Printer and printer control method

A printer includes a media stacking section, a print section, a pickup roller, a relay roller, a common actuator, a transport mechanism section and a control section. The control section is configured to control the common actuator based on a print job and displacement of the printing media. The control section is configured to stop transferring of driving force of the common actuator from the pickup roller to an nth printing medium after the pickup roller draws out the nth printing medium and the relay roller starts to send out the nth printing medium which is drawn out in a case where a print job, where printing is carried out on n of the printing media with a length in a transport direction shorter than a transport distance of the printing media from the pickup roller to the print section, is processed in the continuous transport mode.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese Patent Application No. 2013-162064 filed on Aug. 5, 2013. The entire disclosure of Japanese Patent Application No. 2013-162064 is hereby incorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates to a printer and a printer control method.

2. Related Art

Printers in the prior art are provided with a pickup roller which draws out sheets which are stacked one sheet at a time and a relay roller which sends out the sheets which are drawn out by the pickup roller to a print section. The print section is provided with a sensor which detects the passing of an edge of the sheet, a transport roller which transports the sheet with the position of the edge of the sheet which is detected by the sensor as a reference, and a print head which carries out printing on the sheet which is transported by the transport roller. In recent years, printers which operate in a so-called continuous transport mode, where transporting of the succeeding sheet starts before printing on the preceding sheet is complete, are widespread and the time which is necessary to print a plurality of sheets is shortened (Japanese Unexamined Patent Application Publication No. 2009-155037).

SUMMARY

Here, it is possible to reduce manufacturing costs of the printer by the pickup roller, the relay roller, and the transport roller being driven using one motor, but there is the following problem in the continuous transport mode in a case where the sheet transport distance from the pickup roller to the print section exceeds the length of the sheet. (Here, the interval between the preceding and succeeding sheets which are transported is ignored in order for easier understanding.)

At a point in time when the rear edge of one of the sheets reaches the print section during printing, the pickup roller starts transporting of the sheet which follows the succeeding sheet if the pickup roller, the relay roller, and the transport roller are rotated simultaneously using one motor in the continuous transport mode in a case where the sheet transport distance from the pickup roller to the print section exceeds the length of the sheet. Accordingly, a sheet where printing is not carried out in a print job is unintentionally drawn out by the pickup roller even when the pickup roller is stopped at a point in time when the rear edge of the sheet, which is the n−1thsheet in a print job where printing is carried out on n of the sheets, reaches the print section. On the other hand, continuous transporting is interrupted between the n−1thsheet and the nthsheet when the pickup roller is stopped at a point in time when the rear edge of the sheet, which is the n−2thsheet in a print job where printing is carried out on n of the sheets, reaches the print section.

Accordingly, it is imperative that a lower limit according to the transport distance be provided for the length of the sheet which is able to be used in the continuous transport mode in order to prevent such a problem before it happens in the printers in the prior art. In addition, if the lower limit of the length of the sheet which is able to be used in continuous transport mode is set to the length of a standard sheet with a high frequency of use, the sheet transport distance from the pickup roller to the print section is restricted according to the length of the standard sheet. On the other hand, it is necessary that the sheet transport distance from the pickup roller to the print section be lengthened according to the length of the sheet so that double-sided printing is possible.

The present invention has been created in order to solve such a problem and has an object of providing a printer where all sheets which are used in a print job are continuously transported irrespective of the length of the sheets or the transport distance of the sheets.

(1) A printer which is for achieving the object described above is provided with a media stacking section where printing media are stacked, a print section which is provided with a transport roller which transports the printing media and a print head which prints on the printing media which are transported by the transport roller, a pickup roller which draws out the printing media from the media stacking section, a relay roller which is arranged at a position between the pickup roller and the transport roller and sends out the printing media which are drawn out by the pickup roller to the print section, a common actuator which drives the pickup roller, the relay roller, and the transport roller, a transport mechanism section which transfers the driving force of the common actuator to the printing media via the pickup roller, the relay roller, and the transport roller, and a control section which controls the common actuator based on a print job and displacement of the printing media where, in a period of time when printing is being carried out on a certain printing medium by the print section, other printing media are transported using the pickup roller and the relay roller in a continuous transport mode, wherein the control section stops transfer of the driving force of the common actuator from the pickup roller to an nthprinting medium after the pickup roller draws out the nthprinting medium and the relay roller starts to send out the nthprinting medium which is drawn out in a case where a print job, where printing is carried out on n of the printing media (where n is an integer of two or more) with lengths in the transport direction shorter than the transport distance of the printing media from the pickup roller to the print section, is processed in the continuous transport mode.

Due to the present invention, the printing media are transported by the pickup roller, the relay roller, and the transport roller which are driven using the one common actuator. Then, the printing media which are not used in a print job are not drawn out by the pickup roller irrespective of the length of the printing media or the transport distance in a case where the printing media are transported in the continuous transport mode in a print job with n of the printing media since, before the pickup roller completes drawing out of the printing medium where printing is carried out last in one print job, transferring of the driving force of the common actuator from the pickup roller to the printing medium which is last is stopped. In addition, it is possible to continuously transport all of the printing media which are used in a print job to the print section since transferring of the driving force of the common actuator from the pickup roller to the printing medium which is last is stopped after the relay roller starts to send out the printing medium which is last.

