Conveyor and image forming apparatus with the conveyor

1. A conveyor configured to convey a sheet, comprising:

a sheet conveying path extending in a first direction;

a first conveying unit disposed at a first position along the sheet conveying path, and including a first shaft, first and second rolls attached to the first shaft and spaced from one another by a predetermined roll distance in a second direction perpendicular to the first direction, third and forth rolls confronting the first and second rolls respectively to define two first nip roll sets nipping the sheet and conveying the sheet in the first direction, and first elastic bodies that give the first nip roll sets first nip forces that are applied to the sheet; and

a second conveying unit disposed at a second position downstream from the first position along the sheet conveying path, and including a second shaft, fifth rolls attached to the second shaft and sixth rolls confronting the respective fifth rolls to define second nip roll sets that nip and convey the sheet in the first direction, the second nip roll sets being disposed so that every second nip roll set of the second conveying unit is at a position in the second direction inward of the two first nip roll sets of the first conveying unit so that the second nip roll set is arranged within an area corresponding to the roll distance of the first nip roll set, and a second elastic body that gives the second nip roll sets a second nip force that is applied to the sheet;

a belt connecting the first shaft and the second shaft; and

a drive source delivering a driving force to the belt so that the driving force of the drive source is transmitted simultaneously to the first and second shafts, wherein

the first conveying unit feeds the sheet at a feed rate faster than a feed rate by the second conveying unit,

each of the first nip forces is stronger than the second nip force and is applied to a region of the sheet outward of the second conveying unit in the second direction and while the second conveying unit is applying the second nip force to a downstream part of the sheet so that a skew of the sheet at the second conveying unit is prevented by the first conveying unit.

2. The conveyor according to claim 1 , wherein

the first conveying unit includes a third nip roll set within the roll distance of the first nip roll sets.

3. The conveyor according to claim 2 , wherein

the first conveying unit includes a third elastic body that gives the third nip roll set a third nip force that is applied to the sheet; and

each of the first nip forces is stronger than the third nip force.

4. The conveyor according to claim 3 , wherein

the third nip force is stronger than the second nip force.

5. The conveyor according to claim 1 , wherein

the drive source bi-directionally rotates the first shaft and the second shaft.

6. The conveyor according to claim 1 , wherein

the first elastic bodies include a coil spring extending along a rotational center axis of at least one of the third roll and the fourth roll, and

the coil spring rotatably supports the at least one of the third roll and the fourth roll.

7. The conveyor according to claim 1 , wherein

the second nip roll set includes:

a third shaft configured to rotatably support the sixth rolls; and

an elastic member configured to support the third shaft.

8. An image forming apparatus configured to form an image on a sheet including a first surface and a second surface opposite to the first surface, comprising:

a resist roller configured to send the sheet downstream at a predetermined timing;

a transfer unit configured to transfer a toner image onto the first surface of the sheet sent from the resist roller;

a fixing unit configured to fix the toner image formed on the first surface of the sheet sent from the transfer unit; and

the conveyor according to claim 1 ; wherein

the first conveying unit is configured to convey the sheet sent from the fixing unit in a discharge direction to discharge the sheet or in a duplexing direction to send the sheet to a conveying path for transferring and fixing a toner image on the second surface; and

the second conveying unit is provided in the conveying path.