Sheet feeding device and image forming apparatus having the same
A sheet feeding device includes a first conveying roller conveying the sheet, a second conveying roller conveying the sheet conveyed from the first conveying roller, a first driving gear having a first number of teeth, and a second driving gear having a second number of teeth. When a first meshing frequency defined by multiplication of the first number of teeth and the number of rotations of the first driving gear is defined as A, and a second meshing frequency defined by multiplication of the second number of teeth and the number of rotations of the second driving gear is defined as B, the first meshing frequency A and the second meshing frequency B are set so as to satisfy the following expression (1):A>B.
1. A sheet feeding device, comprising:
a sheet conveying path in which a sheet is conveyed in a predetermined direction;
a first conveying roller pair having a first conveying roller disposed in the sheet conveying path and conveying the sheet in the predetermined direction;
a second conveying roller pair having a second conveying roller disposed downstream of the first conveying roller in the sheet conveying path and conveying the sheet, conveyed from the first conveying roller, in the predetermined direction;
a first driving gear attached coaxially to the first conveying roller for rotation therewith and having a first number of teeth;
a second driving gear attached coaxially to the second conveying roller for rotation therewith and having a second number of teeth; and
a drive source driving the first driving gear and the second driving gear,
wherein, when an end of the sheet on an upstream side in the predetermined direction is sandwiched by the first conveying roller pair and an end of the sheet on a downstream side in the predetermined direction is sandwiched by the second conveying roller pair, the expression A>B is satisfied, where A is a first meshing frequency defined by multiplication of the first number of teeth and the number of rotations of the first driving gear and B is a second meshing frequency defined by multiplication of the second number of teeth and the number of rotations of the second driving gear.
2. The sheet feeding device according to claim 1 , wherein when an outer diameter of the first conveying roller is defined as DA and an outer diameter of the second conveying roller as DB, the outer diameters DA and DB are set so as to satisfy the following expression (2):
DA>DB (2).
3. The sheet feeding device according to claim 1 , wherein
the first conveying roller includes a first driving roller conveying the sheet in the predetermined direction, and a first driven roller that is disposed to face the first driving roller so as to sandwich the sheet therebetween and is driven to rotate due to the sheet conveyance by the first driving roller,
the second conveying roller includes a second driving roller conveying the sheet, conveyed from the first driving roller, in the predetermined direction, and a second driven roller that is disposed to face the second driving roller so as to sandwich the sheet therebetween and is driven to rotate due to the sheet conveyance by the second driving roller, and
when a first slip ratio, defined by a ratio between a rotational linear speed obtained when the first driven roller is driven to rotate and a conveyance speed of the sheet at a position of the first driven roller, is defined as SA, and a second slip ratio, defined by a ratio between a rotational linear speed obtained when the second driven roller is driven to rotate and a conveyance speed of the sheet at a position of the second driven roller, is defined as SB,
the first slip ratio SA and the second slip ratio SB are set so as to satisfy the following expression (3):
SA<SB (3).
4. The sheet feeding device according to claim 2 , wherein
the first conveying roller includes a first driving roller having the outer diameter DA and conveying the sheet in the predetermined direction, and a first driven roller that is disposed to face the first driving roller so as to sandwich the sheet therebetween and is driven to rotate due to the sheet conveyance by the first driving roller,
the second conveying roller includes a second driving roller having the outer diameter DB and conveying the sheet, conveyed from the first driving roller, in the predetermined direction, and a second driven roller that is disposed to face the second driving roller so as to sandwich the sheet therebetween and is driven to rotate due to the sheet conveyance by the second driving roller, and
when a first slip ratio, defined by a ratio between a rotational linear speed obtained when the first driven roller is driven to rotate and a conveyance speed of the sheet at a position of the first driven roller, is defined as SA, and a second slip ratio, defined by a ratio between a rotational linear speed obtained when the second driven roller is driven to rotate and a conveyance speed of the sheet at a position of the second driven roller, is defined as SB,
the first slip ratio SA and the second slip ratio SB are set so as to satisfy the following expression (3):
SA<SB (3).
