JP2010097120A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To detect a resist mark formed on an intermediate transfer belt or a recording material conveying belt, to prevent erroneous detection caused by a flaw or contamination on the belt, when correcting the resist, and to accurately correct the resist. <P>SOLUTION: A resist sensor 9 detects a surface state of an image carrier or a transfer material carrier formed with the resist mark, and the resist mark for correcting the resist is formed based on a detection result, while overlapped with a portion regarded as an abnormal portion caused by at least one out of the flaw, irregularities and unevenness. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a printer, and a facsimile machine using an electrophotographic system, and more particularly to correction of the registration.

  Conventionally, as a color image forming apparatus, an electrostatic latent image is formed by irradiating a photosensitive drum, which is a photosensitive medium, with a laser beam by an electrophotographic process, and a plurality of image forming units for developing the electrostatic latent image are provided. However, those that form color images are known. That is, the multi-color images are superimposed and transferred onto an intermediate transfer belt (also referred to as an intermediate transfer member) that is an image carrier to obtain a color image, and the recording paper is sequentially conveyed to the image forming unit of the intermediate transfer belt, so that the color There is known an apparatus for obtaining a color image formed product by transferring an image onto a recording sheet. There is also an image forming apparatus of a type that has a structure very similar to this, and that directly transfers an image from a photosensitive drum to a recording sheet conveyed by a transfer belt for conveying the recording sheet, that is, a belt-shaped conveying unit.

  When this type of image forming apparatus is used, when an electrostatic latent image is formed on each photosensitive drum and transferred onto a recording sheet on an intermediate transfer belt or a recording material conveyance belt, the transfer image position of each color is shifted from the ideal position. The color changes on the intermediate transfer belt or the recording paper. As the degree further advances, an image with color misregistration is formed. These phenomena significantly degrade the image quality.

  For this reason, conventionally, registration marks formed on the intermediate transfer belt or the recording material conveyance belt from each photosensitive drum are read by an optical sensor, and a registration shift on the photosensitive drum corresponding to each color is detected. Then, the image signal to be recorded is electrically corrected according to the detection result, and the optical path length change is corrected by driving a reflection mirror provided in the laser beam optical path. Here, the registration marks refer to individual marks that are detected by an optical sensor, and the plurality of registration mark groups that are formed are referred to as registration correction pattern images.

  Various types of registration marks are considered. For example, in Patent Document 1, a first line segment and a second line arranged symmetrically with respect to the moving direction at a predetermined angle across a virtual line in the width direction perpendicular to the moving direction of the recording material conveyance belt or the intermediate transfer belt. A pattern consisting of minutes is proposed.

Also, as a registration correction method, by measuring the time when each color pattern is detected by the optical sensor with reference to a certain color pattern, and calculating how far the measured time is from the theoretical value. A method for determining the color misregistration amount is common. This is described in Patent Document 2, for example.
JP 2000-98810 A JP 2002-174992 A

  However, if unexpected dirt (unevenness) or scratches occur on the recording material conveyance belt or the intermediate transfer belt, the reflectance may change at this portion, or reflected light may not return to the optical sensor. For this reason, the optical sensor may erroneously detect this dirt or scratch as a registration mark. In some cases, two registration marks may be connected and erroneously detected as if they were one pattern. In particular, if the dirt or scratches are applied to the edge of the registration mark (the edge of the registration mark image), the detection result of the color misregistration amount of each color is incorrect, and there is a problem that the resist correction (color misregistration correction) cannot be performed accurately. .

  The present invention has been made under such circumstances. When the registration mark transferred on the image carrier or the transfer material carrier is detected and the resist is corrected, It is an object of the present invention to prevent misdetection due to dirt and realize accurate registration correction.

  In order to solve the above-described problem, in the present invention, an image forming apparatus is configured as described in (1) below.

