JPH06175450A - Image forming device - Google Patents

Abstract

PURPOSE:To prevent fluctuation in the determination of an image forming condition with the use of a determination table so as to enhance the stability of copying operation by allowing sections adjacent to the table to overlap each other. CONSTITUTION:The copy density is adjusted by a slide volume 21. In a bias setting control part 20, a comparing circuit 24 compares a present read value with a previous level stored in a memory 23. If the present set value is out of a previous level range, determination (for level determination scanning) with the use of a table 25 is carried out. Six stage determination levels are set on the table, and adjacent sections on the table overlap each other. Scanning for determining a level, is successively carried out from a low level, and an initially corresponding section is determined as an exact determination section. The result of the determination is delivered to an output circuit 2, and accordingly, the bias voltage is changed by means of a bias control circuit 11. Further, the result of the determination is stored in the memory 23.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus and, more particularly, to a stable image by preventing a change in image density for each copy when a plurality of identical originals are continuously copied by a copying machine (copying machine). Relating to technology that enables reproduction.

[0002]

2. Description of the Related Art There are the following configurations for setting a developing bias in a copying machine. That is, when the density is set by the slide volume for adjusting the image density provided in the operation unit, an analog voltage corresponding to the set density is output, and the analog voltage is A / D converted and taken into the control board. The level is divided using a table as shown in FIG. 4, the control data is output, and the bias of the developing sleeve is set.

The structure for judging A / D converted data by a table can be realized by software, is easy to realize and is low cost, and is suitable for a device such as an office desk copying machine which pursues small size, light weight and low cost. Is the preferred technique to use.

In a normal copying machine, the density of the image can be changed by changing the developing bias for each copy. Therefore, the copying machine judges the set copy density for each copy sequence using the above table, and sets the developing bias in accordance with the judgment.

[0005]

In the table of FIG. 4,
The judgment ranges (level ranges) do not overlap (for example, 0-9, 10-19). Therefore, if the copy density is set near the boundary between one range and another range, there is a risk that the judgment category will be different, affected by the operating state of the device at the time of judgment and the presence or absence of noise. Yes (that is, sometimes it is determined to belong to one category, and at other times it is determined to belong to the other category).

For example, when a plurality of copies are continuously made on the same original with the same copy density, during the copying, a slight fluctuation of the current due to the operation of the motor or the optical system or other noise causes A If the / D conversion data fluctuates, the judgment level fluctuates, and as a result, images with different shades are randomly obtained.

It is particularly important for a copying machine to obtain a stable image under the same setting conditions, and therefore, the fluctuation of the judgment level as described above causes a decrease in the reliability of the apparatus. .

On the other hand, low-cost machines have a limit in noise countermeasures. The present invention has been made based on such a consideration, and an object thereof is to prevent fluctuation of judgment using a table, improve stability of copying, and prevent deterioration of reliability of an apparatus. is there.

[0009]

[Means for Solving the Problems]

(1) In the present invention, adjacent sections in the judgment table have overlapping portions, and the scan for level judgment is performed by
The steps are sequentially performed from the low level side, and the first applicable category is determined as the category of the correct determination. (2) Further, prior to the above table determination, the comparison means compares the previous level and the current level stored in the memory, and only when they are different, the current level is determined by the table determination, and the determined level is determined. Is stored in the memory and the data is updated.

[0010]

[Action]

(1) Consider, for example, a case where a table as shown in the lower side of FIG. 2 has an overlapping portion and the developing bias is set. It is assumed that a large number of continuous copies having the same copy density are made for the same object. The A / D converted data value is, for example, “23” (that is, copying is executed at the judgment level 2).

It is assumed that the A / D converted data value changes to "24" due to noise or the like during copying.
In this case, since the values are different from the values up to that point, sequential scanning is performed from the low level side of the table. As a result, the data value "24" is found to be the judgment level 3 (17 to 33), and the development bias (-
180V), and the subsequent copying is also performed with the density of level 3 which is the latest judgment value.

Further, while the copying is continuing, this time, A /
If the D-converted data value fluctuates significantly from "20 to 28", the range of the judgment level 3 is still "17 to 3".
3 ”, there is a considerable margin, so that the judgment level 3 is not changed, and stable density copy is performed by the density of level 3 until the final copy.

As described above, using the table of the present invention, when data is set to the upper and lower limits of one judgment section, the judgment section is changed once due to noise and the copy density is changed. However, after the division is changed, the division after the deflection has a wide margin, so that the judgment division is not changed due to an unintended cause such as noise. Therefore, unlike the conventional case, the problem that the determination level fluctuates for each copy due to the operating state of the apparatus, noise, etc. and the copy density is not stable does not occur.

Moreover, it can be realized by a software method of changing the table and is easy to implement.

[0015]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of essential parts of an embodiment of an image forming apparatus of the present invention (desktop copying machine for office).

In the copying machine of this embodiment, the copy surface of the original 1 is scanned by the exposure lamp 2 and the reflected light is reflected by the optical systems 3 to 7.
To form an electrostatic latent image on the photoconductor drum 8 through the toner, and the toner 10 is attached to the drum 8 using the developing sleeve 9 whose bias voltage is controlled according to the copy density to develop the latent image. It has a function to form an image by transferring to a transfer paper.

The bias of the developing sleeve 9 is controlled by the bias control circuit 11, and the bias control circuit 11
Operates according to a control signal from the bias setting control unit 20. Also, the adjustment of copy density is
The slide volume 21 is used.