5. The sheet feeding device according to claim 1 , wherein the sheet conveying path has a curved conveying part that is curved between the first conveying roller and the second conveying roller.
6. The sheet feeding device according to claim 1 , wherein slidability of the second conveying roller during the sheet conveyance is greater than slidability of the first conveying roller during the sheet conveyance, when the same sheet is conveyed under same conditions.
7. The sheet feeding device according to claim 1 , further comprising:
a sheet storage section storing the sheet; and
a pickup roller feeding the sheet from the sheet storage section to the first conveying roller, wherein
the first conveying roller includes a sheet feeding roller conveying the sheet, conveyed from the pickup roller, to the second conveying roller, and a retard roller that is disposed to face the sheet feeding roller in contact therewith and rotates in the same rotation direction as a rotation direction of the sheet feeding roller to prevent sheet double-feeding, and
the first driving gear is attached coaxially to the sheet feeding roller for rotation therewith.
8. A fixing device, comprising:
a sheet discharge path in which a sheet is discharged in a predetermined direction;
a fixing roller disposed in the sheet discharge path and performing fixation to a toner image on the sheet;
a pressing roller disposed to face the fixing roller in contact therewith with the sheet discharge path therebetween and forming a fixing nip portion with the fixing roller;
a discharging roller disposed downstream of the fixing roller in the sheet discharge path and discharging the sheet, subjected to the fixation, in the predetermined direction;
a fixing roller side driving gear attached coaxially to the fixing roller for rotation therewith and having a first number of teeth; and
a discharging roller side driving gear attached coaxially to the discharging roller for rotation therewith and having a second number of teeth, wherein
when a first meshing frequency defined by multiplication of the first number of teeth and the number of rotations of the fixing roller side driving gear is defined as F1, and a second meshing frequency defined by multiplication of the second number of teeth and the number of rotations of the discharging roller side driving gear is defined as F2, the first meshing frequency F1 and the second meshing frequency F2 are set so as to satisfy the following expression (4):
F1>F2 (4).
9. The fixing device according to claim 8 , wherein when an outer diameter of the fixing roller is defined as DC and an outer diameter of the discharging roller as DD, the outer diameters DC and DD are set so as to satisfy the following expression (5):
DC>DD (5).
10. An image forming apparatus, comprising:
an image forming section forming an image on a sheet; and
a sheet feeding device feeding the sheet to the image forming section,
the sheet feeding device including:
a sheet conveying path in which a sheet is conveyed in a predetermined direction;
a first conveying roller pair having a first conveying roller disposed in the sheet conveying path and conveying the sheet in the predetermined direction;
a second conveying roller pair having a second conveying roller disposed downstream of the first conveying roller in the sheet conveying path and conveying the sheet, conveyed from the first conveying roller, in the predetermined direction;
a first driving gear attached coaxially to the first conveying roller for rotation therewith and having a first number of teeth;
a second driving gear attached coaxially to the second conveying roller for rotation therewith and having a second number of teeth; and
a drive source driving the first driving gear and the second driving gear,
wherein, when an end of the sheet on an upstream side in the predetermined direction is sandwiched by the first conveying roller pair and an end of the sheet on a downstream side in the predetermined direction is sandwiched by the second conveying roller pair, the expression A>B is satisfied, where A is a first meshing frequency defined by multiplication of the first number of teeth and the number of rotations of the first driving gear and B is a second meshing frequency defined by multiplication of the second number of teeth and the number of rotations of the second driving gear.
11. The image forming apparatus according to claim 10 , wherein when an outer diameter of the first conveying roller is defined as DA and an outer diameter of the second conveying roller as DB, the outer diameters DA and DB are set so as to satisfy the following expression (2):
DA>DB (2).