(1) An image including detection means for detecting a registration mark for registration correction formed on an image carrier or transfer material carrier, and a correction means for performing registration correction based on a detection result by the detection means. In the forming apparatus, surface state detection means for detecting a surface state of the image carrier or the transfer material carrier on which the registration mark is formed;
Forming a registration mark for registration correction by superimposing the entire area of the portion regarded as an abnormal portion caused by at least one of scratches, unevenness and unevenness based on the detection result of the surface state detection means And an image forming apparatus.

  According to the present invention, when a resist mark transferred on an image carrier or a transfer material carrier is detected and the resist is corrected, an erroneous registration due to scratches or dirt on these belts can be prevented and an accurate resist can be obtained. Correction can be realized.

  Hereinafter, the best mode for carrying out the invention will be described in detail with reference to an embodiment of a color image forming apparatus.

  A “color image forming apparatus” that is Embodiment 1 will be described. In this embodiment, as a method of forming registration marks for registration correction superimposed on an abnormal portion of the intermediate transfer belt, a method of adjusting the timing for forming the registration marks on the intermediate transfer belt is used.

  FIG. 2 is a cross-sectional view illustrating a configuration of a main part of the color image forming apparatus according to the first embodiment.

  In this color image forming apparatus, in order to increase the speed of color image output, a plurality of photoconductors are stacked and toner images are sequentially transferred in a multiple manner (generally called a 4-drum tandem system).

  As shown in FIG. 2, the image forming apparatus includes a plurality of image forming units Y, M, C, and K (in order, a yellow unit, a magenta unit, a cyan unit, and a black unit), and passes through each image forming unit. An intermediate transfer belt 50 is provided. In each of the image forming units Y, M, C, and K, cylindrical photosensitive members (photosensitive drums) 1Y, 1M, 1C, and 1K as electrostatic latent image carriers are supported so as to be rotatable in the direction of the arrows. Yes. Reference numerals 2Y, 2M, 2C and 2K denote primary chargers, which are arranged to face the photosensitive drums 1Y, 1M, 1C and 1K, respectively. Reference numerals 3Y, 3M, 3C, and 3K denote laser exposure apparatuses, which respectively expose the photosensitive members to the primary chargers 2Y, 2M, 2C, and 2K on the downstream side in the rotation direction of the photosensitive drums 1Y, 1M, 1C, and 1K.

4Y, 4M, 4C, and 4K are developing units that store yellow, magenta, cyan, and black toners, respectively, and are adjacent to the photosensitive drum on the downstream side of the laser exposure devices 1Y, 1M, 1C, and 1K. Arranged to do so.
The intermediate transfer belt 50 is stretched and driven by three rollers: a driving roller 51, a tension roller 52, and a secondary transfer counter roller 53.

  The images made visible on the respective photosensitive drums 1 by the developing devices 4Y, 4M, 4C, and 4K are sequentially transferred onto the intermediate transfer belt 50 by the primary transfer rollers 6Y, 6M, 6C, and 6K, and are temporarily transferred to the intermediate transfer. A full color image is formed on the belt upside down. Thereafter, batch transfer (secondary transfer) is performed on the transfer material P by the secondary transfer roller 54. Transfer residual toner (waste toner) remaining on the intermediate transfer belt 50 is cleaned by the intermediate transfer belt cleaner 7.

  The operation of the image forming apparatus configured as described above will be described using the image forming unit Y as an example.

  The photosensitive drum 1Y has a light semiconductive layer on the surface of a conductive substrate such as aluminum, and rotates in the direction of arrow a. After the surface is uniformly negatively charged by the primary charger 2Y, exposure is performed by the laser exposure device 3Y to form an electrostatic latent image corresponding to the original. The developing device 4Y performs development using negatively charged toner, and forms a toner image corresponding to the electrostatic latent image on the surface of the photosensitive drum 1Y. The toner image formed on the surface of the photosensitive drum 1Y is transferred to the intermediate transfer belt 50 by the primary transfer roller 6Y.

