Abstract: In a vertical type developing device in which plurality of screws are arranged up and down, developer transported by an upper developer transporting screw and developer transported by lower developer transporting screw are properly dispersed. Thereby, developer flows smoothly and further stirs and mixes. As means of it, the followings are included: (1) between the upper screw and the lower screw, properly adjusting developer transporting capabilities and dispersing pressures; (2) arrangement of dispersing members between the upper and lower developer transporting screws; (3) arrangement of openings at a partition wall; (4) arrangement of a developer reservoir portions to a developer accommodating unit; or the like.

Abstract: The present invention is to provide a developing apparatus having a supply screw and a recovery screw both of which are arranged vertically to circulate developer, wherein a component in a normal direction of pressure generated by the recovery screw is made larger than that of pressure generated by the supply screw. Thereby, lowering and raising of developer is suppressed and occurrence of fog on the image and the smoke of toner are prevented. Alternatively, a radial member and a centrifugal member are applied to the supply screw and the recovery screw, respectively. Thereby, developer is prevented from moving between screws in the midst of the transportation. Still alternatively, a preliminary stirring portion is provided on extension of a stirring screw at upperstream side. The preliminary stirring portion has a cylindrical body with inlets and outlets. Both inside and outside of the cylindrical body, screws are provided and inclines of screw blades are reversed to each other.

Abstract: A supply screw 10 and a collection screw 20 for a developing device equip with screw blades having different forms at particular sections so as to make conveying force of developer different depending on sections. Screw blades for big conveying force are attached within sections where developer distribution is dense while screw blades for small conveying force are attached within sections where developer distribution is sparse. In other words, conveying force is made to be greater at sparse-distribution section while smaller at dense-distribution section. Developer delivery is also promoted by providing different conveying force area within carry-up area where developer is carried up from a supply screw 10 to a collection screw 20 or vice versa. By making conveying force of each section different, developer is uniformly delivered to a developing roll 87 whether in width direction or in axial direction. Furthermore, developer circulation in a developing device becomes smooth.

Abstract: A developing device capable of preventing a reduction of image quality due to disparities in image density or fogging and the like that result from an nonuniform toner concentration or static charge status due to inadequate mixing of a developer. The developing device is provided with a mixing screw for mixing a developer separately from a supply screw for supplying a developer to a developing roller and a collection screw for collecting a developer from the developing roller, the transport direction of the mixing screw being opposite to the transport direction of the supply screw and collection screw.

Abstract: A developer transporting device for electrophotographic copiers has a pair of walls, a rotating shaft supported between the pair of walls, a first transporting member provided on the rotating shaft, a rotating cylindrical screw concentrically sheathing the rotating shaft and having a second transporting member provided on an exterior surface thereof and apertures provided at both ends thereof, an inflow pipe mounted on one wall of the pair of walls and extending into one end of the cylindrical screw and provided with a developer inflow opening facing an aperture of the cylindrical screw, and an outflow pipe mounted on the other wall of the pair of walls and extending into the other end of the cylindrical screw and provided with a developer outflow opening facing an aperture of the cylindrical screw.

Abstract: An image density control apparatus which includes a photoreceptor having a photosensitive surface to be uniformly charged to a reference potential and formed with a charge latent image by a reference light amount, a device for developing the charge latent image at a reference developing potential so as to obtain a test pattern, a device for detecting density of the test pattern so as to control image forming condition during an actual image formation according to the detected value. The image density control apparatus further includes a reference condition control device which sets the reference image forming condition for forming the test pattern in accordance with the image forming condition for forming a document which was previously set by detecting a representative density of the document.

Abstract: An image forming apparatus for forming images by an electrophotographic process. The image forming apparatus includes a humidity sensor for detecting the humidity in the area around the image forming members provided therein, a density sensor for detecting the density of images formed on a photoreceptor, and a humidity controller having a dehumidifying unit and a humidifying unit for adjusting the humidity in the area around image forming members. The humidity controller is operated according to humidity historical data generated based on the humidity data outputed from the humidity sensor, a detected photoreceptor potential, a detected amount of developer scattered from the developing unit or the detection result from the density sensor.

Abstract: An image forming apparatus having a developing device which accommodates a developer for developing an electrostatic latent image formed on the surface of a latent image carrier, a developing member provided in said developing device for supplying the developer to the electrostatic latent image formed on the surface of the latent image carrier and a mixing member provided in the developing device for mixing the developer accommodated within the developing device. In the above image forming apparatus, the operating time of the mixing member is determined prior to the start of operation of the developing member based on at least one value of a toner density at the end of developing, the developer standing idle time, and the total number of developing cycles with the same developer.

Abstract: A digital half-tone image is reproduced by exposing a photoconductor by modulating the intensity of laser beam. In order to correct the effect of the size of laser beam on the gradation characteristic, the surface potential of the photoconductor is detected under various conditions. The sensitizing potential and the sensitivity of the photoconductor are corrected according to the measured values for stabilizing the gradation potential. Then, the beam size is corrected according to the surface potential or the amount of adhered toners detected under prescribed conditions, without detecting the beam size.

Abstract: An image forming apparatus having a toner density detecting sensor, a humidity sensor and a memory for storing past record of detected humidity. The toner density is compensated by referring to the detected toner density, currently detected humidity and past record of humidity to maintain image density stability.

Abstract: In forming a digital image on the photoconductor wherein the intensity of the laser beam is modulated according to multi-level image data, a standard toner image is formed at an intermediate intensity at which the reproduced image density is not affected by the beam size, and the toner density is detected. On the other hand, the size of the beam for exposing the photoconductor is measured. Then, the gradation characteristic is controlled according to the toner density and the beam size. Thus, the effect of the beam size on the gradation characteristic is corrected.

Abstract: In an electrophotographic image forming apparatus, a charger sensitizes the photoconductor at a desired initial potential and the photoconductor is exposed to form an electrostatic latent image, which is developed by a developer to form a toner image. A gradation correction table on the relation of the input image signal to the exposure amount is provided in a memory, and it is amended by adding a common amendment value to the image density signal in the gradation correction table. The common amendment value is determined according to the density of a standard toner image. If a plurality of gradation correction tables are stored in a memory, one of them is selected according to the output voltage of the charger or the bias potential of the developer. The selected gradation correction table is amended according to the surface potential of the photoconductor, the temperature of the photoconductor or the humidity of the photoconductor.

Abstract: In an image forming apparatus with use of electrophotographic process, a plurality of toner images are formed on a photoconductor by changing stepwise a predetermined operating parameter such as light intensity of laser beam or the grid potential of sensitizing charger, and the densities of the toner images are measured. Thus, the value of the operating parameter is determined which corresponds with the smallest non-zero toner density among the measured densities. When an image is formed on the photoconductor, for example the gamma table is corrected according to the determined minimum light intensity.