JPH04149478A - Image forming device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an image forming apparatus.

[Conventional technology]

As an example of a conventional image forming apparatus, a laser beam modulated according to recorded information is irradiated onto a photosensitive drum, an electrostatic latent image on the photosensitive drum is developed by an electrophotographic process, and an image is transferred onto transfer paper. It has multiple recording devices for transcription,
In a color image forming apparatus in which a transfer belt sequentially conveys a transfer sheet to each recording device and transfers each color image in a superimposed manner,
Due to mechanical installation errors between each photosensitive drum, optical path length errors of each laser beam, optical path changes, etc., electrostatic latent images are formed on each photosensitive drum, and each color image is developed and transferred to the recording paper on the transfer belt. Registration doesn't match. For this reason, conventionally, the registration correction pattern image formed on the transfer belt from each photosensitive drum is read by a CCD sensor, etc., and the registration deviation on the photosensitive drum corresponding to each color is detected, and the image signal to be recorded is The optical path length change or optical path change is corrected by applying electrical correction and driving a reflecting mirror provided in the optical path of the laser beam.

[Problem to be solved by the invention]

However, in such an apparatus, there is still room for improvement regarding the registration correction that occurs when replacing an image forming member such as a photosensitive drum.For example, when replacing a photosensitive drum corresponding to a certain color, when replacing a photosensitive drum corresponding to a certain color, Registration compensation is performed again, and there is a problem that it takes time to correct the registration, or there is a problem that the correction state changes from a state where the registration is correct to a state where the registration is not correct. It wasn't without fear.

This problem occurs not only in image forming apparatuses using the above-mentioned electrophotographic process, but also in apparatuses using other methods, such as inkjet recording methods.

An object of the present invention is to provide an image forming apparatus in view of this point.

[Failure to solve the problem]

In order to achieve the above-mentioned object, the present invention has a replaceable image forming member for each color, a pattern image forming means for forming a pattern image for registration correction, and a means for reading the formed pattern image for each color. a pattern image reading means, and a registration correction means for correcting registration deviations of other colors using a predetermined color as a reference color based on the reading result of the pattern image reading means, and an image for the reference color. The present invention is characterized in that different registration corrections are performed when replacing a forming member and when replacing an image forming member for another color.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 1 is a configuration diagram of four recording devices and a transfer belt showing an embodiment of the present invention.

Magenta (M a ), Nyan (Cy), Yellow (Y
e) The black (Bk) photosensitive trams 2.3.4.5 are rotationally driven by drum motors 11, 12, 13.14, respectively, and are uniformly charged by a charging unit (not shown). Ma, Cy, Ye, Bk photosensitive drums 2,3°4.
5 is a laser beam 11 optically modulated by a video signal;
f2. #3. 14, each electrostatic latent image is formed on the drum and developed by a developing unit (not shown) to form a developed image.

Next, the developed image formed on the drum is fed from a paper feeding unit (not shown) and transferred at a predetermined timing onto copy paper that is electrostatically attracted to the transfer belt 1. The paper is transported in the direction of the arrow, fixed via a fixing unit, and then discharged.

Next, reading of the registration correction pattern image will be explained. Each photosensitive drum 2, 3. 4. 5
The pattern images visualized above are each transferred onto the transfer belt 1 at the timing shown in FIG. 4 and conveyed in the direction of the arrow in the figure. The transported pattern image is sequentially read by the CCD sensor 10 using an optical system consisting of an illumination lamp 6.7, a condensing lens 8, and a reflecting mirror 9.

FIG. 2 shows a block diagram of the image pattern reading and registration correction circuit. Pattern images of each color formed on the front and back sides of the transfer belt 1 as shown in FIG. 5 are read by CCD sensors 10a and 10b. Original oscillation clock I from the registration controller 20! 50
7. f 508 is the CCD driver 18. 19, and is necessary for driving the CCD sensors 10a and 10b. Lock (transfer pulse, reset pulse, shift pulse, etc.) i 501. f 502 is generated and the CCD 10a
.

IOb. The pattern image signals read by the CCD 10a, ]Ob are sent to the CCD driver 18. 19
Processing such as amplification, DC regeneration, and A/D conversion is performed by
Digital signal f 505. 1 506 to the registration controller 20. Each color pattern image signal received by the registration controller 20 is temporarily stored in memory, and under CPU control, the amount of registration deviation is calculated based on the pattern image of a certain color, and the electric current of each color scan and sub-scan is calculated. A pulse motor 23. which sends target image writing timing setting data 1509 to the system controller 21 and drives and controls a reflection mirror provided in the optical path for correcting changes in the optical path length and changes in the optical path of the recording laser beam. 24. 2
5. 26 pulse data 1511 is supplied to the mirror motor driver 22. In the mirror motor driver 22, each negative reflection mirror drive pulse motor 23. 24. 25. A current signal is supplied to 26, and the pulse motors 23, 24, 25, and 26 are driven to control the reflecting mirror. These registration corrections are performed by the activation signal I! from the system controller 21. Registration controller 20 by 510
is supplied and executed.

