Sheet processing apparatus and image forming system including the same

1. A sheet processing apparatus, comprising:

a conveyance path in which a sheet is conveyed in a predetermined conveyance direction;

a rotary member pair configured to nip a sheet conveyed in the conveyance path and rotate to convey while performing folding processing on the sheet, the rotary member pair having a first rotary member and a second rotary member, the first rotary member having a first circumferential surface part and a second circumferential surface part, a distance from the first circumferential surface part to a rotary shaft center of the first rotary member being longer than a distance from the second circumferential surface part to the rotary shaft center of the first rotary member, the second rotary member having a third circumferential surface part and a fourth circumferential surface part, a distance from the third circumferential surface part to a rotary shaft center of the second rotary member being longer than a distance from the fourth circumferential surface part to the rotary shaft center of the second rotary member; and

a guide portion provided between the first rotary member and the conveyance path and configured to guide a downstream edge of a sheet conveyed in the predetermined conveyance direction,

wherein, in a case that a sheet is conveyed to the conveyance path, the second circumferential surface part and the fourth circumferential surface part are set so as to be oriented toward the conveyance path,

wherein, in a case that the sheet is conveyed in the conveyance path in the predetermined conveyance direction, the guide portion guides a downstream edge of the sheet in the predetermined conveyance direction in a state in which the guide portion is held in contact with the second circumferential surface part, and in a case that the rotary member pair rotates to convey the sheet, the guide portion guides the sheet in a state in which the guide portion is held in contact with the first circumferential surface part, and

wherein the guide portion is configured to be movable to a first position at which the guide portion is held in contact with the first circumferential surface part and to a second position at which the guide portion is held in contact with the second circumferential surface part.

2. A sheet processing apparatus according to claim 1 , wherein the guide portion is urged so as to be always in slide contact with a circumferential surface of the first rotary member being rotated.

3. A sheet processing apparatus according to claim 1 , wherein the guide portion is provided so as to cover a part, which is closest to the conveyance path, of a circumferential surface of the first rotary member.

4. A sheet processing apparatus according to claim 1 , wherein the guide portion is provided so that a tip end of the guide portion is swingable.

5. A sheet processing apparatus according to claim 1 , wherein the first rotary member is provided downstream of the second rotary member in the predetermined conveyance direction.

6. A sheet processing apparatus according to claim 1 , further comprising an alignment unit configured to align a sheet in the conveyance path in a direction crossing the predetermined conveyance direction.

7. An image forming system, comprising:

an image forming unit configured to form an image on a sheet; and

a sheet processing apparatus configured to perform folding processing on a sheet conveyed from the image forming unit,

the sheet processing apparatus comprising:

a conveyance path in which a sheet is conveyed in a predetermined conveyance direction;

a rotary member pair configured to nip a sheet conveyed in the conveyance path and rotate to convey while performing the folding processing on the sheet, the rotary member pair having a first rotary member and a second rotary member, the first rotary member having a first circumferential surface part and a second circumferential surface part, a distance from the first circumferential surface part to a rotary shaft center of the first rotary member being longer than a distance from the second circumferential surface part to the rotary shaft center of the first rotary member, the second rotary member having a third circumferential surface part and a fourth circumferential surface part, a distance from the third circumferential surface part to a rotary shaft center of the second rotary member being longer than a distance from the fourth circumferential surface part to the rotary shaft center of the second rotary member; and

a guide portion disposed between the first rotary member and the conveyance path and configured to guide a downstream edge of a sheet conveyed in the predetermined conveyance direction,

wherein, in a case that a sheet is conveyed to the conveyance path, the second circumferential surface part and the fourth circumferential surface part are set so as to be oriented toward the conveyance path,

wherein, in a case that the sheet is conveyed in the conveyance path in the predetermined conveyance direction, the guide portion guides a downstream edge of the sheet in the predetermined conveyance direction in a state in which the guide portion is held in contact with the second circumferential surface part, and in a case that the rotary member pair rotates to convey the sheet, the guide portion guides the sheet in a state in which the guide portion is held in contact with the first circumferential surface part, and

wherein the guide portion is configured to be movable to a first position at which the guide portion is held in contact with the first circumferential surface part and to a second position at which the guide portion is held in contact with the second circumferential surface part.