Image forming apparatus including a developer replenishing device for a two-ingredient type developer

An image forming apparatus comprising:

• a developing unit configured to develop a latent image formed on an image carrier with a two-ingredient type developer made up of a toner and a carrier;
• toner replenishing means for replenishing a toner stored in a toner storing portion to said developing unit;
• and
• a carrier storing portion storing a carrier and constructed independently of said toner storing portion;
• wherein the carrier is fed from said carrier storing portion to said developing unit by a toner conveying force of said toner replenishing means;
• and wherein said toner replenishing means comprises:
• an air pump configured to convey the toner from said toner storing portion with compressed air;
• and
• a toner conveying tube forming part of a toner replenishing path that extends from said toner storing portion to said developing unit;
• wherein a carrier replenishing path, included in carrier replenishing means and extending from said carrier storing portion to said toner replenishing path, joins said toner conveying tube.

An image forming apparatus comprising:

• a developing unit configured to develop a latent image formed on an image carrier with a two-ingredient type developer made up of a toner and a carrier;
• toner replenishing means for replenishing a toner stored in a toner storing portion to said developing unit;
• and
• a carrier storing portion storing a carrier and constructed independently of said toner storing portion;
• wherein the carrier is fed from said carrier storing portion to said developing unit by a toner conveying force of said toner replenishing means;
• and wherein the carrier is replenished by independent control only when the toner is replenished.

An image forming apparatus comprising:

• a plurality of developing units each for developing a latent image formed on an image carrier with a two-ingredient type developer made up of a toner of a particular color and a carrier;
• a plurality of toner storing portions each storing a toner of a particular color;
• a plurality of toner replenishing means each for replenishing the toner of a particular color from an associated one of said plurality of toner storing portions to an associated one of said plurality of developing units;
• and
• a single carrier storing portion storing a carrier and constructed independently of said plurality of toner storing portions;
• wherein the carrier stored in said carrier storing portion is distributed and is replenished to each developing unit by a toner conveying force of said toner replenishing means associated with said developing unit;
• and wherein the carrier is caused to join the toner in a toner replenishing path that extends from any one of said toner storing portion to said developing unit associated therewith, said apparatus further comprising a replenishing member disposed in a carrier replenishing path between said carrier storing portion and said toner replenishing path and configured to prevent the toner from entering said carrier storing portion and replenish the carrier by a preselected amount.

An image forming apparatus comprising:

• a developing unit configured to develop a latent image formed on an image carrier with a two-ingredient developer made up of a toner and a carrier;
• toner replenishing means for replenishing a toner stored in a toner storing portion to said developing unit;
• and
• carrier replenishing means for replenishing a carrier stored in a carrier storing portion to said developing unit;
• said toner replenishing means comprising:
• a single axis, eccentric screw pump using a discharge pressure;
• and
• air feeding means for feeding compressed air to a position adjoining an outlet of said screw pump to thereby fluidize the toner;
• wherein said carrier replenishing means is connected to a suction port of said air feeding means, whereby an air and carrier mixture is fed to the outlet of said screw pump.

An image forming apparatus comprising:

• a developing unit configured to develop a latent image formed on an image carrier with a two-ingredient developer made up of a toner and a carrier;
• toner replenishing means for replenishing a toner stored in a toner storing portion to said developing unit;
• and
• carrier replenishing means for replenishing a carrier stored in a carrier storing portion to said developing unit;
• said toner replenishing means comprising:
• a single axis, eccentric screw pump using a discharge pressure;
• and
• air feeding means for feeding compressed air to an inside of said toner storing portion and a position adjoining an outlet of said screw pump to thereby fluidize the toner;
• wherein said carrier replenishing means is connected to a suction port of said air feeding means, whereby an air and carrier mixture is fed to the inside of said toner storing portion.

An image forming apparatus comprising:

• a developing unit configured to develop a latent image formed on an image carrier with a two-ingredient developer made up of a toner and a carrier;
• toner replenishing means for replenishing a toner stored in a toner storing portion to said developing unit;
• and
• carrier replenishing means for replenishing a carrier stored in a carrier storing portion to said developing unit;
• said toner replenishing means comprising:
• a single axis, eccentric screw pump using a suction pressure;
• and
• air feeding means for feeding compressed air to an inside of said toner storing portion and an outlet of said screw pump to thereby fluidize the toner;
• wherein said carrier replenishing means is connected to a suction port of said air feeding means, whereby an air and carrier mixture is fed to the inside of said toner storing portion.

An image forming apparatus comprising:

• a developing unit configured to develop a latent image formed on an image carrier with a two-ingredient developer made up of a toner and a carrier;
• toner replenishing means for replenishing a toner stored in a toner storing portion to said developing unit;
• and
• carrier replenishing means for replenishing a carrier stored in a carrier storing portion to said developing unit;
• wherein said toner replenishing means comprises air feeding means for feeding compressed air to an inside a toner cartridge while said carrier replenishing means is connected to a suction port of aid air feeding means, whereby an air and carrier mixture is fed to the inside of said toner cartridge.