Duplex printer with a unidirectional drive source and a gear train with a partially toothed gear

摘要

An image forming apparatus includes a switchback roller which switches between a normal rotation direction and a reverse rotation direction, first and second gear train for rotating the switchback roller in the normal and reverse rotation directions, respectively, a switching unit including a pendulum gear which is movable among a first engagement position where the pendulum gear is engaged with the first gear train, a second engagement position where the pendulum gear is engaged with the second gear train, and a disengagement position where the pendulum gear is not engaged with the first gear train and the second gear train. The switching unit is switchable among a first mode where the pendulum gear is held at the first engagement position, a second mode where the pendulum gear is held at the second engagement position, and a third mode where the pendulum gear is held at the disengagement position.

主权项

1. An image forming apparatus comprising:
a driving source configured to generate a one-direction rotational driving force; a switchback roller configured to be switched between a normal rotation direction and a reverse rotation direction for switching a conveyance direction of a recording medium having an image formed thereon by an image forming unit; a first gear train configured to transmit the one-direction rotational driving force of the driving source to the switchback roller such that a rotation direction of the switchback roller becomes the normal rotation direction; a second gear train configured to transmit the one-direction rotational driving force of the driving source to the switchback roller such that the rotation direction of the switchback roller becomes the reverse rotation direction; and a switching unit including:
a pendulum gear configured to engage a gear train for transmitting the one-direction rotational driving force of the driving source with any of the first gear train and the second gear train;a holder configured to support the pendulum gear to be rotatable;a cam configured to press the holder to move the holder, thereby moving the pendulum gear supported on the holder;a drive gear configured to receive the one-direction rotational driving force from the driving source; anda partially toothed gear configured to be able to receive the rotational driving force through the drive gear and operate the cam, wherein the partially toothed gear includes:a toothed portion configured to be engaged with the drive gear; anda non-tooth portion configured to face the drive gear in each of a first mode, a second mode and a third mode, wherein the pendulum gear is configured to be movable among:
a first engagement position where the pendulum gear is engaged with the first gear train,a second engagement position where the pendulum gear is engaged with the second gear train, anda disengagement position where the pendulum gear is not engaged with any of the first gear train and the second gear train, and wherein the switching unit is configured to be switchable among:
the first mode in which the pendulum gear is held at the first engagement position such that the one-direction rotational driving force of the driving source is transmitted to the first gear train,the second mode in which the pendulum gear is held at the second engagement position such that the one-direction rotational driving force of the driving source is transmitted to the second gear train, andthe third mode in which the pendulum gear is held at the disengagement position such that the one-direction rotational driving force of the driving source is not transmitted to any of the first gear train and the second gear train.