Apparatus for controlling the toner density in an electrophotographic machine

An apparatus for controlling the density of a developer comprising:

• a developer container in which a developer composed of a carrier and toner is enclosed;
• detecting means for magnetically detecting information about the density of the toner in said developer container;
• toner supply means for supplying the toner in accordance with an output value of information about the detected density of the toner;
• waveform forming means for forming a waveform obtained by reducing an output value from said detecting means, by operating mechanical means for periodically raking out the developer existing on a detecting surface of said detecting means;
• toner-density-detection delaying means for delaying detection of the density of the toner for a delay time period, from a time at which the output value has been reduced by said waveform forming means, to a time at which the output value of information about the density of the toner is restored,
• wherein said toner supply means is operable in accordance with information about the density of the toner detected after said delay time period;
• and
• minimum-value detecting means for detecting a minimum value or a value close to the minimum value of the output value which is reduced by said waveform forming means,
• wherein said toner-density-detection delaying means is operated when the minimum value or the value close to the minimum value has been detected.

A developing apparatus comprising:

• a developer container in which a developer composed of a carrier and toner is enclosed;
• toner-density detecting means for magnetically detecting information about the density of the toner in said developer container;
• waveform forming means for forming a waveform obtained by reducing an output value from said detecting means by operating mechanical means for periodically raking out the developer existing on a detecting surface of said detecting means so that the density of the toner is controlled in accordance with the output value of a waveform of vibrations formed by said waveform forming means;
• sampling means for sampling the waveform of vibrations at predetermined intervals;
• sampling-number setting means for setting the number of sampling operations in a predetermined period of the waveforms of the vibrations;
• and
• output-value detecting means for detecting a predetermined output value which is reduced by said sampling means,
• wherein a determination is made that a malfunction has occurred when the output value which is reduced is not detected by said output-value detecting means after sampling has been performed by a predetermined number of times.