Electrophotography – Diagnostics – Consumable
Reexamination Certificate
2001-07-24
2003-02-25
Grainger, Quana M. (Department: 2852)
Electrophotography
Diagnostics
Consumable
Reexamination Certificate
active
06526235
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a toner replenishment control for an image forming apparatus such as a copier, a facsimile machine, a printer or the like, in which a latent-image pattern is formed on an image carrying body, the development characteristic is measured from electric potential information thereof and a toner adhesion amount, and, from the development characteristic, various electric potentials at a time of forming images regularly are determined.
2. Description of the Related Art
In an image forming apparatus such as a copier, a facsimile machine, a printer, or the like, employing an electrostatic photographic method, generally speaking, a photosensitive body drum is rotated by a motor or the like, the photosensitive body drum is uniformly charged by a charging device, then, an electrostatic latent image is formed on the drum as a result of an image being written thereonto through image exposure thereof by an exposure device, the thus-formed electrostatic latent image is developed by a developing device so as to be a toner image, the toner image is then transferred to a transfer material by a transfer device, and the toner image is fixed onto the transfer material by a fixing device.
In the image forming apparatus which forms an image through the above-mentioned electrostatic photographic process, an electrostatic-latent-image electric potential of a test pattern of the electrostatic latent image formed on the photosensitive drum body is measured, the development characteristic is obtained from the toner adhesion amount of the above-mentioned test pattern visualized by toner, and, from this development characteristic, various electric potentials such as a development bias potential and a charging electric potential of the image carrying body (photosensitive body drum) are calculated.
For example, the electrostatic-latent-image electric potential of the test pattern of the electrostatic latent image is measured, the toner adhesion amount of this test pattern of electrostatic latent image visualized by toner is measured, and, then, by using the thus-obtained measurement data, a straight-line approximated formula of the development characteristic, that is, a development &ggr; characteristic, is obtained through straight-line approximation. Then, an inclination of this straight-line approximated formula is assumed as being a development efficiency, and, from the development efficiency, the various electric potentials to be used for regular image formation are obtained.
Further, in a normal (regular) image forming occasion, a toner detecting pattern (test pattern) for toner replenishment control is produced every predetermined number of sheets of printing, and a toner replenishment amount is calculated from the detection result of the toner adhesion amount of this toner detecting pattern. For example, the toner detecting pattern is produced in a predetermined image production condition, the detection value of the toner adhesion amount of the toner detecting pattern is compared with a toner replenishment control target value, and, based on this comparison result, a toner amount to be supplied (toner replenishment amount) is determined.
Further, according to the above-mentioned detection result of the (toner) development characteristic, a development potential for producing the above-mentioned toner detecting pattern is lowered when the above-mentioned detection result of the development characteristic is such that the developing performance is judged as being low. As a result, toner adhesion of the toner detecting pattern is made to be such that the toner adhesion is lower than the above-mentioned toner replenishment control target value for the toner detecting pattern, and, thereby, toner replenishment becomes more likely to be actually performed as a result of ‘toner low’ being detected from the thus-intentionally-lowed toner adhesion of the toner detecting pattern. Thus, restoring of the development performance becomes more likely to be achieved.
However, in the above-described toner replenishment control method, when the development potential for producing the toner detecting pattern for toner replenishment control is altered, a resulting change in toner adhesion amount of the toner detecting pattern may vary according to a characteristic of the used developing agent, mechanical characteristic of the developing device, or environmental conditions. As a result, the toner adhesion amount of the toner detecting pattern may become excessively smaller or larger than an expected value.
In a case where toner replenishment control is performed based on a detection result of toner adhesion amount of the toner detecting pattern in a condition in which the toner detecting pattern is produced by fixed image production conditions, the toner replenishment control is performed such that the toner adhesion amount, in other words, the image density may not vary. However, the image production conditions may be intentionally altered for various reasons.
For example, there is a case where the developing potential is intentionally altered in order to change the toner adhesion amount of the toner detecting pattern so as to change the development performance. Further, in a system in which the image production conditions for the toner detecting pattern are made equal to be the image production conditions for regular image formation (in regular printing operation), the image production conditions for the toner detecting pattern are necessarily altered when the image production conditions for regular image formation are intentionally altered.
In such a case, the thus-altered image production conditions for the toner detecting pattern may result in change in the toner adhesion amount of the toner detecting pattern. However, the amount of change in the toner adhesion amount of the toner detecting pattern may not necessarily become an expected one.
For example, in a case where the toner density is to be increased because the detected development &ggr; characteristic is low, the development bias for developing the toner detecting pattern is intentionally lowed by 10 volts so that the development potential is lowered. Then, although the toner replenishment control target value has been equal to the toner adhesion amount of the toner detecting pattern immediately before the change, the toner adhesion amount of the toner detecting pattern may be reduced by an amount more than an expected one. In such a case, toner replenishment is automatically performed until the resulting toner adhesion amount becomes the toner replenishment control target value. For this purpose, the development performance may be excessively increased, and, this may result in undesired variation in density, and/or variation in color of printed images.
Such a problem may occur not only due to the above-mentioned fact that change in toner adhesion amount of the toner detecting pattern resulting from alternation of the development potential may differ due to environmental condition or the like, but also due to variation in the above-mentioned straight-line approximation for the development &ggr; characteristic, bad influence of a degraded control accuracy in a case where the development bias, charging electric potential, or exposure electric potential is made shifted, or the like.
Further, assuming that the toner detecting pattern for toner replenishment control is developed by a fixed development potential, the problem concerning shift of toner adhesion amount occurring by alteration of the development potential is reduced. However, when the charging characteristic of the developing agent varies due to aging and/or environmental variation, toner replenishment control is performed such that the developing amount may be made uniform with respect to the same potential. As a result, the toner density of the developing agent may vary too much, and, thereby, toner scattering, toner sticking, overflow of the developing agent, or the like may occur.
Thus, according to the
Grainger Quana M.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ricoh & Company, Ltd.
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