Abstract: A color image forming apparatus capable of superposing toner images of respective colors in accurate register by preventing an exposing position from being displaced in the subscanning direction. The rotation phase of a polygonal mirror is controlled on the basis of the mark detection timing of a mark sensor. Hence, the exposing position in the subscanning direction is prevented from being displaced without regard to irregularities in the circumferential length and feed speed of an intermediate image transfer belt.

Abstract: A color printer for forming color toner images on a sheet of paper includes a photoconductive belt for bearing an electrostatic latent image thereon, a plurality of developing devices, and an intermediate transfer belt for forming composite toner images thereon. The intermediate transfer belt and the developing devices face each other across the photoconductive belt. The color printer further includes a front frame which is provided adjacent the intermediate transfer medium, a paper feed device which is provided in a lower position of the apparatus, and a paper output tray which is provided in a upper position of the apparatus. A paper transporting path between the paper feed device and the paper output tray is provided between the intermediate transfer belt and the front frame.

Abstract: A color printer including a photoconductive belt, a black developing unit which is located adjacent the photoconductive belt and a revolving type developing unit which is located adjacent the photoconductive belt and has a developing position on the photoconductive belt which is different from that of the black developing unit. The revolving type developing unit has a yellow developing device, a magenta developing device and a cyan developing device, each including a detachable toner cartridge by which yellow toner, magenta toner and cyan toner is replenished. The black developing unit is replaceable independent of the revolving type developing unit by being removably mounted on a removable frame on which the revolving type developing unit is mounted. Both developing units are removable from the color printer as a body by removal of the removable frame from the color printer.

Abstract: A color image forming apparatus is provided with an intermediate transfer belt to transfer thereupon an image of each of a plurality of colors carried on a photoconductive member, sequentially superposing one image on top of another, to form a full color image, and to further transfer the full color image to a copysheet. The intermediate transfer belt is passed over supporting rollers and a plurality of marks are printed on the intermediate transfer belt for indicating a position on the belt. A detector is provided for detecting the marks on the belt to generate a detect signal to start an image forming operation for each of the colors. The detector is controlled to start detection of a mark when a predetermined length of time is elapsed after a start or a termination of an operation of a driving element of the apparatus. The detector is provided at a position facing one of the support rollers around which the intermediate transfer belt is passed.

Abstract: In a paper conveyer of an image forming apparatus, a transfer operation is performed by a transfer roller and an unfixed image in the transfer operation is carried onto the lower side of a transfer paper sheet. The transfer paper sheet is conveyed to a fixing device constructed by a fixing roller and a pressurizing roller. A hardness of the fixing roller is smaller than that of the pressurizing roller, while a nipping portion of the fixing and pressurizing rollers is formed in a concave shape. The fixing and pressurizing rollers are arranged such that a nipping inlet port point of the fixing and pressurizing rollers is located in the vicinity of a line of a conveying locus of a thin transfer paper sheet. A paper guide plate guides the transfer paper sheet to the nipping inlet port. In this construction, a transferred paper sheet is conveyed such that this transferred paper sheet is reliably fed into the nipping portion of the fixing device, and it is possible to prevent an image rub, wrinkles, a jam, etc.

Abstract: In an image forming apparatus, a developing device is disposed adjacent to a belt-like photosensitive member. A rotary type developing device has a hollow cylindrical casing rotatable around a shaft having a central portion for rotation. The developing device includes a casing which is rotated in a predetermined direction, and four partitions which divide the casing to make four developing units which extend radially outward from the shaft. A toner storing section or hopper is provided on one side of the developing device, i.e., on a front side of the image forming apparatus, and a toner cartridge is detachable from a top of the hopper, and the toner cartridge is exchanged when an end signal of the toner is detected by a sensor in the casing. The toner hopper is filled by new toner from the toner cartridge, and the toner is carried by conveyor members, which control an amount of the toner in the casing, and a supply roller supplies the toner to a developing roller.

Abstract: In an image forming apparatus of the type sequentially forming powder images of different colors on an image carrier, and sequentially transferring them to an acceptor one above the other (primary transfer), an image transfer method is disclosed which prevents transfer dust from being transferred to the acceptor at the time of the primary transfer. During the primary transfer, a bias potential V.sub.1 is applied to one of two conductors located at an upstream side. The potential V.sub.1 has the same polarity as the charged powder carried on the image carrier. A potential V.sub.2 is applied to the other conductor at a downstream side and provided with a polarity opposite to the polarity of the charged powder. Every time the primary transfer is repeated, the potentials V.sub.l and V.sub.2 are respectively sequentially shifted toward the polarity of the powder and toward the polarity opposite to the polarity of the powder.

Abstract: A color image forming apparatus of the type having a photoconductive belt for forming a latent image thereon electrostatically. The latent image is developed to turn out a corresponding toner image. The toner image is transferred from the photoconductive belt to an intermediate transfer belt. Such a procedure is repeated to form a composite color image on the intermediate belt. The color image is transferred from the intermediate belt to a recording medium. Any point on the intermediate belt in the direction of rotation and any points on drive rollers assigned to the two belts, respectively, in the direction of rotation are held in the same positional relation to a stationary member every time the intermediate belt completes one rotation.

Abstract: An electrophotographic color image forming apparatus is disclosed which allows a photoconductive element and an intermediate transfer belt, which are expendables, to be removed from the body thereof at the same time. This promotes easy replacement, inspection and so forth of expendables. The photoconductive element and intermediate transfer belt can be replaced substantially at the same period, reducing the frequency of replacement of expendables. A cartridge including the photoconductive element can be replaced with a minimum of component parts wasted, thereby enhancing the cost performance of the apparatus. Moreover, when a cover hinged to the body of the apparatus is opened, various units can be removed one after another, a unit around which the greatest space is available being first.

Abstract: An image forming apparatus having a developing device which includes a developing roller. A developer or a toner is transported on and along the developing roller without the roller being rotated. The developing roller has a shaft and ultrasonic transport members provided on the shaft. The ultrasonic transport members are made up of a plurality of electrodes, a piezoelectric member surrounding the electrodes and made of, for example, piezoelectric ceramic, and an elastic member surrounding the piezoelectric member and made of, for example, copper alloy or similar alloy. A plurality of standing waves are caused to flow through the electrodes with the result that the piezoelectric member waves. The toner is transported on the waving surface of the elastic member.

Abstract: A photoconductive element unit removably mounted in an electronic copier or like image-forming apparatus and having a single casing in which a photoconductive element, and a cleaning device made up of a cleaning means and a toner collecting container are accommodated. The cleaning device is removably mounted in the unit. The container is provided with an opening for producing toner which is collected in the container. Usually, a closure member is plugged in the opening to close it.