A process cartridge includes an electrophotographic photoreceptor that includes a photosensitive layer and a protective layer on a conductive substrate in this order, and a charging member that includes an elastic layer and a surface layer on a conductive base material in this order and comes into contact with the electrophotographic photoreceptor to charge a surface of the electrophotographic photoreceptor, in which the protective layer in the electrophotographic photoreceptor is a cured film formed to contain a crosslinked material of a composition containing at least one compound X selected from the group consisting of a compound having a guanamine structure and a compound having a melamine structure and a charge transport material Y containing at least one group selected from the group consisting of OH, OCH.sub.3, NH.sub.2, SH, and COOH, a water contact angle ?1 of the surface of the electrophotographic photoreceptor is 65? or greater and less than 80?, and a water contact angle ?2 of a surface of the charging member satisfies a relationship of ?1<?2.

An electrophotographic photosensitive member includes at least one photosensitive layer on which a first photosensitive layer disposed on an outermost side thereof. The first photosensitive layer contains a charge generating material, a binder resin including a polyarylate resin with repeating units (1), (2), (3), and (4), an electron transport material, and a hole transport material.

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The electron transport material includes a compound represented by formula (10), (11), or (12). The hole transport material includes compounds represented by formulas (21) and (22):

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A percentage content of a number of repeats of the repeating unit (3) to the total number of repeats of the repeating units (1) and (3) is greater than 0% and less than 50%. A percentage content of a number of repeats of the repeating unit (4) to the total number of repeats of the repeating units (2) and (4) is at least 35% and less than 70%.

An image forming apparatus, including: a photoconductor; a developing device; a developer storage; a supplier configured to supply developer; an optical sensor; and a controller configured to execute: a developing process of developing an electrostatic latent image on the photoconductor; a usage-amount obtaining process of obtaining a usage amount of the developer; a supplying process of supplying the developer to the developing device every time when the obtained usage amount becomes equal to or greater than a first threshold; and a detecting process of detecting, by the optical sensor, an amount of the developer in the developing device every time when the obtained usage amount becomes equal to or greater than a second threshold larger than the first threshold, and wherein the controller is configured to execute the detecting process in a period different from a period in which the developing process is being executed.

A process cartridge includes a frame having a side surface at a side of the process cartridge. A photosensitive drum is supported by the frame, the photosensitive drum being rotatable about an axis thereof, the photosensitive drum including a first end positioned at the side of the process cartridge and a second end opposite to the first end in a direction of the axis of the photosensitive drum. A projection is positioned coaxial with the photosensitive drum and at the side of the process cartridge, with the projection projecting from the side surface of the frame in the axial direction of the photosensitive drum with at least a tip of the projection being exposed to outside of the process cartridge. A gear is positioned at the side of the process cartridge, with the gear being rotatable about an axis thereof, the gear having a plurality of teeth, with at least some of the teeth being exposed teeth that are uncovered by the frame and exposed to outside of the process cartridge, and with a tip of at least one of the exposed teeth facing the axis of the photosensitive drum.

A process cartridge including a drum cartridge, a developing cartridge, and a waste toner container, is provided. The drum cartridge includes a photosensitive drum including a photosensitive layer and a rotation axis extending in an axial direction, a drum cleaner arranged to contact the photosensitive drum, a cleaner frame configured to accommodate the drum cleaner therein, and a waste toner conveyer tube connected with the cleaner frame. The developing cartridge is movable to be attached to and detached from the drum cartridge and includes a developer roller. The waste toner container is movable to be attached to and detached from the drum cartridge. When the developing cartridge and the waste toner container are attached to the drum cartridge, the waste toner container is connected with the waste toner conveyer tube and is located on an opposite side of the developing cartridge to the photosensitive drum.

A terminal contact structure includes a first terminal provided on a removable body; a second terminal provided on an apparatus body in which the removable body is inserted, the second terminal not being in contact with the first terminal when the removable body is in a removable state, the second terminal being in contact with the first terminal when the removable body is in a fixed state; and a guide member provided on the apparatus body and having a first surface and a second surface, the first surface guiding the first terminal in an insertion direction in which the removable body is inserted, the second surface guiding the second terminal in a contact direction in which the second terminal comes into contact with the first terminal, the contact direction being a crossing direction that crosses the insertion direction.

In the image forming device, the main body has a loading port. The image bearing unit is configured to be detachably attached to the main body thorough the loading port. The toner unit is configured to be detachably attached to the main body thorough the loading port. The developer unit is configured to be detachably attached to the main body thorough the loading port. The toner unit, the developer unit, and the image bearing unit are located in this order from the loading port to an inside of the main body, when the toner unit, the developer unit, and the image bearing unit are attached in the main body. The toner unit is configured to be independently detached from the main body, when the image bearing unit and the developer unit are attached to the main body.

A photoconductor is provided. The photoconductor includes a cylindrical conductive support, a water-repellent resin film, a coating film, and a flange. The cylindrical conductive support has an end part having an inner circumferential surface having a surface roughness Rz of from 3 to 10 m. The water-repellent resin film is on the inner circumferential surface of the end part of the cylindrical conductive support. The coating film is on an outer circumferential surface of the cylindrical conductive support. The flange has a cylindrical fitting part having an outer circumferential surface secured to the inner circumferential surface of the end part of the cylindrical conductive support.

An electrophotographic photosensitive member includes a support member, an electroconductive layer, and photosensitive layer in this order. The electroconductive layer contains a binder and particles. The particles have a core containing titanium oxide, and a coating layer coating the core and containing titanium oxide doped with niobium or tantalum.

Disclosed herein is an electrophotographic photosensitive member in which leakage hardly occurs even in the case of using a layer containing metal oxide particles as an electrically conductive layer in the electrophotographic photosensitive member, and which is compatible with definition in output images, the electrophotographic photosensitive member sequentially including: a support, an electrically conductive layer, and a photosensitive layer, the electrically conductive layer containing a binder material and particles represented by General Formula (1).

Nb.sub.2.00O.sub.5.00-XN.sub.Y (1)

(In Formula (1), Nb is a niobium atom, O is an oxygen atom, N is a nitrogen atom, and 0.00<Y<X4.00.)