Apparatus for controlling toner replenishment in electrostatographic printer

An electrostatographic machine comprising:

• means for contacting an electrostatic image-bearing member with a development mix of toner and carrier particles, wherein the toner is selectable from a first type which exhibits toning contrast characteristics which vary predictably with changes in the concentration of toner particles in the developer mix and a second type which exhibits unpredictable changes in toning contrast as the toner concentration changes;
• means for replenishing the toner in the mix;
• means for producing a contrast signal having a value proportional to toning contrast;
• means for producing a concentration signal having a value indicative of the ratio of toner to carrier in the mix, said concentration signal being substantially insensitive to the toning contrast;
• and
• means having a first state for actuating replenishment of toner of the first type according to the value of said contrast signal and a second state for actuating replenishment of toner of the second type according to the value of said concentration signal.

An electrostatographic machine comprising:

• means for contacting an electrostatic image-bearing member with a development mix of toner and carrier particles, wherein the toner is selectable from a first type which exhibits toning contrast characteristics which vary predictably with changes in the concentration of toner particles in the developer mix and a second type which exhibits unpredictable changes in toning contrast as the toner concentration changes;
• means for replenishing the toner in the mix;
• means for producing a concentration signal having a value indicative of the ratio of toner to carrier in the mix;
• means for producing a depletion signal having a value indicative of the rate of toner usage;
• and
• means having a first state for actuating replenishment of toner of the first type according to the value of said depletion signal and a second state for actuating replenishment of toner of the second type according to the value of at least said concentration signal.

An electrostatographic machine comprising;

• means for contacting an electrostatic image-bearing member with a development mix of toner and carrier particles, wherein the toner is selectable from a first type and a second type;
• means for replenishing the toner in the mix;
• means for producing a contrast signal having a value related to the toning contrast of the machine;
• a toner monitor which produces a concentration signal having a value indicative of the ratio of toner to carrier in the mix;
• means for producing a depletion signal having a value indicative of the rate of toner usage, said depletion signal producing means being selectively adjustable to change the response to toner usage in accordance with said contrast signal;
• and
• means having a first state for actuating replenishment of toner of the first type proportionally according to the value of said depletion signal and a second state for actuating replenishment of toner of the second type proportionally according to the value of at least said concentration signal.

An electrostatographic machine comprising;

• a recording member having image areas;
• means for substantially uniformly charging said recording member to a primary voltage;
• means for imagewise exposing the charged recording member to produce discrete latent charge images;
• means, including a biased electrode, for developing the latent charge images with toner selectable from a first type and a second type;
• the electrode bias, the exposure level, and the primary voltage being process control parameters;
• means for controlling at least one of the process control parameters for a given image area to adjust the maximum output image density D.sub.max ;
• means for producing a depletion signal;
• means for proportionally converting the depletion signal to a replenishment control signal;
• means, for the given image area, for comparing the value of said at least one of the controlled process control parameters to a predetermined target value to produce a difference signal;
• means for adjusting the constant of proportionallity of the converting means in response to the difference signal;
• a toner monitor which produces a concentration signal having a value indicative of the ratio of toner to carrier in the mix;
• and
• means having a first state for actuating replenishment of toner of the first type proportionally according to the value of said depletion signal and a second state for actuating replenishment of toner of the second type proportionally according to the value of at least said concentration signal.

An electrostatographic machine comprising:

• means for contacting an electrostatic image-bearing member with a development mix of toner and carrier particles, wherein the toner is selectable from a first type which exhibits toning contrast characteristics which vary predictably with changes in the concentration of toner particles in the developer mix and a second type which exhibits unpredictable changes in toning contrast as the toner concentration changes;
• means for replenishing the toner in the mix;
• means for producing an actual concentration signal having a value indicative of the ratio of toner to carrier in the mix;
• means for producing a predetermined target toner concentration signal;
• means for producing a contrast signal having a value proportional to toning contrast;
• and
• means having (1) a first state for actuating replenishment of toner of the first type according to a comparison between said actual toner concentration signal and said contrast signal and (2) a second state for actuating replenishment of toner of the second type according to a comparison between said actual toner concentration signal and said target toner concentration signal.