JP2001083762A - Multicolor image forming device - Google Patents

Abstract

(57) [Problem] To accurately perform registration correction control by reducing registration mark detection errors caused by uneven rotation of an intermediate transfer member. SOLUTION: A registration mark 11 is formed on an intermediate transfer member 4 and detected by a detection sensor 5, and in response to the detection result, rotation unevenness of the intermediate transfer member 4 detected by a rotary encoder 8 is used as correction information. Used.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic or electrostatic recording type multicolor image forming apparatus such as a color copying machine or a color printer.
The present invention relates to a multicolor image forming apparatus that forms images of different colors by a plurality of image forming units.

[0002]

2. Description of the Related Art Conventionally, a multi-color image forming apparatus of this type has a plurality of image forming units, and irradiates a laser beam on a photosensitive drum as a photosensitive medium by an electrophotographic process to form an electrostatic latent image. The electrostatic latent image is formed, developed with a developer (toner), and the images of the respective colors are further superimposedly transferred onto an intermediate transfer body as an image carrier, and a recording paper as a recording material is intermediately transferred by a transfer belt. 2. Description of the Related Art There is known an apparatus that transfers a color image onto a recording sheet while conveying the image to a transfer section of a body to obtain a color image.

When this multicolor image forming apparatus is used, an image of each color is formed on each photosensitive drum, and when the image is transferred to a recording paper on a transfer belt via an intermediate transfer member, the transfer image position of each color is ideal. If the position deviates from the position, an image in which the color is changed is formed on the recording paper, and if the position further advances, an image in which the color is deviated is formed. These phenomena significantly degrade image quality.

For this reason, conventionally, a registration correction pattern image is formed on an intermediate transfer member from each photosensitive drum, and these are read by a CCD sensor or the like as detecting means, and are read on a photosensitive drum corresponding to an image of each color. Detecting the registration deviation of the laser beam, applying an electrical correction to the image signal to be recorded, and driving a reflection mirror provided in the laser beam optical path to correct the optical path length change or the optical path change. .

The registration correction pattern image is a line-shaped pattern drawn with yellow Y, magenta M, cyan C, black K, and toner of each color. The pattern of each color is based on a certain one color pattern. A general technique is to measure the time detected by the sensor and calculate how far the measured time deviates from the theoretical value to determine the amount of color misregistration.

A multi-color image forming apparatus of the type in which images of each color formed on each photosensitive drum are directly transferred to a recording material carried on a conveyor belt as an image carrier to obtain a color image. The technique for determining the amount of color misregistration is also applied to this. In this case, the registration correction pattern image is formed on the transport belt.

[0007]

However, the unevenness of rotation of the intermediate transfer member and the conveyor belt caused by the rotational accuracy and mechanical accuracy of the motor for driving the intermediate transfer member and the conveyor belt is a problem for registration correction. There are cases where the error is a factor when the sensor reads a pattern image.

Accordingly, it is an object of the present invention to provide a multicolor image forming apparatus capable of reducing a detection error of a registration correction pattern image caused by uneven rotation of an image carrier.

[0009]

The above object is achieved by a multicolor image forming apparatus according to the present invention. In summary, the present invention responds to image information signals transmitted from the outside,
Means for forming an image with a plurality of color toners by performing charging, exposure, development, and transfer to an image carrier a plurality of times, and a plurality of registration correction patterns created on the image carrier In a multicolor image forming apparatus having an image detection unit, a timer unit for measuring time, and a storage unit for sequentially storing a time until the registration correction pattern image is detected by the detection unit, Measuring means for measuring the rotation unevenness of the image carrier; correcting means for correcting the time information stored in the storage means using the rotation unevenness information of the image carrier; and the corrected time Information processing means for calculating the amount of positional deviation between images formed by the plurality of image forming means based on information. An image forming apparatus.