  The above operation is performed in each image forming unit at a predetermined timing, and the toner image formed on each photosensitive drum is held on the intermediate transfer belt 50, and then transferred to the transfer material by the secondary transfer roller 54. All images are transferred to P.

  The transfer material P onto which the toner image has been transferred is supplied to the fixing device 8 and is fixed to the transfer material P by being heated and pressurized, and a full color image is obtained.

  Further, two optical sensors (hereinafter referred to as registration sensors) 9 for detecting registration are arranged opposite to the intermediate transfer belt 50 on the left and right (main scanning direction).

  Next, the configuration and characteristics of the registration sensor 9 will be described.

  As shown in FIG. 3, the registration sensor 9 includes a light emitting element 91 such as an LED and a light receiving element 92 such as a photodiode. Then, the infrared light from the light emitting element 91 is irradiated onto the registration pattern P on the intermediate transfer belt, and the regular reflection light therefrom is measured by the light receiving element 92 to detect the position of the registration pattern P. A curve A in FIG. 4 represents the output characteristics of the registration sensor 9, and the sensor output (the amount of light received by the photodiode 92) decreases as the amount of applied toner on the intermediate transfer belt increases. This is because when the amount of toner on the intermediate transfer belt increases, the irradiation light is diffused by the toner, and at the same time, the surface of the intermediate transfer belt, which is the base, is concealed and specularly reflected light from the intermediate transfer belt decreases. .

The main configuration and operation of the color image forming apparatus of this embodiment have been described above.
Next, a registration deviation amount detection method will be described.
FIG. 5 is an explanatory diagram showing the positional relationship between the registration sensor 9 and the pattern image for registration correction (hereinafter, registration pattern) in this embodiment. Two registration sensors 9 are arranged in the main scanning direction so that the registration patterns formed on the left and right on the intermediate transfer belt 50 can be detected. The registration patterns P-Y, P-M, PC, and P-K are registration patterns for detecting registration in the sub-scanning direction, and are sequentially formed with toners of yellow, magenta, cyan, and black. . The “<”-shaped registration patterns SY, SM, SC, and SK are registration patterns for detecting registration in the main scanning direction, and are sequentially registered in yellow, magenta, cyan, Formed with black toner.

A method for calculating the registration deviation amount using the registration mark will be described in detail with reference to FIGS. Here, the registration misalignment amount refers to a deviation amount from an ideal position or detection timing. An ideal position or detection timing is determined based on a certain standard. Examples of the reference include a reference position mark provided on the intermediate transfer belt, and a position or timing at which a reference color is detected.
First, registration detection in the sub-scanning direction will be described. In FIG. 6, P represents an actually formed registration mark for detecting registration in the sub-scanning direction, and P ′ represents a registration mark formed when the registration error is zero. Here, assuming that the timing at which the sensor detects the registration mark P is T and the timing at which the ideal registration mark is to be detected is T ′, the registration deviation dp in the sub-scanning direction can be calculated by the following equation.
dp = (T−T ′) × ps (ps is the moving speed of the intermediate transfer belt)

Next, registration detection in the main scanning direction will be described. In the figure, S represents a registration pattern for detecting registration in the main scanning direction that is actually formed, and S ′ represents a registration mark formed when the registration error is zero. The registration mark for detecting the registration in the main scanning direction is a “<”-shaped pattern composed of two lines intersecting at an angle of 90 degrees, and the angle of the line portion is 45 degrees with respect to the sub-scanning direction. is there. Since this registration mark passes through the registration sensor twice, the first passage timing is T1, and the second passage timing is T2. Similarly, assuming that the timing at which registration marks should be detected ideally is T1 ′ and T2 ′, the registration deviation ds in the main scanning direction can be calculated by the following equation.
ds = 1/2 × {(T2′−T1 ′) − (T2−T1)} × ps (ps is the moving speed of the intermediate transfer belt)

