Electrophotography – Control of electrophotography process – Of plural processes
Reexamination Certificate
2000-09-26
2001-11-20
Grimley, Arthur T. (Department: 2852)
Electrophotography
Control of electrophotography process
Of plural processes
C399S072000, C399S074000
Reexamination Certificate
active
06321044
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-274885, filed Sep. 28, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to an image forming apparatus and method in use as, for example, an electrophotographic full-color printer or full-color copier.
As a multi-color image forming apparatus of this type, a quad-tandem color image forming apparatus that comprises a plurality of electrophotographic process units arranged opposite to the same transfer belt is known. In the quad-tandem color image forming apparatus, various controls are executed to obtain an image superposed without displacement.
For example, a rotational speed of a drive motor for a drum or a drive motor for a belt is controlled so as to make a rotational circumferential speed of photosensitive drums of plural electrophotographic process units equal to a moving circumferential speed of the transfer belt. In addition, a plurality of photosensitive drums are arranged with a predetermined gap disposed therebetween. Therefore, the image forming timing to the photosensitive drums can be shifted in time in accordance with the gap of the photosensitive drums.
Actually, however, there are various conditions such as displacement of an exposure beam, misalignment in a pitch of a photosensitive drum, slipping between a transfer belt and the roller which drives the transfer belt, variation in the circumferential speed of the transfer belt caused by the thermal expansion in the diameter of the roller which drives the transfer belt, and the like, and it is therefore difficult to obtain a superposed image having no displacement.
Thus, the color image forming apparatus comprises a sequence of solving a problem of displacement in the superposed image by utilizing the warm-up time after opening a door at the time of turning on a power supply or in a paper jam process.
This apparatus also comprises a sequence of optimizing the image density, which is the amount of adhesion of the toner, even when the characteristics are varied due to the variation in temperature or deterioration in lifetime.
A registration sensor is used for the sequence of solving the displacement in the superposed image, and a toner density sensor is used for the sequence of optimizing the image density. The registration sensor and the toner density sensor are arranged at the most downstream side in the sheet conveying direction so as to detect marks for detection of the toner density and the displacement, which are formed on the transfer belt.
The registration sensor and the toner density sensor are arranged opposite to one another in the close vicinity of the transfer belt.
Incidentally, when a sheet on which a toner image is transferred is conveyed by the transfer belt at the time of image formation, the toner flies off from the toner image since the toner image is in a non-fixed state. For this reason, the flying toner adheres to the registration sensor and the toner density sensor, and may thereby cause stains and make the detection impossible.
If the registration sensor and the toner density sensor are covered with a hood at the time of image formation, adhesion of the flying toner can be prevented. However, the gap between the toner density sensor and the transfer belt is small, i.e. about 5 mm, and thus the hood or the like cannot be used.
In the prior art, for example, the detecting surface of the registration sensor and the toner density sensor has been cleaned by a hand or by a cleaner interlocking with the opening and closing operation of a front door of the apparatus, at the time of maintaining and checking the apparatus.
However, the stains cannot be certainly removed by the cleaning, which causes deterioration in the accuracy of detection. In the cleaning process, the detecting surface of the sensor may be scarred or, on the contrary, a lump of stains may be applied thereto.
BRIEF SUMMARY OF THE INVENTION
The present invention is accomplished by consideration of the above-described circumstances, and the object of the present invention is to provide an image forming apparatus and method capable of preventing adherence of the flying developer on the detecting means, and discriminating whether a member for preventing the adherence of the developer is normally operated or not without providing any additional detecting means.
An image forming apparatus according to the present invention comprises an image forming means for forming a developer image on an image carrier, a detecting means for detecting the developer image formed by the image forming means, a control means for controlling the formation of the developer image on the image carrier executed by the image forming means, in accordance with detection information of the detecting means, an opening/closing member for opening a detecting surface of the detecting means when the developer image is detected by the detecting means, and for covering the detecting surface thereof when the developer image is not detected, and a discriminating means for discriminating a condition of the operation of the opening/closing member by using a result of the detection of the developer image executed by the detecting means.
Another image forming apparatus according to the present invention comprises an image forming means for forming a developer image on an image carrier, a transfer means for conveying a member on which the developer image is to be transferred while placing the member on a transfer surface, and allowing the developer image formed on the image carrier to be transferred on the member or allowing the developer image to be directly transferred on the transfer surface as a mark for control of the image formation, a detecting means provided so that a detecting surface thereof faces the transfer surface of the transfer means, for optically detecting the control mark formed on the transfer surface, a control means for controlling the formation of the developer image on the image carrier executed by the image forming means, in accordance with detection information of the detecting means, an opening/closing member movably provided between the detecting surface of the detecting means and the transfer surface, for moving in a first direction and opening the detecting surface of the detecting means when the control mark is detected by the detecting means and for moving in a second direction opposite to the first direction and covering the detecting surface of the detecting means when the control mark is not detected, and a discriminating means for discriminating a condition of the operation of the opening/closing member by using a result of the detection of the control mark executed by the detecting means when the opening/closing means executes the opening/closing operation.
An image forming method according to the present invention comprises the steps of forming a developer image on an image carrier, detecting the developer image formed at the image forming step, by a detecting means, controlling the formation of the developer image on the image carrier executed at the image forming step, in accordance with detection information obtained at the detecting step, operating an opening/closing member for opening a detecting surface of the detecting means when the developer image is detected by the detecting means, and for covering the detecting surface thereof when the developer image is not detected, and discriminating a condition of the operation of the opening/closing member by using a result of the detection of the developer image executed by the detecting means.
Another image forming method according to the present invention comprises the steps of forming a developer image on an image carrier, conveying a member on which the developer image is to be transferred while placing the member on a transfer surface of a transfer means, and allowing the developer image formed on the image carrier to be transferred on the member or al
Foley & Lardner
Grimley Arthur T.
Toshiba Tec Kabushiki Kaisha
Tran Hoan
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