(2) The printer which achieves the object described above wherein, when the transport distance of the printing media from the pickup roller to the print section is X, the interval between the printing media which line up and are transported as preceding and succeeding printing media in the continuous transport mode is Y, the length of the printing media in the transport direction is Z and N is a quotient X/(Y+Z), the control section may stop transferring of the driving force of the common actuator from the pickup roller to the nthprinting medium before the rear edge of an (n−N)thprinting medium reaches the print section.

In a case where this configuration is adopted, it is possible to continuously transport all of the printing media which are used in a print job to the print section without the printing media which are not used in the print job being drawn out by the pickup roller even when the transport distance of the printing media is equal to or more than double the length of the printing media.

(3) The printer which achieves the object described above which further has a measuring section which measures displacement of the printing media, wherein the measuring section is provided with a sensor which detects passing of an edge of the printing media at a position between the relay roller and the transport roller and the control section may drive the transport roller with the position where the sensor detects the edge of the printing media as a reference, alternately repeat transporting of the printing media using the transport roller and driving of the print head, determine whether or not the nthprinting medium has reached the position of being sent out by the relay roller when the one of the printing media is in the process of being transported, determine whether or not the rear edge of the one of the printing media has passed the sensor when the one of the printing media is in the process of being transported in a case when it is determined that the nthprinting medium has not reached the position of being sent out by the relay roller even when the one of the printing media is in the process of being transported, and execute splitting the process of being transported into two parts of prior transporting where the rear edge of the one of the printing media has not reached the sensor and latter transporting where the rear edge of the one of the printing media has passed the sensor as well as stopping transferring of the driving force of the common actuator from the pickup roller to the nthprinting medium between the prior transporting and the latter transporting in a case when it is determined that the rear edge of the one of the printing media has passed the sensor when the one of the printing media is in the process of being transported.

Since it is possible for displacement of the printing media to be detected using the sensor which is fixed at a position which is close to the print section in a case where this configuration is adopted, it is possible to switch processes from transporting to the print section to printing in the print section at a precise timing and it is possible to precisely control the position of the printing media during printing. In addition, it is possible to stop transferring of the driving force of the common actuator from the pickup roller to the printing media reliably at an appropriate timing while using the sensor to grasp the number of the printing media on which printing has been carried out.

(4) The printer which achieves the object described above wherein the print section may be provided with a carriage which moves back and forth in a direction which is orthogonal to the transport direction of the printing media by being mounted on the print head which discharges ink droplets, the transport mechanism section may have a switching mechanism which switches between a state where the driving force is transferred from the common actuator to the pickup roller and a state where the driving force is not transferred from the common actuator to the pickup roller and which interrupts transferring of the driving force from the common actuator to the pickup roller by abutting with the carriage at a prescribed position and moving along with the carriage, and the control section may stop transferring of the driving force of the common actuator to the pickup roller by moving the carriage to pass the prescribed position.

In regard to the necessary of having a means which switches between a state where the driving force is transferred from the common actuator to the pickup roller and a state where the driving force is not transferred from the common actuator to the pickup roller, it is possible to reduce manufacturing costs of the printer a case when using the present invention since a dedicated actuator for this switching operation is not necessary in a serial ink jet printer which adopts this configuration.

(5) The printer which achieves the object described above wherein the control section may discharge ink droplets from the print head in both of a first period when the carriage is moved in a first direction and a second period when the carriage is moved in a second direction which is the opposite orientation to the first direction, set a stopping flag in a case where it is determined that the nthprinting medium reaches the position of being sent out by the relay roller when the one of the printing media is in the process of being transported, determine whether or not the movement direction of the carriage when transporting the current and previous certain printing media is a direction where the carriage is approaching the switching mechanism when the one of the printing media in the process of being transported, and move the carriage to pass the prescribed position before the one of the printing media in the process of being transported is transported in a case where it is determined that the movement direction of the carriage is the direction where the carriage is approaching the switching mechanism.

In a serial ink jet printer where this configuration is adopted, it is possible to shorten the time for printing since so-called bidirectional printing is performed. Furthermore, it is possible to shorten the time for printing since it is possible to shorten the distance which the carriage moves in order to switch between a state where the driving force is transferred from the common actuator to the pickup roller and a state where the driving force is not transferred from the common actuator to the pickup roller in a serial ink jet printer which adopts this configuration.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Below, an embodiment of the present invention will be described with reference to the attached drawings. Here, the same reference numerals are given to the constituent elements which correspond in each of the diagrams and overlapping descriptions are omitted.

1. Overview of Printer

A configuration of a printer1which is an embodiment of the present embodiment is illustrated inFIG. 1andFIG. 2. The printer1is a serial ink jet type of printer which executes a print job by sending out sheets P which are printing media which are stacked in a sheet supply cassette50one sheet at a time between a platen24and a print head22using a transport mechanism10.