  Next, a method for detecting the time when the registration mark P has passed through the registration sensor 9 will be described with reference to FIG. FIG. 7A shows the sensor output when the registration mark passes the registration sensor 9. When the registration sensor 9 detects a mark other than the registration mark (intermediate transfer belt base), the amount of specularly reflected light incident on the light receiving member is large, so the sensor output is large and the sensor output is constant. When the registration mark passes through the registration sensor 9, the amount of specularly reflected light incident on the light receiving member by the toner decreases, and the sensor output decreases. Thereafter, the sensor output A is output as a digital signal B through a comparison circuit (not shown). In the figure, a dotted line C represents a threshold value of the comparison circuit, and an output signal B from the comparison circuit is turned on when the threshold value C is equal to or less. The center T of the ON signal portion is set as the registration mark detection timing.

The above is the detection method of the registration deviation amount in the image forming apparatus of the present embodiment.
In the registration correction, the image forming condition is corrected in accordance with the detected registration deviation amount. More specifically, Y, M, C, and K image signal transmission timings are adjusted as image forming condition correction.
In this example, only the effect on the registration error in the vertical direction (sub-scanning direction) has been described. However, the registration error in the main scanning direction, the main scanning magnification, the inclination in the main scanning direction (SKEW), and the like. The same effect can be obtained.
Next, a method for adjusting the timing for forming a registration mark on the intermediate transfer belt in the case of forming a registration mark for registration correction superimposed on an abnormal portion of the intermediate transfer belt, which is a feature of this embodiment Will be described with reference to the flowchart of FIG.

  STEP 1: The surface state on the intermediate transfer belt 50 is detected by the registration sensor 9.

  In advance, a home position determination sticker is pasted on an end of the intermediate transfer belt 50 that does not hinder image formation, and the home position of the intermediate transfer belt is recorded. Next, the intermediate transfer belt 50 is rotated once without printing any image. At that time, when viewed from the home position, the output characteristics at each position on the intermediate transfer belt 50 where each registration mark is to be formed are measured by the registration sensor 9, and if there is a position where the sensor output shows an abnormal value, It is judged that there is an abnormal part.

  As mentioned above, when unexpected dirt (unevenness), scratches, or irregularities occur on the intermediate transfer belt, the reflectivity changes drastically in the abnormal part or reflects on the optical sensor. The light will not return. In order to detect this reflection state, for example, the CPU 300 may determine whether the reflection intensity exceeds a threshold value, or determine whether the time during which the reflectance changes is equal to or greater than the threshold value. In this way, the position of the above part is specified by the analysis of the reflection state by the CPU 300.

  If it is determined that there is an abnormal part, the process proceeds to STEP 2. If there is no abnormal value, it is determined that there is no abnormal part and the process proceeds to STEP 3.

  STEP 2: The image writing timing is adjusted so that the registration mark is superimposed on the abnormal part.

FIG. 8 shows the planned formation positions of the respective resist marks when the control according to this embodiment is not performed. The abnormal part is on the edge of one registration mark. If each registration mark is detected in this state, the registration sensor 9 may be erroneously detected. From the position information of the abnormal portion on the intermediate transfer belt obtained in STEP 1, the timing for forming the registration mark on each color photosensitive drum so that the nearest registration mark overlaps the entire abnormal portion as shown in FIG. To decide.
STEP 3: Each registration mark is formed and each registration mark formed is detected by the registration sensor 9. When not passing through STEP 2, each registration mark to be detected by the registration sensor 9 is formed based on a predetermined timing for forming the registration mark on each color photosensitive drum. Then, based on the registration mark detection result, the CPU 300 performs registration correction.

  As described above, according to the present embodiment, the registration correction uses the fact that the output is lower than that on the intermediate transfer belt when each registration mark formed on the intermediate transfer belt is detected by the registration sensor. Thus, the registration deviation amount is calculated and corrected. For this reason, when an abnormal part such as a scratch on the intermediate transfer belt is detected by the registration sensor, the reflectance is reduced or the reflected light is not returned, so that the output of the sensor is lowered in the same manner as the registration mark. This leads to erroneous detection of the registration sensor. Therefore, by superimposing abnormal parts such as scratches in registration marks with reduced output characteristics, it is possible to suppress registration sensor misdetection and calculate the correct registration displacement amount, thereby improving registration correction accuracy. Is possible.

