Image forming apparatus including improved toner image density detecting arrangement
AssigneeMita Industrial Co., Ltd.
InventorsKazuto Hori, Sadao Tanigawa
Life of this patent
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Abstract
An image forming apparatus capable of detecting a toner image density well by shifting a developing bias. In adjusting a fog density or a solid density, the developing bias is shifted by a specified width so as to form an image of a gray density. This enables detection of the fog density and the solid density to be replaced with detection of a density in a gray density region where a reflection type photosensor can detect a density with high sensitivity. Thus, densities in a fog or solid density region where usually an output from the reflection type photosensor is saturated can be detected with high accuracy.
Claims11
An image forming apparatus, comprising:
- a photoconductor having a surface on which an electrostatic latent image is formed corresponding to an intended image;
- a developing device for developing an electrostatic latent image into a toner image;
- developing bias control means for variably controlling a developing bias which corresponds to a potential difference between said surface of said photoconductor and said developing device;
- a reflection type photosensor, provided opposed to a toner image carrier for carrying a toner image thereon, said reflection type photosensor for irradiating the toner image carrier with a specified quantity of light and detecting a quantity of light reflected therefrom;
- means for detecting a fog density, a gray density or a solid density of the toner image based upon an output from said reflection type photosensor;
- means for inputting an adjustment signal representative of an image density to be adjusted based on an output from said means for detecting;
- and
- bias shift means for controlling said developing bias control means and shifting the developing bias by a specified width when adjusting to one of a fog density or a solid density in response to said adjustment signal from said means for inputting an adjustment signal, thereby forming a gray density toner image.
A method for detecting a density of a toner image carried by a toner image carrier with a reflection type photosensor which irradiates the toner image carrier with a specified quantity of light and detects a quantity of light reflected therefrom, said method being applicable to an image forming apparatus for developing an electrostatic latent image formed on a photoconductor into a toner image by a developing device including means for applying a specified potential difference as a developing bias between the photoconductor and the developing device, said method comprising the steps of:
- judging which toner density is to be detected from the group of a fog density, a gray density or a solid density;
- shifting the developing bias by a first specified width under a condition where a density of a fog density toner image is judged, such that a gray density toner image is formed, or alternatively, shifting the developing bias by a second specified width under a condition where a density of a solid density toner image is judged, such that a gray density toner image is formed;
- and
- detecting a toner image density on said toner image carrier based upon an output from said reflection type photosensor.
An image forming apparatus, comprising:
- a photoconductor having a surface on which an electrostatic latent image is formed corresponding to an intended image;
- a developing device for developing an electrostatic latent image into a toner image;
- developing bias control means for variably controlling a developing bias which corresponds to a potential difference between said surface of said photoconductor and said developing device;
- a reflection type photosensor provided opposed to a toner image carrier for carrying a toner image thereon, said reflection type photosensor for irradiating the toner image carrier with a specified quantity of light and detecting a quantity of light reflected therefrom;
- means for comparing a density detected based upon an output from said reflection type photosensor with a reference density when an image of said reference density is put opposed to said reflection type photosensor, wherein said image of said reference density is a toner image carried by the toner image carrier, and said image of said reference density includes an image of a fog density, an image of a gray density or an image of a solid density;
- output calibrating means for calibrating the output of said reflection type photosensor based upon a result of a comparison by said comparing means;
- bias shift means for controlling said developing bias control means and, when calibrating the output of said reflection type photosensor corresponding to one of a fog density or a solid density, shifting the developing bias by a specified width, thereby forming a gray density reference toner image;
- and
- means for obtaining an output of said photosensor which should have been output if the developing bias had not been shifted, based upon said specified width for shifting the developing bias, when a toner reference image is formed with the developing bias being shifted by said specified width;
- wherein said means for comparing compares an output obtained by said means for obtaining an output, when calibrating the output of the photosensor corresponding to one of a fog density or a solid density, with said reference density.
Dependencies are inferred from the claim text.