Patent Description:
In a printer, a sheet-feed type scanner, or the like, a roller pair configured by a drive roller and a driven roller is provided in a medium transport path. Sometimes, the driven roller may be configured to advance and retreat with respect to the drive roller, as shown in the <CIT>.

<CIT> discloses a configuration in which a head movement unit having a line head, which is a recording head, a maintenance unit having a cap section that caps the line head, and a second maintenance unit having a blade that wipes the line head are movable in directions orthogonal to each other.

In a case where a clutch is provided in a driving force transmission path from a motor to a drive roller and on/off switching of driving force transmission from the motor to the drive roller is performed, when the clutch is turned on after the motor is started, backlash of gears disappears and meshing noise occurs when teeth of the gears mesh with each other.

<CIT> discloses a target transportation device that includes a first transportation portion which is capable of applying a transportation force toward a downstream side from an upstream side of a transportation path to a target, a second transportation portion which is provided on the transportation path at a position at the downstream side with respect to the first transportation portion in a transportation direction and is capable of applying a transportation force toward the downstream side from the upstream side of the transportation path to the target while nipping the target, and a cutting member which is provided on the transportation path at a position between the first transportation portion and the second transportation portion and is capable of cutting the target in the width direction perpendicular to the transportation direction of the target. The second transportation portion is configured so as to be capable of changing a nipping position of the target in the transportation direction of the target.

A medium transport apparatus according to the invention is defined in claim <NUM>.

Another medium transport apparatus according to the invention is defined in claim <NUM>.

Further, a recording apparatus according to the invention includes the medium transport apparatus described above and a recording section configured to perform recording on a medium being transported.

A control method according to the invention is defined in claim <NUM>.

Another control method according to the invention is defined in claim <NUM>.

Hereinafter, the present disclosure will be specifically described.

Hereinafter, an inkjet printer <NUM> that performs recording by ejecting ink, which is an example of a liquid, onto a medium, represented by recording paper, will be described as an example of a recording apparatus. Hereinafter, the inkjet printer <NUM> will be abbreviated as printer <NUM>. Since the printer <NUM> transports the medium, the printer <NUM> is also an example of a medium transport apparatus.

An X-Y-Z coordinate system illustrated in the drawings is an orthogonal coordinate system, and a Y-axis direction is a direction intersecting with a transport direction of the medium, that is, a medium width direction, and is also an apparatus depth direction. In the Y-axis direction, a +Y direction is a direction from an apparatus front surface toward an apparatus rear surface, and a -Y direction is a direction from the apparatus rear surface toward the apparatus front surface.

An X-axis direction is an apparatus width direction, and a +X direction is to the left side and a -X direction is to the right side as viewed from an operator of the printer <NUM>. A Z-axis direction is a vertical direction, which is a normal direction with respect to a placement surface G of the printer <NUM>, that is, an apparatus height direction. In the Z-axis directions, a +Z direction is the upward direction and a -Z direction is the downward direction.

Hereinafter, a direction in which the medium is transported may be referred to as "downstream", and an opposite direction may be referred to as "upstream". In <FIG>, a medium transport path is indicated by a dashed line. In the printer <NUM>, the medium is transported through the medium transport path indicated by the dashed line in <FIG>.

An F-axis direction is a medium transport direction between a line head <NUM> and a transport belt <NUM> (these will be described later), that is, in a recording region, and a +F direction is downstream in the transport direction and an opposite -F direction is upstream in the transport direction. A V-axis direction is orthogonal to the F-axis direction.

Hereinafter, the medium transport path in the printer <NUM> will be described with reference to <FIG>. The printer <NUM> is configured such that an additional unit <NUM> can be coupled to a lower portion of an apparatus main body <NUM>, and <FIG> illustrates a state in which the additional unit <NUM> is coupled.

The apparatus main body <NUM> is provided with a first medium cassette <NUM> for accommodating the medium in the lower portion thereof, and when the additional unit <NUM> is coupled, a second medium cassette <NUM> and a third medium cassette <NUM> are further provided below the first medium cassette <NUM>. The medium cassettes are examples of a medium support section that supports the medium before feeding.

