Abstract: A developing device for an image forming apparatus capable of collecting a developer left on an image carrier with a so-called cleanerless process is disclosed. A ratio of a distance between the image carrier and a developer carrier at the boundary of a nip to a development gap at the center of the nip is selected to be 1.5 or less. This obviates the omission of the trailing edge of an image and granularity and enhances faithful reproduction of horizontal lines and dots despite the use of the cleanerless process.

Abstract: An image forming apparatus develops a latent image formed on an image carrier with a developer that forms a magnet brush on a developer carrier. The developer carrier is made up of a sleeve and a stationary magnet roller accommodated in the sleeve. The magnet roller includes a main pole for causing the developer to form the magnet brush and auxiliary poles for helping the main pole exert a magnetic force. An electric field including an oscillation component is formed between the image carrier and the developer carrier. A particular ratio is set up between a distance between the image carrier and the developer carrier, as measured at the boundary of a nip, and the shortest distance between them, between the above shortest distance and the shortest distance between the developer carrier and a metering member, or between the shortest distance between the image carrier and the developer carrier and the amount of developer scooped up to the image carrier.

Abstract: An image forming apparatus including a rotatable image supporter having photoconductive properties, an optical image irradiating device configured to irradiate the image supporter with a light beam to form an electrostatic latent image thereon, and a developing device including a developer, which includes a magnetic carrier and a toner, and a developer supporter which bears the developer on the surface thereof and configured to feed the developer to a developing area between the image supporter and the developer supporter to develop the electrostatic latent image, wherein a ratio of a toner content in a first portion of the developer in the developing area relatively close to the surface of the image supporter to a toner content in a second portion of the developer in the developing area relatively close to the surface of the developer supporter is not less than about 0.6, measured when the developer contacts a continuous non-image area formed on the image supporter.

Abstract: In an image forming apparatus, a developing unit for forming an image by use of a two-ingredient type developer, i.e., toner and carrier mixture, includes a container for replenishing fresh toner and for replacing carrier deteriorated due to aging or a developer including such carrier. The developer in the developing unit will be collected based on the number of times that a part of the developer has been replenished.

Abstract: An image forming apparatus including, an image bearing member capable of having a latent image formed thereon, and a developer bearing member that bears a developer comprising a toner and a carrier, wherein a latent image formed on the image bearing member is developed by a non-contacting method under application of a vibrating electric field, so that the toner is transferred from the developer bearing member toward the image bearing member, and wherein the following relation holds:1.0.times.10.sup.-4 <t.sub.1.sup.2 /L.sub.T <1.0.times.10.sup.-3 (sec.sup.2 /m),where t.sub.1 represents a phase period during which a toner particle of the toner is transferred from the toner bearing member to the latent image during application of the vibrating electric field and L.sub.T represents a weight average particle diameter of the toner particles.

Abstract: An image forming apparatus includes an image support which supports an electrostatic latent image on a surface of the image support. A developing unit has a developing agent support which retains a developing agent, including a toner and carriers, contained in the developing unit. The developing unit converts the latent image on the image support into a toner image by causing the toner to adhere to the surface of the image support. A developing bias supplying unit supplies a developing bias voltage to the developing agent support of the developing unit, the developing bias voltage being one of a DC bias voltage and an AC bias voltage. A timer measures a non-driven period of the developing agent in the developing unit.

Abstract: An image forming apparatus of the present invention is capable of forming an oscillation electric field in a developing region on the basis of the particle size of toner and the particle size of magnetic carrier. Assume that the oscillation electric field includes a phase for causing the toner to move toward a latent image and having a duration t.sub.1, that the electric field has a period T, that the toner has a weight-average particle size of L.sub.t, and that the carrier has a weight-average particle size of L.sub.c. Then, there hold a relation of 1.0.times.10.sup.-4 <t.sub.1.sup.2 /L.sub.t <1.0.times.10.sup.-3 ?sec.sup.2 /m! and a relation of T.sup.2 /L.sub.c <0.005 ?sec.sup.2 /m!. The apparatus insures images with uniform dots and including a minimum of noise.

Abstract: In an image forming apparatus, a developing unit for forming an image by use of a two-ingredient type developer, i.e., toner and carrier mixture includes a container for replenishing fresh toner and for replacing carrier deteriorated due to aging or a developer including such carrier. By rotating the container in one direction, both fresh toner and a two-ingredient developer can be supplied to the developing unit. Initially when a container is mounted, the developer is fed in an amount less than an amount for image formation to start and only when a second container is mounted and rotated is the developer amount sufficient for image formation to start.

Abstract: An image forming apparatus includes a cleaning member for collecting toner left on an image carrier after image transfer, and then redepositing it on the carrier, so that a developing unit can collect the redeposited toner to reuse it. Even when the frictional charging ability of the cleaning member falls due to aging or varying environment, the charge of the toner left on the image carrier is regulated to preselected polarity before the toner reaches the cleaning member, thereby enhancing a toner collecting efficiency and a toner redepositing efficiency. The charge of the toner redeposited on the image carrier and moved away from the cleaning member is regulated to preselected polarity while being increased, thereby reducing a load to act on the developing unit. The toner is redeposited on the image carrier efficiently without regard to the polarity of the toner collected by the cleaning member.

