JP3307077B2 - Tandem type color image forming apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine in which a plurality of laser driving devices and photosensitive drums are provided for each color, and an electrostatic latent image is formed on each photosensitive drum to perform color printing. The present invention relates to an image forming apparatus such as a facsimile, and further relates to print control for obtaining a high-quality image without color shift in such an image forming apparatus.

[0002]

2. Description of the Related Art As the demand for high productivity and high image quality of copying machines and the demand for copying color originals are increasing, the configuration of electrophotographic image forming apparatuses tends to become more complicated year by year. It is in.

FIG. 3 is a schematic configuration diagram of a conventional tandem-type color image forming apparatus using an electrophotographic system. The tandem type color image forming apparatus includes a photosensitive drum 1
An image forming unit including a charging corotron 2, a laser generator 3, a developing unit 5, a transfer corotron 6, and a cleaner (not shown) is transferred to a transport unit including a transport belt (transfer material carrier) 9 and the like. In addition, a plurality of black (K), yellow (Y), magenta (M), and cyan (C) colors are arranged and arranged in a column.

In such a tandem type color image forming apparatus, an optical image obtained by color separation of a color original read by image reading means (not shown) is formed by a laser based on an output signal of a reference signal generator 10. The laser beam is converted into an image forming laser beam 4 via a generator 3 and scanned on the photosensitive drum 1 to form an electrostatic latent image, and the electrostatic latent image is developed by each color toner. The image is transferred to a sheet (transfer material) 8 located at a transfer section 6. When the paper 8 passes below the photoreceptor drum 1 of each color (K, Y, M, C) by the transport belt 9, each color is superimposed and transferred, and a desired color is obtained.
Printing is performed. Here, the reference signal from the reference signal generator 10 is a signal that is generated based on the interval between the photoconductors of each image forming unit and the paper conveyance speed, and is a time reference for the operation of each image forming unit. .

[0005] The current demands for color image forming apparatuses such as copiers and the like are, first, to provide high productivity and, second, to obtain high-precision image quality. In order to achieve high productivity, it is necessary to feed and convey a large number of sheets within a unit time, and it is necessary to control the sheet interval to a minimum. Further, in order to achieve high image quality, it is necessary to know the state of the copying machine in a short cycle, so that as many reference points as possible are located between the successively supplied sheets on the photosensitive drum 1. The pattern must be monitored by the surface potential sensor 11 by providing the potential pattern 12 or the like, and the state of formation of the latent image and the state of formation of the image must be accurately known, and fine image quality control must be performed.

However, in the conventional image forming apparatus, a large reference potential pattern is formed at a distance between image latent images formed on one photoreceptor drum surface, so that the measurement of the pattern can be skipped. In order to prevent the problem or to increase the cycle of creating the reference potential pattern in order to obtain high productivity, control was performed, so that fine control could not be performed, and both of the above requirements could not be satisfied at once. It was difficult.

Therefore, in order to achieve both the requirements of high productivity and high image quality, the reference potential pattern is formed by narrowing the interval between the sheet and the reference potential pattern as closely as possible and defining the position strictly. It is necessary to read this reference potential pattern accurately. However, each image forming unit has a problem that the designed installation position is shifted from the actual installation position. If the interval between the sheet and the reference potential pattern is extremely reduced, the formed image range is also monitored. However, there is a risk that the accurate reference potential pattern may not be monitored.

In order to achieve the above object, for example, JP-A-2-60020 and JP-A-3-261973 describe that various timing controls are adjusted by an external operation. However, in this method, it is necessary to change the reference value stored in the storage means in accordance with a change in the state, so that an operator or the like must perform this adjustment work at the time of copying. Was.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and eliminates the need for an operator or the like at the time of copying to make adjustments to a photosensitive drum easily and accurately. It is an object of the present invention to provide an image forming apparatus capable of accurately detecting a reference position with an attached surface electrostatic potential sensor and automatically adjusting image quality.

