A developing device usable with an electrophotographic image forming apparatus, the apparatus including a driving shaft rotatable by a motor and having a rotating force applying portion, and a movable member, the developing device being mountable to the movable member, and the developing device being movable in a direction substantially perpendicular to an axial direction of the driving shaft in response to movement of the movable member in one direction with the developing device mounted to the movable member, the developing device includes i) a developing roller for developing an electrostatic latent image formed on an electrophotographic photosensitive drum, the developing roller being rotatable about an axis; and ii) a coupling member for transmitting a rotating force to the developing roller, the coupling member including, a rotating force receiving portion engageable with the rotating force applying portion to receive a rotating force from the driving shaft, and a rotating force transmitting portion for transmitting the rotating force received through the rotating force receiving portion to the developing roller, the coupling member being capable of taking a rotational force transmitting angular position for transmitting the rotational force for rotating the developing roller to the developing roller, a pre-engagement angular position which is taken before the coupling member is engaged with the rotating force applying portion and in which the coupling member is inclined away from the rotational force transmitting angular position, and a disengaging angular position which is taken for the coupling member to disengage from the driving shaft and in which the coupling member is inclined away from the rotational force transmitting angular position in a direction opposite to the pre-engagement angular position; wherein in response to a movement of the developing device when the movable member moves in the one direction, the coupling member moves from the pre-engagement angular position to the rotational force transmitting angular position to be opposed to the driving shaft, and wherein when the movable member makes a further movement in the one direction from a position where the coupling member is opposed to the driving shaft, in response to the further movement, the coupling member is disengaged from the driving shaft by moving from the rotational force transmitting angular position to the disengaging angular position.

A developing device usable with an electrophotographic image forming apparatus, the apparatus including a driving shaft rotatable by a motor and having a rotating force applying portion, and a movable member, the developing device being mountable to the movable member, and the developing device being movable in a direction substantially perpendicular to an axial direction of the driving shaft in response to movement of the movable member in one direction with the developing device mounted to the movable member, the developing device includes i) a developing roller for developing an electrostatic latent image formed on an electrophotographic photosensitive drum, the developing roller being rotatable about an axis; and ii) a coupling member for transmitting a rotating force to the developing roller, the coupling member including, a rotating force receiving portion engageable with the rotating force applying portion to receive a rotating force from the driving shaft, and a rotating force transmitting portion for transmitting the rotating force received through the rotating force receiving portion to the developing roller, the coupling member being capable of taking a rotational force transmitting angular position for transmitting the rotational force for rotating the developing roller to the developing roller, a pre-engagement angular position which is taken before the coupling member is engaged with the rotating force applying portion and in which the coupling member is inclined away from the rotational force transmitting angular position, and a disengaging angular position which is taken for the coupling member to disengage from the driving shaft and in which the coupling member is inclined away from the rotational force transmitting angular position in a direction opposite to the pre-engagement angular position; wherein in response to a movement of the developing device when the movable member moves in the one direction, the coupling member moves from the pre-engagement angular position to the rotational force transmitting angular position to be opposed to the driving shaft, and wherein when the movable member makes a further movement in the one direction from a position where the coupling member is opposed to the driving shaft, in response to the further movement, the coupling member is disengaged from the driving shaft by moving from the rotational force transmitting angular position to the disengaging angular position.

An image forming apparatus includes a power supply board, a driver board, and an engine control board. The driver board includes a plurality of switching elements each configured to supply and shut off a power supply for each of a plurality of distributed power supply voltages supplied from the power supply board. The plurality of switching elements includes a first switching element, to which the power supply voltage is to be applied from the power supply board, and a second switching element, to which the power supply voltage output from the first switching element is to be applied in a distributed manner. The engine control board is configured to performs failure diagnosis of the first switching element when the image forming apparatus is activated, and performs failure diagnosis of the second switching element in a case where an abnormality has occurred in any one of a plurality of loads.