The medium cassettes are provided with a pickup roller that feeds the accommodated medium in the -X direction. Pickup rollers <NUM>, <NUM>, and <NUM> are pickup rollers provided for the first medium cassette <NUM>, the second medium cassette <NUM>, and the third medium cassette <NUM>, respectively, and are provided so as to be able to advance and retreat with respect to the medium accommodated in the medium cassettes.

The medium cassettes are provided with a feed roller pair for feeding the medium fed in the -X direction obliquely upward. Feed roller pairs <NUM>, <NUM>, and <NUM> are feed rollers provided for the first medium cassette <NUM>, the second medium cassette <NUM>, and the third medium cassette <NUM>, respectively.

In the following description, unless otherwise specified, a "roller pair" is composed of a drive roller that is driven by a drive source to apply feed force to the medium, and a driven roller that is driven to rotate in contact with the drive roller or the medium.

The medium fed out from the third medium cassette <NUM> is sent to the transport roller pair <NUM> by transport roller pairs <NUM> and <NUM>. The medium fed out from the second medium cassette <NUM> is sent to the transport roller pair <NUM> by the transport roller pair <NUM>. The medium is nipped by the transport roller pair <NUM> and sent to the transport roller pair <NUM>.

The medium fed out from the first medium cassette <NUM> is sent to the transport roller pair <NUM> by the feed roller pair <NUM> without passing through the transport roller pair <NUM>.

Note that a feed roller <NUM> and a separation roller <NUM> provided in the vicinity of the transport roller pair <NUM> are roller pair that feeds the medium from a supply tray (not illustrated in <FIG>).

The medium that receives feed force from the transport roller pair <NUM> is sent to a position between the line head <NUM>, which is an example of a recording head, and the transport belt <NUM>, that is, to a position facing the line head <NUM>. Hereinafter, the medium transport path from the transport roller pair <NUM> to a transport roller pair <NUM> is referred to as a recording time transport path T1.

The line head <NUM> constitutes a head unit <NUM>. The line head <NUM> performs recording by ejecting ink onto a surface of the medium. The line head <NUM> is an ink ejection head configured such that nozzles for ejecting ink cover the entire region in the medium width direction, and is configured as the ink ejection head capable of performing recording on the entire region in the medium width direction without moving in the medium width direction. However, the ink ejection head is not limited thereto, and may be a type that is mounted on a carriage and that ejects ink while moving in the medium width direction.

The head unit <NUM> is provided so as to be able to advance and retreat with respect to the recording time transport path T1, and is provided so as to be able to move between a recording position at which the head unit <NUM> advances to the recording time transport path T1 and performs recording on the medium, and a retreat position at which the head unit <NUM> retreats from the recording time transport path T1.

<FIG> shows a state in which the head unit <NUM> is in the recording position, and in this state, recording is performed on the medium.

Reference symbols 10A, 10B, 10C, and 10D denote ink containers as liquid containing sections. The ink to be eject from the line head <NUM> is supplied to the line head <NUM> from the ink containers via a tube (not shown). The ink containers 10A, 10B, 10C, and 10D are detachably provided with respect to the mounting sections 11A, 11B, 11C, and 11D, respectively.

Reference symbol <NUM> denotes a waste liquid container that stores ink as waste liquid ejected from the line head <NUM> toward a flushing cap (not shown) for maintenance.

The transport belt <NUM> is an endless belt which is wound around a pulley <NUM> and a pulley <NUM>, and rotates when at least one of the pulley <NUM> and the pulley <NUM> is driven by a motor (not shown). The medium is transported to the position facing the line head <NUM> while clinging to the belt surface of the transport belt <NUM>. A known attraction method such as an air suction method or an electrostatic attraction method can be adopted for attracting the medium to the transport belt <NUM>.

Here, the recording time transport path T1 that passes through the position facing the line head <NUM> intersects both a horizontal direction and the vertical direction, and transports the medium upward. Accordingly, the V-axis direction, which is the movement direction of the head unit <NUM>, also intersects both the horizontal direction and the vertical direction, and the inclination angle α of the V-axis direction with respect to the horizontal direction is smaller than <NUM>°, more specifically, approximately <NUM>°.

The V-axis direction may be parallel to the horizontal direction without being limited to the above-described configuration.

