Image forming apparatus having functional redundancy system

An image forming apparatus having a functional redundancy system, comprising:

• functional means comprising a plurality of functional portions, each of the plurality of functional portions having a predetermined inherent function, at least a part of the plurality of functional portions each having a potential function which is different from its predetermined inherent function and which is not ordinarily used;
• diagnosing means for making a diagnosis to judge whether or not a fault occurs in said functional means;
• ordinary control means for operating said plurality of functional portions in accordance with a first sequence such that said plurality of functional portions use their inherent functions when it is judged by said diagnosing means that no fault occurs;
• and
• redundancy system control means for operating, when it is judged by said diagnosing means that a fault occurs, functional portions, other than a functional portion which fails, in accordance with a second sequence which is different from said first sequence such that the inherent function of the functional portion which fails is replaced by the potential function of another functional portion.

An image forming apparatus having functional redundancy system, comprising:

• storing means for storing information concerning the contents of at least a part of the image forming apparatus in predetermined relational representation using functions, behavior and states which define a FBS diagram;
• means for retrieving a substitutable function which can be substituted for a particular function in the apparatus on the basis of the FBS diagram stored in the storing means;
• and
• redundancy system control means for operating the apparatus using a substitutable function retrieved by the means for retrieving.