Abstract: In an image forming apparatus including a transfer and transport belt suspended between a plurality of rollers, an image forming section for forming a pattern image on the transfer and transport belt, and a pattern image detecting sensor for detecting the pattern image, the pattern image detecting sensor is disposed so as to detect the surface of a suspended segment, of the transfer and transport belt, suspended between the rollers, and a back surface contact member that is in contact with a back surface of a detection area where the pattern image detecting sensor detects the pattern image on the surface of the transfer and transport belt is provided so as to render the detection area flat and stable. This can provide an image forming apparatus incorporating a pattern image detecting means having a simple arrangement and a capability to surely detect the pattern image in a precise and stable manner.

Abstract: Developing devices are provided adjacent to a light sensitive element. An intermediate transfer drum is provided adjacent to the light sensitive elements. After exposure of the light sensitive element, a first color or third color image is formed on the light sensitive element. On the other hand, after exposure of the light sensitive element, a second color or fourth color image can be formed on the light sensitive element. The first color image is transferred from the transfer unit to the intermediate transfer drum at the first transfer portion, and the second color image is transferred from the transfer unit at the second transfer portion so as to be superimposed on the first color image. Similarly, the third color image is transferred so as to be superimposed on the second image and the fourth color image is transferred so as to be superimposed on the third color image to the intermediate transfer drum. Accordingly, the first to fourth color images are superimposed.

Abstract: A registration pattern data generating portion is configured of a pattern set data generator for rough order error estimation and a pattern set data generator for fine order error estimation. When an error is estimated, a pattern set for rough order error estimation is checked first so as to roughly determine the size of the error and then another pattern set for fine order error estimation is checked so as to finely determine the size of the error. Thus, checking the two types of pattern sets makes it possible to exactly recognize the error in rough and fine units, providing fast and exact error determination.

Abstract: In an image forming apparatus wherein a multiple number of image supports form developer images of different colors so that the developer images of different colors corresponding to the multiple number of image supports are superimposed to a recording medium to form an image, flywheels are set at the ends of the rotary shafts of multiple image supports corresponding to relatively highly visible colors while no flywheel or a flywheel having a different diameter or weight from that of the above is set for the image support corresponding to a less visible color so as to make the inertial condition different from that of the others.

Abstract: Photoreceptor drums for forming color images each have a gear as the drive transmission element at their central shafts. Each gear has an idle gear which in turn is coupled with a first motor via a timing belt. The photoreceptor drum for forming black monochrome images has a gear as the drive transmission element at its central shaft. This gear has an idle gear which is coupled with a second motor.

Abstract: The present invention is intended to reduce a f.theta. correction error by correcting an error of an object scanning speed which is produced because a reflecting point of a laser beam moves on a polygon mirror. In an inventive laser scanner, laser light emitted from a laser oscillator is condensed into a beam by a condenser lens at first. This laser beam is reflected by a polygon mirror rotated by a scanning section and is reflected again to a photoreceptor by a curved reflecting mirror. A curved profile of a reflecting plane of the curved reflecting mirror in the main scanning direction is formed so as to be asymmetrical on right and left bounding about a scanning center point. Thereby, variation of speed for scanning the curved reflecting mirror by the light reflected by the polygon mirror may be canceled by the curved reflecting mirror and a speed for scanning the object may be fixed almost at a predetermined speed.

Abstract: Developing devices are provided adjacent to a light sensitive element. An intermediate transfer drum is provided adjacent to the light sensitive elements. After exposure of the light sensitive element, a first color or third color image is formed on the light sensitive element. On the other hand, after exposure of the light sensitive element, a second color or fourth color image can be formed on the light sensitive element. The first color image is transferred from the transfer unit to the intermediate transfer drum at the first transfer portion, and the second color image is transferred from the transfer unit at the second transfer portion so as to be superimposed on the first color image. Similarly, the third color image is transferred so as to be superimposed on the second image and the fourth color image is transferred so as to be superimposed on the third color image to the intermediate transfer drum. Accordingly, the first to fourth color images are superimposed.

Abstract: An intermediate transfer drum has at least a drum main body having a volume resistivity of 10.sup.4 to 10.sup.8 .OMEGA.cm, and an insulating layer provided on an outer surface of the drum main body. A first transfer voltage applying roller is provided inside the intermediate transfer drum so as to be opposite to a photosensitive drum and so as to be in contact with an inner surface of the intermediate transfer drum. A transfer roller is provided inside the intermediate transfer drum so as to be opposite to a second transfer grounded roller and so as to be in contact with the inner surface of the intermediate transfer drum. By thus arranging an image forming apparatus wherein image formation is carried out with respect to recording paper through the intermediate transfer drum, an optimal first transfer voltage can be applied from the photosensitive drum to the intermediate transfer drum, while an optimal second transfer voltage can be applied from the intermediate transfer drum to the recording medium.