FIG. 3 shows a block diagram of an image pattern forming circuit for registration correction according to the present invention. Beam image obtained by scanning outside the image recording area with a laser beam
The H enable signal 1516 is generated by the main scanning enable signal generation circuit 27 using the (BD) signal β528 as a synchronization signal in the main scanning direction, and the image writing timing signal (I TOP) J2529 in the sub scanning direction generates a sub scanning enable signal. V enable signal 1517 by circuit 28
is formed. H, V enable signal I! 516.
An address signal 7531 is generated by the address counter 29 based on f517, and is supplied as a readout signal to the pattern RAM 30 in which the pattern image for registration correction is stored.

Pattern image signal A read out from pattern RAM
518 is then provided to selector 32. selector 32
The other input is the output signal I of the patch register 31.
2519 is connected, but this is because when a carbon black type toner is used as the Bk toner, the pattern image cannot be read in a reflective optical system because the carbon black absorbs light. Other colors (M a , Cy ) that reflect light there.

Ye) To form a solid pattern (patch) using one of the toners (Ye in this embodiment), and to form a pattern image for registration correction on this solid pattern, select the pattern image signal 1518 and the patch signal 1519. 32
Switch by. As the switching signal of this selector 32, C
The output signal 1526 from register 35 is used by the PU's data bus 1530.

In this embodiment, only Ye input is switched to the selector 32 and outputted to 1520. In the next selector 33, the normal image (VIDEO) f 52] is written or the pattern image I! 520 is written to the CPU data bus 75.
30, the output signal 7527 from the register 35 is used as the switching signal j1! 522 and is selectively output to γRAM3.
4, is supplied to the laser driver 38 via the gate 37, and is activated by the laser diode 39 in response to the input image signal 1525.
An optically modulated laser beam is output from.

FIG. 6 shows a flowchart of the initial registration correction mode (registration correction mode 1), and the initial registration correction mode will be explained in conjunction with FIG.

First, the first image pattern formation and reading are set (1). Next, the registration correction pattern image forming circuit shown in FIG. 3. A pattern image is written on the 4° 5 (2), the electrostatic latent image is developed and transferred onto the transfer belt 1 (3), and each color pattern image is sequentially conveyed to the pattern image reading position. The pattern image reading circuit shown in the figure reads the image (4), and the registration correction circuit reads the registration deviation data Di(M) for each color.

C, Y, K) are operated and calculated (5).

Next, determine whether the Nth image pattern formation, reading, and calculation of registration deviation data for each color have been completed 6).
Since the process is not completed, the second image pattern formation, reading, and registration deviation calculation mode for each color are set (7). When the Nth image pattern formation reading is performed in this way and the calculation of registration deviation data for each color is completed, the maximum value (MAX) and minimum value (MJN) are calculated from among the N pieces of registration deviation data for each color.
8), and compare the maximum value or minimum value with other registration deviation data in order to eliminate image pattern reading errors. The difference between the maximum value (MAX) and other registration deviation data (Di) is taken, and it is determined whether this is larger than a predetermined value (k) at the N-1 credit union (9). A predetermined value (k
), the maximum value (MAX) is determined to be an error in reading the image pattern, and is discarded from the registration deviation data (10). If any of the N-1 differences between the maximum value (MAX) and other registration deviation data is smaller than a predetermined value (k), the maximum value is left as is. Next, take the difference between the minimum value (MIN) and other registration deviation data (Di),
If the maximum value has been truncated, N-2, if the maximum remains, N-1, and it is determined whether all of them are larger than a predetermined value (k) (11). N-2 or N
-1 If it is determined that the minimum value (MIN) is larger than the predetermined value (k), the minimum value (MIN) is determined to be an error in reading the image pattern, and is discarded from the registration deviation data (1
2). If the difference between the minimum value (MIN) and other registration deviation data is smaller than the predetermined value (k) in any of N-2 or N-1, the minimum value is left as is (. Next, the maximum and minimum values are rounded down or the stored registration deviation data is averaged (step 13, calculate sub-scanning direction timing correction data for each color image signal (step 14)), and the main scanning direction Data Sera 1-L with timing correction data, (15)
, set the image writing timing in the main scanning and sub-scanning directions,
Exit the initial registration correction mode (16)
. Next, FIG. 7 shows a flowchart of the registration correction mode (registration correction mode 2) when replacing the drum and will be described.

First, it is determined whether or not the specific reference color (Cy in this case) has been replaced with a drum (17). Judgment result C
In the case of the y photosensitive drum, since it is the reference color for registration correction, it is necessary to perform registration correction for all colors, so proceed to registration correction mode l in Fig. 6 (1
8). If the drum was replaced with a color other than cy, registration correction is performed only for the color for which the drum was replaced. The steps here are basically the same, with the only difference being that the registration deviation calculation for all colors in Figure 6 is now the registration deviation calculation for the color for which the drum has been replaced. The explanation will be omitted.