Preferably, the image forming means includes a semiconductor laser. According to another aspect, the image forming means preferably includes an LED. The plurality of color toners are
It is preferably a yellow, magenta, cyan or black toner. Preferably, the image carrier is an intermediate transfer member. According to another aspect, it is preferable that the image carrier at the time of normal printing is printing paper, and the image carrier at the time of creating the registration correction pattern image is a recording material transport belt.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a multicolor image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 A first embodiment of the present invention will be described with reference to FIGS.

First, the multicolor image forming apparatus of this embodiment will be schematically described with reference to FIG. As shown in FIG. 1, a multicolor image forming apparatus according to the present embodiment includes a photosensitive drum 1 serving as a photosensitive medium.
a, 1b, 1c, 1d, laser scanner unit 2
a, 2b, 2c, 2d, developing units 3a, 3b, 3c, 3
d, an intermediate transfer member (intermediate transfer belt) as an image carrier
4. A registration mark detection sensor 5 as a detecting means for detecting a registration mark as a registration correction pattern image, and a transfer for transferring a recording paper as a recording material and transferring a toner image on the intermediate transfer body 4 to the recording paper. Belt 6,
And a fixing device 7 for fixing the toner image on the recording paper to the recording paper by heat and pressure. Note that the laser scanner units 2a to 2d may be LEDs.

The intermediate transfer member 4 is stretched around a driving roller 4a, a tension roller 4b, and a secondary transfer opposing roller 4c, and is driven to rotate in the direction of the arrow in the drawing.

The photosensitive drums 1a to 1d, the laser scanner units 2a to 2d, and the developing units 3a to 3d correspond to yellow Y, magenta M, cyan C, and black K, respectively, and image information from a controller (not shown). In accordance with the signal, that is, the image data, the laser scanner unit 2
a to 2d scan on the photosensitive drums 1a to 1d to form electrostatic latent images, and visualize the electrostatic latent images as images with toner stored in the developing units 3a to 3d. Subsequently, the images formed on the respective photosensitive drums 1a to 1d are superimposedly transferred onto the intermediate transfer member 4 to form a color image, and the color image is transferred onto the recording paper conveyed by the transfer belt 6. Thereafter, the recording paper is conveyed to the fixing device 7, where the toner is melted by heat and pressed, so that the color image is completely fixed on the recording paper.

The formation of a registration correction pattern image, ie, a registration mark, is started when a start condition is satisfied, such as when the power is turned on, after a predetermined number of sheets are printed, or after a predetermined time has elapsed. That is, as shown in FIG. 2, four color registration marks 11 are printed on the intermediate transfer member 4 at regular intervals. Here, the four color registration marks 11 are arranged in the order of Y, M, C, and K from the top. Each of these registration marks 11 is detected by a registration mark detection sensor 5 as a detecting means, and each time T is detected from the detection of the first registration mark Y to the detection of other registration marks M, C, and K.
ym, Tyc, and Tyk are measured using timer means (not shown).

Each of the above times Tym, Tyc, Ty
For k, as shown in FIG. 3, these four registration marks Y, M, C, and K are taken as one set, a plurality of registration mark sets are measured, and the average time is adopted. In this embodiment, 6
Let us measure the set of resist mark sets. In this case, in short, there are six registration marks for each color. Here, by adding a number to the end of the registration mark measurement time Tym, Tyc, Tyk, it is possible to determine which set the time represented by the variable.

At this time, simultaneously, as shown in FIG. 4, a rotary encoder 8 as rotation unevenness measuring means is used.
Of the intermediate transfer member 4 is measured. The rotary encoder 8 includes a driving roller 4 a for driving the intermediate transfer body 4.
Is attached to the rotary shaft 4a1. The rotation shaft 4a1 is connected to the drive motor 9 via a gear train 10.

In this embodiment, the rotary encoder 8 is of a type that generates 360 pulses per rotation. The pulse generated by the rotary encoder 8 serves as a partition for dividing the rotational operation of the drive roller 4a into 360, and within this 360 section, how many finer clock pulses generated by a clock oscillator (not shown) exist. The rotation unevenness can be measured by doing or counting. This is shown in FIG.