[0010]

According to the present invention, there is provided an image forming apparatus provided with a photoconductor potential detecting means, comprising: a reference signal generating means for generating a reference signal at a time interval based on an interval between photoconductors;
A color shift amount detecting means for detecting a relative positional shift amount of each output color, a correcting means for correcting a reference signal based on the color shift amount, and the reference potential pattern based on the corrected reference signal. Of the photoreceptor electrostatic potential detecting means for measuring the

[0011]

The present invention compares the method of preventing the measurement of the latent image from being missed by increasing the reference potential pattern by increasing the distance between the latent images, which is found in conventional copying machines. As a result, since there is no extra interval, high productivity can be obtained. Also, in order to achieve high productivity, more reference potential patterns can be detected and finely controlled compared to a method in which a reference potential pattern is created and the control cycle is lengthened. Obtainable. Further, according to this apparatus, unlike the above-described conventional technique, correction is performed based on the amount of deviation detected with respect to the fixed reference value, so that there is no burden on the operator and high-quality recording as described above can be performed with high productivity. Can be made higher.

[0012]

FIG. 1 is a diagram showing a schematic configuration of a tandem type color image forming apparatus according to the present invention. An embodiment of the present invention will be described with reference to FIG. The description of the same parts as those in FIG. 3 is omitted. This color image forming apparatus is different from the apparatus shown in FIG. 3 in that a registration control pattern reading unit 13 using an optical sensor and a relative positional shift of each color output from each image forming unit based on the output of the reading unit. It is characterized in that a color shift amount calculating means 14 for calculating the amount and a correcting means 15 for correcting the generation timing of the reference signal based on the color shift amount are provided.

The operation will be described below. At the time of production adjustment at a factory or when the photoconductor is replaced at the place of use, the amount of color misregistration of each photoconductor drum 1 is detected before copying is started. The color shift amount detection process will be described. Photoconductor drum 1
Are charged by the charging corotron 2 to prepare for forming a latent image. The reference signal generating device 10 generates a reference signal for each image forming unit (K to C) at a timing obtained based on an installation interval of each photosensitive drum 1 of each image forming unit (K to C), a sheet conveying speed, and the like. . However, the installation interval is an ideal interval in design, and the installation accuracy at the time of assembly is not considered at all. The laser generator 3 of each image forming unit emits the image forming laser light 4 at the timing of the reference signal to start image formation, and uses, for example, a reference potential pattern on the photosensitive drum 1. A latent image of the detected color misregistration detection pattern (registration control pattern) is formed.
This latent image is converted into a visible image by the developing device 5 and is transferred to, for example, the conveyor belt 9 by the copying corotron 7.

The latent image of the pattern for detecting the amount of color misregistration formed on each photosensitive drum 1 of each of the image forming sections (K to C) at the timing of the reference signal is substantially at the same position on the conveyor belt 9. Is transferred to form a registration control pattern shown in FIG. FIG. 2A shows an example of a registration control pattern having no color shift, and FIG. 2B shows an example of a registration control pattern having a shift for each color.
The color misregistration detection patterns output from the respective image forming units may all be the same size as in this example, and may be other color misregistration detection patterns than the black (K) color misregistration detection pattern. Is increased, the amount of color misregistration can be easily detected using both edges of the color misregistration detection pattern.

The color misregistration detection pattern (registration control pattern) output from each of the image forming sections is read by the optical sensor 13 and information on the relative mutual position of each color is subjected to color misregistration. Output to the quantity calculation means 14. The color misregistration amount calculating means 14 forms an image of each of the other colors based on the photosensitive drum 1 of the image forming section (for example, K) of a reference color from the detected color misregistration amount of the color misregistration detection pattern. The shift amount of the actual installation position of each photosensitive drum 1 of the section (Y to C) is calculated. This calculation result can be stored in a storage unit (not shown) provided in the color shift amount calculation unit 14 or the correction unit 15.

Next, a process of performing copying will be described.
Based on the amount of color misregistration for each photosensitive drum of each image forming unit obtained by the above procedure, each correction unit 15 causes the image forming laser.
The irradiation timing of the light 4 is corrected. That is, the timing at which the image forming laser light 4 is generated from the generation of the reference signal is corrected, and the deviation of the visible image formed on the sheet 8 sent on the transport belt 9 is corrected. Therefore, the image forming laser light 4 is formed on each photosensitive drum 1 of each image forming section (K to C).
Is formed by correcting the color shift of each photosensitive drum 1.

