A mode control section forms a plurality of reference toner images having different densities on a photosensitive drum, where the frequency of an alternating-current voltage of a development bias is varied with a potential difference between direct-current voltages of a development roller and the photosensitive drum maintained constant, generates a reference straight line indicating a relationship between a toner amount of each reference toner image obtained by converting the density of the measured reference toner image into weight, and a representative value of current values of a development current measured during formation of the reference toner image, and acquires the amount of electrostatic charge of toner using the reference straight line.

A resin molded product whose main component consists of an ethylene-vinyl acetate copolymer resin and carbon black. The ethylene-vinyl acetate copolymer resin has an MFR of 0.5 g/10 min or more and 20 g/10 min or less. The carbon black has an average primary particle diameter of 55 nm or more and 100 nm or less and a DBP oil absorption amount of 100 mL/100 g or more and 300 mL/100 g or less. The content of vinyl acetate is 2.9 parts by mass or more and 12.3 parts by mass or less based on 100 parts by mass of the main component. The resin molded product has a surface resistivity of 720 / or less.

A powder-amount detection device includes an outer electrode, an inner electrode, and a detector. The outer electrode is disposed outside a powder container to be replaceably installed to an image forming apparatus. The inner electrode is disposed inside a powder supply port of the powder container. The detector is configured to apply an electric field between the outer electrode and the inner electrode to detect a capacitance between the outer electrode and the inner electrode.

An image forming apparatus includes a density detecting portion configured to detect a density of a control toner image being formed every time when an image is formed on a predetermined number of sheets in successively forming the image on sheets, and a control portion configured to control an amount of supplying developer. The control portion controls forming of the control toner image so that the predetermined number of image-formed sheets is a first number in a period of time from when the use of a developing apparatus is started, until when an amount of developer of the developing apparatus reaches a set value which is larger than an amount of initial developer, and the predetermined number of image-formed sheets is a second number which is larger than the first number of image-formed images, after the amount of developer of the developing apparatus reaches the set value.

The present disclosure provides a process cartridge and a potential detection part. The process cartridge includes a cartridge body, a photosensitive drum rotatably installed at the cartridge body, and a potential detection part configured to detect an electrical signal on the image-forming region. The potential detection part includes a detection starting portion and a detection ending portion; the detection starting portion and the detection ending portion respectively correspond to a detection starting position and a detection ending position of a detectable region of the potential detection part along a first direction; a maximum distance along the first direction between orthographic projections of the detection starting portion and the detection ending portion on the image-forming region is L1; a length of the image-forming region along the first direction is L2; the first direction is in parallel with an axis direction of the photosensitive drum; and L1/L2>?.

An image forming apparatus includes a developer unit, a toner container, a capacitance sensor, a toner amount detector, and a determining unit. The toner container is located to be removably attachable to the image forming apparatus. The toner container supplies a toner to the developer unit. The capacitance sensor is located on a supply passage for the toner from the toner container to the developer unit. The capacitance sensor detects an electric charge amount and a relative dielectric constant of the toner. The electric charge amount is an electric charge amount when the toner passes through the supply passage. The toner amount detector detects an amount of the toner passing through the supply passage based on the electric charge amount detected by the capacitance sensor. The determining unit determines whether the relative dielectric constant of the toner detected by the capacitance sensor is in a predetermined range.

An image forming apparatus determines a toner density erroneous detection state based on a patch image density in patch detection auto toner replenishing and, when the toner density erroneous detection state is determined, offsets a target toner density by the amount of erroneous detection so that the actual toner density becomes a desired toner density.

An image forming apparatus includes a developer unit, a toner container, a capacitance sensor, a toner amount detector, and a determining unit. The toner container is located to be removably attachable to the image forming apparatus. The toner container supplies a toner to the developer unit. The capacitance sensor is located on a supply passage for the toner from the toner container to the developer unit. The capacitance sensor detects an electric charge amount and a relative dielectric constant of the toner. The electric charge amount is an electric charge amount when the toner passes through the supply passage. The toner amount detector detects an amount of the toner passing through the supply passage based on the electric charge amount detected by the capacitance sensor. The determining unit determines whether the relative dielectric constant of the toner detected by the capacitance sensor is in a predetermined range.

A powder-amount detection device includes an outer electrode, an inner electrode, and a detector. The outer electrode is disposed outside a powder container to be replaceably installed to an image forming apparatus. The inner electrode is disposed inside a powder supply port of the powder container. The detector is configured to apply an electric field between the outer electrode and the inner electrode to detect a capacitance between the outer electrode and the inner electrode.

A developing device includes a developer bearing member, a developing container which accommodates developer, a conveying screw which conveys the developer accommodated in the developing container, and an inductance sensor which includes a detecting portion which detects magnetic permeability of the developer accommodated in the developing container. The conveying screw includes a rotary shaft, a blade which is spirally formed on an outer circumference of the rotary shaft, and a rib formed to protrude outwardly from the outer circumference of the rotary shaft. The rib is disposed opposite the detection portion with respect to a conveying direction of the conveying screw and is provided with a magnet, with magnetic flux density of the magnet being in the range of 20 mT to 60 mT.