the trailing edge of a preceding sheet and the leading edge of a succeeding sheet, which is a sheet conveyed after the preceding sheet, overlap, and a second conveyance operation for conveying sheets by arranging a distance between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet, wherein the controlling conveyance, based on information indicating that the second motor is in a temperature rising state, controls whether to execute the first conveyance operation or to execute the second conveyance operation.

According to a fourth aspect of the present invention, there is provided a method of controlling a printing apparatus comprising a first roller for conveying sheets, a first motor for driving the first roller, a second roller for conveying sheets conveyed by the first roller, and a second motor for driving the second roller, the method comprising: controlling conveyance to be able to execute a first conveyance operation for conveying sheets such that the trailing edge of a preceding sheet and the leading edge of a succeeding sheet, which is a sheet conveyed after the preceding sheet, overlap, and a second conveyance operation for conveying sheets by arranging a distance between the trailing edge of the preceding sheet and the leading edge of the succeeding sheet, wherein the controlling conveyance, based on temperature information of the second motor, controls whether to execute the first conveyance operation or to execute the second conveyance operation.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, an embodiment of the present invention is described in detail with reference to the accompanying drawings.

FIG.1toFIG.4are cross-sectional views for explaining an operation of overlapped continuous feeding in the printing apparatus according to the embodiment of the present invention (an operation of overlapping the leading edge of the succeeding sheet on the trailing edge of the preceding sheet and conveying the sheet). First, a schematic configuration of a printing apparatus capable of executing an operation of overlapped continuous feeding in the present embodiment is described with reference to the view illustrated in ST1ofFIG.1.

In ST1ofFIG.1, reference numeral1denotes printing sheets. A plurality of printing sheets1are stacked in a feeding tray11(stacking unit). Reference numeral2is a pick-up roller that comes into contact with the uppermost printing sheet1stacked on the feeding tray11and picks up the printing sheet. Reference numeral3is a feeding roller for feeding the printing sheet1picked up by the pick-up roller2to the downstream side in the sheet conveyance direction. Reference numeral4is a feed driven roller biased to the feeding roller3and for feeding by sandwiching the printing sheet1together with the feeding roller3.

Reference numeral5is a conveyance roller for conveying the printing sheet1fed by the feeding roller3and the feed driven roller4to a position facing the printing head7. Reference numeral6is a pinch roller biased to the conveyance roller5and for conveying by sandwiching the printing sheet together with the conveyance roller5.

Reference numeral7is a printing head for performing printing on the printing sheet1conveyed by the conveyance roller5and the pinch roller6. In the present embodiment, it is assumed that the printing head is an inkjet printing head which discharges ink from the printing head and performs printing on the printing sheet1. Reference numeral8is a platen that supports the back surface of the printing sheet1at a position facing the printing head7. Reference numeral10is a carriage that is mounted on the printing head7and moves in a direction intersecting the sheet conveyance direction.

Reference numeral9is a discharge roller for discharging a printing sheet on which printing was performed by the printing head7to the outside of the apparatus. Reference numerals12and13are spurs that rotate in contact with the printing surface of the printing sheet on which printing was performed by the printing head7. Here, the spur13on the downstream side is biased to the discharge roller9, and discharge roller9is not disposed at a position facing the spur12on the upstream side. The spur12is for preventing upward displacement of the printing sheet1and is also referred to as a pressing spur.

Between the feeding nip portion formed by the feeding roller3and the feed driven roller4, and the conveying nip portion formed by the conveyance roller5and the pinch roller6, the printing sheet1is guided by the conveying guide15. Reference numerals16and18are sheet detection sensors for detecting the leading edge and the trailing edge of the printing sheet1. The first sheet detection sensor16is disposed near the downstream side of the feeding roller3in the sheet conveyance direction, and the second sheet detection sensor18is disposed near the upstream side of the conveyance roller5in the sheet conveyance direction. Reference numeral17is a sheet holding lever for overlapping the leading edge portion of the succeeding sheet on the trailing edge portion of the preceding sheet. The sheet holding lever17is biased by a spring in the counterclockwise direction in the drawing around the rotation shaft17b.

FIG.5AandFIG.5Bare views illustrating a configuration of a pick-up roller2. As described above, the pick-up roller2comes into contact with the uppermost printing sheet stacked in the feeding tray11and picks up the printing sheet. Reference numeral19is a drive shaft for transmitting the drive of the feed motor, described later, to the pick-up roller2. When the printing sheet is picked up, the drive shaft19and the pick-up roller2rotate in the direction of arrow A in the drawing. A projection19ais provided on the drive shaft19. A concave portion2c, in which the projection19cis fitted, is formed on the pick-up roller2. As illustrated inFIG.5A, in a case where the projection19ais in contact with a first surface2aof the concave portion2cof the pick-up roller2, the drive of the drive shaft19is transmitted to the pick-up roller2, and the pick-up roller2is also rotated when the drive shaft19is driven. On the other hand, as illustrated inFIG.5B, in a case where the projection19ais in contact with a second surface2aof the concave portion2cof the pick-up roller2, the drive of the drive shaft19is not transmitted to the pick-up roller2, and the pick-up roller2is not rotated when the drive shaft19is driven. Even in a case where the projection19adoes not abut either of the first surface2aand a second surface2band is located between the first surface2aand the second surface2b, the pick-up roller2is not rotated even if the drive shaft19is driven.