The medium on which recording has been performed on a first surface by the line head <NUM> is further transported upward by the transport roller pair <NUM> positioned downstream of the transport belt <NUM>.

A flap <NUM> is provided downstream of the transport roller pair <NUM>, and the transport direction of the medium is switched by the flap <NUM>. When the medium is to be discharged as is, the medium transport path is switched by the flap <NUM> so as to be directed toward an upper transport roller pair <NUM>, and the medium is discharged toward a discharge tray <NUM> by the transport roller pair <NUM>.

When recording is performed on a second surface of the medium in addition to the first surface, the transport direction of the medium is directed to the branch position K1 by the flap <NUM>. Then, the medium passes through the branch position K1 and enters the switch-back path T2. In the present embodiment, the switch-back path T2 is the medium transport path above the branch position K1. Transport roller pairs <NUM> and <NUM> are provided in the switch-back path T2. The medium that has entered the switch-back path T2 is transported upward by the transport roller pairs <NUM> and <NUM>, and when the lower edge of the medium has passed through the branch position K1, the rotation direction of the transport roller pairs <NUM> and <NUM> is switched, whereby the medium is transported downward.

An inversion path T3 is connected to the switch-back path T2. In the present embodiment, the inversion path T3 is a medium transport path extending from the branch position K1 to the transport roller pair <NUM> through transport roller pairs <NUM> and <NUM>.

The medium transported downward from the branch position K1 receives feed forces from the transport roller pairs <NUM> and <NUM>, reaches the transport roller pair <NUM>, turns over while curving around, and is sent to the transport roller pair <NUM>.

The medium that is transported to the position facing the line head <NUM> again has its second surface, which is opposite to the first surface on which recording has already been performed, facing the line head <NUM>. Accordingly, recording by the line head <NUM> can be performed on the second surface of the medium.

Next, the power transmission apparatus 50A will be described with reference to <FIG>. The power transmission apparatus 50A includes a transport motor <NUM>, as an example of a drive source, and a drive roller 31a, as an example of a driven section, that is driven by the transport motor <NUM>. The power transmission apparatus 50A includes an electromagnetic clutch <NUM> as an example of a power transmission switching section that is switchable between a transmission state in which the power of the transport motor <NUM> is transmitted to the drive roller 31a and a non-transmission state in which the power of the transport motor <NUM> is not transmitted to the drive roller 31a. The electromagnetic clutch <NUM> is brought into the non-transmission state by being turned off, and into the transmission state by being turned on. In addition, the power transmission apparatus 50A includes a solenoid <NUM> as an example of a load switching section switchable between a first load state which is a load when the drive roller 31a is driven and a second load state which is a load is smaller than the first load state.

The power transmission apparatus 50A includes a control section <NUM> for controlling the transport motor <NUM>, the electromagnetic clutch <NUM>, and the solenoid <NUM>.

The control section <NUM> includes a non-volatile memory (not illustrated), and the non-volatile memory stores a program for realizing control described below, parameters necessary for executing the program, and the like.

The drive roller 31a is a roller that constitutes the transport roller pair <NUM> (see <FIG>). The transport roller pair <NUM> includes the drive roller 31a and a driven roller 31b that can advance and retreat with respect to the drive roller 31a. However, the drive roller 31a may be configured to advance and retreat with respect to the driven roller 31b. The transport roller pair <NUM> transports the medium by rotating the drive roller 31a in a state in which the medium is nipped between the drive roller 31a and the driven roller 31b. In <FIG>, the driven roller 31b shown by a solid line shows a state in which the driven roller 31b is advanced with respect to the drive roller 31a, and a reference symbol 31b-<NUM> shows a state in which the driven roller 31b is separated from the drive roller 31a.

The advance and retreat operation of the driven roller 31b with respect to the drive roller 31a is performed by the solenoid <NUM>. When the solenoid <NUM> is in the turned on (energized) state, the driven roller 31b advances to and contacts on the drive roller 31a, and when the solenoid <NUM> is in the turned off (non-energized) state, the driven roller 31b retreats from the drive roller 31a.