[Other Examples]

In the description of the first embodiment of the present invention, the maximum value and minimum value of N pieces of registration deviation data are calculated, and the difference with other registration deviation data is calculated as N-1.
If the maximum value or minimum value is larger than a predetermined value (k) for all 7 or N-2 registration errors, the maximum or minimum value is rounded down, and the remaining registration deviation data is averaged to calculate the image writing timing correction data. As a second embodiment, a registration correction mode is used in which the difference between each registration/con deviation data is taken, and only those that are equal to or less than a predetermined value (k') are averaged to calculate image writing timing correction data. The process will be explained according to the flowchart shown in FIG.

In FIGS. 8 and 9, the same steps as in FIGS. 6 and 7 are given the same numbers. Furthermore, since the steps up to the calculation of N pieces of registration deviation data for each color are the same, the explanation will be omitted.

When the Nth calculation of the registration deviation data for each color is completed, the difference is then calculated for each of the N pieces of registration deviation data for each color (17).

(l Di-Dj t , i-]]~N-1.j=2
It is determined whether each difference value of ~N is smaller than a predetermined value (k') (18), and data for those smaller than the predetermined value (k') are saved. Next, the registration deviation data for each color is averaged (13), the sub-scanning direction timing correction data for each color image signal is calculated (14), and the data is set together with the main-scanning direction timing correction data (15). Set the scanning direction image writing timing and end the registration correction mode (16
).

As explained above, according to this embodiment, there is a pattern image forming means for forming a registration correction pattern image for each color on the transfer belt, and a means for reading the pattern image formed on the transfer belt for each color. a pattern image reading means, and a registration correction means for correcting each color/registration deviation based on a specific color based on the reading result of the pattern image reading means, and forming a pattern image on the transfer belt. , read this, and calculate registration deviation data for each color based on the reading results.This series of operations is performed multiple times, and registration correction for each color is performed according to data obtained by averaging multiple pieces of registration deviation data. This prevents deterioration of registration correction accuracy due to speed unevenness of the photosensitive drum and the transfer belt, and furthermore, by providing a unique data detection means for detecting unique data from among a plurality of pieces of registration deviation data, the unique data detection means can be improved. By discarding unique data based on the detection result and performing registration correction according to data obtained by averaging the remaining registration deviation data, it is possible to further improve registration correction accuracy.

Moreover, especially according to this embodiment, registration correction when replacing a photoreceptor other than a specific reference color is performed only for the color corresponding to the replacement photoreceptor, thereby reducing the calculation time for registration deviation data. It becomes possible.

Further, the present invention is not limited to image forming apparatuses using an electrophotographic process, but can also be applied to other recording apparatuses, such as inkjet recording apparatuses. The image forming member in this case corresponds to an inkjet head member.

Further, the present invention is particularly effective in a recording apparatus that records color images in a superimposed manner while conveying a recording material using a belt.

〔Effect of the invention〕

According to the present invention described above, registration correction can be performed with high accuracy and in a short time even when replacing an image forming member.

[Brief explanation of drawings]

FIG. 1 is a block diagram of the photosensitive drum and transfer belt for each color of the present invention, FIG. 2 is a block diagram of an image pattern reading and registration correction circuit, FIG. 3 is a block diagram of a pattern image forming circuit for each color, Figure 4 is the pattern image writing timing chart, Figure 5.
6 is a flowchart of the initial registration correction mode of the first embodiment; FIG. 7 is a flowchart of the registration correction mode when replacing the drum of the embodiment; FIG. 9 is a flowchart of the initial registration correction mode of the second embodiment, and FIG. 9 is a flowchart of the registration correction mode during drum replacement of the second embodiment. 1... Transfer belt 2, 3.4.5-Ma, Cy, Ye, Bk photosensitive drums 10a, 10b = CCD sensor 20... Registration controller 21...
System controller 22...Mirror motor driver 30...Pattern image RAM 38...Laser driver 39...Laser diode No. (J)

Claims (3)

[Claims] (1) A pattern image forming means having a replaceable image forming member for each color and forming a pattern image for registration correction, a pattern image reading means for reading the formed pattern image for each color, and the pattern and registration correction means for correcting misregistration of other colors using a predetermined color as a reference color based on the reading result of the image reading means, and when replacing the image forming member for the reference color and for the other colors. An image forming apparatus characterized by performing different registration corrections when replacing an image forming member. (2) The image forming apparatus according to claim 1, wherein when the image forming member for another color is replaced, registration correction is performed only on the replaced image forming member. (3) The image forming apparatus according to claim 1, wherein the image forming member is a photoreceptor.