FIG.6is a block diagram of the printing apparatus of the embodiment. Reference numeral201denotes an MPU that controls operations of each unit, processing of data, and the like. As described later, the MPU201also functions as a conveyance control unit that can control the conveyance of the printing sheet so that the trailing edge portion of the preceding printing sheet overlaps the leading edge portion of the succeeding sheet. Reference numeral202is a ROM for storing programs and data to be executed by the MPU201. Reference numeral203is a RAM for temporarily storing processing data executed by the MPU201and data received from a host computer214.

The printing head7is controlled by a printing head driver207. A carriage motor204for driving the carriage10is controlled by a carriage motor driver208. The conveyance roller5and the discharge roller9are driven by a conveyance motor205. The conveyance motor205is controlled by a conveyance motor driver209. The pick-up roller2and the feeding roller3are driven by the feed motor206. The feed motor206is controlled by a feeding motor driver210.

The carriage motor204, the conveyance motor205, and the feed motor206are DC motors. These motors are driven by PWM control. The PWM signal output to each driver is expressed by a duty value (ratio of the high level to the low level and the ratio of on and off). The duty value ranges from 0% to 100%. The larger the duty value, the greater the power supplied to the motor.

Here, in the present embodiment, in order to suppress a temperature rise of the conveyance motor205, the conveyance motor205determines whether or not it is in a temperature rising state. The temperature rising state of the conveyance motor205is determined from information of a PWM value when the conveyance motor205is driven in the printing operation (described later). Specifically, the number of times when the PWM value during driving the conveyance motor205exceeds the threshold value is counted, and a “temperature rising state” is determined if the number of times is greater than or equal to a predetermined number of times and a “non-temperature rising state” is determined if the number of times is less than the predetermined number of times. In a case where the conveyance motor205is determined to be in a temperature rising state, the speed of the conveyance motor205for the printing operation is switched to a low-speed drive. By this, a temperature rise of the conveyance motor is suppressed. Incidentally, temperature rise determination of the conveyance motor205is performed every time the conveyance motor205for the printing operation is driven. Note, although the temperature rising state of the motor is determined based on the information of the PWM value, a temperature sensor for detecting the temperature of the motor may be provided separately, and in a case where the temperature information is equal to or greater than a predetermined temperature, this may be determined as a temperature rising state.

A printer driver2141for collectively communicating printing information such as a print image and a print image quality with the printing apparatus is arranged in the host computer214in a case where a user commands the execution of the printing operation. The MPU201executes an exchange of a print image and the like with the host computer214through an I/F unit213.

By using ST1ofFIG.1to ST10ofFIG.4, operation of the overlapped continuous feeding (operation for overlapping the leading edge of a succeeding sheet on the trailing edge of a preceding sheet and conveying the sheet) is described. When the printing data is transmitted from the host computer214through the I/F unit213, the printing data is processed by the MPU201and then loaded into the RAM203. The MPU201starts the printing operation based on the loaded data.

Description is given with reference to ST1ofFIG.1. First, the feed motor206is driven at a low speed by the feed motor driver210. As a result, the pick-up roller2is rotated at 7.6 inch/sec. When the pick-up roller2rotates, the uppermost printing sheet (a preceding sheet1-A) stacked on the feeding tray11is picked up. The preceding sheet1-A picked up by the pick-up roller2is conveyed by the feeding roller3rotating in the same direction as the pick-up roller2. The feeding roller3is also driven by a feed motor206. The present embodiment is described with a configuration including the pick-up roller2and the feeding roller3. However, it may be configured to include only a feeding roller for feeding the printing sheets stacked in the stacking unit.

When the leading edge of the preceding sheet1-A is detected by the first sheet detection sensor16provided near the downstream side of the feeding roller3, the feed motor206switches to the high-speed drive. That is, the pick-up roller2and the feeding roller3rotate at 20 inch/sec.

Description is given with reference to ST2ofFIG.1. By continuing to rotate the feeding roller3, the leading edge of the preceding sheet1-A causes the sheet holding lever17to rotate clockwise about the rotation shaft17b, which is against the biasing force of the spring. Furthermore, when the feeding roller3is continuously rotated, the leading edge of the preceding sheet1-A is detected by the second sheet detection sensor18, and then abuts the conveying nip portion formed by the conveyance roller5and the pinch roller6. At this time the conveyance roller5is in a stopped state. The leading edge of the preceding sheet1-A is aligned in a state in which it abuts the conveying nip portion by the feeding roller3being rotated by a predetermined amount based on the first sheet detection sensor16even after the leading edge of the preceding sheet1-A abuts the conveying nip portion, and thereby skew is corrected. The skew correction operation may also be called a registration operation.