Abstract: In an image forming apparatus, a toner collection mode is executed when a series of image formation modes ends and when the image formation mode is continuously repeated a preselected number of times. A toner image sensing mode for sensing a reflection density from a reference toner image is executed every time the image formation mode is repeated a preselected number of times. The apparatus is capable of surely and efficiently removing toner left on an image carrier after image transfer, and collecting the reference toner image with a developing unit. The reference toner image is prevented from contaminating an image transferring unit and a cleaning unit.

Abstract: In an image forming apparatus, during the course of recording, a cleaning roller is rotated together with an image carrier. The roller frictionally charges toner left on the image carrier after image transfer to the same polarity. A cleaning member electrostatically collects the charged toner. At the same time, a voltage is applied to the cleaning member by a voltage applying device in order to cause it to attract the charged toner, thereby cleaning the image carrier. Hence, even when the toner remaining on image carrier is charged partly to the positive polarity and partly to the negative polarity, the toner can be entirely transferred to the cleaning member by a simple construction.

Abstract: In a method and an apparatus for discriminating real securities from copies thereof produced by an electrophotographic copier using a toner, a heating member heated to a temperature above 50.degree. C. and below 250.degree. C. is brought into contact with a printing to see if an image on the printing changes or if any deposit is present on the heating member. Whether or not the image of the printing is formed by a toner whose major component is a thermoplastic resin, is determined on the basis of the result of the above decision.

Abstract: An image forming apparatus capable of readily changing the pixel density of an image to be formed on an image carrier and, therefore, stabilizing image reproduction. To change the pixel density, the apparatus turns on, among light emitting elements arranged in a higher density than input image data, a plurality of light emitting elements per pixel or by changing the number of light emitting elements per pixel and the turn-on time thereof.

Abstract: An image recording apparatus for electrostatically forming a latent image on an image carrier by driving optics in response to multi-level image data. Before the start of an actual image recording operation, a latent image in the form of a test pattern having a plurality of tones is formed on the image carrier by pulse width modulation. A table for correcting image data is generated on the basis of sensed surface potentials of the test pattern. A semiconductor laser included in the optics is driven such that the tone data and the latent image potential remains in a constant relation.

Abstract: A color image forming apparatus including a color image reader for optically scanning a document to produce blue, green, and red color separated information, a processor for processing the color separating information supplied by the reader and generating black, yellow, magenta, and cyan color information signals, a rotatable image retainer, and two latent image forming devices for forming latent images at a common region on the image retainer in accordance with the color information signals corresponding to two recording colors. The first latent image is formed by one of the latent image forming devices in synchronization with the scanning of the color image recorder to form a first latent image at a first writing position. The second latent image forming device is delayed to form the second latent image at a second writing position. The delay device compensates for the time necessary for the common region on the image retainer to travel between the first and second writing positions.

Abstract: A multicolor image forming method includes a first step of optically scanning and color separating an original so as to obtain first image signals corresponding to R, G and B multicolor components, a second step of parallelly inputting the first image signals as address signals to a reference memory storing at least one reference table representative of at least two different types of color correction for converting the first image signals into second image signals corresponding to at least Y, M and C multicolor components, a third step of selecting second image signals corresponding to one color component from the second image signals corresponding to the multicolor components output from the reference memory, a fourth step of providing a latent image made by image exposure onto a moveable image carrier having a photoconductive property based on the second image signals corresponding to the color component selected in the third step, a fifth step of developing the latent image formed on the image carrier in

Abstract: A color image forming apparatus wherein an image retainer and a transfer member are arranged unitarily in a process cartridge, the process cartridge being formed so that it can be inserted into and withdrawn from an apparatus body having a pluralilty of developing devices. The process cartridge has a cleaning device and a transfer member, and the apparatus body has a device for recovering waste toner. The waste toner scraped off from a surface of the image retainer by the cleaning device is recovered into a hollow in the transfer member.

Abstract: The invention provides a color image forming apparatus provided with an image carrying unit including a rotatable photoreceptor, a developing unit including a plurality of developing devices, and a cleaning unit. The apparatus is formed with a lower casing and an upper casing. In the upper casing, the image carrying unit, the developing unit and the cleaning unit are accommodated, in which at least two kinds of the units are incorporated in a cartridge capable of being detachably installed in the upper casing. The upper casing is adapted pivotal between an open position and an operation position around an axis which is disposed parallel to the rotation axis of the photoreceptor. When the upper casing is pivotted to the open position, the developing unit is so disposed that a side of the developing unit facing the photoreceptor becomes higher than other side of the developing unit.

Abstract: A method of reproducing multiplex images wherein an electrostatic image is formed on an image retainer by using a common electrostatic image forming device, the electrostatic image formed on the image retainer is developed, the steps of the above are repeated to superpose a plurality of toner images on the image retainer, and the toner images is transferred on a recording paper by one step. The developings other than the first time developing are carried out in such a manner that the surface of a developer layer on a developer feeding carrier does not contact with the surface of the toner image on the image retainer.

Abstract: A method of reproducing multiplex images wherein an electrostatic image is formed on an image retainer by using a common electrostatic image forming device, the electrostatic image formed on the image retainer is developed, the steps of the above are repeated to superpose a plurality of toner images on the image retainer, and the toner images is transferred on a recording paper by one step. The developings other than the first time developing are carried out in such a manner that the surface of a developer layer on a developer feeding carrier does not contact with the surface of the toner image on the image retainer.