Image forming apparatus having a developer deterioration detecting device

A color image forming apparatus having a latent image forming unit, a plurality of developing units containing toner of respective colors included in developer for respectively developing latent images formed by the latent image forming unit into toner images so as to form a color image by a superposition of the toner images in an image area of a surface of an image carrying member, a transfer unit for transferring the color image onto a recording sheet, a cleaning unit for removing residual toner from the surface after the transfer and a plurality of supplying units for respectively supplying the toner of the respective colors into the developing units, the color image forming apparatus comprising:

• means for measuring toner density in each developing unit, the toner density meaning toner content of the developer;
• drive control means for controlling a supply time period of each supplying unit based on the toner density measured in each developing unit;
• means for calculating average toner supply to each developing unit based on data of the drive time periods having been measured by a predetermined number of measurements in each developing unit;
• means for memorizing reference data including standard toner consumption data;
• and
• means for detecting deterioration of the developer contained in the developing unit based on a comparison of the average toner supply with the standard toner consumption data.

An image forming apparatus having latent image forming means for forming a latent image in an image area of a surface of an image carrying member, developing means for developing the latent image to form a toner image, transfer means for transferring the toner image on a recording sheet and cleaning means for removing residual toner from the surface, the image forming apparatus comprising:

• means for recursively measuring toner density of developer contained in the developing means;
• means for storing reference data including standard toner consumption data;
• means for calculating an average toner consumption consumed by the developing means based on data of the toner density accumulated from recursive measurements by the measuring means;
• and
• means for detecting deterioration of the developer in the developing means by comparing the average toner consumption with the standard toner consumption data.

An image forming apparatus provided with a latent image forming unit for forming a latent image in an image area of a surface of an image carrying member, a developing unit for developing the latent image to form a toner image, a supply unit for supplying toner of developer into the developing unit, a transfer unit for transferring the toner image onto a recording sheet and a cleaning unit for removing residual toner from the surface after the transfer, the image forming apparatus comprising:

• means for measuring toner density of the developer in the developing unit;
• means for generating a drive control signal, which measures toner content of developer contained in the developing unit and generates the drive control signal based on the toner density;
• drive control means responsive to the drive control signal for controlling a driving period of the supply unit;
• memory means for memorizing reference data of toner consumption by the developing unit;
• calculating means for calculating a consumption amount of toner consumed by the developing unit based on the driving period;
• detecting means for detecting the deterioration of the developer contained in the developing unit by comparing the calculated consumption amount with the reference data;
• control means for making the toner adhere to the surface from the developing unit when the detecting means detects the deterioration of the developer.