Description is given with reference to ST3ofFIG.1. When the skew correction operation for the preceding sheet1-A is completed, the conveyance roller5starts to rotate by the conveyance motor205being driven. The conveyance roller5conveys the sheet at 15 inch/sec. After the leading edge of the preceding sheet1-A is cued to a position facing the printing head7, the printing operation is performed by ejecting inks from the printing head7based on the printing data. Note, the cuing operation is performed by the leading edge of the printing sheet being temporarily aligned at the position of the conveyance roller5by abutting the conveying nip portion and then by the rotation amount of the conveyance roller5being controlled with reference to the position of the conveyance roller5.

The printing apparatus of the present embodiment is a serial type printing apparatus in which a printing head7is mounted on the carriage10. A printing operation for a printing sheet is performed by repeating a conveying operation in which the printing sheet is intermittently conveyed by the conveyance roller5by intermittently driving the conveyance motor205by a predetermined amount and an image forming operation in which ink is ejected from the printing head7while moving the carriage10on which the printing head7is mounted when the conveyance roller5is stopped. Each time the conveyance motor205is driven intermittently, it performs a determination as to whether the temperature of the conveyance motor205has risen. In a case where the conveyance motor205is determined to be in a temperature rising state, the conveyance motor205switches from the next drive to the low-speed drive, and conveys the sheet at 10 inches/sec.

When the preceding sheet1-A is cued, the feed motor206switches to the low-speed drive. That is, the pick-up roller2and the feeding roller3rotate at 7.6 inch/sec. When the printing sheets are intermittently conveyed per a predetermined amount by the conveyance roller5, the feeding roller3is also intermittently driven by the feed motor206. Specifically, the feeding roller3is also rotated when the conveyance roller5is rotating, and the feeding roller3is also stopped when the conveyance roller5is stopped. With respect to the rotation speed of the conveyance roller5, the rotation speed of the feeding roller3is small. Therefore, the sheet is pulled between the conveyance roller5and the feeding roller3. Further, the feeding roller3is rotated by the printing sheet conveyed by the conveyance roller5.

In order to drive the feed motor206intermittently, the drive shaft19is also driven. As described above, the rotation speed of the pick-up roller2is smaller than the rotation speed of the conveyance roller5. For this reason, the pick-up roller2is caused to be rotated by the printing sheet conveyed by the conveyance roller5. That is, the pick-up roller2rotates ahead with respect to the drive shaft19. Specifically, the projection19aof the drive shaft19is separated from the first surface2aand contacts the second surface2b. As a result, even if the trailing edge of the preceding sheet1-A passes through the pick-up roller2, the second printing sheet (the succeeding sheet1-B) is not immediately picked up. When the drive shaft19is driven for a predetermined time, the projection19acomes in contact with the first surface2a, and the pick-up roller2starts to rotate.

Description is given with reference to ST4ofFIG.2. A state in which the pickup roller2has started to rotate and has picked up the succeeding sheet1-B is illustrated. The first sheet detection sensor16requires a predetermined interval or more between the sheets in order to detect the leading edge of the printing sheet due to factors such as the response of the sensor. That is, a predetermined distance between the trailing edge portion of the preceding sheet1-A and the leading edge portion of the succeeding sheet1-B is required in order to provide a predetermined time interval before detecting the leading edge of the succeeding sheet1-B after the trailing edge of the preceding sheet1-A is detected by the first sheet detection sensor16. Therefore, the concave portion2cof the pick-up roller2is set to about 70 degrees.

Description is given with reference to ST5ofFIG.2. The succeeding sheet1-B picked up by the pick-up roller2is conveyed by the feeding roller3. At this time, for the preceding sheet1-A, an image forming operation is performed by the printing head7based on the printing data. When the leading edge of the succeeding sheet1-B is detected by the first sheet detection sensor16, the speed of the feed motor206switches in accordance with the temperature rising state of the conveyance motor205in the present embodiment.

Here, in the present embodiment, in a case where the conveyance motor205is in a temperature rising state, in order to suppress the temperature rise of the conveyance motor205, the rotational speed of the conveyance motor205is reduced and also the overlapped continuous feeding operation is not performed. That is, the operation of overlapping the leading edge of the succeeding sheet1-B on the trailing edge of the preceding sheet1-A is not performed. Specifically, the conveyance motor205switches from a normal conveyance speed of 15 inches/sec to a conveyance speed of 10 inches/sec, which is a low-speed drive. Also, the speed of the feed motor206is driven in synchronism with the conveyance motor205without changing the low-speed drive (7.6 inch/sec). Since the rotation speed of the conveyance motor205is higher than the rotation speed of the feed motor206, and the conveyance motor205and the feed motor206are synchronously driven, the succeeding sheet1-B does not catch up with the preceding sheet1-A, and an overlapping state is not formed.

ST10ofFIG.4shows a state in which the printing operation on the preceding sheet1-A is completed. Since the trailing edge of the preceding sheet1-A and the leading edge of the succeeding sheet1-B do not overlap with each other due to the driving of the motor as described above, the leading edge of the succeeding sheet1-B can be detected by the second sheet detection sensor18. In other words, the leading edge position of the succeeding sheet1-B can be calculated from the rotational amount of the feeding roller3based on the position of the second sheet detection sensor18rather than the position of the first sheet detection sensor16. Therefore, the skew correction operation for the succeeding sheet1-B can be performed by driving the feeding roller3by the skew correction conveyance amount with reference to the second sheet detection sensor18, and the skew correction operation can be performed accurately. Since the second sheet detection sensor18is closer to the conveying nip portion of the conveyance roller5than the first sheet detection sensor16, if the position (detection result) is used as a reference, the leading edge position of the succeeding sheet1-B can be controlled more accurately than if the position of the first sheet detection sensor16is used as a reference.