2. Printer Configuration

The sheet supply cassette50which is a media stacking section is a box for stacking a plurality of the sheets P. The sheet supply cassette50is accommodated in the printer body which is not shown in the diagram to be able to be inserted and removed to and from the printer body. A slider501is provided in the sheet supply cassette50. It is possible to align and hold, for example, sheets from photo (89 mm×127 mm) size to A3 size in the sheet supply cassette50by the slider501being moved according to the size of the sheets.

The transport mechanism10includes a pickup roller11, relay rollers12aand13a, a sheet feeding roller14a, a sheet discharge roller15a, a gear train not shown in the diagram which transfers the driving force from a sheet supply motor34which is a common actuator to the rollers, and a switching mechanism19which forms a portion of the gear train which transfers the driving force from the sheet supply motor34to the pickup roller11.

A rotation shaft of the pickup roller11is attached to an arm which is not shown in the diagram and the pickup roller11comes into contact with the upper surface of the sheets P which are stacked in the sheet supply cassette50. The pickup roller11sends out the sheets P toward the relay roller12aby being driven by the sheet supply motor34in a counterclockwise direction inFIG. 1. The sheet supply motor34is driven by a driving circuit33which is controlled by a control section30.

The relay rollers12aand13asend out the sheets P toward the sheet feeding roller14aby being driven by the sheet supply motor34in a counterclockwise direction inFIG. 1. Driven rollers12band12c, which come into contact with the relay roller12aand rotate along with the relay roller12a, are provided in the periphery of the relay roller12awhich is provided at the upstream side of a sheet supply path. Driven rollers13b,13c, and13d, which come into contact with the relay roller13aand rotate along with the relay roller13a, are provided in the periphery of the relay roller13awhich is provided at the downstream side of the sheet supply path. The sheets P are sent out toward the sheet feeding roller14aby being pinched by the relay rollers12aand13aand by the driven rollers12b,12c,13b, and13c.

The sheet feeding roller14awhich is a transport roller rotates along with a driven roller14bby being driven by the sheet supply motor34in a counterclockwise direction inFIG. 1and sends out the sheets P which are pinched between the sheet feeding roller14aand the driven roller14btoward the sheet discharge roller15a. The sheet discharge roller15arotates along with a driven roller15bby being driven by the sheet supply motor34in a counterclockwise direction inFIG. 1and sends out the sheets P which are pinched between the transport roller15aand the driven roller15bonto a stacker which is not shown in the diagram.

A carriage21where the print head22is mounted and the platen24are provided between the sheet feeding roller14aand the sheet discharge roller15a. A discharge port which is not shown in the diagram and which discharges ink droplets is formed in the print head22. The carriage21is supported on a guide rail23to be able to move back and forth in a direction which is orthogonal with regard to the transport direction of the sheets P. The carriage21moves along the guide rail23due to rotation of a carriage motor32. The carriage motor32is driven by a driving circuit31which is controlled by the control section30. Displacement of the carriage21is detected using a linear encoder41which measures displacement of the carriage21and a home position sensor42which detects the carriage21at a home position.

Displacement of the sheets P is measured using a rotary encoder44, which measures the rotation angle of the sheet supply motor34, and a sheet sensor43. That is, the rotary encoder44and the sheet sensor43configure a measuring section. The sheet sensor43is provided in the vicinity of the upstream side of the sheet feeding roller14a. The sheet sensor43is an optical sensor which detects changes in the amount of light incident on the sheet sensor43which accompanies passing of the sheets P. It is possible to switch between a sheet supply process and a print process at a precise timing by using the sheet sensor43which is fixed at a position in the vicinity of the upstream side of the platen24, and it is possible to precisely control the position of the sheets P during printing. In addition, it is possible to stop transferring of the driving force from the sheet supply motor34to the pickup roller11reliably at an appropriate timing while grasping the number of sheets P on which printing has been carried out. Here, the sheet sensor43, the sheet feeding roller14a, the sheet discharge roller15a, the print head22, the platen24, and the like are elements which configure the print section20which is shown inFIG. 2.

The control section30is a computer which is provided with a processor, a memory, a ROM, an inputting and outputting circuit, and the like which are not shown in the diagram. The control section30controls the carriage motor32, the sheet supply motor34, and the print head22in accordance with a sequence which is determined in advance by the processor executing a control program by reading the control program from the ROM into the memory. Printing is carried out on the sheet P by alternately repeating sub-scanning where the sheet P is transported to a prescribed position and main scanning where ink is discharged from the print head22at a specific timing while the print head22is moving. Then, the time for printing is shortened by the control section30executing so-called bidirectional printing. That is, using the control section30, ink droplets are not only discharged from the print head22while the carriage21is moving in a direction of moving away from the home position, but ink droplets are also discharged from the print head22while the carriage21is moving in a direction of approaching the home position.

A guide which is not shown in the diagram is provided in the printer1in order to transport the sheets P along a transport path which is shown by a dotted line inFIG. 1. Here, an origin D0and waypoints D1, D2, D3, D4, D5, D6, D7, D8, D9, and D10are set as follows in the transport path of sheets P.

