Image forming apparatus

An image forming apparatus, comprising:

• a developing device that feeds toner to an image carrying member;
• a first container and a second container that each store toner to be supplied to the developing device;
• a toner supplying device that supplies the toner in the first and second containers to the developing device;
• and
• a remaining quantity sensing portion that senses remaining quantities of toner in the first and second containers,
• wherein
• the toner supplying device comprises:
• a single supply pipe that is connected to the developing device and through which the toner passes into the developing device;
• a first conveyance pipe that is connected between the first container and the supply pipe and through which the toner is conveyed from the first container toward the supply pipe;
• a second conveyance pipe that is connected between the second container and the supply pipe and through which the toner is conveyed from the second container toward the supply pipe;
• a first conveyance member that is rotatably disposed inside the first conveyance pipe and that conveys the toner from the first container toward the supply pipe;
• a second conveyance member that is rotatably disposed inside the second conveyance pipe and that conveys the toner from the second container toward the supply pipe;
• a clutch that enables selectively one of the first and second conveyance members to be driven,
• a first sensing shaft that is coupled to the first conveyance member to rotate together with the first conveyance member;
• a second sensing shaft that is coupled to the second conveyance member to rotate together with the second conveyance member;
• and
• a single optical sensor that senses rotation of the first and second sensing shafts,
• the remaining quantity sensing portion counts numbers of revolutions of the first and second sensing shafts based on an output signal from the optical sensor and, based on the numbers of revolutions, senses the remaining quantities of toner in the first and second containers,
• the first sensing shaft has a first light-shielding plate that moves into and out of an optical path of the optical sensor,
• the second sensing shaft has a second light-shielding plate that moves into and out of the optical path of the optical sensor,
• one of the first and second light-shielding plates rotates together with the first or second conveying member driven by the clutch and makes contact with another of the first and second light-shielding plates, thereby to make the another of the first and second light-shielding plates move out of the optical path of the optical sensor.