A reference potential pattern 12 is formed between latent images (between sheets) formed on the surface of each photoconductor drum 1 based on a reference signal generated by a reference signal generator 10.
By detecting the pattern 12 with the surface electrostatic potential sensor 13, the electrostatic potential application state of the photosensitive drum is detected, and the image quality formation state such as color density and gradation is detected to perform image quality control. At this time, the position of the latent image of the reference potential pattern 12 and
In relation to the timing of detecting the reference potential pattern 12,
Since the engagement is accurately set by the corrected reference signal, the surface electrostatic potential detection sensor 11 can accurately detect the reference potential pattern 12.

That is, a reference potential pattern 12 is formed at an interval between image latent images and the image latent image is separated, and only the reference potential pattern 12 is detected by the surface electrostatic potential sensor 11 while timing is measured based on the reference signal. The image can be read and used for controlling the image forming unit. Here, the position of the image latent image is moved to correct the color shift as described above,
Further, a reference potential pattern 12 formed between image latent images
Is moved in the same manner, the timing is directly obtained from the uncorrected reference signal, and the surface electrostatic potential sensor 11
When reading the reference potential pattern 12 by
Since not only the reference potential pattern but also the image latent image portion is read and accurate control cannot be performed,
It is necessary to correct the timing from the reference signal generator 10 in consideration of the color shift obtained above, and the reference potential pattern 12 can be accurately read using the output signal of the correction means 15, High-precision control can be performed.

[0019]

According to the tandem type color image forming apparatus provided with the photoconductor potential detecting means of the present invention, a means for generating a reference signal at a time interval based on a design installation interval of each photoconductor, A color misregistration amount detecting means for detecting a relative color misregistration amount, a correction means for correcting a reference signal based on the color misregistration amount, and a surface static measurement for measuring the reference potential pattern based on the corrected reference signal Since the electric potential detecting means is provided, the reference electric potential pattern is read out without necessitating a particularly large interval between the image and the reference electric potential pattern when reading the reference electric potential pattern as compared with the conventional tandem type color image forming apparatus. Can be prevented, and high productivity can be obtained in image formation.

Further, as described above, since the image formation can be controlled without lengthening the cycle of generating the reference potential pattern, high productivity can be achieved, and more reference potential patterns can be read and read. Based on this, it is possible to obtain a high quality image.

Further, according to this apparatus, unlike a conventional color image forming apparatus, correction is applied to a fixed reference signal. This produces an effect that high-quality recording can be performed with high productivity.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an image forming apparatus according to the present invention.

FIG. 2 shows an example of a registration control pattern.

FIG. 3 is a schematic configuration diagram of a conventional image forming apparatus.

[Explanation of symbols]

Reference Signs List 1 photoreceptor drum, 2 charged corotron, 3 laser generator, 4 laser light for image formation, 5 developing device, 6 transfer corotron, 7 transfer material transport roll,
8 paper (transfer material), 9 transfer belt (transfer material carrier), 10 reference signal generator, 11 surface electrostatic potential sensor, 12 reference potential pattern, 13 registration control pattern reading means (optical sensor), 14 color shift Quantity calculator, 15 correction means.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 21/00 370-512 G03G 21/14 G03G 15/00 303 G03G 15/01 G01J 3/46

Claims (4)

(57) [Claims] 1. A tandem type color image forming apparatus comprising: a plurality of image forming units, wherein a reference potential pattern formed on a photoconductor of each image forming unit is read by a surface electrostatic potential sensor. Reference signal generating means for generating a reference signal at a time interval based on the design installation interval, color shift amount detecting means for detecting a relative positional shift amount of each output color, and a reference signal based on the color shift amount. Correction means for correcting the reference potential pattern based on the corrected reference signal.
A tandem-type color image forming apparatus, comprising: a photoconductor potential detecting unit that determines a timing of measurement and measures the reference potential pattern. 2. A color misregistration amount detecting means comprising: a registration control pattern reading means comprising an optical sensor for reading a registration control pattern; 2. The tandem-type color image forming apparatus according to claim 1, further comprising a color shift amount calculating unit that calculates a color shift amount indicating a shift in the installation interval of the photoconductors. 3. The photoconductor according to claim 1, wherein the correction unit is provided for each photoconductor except a photoconductor serving as a reference.
5. A tandem type color image forming apparatus according to item 1. 4. The apparatus according to claim 3, wherein said correction means determines a correction amount of a reference signal for each photoconductor based on the amount of color misregistration, and corrects a detection timing of the photoconductor potential detection means. A tandem type color image forming apparatus as described in the above.