D0: front edge of the sheet P which is held in the sheet supply cassette50

D1: contact point of the relay roller12aand the driven roller12b

D2: contact point of the relay roller12aand the driven roller12c

D3: contact point of the relay roller13aand the driven roller13b

D4: contact point of the relay roller13aand the driven roller13c

D5: detection position of the sheet sensor43

D6: contact point of the sheet feeding roller14aand the driven roller14b

D7: position of the discharge port on the farthest upstream side of the print head22

D8: position of the discharge port on the farthest downstream side of the print head22

D9: contact point of the sheet discharge roller15aand the driven roller15b

D10: contact point of the relay roller13aand the driven roller13d

Here, a contact point is a contact point in a state where the sheet P is not being transported and is a nip point where the sheet P is transported by being pinched in a state where the sheet P is being transported.

In addition, the length of the sheets in the transport direction is expressed as Z, the length of the sheet which is an A3 size in the translation direction is expressed as Z3, a transport segment from Dnto Dmis expressed as Dn/Dm, and the distance from Dnto Dmis expressed as |Dn/Dm|. The transport mechanism10transfers the driving force of the sheet supply motor34to the pickup roller11, the relay rollers12aand13a, the sheet feeding roller14a, and the sheet discharge roller15aduring double-sided printing so that the rear edge of the sheet P passes in the order of D10, D1, D2, D3, D4, D5, D6, D7, D8, and D9after the front edge of the sheet P has passed in the order of D1, D2, D3, D4, D5, D6, D7, D8, and D9. Accordingly, the printer1is able to carry out double-sided printing with regard to the sheets which satisfy the following equation.
|D5/D10|+|D10/D1|+|D1/D5|>Z

Double-sided printing is possible in the printer1with regard to the sheets P where the following equation is established and which are A3 size or smaller.
|D5/D10|+|D10/D1+|D1/D5|>Z

As a result, the transport segment D0/D5is longer than the length of the sheet with an A4 size. That is, the sheet P does not reach D5which is the detection point of the sheet sensor43even when transporting one of the sheets where the length of the sheet is an A4 size.

Accordingly, the control section30stops transferring of the driving force of the sheet supply motor34from the pickup roller11to the sheet P in the continuous transport mode before the last of the sheets P in a print job reaches D5which is the detection point of the sheet sensor43in order for the sheet P which is not used in the print job to not be drawn out downstream more than the origin Do when the print job is complete. In addition, the control section30continues transferring of the driving force of the sheet supply motor34from the pickup roller11to the sheet P in the continuous transport mode until the last of the sheets P reaches D1which is the contact point of the relay roller12aand the driven roller12bin order for the sheets P to be continuously transported from the first to the last of the sheets in the print job.

The switching mechanism19is configured so as to maintain either state of a state where the driving force of the sheet supply motor34is transferred to the pickup roller11or a state where the driving force of the sheet supply motor34is not transferred to the pickup roller11.

The switching mechanism19is shown inFIGS. 7A and 7B. The switching mechanism19is provided with gears191and193for continuing or interrupting a transfer path of the driving force from the sheet supply motor34to the pickup roller11and a holding section192which holds the rotation shafts of the gears191and193.

The gears191and193are fixed to a rotation shaft which is shared. The holding section192is supported to be parallel with the carriage21so as to be able to move. The holding section192is pressed by a spring which is not shown in the diagram in a direction toward an edge section which is on the opposite side to the home position (a direction to the left inFIGS. 7A and 7B) and is at a position which is shown inFIG. 7Ain the vicinity of the home position in a state of being of not being in contact with the carriage21. In the state which is shown inFIG. 7Awhere the holding section192is not in contact with the carriage21, the gear191meshes with a gear101which always transfers torque to the pickup roller11and the gear193meshes with a gear102which always transfers torque from the sheet supply motor34. Accordingly, the driving force of the sheet supply motor34is transferred to the pickup roller11in the state which is shown inFIG. 7Awhere the holding section192is not in contact with the carriage21.

A portion of the holding section192protrudes into the range of the movement of the carriage21toward a region of the edge section on the home position side. As a result, the carriage21abuts with the holding section192when moving to the prescribed position toward the home position. The holding section192engages with an engaging mechanism which is not shown in the diagram when moving to the prescribed position which is shown inFIG. 7Bby being pressed by the carriage21. The gear191is separated from the gear101which transfers torque to the pickup roller11in a state which is shown inFIG. 7Bwhere the holding section192is engaged with the engaging mechanism. Accordingly, the driving force of the sheet supply motor34is not transferred to the pickup roller11in the state inFIG. 7Bwhere the holding section192is engaged with the engaging mechanism.

The engaging mechanism which is not shown in the diagram releases the holding section192when the holding section192is further pressed to a direction to the left of the position, which is shown inFIG. 7B, on the paper of the diagram due to the carriage21. After this, the holding section192which is released by the engaging mechanism returns to the state which is shown inFIG. 7Aby being pressed by the spring when the carriage21moves in the direction toward the edge section which is on the opposite side to the home position (a direction to the left inFIGS. 7A and 7B).

