Patent ID: 8727492

Claim:
An image forming apparatus comprising: an image forming part configured and arranged to form an image by injecting a liquid; a waste liquid tank detachably attached to said image forming apparatus and configured and arranged to store a waste liquid discharged from said image forming part, the waste liquid tank having a memory element to store identification information A and waste liquid amount information B of said liquid tank; a memory unit that is different from said memory element incorporated in said waste liquid tank and stores identification information C and waste liquid amount information D of said waste liquid tank; and a control unit that manages information regarding said waste liquid tank, wherein each of the identification information A and the identification information C uniquely identifies said waste liquid tank, and each of the waste liquid amount information B and the waste liquid amount information D indicates an amount of liquid stored in said waste liquid tank; and wherein said control unit determines a current amount of the waste liquid currently retained in said waste liquid tank, when it is detected that said waste liquid tank is attached to said image forming apparatus, in accordance with a result of a comparison between the identification information A stored in said memory element of said waste liquid tank currently attached and the identification information C currently stored in said memory unit and a result of a comparison between the waste liquid amount B stored in said memory element of said waste liquid tank currently attached and the waste liquid amount D currently stored in said memory unit, and updates said current amount of the waste liquid in accordance with a subsequent operation of said image forming part, wherein said control unit determines that said waste liquid tank has not been replaced by a different waste liquid tank when the identification information A stored in said memory element of said waste liquid tank currently attached matches the identification information C previously acquired and currently stored in said memory unit, and said control unit selects a larger one of said waste liquid amount information B and said waste liquid amount information D and determines the larger one as said current amount of the waste liquid, wherein said control unit determines that said waste liquid tank has been replaced by a different waste liquid tank when the identification information A stored in said memory element of said waste liquid tank currently attached does not match the identification information C previously acquired and currently stored in said memory unit, and said control unit determines that said waste liquid tank currently attached is full when the waste liquid amount information B stored in said memory element of said waste liquid tank currently attached is not equal to zero.