Developing unit, image forming apparatus incorporating same, and method of controlling amounts of toner

An image forming apparatus, comprising:

• an image bearing member to bear an electrostatic latent image on a surface thereof;
• and
• a developing unit including:
• a developer case to accommodate a two-component developer including toner particles and carrier particles;
• a developer bearing member disposed in the developer case and bearing the two-component developer to supply to an electrostatic latent image for development of the electrostatic latent image into a visible image;
• a developer supply path formed inside the developer case to supply the two-component developer along an axial direction of the developer bearing member;
• an agitation and conveyance member disposed in the developer supply path to agitate and convey the two-component developer;
• a toner collecting mechanism to collect toner particles from the two-component developer remaining on the developer bearing member after development;
• a collected toner conveyance path formed inside the developer case and separated from the developer supply path, comprising a collected toner conveying member disposed therewithin to convey toner collected by the toner collecting mechanism;
• a developer releasing area where the developer is separated from the developer bearing member using a magnetic repulsion force,
• the collected toner conveyance path and the developer supply path arranged in communication with each other in the vicinity of one end of the collected toner conveyance path in a direction of conveyance of collected toner so as to recirculate toner unused for development, and
• wherein the toner collecting mechanism is located outside of the developer releasing area, and the developer releasing area is located between an image development area and the toner collection mechanism,
• the image forming apparatus further including:
• a new toner container to contain new toner;
• a new toner supply path in communication with the new toner container and the developing unit to supply the new toner to the developing unit;
• a new toner conveyance member mounted on the new toner supply path to convey the new toner and control an amount of supply of the new toner;
• a collected toner conveyance member disposed in the collected toner conveyance path to convey the collected toner and control an amount of supply of collected toner;
• and
• a control unit to control an amount of conveyance of toner by the new toner conveyance member, an amount of conveyance of toner by the collected toner conveyance member, and an amount of collected toner collected by the toner collecting mechanism,
• the control unit controlling an amount of collected toner per unit of time such that, when an amount of collected toner per unit of time where the toner is transferred from the developing unit to the image bearing member and consumed at a development area is smaller than a reference amount, the amount of collected toner per unit of time collected by the toner collecting mechanism is conveyed by the collected toner conveyance member and exceeds the amount of supply of collected toner to be supplied to the developer supply path, and when the amount of consumed toner per unit of time is greater than the reference amount, the amount of collected toner per unit of time is reduced to below the amount of supply of collected toner,
• wherein a reference amount A corresponding to the reference amount is specified within a range satisfying an equation
• 0.02·x·T/t≦A≦0.07·x·T/t,
• where “x” represents an amount of consumed toner when one solid image is output, “T” represents the unit time corresponding to a reference period of time in which the control unit controls at least one of toner collection and supply of collected toner, and “t” represents a time required for printing one image in continuous image printing.

A method for controlling amounts of toner in an image forming apparatus including:

