An image forming apparatus includes a reverse roller pair configured to reverse a conveyance direction of a recording medium between a first direction and a second direction, a first conveyance roller pair configured to convey the recording medium in the first direction, and a second conveyance roller pair configured to convey the recording medium in the second direction. A first distance is between the first conveyance roller pair and a reversal position in which a trailing edge of the recording medium is located when the conveyance direction is reversed. A second distance is between the reversal position and the second conveyance roller pair. An absolute value of a difference between the first distance and the second distance is an integer multiple of a circumferential length of a drive roller of the reverse roller pair or within a predetermined range from the integer multiple.

A retaining ring 1 for a shaft 2a usable with a bearing 3 having an outer ring 3a and an inner ring 3b fixed on the shaft, wherein the inner ring 3b and the outer ring 3a are rotatable relative to each other, and the retaining ring 1 is provided on the shaft 2a adjacent to the bearing 3 in a thrust direction to restrict a position of the bearing 3 in the thrust direction, the retaining ring 1 includes a protrusion 1a protruding in the thrust direction from a surface opposing the inner ring 3b in the thrust direction to contact the inner ring 3b so that the retaining ring 1 is out of contact from the outer ring 3a.

A retaining ring 1 for a shaft 2a usable with a bearing 3 having an outer ring 3a and an inner ring 3b fixed on the shaft, wherein the inner ring 3b and the outer ring 3a are rotatable relative to each other, and the retaining ring 1 is provided on the shaft 2a adjacent to the bearing 3 in a thrust direction to restrict a position of the bearing 3 in the thrust direction, the retaining ring 1 includes a protrusion 1a protruding in the thrust direction from a surface opposing the inner ring 3b in the thrust direction to contact the inner ring 3b so that the retaining ring 1 is out of contact from the outer ring 3a.

A medium conveying apparatus includes feed roller pairs spaced and located in a direction perpendicular to a medium conveying direction, to separate and feed a medium, and conveying roller pairs located on a downstream side of the feed roller pairs in the medium conveying direction, and spaced and located in the direction perpendicular to the medium conveying direction. For each of the conveying roller pairs, a diameter of an outer end in the direction perpendicular to the medium conveying direction of at least one conveying roller is larger than a diameter of an inner end in the direction perpendicular to the medium conveying direction of said conveying roller, and a total D of differences between the diameter of the outer end and the diameter of the inner end of each conveying roller is 0.06 mm or more and 1.00 mm or less.

A medium conveying apparatus includes feed roller pairs spaced and located in a direction perpendicular to a medium conveying direction, to separate and feed a medium, and conveying roller pairs located on a downstream side of the feed roller pairs in the medium conveying direction, and spaced and located in the direction perpendicular to the medium conveying direction. For each of the conveying roller pairs, a diameter of an outer end in the direction perpendicular to the medium conveying direction of at least one conveying roller is larger than a diameter of an inner end in the direction perpendicular to the medium conveying direction of said conveying roller, and a total D of differences between the diameter of the outer end and the diameter of the inner end of each conveying roller is 0.06 mm or more and 1.00 mm or less.

A medium transport device includes a feeding roller that feeds a recording medium, a transport roller that transports the recording medium toward a recording head, and a transport motor which is a common driving source for the feeding roller and the transport roller. The medium transport device includes a power transmission mechanism that transmits power of the transport motor to the feeding roller, and a control section that controls a current of the transport motor. The control section measures a current value flowing through the transport motor during driving as a measured current value, and adds a predetermined offset value to the measured current value to set a second limit value as a limit value of the current supplied to the transport motor.

A medium transport device includes a feeding roller that feeds a recording medium, a transport roller that transports the recording medium toward a recording head, and a transport motor which is a common driving source for the feeding roller and the transport roller. The medium transport device includes a power transmission mechanism that transmits power of the transport motor to the feeding roller, and a control section that controls a current of the transport motor. The control section measures a current value flowing through the transport motor during driving as a measured current value, and adds a predetermined offset value to the measured current value to set a second limit value as a limit value of the current supplied to the transport motor.

A sheet conveyance apparatus includes a switching member to execute a pivot operation and a conveyance portion to convey a sheet at a first conveyance speed where a driving motor rotates at a first rotational speed, and to convey the sheet at a second conveyance speed which is greater than zero and slower than the first conveyance speed where the driving motor rotates at a second rotational speed which is greater than zero and slower than the first rotational speed. Where a control portion conveys a first sheet at the first conveyance speed, the switching member executes the pivot operation at the second operating speed before the first sheet arrives at the switching member and the conveyance portion, and rotates the driving motor at the first rotational speed after the pivot operation has been executed and before the first sheet arrives at the conveyance portion.

A sheet conveyance apparatus includes a switching member to execute a pivot operation and a conveyance portion to convey a sheet at a first conveyance speed where a driving motor rotates at a first rotational speed, and to convey the sheet at a second conveyance speed which is greater than zero and slower than the first conveyance speed where the driving motor rotates at a second rotational speed which is greater than zero and slower than the first rotational speed. Where a control portion conveys a first sheet at the first conveyance speed, the switching member executes the pivot operation at the second operating speed before the first sheet arrives at the switching member and the conveyance portion, and rotates the driving motor at the first rotational speed after the pivot operation has been executed and before the first sheet arrives at the conveyance portion.

A sheet conveyor unit is connected to downstream side of an upstream side unit in a sheet conveying direction. The sheet conveyor unit includes a convey guide for receiving a sheet discharged from outlet of the upstream side unit. The convey guide is constituted of a pair of guide members disposed to face each other with a predetermined space therebetween. The guide members have the same shape and include base parts having guide surfaces that form a sheet conveying path when combined to face each other, and inclined parts bent to directions apart from the guide surfaces from one end of the base parts in the sheet conveying direction so as to form a receiving port. The convey guide is attached selectively to one of positions different in at least one of a height direction and the sheet conveying direction with respect to an apparatus main body.