An image forming apparatus includes an image bearing member 7, a transfer roller 8, an electric energy supply member 9, a voltage source E2, a detecting means 32 a controlling means 50 for adjusting a transfer voltage. A circumferential length 2K of the transfer roller, and a distance k measured along an outer periphery of the transfer roller from the electric energy supplying portion to the transfer portion satisfy 0.8Kk1.2K. The controller controls the voltage source so as to satisfy 0.7Tt1.3T, where 2T is time required for one full rotation of the transfer roller, and t is time during which the voltage source supplies in the test current or the test voltage per one level in the operation of the setting mode.

A developing device usable with an electrophotographic image forming apparatus, the apparatus including a driving shaft rotatable by a motor and having a rotating force applying portion, and a movable member, the developing device being mountable to the movable member, and the developing device being movable in a direction substantially perpendicular to an axial direction of the driving shaft in response to movement of the movable member in one direction with the developing device mounted to the movable member, the developing device includes i) a developing roller for developing an electrostatic latent image formed on an electrophotographic photosensitive drum, the developing roller being rotatable about an axis; and ii) a coupling member for transmitting a rotating force to the developing roller, the coupling member including, a rotating force receiving portion engageable with the rotating force applying portion to receive a rotating force from the driving shaft, and a rotating force transmitting portion for transmitting the rotating force received through the rotating force receiving portion to the developing roller, the coupling member being capable of taking a rotational force transmitting angular position for transmitting the rotational force for rotating the developing roller to the developing roller, a pre-engagement angular position which is taken before the coupling member is engaged with the rotating force applying portion and in which the coupling member is inclined away from the rotational force transmitting angular position, and a disengaging angular position which is taken for the coupling member to disengage from the driving shaft and in which the coupling member is inclined away from the rotational force transmitting angular position in a direction opposite to the pre-engagement angular position; wherein in response to a movement of the developing device when the movable member moves in the one direction, the coupling member moves from the pre-engagement angular position to the rotational force transmitting angular position to be opposed to the driving shaft, and wherein when the movable member makes a further movement in the one direction from a position where the coupling member is opposed to the driving shaft, in response to the further movement, the coupling member is disengaged from the driving shaft by moving from the rotational force transmitting angular position to the disengaging angular position.

An imaging device prints in color and monochromatically, such as black-only. It has a plurality of photoconductive drums, one each for black toner and at least one colored toner. The drums contact and rotate with an intermediate transfer member (ITM) to transfer images at a first transfer. During black-only imaging, the photoconductive drum for the black toner rotates with the ITM at process speed while the drum for the at least one colored toner rotates at less than process speed, often substantially less. The technique reduces consumption of colored toner during black-only imaging and minimizes charge build-up on the drum for the colored toner.

A developing device usable with an electrophotographic image forming apparatus, the apparatus including a driving shaft rotatable by a motor and having a rotating force applying portion, and a movable member, the developing device being mountable to the movable member, and the developing device being movable in a direction substantially perpendicular to an axial direction of the driving shaft in response to movement of the movable member in one direction with the developing device mounted to the movable member, the developing device includes i) a developing roller for developing an electrostatic latent image formed on an electrophotographic photosensitive drum, the developing roller being rotatable about an axis; and ii) a coupling member for transmitting a rotating force to the developing roller, the coupling member including, a rotating force receiving portion engageable with the rotating force applying portion to receive a rotating force from the driving shaft, and a rotating force transmitting portion for transmitting the rotating force received through the rotating force receiving portion to the developing roller, the coupling member being capable of taking a rotational force transmitting angular position for transmitting the rotational force for rotating the developing roller to the developing roller, a pre-engagement angular position which is taken before the coupling member is engaged with the rotating force applying portion and in which the coupling member is inclined away from the rotational force transmitting angular position, and a disengaging angular position which is taken for the coupling member to disengage from the driving shaft and in which the coupling member is inclined away from the rotational force transmitting angular position in a direction opposite to the pre-engagement angular position; wherein in response to a movement of the developing device when the movable member moves in the one direction, the coupling member moves from the pre-engagement angular position to the rotational force transmitting angular position to be opposed to the driving shaft, and wherein when the movable member makes a further movement in the one direction from a position where the coupling member is opposed to the driving shaft, in response to the further movement, the coupling member is disengaged from the driving shaft by moving from the rotational force transmitting angular position to the disengaging angular position.