In this manner, it is possible to reduce manufacturing costs of the printer1in the present embodiment compared to a case of providing a separate actuator, which switches between a state where the driving force is transferred from the sheet supply motor34to the pickup roller11and a state where the driving force is not transferred from the sheet supply motor34to the pickup roller11, in order to drive the switching mechanism19using the carriage motor32.

3. Printer Operations

Next, an overview of operations of the printer1in a one-sided printing continuous sheet supply mode (a continuous transport mode) will be described with reference toFIG. 3.

The control section30rotates the pickup roller11and the relay rollers12aand13aby activating the sheet supply motor34and transports the first of the sheets to the print section20(S1) when a print job, which is set in a one-sided printing continuous sheet supply mode (the continuous transport mode) for sheets with an A4 size, is acquired. At this time, the control section30activates the sheet supply motor34by setting a target value of the rotation angle, which is in a range where the sheet P sufficiently reaches the detection position of the sheet sensor43, in the driving circuit33.

After activating the sheet supply motor34, the control section30continues by determining if the front edge of the sheet P has reached the detection position of the sensor sheet43(S2) until the front edge of the sheet P reaches the detection position of the sensor sheet43.

When it is determined that the front edge of the sheet P has reached the detection position of the sensor sheet43, the control section30executes continuous sheet supply printing (S3). The continuous sheet supply printing is a process where the sheet P which is the next sheet is transported toward the print section20by the pickup roller11and the relay rollers12aand13abeing rotated at the same time as the sheet feeding roller14aand the sheet discharge roller15aare rotated in order to execute printing with regard to one of the sheets P.

Here, the length of the transport segment |D0/D5| from the sheet supply cassette50to the sheet sensor43of the print section20satisfies the following relationship when length of the sheet with an A4 size in the transport direction is Z1and the interval between the preceding and succeeding sheets P which are continuously transported in the one-sided printing continuous sheet supply mode is Y.
Y+Z4<|D0/D5|<2(Y+Z4)

Accordingly, the continuous sheet supply printing is performed with regard to the sheets P until the sheet P which is the n−2thsheet which belongs to one print job.

When printing with regard to an arbitrary one of the sheets P which belongs to the one print job is completed, the control section30determines if printing is complete with regard to the sheet P which is the n−2thsheet which belongs to the print job (S4). The control section30repeats the processes of steps S2, S3and S4until printing is completed with regard to the sheet P which is the n−2thsheet which belongs to the print job. Here, during sheet supply printing of the sheet Pnwhich is the nthsheet which belongs to one print job, Y which is the interval between the preceding and succeeding sheets P which are continuously transported in the continuous sheet supply mode and |D5/D7| which is the distance from D7which is the position of the discharge port on the farthest upstream side of the print head22to D5which is the detection position of the sheet sensor43are set to a relationship where the sheet Pn+1which is the next sheet does not reach the detection position of the sheet sensor43until the rear edge of the sheet Pnwhich is the nthsheet reaches D7which is the position of the discharge port on the farthest upstream side of the print head22.

When it is determined that printing is complete with regard to the sheet P which is the n−2thsheet which belongs to the print job, the control section30continues by determining if the front edge of the sheet P has reached the detection position of the sensor sheet43(S5) until the front edge of the sheet P which is the next sheet reaches the detection position of the sensor sheet43. Here, since printing is complete with regard to the sheet P which is the n−2thsheet, it is determined whether or not the front edge of the sheet P which is the n−1thsheet has reached the detection position of the sheet sensor43.

When it is determined that the front edge of the sheet P which is the n−1thsheet has reached the detection position of the sheet sensor43, sheet supply printing is performed with regard to the sheet P which is the n−1thsheet (S6). As will be described later, in the sheet supply printing with regard to the sheet P which is the n−1thsheet, the sheet P which is the nthsheet is transported toward the print section20by being drawn out from the sheet supply cassette50by rotating the pickup roller11and the relay rollers12aand13aat the same time as the sheet feeding roller14ais rotated during printing with regard to the sheet P which is the n−1thsheet. However, as will be described later, transferring of the driving force from the pickup roller11to the sheet supply motor34is stopped before the pickup roller11comes into contact with the sheet P (the sheet P which is the n+1thsheet) which does not belong to the print job which is being executed.

When the sheet supply printing of the n−1thsheet is complete, the control section30continues by determining if the front edge of the sheet P has reached the detection position of the sensor sheet43(S7) until the front edge of the sheet P reaches the detection position of the sensor sheet43. Here, it is determined whether or not the front edge of the sheet P which is the last sheet has reached the detection position of the sensor sheet43since the printing is completed up to printing with regard to the sheet P which is the n−1thsheet.

When it is determined that the front edge of the sheet P which is the last sheet has reached the detection position of the sheet sensor43, printing is performed with regard to the sheet P which is the last sheet (S8). Since the length of the transport segment |D0/D5| from the sheet supply cassette50to the sheet sensor43of the print section20is shorter than Z4which is length of the sheet with an A4 size and is shorter than 2×Z4, the pickup roller11comes into contact with the sheet P which is not a printing target in the print job which is currently being executed in a state where the front edge of the sheet P which is the last sheet has reached the detection position of the sheet sensor43. Then, the relay rollers12aand13a, the sheet feeding roller14a, and the sheet discharge roller15aare driven by the sheet supply motor34during printing with regard to the sheet P which is the last sheet, but the sheet P which is not a printing target in the print job which is currently being executed is not drawn out from the sheet supply cassette50since there is a continuation of a state, where transferring of the driving force of the sheet supply motor34to the pickup roller11is stopped, from during the sheet supply printing with regard to the sheet P which is the n−1thsheet.