The load when the drive roller 31a is driven in a state where the driven roller 31b is in contact with the drive roller 31a is the first load state. When the driven roller 31b retreats from the drive roller 31a, a second load state in which the load is smaller than that in the first load state is established.

Note that the load switching section may have other configurations as long as it can switch between the first load state and the second load state. For example, it may be configured by a rack and pinion mechanism or the like operated by a motor.

The driving force of the transport motor <NUM> is transmitted to the pinion gear <NUM>, the gear <NUM>, the gear <NUM>, and the gear <NUM> in this order. The driving force of the transport motor <NUM> transmitted to the gear <NUM> is transmitted to the shaft <NUM> via the electromagnetic clutch <NUM>. Both the gear <NUM> and the drive roller 31a are provided on the shaft <NUM>, but the positions thereof are shifted in <FIG> for convenience of illustration.

Under the control of the control section <NUM>, the electromagnetic clutch <NUM> is switched between a transmission state (clutch on) in which the driving force of the transport motor <NUM> is transmitted to the drive roller 31a by transmitting the rotation of the gear <NUM> to the shaft <NUM> and a non-transmission state (clutch off) in which the driving force of the transport motor <NUM> is not transmitted to the drive roller 31a.

The power transmission switching section may have other configurations as long as it can switch between a transmission state in which the power of the transport motor <NUM> is transmitted to the drive roller 31a and a non-transmission state in which the power of the transport motor <NUM> is not transmitted to the drive roller 31a. For example, one of the two gears that can mesh with each other may be displaceable, and a meshing state and a non-meshing state may be switched between using power of a motor, a solenoid, or the like.

Next, a first embodiment of control performed by the control section <NUM> will be described with reference to <FIG> and <FIG>. The first embodiment of the control method of the power transmission apparatus 50A and the control method of the printer <NUM>, as the medium transport apparatus or the recording apparatus, is realized by the control shown in <FIG> and <FIG>.

In the printing standby state, the electromagnetic clutch <NUM> is off, the solenoid <NUM> is off, and the driven roller 31b is retreated from the drive roller 31a. Further, the transport motor <NUM> is not operating, that is, is stopped.

In a case where a plurality of media are to be transported from this state, and in a case where transport of a first medium (first page) of media is to be started, the control section <NUM> starts the transport motor <NUM> (step S101) and turns on the electromagnetic clutch <NUM> (step S102). This timing corresponds to the timing T1 in <FIG>. The start of the transport motor <NUM> and turning on of the electromagnetic clutch <NUM> may be performed at the same time, or one of them may be performed first.

After a waiting time wt (msec) (step S103) has elapsed, the solenoid <NUM> is turned on to bring the driven roller 31b into contact with the drive roller 31a (step S104, timing T2). That is, after the electromagnetic clutch <NUM> is turned on and waiting for a predetermined time, the solenoid <NUM> is turned on.

The waiting time wt (msec) is a time required to take up the slack of the backlash between the gears in the power transmission apparatus 50A, so that the teeth contact each other, and is desirably set as short as possible within this range.

Next, when the control section <NUM> determines that the leading edge of the medium is transported to a predetermined position (Yes in step S105), the control section <NUM> turns off the electromagnetic clutch <NUM> (step S106, timing T3). The predetermined position of the step S105 can be set to, for example, a position where the medium clings to the transport belt <NUM> or a nip position of the transport roller pair <NUM>. Medium detection sensors (not shown) are provided at a position facing the transport belt <NUM> and upstream and downstream of the line head <NUM>, and the control section <NUM> can grasp the position of the leading edge of the medium based on the detection information of the medium detection sensor.

Then, the control section <NUM> repeats steps S104 to S107 (No in step S107) until a last page is reached. When the last page is reached (Yes in step S107), the control section <NUM> stops the transport motor <NUM> (step S108), and turns off the solenoid <NUM> to retreat the driven roller 31b from the drive roller 31a (step S109). This timing corresponds to the timing Te in <FIG>. Stopping of the transport motor <NUM>, the turning off of the solenoid <NUM>, and the turning off of the electromagnetic clutch <NUM> may be performed at the same time, or any of them may be performed first.