In FIG. 5A, CP is a clock pulse,
(B) P is a pulse generated by the rotary encoder 9, and (c) is a predetermined section. When there are many clock pulses in a certain section, it means that the rotation of the intermediate transfer body was slow in that section, and conversely, when there were few clock pulses, the rotation of the intermediate transfer body was fast. Means.

FIG. 6 is a block diagram of a registration correction control circuit according to this embodiment.

The registration mark detection sensor 5 and the rotary encoder 8 are connected to the CPU 12 as information processing means, and a RAM 13 as storage means as a primary storage location of data and a control program are stored. The ROM 14 is connected.

The CPU 12 has a registration mark detection sensor 5
Detects the registration mark 11 and simultaneously obtains the rotation unevenness information at that time. This is shown in FIG.

If there are a plurality of sections divided by the pulse of the rotary encoder 8, the average is taken. As an example, when the time Tym from the detection of the Y registration mark to the detection of the M registration mark is measured, the rotation unevenness information section (b) corresponds to N to N + 2. Assuming that the average value of the obtained values is Nave and the theoretical value obtained when normal operation is performed is expressed by Nthe, the ratio can be obtained by calculating Nthe / Nave. This is set as rotation unevenness correction information Nym, Nyc, Nyk at that time. By adding a number to the end, it is possible to determine which registration mark set the correction information is for.

The registration mark measurement time Tymn, T
ycn, Tykn (n = 1 to 6) include correction information Nymn,
By multiplying Nycn and Nykn (n = 1 to 6), it is possible to calculate more accurate registration mark position information from which the influence of uneven rotation of the intermediate transfer member 4 has been removed. Letting these be ATym, ATyc, and ATyk, the calculation formula is as shown in the following formula (1). Here, as an example,
The measurement time between yellow and magenta was used as an example.

[0026]

(Equation 1) Here, the standard value STy stored in the CPU 12 in advance.
m, STyc, and STyk, and the difference is obtained.
Since the difference ΔT is used as registration deviation amount information, the timing of transmitting the Y, M, C, and K image signals is adjusted in accordance with this value.

As described above, according to this embodiment, the unevenness of rotation of the intermediate transfer member is detected, and the registration mark detection time is corrected to reduce the registration mark detection error. Can be performed more accurately.

Embodiment 2 In the first embodiment, the rotary encoder 8 is provided on the rotating shaft 4a1 of the drive roller 4a in the intermediate transfer member 4. In the second embodiment, as shown in FIG. The rotary encoder 8 is installed on the rotating shaft 9a of 9 and the rotation unevenness is measured.

The same effect as in the first embodiment can be obtained by performing registration correction control in the same manner as in the first embodiment.

Embodiment 3 Next, a third embodiment of the present invention will be described with reference to FIG. As shown in FIG. 9, the multicolor image forming apparatus according to the present embodiment directly transfers the images formed on the photosensitive drums 1a to 1d without using an intermediate transfer member. The image is transferred to the recording paper placed on the top.

A registration mark for registration correction is created on the transport belt 16 stretched between the driving roller 16a and the driven roller 16b, and the registration correction control is performed in the same manner as in the first embodiment.

The rotation unevenness of the conveyor belt 16 is shown in FIG.
The measurement is performed by a rotary encoder provided on the rotation shaft of the drive roller 16a, as described above.

In this embodiment, the same effects as in the first embodiment can be obtained.

Embodiment 4 In the third embodiment, the rotation unevenness of the conveyor belt 16 was measured by a rotary encoder provided on the rotating shaft of the drive roller 16a. In the fourth embodiment, the third embodiment shown in FIG. In the multicolor image forming apparatus of the embodiment, the driving roller 16
The measurement is performed by a rotary encoder provided on a drive shaft of a drive motor for driving the motor a.

In this embodiment, the same effect as in the above embodiment can be obtained.