The bias setting controller 20 includes an A / D converter 22 for converting an analog signal (density setting signal) from the slide volume 21 into a digital signal, a memory 23 for storing the density level of the previous copy, and a previous copy. Comparing circuit 24 compares the density level of the current density with the density setting level of the current A / D conversion to determine whether there is a change, and to determine the current density level when it is determined that the density needs to be changed. Table 25 and output circuit 2 having a latch function
6 and 6.

As shown in the lower part of FIG. 2, the table 25 is divided into six judgment levels, and the adjacent sections have overlapping portions (for example, level 1 is 0 to 0). 13, Level 2 7-23). A development bias value from −40 V to −300 V is set corresponding to each of the six levels, and as a result of the determination using the table, a signal indicating the development bias value (that is, control voltage designation data). ) Is sent to the output circuit 26. The determined copy density level of this time is stored in the memory 24, and the stored value is updated accordingly.

With respect to the table 25, the rule is applied that the scan for level judgment is sequentially performed from the low level side, and the first applicable section is judged as the section of correct judgment.

Next, the operation of the apparatus will be described. When the copy density is set by the slide volume 21 and a copy button (not shown) is pressed, the density level is determined for each copy. That is, the analog signal from the slide volume 21 is A / D converted, and subsequently, the density level is determined by the procedure shown in FIG.

That is, first, the A / D converted data is read into the comparison circuit 24 (step 30). Next, the memory 23
The previous copy density level stored in is determined (steps 31, 33, 35, 37, 39) and the previous level found as a result and the read value of this time are compared (steps 32, 34, 36, 36). 38, 40, 41).

As a result of the comparison, if the set value of this time is within the range of the previous level, it is determined that the density level is not changed, and the comparison circuit 24 sends a signal to that effect to the output circuit 26, and the output circuit 26 maintains the current level of the control signal.

On the other hand, as a result of the comparison, if the set value this time is outside the range of the previous level, it is determined that the density level has been changed, and in this case, the determination (level determination scan) by the table 25 is performed (step). 42). When the current level is determined by this scan, the result is sent to the output circuit 26, the level of the control output is changed accordingly, the developing bias is changed via the bias control circuit 11, and the toner is changed. The amount of adhering is adjusted. The result of the table judgment is stored in the memory 23 (step 4
3).

In the table judgment of this embodiment, when the copy density is set near the upper and lower limit values of one section and the section is changed to the adjacent section due to noise during the execution of the copy, the change is made. The subsequent classification has a sufficient margin with respect to the upper and lower limits of the classification before the modification, so that the classification will not be changed thereafter. Therefore, it is possible to prevent variations in copy density when a plurality of copies are continuously made on the same original with the same copy density.

Although the control of the copy density has been described in the above example, the present invention is not limited to this.
It can also be used to determine other image forming conditions such as adjustment of color tone when forming a color image.

[0027]

As described above, according to the present invention, the following effects can be obtained. (1) There is no problem that the determination level fluctuates for each copy due to the operating state of the apparatus, noise, etc., and the problem that the copy density is not stable does not occur, and stable copying can always be performed. (2) It can be realized by a software method of changing the table and is easy to implement. (3) As a result, it is possible to improve the performance of an apparatus, such as an office desk copy machine, which is small, lightweight, and low in cost.

[Brief description of drawings]

FIG. 1 is a diagram showing a main configuration of an example of an image forming apparatus of the present invention.

FIG. 2 is a diagram for explaining the contents and characteristics of a table 25 of FIG.

FIG. 3 is a flowchart showing a characteristic operation procedure (concentration level determination procedure) in the apparatus of FIG.

FIG. 4 is a diagram showing the contents of a table in a conventional device.

[Explanation of symbols]

 1 Original 2 Exposure Lamp 9 Developing Sleeve 10 Toner 11 Bias Control Circuit 20 Bias Setting Control Unit 22 A / D Converter 23 Memory 24 Comparison Circuit 25 Judgment Table 26 Output Circuit

Claims (2)

[Claims] 1. An image forming apparatus that determines a set image forming condition using a table, obtains data necessary for realizing the image forming condition from the table, and executes image formation according to the data. There, the table has a format in which the data is associated with each of a plurality of judgment sections divided according to the level of a signal indicating the image forming condition, and between adjacent sections,
A part of the levels of the signals indicating the image forming conditions overlap each other, and further, in determining to which section of the table the signal indicating the image forming conditions belongs, from the low level section to the high level section. An image forming apparatus, characterized in that scanning is performed for each section and the first applicable section is determined as an applicable range. 2. A copy density can be set for each copy, and determination of the copy density is performed using a table, and the table can receive a signal indicating the set copy density. The level range is divided into multiple areas to create multiple sections, and development bias data is associated with each section. Also, some of the level ranges overlap between adjacent sections. In addition, in determining which division of the table the signal indicating the set copy density belongs to,
By sequentially scanning from low level to high level, the first applicable category is determined as the applicable range, and further, prior to the determination by the scan of the table,
The copy density level at the time of the previous copy stored in the storage means and the copy density level at this time are compared by the comparison means, and as a result of the comparison, it is determined that the copy density level at this time is different from the previous level. In this case, the current copy density level is determined by scanning the table, and the determined current toner density level is stored in the storage means.