Image reading device, image forming apparatus

An image reading device comprising:

• an image sensor;
• a contact glass;
• a platen glass disposed side by side with the contact glass;
• a carriage supporting a light emission portion that emits light upward, and a light guide member that guides a reflection light of the light emitted from the light emission portion to the image sensor, the carriage configured to, upon application of a driving force, move along a predetermined moving path that passes through a first position located below the contact glass, a second position located below a first end portion of the platen glass, and a third position located below a second end portion of the platen glass, the first end portion being close to the contact glass, the second end portion being opposite to the first end portion;
• a main body portion storing the carriage, wherein the contact glass and the platen glass are disposed on an upper surface of the main body portion;
• a cover supported in such a way as to be displaced between a closing position and an opening position, the closing position being located on the upper surface of the main body portion where the cover covers the contact glass and the platen glass, the opening position being more separated from the upper surface of the main body portion than the closing position;
• a plurality of pairs of conveyance rollers provided in the cover and configured to, upon application of a driving force, convey a document sheet along a conveyance path that passes through positions along an upper surface of the contact glass, in a state where the cover is located at the closing position;
• and
• a drive device configured to selectively apply a driving force to the carriage and the plurality of pairs of conveyance rollers, wherein
• the drive device includes:
• an abutting member provided in the main body portion and configured to abut on the carriage that is moving from the second position side to the first position side, thereby stopping the carriage at the first position;
• a motor supported by the carriage;
• a first main body gear and a second main body gear that are supported by the carriage, and respectively rotate in conjunction with the motor;
• a cover input gear provided in the cover and configured to mesh with the first main body gear in a state where the carriage is located at a position between the first position and a predetermined relay region that is located between the first position and the second position;
• a cover output gear configured to cause the plurality of pairs of conveyance rollers to rotate in conjunction with the cover input gear;
• and
• a main rack gear that is a rack gear disposed in the main body portion in parallel to the moving path, and configured to mesh with the second main body gear in a state where the carriage is located in a region extending from the relay region to the third position, wherein
• in a state where the carriage is located at a position on the first position side with respect to the relay region, a load torque that is applied to the motor to drive the cover input gear when the carriage is fixed, is larger than a load torque that is applied to the motor to move the carriage when the cover input gear that meshes with the first main body gear, is fixed.