On the other hand, in a case where the conveyance motor is not in a temperature rising state, the feed motor206switches to the high-speed drive, the overlapped continuous feeding operation is performed. That is, the pick-up roller2and the feeding roller3rotate at 20 inch/sec.

Description is given with reference to ST6ofFIG.2. The trailing edge portion of the preceding sheet1-A is pressed downward by the sheet holding lever17as illustrated in ST5ofFIG.2and the preceding sheet1-A is detected by the second sheet detection sensor18. Since the printing operation is being performed on the preceding sheet1-A based on the printing data, the preceding sheet1-A is intermittently conveyed by the conveyance roller5at a normal rotational speed of 15 inches/sec. On the other hand, since the feeding roller3is consecutively driven at a high speed to convey the succeeding sheet1-B, the distance between the trailing edge of the preceding sheet1-A and the leading edge of the succeeding sheet1-B becomes smaller. If the conveyance motor remains in the non-temperature rising state, it is possible to form a state in which the trailing edge portion of the succeeding sheet1-B overlaps the leading edge portion of the preceding sheet1-A (ST6ofFIG.2) due to the continuous driving of the feeding roller3.

Even during high-speed driving of the feeding roller3, the conveyance motor205is intermittently driven for the printing operation, and the temperature rise determination is performed every time a drive is performed. In a case where the conveyance motor205is in the temperature rising state, if the rotation amount of the feeding roller3after starting the high-speed driving is shorter than the distance between the first sheet detection sensor16and the second sheet detection sensor18, the driving of the feeding roller3is stopped to stop the overlapped continuous feeding operation. Also, in this instance, when the printing operation for the preceding sheet1-A is completed, the state is as illustrated in ST10ofFIG.4.

In this way, the leading edge of the succeeding sheet1-B can be detected by the second sheet detection sensor18by not overlapping the trailing edge of the preceding sheet1-A and the leading edge of the succeeding sheet1-B. Therefore, as already described, by driving the feeding roller3by the skew correction conveying amount with the second sheet detection sensor18as a reference, it is possible to accurately perform the skew correction operation for the succeeding sheet1-B.

Description is given with reference to ST7ofFIG.3. After forming an overlapping state in which the leading edge portion of the succeeding sheet1-B overlaps the trailing edge portion of the preceding sheet1-A, the succeeding sheet1-B is conveyed by the feeding roller3until the leading edge stops at a predetermined position upstream of the conveying nip. When the overlapping state is formed, it is impossible to detect the leading edge of the succeeding sheet1-B by the second sheet detection sensor18since the second sheet detection sensor18detects the preceding sheet1-A. Therefore, the position of the leading edge of the succeeding sheet1-B is calculated from the rotational amount of the feeding roller3after the leading edge of the succeeding sheet1-B is detected by the first sheet detection sensor16, and is controlled based on the calculation result. At this time, for the preceding sheet1-A, an image forming operation is performed by the printing head7based on the printing data.

Description is given with reference to ST8ofFIG.3. When the conveyance roller5is stopped in order to perform an image forming operation (ink ejection operation) of the last line of the preceding sheet1-A, the leading edge of the succeeding sheet1-B abuts the conveying nip portion by the feeding roller3being driven, and the skew correction operation for the succeeding sheet1-B is performed. At this time, as already described, since the second sheet detection sensor18is detecting the preceding sheet1-A, it is impossible to detect the leading edge of the succeeding sheet1-B. Therefore, the driving amount of the feed motor206for skew correction operation of the succeeding sheet1-B becomes a predetermined amount based on the first sheet detection sensor16.

Description is given with reference to ST9ofFIG.3. When the image forming operation of the last line of the preceding sheet1-A is completed, it is possible to cue the succeeding sheet1-B while maintaining a state in which the succeeding sheet1-B overlaps the preceding sheet1-A by rotating the conveyance roller5by a predetermined amount. The printing operation is performed on the succeeding sheet1-B by the printing head7based on printing data. When the succeeding sheet1-B is intermittently conveyed for the printing operation, the preceding sheet1-A is also intermittently conveyed, and eventually, the preceding sheet1-A is discharged to the outside of the printing apparatus by the discharge roller9.

Incidentally, when the succeeding sheet1-B is cued, in preparation for the printing operation for the succeeding sheet1-B, the feed motor206switches to the low-speed drive. That is, the pick-up roller2and the feeding roller3rotate at 7.6 inch/sec. In a case where there is printing data even after the succeeding sheet1-B, ST4ofFIG.2is returned to and a third pick-up operation is performed.

