A medium transport device includes a feeding roller that feeds a recording medium, a transport roller that transports the recording medium toward a recording head, and a transport motor which is a common driving source for the feeding roller and the transport roller. The medium transport device includes a power transmission mechanism that transmits power of the transport motor to the feeding roller, and a control section that controls a current of the transport motor. The control section measures a current value flowing through the transport motor during driving as a measured current value, and adds a predetermined offset value to the measured current value to set a second limit value as a limit value of the current supplied to the transport motor.

A printer includes: a conveyor that performs a forward-conveyance operation for conveying a printing medium downstream in a conveying direction and a backward-conveyance operation for conveying the printing medium upstream in the conveying direction; a printing device; a roller provided downstream of the conveyor in the conveying direction; an opposed member opposed to the roller; a moving mechanism that moves a moving member, which is one of the roller and the opposed member, between (i) a first position at which the printing medium is nipped between the moving member and the other of the roller and the opposed member and (ii) a second position at which the moving member is separated from the printing medium; and a controller that executes a first conveyor-backward-conveyance processing for controlling the conveyor to perform the backward-conveyance operation in a state in which the moving member is located at the second position.

A sheet conveyance device includes a first conveyance member, and a drive transmission mechanism. The first conveyance member is configured to convey a sheet toward a second conveyance member. The drive transmission mechanism is configured to transmit a driving force of a driving source to the first conveyance member. The drive transmission mechanism includes a first drive transmitter and a second drive transmitter disposed coaxially with the first drive transmitter. The driving force is transmitted from the first drive transmitter to the second drive transmitter. The second drive transmitter is rotatable relative to the first drive transmitter within at least a predetermined angular range.

A one-way clutch includes: an outer member that has an inner periphery including an internal gear; an inner member that is rotatably disposed, and includes an engagement portion; and a planetary gear that is rotatable relative to the inner member, meshes with the internal gear, and is prevented from rotating by engaging with the engagement portion, wherein in a state in which the outer member and the inner member rotate together, the planetary gear engages with the engagement portion; in a state in which relative rotation between the outer member and the inner member is performed, the planetary gear disengages from the engagement portion; and in a state in which the planetary gear engages with the engagement portion, a top land of the internal gear abuts on a bottom land of the planetary gear.

A drive transmission device includes a rotatable driving member; a rotatable follower member, and an elastic member. The drive transmission device includes a first rotatable member and a second rotatable member. The first rotatable member includes first and second driving portions and a limiting portion. The second rotatable member includes a first driven portion, a second driven portion and a contact portion contacting the limiting portion. The second driving portion is adjacent to the limiting portion with respect to a rotational axis direction of the first rotatable member. The second driven portion is adjacent to the contact portion with respect to a rotational direction of the second rotatable member.

A sheet supply apparatus detachably attached to an image forming apparatus is configured to receive a drive force from the image apparatus to supply sheet to the image forming apparatus. The sheet supply apparatus includes a sheet supply tray, a sheet supply roller, a first transmission mechanism configured to transmit a drive force from the image forming apparatus to the sheet supply roller, a second transmission mechanism including an output member and configured to transmit a drive force supplied from the image forming apparatus to the output member, a clutch mechanism configured to intermittently transmit a drive force from the image forming apparatus to the second transmission mechanism, a latch member pivotable between a restriction position and an allowance position, a change cam, a sector gear, a rotational force applying member, an engaging member, a first engagement portion, a second engagement portion, and an electromagnetic solenoid.

A sheet transport device includes a transport roller, a drive source, and a gear train The transport roller transports a sheet. The gear train transmits rotating force from the drive source to the transport roller. The gear train includes a movable gear and a leaf spring. The movable gear is configured to move between a normal position where transmission of the rotating force to the transport roller is enabled, and a disengaged position where the transmission of the rotating force to the transport roller is interrupted, and also to move in an axial direction, and includes a helical gear that generates force to axially move in one direction, when the movable gear moves from the normal position to the disengaged position. The leaf spring buffers the movement of the movable gear in the one direction.

A sheet conveyance device includes a first conveyance member, and a drive transmission mechanism. The first conveyance member is configured to convey a sheet toward a second conveyance member. The drive transmission mechanism is configured to transmit a driving force of a driving source to the first conveyance member. The drive transmission mechanism includes a first drive transmitter and a second drive transmitter disposed coaxially with the first drive transmitter. The driving force is transmitted from the first drive transmitter to the second drive transmitter. The second drive transmitter is rotatable relative to the first drive transmitter within at least a predetermined angular range.

A sheet transport device includes a transport roller, a drive source, and a gear train. The transport roller transports a sheet. The gear train transmits rotating force from the drive source to the transport roller. The gear train includes a movable gear and a leaf spring. The movable gear is configured to move between a normal position where transmission of the rotating force to the transport roller is enabled, and a disengaged position where the transmission of the rotating force to the transport roller is interrupted, and also to move in an axial direction, and includes a helical gear that generates force to axially move in one direction, when the movable gear moves from the normal position to the disengaged position. The leaf spring buffers the movement of the movable gear in the one direction.

A printer includes: a conveyor that conveys a printing medium; a printing device that prints an image; a roller provided downstream of the printing device in a conveying direction; an opposed member opposed to the roller; a motor; a coupling mechanism that power-transmittably couples the motor and the roller to each other and rotates the roller in a first direction during driving of the motor, the first direction being a rotational direction for conveying the printing medium downstream in the conveying direction; and a moving mechanism that moves the roller between (i) a first position at which the roller is power-transmittably coupled to the motor by the coupling mechanism, and the printing medium is nipped by the roller and the opposed member and (ii) a second position at which the roller is power-transmittably coupled to the motor by the coupling mechanism and separated from the printing medium.