An image forming apparatus includes an apparatus main body, a conductive member, a contact spring, a hollow cylinder, and a drum unit attachable to and detachable from the apparatus main body. The conductive member is disposed in the drum unit. The contact spring is disposed in the apparatus main body and comes in electrically conductive contact with the conductive member. The hollow cylinder is disposed in the apparatus main body. The contact spring has a contact part and a helical spring part. The contact part is provided on the helical spring part. The contact part is retractable in and out of the hollow cylinder. The helical spring part is contained in the hollow cylinder and urges the contact part in a direction for causing the contact part to protrude from the hollow cylinder. The contact part has a longitudinal shape elongated along an axis of the helical spring part.

An image forming apparatus includes a photoconductor, a charger that charges the photoconductor, a transfer unit that transfers a toner image formed on the photoconductor to a transfer device, a charging power supply that outputs AC voltage for applying a charging bias to the charger, a transfer power supply that outputs DC voltage or DC current for applying a transfer bias to the transfer unit, an output detector that detects an output value of the DC voltage or the DC current, and a controller that calculates load impedance of the photoconductor based on the detected output value of the DC voltage or DC current detected by the output detector while modifying the output of the AC voltage by the charging power supply and sets the output of the AC voltage that the load impedance starts converging into a predetermined value as an adjusted AC output to the charging power supply.

A power supply device includes a rectification circuit that is supplied with AC power from an AC power supply, a power factor improvement circuit that boosts an output voltage of the rectification circuit, smooths a boosted voltage with a capacitor, and thereby generates a DC output voltage outputted to a load circuit, a DC-DC converter that steps down the DC output voltage to a prescribed first voltage, a DC output voltage detection circuit that detects whether or not the DC output voltage satisfies a prescribed condition, and a switch circuit that temporarily puts the power factor improvement circuit in an operating state by use of the first voltage each time the prescribed condition is satisfied in a period in which the power factor improvement circuit is in a stopped state due to an energy saving mode of the load circuit.

An image forming apparatus includes a photosensitive member, a charging member configured to charge a surface of the photosensitive member, a power supply configured to apply the DC voltage to the charging member, a current detection unit configured to detect a current value flowing from the charging member to the photosensitive member, a calculation unit configured to calculate a first voltage value based on applied voltages with different voltage values and detected current values, a setting unit configured to set a second voltage value to be applied to the charging member during forming of the image. The setting unit sets the second voltage by adding the first voltage value, a target voltage value, and a correction value corresponding to a peripheral speed of the photosensitive member during forming of the image.

A control circuit of an image forming apparatus outputs a pulse signal. A clock signal generation circuit generates a clock signal, based on the pulse signal. A pulse signal conversion circuit generates a pulse conversion control signal of a voltage value associated with a duty ratio of the pulse signal. An AC voltage generation circuit generates an AC voltage of a frequency based on the clock signal. Either the AC voltage generation circuit or a DC voltage generation circuit generates a voltage whose amplitude or voltage value increases as a voltage value of the received pulse conversion control signal increases, and whose amplitude or voltage value decreases as a voltage value of the pulse conversion control signal decreases.

An image forming apparatus according to this disclosure includes: a charging roller that charges a surface of a photoconductor drum; a development unit that forms a toner image on the surface of the photoconductor drum; an image density sensor that detects density of the formed toner image; a charge power supply that applies a bias voltage to the charging roller; a development power supply that applies a bias voltage to the development unit; and a controller. The controller causes the charge and development power supplies to output respective predetermined bias voltages for predetermined time, and is capable of executing a contact and separation determination mode in which a contact and separation state of the charging roller is determined based on whether or not an image is detected by the image density sensor after output of the respective bias voltages.

An image forming apparatus includes a photosensitive member, a charging member configured to charge a surface of the photosensitive member, a power supply configured to apply the DC voltage to the charging member, a current detection unit configured to detect a current value flowing from the charging member to the photosensitive member, a calculation unit configured to calculate a first voltage value based on applied voltages with different voltage values and detected current values, and a setting unit configured to set a second voltage value to be applied to the charging member during forming of an image. The setting unit sets the second voltage value by adding the first voltage value, a target voltage value, and a correction value corresponding to a peripheral speed of the photosensitive member during forming of the image.

An image forming apparatus executes processing for calculating a complex number of a discharge current waveform which is a discharge current component of a current waveform in discharge based on a first complex number at an analyzing frequency near a charging frequency of a current waveform in non-discharge, a second complex number at the analyzing frequency of the current waveform in non-discharge, a third complex number at an analyzing frequency of the current waveform in discharge, and a fourth complex number at the analyzing frequency of the current waveform in discharge, and then for determining an AC voltage value of a charging voltage during image formation based on a calculation result of the complex number of the discharge current waveform. The controller controls a power supply portion to apply, to the charging member, the charging voltage including an AC voltage component with the determined value.

An image forming apparatus includes an image bearing member, a belt, a contact member, a rotation shaft member, a cam, an opposing member, and a damper. The belt receives a toner image from the image bearing member. The cam rotates in tandem with the rotation shaft member and contacts or separates the contact member and the belt. The opposing member is disposed to face the rotation shaft member in a direction intersecting with a rotation shaft member shaft direction. The damper member has a first flexible portion and a second flexible portion that are elastically deformable by contacting with the opposing member. In either contact operation or separation operation of the contact member to/from the belt, the damper member rotates in tandem with rotation of the rotation shaft member so that both the first flexible portion and the second flexible portion contact with the opposing member and are elastically deformed.

An image forming apparatus includes a print engine including a photosensitive drum forming an image on an image forming medium, a charging member charging the photosensitive drum, a power supply to provide a charging power supply having a reference charging voltage to the charging member, a sensor to detect an image density of an image formed on the image forming medium, and a processor to control the power supply to change a magnitude of voltage of the charging power supply within a predetermined voltage range at predetermined periods, and to identify an occurrence of a background with respect to the photosensitive drum based on an image density detected by the sensor while the charging power supply is changed.