FIG.7AtoFIG.7Eare flowcharts of an overlapped continuous feeding operation in the embodiment. In step S1, when the printing data is transmitted from the host computer214through the I/F unit213, the printing operation is started. In step S2, the feeding operation of the preceding sheet1-A is started. Specifically, the feed motor206is driven at a low speed. That is, the pick-up roller2and the feeding roller3rotate at 7.6 inch/sec. The preceding sheet1-A is picked up by the pick-up roller2, and the preceding sheet1-A is fed toward the printing head7by the feeding roller3.

In step S3, the leading edge of the preceding sheet1-A is detected by the first sheet detection sensor16. When the leading edge of the preceding sheet1-A is detected by the first sheet detection sensor16, the feed motor206switches to the high-speed drive in step S4. That is, the pick-up roller2and the feeding roller3rotate at 20 inch/sec. After this, the leading edge of the preceding sheet1-A is detected by the second sheet detection sensor18. After the leading edge of the preceding sheet1-A is detected by the second sheet detection sensor18, the leading edge position of the preceding sheet1-A is controlled by the rotation amount of the feeding roller3with reference to the position of the second sheet detection sensor18. In step S5, by controlling the leading edge position, the leading edge of the preceding sheet1-A is abutted against the conveying nip portion and the skew correction operation for the preceding sheet1-A is performed.

In step S6, the preceding sheet1-A is cued based on the printing data. That is, by controlling the rotational amount of the conveyance roller5, the preceding sheet1-A is conveyed to the printing start position with reference to the position of the conveyance roller5based on the printing data. The feed motor206switches to the low-speed drive (7.6 inch/sec) in step S7. In step S8, the printing operation is started by ejecting the ink from the printing head7to the preceding sheet1-A. Specifically, a conveying operation in which the preceding sheet1-A is intermittently conveyed at a conveying speed of 15 inches/sec, which is a normal speed, by the conveyance roller5, and an image forming operation (ink ejection operation) in which the carriage10is moved to eject ink from the printing head7are repeated. As a result, the printing operation for the preceding sheet1-A is performed. The feed motor206is driven at a low speed intermittently in synchronization with the operation of intermittently conveying the preceding sheet1-A by the conveyance roller5. That is, the pick-up roller2and the feeding roller3intermittently rotate at 7.6 inch/sec.

In step S9, it is determined whether or not there is printing data for the next page. If there is no printing data for the next page, the process proceeds to step S28. When the printing operation on the preceding sheet1-A is completed in step S28, the preceding sheet1-A is discharged and the printing operation is terminated in step S29.

If there is printing data for the next page in step S9, the feeding operation of the succeeding sheet1-B is started in step S10. Specifically, the succeeding sheet1-B is picked up by the pick-up roller2, and the succeeding sheet1-B is fed toward the printing head7by the feeding roller3. That is, the pick-up roller2and the feeding roller3rotate at 7.6 inch/sec. As described above, since the concave portion2cof the pick-up roller2is arranged to be large with respect to the projection19aof the drive shaft19, the succeeding sheet1-B is fed with a predetermined distance from the trailing edge of the preceding sheet1-A.

In step S11, the printing operation on the preceding sheet1-A is continued by the printing head7.

In step S12, when the leading edge of the succeeding sheet1-B is detected by the first sheet detection sensor16, the temperature rising state of the conveyance motor205is determined in step S13, and the driving method of the feed motor206is switched. If the conveyance motor205is not in the temperature rising state, the overlapped continuous feeding operation is continued and the feed motor206switches to the high-speed drive in step S14. That is, the pick-up roller2and the feeding roller3rotate at 20 inch/sec. The preceding sheet1-A is intermittently conveyed at a rate of 15 inches/sec based on the printing data, and the printing is continued. Each time the conveyance motor205is driven intermittently, temperature rise determination is performed.

It is determined whether to continue the overlapped continuous feeding operation from the temperature rising state of the conveyance motor205and the rotation amount of the feeding roller3in step S15. In a case where, in the middle of the high-speed driving of the feeding roller, the conveyance motor205is determined to be in the temperature rising state, if the rotation amount of the feeding roller3after the start of the high-speed driving is shorter than the distance between the first sheet detection sensor16and the second sheet detection sensor18, the overlapped continuous feeding operation stops and the processing advances to step S39. Otherwise, the overlapped continuous feeding operation is continued and the processing advances to step S16.

In step S16, by controlling the rotational amount of the feeding roller3after the leading edge of the succeeding sheet1-B is detected by the first sheet detection sensor16, the succeeding sheet1-B is conveyed so that the leading edge of the succeeding sheet1-B is positioned in front of the conveying nip portion by a predetermined amount. The preceding sheet1-A is intermittently conveyed at a rate of 15 inches/sec based on the printing data. The succeeding sheet1-B is continuously driven at a high speed of 20 inches/sec by the feed motor206to catch up with the preceding sheet1-A, and an overlapping state in which the leading edge portion of the succeeding sheet1-B overlaps the trailing edge portion of the preceding sheet1-A is formed.

