Ricoh Company, Ltd.

Wataru Yasuda

Koji Sakamoto

Fuchio Kanno

Toshio Kaneko

Kazuo Kobayashi

Naomi Sugimoto

Kouji Ishigaki

Moriyuki Koike

Shinsuke Kikui

Masaki Tokuhashi

Hiromi Ogiyama

Takashi Bisaiji

Chikara Imai

Yoshihiro Abe

Ichiro Shimeki

A charging apparatus and method used in an image forming apparatus uses a charging apparatus to apply a charging potential to a photosensitive body, a voltage measuring device that measures the charging potential and outputs a measured charging potential signal, an environmental condition sensor which senses at least one environmental condition and outputs an environmental condition signal, and adjustable voltage application which applies an applied voltage to said charging member, and a controller, where the controller controls an amount of the applied voltage applied to the charging member in accordance with the charging potential signal and the environmental signal, where the applied voltage is adjusted to compensate for the sensed environmental condition.

Charging apparatus and method for use in image forming device

An image forming apparatus includes a charging member to be contacted with a rotating photosensitive body so as to charge the photosensitive body, a temperature detection device for detecting temperature of the charging member, and a voltage control device for controlling a voltage to be supplied to the charging member in accordance with a temperature value detected by the temperature detection device. The control device includes a detection temperature read device for reading the detection temperature value detected by the temperature detection device, a voltage calculation device for calculating a voltage to be supplied to the charging member based on the detection temperature value read by the detection temperature read device, and a maintenance device for maintaining a charging voltage as it is, which charging voltage is calculated last time, when a difference between the detection temperature value currently read by the detection temperature read device and the detection temperature value which is read last time by the detection temperature read device has exceeded a preset temperature value.

Image forming apparatus with contact type charging member

An image density control method for an image forming apparatus of the type forming a latent image of a document image on a photoconductive element and developing the latent image by a toner to produce a toner image by an electrophotographic procedure. A background pattern whose density is substantially the same as the background density of a document, i.e., a light pattern is illuminated to electrostatically form a latent image thereof on the photoconductive element. The latent image is developed by the toner, and the density of the resultant toner image is optically sensed by an image density sensor. A change in background density due to contamination or an increase in background potential, for example, is detected. Based on the detected change in background density, a quantity of light for imagewise exposure or similar factor dictating the developing ability is corrected, i.e., it is controlled to the light side if the density has been shifted to the dark side. The detection of the background density and the control for correction are effected only when the charge retaining ability of the photoconductive element is stable.

Image density control method for an image forming apparatus

An image density control method for an image forming apparatus of the type forming a latent image of a document image on a photoconductive element and developing the latent image to form a toner image by an electrophotographic procedure. A background pattern is implemented as a light pattern having a low density and provided independently of a reference density pattern. The light pattern is illuminated to form a latent image thereof on the photoconductive element, and the latent image is developed by a toner. The density of the resultant toner image is sensed by an image density sensor. Such a procedure allows a change in background density ascribable to contamination, increase in background potential and so forth to be detected. The light pattern may be replaced with a leading edge portion of a document if the leading edge portion has a density corresponding to the background density. Then, the latent image of the background pattern will be formed under exactly the same conditions as the latent image of an ordinary image, i.e., without any limitations as to the position of the pattern.

A developing device for developing an electrostatic latent image formed on an image bearing member such as a photosensitive member for use in an electrophotographic copying machine and the like using magnetic toner particles includes a rotatable sleeve, a magnet roll disposed inside of the sleeve and a doctor blade pressed against the sleeve for charging and forming a thin film of toner particles to be used in developing the latent image. In one form, the blade is provided movably in parallel with the rotating axis of the sleeve. In another form, an electrically conductive brush is provided to remove residual charges from the sleeve after each developing operation. In a further form, the tip end of the blade is disposed between the two adjacent magnetic poles of the magnet roll. In a still further form, the blade is constructed to have a two-part structure.

Developing device

A device for developing an electrostatic latent image formed on a photosensitive member includes a composite sleeve which is comprised of a cylindrical support, a dielectric layer formed on the support and a plurality of fine magnets serving as floating electrodes embedded in the dielectric layer and which is driven to rotate to carry magnetic toner as magnetically attracted to its outer peripheral surface.

