Sheet conveying apparatus and image forming apparatus

A sheet conveying apparatus having a first conveying roller pair configured to nip and convey a sheet, and a second conveying roller pair provided upstream of the first conveying roller pair in a sheet conveying direction, the second conveying roller pair being configured to nip and convey the sheet, the sheet conveying apparatus being configured to correct skew feeding of the sheet by a tip of the sheet abutting against a nip portion of the first conveying roller pair, the sheet conveying apparatus comprising:

• a conveying unit having a third conveying roller that conveys the sheet, and a guide member that guides the sheet, the third conveying roller being provided between the first conveying roller pair and the second conveying roller pair, the guide member being configured to support the third conveying roller and to be rotatable, the conveying unit being configured to shift along with the guide member to an abutting position where the third conveying roller abuts on a counter roller or a separating position where the third conveying roller is separated from the counter roller;
• a driving portion configured to switch a position of the conveying unit to the abutting position and the separating position;
• a detecting member configured to detect the position of the conveying unit;
• and
• a control portion configured to switch the position of the conveying unit according to a basis weight of the sheet,
• wherein when a first sheet with a predetermined basis weight is conveyed, the control portion performs such a control that the third conveying roller is located in the abutting position and a tip of the first sheet is guided along the guide member to a nip portion between the third conveying roller and the counter roller with the third conveying roller being located in the abutting position, and
• wherein when a second sheet with a basis weight greater than that of the first sheet is conveyed, the control portion performs such a control that the third conveying roller is located in the separating position and a tip of the second sheet is guided along the guide member with the third conveying roller being located in the separating position.