In step S17, it is determined whether a predetermined condition (described later) is satisfied. In a case where the predetermined condition is satisfied, it is determined in step S18whether the image forming operation of the last line of the preceding sheet1-A is started. In a case where the image forming operation of the last line is started, the processing advances to step S19, and when it is not started, the processing waits until it is started. In step S19, the leading edge of the succeeding sheet1-B is abutted against the conveying nip portion while maintaining the overlapping state and the skew correction operation for the succeeding sheet1-B is performed. In a case where it is determined in step S20that the image forming operation of the last line of the preceding sheet1-A is completed, the succeeding sheet1-B is cued while maintaining the overlapping state in step S21.

In a case where the predetermined condition is not satisfied in step S17, the overlapping state is cancelled and the succeeding sheet1-B is cued. Specifically, when the image forming operation of the last line of the preceding sheet1-A is completed in step S30, a discharging operation of the preceding sheet1-A is performed in step S31. During this time, since the feed motor206is not driven, the succeeding sheet1-B is stopped while the leading edge thereof is in a position in front of the conveying nip portion by a predetermined amount. Since the preceding sheet1-A is discharged, the overlapping state is released. In step S32, the leading edge of the succeeding sheet1-B is abutted against the conveying nip portion and the skew correction operation for the succeeding sheet1-B is performed. Then, in step S21, the succeeding sheet1-B is cued.

The feed motor206switches to the low-speed drive in step S22. That is, the pick-up roller2and the feeding roller3rotate at 7.6 inch/sec.

Meanwhile, if the conveyance motor205in step S13was in the temperature rising state, the processing would advance to step S33without performing the overlapped continuous feeding operation. The conveyance motor205switches to a conveying speed of 10 inch/sec, which is a low-speed drive, and the speed of the feed motor206is left unchanged at low-speed drive (7.6 inch/sec), and the feed motor206is driven in synchronism with the conveyance motor205. After the printing operation on the preceding sheet1-A is completed in step S34, the preceding sheet1-A is discharged in step S35.

If it is determined in step S15that the overlapped continuous feeding operation is to be stopped, the processing advances to step S39. In step S39, the printing operation of the preceding sheet1-A is continued by switching the conveyance motor205to the low-speed drive (10 inch/sec). At the same time, the feed motor206is stopped to stop the conveyance of the succeeding sheet1-B. After the printing operation on the preceding sheet1-A is completed in step S40, the preceding sheet1-A is discharged in step S41.

In step S36, the leading edge of the succeeding sheet1-B is abutted against the conveying nip portion and the skew correction operation for the succeeding sheet1-B is performed. At this time, the leading edge of the succeeding sheet1-B can be detected by the second sheet detection sensor18since the trailing edge of the preceding sheet1-A and the leading edge of the succeeding sheet1-B are not overlapping. Therefore, by driving the feed motor206only the skew correction conveying amount with reference to the second sheet detection sensor18, the skew correction operation for the succeeding sheet1-B is performed. Then, in step S37, the succeeding sheet1-B is cued.

In step S23, the printing operation is started by ejecting the ink from the printing head7to the succeeding sheet1-B. Specifically, the printing operation for the succeeding sheet1-B is performed by repeating the conveyance operation for intermittently conveying the succeeding sheet1-B by the conveyance roller5and the image forming operation (ink ejection operation) of causing the carriage10to move and ejecting ink from the printing head7. The feed motor206is driven at a low speed intermittently in synchronization with the operation of intermittently conveying the succeeding sheet1-B by the conveyance roller5at a speed of 15 inch/sec. That is, the pick-up roller2and the feeding roller3intermittently rotate at 7.6 inch/sec.

In step S24, it is determined whether or not there is printing data for the next page. If there is no printing data for the next page, the process returns to step S10. In a case where there is no printing data of the next page, when the image forming operation of the succeeding sheet1-B is completed in step S25, the discharging operation of the succeeding sheet1-B is performed in step S26, and the printing operation is completed in step S27.

FIG.8andFIG.9are views for describing an operation of overlapping a succeeding sheet on a preceding sheet in the present embodiment. Description is given of an operation of forming an overlapping state in which the leading edge portion of the succeeding sheet overlaps the trailing edge portion of the preceding sheet as described in step S16ofFIG.7D.

FIG.8andFIG.9are enlarged views of a feeding nip portion formed by the feeding roller3and the feeding pinch roller4and a conveying nip portion formed by the conveyance roller5and the pinch roller6.

A process in which the printing sheet is conveyed by the conveyance roller5and the feeding roller3is described in order as three states. With reference to ST1and ST2ofFIG.8, a first state in which an operation in which a succeeding sheet follows a preceding sheet will be described. With reference to ST3and ST4ofFIG.9, a second state in which an operation in which a succeeding sheet overlaps a preceding sheet will be described. With reference to ST5ofFIG.9, a third state in which it is determined whether or not the skew correction operation for the succeeding sheet is performed while maintaining the overlapping state is described.

