An image forming apparatus detects a first current value and a second current value of currents flowing between an image bearing member and a developer carrying member. When a difference between the detected first current value and the detected second current value exceeds a threshold in a state in which the image bearing member and the developer carrying member are rotated and a first developing voltage is applied to the developer carrying member, a controller controls AC voltage applied to the developer carrying member.

A resin member includes a base material and a resin molded body disposed on the base material, the resin molded body containing a main component constituted by an ethylene-vinyl acetate copolymer resin and a carbon black. The resin molded body has two or more peaks within a range of 25° C. to 80° C. in an endothermic curve obtained through measurement performed by heating from 25° C. to 150° C. at 5° C./min with a differential scanning calorimetry (DSC) apparatus.

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 Ω/□ or less.

The image forming apparatus includes a developing device, a toner container, a first mechanism, a toner sensor, and a controller. The developing device adheres toner to an electrostatic latent image on a photoconductor to form a toner image. The toner container supplies toner to the developing device. The first mechanism causes a toner interface to undulate in the toner container. The toner sensor detects a capacitance between a first electrode and a second electrode arranged apart from the first electrode. The controller determines a remaining amount of toner in the toner container based on detection information from the toner sensor.

An image forming apparatus including a developing unit with a developing container configured to contain a developer including a toner and a carrier, and configured to develop the electrostatic latent image by using the developer in the developing container. A sensor, which is provided on an outer wall of the developing container, is configured to output a pulse signal that changes in frequency depending on a toner concentration of the developer in the developing container. A controller is provided to control supply of the toner to the developing unit by detecting the toner concentration based on the time required for the pulse number to reach a predetermined count number.

The image forming apparatus includes a developing device, a toner container, a first mechanism, a toner sensor, and a controller. The developing device adheres toner to an electrostatic latent image on a photoconductor to form a toner image. The toner container supplies toner to the developing device. The first mechanism causes a toner interface to undulate in the toner container. The toner sensor detects a capacitance between a first electrode and a second electrode arranged apart from the first electrode. The controller determines a remaining amount of toner in the toner container based on detection information from the toner sensor.

A resonance circuit (2) includes a capacitor (C1) and an inductor (L1, L2) of which an inductance is changed depending on developer including toner, and generates an output voltage corresponding to the inductance. A detecting circuit (3) detects the toner on the basis of the output voltage. An adjustment-purpose closed circuit (4) includes a semi-fixed resistor (VR1) and an adjustment inductor (L3) that forms magnetic coupling with the inductor (L1, L2), and causes an inductance of the inductor (L1, L2), a resonance frequency of the resonance circuit (2), an amplitude of the output voltage and a detected toner amount to be adjustable with a variable resistance value of the semi-fixed resistor (VR1).

The image forming apparatus includes a developing device, a toner container, a first mechanism, a toner sensor, and a controller. The developing device adheres toner to an electrostatic latent image on a photoconductor to form a toner image. The toner container supplies toner to the developing device. The first mechanism causes a toner interface to undulate in the toner container. The toner sensor detects a capacitance between a first electrode and a second electrode arranged apart from the first electrode. The controller determines a remaining amount of toner in the toner container based on detection information from the toner sensor.

An image forming apparatus includes a toner charge amount predictor, a toner developing resistance calculator, and a determiner. The toner developing resistance calculator calculates a toner developing resistance on the basis of a bias voltage applied to a developing device and a measured developing current by dividing a value of the bias voltage by a value of the developing current when a developing device develops an electrostatic latent image formed on the surface of an image carrier to form a toner image. The toner charge amount predictor predicts a toner charge amount of a toner which is supplied to the image carrier by the developing device on the basis of a density of the toner image and the developing current. The determiner determines a state of the developing device on the basis of the toner charge amount and the toner developing resistance.

An image forming apparatus includes a toner charge amount predictor, a toner developing resistance calculator, and a determiner. The toner developing resistance calculator calculates a toner developing resistance on the basis of a bias voltage applied to a developing device and a measured developing current by dividing a value of the bias voltage by a value of the developing current when a developing device develops an electrostatic latent image formed on the surface of an image carrier to form a toner image. The toner charge amount predictor predicts a toner charge amount of a toner which is supplied to the image carrier by the developing device on the basis of a density of the toner image and the developing current. The determiner determines a state of the developing device on the basis of the toner charge amount and the toner developing resistance.