Abstract: An image forming apparatus, wherein the packing density at a closest point where the first peripheral surface and the second peripheral surface are the closest to each other is within a range from 0.3 to 0.4; wherein a maximum magnetic flux density of a principal magnetic pole for generating the magnetic field for development is located in an upstream side from the closest point with respect to the specified direction and at a point where the packing density is equal to or greater than 0.2; and wherein a magnetic flux density of the principal magnetic pole at a point where the packing density is 0.2 in a downstream side from the closest point with respect to the specified direction is equal to or less than ½ of a magnetic flux density of the principal magnetic pole at a point where the packing density is 0.2 in the upstream side.

Abstract: An image forming apparatus for forming a toner image on a print medium with a developer composed of toner and carriers, wherein when the first distance is longer than the second distance, an average gap between the first peripheral surface and a member that faces to the first peripheral surface in an area with a length of the first distance extending upstream from the closest point with respect to the specified direction is smaller than an average gap between the first peripheral surface and a member that faces to the first peripheral surface in an area with a length of the first distance extending downstream from the closest point with respect to the specified direction.

Abstract: A two-component developing device using a developer containing toner and magnetic carrier particles. The developing device comprises a housing, a developing roller, a magnetic field generator mounted inside the developing roller, and a developer restricting member, and further comprises a developer guide member providing a developer guide path for guiding the developer to the developer amount restricting clearance, providing a developer circulation path for circulating the developer to an upstream end of the guide member, and providing a communication path for bringing the developer guide path into communication with the developer circulation path, an upstream end of the guide member being positioned above the position of a peak of magnetic flux density of the magnetic pole of the magnetic field generator which is closest to a low-magnetic force area downstream of the low-magnetic force area or positioned upstream of such a position and downstream of the low-magnetic force area.

Abstract: In case new and old toners may be mixed, a developing bias is set as follows. The time is first clocked. The number of times toner is replenished from a hopper into a buffer for a clocked period is counted. If a replenishment amount per clock time is a threshold value or higher, considering that new and old toners are mixed, the setting of the developing bias is changed. An electric field intensity between a developing roller and a photoconductor is set to cause normally-charged toner to fly in an image area but not to fly in a background area. No image fogging is therefore generated in the background area. Thus, an image forming apparatus and method capable of preventing low-charged toner and oppositely-charged toner generated by mixing of new and old toners from adhering to the background area of an electrostatic latent image on the photoconductor, thereby avoiding generation of image fogging.

Abstract: In case new and old toners may be mixed, a developing bias is set as follows. The time is first clocked. The number of times toner is replenished from a hopper into a buffer for a clocked period is counted. If a replenishment amount per clock time is a threshold value or higher, considering that new and old toners are mixed, the setting of the developing bias is changed. An electric field intensity between a developing roller and a photoconductor is set to cause normally-charged toner to fly in an image area but not to fly in a background area. No image fogging is therefore generated in the background area. Thus, an image forming apparatus and method capable of preventing low-charged toner and oppositely-charged toner generated by mixing of new and old toners from adhering to the background area of an electrostatic latent image on the photoconductor, thereby avoiding generation of image fogging.

Abstract: Developing bias is set as follows. An electric field intensity between a developing roller and a photoconductor is set to cause normally-charged toner to fly in an image area and not to cause the toner to fly in a background area. Thus, the normally-charged toner does not fly in the background area. The normally-charged toner caused to fly is therefore unlikely to flick low-charged toner and oppositely-charged toner. The low-charged toner and the oppositely-charged toner will not adhere to the background area and cause image fogging. Accordingly, an image forming apparatus can be provided to prevent the low-charged toner and the oppositely-charged toner from adhering to the background area of an electrostatic latent image on the photoconductor and to avoid the occurrence of image fogging in the background area on a printed material.

Abstract: In order to simply and easily treat drainage produced by cutting a face to be cut such as concrete without discharging the drainage on a road, a floor of a building, or the like, the concrete cutting machine of the present invention comprises a cutting mechanism for cutting the face by means of a rotating blade covered by a cover, a water supply mechanism for supplying and jetting water cooling to the rotating blade, and a collecting mechanism for collecting the drainage produced inside the cover by the jetting of the water cooling when the face is cut by the rotating blade. Further, in the collecting mechanism, the drainage produced inside the cover is sucked through a sucking portion provided on the lower end periphery of the cover to a collecting portion by a sucking operation of a suction blower so that the drainage in which air is removed at the collecting portion is discharged by a pump for collection.