• an image bearing member to bear an electrostatic latent image on a surface thereof;
• and
• a developing unit including:
• a developer case to accommodate a two-component developer including toner particles and carrier particles;
• a developer bearing member disposed in the developer case and bearing the two-component developer to supply to an electrostatic latent image for development of the electrostatic latent image into a visible image;
• a developer supply path formed inside the developer case to supply the two-component developer along an axial direction of the developer bearing member;
• an agitation and conveyance member disposed in the developer supply path to agitate and convey the two-component developer;
• a toner collecting mechanism to collect toner particles from the two-component developer remaining on the developer bearing member after development;
• a collected toner conveyance path formed inside the developer case and separated from the developer supply path, comprising a collected toner conveying member disposed therewithin to convey toner collected by the toner collecting mechanism;
• a developer releasing area where the developer is separated from the developer bearing member using a magnetic repulsion force,
• the collected toner conveyance path and the developer supply path arranged in communication with each other in the vicinity of one end of the collected toner conveyance path in a direction of conveyance of collected toner so as to recirculate toner unused for development, and
• wherein the toner collecting mechanism is located outside of the developer releasing area, and the developer releasing area is located between an image development area and the toner collection mechanism,
• the image forming apparatus further including:
• a new toner container to contain new toner;
• a new toner supply path in communication with the new toner container and the developing unit to supply the new toner to the developing unit;
• a new toner conveyance member mounted on the new toner supply path to convey the new toner and control an amount of supply of the new toner;
• a collected toner conveyance member disposed in the collected toner conveyance path to convey the collected toner and control an amount of supply of collected toner;
• and
• a control unit to control an amount of conveyance of toner by the new toner conveyance member, an amount of conveyance of toner by the collected toner conveyance member, and an amount of collected toner collected by the toner collecting mechanism,
• the control unit controlling an amount of collected toner per unit of time such that, when an amount of collected toner per unit of time where the toner is transferred from the developing unit to the image bearing member and consumed at a development area is smaller than a reference amount, the amount of collected toner per unit of time collected by the toner collecting mechanism is conveyed by the collected toner conveyance member and exceeds than the amount of supply of collected toner to be supplied to the developer supply path, and when the amount of consumed toner per unit of time is greater than the reference amount, the amount of collected toner per unit of time is reduced to below the amount of supply of collected toner,
• the method comprising:
• (1) calculating the amount of collected toner bn, the amount of supply of collected toner cn, and the amount of supply of new toner dn according to Equation Set (1), when the amount of consumed toner an is equal to or smaller than a reference amount A corresponding the reference amount and a toner-empty sensor and a toner-full sensor detect neither an empty state nor a full state of the collected toner,
• bn=A−an+α,
• cn=α, and
• dn=A Equation Set (1);
• (2) calculating the amount of collected toner bn, the amount of supply of collected toner cn, and the amount of supply of new toner dn according to Equation Set (2) when the amount of consumed toner an is greater than a reference amount corresponding the reference amount and the toner-empty sensor and the toner-full sensor detect neither an empty state nor a full state of the collected toner,
• bn=β,
• cn=an−γ+β, and
• dn=γ Equation Set (2);
• (3) calculating the amount of collected toner bn, the amount of supply of collected toner cn, and the amount of supply of new toner dn according to Equation Set (3) when the amount of consumed toner an is equal to or smaller than the reference amount A corresponding to the reference amount and the toner-empty sensor has detected an empty state of the collected toner,
• bn=A−an+α,
• cn=0, and
• dn=A+α Equation Set (3);
• (4) calculating the amount of collected toner bn, the amount of supply of collected toner cn, and the amount of supply of new toner dn according to Equation Set (4) when the amount of consumed toner an is greater than a reference amount A corresponding to the reference amount and the toner-empty sensor has detected an empty state of the collected toner,
• bn=β,
• cn=0, and
• dn=an+β Equation Set (4);
• (5) calculating the amount of collected toner bn, the amount of supply of collected toner cn, and the amount of supply of new toner dn according to Equation Set (5) when the amount of consumed toner an is equal to or smaller than the reference amount and the toner-full sensor has detected a full state of the collected toner,
• bn=A−an+α,
• cn=A+α, and
• dn=0 Equation Set (5);
• (6) calculating the amount of collected toner bn, the amount of supply of collected toner cn, and the amount of supply of new toner dn according to Equation Set (6) when the amount of consumed toner an is greater than a reference amount and the toner-full sensor has detected a full state of the collected toner,
• bn=β,
• cn=an+β, and
• dn=0 Equation Set (6),
• where “α”, “β”, and “γ” represent respective arbitrary values, “α” represents any set value of 0 or above according to a volume of capacity of the collected toner conveyance path, “β” and “γ” represent any set value of 0 or above, and “A” represents a reference amount corresponding to an average amount of consumed toner;
• and
• (7) controlling to obtain the calculated amounts.