Next, the operation of the sheet supply printing with regard to the sheet P which is the n−1thsheet will be described with reference toFIG. 4.

When starting execution of the sheet supply printing of the n−1thsheet, first, the control section30executes sheet transporting by driving the sheet supply motor34with the initial print position of the sheet P which is the n−1thsheet as a target (S31). At this time, as will be described later, the control section30stops transferring of the driving force from the sheet supply motor34to the pickup roller11according to the target position.

Next, the control section30executes main scanning where ink is discharged from the print head22once (S32) by driving the print head22while moving the carriage21in either direction by driving the carriage motor32. At this time, ink is discharged from the print head22in a segment of D7/D8which is shown inFIG. 1with regard to the sheet P which is the n−1thsheet which is stopped on the platen24.

Next, the control section30executes a pickup roller off control (S33). As will be described later, the control section30in the pickup roller off control stops transferring of the driving force from the sheet supply roller34to the pickup roller11according to the state of a pickup roller off flag and the immediately previous movement direction of the carriage21.

Next, the control section30executes sheet transporting by driving the sheet supply motor34with the next print position of the sheet P which is the n−1thsheet as a target (S34). At this time, as will be described later, the control section30stops transferring of the driving force from the sheet supply motor34to the pickup roller11according to the target position during transporting of the sheet P.

Next, the control section30determines whether or not the trailing edge of the range where printing is possible (the trailing edge of the page) on the sheet P which is the n−1thsheet has reached D7which is the position of the discharge port on the farthest upstream side of the print head22(S35). The control section30repeats the process of steps S32to S35until the trailing edge of the page reaches D7which is the position of the discharge port on the farthest upstream side of the print head22.

When it is determined that the rear edge of the sheet P which is the n−1thsheet reaches D7which is the position of the discharge port on the farthest upstream side of the print head22, the control section30activates the sheet supply motor34and transports the sheet P with a position, where the rear edge of the sheet P which is the n−1thsheet passes the contact point between the sheet discharge roller15aand the driven roller15b, as a target (S36). At this time, the relay rollers12aand13a, the sheet feeding roller14a, and the sheet discharge roller15aare driven when the sheet supply motor34is rotated. Then, since transferring of the driving force of the sheet supply motor34from the pickup roller11to the sheet P is stopped in both step S31and S32, the pickup roller11is not driven even if the sheet supply motor34is rotated. The sheet supply printing of the n−1thsheet is completed when the control section30activates the sheet supply motor34by setting a target value of the rotation angle, which is in a range where the rear edge of the sheet P which is the n−1thsheet sufficient reaches the contact point of the sheet discharge roller15aand the driven roller15b, in the driving circuit33.

When the sheet supply printing of the sheet P which is the n−1thsheet is completed by activating the sheet supply motor34and the sheet P which is the nth(last) sheet reaches the detection position of the sheet sensor43, the control section30starts printing of the sheet P which is the nthsheet since “true” is determined in step S7which is shown inFIG. 3.

Next, the operation of sheet transporting which is executed in steps S31and S34which are shown inFIG. 4will be described in detail with reference toFIG. 5.

Initially, the control section30acquires a current transport target (S310). At this time, the control section30acquires a transport target which is a value which indicates the rotation angle of the sheet supply motor34, but at this point in time, the transport target is not set in the driving circuit33of the sheet supply motor34. Here, the transport target is not only |D7/D8| which is the length of the print head22in the sub-scanning direction but is different every time according to the content of a printing target page due to the settings of the intervals between lines in the sub-scanning direction and the lengths of the margins.

Next, when it is assumed that the sheet P where printing is being carried out reaches the current transport target, that is, when it is assumed that the sheet supply motor34is rotated to the current transport target, the control section30determines whether or not the sheet P which is the next sheet has reached D1which is the contact point of the relay roller12aand the driven roller12b(S311). Here, that the sheet P which is the next sheet has reached D1which is the contact point of the relay roller12aand the driven roller12bis the same as that the relay rollers have started to send out the sheet P which is the nth(last) sheet. Accordingly, due to this determination, it is clear whether or not there is a state where it is possible to transport the sheet P which is the last sheet to the print section20without driving the pickup roller11due to the sheet P where printing is being carried out having reached the current transport target.

The control section30determines whether or not the rear edge of the sheet where printing is currently being carried out has reached D5which is the detection position of the sheet sensor43(S312) when the sheet supply motor34is rotated to the current transport target in a case where it is determined that the sheet P which is the last sheet has not reached D1which is the contact point of the relay roller12aand the driven roller12beven when the sheet supply motor34is rotated to the current transport target. Here, activating of continuous sheet supply printing until the n−2thsheet, sheet supply printing of the n−1thsheet, and printing of the nthsheet are at points in time when the front edge of the sheet P has reached the detection position of the sheet sensor43. Accordingly, when the sheet supply motor34is rotated to the current transport target, it may be determined whether or not the front edge of the sheet P which is the next sheet has reached the detection position of the sheet sensor43and not whether or not the rear edge of the sheet P where printing is currently being carried out has reached D5which is the detection position of the sheet sensor43.