As described above, the control section <NUM> switches the electromagnetic clutch <NUM> from the non-transmission state(clutch off) to the transmission state (clutch on) while the load for driving the drive roller 31a is in the second load state, that is, when the driven roller 31b is separated from the drive roller 31a, and then switches the load by the solenoid <NUM> to the first load state, that is, to the state in which the driven roller 31b is in contact with the drive roller 31a, so it is possible to suppress meshing noise in which teeth of two gears mesh with each other when the electromagnetic clutch <NUM> is switched from the non-transmission state (clutch off) to the transmission state (clutch on).

Further, in the present embodiment, there is provided the driven roller 31b, as a driven section, which is driven to rotate by contact with the drive roller 31a, as a drive section, and the driven roller 31b can be displaced by the solenoid <NUM>, as an example of a displacement mechanism, into a first position (position contacted to the drive roller 31a) for forming the first load state and a second position (position separated from the drive roller 31a) for forming the second load state. When the driven roller 31b is at the second position, the control section <NUM> switches the electromagnetic clutch <NUM> from the non-transmission state (clutch off) to the transmission state (clutch on). Accordingly, it is possible to suppress the meshing noise generated when the teeth of the two gears mesh with each other when the electromagnetic clutch <NUM> is switched from the non-transmission state (clutch off) to the transmission state (clutch on).

Further, as described above, when the load is in the second load state, the control section <NUM> switches the electromagnetic clutch <NUM> from the non-transmission state (clutch off) to the transmission state (clutch on) (step S102), and then switches the load from the second load state to the first load state by the solenoid <NUM> (step S104) to transport the first medium among the plurality of media (first page). When the first medium is transported by a predetermined amount (Yes in step S105), the electromagnetic clutch <NUM> is switched from the transmission state (clutch on) to the non-transmission state (clutch off) (step S106), and for the second and subsequent media (second and subsequent pages) among the plurality of media, while the load is maintained in the first load state, the electromagnetic clutch <NUM> is switched from the non-transmission state (clutch off) to the transmission state (clutch on) and from the transmission state (clutch on) to the non-transmission state (clutch off) each time the medium is transported (steps S104 to S107).

In this way, since the load is maintained in the first load state while a second and subsequent media among the plurality of media are transported until the transport of all the media ends, it is possible to improve quietness by suppressing the generation of sound generated by the solenoid <NUM>.

When the second and subsequent media are transported, since the state in which the backlash between the gears is taken up is maintained, meshing noise when backlash between gears is taken up is not generated.

Next, a second embodiment of control performed by the control section <NUM> will be described with reference to <FIG> and <FIG>. The second embodiment of a control method of the power transmission apparatus 50A and the control method of the printer <NUM>, as the medium transport apparatus or the recording apparatus, is realized by the control shown in <FIG> and <FIG>.

Since steps S201 to S205 in <FIG> are the same as steps S101 to S105 in <FIG>, description thereof is omitted.

When the leading edge of the medium is transported to the predetermined position (Yes in step S205), the control section <NUM> turns off the electromagnetic clutch <NUM> (step S206). Then, the solenoid <NUM> is turned off to retreat the driven roller 31b from the drive roller 31a (step S207). Step S206 and step S207 may be performed at the same time, or one of them may be performed first.

In the present embodiment, the control section <NUM> repeats steps S202 to S208 (No in step S208) until the last page is reached. When the last page is reached (Yes in step S208), the control section <NUM> stops the transport motor <NUM> (step S209, timing Te).

In <FIG>, timings T5 and Tn are timings at which the same processing as timing T1 is performed, and timings T6 and Tn+<NUM> are timings at which the same processing as timing T2 is performed (wherein n is an integer).

Also in this embodiment, at the timing Te, stopping of the transport motor <NUM>, turning off of the solenoid <NUM>, and turning off of the electromagnetic clutch <NUM> may be performed at the same time, or any of them may be performed first.

Also in the present embodiment, the control section <NUM> switches the electromagnetic clutch <NUM> from the non-transmission state (clutch off) to the transmission state (clutch on) while the load for driving the drive roller 31a is in the second load state, that is, when the driven roller 31b is separated from the drive roller 31a, and thereafter, switches the load by the solenoid <NUM> to the first load state, that is, the state in which the driven roller 31b is in contact with the drive roller 31a, so it is possible to suppress the meshing noise by teeth of two gears meshing with each other when the electromagnetic clutch <NUM> is switched from the non-transmission state (clutch off) to the transmission state (clutch on).