[0036]

As is apparent from the above description, according to the present invention, the photosensitive medium is charged, exposed, developed, and transferred to the image carrier in response to the image information signal sent from the outside. Performing a plurality of times to form an image with a plurality of color toners, detecting means for a plurality of registration correction pattern images created on the image carrier, timer means for measuring time, Storage means for sequentially storing the time until the detection means detects the pattern image for registration correction, a measuring means for measuring rotation unevenness of the image carrier, and the storage means Correction means for correcting the time information stored in the means using the rotation unevenness information of the image carrier; and And information processing means for calculating the amount of positional deviation between the images formed by the plurality of image forming means, thereby reducing the detection error of the pattern image for registration correction caused by uneven rotation of the image carrier. Thus, registration correction control can be accurately performed. Therefore, a high-quality color image can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a multicolor image forming apparatus according to first and second embodiments of the present invention.

FIG. 2 is an explanatory diagram showing registration marks used in the first to fourth embodiments.

FIG. 3 is an explanatory diagram showing a plurality of registration mark sets used in the first to fourth embodiments.

FIG. 4 is an explanatory diagram showing an installation location of the rotary encoder according to the first embodiment.

FIG. 5 is a diagram for explaining a method for measuring rotational unevenness of an intermediate transfer member using the rotary encoder according to the first to fourth embodiments.

FIG. 6 is a block diagram of a registration correction control circuit in the first to fourth embodiments.

FIG. 7 is a diagram for explaining a relationship between registration mark position information and rotation unevenness information of an intermediate transfer member according to the first to fourth embodiments.

FIG. 8 is an explanatory diagram showing an installation location of a rotary encoder according to a second embodiment of the present invention.

FIG. 9 is a schematic configuration diagram illustrating a multicolor image forming apparatus according to a third embodiment of the present invention.

[Explanation of symbols]

1a, 1b, 1c, 1d Photosensitive drum (photosensitive medium) 4 Intermediate transfer body (image carrier) 5 Registration mark detection sensor (detection means) 8 Rotary encoder (rotational unevenness measurement means) 11 Registration mark (registration correction pattern image 12) CPU (information processing means) 13 RAM (storage means) 16 recording material transport belt (image carrier)

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 21/14 B41J 3/00 MH04N 1/29 G03G 21/00 372 F term (Reference) 2C362 AA03 BA52 BA70 BA71 CA23 CA39 CB47 CB80 2H027 DA17 DA38 EB04 EC03 EC06 EC20 ED02 ED06 ED24 EE02 EE03 EE04 EE07 EF09 2H030 AA01 AB02 AD12 AD17 BB02 BB16 BB23 BB42 BB44 BB56 2H032 BA01 BBDD DD03C07 DD08 GG02 GG12 GG14 HH02 HH04

Claims (6)

[Claims] An image is formed with toner of a plurality of colors by performing charging, exposure, development, and transfer to an image carrier of a photosensitive medium a plurality of times in response to an image information signal sent from outside. Means, detecting means for a plurality of registration correction pattern images created on the image carrier, timer means for measuring time, and until each of the registration correction pattern images is detected by the detection means. A storage unit for sequentially storing the time of the image carrier, a measuring unit for measuring the rotation unevenness of the image carrier, and the image carrier for the time information stored in the storage unit. A correcting unit that corrects using the rotation unevenness information, and a position between each image formed by the plurality of image forming units based on the corrected time information. Multi-color image forming apparatus, comprising: the information processing unit, a for calculating a is weight. 2. The multicolor image forming apparatus according to claim 1, wherein said image forming means includes a semiconductor laser. 3. The multicolor image forming apparatus according to claim 1, wherein said image forming means includes an LED. 4. The multicolor image forming apparatus according to claim 1, wherein the plurality of color toners are yellow, magenta, cyan, or black toner. 5. The multicolor image forming apparatus according to claim 1, wherein said image bearing member is an intermediate transfer member. 6. The image carrier during normal printing is a recording material, and the image carrier when forming the registration correction pattern image is a recording material transport belt. 1. A multicolor image forming apparatus.