An image forming apparatus includes: an image bearing member, a developing device, and a controller configured to execute an operation in a forced consumption mode. The controller includes a difference calculating portion, an integrating portion, and a flag. In a case where the flag is set when a predetermined time is elapsed after the integrated value exceeds the predetermined threshold, the image formation on the predetermined number of the recording materials is effected and then the controller executes the operation in the forced consumption mode, and in a case where the flag is reset when the predetermined time is elapsed after the integrated value exceeds the predetermined threshold, the image formation on the predetermined number of the recording materials is effected and then the controller continues an image forming operation without executing the operation in the forced consumption mode.

A developing device includes a developing container, first and second stirring-conveyance members, a developer carrier, a toner concentration sensor, a scraper, and a scraper attachment unit. The second stirring-conveyance member includes a rotation shaft, a first spiral blade to convey developer in an axial direction, and a second spiral blade to overlap a region where the first spiral blade is formed, which is opposite to the first spiral blade in phase, and lower than the first spiral blade in height in a radial direction. An absent region, where the second spiral blade does not exist, is formed in one pitch of the first spiral blade, the one pitch facing the toner concentration sensor. The scraper attachment unit is formed to extend, along a straight line passing through intersection points of the first and second spiral blades and parallel to the rotation shaft, into the absent region.

A toner is provided. The toner contains a polyester resin. The toner has a glass transition temperature (Tg1st) at first temperature rising of differential scanning calorimetry (DSC) of from 45 C. to 65 C. The toner includes a component insoluble in tetrahydrofuran (THF) having two glass transition temperatures (Tga1st and Tgb1st) at the first temperature rising of DSC, where Tga1st is in a range of 45 C. to 5 C. and Tgb1st is in a range of 45 C. to 70 C. The toner includes a component soluble in THF having a glass transition temperature (Tg2nd) at second temperature rising of DSC of from 40 C. to 65 C.

A development device includes a developer bearing, a regulation portion, and a magnetic field generation member that is provided inside of the developer bearing member. The magnetic field generation member includes a development pole a first magnetic pole, and a second magnetic pole. The magnetic field generation member has a region satisfying |(Br(a)Br(c))/10|<0.3, wherein Br(a) is a magnetic flux density in a normal direction relative to the surface of the developer bearing member on a position shifted by 5 from a point nearest to the regulation portion on the developer bearing member around a center of the developer bearing member, and Br(c) is the magnetic flux density around the developer bearing member on a position shifted by +5 from the point nearest to the regulation portion on the developer bearing member.

An image forming apparatus includes a correction amount calculator, a fluidity measuring unit, and an external additive amount calculator. The correction amount calculator calculates a correction amount of fluidity to correct the fluidity of a two-component developer. The fluidity measuring unit measures the fluidity of the two-component developer. The external additive amount calculator corrects the measured fluidity on the basis of the correction amount of fluidity, calculates the amount of an external additive of a toner from the corrected fluidity of the two-component developer, and determines the state of the external additive.

An image forming apparatus includes a developing unit attachment part to which developing units are to be attached, each of the developing units being associated with a first criteria for performing developer refreshing and a second criteria for performing developer refreshing, wherein the second criteria is defined so as to be met prior to the first criteria, and a controller configured to control a timing of developer refreshing executed for each of the developing units according to the first and second criteria values thereof, and a first developer tank that is located at a position higher than the developing unit and configured to contain the developer. When the first criteria for performing developer refreshing is met for at least one of the developing units, the controller causes developer refreshing to be performed for all developing units whose first or second criteria is met.

An object of the invention is to accurately grasp the fluidity of a developer and give proper feedback to an image forming process. An image forming device has a developing unit developing a latent image by transferring a developer to an image carrier, a fluidity measuring unit measuring fluidity of the developer, a correction amount computing unit computing a fluidity correction amount for correcting the fluidity of the developer measured by the fluidity measuring unit, and a process control unit changing a process condition of an image forming process. The process control unit selects, on the basis of the fluidity of the developer corrected based on the fluidity correction amount, an image forming process of changing a process condition from a plurality of image forming processes.

An electrostatic latent image developing toner includes toner particles. Each of the toner particles includes a toner mother particle and an external additive. The toner mother particle contains a binder resin. The external additive includes external additive particles adhering to a surface of the toner mother particle. Each of the external additive particles includes a titanium oxide particle and resin particles adhering to a surface of the titanium oxide particle.

A control unit performs control to satisfy T.sub.Va<T T.sub.Vb, where T is a time from a point when irradiation with light by a pre-exposure member is started to a point when a predetermined portion of the photosensitive member which is located at the pre-exposure position when the irradiation is started reaches a charging position, T.sub.Va is a time from the point when the irradiation is started to a point when application of a first voltage is started, and T.sub.Vb is a time from the point when the irradiation is started to a point when application of the second voltage is started.

A two-component developing agent contains a toner that contains a pulverized toner, the pulverized toner containing at least one type of polyester resin, a styrene-based resin or an aromatic petroleum resin, and Fisher-Tropsch wax, and a carrier that contains a silicone resin covering layer containing conductive fine powder.