In a first image formation mode, an image is formed with a first development contrast C1 and a specific dot pattern is formed with a second development contrast C2, which is lower than the first development contrast C1; in a second image formation mode, an image is formed with a third development contrast C3 and a specific dot pattern is formed with a fourth development contrast C4, which is lower than the third development contrast C3; and when C1 (=C2/C1) denotes a ratio between the second development contrast C2 and the first development contrast C1, and C2 (=C4/C3) denotes a ratio between the fourth development contrast C4 and the third development contrast C3, C2<C1 is satisfied.

An image forming apparatus includes a photosensitive member including a photosensitive layer and a protective layer provided outside the photosensitive layer; a charging member configured to electrically charge the photosensitive member; an exposure device configured to expose, to light, the photosensitive member charged by the charging member; a detecting member configured to detect a surface potential of the photosensitive member; and an output portion configured to output information on a lifetime of the photosensitive member. The output portion outputs the information on the basis of an exposure amount with which the photosensitive member charged is exposed to light and a detection result of the surface potentials of the photosensitive member by the detecting member before and after the photosensitive member is exposed to the light with the exposure amount.

An image forming apparatus includes a photosensitive member, a corona charger including a discharging electrode and a grid electrode having a surface layer containing a carbon atom as a main component and configured to electrically charge the photosensitive member under application of a voltage to the discharging electrode and the grid electrode, and an output portion configured to output information on a lifetime of the grid electrode. The output portion outputs the information on the basis of an index value of an amount of use of the grid electrode correlating with a product of a value of a grid current flowing through the grid electrode and a time of flowing of the grid current through the grid electrode.

An image forming apparatus includes a photoconductor, a charging roller for charging the photoconductor, a current sensor for detecting a value of current flowing through the photoconductor or the charging roller as a result of application of voltage to the charging roller, an acquisition sensor for acquiring an environment value representing an environment state inside the image forming apparatus, and a processor configured to estimate a film thickness of the photoconductor, based on a value of current detected by the current sensor when a state in which the environment value falls within a predetermined range continues for a predetermined time or longer.

An image forming apparatus includes a development current detector that detects an actual measurement value of a development current, a development current calculator that calculates a provisional calculation value of a development current based on an image formation condition, and an image-defect determiner that determines whether or not an image defect occurs, based on the actual measurement value of the development current detected by the development current detector and the provisional calculation value of the development current calculated by the development current calculator.

An image forming apparatus includes an image bearing member, a charging roller, a toner image forming portion, a voltage source, a detecting member, a controller, and a test executing portion configured to execute an operation in a test mode in which in a period in advance of the image forming period, a plurality of test AC voltages having a test peak-to-peak voltage with different frequencies are successively applied to the charging roller and alternating currents are detected by the detecting member. The test executing portion sets a predetermined peak-to-peak voltage on the basis of a specific frequency which is a maximum frequency at which a relationship between the frequencies and the alternating currents acquired in the operation in the test mode maintains linearity.

In an image forming apparatus, a control unit performs a control for determining a surface potential A to determine a first voltage to be applied to a charge roller by a charge voltage application circuit so that a surface potential of a photosensitive drum becomes a first potential. The charge voltage application circuit thereafter applies the first voltage to the charge roller to charge the photosensitive drum. In such a state, the control unit performs a second control to determine a light amount of a laser light source, so that the surface potential of the photosensitive drum becomes a second potential. In such a manner, a potential of a photosensitive drum surface is detected with high accuracy. Moreover, a time taken to detect the potential of the photosensitive drum surface is shortened.

An image forming apparatus includes an image bearing member, a rotatable endless intermediary transfer belt, an inner roller, an outer roller, a power source, a detecting portion, and a controller. On the basis of a result of detection by the detecting portion when a voltage is applied to the inner roller so as to form a chart on a recording material of a predetermined kind in an operation in an adjusting mode, the controller determines whether a transfer voltage when a toner image is transferred onto the recording material of the predetermined kind is subjected to constant-voltage control so that the voltage applied to the inner roller by the power source becomes a target value or is subjected to constant-current control so that a current supplied to the inner roller becomes a target value.

An image forming apparatus includes a high voltage generating circuit, a voltage controller, a current detector, and a recovery process controller. If two inflection points (O and P) exist, which exist on a characteristic curve indicating a relationship between the voltage value and the current value when the frequency of the AC voltage is set as a first frequency or when a photosensitive drum is rotated at a first linear speed, the recovery process is performed if a potential difference between a first inter-inflection-point voltage (OP) between inflection points and a second inter-inflection-point voltage (OP) between inflection points (O and P) when setting a second frequency different from the first frequency, or a potential difference between the first voltage and a third inter-inflection-point voltage (OP) between inflection points (O and P) when setting a second linear speed different from the first linear speed becomes a predetermined value or less.

After a predetermined period elapses since the start of use of a photosensitive member, if a calculated value calculated from a detection current between a charging unit and a photosensitive member is out of a predetermined range, a determining unit does not perform determination using a currently calculated value and, if the calculated value is within the predetermined range, the determining unit performs determination using the currently calculated value.