In this embodiment, the registration correction control in the intermediate transfer belt has been described. However, the same control can be performed in the recording material conveyance belt that functions as a transfer material carrier. In this case, the color image forming apparatus executes the same processing as described above for the registration marks formed on the transfer material carrier.
In the present embodiment, registration correction control in the sub-scanning direction has been described, but the same control can be performed in the main scanning direction.
Further, in FIGS. 8 and 9, a large pattern image is drawn in order to easily explain the difference in the resist pattern, but the actual ratio is an image that seems to be appropriate for the registration test as shown in FIG. The size is adopted.

The “color image forming apparatus” of Embodiment 2 is configured to be able to form a plurality of types of registration marks. Hereinafter, as a method of forming a registration mark, a method of registering a plurality of types of registration marks for registration correction and selectively forming an appropriate type of registration mark depending on the occurrence mode (position, shape, etc.) of the abnormal part Will be described.
Hereinafter, this embodiment will be described with reference to the drawings.
Note that the configuration, operation, and registration deviation amount detection method of the color image forming apparatus used in this embodiment are the same as those in the first embodiment, and descriptions of common configurations, operations, and methods are omitted.
The second embodiment is different from the first embodiment in that it has a plurality of registration correction registration marks, and is appropriate depending on the occurrence mode (position, shape, etc.) of the abnormal portion on the intermediate transfer belt. The type of registration mark is to be selected.

Next, features of this embodiment will be described with reference to the flowchart of FIG.
STEP 21: The surface state of the intermediate transfer belt 50 is detected by the registration sensor 9.
The detection method is the same as that in the first embodiment, and a description thereof will be omitted.
STEP 22: From a plurality of registration correction resist patterns, a registration mark to be superimposed over the entire abnormal portion is selected from a plurality of types of registration marks.

For example, when an abnormal portion on the intermediate transfer belt having a mode as shown in FIG. 11 is detected, the abnormal portion cannot be completely overlapped with the registration mark A, so the registration mark B as shown in FIG. 12 is selected.
STEP 23: Each resist mark is detected by the registration sensor 9 and each formed resist mark is detected. At this time, when the registration marks to be detected by the registration sensor 9 do not go through STEP 22, the normal registration marks shown in FIG. 11 are formed on the respective color photosensitive drums. Then, the CPU 300 performs registration correction based on the detection result of each registration mark.

In this embodiment, the registration correction control in the intermediate transfer belt has been described. However, the same control can be performed in the recording material conveyance belt.
In the present embodiment, registration correction control in the sub-scanning direction has been described, but the same control can be performed in the main scanning direction.
Further, in FIGS. 11 and 12, the resist marks are drawn larger in order to easily explain the difference between the resist marks, but the actual ratio is an image that seems to be appropriate for the registration test as shown in FIG. The size is adopted.

  As described above, according to the present embodiment, the same effect as in the first embodiment can be expected.

A “color image forming apparatus” that is Embodiment 3 will be described. In this embodiment, a method of moving a part of a pattern image for registration correction will be described as a method for forming a registration mark for registration correction superimposed on an abnormal portion of the intermediate transfer belt. The part of the pattern image for registration correction refers to a part of the registration marks among the plurality of registration marks.
Embodiments of the present invention will be described below with reference to the drawings.
Note that the configuration, operation, and registration deviation amount detection method of the color image forming apparatus used in this embodiment are the same as those in the first embodiment, and descriptions of common configurations, operations, and methods are omitted.
The third embodiment is different from the first and second embodiments in that a pattern image for registration correction is used as a technique for forming a registration mark for registration correction by superimposing it on an abnormal portion of the intermediate transfer belt. To move part of.