A device is provided for developing an electrostatic latent image formed on an image bearing member with a developer comprised of magnetically attractable, electrically insulating toner particles for developing the latent image by applying the toner particles in the form of a thin film uniform in charge and thickness. The developing device generally comprises a developing sleeve, which is driven to rotate to carry thereon toner particles, and a pressure plate is held in pressure contact with the sleeve to thereby form a thin film of charged toner particles on the sleeve upstream of the developing station. In one aspect of the present invention, the pressure plate has a low hardness or relatively easily wearable region which is in pressure contact with the sleeve so as to prevent toner particles from permanently sticking to the pressure plate. In another aspect, the pressure plate is structured to have a locally defined relatively easily deflectable region which is in pressure contact with the sleeve. In a further aspect, the pressure plate is movable with respect to the sleeve to thereby remove stuck toner particles from the pressure plate and from the sleeve. In a still further aspect, a separator strip is provided, interposed between the pressure plate and the sleeve, which also keeps toner particles from sticking to the pressure plate. In a still further aspect, a cleaner is provided for cleaning the pressure plate periodically or continuously in order to keep toner particles from sticking to the pressure plate and to allow a thin film of uniformly charged toner particles to be formed on the sleeve for use in developing the latent image at the developing station.

Developing device with regulated developer supply

A device for developing an electrostatic latent image formed on a photosensitive member includes a developing sleeve which is driven to rotate in a predetermined direction and a pressure blade which is kept pressed against the sleeve to form a thin film of uniformly charged toner so as to apply for the latent image for development. In accordance with the present invention, the forward end portion of the pressure blade is specifically shaped such that a projection having the width which substantially corresponds to the width of an image forming area of the photosensitive member is provided to extend beyond a contact line between the sleeve and the blade thereby allowing to form the thin film of toner whose width substantially corresponds to the image forming area of the photosensitive member, thereby preventing the waste of toner from occurring.

A developing device includes a developing sleeve driven to rotate to transport a film of developer riding on its outer peripheral surface, the developing sleeve including an electrically conductive cylinder, a dielectric layer formed on the cylinder and a plurality of fine electrodes provided electrically isolated from each other at least at the outer peripheral surface of the dielectric layer. In one form, each of the fine electrodes is previously coated with an insulating material having the volume resistivity of 10.sup.12 ohms-cm or more to a thickness of 0.5 microns to 0.5 mm. An intermediate dielectric layer may be provided between the cylinder and the first dielectric layer. Further, an electrically conductive layer may be provided as sandwiched between the two dielectric layers. Moreover, the outermost surface of the sleeve may be appropriately roughened in view of the average diameter of toner particles used.

Developing device having dispersed floating electrodes in a dielectric

A device for developing an electrostatic latent image formed on an imaging surface by applying a thin film of uniformly charged magnetic toner includes a sleeve which is driven to rotate at constant speed in an intended direction, a hopper for supplying toner to said sleeve, a pressure blade pressed against the sleeve to form the thin film of charged toner on the sleeve and a discharging scraper provided with a plurality of holes and disposed in contact with the sleeve at a location downstream of the developing region, whereby remaining toner on the sleeve is scraped off the sleeve and returned to the sleeve after passing through the holes, to thereby have the charge remaining on the sleeve removed by the discharging scraper.

Voltage-controlled developing device

A device for forming a toner film for use in developing an electrostatic latent image on an image bearing member, such as photosensitive member, is provided. A developing sleeve is rotatably provided and a magnet roll is also rotatably provided inside of the sleeve for magnetically attracting a blade of magnetic material to the outer peripheral surface of the sleeve thereby causing the toner carried on the sleeve to be formed into a film of desired thickness and charge. The magnet roll is formed with a plurality of magnetic poles elongated axially and arranged along the periphery of the roll in alternating polarities. Thus, the magnetic attractive force applied by the magnet roll to the blade changes periodically. In the present invention, the frequency of alternating magnetic field applied to the blade is set to be larger than the first order resonant frequency of the blade, thereby allowing to maintain the applied magnetic force as constant as possible.

Growing community of inventors

Yokohama, Japan

Wataru Yasuda