12. The image forming apparatus according to claim 10 , wherein:
the first conveying roller includes a first driving roller conveying the sheet in the predetermined direction, and a first driven roller that is disposed to face the first driving roller so as to sandwich the sheet therebetween and is driven to rotate due to the sheet conveyance by the first driving roller,
the second conveying roller includes a second driving roller conveying the sheet, conveyed from the first driving roller, in the predetermined direction, and a second driven roller that is disposed to face the second driving roller so as to sandwich the sheet therebetween and is driven to rotate due to the sheet conveyance by the second driving roller, and
when a first slip ratio, defined by a ratio between a rotational linear speed obtained when the first driven roller is driven to rotate and a conveyance speed of the sheet at a position of the first driven roller, is defined as SA, and a second slip ratio, defined by a ratio between a rotational linear speed obtained when the second driven roller is driven to rotate and a conveyance speed of the sheet at a position of the second driven roller, is defined as SB,
the first slip ratio SA and the second slip ratio SB are set so as to satisfy the following expression (3):
SA<SB (3).
13. The image forming apparatus according to claim 11 , wherein:
the first conveying roller includes a first driving roller having the outer diameter DA and conveying the sheet in the predetermined direction, and a first driven roller that is disposed to face the first driving roller so as to sandwich the sheet therebetween and is driven to rotate due to the sheet conveyance by the first driving roller,
the second conveying roller includes a second driving roller having the outer diameter DB and conveying the sheet, conveyed from the first driving roller, in the predetermined direction, and a second driven roller that is disposed to face the second driving roller so as to sandwich the sheet therebetween and is driven to rotate due to the sheet conveyance by the second driving roller, and
when a first slip ratio, defined by a ratio between a rotational linear speed obtained when the first driven roller is driven to rotate and a conveyance speed of the sheet at a position of the first driven roller, is defined as SA, and a second slip ratio, defined by a ratio between a rotational linear speed obtained when the second driven roller is driven to rotate and a conveyance speed of the sheet at a position of the second driven roller, is defined as SB,
the first slip ratio SA and the second slip ratio SB are set so as to satisfy the following expression (3):
SA<SB (3).
14. The image forming apparatus according to claim 10 , wherein the sheet conveying path has a curved conveying part that is curved between the first conveying roller and the second conveying roller.
15. The image forming apparatus according to claim 10 , wherein slidability of the second conveying roller during the sheet conveyance is greater than slidability of the first conveying roller during the sheet conveyance, when the same sheet is conveyed under same conditions.
16. The image forming apparatus according to claim 10 , wherein:
the sheet feeding device further includes a sheet storage section storing the sheet and a pickup roller feeding the sheet from the sheet storage section to the first conveying roller,
the first conveying roller includes a sheet feeding roller conveying the sheet, conveyed from the pickup roller, to the second conveying roller, and a retard roller that is disposed to face the sheet feeding roller in contact therewith and rotates in the same rotation direction as a rotation direction of the sheet feeding roller to prevent sheet double-feeding, and
the first driving gear is attached coaxially to the sheet feeding roller for rotation therewith.
17. An image forming apparatus, comprising:
an image forming section forming a toner image on a sheet; and
a fixing device fixing the toner image, formed on the sheet, onto the sheet,
the fixing device including:
a sheet discharge path in which a sheet is discharged in a predetermined direction;
a fixing roller disposed in the sheet discharge path and performing fixation to a toner image on the sheet;
a pressing roller disposed to face the fixing roller in contact therewith with the sheet discharge path therebetween and forming a fixing nip portion with the fixing roller;
a discharging roller disposed downstream of the fixing roller in the sheet discharge path and discharging the sheet, subjected to the fixation, in the predetermined direction;
a fixing roller side driving gear attached coaxially to the fixing roller for rotation therewith and having a first number of teeth; and
a discharging roller side driving gear attached coaxially to the discharging roller for rotation therewith and having a second number of teeth, wherein
when a first meshing frequency defined by multiplication of the first number of teeth and the number of rotations of the fixing roller side driving gear is defined as F1, and a second meshing frequency defined by multiplication of the second number of teeth and the number of rotations of the discharging roller side driving gear is defined as F2, the first meshing frequency F1 and the second meshing frequency F2 are set so as to satisfy the following expression (4):
F1>F2 (4).
18. The image forming apparatus according to claim 17 , wherein when an outer diameter of the fixing roller is defined as DC and an outer diameter of the discharging roller as DD, the outer diameters DC and DD are set so as to satisfy the following expression (5):
DC>DD (5).