Abstract: An image forming apparatus includes an image bearing member and a developer bearing member. A first period is from when rotational drive of the developer bearing member is started until increased to a speed at which the image forming apparatus performs image forming. A first absolute value of a difference between a developer bearing member surface potential Vdc and an image bearing member surface potential Vd, as determined when the image bearing member is facing the developer bearing member, is obtained during the first period. The value |Vdc?Vd| obtained during the first period is smaller than the value |Vdc?Vd| obtained after the first period. During the first period, the image bearing member surface potential Vd at the facing position is a first potential and, after the first period, the image bearing member surface potential Vd at the facing position becomes a second potential different from the first potential.

Abstract: An image forming apparatus includes a rotatable intermediate transfer member; a first image forming portion having a first photosensitive member which rotates, a first developing unit, and a first charge eliminating unit; a second image forming portion that is located on a downstream side of the first image forming portion in a rotational direction of the intermediate transfer member, and that has a second photosensitive member which rotates, a second developing unit, and a second charge eliminating unit; a transfer unit; and a switching unit that switches a light amount of the second charge eliminating unit when a usage amount of the second image forming portion reaches a predetermined amount to a value that is greater than a light amount of the first charge eliminating unit when a usage amount of the first image forming portion reaches the predetermined amount.

Abstract: An image forming apparatus includes a photosensitive member, a first charging roller, a first cleaning member, a second charging roller, and a second cleaning member. The following relationship is satisfied: (X×L0+L1+L2)?(Y×L3+L4)?0 where L0 represents a length of a whole circumference of the first charging roller, L1 represents a length between a first contact area and a first contact position of the first charging roller and the photosensitive member, L3 represents a length of a whole circumference of the second charging roller, L4 represents a length between a second contact area and a second contact position, L2 represents a length between the first contact position and the second contact position, X represents an integer in a range of 0?X?40, and Y represents an integer in a range of 0?Y?40.

Abstract: An image forming apparatus has a changing portion configured to change, based on a detection result of a temperature sensor, response sensitivity in starting of power supply by a determination portion based on a detection result of a human body detection sensor in a case where a human body approaches the human body detection sensor. The changing portion increases the sensitivity in a case where a temperature detected by the temperature sensor is a second temperature lower than a first temperature than in a case where the temperature detected by the temperature sensor is the first temperature.

Abstract: An image forming apparatus includes a photosensitive member, a first charging roller, a first cleaning member, a second charging roller, and a second cleaning member. The relationship is satisfied (X×L0+L1+L2)?(Y×L3+L4)?0 where L0 represents a length of a whole circumference of the first charging roller, L1 represents a length between the first contact area and the first contact position of the first charging roller and the photosensitive member, L3 represents a length of a whole circumference of the second charging roller, L4 represents a length between the second contact area and the second contact position, L2 represents a length between the first contact position and the second contact position, X represents an integer in a range of 0?X?40, and Y represents an integer in a range of 0?Y?40.

Abstract: An image forming apparatus includes: a rotatable intermediate transfer member; a first image forming portion having a first photosensitive member which rotates, a first developing unit, and a first charge eliminating unit; a second image forming portion that is located on a downstream side relative to the first image forming portion in a rotational direction of the intermediate transfer member, and that has a second photosensitive member which rotates, a second developing unit, and a second charge eliminating unit; a transfer unit; and a switching unit that switches a light amount of the second charge eliminating unit when a usage amount of the second image forming portion reaches a predetermined amount to a value that is greater than a light amount of the first charge eliminating unit when a usage amount of the first image forming portion reaches the predetermined amount.

Abstract: An image forming apparatus has a changing portion configured to change, based on a detection result of a temperature sensor, response sensitivity in starting of power supply by a determination portion based on a detection result of a human body detection sensor in a case where a human body approaches the human body detection sensor. The changing portion increases the sensitivity in a case where a temperature detected by the temperature sensor is a second temperature lower than a first temperature than in a case where the temperature detected by the temperature sensor is the first temperature.

Abstract: An image forming apparatus including a rotatable photosensitive member, a first charging member for electrically charging the photosensitive member at a first charging portion by applying thereto a first DC voltage, and a second charging member, provided downstream of the first charging portion with respect to a rotational direction of the photosensitive member, for electrically charging the photosensitive member charged by the first charging member, at a second charging portion by applying thereto an oscillating voltage in the form of a second DC voltage superposed with an AC voltage.

Abstract: A high-density area of a low-reflectance patch image is accurately detected. There is an image forming apparatus that detects the density of a patch image by radiating light from a laser oscillator 701 and receiving reflected light reflected off the patch image using a line sensor 704. The density of a black patch image 720 having a low reflectance is detected from the difference between the position at which reflected light from a yellow patch image 710 is received and the position at which reflected light from a superimposed toner image that is transferred in such a manner that the yellow patch image 730 is superimposed on the top of the black patch image 720 is received.

Abstract: A toner image height measurement apparatus capable of accurately measuring heights of toner images of respective colors with a relatively simple construction and without being affected by toner colors. With motion of an image carrier, there occurs a change in reflection light amount detected by a photodiode of the height measurement apparatus in timing when laser light having been irradiated onto the image carrier starts to be irradiated onto or intercepted by a toner image and in timing when the laser light having been irradiated onto the toner image starts to be irradiated onto the image carrier. Based on a principle that these timings vary according to a toner image height, the height measurement apparatus detects the timing when the reflection light amount changes by a predetermined amount, thereby detecting the toner image height.

Abstract: An image forming apparatus includes a image bearing member (drum); a developing device; a first charging member; a second charging member provided downstream of the first charging member and upstream of the developing device with respect to a rotational direction of the drum; a first power source for applying a DC voltage to the first charging member; a second power source for applying an oscillating voltage, in the form of a DC voltage biased with an AC voltage, to the second charging member; a detecting device for detecting a DC current passing through the second charging member; and a controller for controlling, when the oscillating voltage is applied to the second charging member while the DC voltage is applied to the first charging member, the DC voltage applied to the first charging member so that the detected DC current falls within a predetermined range including zero.

Abstract: A high-density area of a low-reflectance patch image is accurately detected. There is an image forming apparatus that detects the density of a patch image by radiating light from a laser oscillator 701 and receiving reflected light reflected off the patch image using a line sensor 704. The density of a black patch image 720 having a low reflectance is detected from the difference between the position at which reflected light from a yellow patch image 710 is received and the position at which reflected light from a superimposed toner image that is transferred in such a manner that the yellow patch image 730 is superimposed on the top of the black patch image 720 is received.

Abstract: A toner image height measurement apparatus capable of accurately measuring heights of toner images of respective colors with a relatively simple construction and without being affected by toner colors. With motion of an image carrier, there occurs a change in reflection light amount detected by a photodiode of the height measurement apparatus in timing when laser light having been irradiated onto the image carrier starts to be irradiated onto or intercepted by a toner image and in timing when the laser light having been irradiated onto the toner image starts to be irradiated onto the image carrier. Based on a principle that these timings vary according to a toner image height, the height measurement apparatus detects the timing when the reflection light amount changes by a predetermined amount, thereby detecting the toner image height.