In addition, each time one medium is transported as described above, the control section <NUM> switches the electromagnetic clutch <NUM> from the non-transmission state (clutch off) to the transmission state (clutch on), and thereafter, executes a first control (step S202, S203, and S204) for switching the load from the second load state to the first load state by the solenoid <NUM>, a second control (step S206) for switching the electromagnetic clutch <NUM> from the transmission state (clutch on) to the non-transmission state (clutch off) when the medium is transported by a predetermined amount, and a third control (step S207) for switching the load from the first load state to the second load state by the solenoid <NUM>. Accordingly, it is possible to suppress wear of a members configuring the power transmission path from the transport motor <NUM> to the drive roller 31a.

Next, a third embodiment of control performed by the control section <NUM> will be described with reference to <FIG> and <FIG>. The third embodiment of a control method of the power transmission apparatus 50A and the control method of the printer <NUM>, as the medium transport apparatus or the recording apparatus, is realized by the control illustrated in <FIG> and <FIG>.

Since steps S301 to S305 in <FIG> are the same as steps S101 to S105 in <FIG>, description thereof is omitted.

When the leading edge of the medium is transported to the predetermined position (Yes in step S305), the control section <NUM> turns off the solenoid <NUM> to retreat the driven roller 31b from the drive roller 31a (step S306).

In the present embodiment, the control section <NUM> repeats steps S304 to S307 (No in step S307) until the last page is reached. When the last page is reached (Yes in step S307), the control section <NUM> turns off the electromagnetic clutch <NUM> (step S308) and stops the transport motor <NUM> (step S309, timing Te).

In the present embodiment, for a second and subsequent medium among the plurality media, as described above the control section <NUM> maintains the electromagnetic clutch <NUM> in the transmission state (clutch on) while using the solenoid <NUM> to switch from the second load state to the first load state (step S304) and switching from the first load state to the second load state (step S306) each time a medium is transported.

As a result, it is possible to improve quietness by suppressing the generation of noise generated by the electromagnetic clutch <NUM>.

Further, since the meshing noise generated when backlash between the gears is not generated in the second and subsequent media, the quietness can be enhanced by this as well.

Next, another embodiment of a power transmission apparatus will be described with reference to <FIG>. In <FIG>, the same components as those described with reference to <FIG> are denoted by the same reference symbols, and a description thereof will not be repeated.

In the power transmission apparatus 50B according to the present embodiment, the pickup roller <NUM> is an example of the driven section and a drive roller that are driven by the transport motor <NUM>. The pickup roller <NUM> is supported by a roller support member <NUM> that is swingable around a shaft <NUM>, and advances and retreats with respect to a medium P in accordance with the swing of the roller support member <NUM>. In <FIG>, the pickup roller <NUM> indicated by a solid line indicates a state in which the pickup roller <NUM> has advanced to and contacts the uppermost medium P, and a reference symbol <NUM>-<NUM> indicates the pickup roller <NUM> retreated from the medium P.

The power of the transport motor <NUM> is transmitted to the gear <NUM> via the pinion gear <NUM>, the gear <NUM>, and the gear <NUM>, and is transmitted to a shaft <NUM> via the electromagnetic clutch <NUM>. Both the gear <NUM> and a gear <NUM> are provided on the shaft <NUM>, but the positions thereof are shifted in <FIG> for convenience of illustration.

The gear <NUM> meshes with a gear <NUM>, and the gear <NUM> transmits power to a gear <NUM> via the shaft <NUM>. Both the gear <NUM> and the gear <NUM> are provided on the shaft <NUM>, the positions thereof are shifted in <FIG> for convenience of illustration.

The power transmitted to the gear <NUM> is transmitted to the pickup roller <NUM> via a gear <NUM> and a gear <NUM>.