In ST1ofFIG.8, the feeding roller3is controlled to convey the succeeding sheet1-B, and the leading edge of the succeeding sheet1-B is detected by the first sheet detection sensor16. A position P1at which the succeeding sheet1-B from the first sheet detection sensor16can be overlapped on the preceding sheet1-A is defined as a first section A1. In the first section A1, an operation in which the leading edge of the succeeding sheet1-B follows the trailing edge of the preceding sheet1-A is performed. Specifically, the conveyance control of the succeeding sheet1-B is performed so that the distance between the trailing edge of the preceding sheet1-A and the leading edge of the succeeding sheet1-B becomes 10 mm. P1is determined by the configuration of the mechanism.

In the first state, in the first section A1, there is a case in which the driving of the feed motor206is stopped to stop the conveyance of the succeeding sheet1-B. That is, there is a case where the following operation is stopped. This prevents the leading edge of the succeeding sheet1-B from overtaking the trailing edge of the preceding sheet1-A before P1, as in ST2ofFIG.8. When the trailing edge of the preceding sheet1-A and the leading edge of the succeeding sheet1-B are separated by 10 mm or more after the driving of the feed motor206is stopped, the driving of the feed motor206is restarted and the conveyance of the succeeding sheet1-B is restarted. Thus, while the leading edge of the succeeding sheet1-B is conveyed in the first section A1, the feed motor206may repeat driving and stopping.

In ST3ofFIG.9, the above-described position P1to the position P2where the sheet holding lever17is provided is defined as a second section A2. In the second section A2, an operation in which the succeeding sheet1-B is overlapped on the preceding sheet1-A is performed.

In the second state, in the second section A2, there is a case where the operation of overlapping the succeeding sheet on the preceding sheet is stopped. As in ST4ofFIG.9, in a case where the leading edge of the succeeding sheet1-B cannot catch up with the trailing edge of the preceding sheet1-A in the second section A2, the operation of overlapping the preceding sheet on the succeeding sheet cannot be performed.

In ST5ofFIG.9, the above-mentioned P2to P3are defined as the third section A3. P3is the position of the leading edge when the succeeding sheet is stopped in step S16ofFIG.7D. The succeeding sheet1-B is conveyed while being overlapped on the preceding sheet1-A until the leading edge of the succeeding sheet1-B reaches P3. In the third section A3, it is determined whether or not the succeeding sheet1-B abuts the conveying nip portion and cuing is performed, while maintaining the overlapping state. Specifically, it is determined whether the skew correction operation and cuing is performed by maintaining the overlapping state or whether the skew correction operation and cuing is performed by releasing the overlapping state.

FIG.10is a flowchart illustrating a skew correction operation of the succeeding sheet in the embodiment. Determination of whether or not the predetermined condition described in step S17ofFIG.7Dis satisfied is described in detail.

An operation of determining whether to perform the skew correction operation by abutting the leading edge of the succeeding sheet1-B against the conveying nip portion while maintaining the overlapping state of the preceding sheet1-A and the succeeding sheet1-B, or to perform the skew correction operation by abutting the leading edge of the succeeding sheet1-B against the conveying nip portion after releasing the overlapping state of the preceding sheet1-A and the succeeding sheet1-B is described.

Processing starts in step S101. In step S102, it is determined whether or not the leading edge of the succeeding sheet1-B has reached the determination position (P3of ST5ofFIG.9). Here, if not reached (step S102: NO), since it is unknown whether the leading edge of the succeeding sheet1-B abuts the conveying nip portion at a predetermined amount of conveyance, it is determined that the skew correction operation is to be performed only for the succeeding sheet (step S103), and the determination operation ends (step S104). That is, after the trailing edge of the preceding sheet1-A passes through the conveying nip portion, only the succeeding sheet1-B abuts against the conveying nip portion to perform the skew correction operation, and thereafter, cuing is performed in the condition where only the succeeding sheet1-B is present.

On the other hand, when the leading edge of the succeeding sheet1-B has reached the determination position P3(step S102: YES), it is determined whether the trailing edge of the preceding sheet1-A has passed through the conveying nip portion (step S105). If it is determined that the sheet has passed through (step S105: YES), since the preceding sheet and the succeeding sheet do not overlap each other, the skew correction operation for only the succeeding sheet is determined (step S106). That is, only the succeeding sheet1-B abuts against the conveying nip portion to perform the skew correction operation, and thereafter, the cuing is performed in a state where only the succeeding sheet1-B is present.

On the other hand, when it is determined that the trailing edge of the preceding sheet1-A does not pass through the conveying nip portion (step S105: NO), it is determined whether the overlap amount between the trailing edge portion of the preceding sheet1-A and the leading edge portion of the succeeding sheet1-B is smaller than a threshold (step S107). The position of the trailing edge of the preceding sheet1-A is updated in accordance with the printing operation for the preceding sheet1-A. The position of the leading edge of the succeeding sheet1-B is the aforementioned determination position. That is, the overlap amount will decrease along with the printing operation of the preceding sheet1-A. If it is determined that the overlap amount is smaller than the threshold value (step S107: YES), the overlapping state is released and the skew correction operation for only the succeeding sheet is determined (step S108). That is, after the image forming operation of the preceding sheet1-A is completed, the succeeding sheet1-B is not conveyed together with the preceding sheet1-A. Specifically, the conveyance roller5is driven by the conveyance motor205to convey the preceding sheet1-A. However, the feeding roller3is not driven. Therefore, the overlapping state is released. Furthermore, only the succeeding sheet1-B abuts against the conveying nip portion to perform the skew correction operation, and thereafter, the cuing is performed in a state where only the succeeding sheet1-B is present.