The sheet transporting is completed by the control section30driving the sheet supply motor34to the current transport target (S313) in a case where it is determined that the rear edge of the sheet P where printing is currently being carried out has not reached D5which is the detection position of the sheet sensor43even when the sheet supply motor34is rotated to the current transport target. At this time, the relay rollers12aand13a, the sheet feeding roller14a, and the sheet discharge roller15aare driven when the sheet supply motor34is rotated. In addition, if transferring of the driving force from the sheet supply motor34to the pickup roller11has already been stopped, the pickup roller11is not driven even when the sheet supply motor34is rotated. In addition, if transferring of the driving force from the sheet supply motor34to the pickup roller11has not yet stopped, the pickup roller11is also driven when the sheet supply motor34is rotated.

The pickup roller11is rotated along with the sheet P which is the nthsheet since the sheet P which is the nthsheet is sent out by the relay roller12aif the sheet supply motor34is rotated in a case where the pickup roller11and the relay roller12acome into contact with the same sheet P which is the nthsheet even in a state where the driving force of the sheet supply motor34is not transferred to the pickup roller11. On the other hand, the sheet P which is the n+1thsheet is not drawn out from the sheet supply cassette50since the pickup roller11is not rotated in a case where rear edge of the sheet P which is the nthsheet which is sent out by the relay roller12ahas already passed the pickup roller11in a state where the driving force of the sheet supply motor34is not transferred to the pickup roller11.

Therefore, the control section30rotates the sheet supply motor34to the current transport target in step S313after the pickup roller off flag is turned on (S318) in a case where it is determined that the sheet P which is the last sheet has reached D1which is the contact point of the relay roller12aand the driven roller12bin step S311when the sheet supply motor34is rotated to the current transport target.

As will be described next, the control section30executes splitting the process of transporting into two part of prior transporting where the rear edge of the sheet P where printing is currently being carried out has not reached the sheet sensor43and latter transporting where the rear edge of the sheet P where printing is currently being carried out has passed the sheet sensor43as well as stopping transferring of the driving force from the sheet supply motor34to the pickup roller11between the prior transporting and the latter transporting in a case where it is determined that the rear edge of the sheet P where printing is currently being carried out has reached D5which is the detection position of the sheet sensor43when the sheet supply motor34is rotated to the current transport target.

In detail, first, the control section30drives the sheet supply motor34by setting the transport target in the prior transporting to immediately before the rear edge of the sheet P where printing is currently being carried out reaches D5which is the detection position of the sheet sensor43(S314). In the prior transporting, the pickup roller11, the relay rollers12aand13a, the sheet feeding roller14a, and the sheet discharge roller15aare driven by the sheet supply motor34since the driving force is transferred from the sheet supply motor34to the pickup roller11.

When the sheet supply motor34is stopped due to the rear edge of the sheet P where printing is currently being carried out reaching immediately before D5which is the detection position of the sheet sensor43, the control section30stops transferring of the driving force from the sheet supply motor34to the pickup roller11(S315) by moving the switching mechanism19along with the carriage21by driving the carriage motor32.

When transferring of the driving force from the sheet supply motor34to the pickup roller11is stopped, the control section30drives the sheet supply motor34(S316) by setting the current transport target with regard to the sheet P which is the n−1thsheet as the transport target in the latter printing. In the latter transporting, the sheet which is the n+1thsheet, where printing is not carried out in the print job which is currently being executed, is not drawn out by the pickup roller11since the driving force from the sheet supply motor34to the pickup roller11is not transferred. Then, in the latter transporting, since the sheet P which is the nth(last) sheet has already been transferred to D1which is the contact point of the relay roller12aand the driven roller12b, the sheet P which is the nthsheet is reliably transported to the print section20by the relay rollers12aand13aeven without the driving force being transferred from the sheet supply motor34to the pickup roller11.

Next, pickup roller off control which is executed in step S33which is shown inFIG. 4will be described in detail with reference toFIG. 6.

Initially, the control section30determines if the pickup roller off flag is on or off (S321). In a case where it is determined that the pickup roller off flag is off, the control section30completes pickup roller off control without stopping transferring of the driving force from the sheet supply motor34to the pickup roller11.

In a case where the pickup roller off flag is on, the control section30determines whether or not the movement direction of the carriage21during the previous printing is a direction of approaching the home position (a direction of approaching the switching mechanism19) (S322). That is, it is determined in which direction the carriage21is moving when ink is being discharged in step S32which is shown inFIG. 4which is carried out immediately beforehand. In a case where it is determined that the movement direction of the carriage21during the previous printing is not a direction of approaching the home position, the control section30completes pickup roller off control without stopping transferring of the driving force from the sheet supply motor34to the pickup roller11.

