Drive transmission device and image forming apparatus incorporating the same
A drive transmission device includes a drive transmission member and a rotation shaft. The drive transmission member has an insertion portion. The rotation shaft includes a press-fit portion and another flat portion. The press-fit portion press-fits into the insertion portion after insertion of an axial tip of the rotation shaft into the insertion portion and includes a press-fit flat portion parallel to an axial direction of the rotation shaft. The other flat portion is at a position closer to the axial tip than the press-fit flat portion. The insertion portion has an inner-wall flat portion to contact the press-fit flat portion when the press-fit portion is press-fitted into the insertion portion. The other flat portion is parallel to the press-fit flat portion that has a distance from an axial center of the rotation shaft smaller than the press-fit flat portion.
1 . A drive transmission device comprising:
a drive transmission member to receive a driving force from a drive source, the drive transmission member having an insertion portion; and
a rotation shaft that is inserted into the insertion portion to be held, the rotation shaft having a D-cut shape extending in an axial direction of the rotation shaft from an endmost surface of a tip end of the rotation shaft that is perpendicular to a longitudinal axis of the rotation shaft, with a rounded segment extending in the axial direction and with flat portions arranged at different positions in the axial direction, the rotation shaft including:
a first shaft portion along the axial direction having a first flat portion extending in the axial direction from the tip end, and
a second shaft portion along the axial direction having
a first inclined surface extending in the axial direction from the first flat portion and being inclined with respect to the first flat portion; and
a second flat portion extending in the axial direction from the first inclined surface and being pressed in contact with the insertion portion,
wherein the second flat portion is parallel to the first flat portion that has a distance from an axial center of the rotation shaft smaller than the second flat portion,
wherein the insertion portion has a D-cut shape where an inner-wall surface comprises an inner-wall flat portion and an inner-wall rounded portion, and further has an entrance edge portion and an exit edge portion opposite the entrance edge portion,
wherein the D-cut shape of the insertion portion extends from the entrance edge portion to the exit edge portion, and
wherein the inner-wall flat portion contacts the second flat portion when the second flat portion is press-fitted into the insertion portion.
2 . The drive transmission device according to claim 1 , wherein an angle between the first inclined surface and the first flat portion at a most upstream position of the first flat portion in a direction of insertion of the tip end is equal to or lower than an angle between a second inclined surface of the entrance edge portion and the inner-wall flat portion of the drive transmission member.
3 . The drive transmission device according to claim 1 , wherein a height of the first inclined surface relative to the first flat portion at a most upstream position of the first flat portion in a direction of insertion of the tip end is equal to or less than a height of a second inclined surface of the entrance edge portion relative to the inner-wall flat portion of the drive transmission member.
4 . The drive transmission device according to claim 1 ,
wherein a length of the second flat portion in the axial direction is longer than a length of the first flat portion in the axial direction.
5 . The drive transmission device according to claim 1 ,
wherein the second flat portion extends from the first inclined surface to a stopper wall opposite the first inclined surface in the axial direction.
6 . The drive transmission device according to claim 1 , further comprising
a stopper to prevent the rotation shaft from disengaging from the insertion portion, wherein
the first shaft portion has a circumferential groove placed outside the insertion portion after the rotation shaft passes through the insertion portion and is press-fitted,
the stopper is fitted in the circumferential groove, and
a position of the circumferential groove in the axial direction is closer to the tip end than the first inclined surface.
7 . The drive transmission device according to claim 1 ,
wherein the drive transmission member is one of a belt pulley or a gear.
8 . The drive transmission device according to claim 1 ,
wherein the drive transmission member is a resin-molded product.
9 . The drive transmission device according to claim 1 ,
wherein the insertion portion of the drive transmission member is formed with a through hole, and
wherein a relation of H 1 ≤H 3 <H 2 is satisfied, where when the through hole is viewed from the axial direction, H 1 represents a distance between the axial center of the rotation shaft and the first flat portion of the rotation shaft, H 2 represents a distance between the axial center of the rotation shaft and the second flat portion of the rotation shaft, and H 3 represents a distance between a center of the through hole and the inner-wall flat portion.
10 . The drive transmission device according to claim 1 ,
wherein the rotation shaft has a mark indicating an insertion position of the rotation shaft with respect to the insertion portion of the drive transmission member.
11 . An image forming apparatus for forming an image on a recording medium, the apparatus comprising:
a driven member; and
the drive transmission device according to claim 1 to transmit the driving force of the drive source to the driven member.
12 . The drive transmission device according to claim 1 , wherein
the first shaft portion has a circumferential groove in the rounded segment, and
a first rounded portion of the rounded segment and a second rounded portion of the rounded segment on opposing sides of the circumferential groove have a same distance from the axial center of the rotation shaft.
13 . The drive transmission device according to claim 12 , further comprising
a stopper fitted in the circumferential groove preventing the rotation shaft from disengaging from the insertion portion.
14 . The drive transmission device according to claim 1 , wherein:
the entrance edge portion is inclined so as to widen, in a direction from inside toward outside, relative to a diameter of the inner-wall surface, and
the exit edge portion is inclined so as to widen, in a direction from the inside toward the outside, relative to the diameter of the inner-wall surface.
15 . The drive transmission device according to claim 14 ,
wherein the insertion portion has a symmetrical shape.
16 . A drive transmission device comprising:
a drive transmission member to receive a driving force from a drive source, and
a rotation shaft that is inserted into an insertion portion of the drive transmission member to be held, the rotation shaft having a D-cut shape with a rounded segment extending in an axial direction of the rotation shaft, and with flat portions arranged at different positions in the axial direction, the rotation shaft including:
a first shaft portion along the axial direction having a first flat portion, the first flat portion extending in the axial direction from an endmost surface of a tip end of the rotation shaft that is perpendicular to a longitudinal axis of the rotation shaft, and
a second shaft portion along the axial direction having
a first inclined surface extending in the axial direction from the first flat portion and being inclined with respect to the first flat portion, and
a second flat portion extending in the axial direction from the first inclined surface,
wherein the insertion portion has a D-cut shape where an inner-wall surface comprises an inner-wall flat portion and an inner-wall rounded portion, and further has an entrance edge portion and an exit edge portion opposite the entrance edge portion with a second inclined surface,
where in the D-cut shape of the insertion portion extends from the entrance edge portion to the exit edge portion,
wherein the inner-wall flat portion contacts the second flat portion when the second flat portion is press-fitted into the insertion portion, and
wherein, after the first shaft portion of the rotation shaft passes a second inclined surface of the entrance edge portion, the second inclined surface is pressed in contact with the first inclined surface of the rotation shaft and the rotation shaft is inserted while the drive transmission member is being deformed.
17 . The drive transmission device according to claim 16 ,
wherein an angle between the first inclined surface and the first flat portion at a most upstream position of the first flat portion in a direction of insertion of the tip end is equal to or lower than an angle between the second inclined surface of the entrance edge portion and the inner-wall flat portion of the drive transmission member.
18 . The drive transmission device according to claim 16 ,
wherein a height of the first inclined surface relative to the first flat portion at a most upstream position of the first flat portion in a direction of insertion of the tip end is equal to or less than a height of the second inclined surface of the entrance edge portion relative to the inner-wall flat portion of the drive transmission member.
19 . An image forming apparatus for forming an image on a recording medium, the apparatus comprising:
a driven member; and
the drive transmission device according to claim 16 to transmit the driving force of the drive source to the driven member.
20 . The drive transmission device according to claim 16 ,
where in the insertion portion has a symmetrical shape.