Next, features of the present invention will be described with reference to the flowchart of FIG.
STEP 31: The surface state on the intermediate transfer belt 50 is detected by the registration sensor 9.
The detection method is the same as that in the first embodiment, and a description thereof will be omitted.
STEP 32: Moves the formation position of a part of the pattern image for registration correction to overlap the entire abnormal part.

As shown in FIG. 14, when the abnormal part on the intermediate transfer belt is superimposed on the end of the registration mark for registration correction and there is a possibility of erroneous detection, as shown in FIG. A part of the pattern image is moved so as to be superimposed on the registration mark.
STEP 33: Each register mark is detected by the registration sensor 9 and each registration mark formed is detected. At this time, when the registration marks to be detected by the registration sensor 9 do not pass through STEP 32, normal registration marks as shown in FIG. 14 are formed. Then, based on the registration mark detection result, the CPU 300 performs registration correction.

In this embodiment, the registration correction control in the intermediate transfer belt has been described. However, the same control can be performed in the recording material conveyance belt.
In the present embodiment, registration correction control in the sub-scanning direction has been described, but the same control can be performed in the main scanning direction.
Further, in FIGS. 14 and 15, the registration marks are drawn larger in order to easily explain the difference between the registration marks, but the actual ratio is an image that seems to be appropriate for the registration test as shown in FIG. 5. The size is adopted.

  As described above, according to the present embodiment, the same effect as in the first embodiment can be expected.

6 is a flowchart illustrating the operation of the color image forming apparatus according to the first exemplary embodiment. Sectional drawing which shows the principal part in the color image forming apparatus of Example 1. Sectional view showing the configuration of the registration sensor Diagram showing the output characteristics of the registration sensor The figure which shows the positional relationship of a registration sensor and the pattern image for registration correction Illustration of cash register pattern detection method Explanatory drawing of registration deviation amount calculation method FIG. 6 is a diagram illustrating an abnormal portion on the intermediate transfer belt in Embodiment 1. The figure which shows the abnormal part countermeasure in Example 1 7 is a flowchart showing the operation of the color image forming apparatus according to the second embodiment. FIG. 10 is a diagram illustrating an abnormal portion on the intermediate transfer belt in the second embodiment. The figure which shows the abnormal part countermeasure in Example 2 7 is a flowchart showing the operation of the color image forming apparatus according to the third embodiment. FIG. 10 is a diagram illustrating an abnormal portion on the intermediate transfer belt in Embodiment 3. The figure which shows the abnormal part countermeasure in Example 3

Explanation of symbols

9 Cash register sensor 300 CPU

Claims (4)

An image forming apparatus comprising: a detection unit that detects a registration mark for registration correction formed on an image carrier or a transfer material carrier; and a correction unit that performs registration correction based on a detection result of the detection unit. ,
Surface state detection means for detecting the surface state of the image carrier or transfer material carrier on which the registration mark is formed;
Registration mark formation for forming a registration mark for registration correction by superimposing the entire area of the portion regarded as an abnormal portion caused by at least one of scratches, unevenness and unevenness based on the detection result of the surface state detection means Means,
An image forming apparatus comprising: The image forming apparatus according to claim 1,
The registration mark forming means adjusts the timing of forming the registration mark on the image carrier or transfer material carrier, and forms the registration mark so as to overlap the portion regarded as the abnormal portion. Image forming apparatus. The image forming apparatus according to claim 1,
The registration mark forming means can selectively form a plurality of types of registration correction registration marks, and the plurality of types of registration correction registration marks can be selected according to the occurrence of the abnormal portion. An image forming apparatus, wherein a registration mark that can be formed over an entire abnormal portion is formed. The image forming apparatus according to claim 1,
The registration mark forming means forms a pattern image for registration correction composed of a plurality of registration marks, and further superimposes on the abnormal portion by moving a part of the plurality of Gilest marks. Forming a pattern image for registration correction.

Images