Under the control of the control section <NUM>, the electromagnetic clutch <NUM> is switched between a transmission state (clutch on), in which the power of the transport motor <NUM> is transmitted to the pickup roller <NUM> by transmitting the rotation of the gear <NUM> to the shaft <NUM>, and a non-transmission state (clutch off), in which the power of the transport motor <NUM> is not transmitted to the pickup roller <NUM>.

The swinging operation of the roller support member <NUM> is performed by the solenoid <NUM>. When the solenoid <NUM> is in the on (energized) state, the pickup roller <NUM> is in contact with the uppermost medium P due to its own weight. When the solenoid <NUM> is in the off (non-energized) state, the roller support member <NUM> is pulled upward and retreated from the uppermost medium P. In addition, the relationship between on and off of the solenoid <NUM> may be reversed, that is, the pickup roller <NUM> may be pulled upward and retreated from the uppermost medium P in the state in which the solenoid <NUM> is off (non-energized), and the pickup roller <NUM> may in contact with the uppermost medium P in the state in which the solenoid <NUM> is on (energized).

In the state in which the pickup roller <NUM> is in contact with the uppermost medium P, the load when the pickup roller <NUM> is driven is the first load state. When the pickup roller <NUM> retreats from the uppermost medium P, the second load state is entered, in which the load is smaller than the load in the first load state. In this way, the contact state of the pickup roller <NUM> with respect to the medium P affects the load when driving the pickup roller <NUM>.

Also in the present embodiment, the control according to the first embodiment described with reference to <FIG> and <FIG>, the control according to the second embodiment described with reference to <FIG> and <FIG>, or the control according to the third embodiment described with reference to <FIG> and <FIG> can be employed.

That is, in this embodiment, the pickup roller <NUM>, which is an example of the driven section, is displaced by the solenoid <NUM>, which is an example of the displacement mechanism, between the first position, which is the position forming the first load state and in which the roller <NUM> is in contact with the uppermost medium P, and the second position, which is the position forming the second load state and in which the roller <NUM> is retreated from the uppermost medium P. When the pickup roller <NUM> is at the second position, the control section <NUM> switches the electromagnetic clutch <NUM> from the non-transmission state (clutch off) to the transmission state (clutch on). Accordingly, it is possible to suppress the meshing noise generated when the teeth of the two gears mesh with each other when the electromagnetic clutch <NUM> is switched from the non-transmission state (clutch off) to the transmission state (clutch on).

Note that when the first medium is to be transported in the first embodiment, the second embodiment, or the third embodiment described above, after the control section <NUM> switches the electromagnetic clutch <NUM> from the non-transmission state (clutch off) to the transmission state (clutch on) while the load for driving the driven section is in the second load state, and after the speed of the transport motor <NUM> is set to a first speed and the solenoid <NUM> switches the load from the second load state to the first load state, then the speed of the transport motor <NUM> may be set to a second speed higher than the first speed, and the medium may be transported at the second speed. Accordingly, it is possible to further suppress the meshing noise generated when the teeth of the two gears mesh with each other when the electromagnetic clutch <NUM> is switched from the non-transmission state (clutch off) to the transmission state (clutch on).

Claim 1:
A medium transport apparatus (<NUM>) comprising:
a power transmission apparatus (50A); and
a medium transport path (T1-T3) configured to transport a medium, the power transmission apparatus comprising:
a drive source (<NUM>);
a power transmission switching section (<NUM>) configured to switch between a transmission state in which power of the drive source is transmitted to a driven section (31a) and a non-transmission state in which power of the drive source is not transmitted to the driven section;
a load switching section (<NUM>) configured to switch between a first load state, which is a load while the driven section is driven, and a second load state, which is a load smaller than the load of the first load state; and
a control section (<NUM>) configured to control the drive source, the power transmission switching section, and the load switching section, wherein
the driven section (31a) is a drive roller configured to apply feeding force to the medium in the medium transport path,
the medium transport apparatus further comprising a driven roller (31b), characterized in that the driven roller is configured to advance and retreat with respect to the drive roller,
the load switching section (<NUM>) forms the first load state by bringing the driven roller into contact with the drive roller, and forms the second load state by separating the driven roller from the drive roller, and
the control section switches the power transmission switching section from the non-transmission state to the transmission state while the load is in the second load state, and then uses the load switching section to switch the load from the second load state to the first load state.