A developing device usable with an electrophotographic image forming apparatus, the apparatus including a driving shaft rotatable by a motor and having a rotating force applying portion, and a movable member, the developing device being mountable to the movable member, and the developing device being movable in a direction substantially perpendicular to an axial direction of the driving shaft in response to movement of the movable member in one direction with the developing device mounted to the movable member, the developing device includes i) a developing roller for developing an electrostatic latent image formed on an electrophotographic photosensitive drum, the developing roller being rotatable about an axis; and ii) a coupling member for transmitting a rotating force to the developing roller, the coupling member including, a rotating force receiving portion engageable with the rotating force applying portion to receive a rotating force from the driving shaft, and a rotating force transmitting portion for transmitting the rotating force received through the rotating force receiving portion to the developing roller, the coupling member being capable of taking a rotational force transmitting angular position for transmitting the rotational force for rotating the developing roller to the developing roller, a pre-engagement angular position which is taken before the coupling member is engaged with the rotating force applying portion and in which the coupling member is inclined away from the rotational force transmitting angular position, and a disengaging angular position which is taken for the coupling member to disengage from the driving shaft and in which the coupling member is inclined away from the rotational force transmitting angular position in a direction opposite to the pre-engagement angular position; wherein in response to a movement of the developing device when the movable member moves in the one direction, the coupling member moves from the pre-engagement angular position to the rotational force transmitting angular position to be opposed to the driving shaft, and wherein when the movable member makes a further movement in the one direction from a position where the coupling member is opposed to the driving shaft, in response to the further movement, the coupling member is disengaged from the driving shaft by moving from the rotational force transmitting angular position to the disengaging angular position.

A developing device usable with an electrophotographic image forming apparatus, the apparatus including a driving shaft rotatable by a motor and having a rotating force applying portion, and a movable member, the developing device being mountable to the movable member, and the developing device being movable in a direction substantially perpendicular to an axial direction of the driving shaft in response to movement of the movable member in one direction with the developing device mounted to the movable member, the developing device includes i) a developing roller for developing an electrostatic latent image formed on an electrophotographic photosensitive drum, the developing roller being rotatable about an axis; and ii) a coupling member for transmitting a rotating force to the developing roller, the coupling member including, a rotating force receiving portion engageable with the rotating force applying portion to receive a rotating force from the driving shaft, and a rotating force transmitting portion for transmitting the rotating force received through the rotating force receiving portion to the developing roller, the coupling member being capable of taking a rotational force transmitting angular position for transmitting the rotational force for rotating the developing roller to the developing roller, a pre-engagement angular position which is taken before the coupling member is engaged with the rotating force applying portion and in which the coupling member is inclined away from the rotational force transmitting angular position, and a disengaging angular position which is taken for the coupling member to disengage from the driving shaft and in which the coupling member is inclined away from the rotational force transmitting angular position in a direction opposite to the pre-engagement angular position; wherein in response to a movement of the developing device when the movable member moves in the one direction, the coupling member moves from the pre-engagement angular position to the rotational force transmitting angular position to be opposed to the driving shaft, and wherein when the movable member makes a further movement in the one direction from a position where the coupling member is opposed to the driving shaft, in response to the further movement, the coupling member is disengaged from the driving shaft by moving from the rotational force transmitting angular position to the disengaging angular position.

A developing device that is useable with an electrophotographic image forming apparatus includes a developing roller for developing an electrostatic latent image formed on an electrophotographic photosensitive drum. The developing device also includes a coupling member for transmitting a rotating force to the developing roller.