Abstract: A reference developing image is formed on a photoreceptor drum under an image forming condition measured in advance, and the density of this reference developing image is detected. A development bias voltage is corrected based on the detection result, and when a correction value of the development bias voltage exceeds a predetermined range, a reference output voltage of an ATC sensor for detecting the density of toner in a developing device is corrected based on the detected value of humidity around the developing device, the frequency of use of the apparatus, and the agitation stress of developer.

Abstract: There is provided an image stabilizing apparatus which is capable of keeping a toner concentration and a printing density constant when, toner consumption is small, and further which is systematically simple. The image stabilizing apparatus comprises a control portion for controlling a toner replenishment amount in a toner replenishing apparatus depending on a toner concentration detected by a toner concentration sensor and a print coverage of a document detected by a print coverage detecting portion, and controlling, when the print coverage of the document detected by the print coverage detecting portion is less than a predetermined value and such documents continue, so as to discharge a predetermined amount of toner to the image bearing member by developing forcibly, and then replenish the same amount of toner as the predetermined amount by the toner replenishing apparatus.

Abstract: An amount of toner consumption accompanying development of an image corresponding to the image data is calculated based on image data, and a corrected consumption amount is calculated by multiplying the calculated amount of toner consumption by a predetermined correction ratio that is less than 1. Further, toner is supplied based on the calculated corrected consumption amount. As a result, it is possible to prevent excessive supply of toner, and to supply toner without time delay.

Abstract: An image forming apparatus is provided which is capable of forming higher-quality images by detecting a toner concentration with higher accuracy to attain appropriate toner supply and image density. A value obtained by adding a correction value based on a temperature, humidity, a print coverage, or the like to a developer concentration adjustment value is set as a control voltage value Vc which is to be inputted to a toner concentration sensor, and an output value of the toner concentration sensor is detected for each of process speeds. A difference between the output value detected and a value at reference process speed is calculated and based on the difference, a correction value is further calculated. Such another calculation of the correction value with use of the output value detected allows for highly accurate correction.

Abstract: A controller determines the degree of acuteness of the resonant oscillation of a piezoelectric oscillator, based on the developer's fluidity detection data detected by the piezoelectric oscillator. The toner density output data detected by a toner density sensor is modified to a correct value, based on the degree of acuteness, and a supply roller is controlled based on this corrected value so as to implement the necessary toner supply.

Abstract: A controller determines the degree of acuteness of the resonant oscillation of a piezoelectric oscillator, based on the developer's fluidity detection data detected by the piezoelectric oscillator. The toner density output data detected by a toner density sensor is modified to a correct value, based on the degree of acuteness, and a supply roller is controlled based on this corrected value so as to implement the necessary toner supply.

Abstract: A reference developing image is formed on a photoreceptor drum under an image forming condition measured in advance, and the density of this reference developing image is detected. A development bias voltage is corrected based on the detection result, and when a correction value of the development bias voltage exceeds a predetermined range, a reference output voltage of an ATC sensor for detecting the density of toner in a developing device is corrected based on the detected value of humidity around the developing device, the frequency of use of the apparatus, and the agitation stress of developer.

Abstract: An amount of toner consumption accompanying development of an image corresponding to the image data is calculated based on image data, and a corrected consumption amount is calculated by multiplying the calculated amount of toner consumption by a predetermined correction ratio that is less than 1. Further, toner is supplied based on the calculated corrected consumption amount. As a result, it is possible to prevent excessive supply of toner, and to supply toner without time delay.

Abstract: An image forming apparatus which can detect a defect in a nozzle and an optical system, and inform an execution of maintenance. The apparatus comprises a scanner which reads an image; a print head which prints an image; a test pattern image data ROM stored a test pattern; and an image processing unit which diagnoses a defect in the print head and the scanner by processing data of the test pattern which is read by the scanner.

Abstract: The image forming apparatus of the invention controls the toner density by any one of the following configurations: by correcting the toner density of the developer in association with the agitation total; by controlling a process parameter so that the density of a toner patch formed on the photoreceptor corresponds to a prescribed density value and determining that developing performance of the developer is improved and canceling the toner density correction when the process parameter reaches the prescribed value; by changing the toner density reference value when the variation as to the charger output is equal to or greater than a first predetermined value and maintaining the changed toner density reference value until the variation of the charger output again becomes equal to or greater than the first predetermined value; or by prohibiting toner supply for a constant duration to prevent excessive toner supply if time from the end of the last operation of the developing unit to the start of a next operation

Abstract: CPU is designed to create toner patches on the surface of the photoreceptor drum and pick up the detected data of the density of the toner patches by a photosensor. CPU calculates a correcting value .DELTA.Vg of the charger output in accordance with the picked up detected data, and compared the corrected charger output Vg with (Vgs+.alpha.) and (Vgs-.alpha.). If the corrections in the same direction are repeated in a row, k.beta. (where 0<k<1) is added to or subtracted from the toner density reference value. When the direction of the correction for the toner concentration reference value to be made is opposite that of the previous one, the absolute value of the correcting value for the current correction is set to be the absolute value of the previous one.

Abstract: A process control apparatus of electrophotographic apparatus has an optical sensor for optically detecting the density of toner patches formed on a photoreceptor drum. The present apparatus is further provided with a control device for controlling lamps for the copying process, chargers and other elements. A toner patch is formed on the photoreceptor so as to be located between every two toner images for a copying operation. The control device controls the lamps, chargers and other elements in accordance with the result of the toner patches detected by the optical sensor so as to stabilize the copying picture quality. With the arrangement, it is avoided that the job efficiency during the copying operation deteriorates, and the control data obtained from the toner patches is soon used for the toner image formation for the copying operation, thereby ensuring that the process control improves in accuracy.

Abstract: An apparatus includes a system controller which calculates a ratio of a first signal to a second signal and adjusts a control parameter of an electrophotographic reproduction process so that the density of fog indicated by the ratio is within a predetermined range. A first optical sensor outputs the first signal by detecting a reflectance of a non-image area on the photoreceptor between a developing unit and a transfer charger. A second optical sensor outputs the second signal by detecting a reflectance of a surface of the photoreceptor between a cleaning unit and a charger. The system controller controls developer including toner and carrier to be agitated when the ratio obtained after adjusting the control parameter is still outside the predetermined range. Since the density of fog is detected with accuracy by calculating the ratio, copy quality is stabilized even when temperature changes.