Electrophotography – Control of electrophotography process
Reexamination Certificate
2000-09-11
2003-04-22
Ngo, Hoang (Department: 2852)
Electrophotography
Control of electrophotography process
C399S046000, C399S049000, C399S072000
Reexamination Certificate
active
06553191
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an adjustment control system in an adjustment mechanism for maintaining the quality of images produced by an image forming apparatus, such as an analog copying machine, a digital copying machine, a facsimile machine, and a laser printer.
An image forming apparatus, for example, an analog copying machine comprises an optical unit and a process unit. The optical unit reads an image on a document placed on a document table formed of glass. The process unit forms a developer image according to the image read out by the optical unit and transfers the image onto a recording medium such as a sheet paper.
In the copying machine, a resolution that can finally been obtained for a photocopy image depends on a resolution of exposure on a photoconductive drum and faithful-reproductivity of electrophotography processing for the exposure image.
For example, in an image forming apparatus, there occurs a case where photocopied objects produced by the same copying machine from the same original sheet material have densities differing from each other. The image density of an electrophotograph varies depending upon influence of variation and deterioration in image-forming conditions according to environmental and aging factors. Needless to say for analog copying machines, but also for other multigradation printers and digital copying machines, it is important to minimize the variation in the image density and to thereby stabilize the image density so that the quality of images can be maintained. Particularly, for color images, the image density influences not only density-reproductivity, but also color-reproductivity, therefore, it can be the that the stabilization in the image density is an indispensable conditional requirement.
Under these circumstances, conventional methods perform feedback control. The feedback control allows multiple test patterns to be formed on an image-carrier, detects the densities of the images, thereby grasps the variation in gradation characteristics, and repeats adjustment of operation sections in an image-forming section and determination for the quality (goodness or badness). In the control, the amounts of operations corresponding to control amount deviations are computed according to lookup tables preliminary created. The contents of the lookup tables are created offline. To describe the tables, a variety of experiments must be carried out to grasp characteristics (amounts of operations-corresponding to control amounts) of adjustment objects. The creation therefore requires much manpower and time.
In multi-input and multi-output systems, generally, the individual dependence relationships between inputs and outputs are not independent of each other. Therefore, description of the input-output relation-ships into the lookup tables requires lookup tables corresponding to the number of dimensions of the number of the inputs and the outputs. A system that handles a large number of dimensions therefore requires a large memory capacity for storing the tables; and accordingly, it requires a very large number of identification tasks All to be performed therefor. In addition, there are cases the aforementioned relationships are not suitable to an intended apparatus because of nonlinear characteristics, difference between the produces, reproductivity, and aged deteriorations. The employment of the feedback control allows the method to be practicable even in a case where the identification is incomplete to a certain extent. In this case, however, the number of converging operations and control time, before acceptance conditions of the quality determination is satisfied, is resultantly increased by the deviations from the characteristics of the apparatus that has processed the identification tasks.
As described above, in most cases where the multiple adjustment portions exist, adjustment portions have the dependence relationship with each other. This causes a phenomenon such as that, when one adjustment portion is adjusted in consideration of one adjustment amount, other multiple adjustment amounts are caused to vary; and when another adjustment portion is then operated for compensation therefor, a different characteristics amount is caused to vary. Thus, the method still arises problems in that the optimum adjustment is difficult and the efficiency of adjustment significantly decreases.
Jpn. Pat. Appln. KOKAI Publication No. 11-258873 discloses an adjustment control system that employs a rule-generating method, a feedback control method, and an adjustment control system. The rule-generating method generates desired adjusting rules according to the aforementioned various dependence relationships. The feedback control method repeats detection, determination, and scanning until a control amount deviation is adjusted to be within a given tolerance. This system combines the rule-generating method and the feedback control method, thereby successively detects the sensitivity, and further uses the adaptive-control method that determines the adjusting operation amount according to a result of the aforementioned checking for the density.
Adjustment-control systems as described above are required to implement reduction in the number of the control operations required for adjustment convergence and to implement further reduction in control time. For example, in an image forming apparatus, in a case where the density of a test pattern is measured, and the measurement is used as a control amount, developer consumption and apparatus-unusable time are required to be reduced as much as possible; and also, time required for the adjustment operation at an actual control site is required to be reduced as much as possible.
To comply with these requirements, Jpn. Pat. Appln. KOAKI Publication No. 2000-089525 proposes an adjustment control system that employs a so-called learning-control method and the above-described adaptive-control method. The learning-control method stores the relationships between individual control amounts and the operation amounts as successfully experienced instances so as to be used in subsequent control operations. The proposed system selectively executes the learning-control method and the adaptive-control method, and thereby, determines the operation amount. In addition, the proposed adjustment control system does not require the development of the lookup tables as described above, thereby allowing implementation of reduction of manpower, securement of adjustment convergence, and improvement in convergence efficiency.
However, the described adjustment control system, which selectively executes the adaptive-control method and the learning-control method, causes cases where the convergence is difficult, and defects such as overshoot occur when the system stores inappropriate learning data because of aged deteriorations and an abnormal state of the adjustment-object system. These defects repeatedly occur in subsequent adjusting operations.
BRIEF SUMMARY OF THE INVENTION
The present invention has been contrived in consideration of the above circumstances and its object is to provide an adjustment control system which prevents occurrence of problems making convergence and the like in control operations to be difficult and which can efficiently perform an optimum adjustment.
To achieve the above, an adjustment control system for an image forming apparatus comprises detecting means for detecting individual control amounts; deviation computing means for computing a plurality of control amount deviations in accordance with the control amounts detected by the detecting means and a predetermined target value; deciding means for deciding whether or not the individual control amount deviations are within a predetermined tolerance; operation amount determining means for determining an operation amount for compensating each of the plurality of control amount deviations when at least one of the control amount deviations is determined by the detecting means to be out of the predetermined tolerance; a plurality of operating mea
Foley & Lardner
Ngo Hoang
Toshiba Tec Kabushiki Kaisha
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