In a case where it is determined that the movement direction of the carriage21during the previous printing is a direction of approaching the home position (a direction of approaching the switching mechanism19), the control section30stops transferring of the driving force from the sheet supply motor34to the pickup roller11(S323) by moving the carriage motor32to abut with the switching mechanism19in the same direction as during the previous printing by driving the carriage motor32and further moving the switching mechanism19along with the carriage21. That is, in pickup roller off control, the transfer path of the driving force from the sheet supply motor34to the pickup roller11is interrupted and, as a result, transferring of the driving force from the sheet supply motor34to the sheet P which is the nthsheet is stopped only in a case where the movement direction of the carriage21during the previous printing is a direction of approaching the switching mechanism19. Then, the carriage motor32is not driven and the carriage21does not move to the switching mechanism19in a case where the movement direction of the carriage21during the previous printing is a direction of moving away from the switching mechanism19. As a result, it is possible to shorten time for printing by suppressing the movement distance of the carriage21which is performed in order to stop transferring of the driving force from the sheet supply motor34to the sheet P which is the nthsheet.

Using the printer1described above, in a case where the printing media are transported in the continuous transport mode in the print job with n sheets, the sheet P which is the n+1thsheet which is not used in the print job is not drawn out by the pickup roller11irrespective of the length of the printing media and the transport distance since transferring of the driving force from the sheet supply motor34to the pickup roller11is stopped before the pickup roller11completes drawing out of the sheet P which is the last sheet which belongs to the print job from the sheet supply cassette50. In addition, it is possible to continuously transport all of the sheets P which are used in the print job to the print section20since transferring of the driving force from the sheet supply motor34to the pickup roller11is stopped after the relay roller12astarts drawing out of the sheet P which is the last sheet.

In addition, it is not possible for the control section30to stop the pickup roller since the control section30does not carry out switching of the switching mechanism19using movement of the carriage21in a case where it is determined that the movement direction of the carriage21during the previous printing is not a direction of approaching the home position even when the pickup roller off flag is on. In this state, it is possible for the control section30to stop the pickup roller by carrying out switching of the switching mechanism19using movement of the carriage21if the next printing has been executed and the movement direction of the carriage21during the previous printing is a direction of approaching the home position. However, the control section30still does not carry out switching of the switching mechanism19using movement of the carriage21in a case where only transporting of the sheet P is carried out without the next printing being executed. In a case such as this, the sheet P which is the n+1thsheet which is not used in the print job is not drawn out by the pickup roller11if switching of the switching mechanism19is carried out according to it being determined that the rear edge of the sheet P where printing is currently being carried out reaches D5which is the detection position of the sheet sensor43when the sheet supply motor34is rotated to the current transport target.

4. Other Embodiments

Here, the technical scope of the present invention is not limited by the embodiment described above and it is clear that various modifications are possible in the scope which does not depart from the gist of the present invention.

In the embodiment described above, transferring of the driving force from the sheet supply motor34to the pickup roller11is stopped during execution of sheet supply printing with regard to the sheet P which is the second to last sheet of the print job (the n−1thsheet in the print job with n sheets), but whether to stop transferring of the driving force from the sheet supply motor34to the pickup roller11during execution of sheet supply printing with regard to the sheet P which is any number sheet before the last sheet of the print job may be set according to the length of the transport path. That is, when the transport distance of the sheet P from the pickup roller11to the print section20is X, the interval between the sheets P which line up and are transported as preceding and succeeding sheets in the continuous transport mode is Y, the length of the sheet P is Z, and N is a quotient X/(Y+Z), the control section30may stop transferring of the driving force from the sheet supply motor34to the pickup roller11before the rear edge of the sheet P which is the (n−N)thsheet reaches the print section20. Then, the number of relay rollers is not limited to two, may be one or three or more, and may be set to a number according to the length of the transport path.

In addition, transferring of the driving force from the sheet supply motor34to the pickup roller11may be stopped at any timing during a period when the pickup roller11draws out the sheet P which is the last sheet of the print job if it is after the relay roller12ahas started to send out the sheet P which is the last sheet. In addition, transferring of the driving force from the sheet supply motor34to the pickup roller11may be stopped normally in step S315by, for example, reversing the processing order of step S311and step S312which are shown inFIG. 5or omitting the processes of steps S33, S311, and S318.

In addition, instead of stopping transferring of the driving force from the sheet supply motor34to the pickup roller11, transferring of the driving force of the sheet supply motor34from the pickup roller11to the sheet P may be stopped by separating the pickup roller11from the sheet P by moving the pickup roller11. In addition, the switching mechanism may be driven by an actuator which is different from the carriage motor32.

In addition, a printing mechanism such as a line ink jet printer, a laser printer, a heat transfer printer, or the like may be used as the print section. In addition, the edge of the sheet may be detected using a non-contact sensor other than an optical sensor, the edge of the sheet may be detected using a contact sensor, or displacement of the sheet may be measured using only the rotary encoder of the sheet supply motor. In addition, as the actuator which drives the transport roller, a stepping motor may be used or a servomotor may be used.

General Interpretation of Terms