If it is determined that the overlap amount is greater than or equal to the threshold value (step S107: NO), it is determined whether or not the succeeding sheet1-B reaches the pressing spur12when the succeeding sheet1-B is cued (step S109). If it is determined that the succeeding sheet1-B has not reached the pressing spur12(step S109: NO), the overlapping state is released and the skew correction operation for only the succeeding sheet is determined (step S110). That is, after the image forming operation of the preceding sheet1-A is completed, the succeeding sheet1-B is not conveyed together with the preceding sheet1-A. Specifically, the conveyance roller5is driven by the conveyance motor205to convey the preceding sheet1-A. However, the feeding roller3is not driven. Therefore, the overlapping state is released. Furthermore, only the succeeding sheet1-B abuts against the conveying nip portion to perform the skew correction operation, and thereafter, the cuing is performed in a state where only the succeeding sheet1-B is present.

If it is determined that the succeeding sheet1-B reaches the pressing spur12(step S109: YES), it is determined whether or not there is a gap between the last line of the preceding sheet and the line preceding the last line (step S111). If it is determined that there is no gap (step S111: NO), the overlapping state is released and the skew correction operation for only the succeeding sheet is determined (step S112). If it is determined that there is a gap (step S111: YES), the skew correction operation for the succeeding sheet1-B is performed while maintaining the overlapping state, and then, cuing is performed. That is, after the image forming operation of the preceding sheet1-A is completed, the succeeding sheet1-B is abutted against the conveying nip portion in a state in which it overlaps the preceding sheet1-A. Specifically, the conveyance roller5and the feeding roller3are rotated by driving the feed motor206simultaneously with the conveyance motor205. After the skew correction operation, the succeeding sheet1-B is cued while being overlapped with the preceding sheet1-A.

In this way, the determination operation is performed to determine whether the preceding sheet1-A and the succeeding sheet1-B are maintained in the overlapping state or released.

FIG.11is a flowchart for describing a configuration for calculating the leading edge position after cuing the succeeding sheet in the embodiment.

Processing starts in step S201. In step S202, the printable area of the sheet size is read. Since the leading printable position, in other words, the upper edge margin, is specified, the upper edge margin of the printable area is set to the leading edge position (step S203). Here, the leading edge position is defined by the distance from the conveying nip portion.

Next, first printing data is read (step S204). As a result, the position of the first printing data from the leading edge of the sheet is specified (the non-printing area is detected), and therefore, it is determined whether the distance from the leading edge of the sheet to the first printing data is larger than the leading edge position set previously (step S205). If the distance from the leading edge of the sheet to the first printing data is larger than the leading edge position set earlier (step S205: YES), the leading edge position is updated to the distance from the leading edge of the sheet to the first printing data (step S206). If the distance from the leading edge of the sheet to the first printing data is less than or equal to the leading edge position set earlier (step S205: NO), the processing advances to step S207.

Next, a first carriage-moving command is generated (step S207). Next, a determination is made as to whether or not the sheet conveyance amount for the first carriage movement is larger than the previously set leading edge position (step S208). If the sheet conveyance amount for the first carriage movement is larger than the previously set leading edge position (step S208: YES), the leading edge position is updated to the sheet conveyance amount for the first carriage movement (step S209). If the sheet conveyance amount for the first carriage movement is less than or equal to the leading edge position set previously (step S208: NO), the leading edge position is not updated. As described above, the leading edge position of the succeeding sheet1-B is determined (step S210), and the processing ends (step S211). Based on the determined leading edge position, it is possible to determine whether or not the succeeding sheet1-B reaches the pressing spur12when the succeeding sheet1-B is cued (FIG.10: step S109).

As described above, by virtue of the above-described embodiment, in a case where the conveyance motor205rises in temperature and the driving speed during the overlapped continuous feeding is reduced, the overlapped continuous feeding operation is stopped, and the leading edge of the succeeding sheet1-B is detected by the second sheet detection sensor18to thereby enable satisfactory skew correction of the succeeding sheet1-B.

Second Embodiment

Next, a printing apparatus according to the second embodiment of the present invention is described. In the first embodiment, a printing apparatus in which the overlapped continuous feeding operation is not performed when the conveyance motor205is in a temperature rising state was described. In the second embodiment, the temperature rise determination is also performed for the feed motor206. If the feed motor206is determined to be in a temperature rising state during the overlapped continuous feeding, the feeding speed of the feed motor206is not increased, and the overlapped continuous feeding operation is not performed. Furthermore, the leading edge of the succeeding sheet1-B is detected by the second sheet detection sensor18and the skew correction is performed. Thus, it is possible to perform satisfactory skew correction of the succeeding sheet1-B while suppressing a temperature rise of the conveyance motor205and the feed motor206.

This application claims the benefit of Japanese Patent Application No. 2020-217371, filed Dec. 25, 2020, which is hereby incorporated by reference herein in its entirety.