Abstract: An electrographic copying machine has a photoreceptor drum which moves so that a photosensitive layer on its surface is successively charged, exposed, developed and charge-removed. The photosensitive layer is made of an amorphous material. The drum surface is charged by a charger before a latent image is formed thereon through exposure. A voltage generator is provided which supplies the charger with a voltage to charge the drum surface. It takes time for the potential of the charged drum surface at the developing section to reach a predetermined potential from a potential higher than the predetermined potential due to a rise characteristic of the surface potential. A controller is provided which corrects an output voltage value of the voltage generator to a voltage value necessary for the drum surface to be charged at the predetermined potential in a predetermined number of charging operations performed until the surface potential reaches the predetermined potential.

Abstract: In a copying processing performed several times from the depression of a copy button of a copying machine until the surface potential of the photoreceptor drum is stabilized, a voltage sufficiently high for correcting the rise characteristic of the photosensitive layer on the drum surface is applied to a charger. A main circuit having a controlling portion to realize this corrects the output voltage of the high-voltage generating circuit which applies a high voltage to the charger to a voltage value necessary for the drum surface to be charged at a stable potential level. The main circuit charges the drum surface at the stable potential level necessary for development from copying of the first sheet.

Abstract: A sheet feeding unit includes a sheet forwarding unit for forwarding sheets from a sheet storing unit, a key input portion, a sheet detection gate, and a control unit. In one embodiment, the sheet forwarding unit repetitively performs its function after an operation start instruction until either the sheet detection gate detects a sheet from the feeding cassette or until the number of repetitions of the sheet forwarding unit reaches a predetermined number. An error process is performed when the number of repetition reaches the predetermined number without the gate detecting a sheet. Also, the sheet feeding unit compares the number of times a sheet is fed from the sheet feeding unit with the number of times the sheet if forwarding to determine the status of the feeding roller.

Abstract: An encoder is connected to the drive system of the optical system of an image forming apparatus including an optical system for exposing a document image to a light and scanning the document image, a home position switch for detecting the optical system when it comes to the vicinity of the starting position, and a resist roller for setting the feeding start timing of a transfer sheet to the transfer section, and, on reproducing the above document image on a transfer sheet, when the pulse signals coming from the encoder, which are counted from the time when the optical system passes through the home position switch, reach the appointed value, the above resist roller operates.

Abstract: A paper supplying deck is insertable into and withdrawable from a paper supplying portion of a body resulting in electrical connection between the side of the paper supplying deck and the side of the body through a drawer-type connector when the paper supplying deck is inserted and interruption of such electrical connection when the drawer is withdrawn. The paper supplying deck has a paper carrying portion with a paper width setting mechanism and a variable resistor the resistance value of which is changed in dependence on the paper width setting mechanism, thereby changing an output paper width detecting voltage. On the wide of the paper supplying deck, a resistance which prevents the paper width detecting voltage from amounting to a power source voltage even though the resistance value of the variable resistor reaches a maximum value, is connected in series with the variable resistor.

Abstract: A toner conveyor disposed in a housing includes an upstream-side toner conveyor and a downstream-side toner conveyor. A toner amount detector is disposed to detect whether the amount of toner in the downstream portion of the housing is greater than a predetermined amount or not, and the upstream-side toner conveyor is not operated when the amount of toner is greater than the predetermined amount in the downstream portion of the housing. A toner replenishment signal is produced when the amount of toner is not greater than the predetermined amount in the downstream portion of the housing despite the downstream-side toner conveying means being operated for more than a predetermined period of time. The toner amount detector can be a plate which rests on top of the toner and pivots up and down as the toner level changes, with a magnet on the plate detected by a suitable detector.

Abstract: A sorter incorporating a stapler is an apparatus for sorting and stapling sheets discharged from an image forming apparatus. This sorter includes a plurality of vertically movable bins for storing the supplied sheets, a bin drive unit for conveying the bins, a stapler for stapling the sheets stored in the bins, a pair of lateral guides, and a lateral guide drive unit for moving the lateral guides. The lateral guides are movable in the width direction of the sheets in the bins and abut on both sides of stacks of the sheets to arrange them into widthwise adjustment, and then to move them into the stapling position of the stapler.