1. Field of the Invention
The present invention relates to a technique for calculating toner consumption in an image forming apparatus.
2. Description of the Related Art
In electrophotographic image forming apparatuses, such as printers, copiers and facsimiles, which form images using a toner, a need exists for figuring out toner consumption or residual quantity of toner as a matter of convenience for maintenance services such as toner replenishment. Particularly, the recent years have seen increasing demands for allowing a toner charged in the apparatus to be used as effectively as possible or with minimum toner waste, while exactly predicting time when the toner is used up, as well as for preventing the degradation of image quality as a result of shortage of the remaining toner. Hence, the image forming apparatuses of this type are faced with a demand for further increasing the accuracies of toner counting technique.
In response to such demands, there have heretofore been proposed techniques for accurately determining the toner consumption. According to a calculation method of toner consumption as disclosed in Japanese Patent Application Laid-Open Gazette No. 2002-174929, for instance, determines the toner consumption in the following manner, noting a fact that a non-linear relation exists between the continuity of dots and the toner consumption. Print dot strings are classified into three patterns including isolated dots, consecutive double dots and intermediate-value dots. The number of generated dots in each of the patterns is counted so as to determine the toner consumption based on the resultant count value.
According to the prior-art technique, however, the unit of count is the number of “print dots”, whereas the amount of toner adherent to the intermediate-value dots is calculated on assumption that an equal amount of toner is adhered to each of the dots. That is, the prior-art technique obviates close study on the amount of toner adherent to the respective types of print dots. As a result, the prior-art technique sometimes falls short of fully meeting the demand for even higher accuracies of the calculation of toner consumption.