JP2003167408A - Color image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a color image forming apparatus capable of properly correcting color slurring between respective colors by accurately detecting an image for measuring color slurring amount. <P>SOLUTION: This color image forming apparatus 100 is provided with a means 40 for controlling the image forming position of a developer image in a plurality of colors by image forming means PY to PBk based on each of positional information obtained by detecting color slurring measuring images in a plurality of colors 601 to 620 consecutively formed on a carrying means 30 by the image forming means PY to PBk by using a detection means 50. In the apparatus 100, at least one of the consecutive images 601 to 620 is set as a reference image 601 and formed to be thicker in the moving direction of the carrying means than other images 602 to 620. Based on the positional information of the reference image 601 detected by the detection means 50, the range of the respective detecting positions of the other images 602 to 620 by the detection means 50 is estimated. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image forming apparatus such as a copying machine or a printer which uses an electrophotographic system or an electrostatic recording system.

[0002]

2. Description of the Related Art Conventionally, an electrostatic latent image is formed on an image carrier by an electrophotographic system or an electrostatic recording system, and the electrostatic latent image is developed as a toner image by a toner included in a developer by a developing device. There is an image forming apparatus that obtains an image by transferring a toner image onto a recording material.

In particular, as a color image forming apparatus for forming a color image at a high speed, a drum type electrophotographic photosensitive member (hereinafter referred to as "photosensitive drum") is provided as an image bearing member along a conveyor belt. Are arranged to form images of yellow (Y), magenta (M), cyan (C), and black (Bk) on the plurality of photosensitive drums, respectively, and the respective colors are formed on the recording material conveyed by the conveyor belt. There is a so-called tandem system in which the images of are sequentially transferred to a recording material.

A tandem type color image forming apparatus will be described with reference to FIG. FIG. 5 shows a schematic configuration of a laser beam printer as a tandem type color image forming apparatus 100. The tandem-type color image forming apparatus 100 forms a plurality of colors on a transfer target, in this example, a yellow image (Y), a magenta image (M), a cyan (C) image, and a black image (Bk). As an image forming means,
The image forming units PY, PM, PC and PBk are provided. Here, since the configurations of the image forming units PY to PBk are the same except for the color of the developer, the suffix Y indicating that the components of the image forming units PY to PBk of each color are provided unless particularly distinguished. , M, C and Bk are omitted.

In each of the image forming sections PY to PBk,
A photosensitive drum 18, a charging roller 16 as a charging means for uniformly charging the photosensitive drum 18, a laser scanner unit 11 as an exposing means for irradiating the laser beam 13 to form a latent image on the photosensitive drum 18, A developer (toner) is supplied to the latent image to visualize it as a developer image (toner image). The developing device 14 is a developing unit. The transfer roller is a transfer unit that transfers the toner image formed on the photoconductor drum 18 onto a transfer sheet. 19, a cleaning device 15 as a cleaning unit for removing the developer remaining on the photosensitive drum 18, and the like are provided. The developing device 14 includes a developing roller 17 that supplies the developer in the developing device to the photosensitive drum 18.
The cleaning device 15 that cleans the photosensitive drum 18 and the charging roller 16 that performs the primary charging are unitized as a block 12.

A recording material S, such as a recording paper or an OHP sheet, is supplied from the recording material cassette 22 or the manual feed tray 28 into the apparatus. The recording material S in the recording material cassette 22 is
It is sent out by the cassette pickup roller 20a. The recording material S in the manual feed tray 28 is sent out by the manual feed pickup roller 20b. The recording material S sent out stands by at the registration rollers 21 in order to keep timing with the image forming units PY to PBk.

A first registration sensor (registration sensor) 24 for detecting the leading end of the supplied recording material S is provided near the registration roller 21.
The image forming control unit (controller) 40 (FIG. 6) that controls the image forming units PY to PBk includes the first registration sensor 24.
The leading edge of the recording material S is detected by the registration roller 2 according to the detection result of
The timing of reaching 1 is detected, and the image of the first color (yellow in the illustrated example) is formed on the photoconductor drum 18Y. At the same time, the controller 40 controls the temperature of a heater (not shown) included in the fixing device 23 so as to reach a predetermined temperature.

A suction roller 29 is provided adjacent to the registration roller 21. By applying a suction bias to the shaft of the suction roller 29, the recording material S is electrostatically attracted onto the transport belt 30 as a transport unit.

The recording material S which is on standby by the registration roller 21.
At the timing of the detection result of the first registration sensor 24 and the image forming process of the first color,
The image of the first color is transferred onto the recording material S by being transferred on the transfer belt 30 which is arranged so as to pass through PBk and by applying a transfer bias to the transfer roller 19. The conveyor belt 30 includes the conveyor belt support roller 3
It is supported by 1 and 32, and orbits in the direction of the arrow in the figure.

Similarly, the image of the second color (magenta in the illustrated example) is conveyed by the conveyor belt 3 at the timing of the detection result of the second registration sensor 25 and the image forming process of the second color.
0 is superimposed and transferred onto the image of the first color on the recording material S which is conveyed over 0.

Thereafter, similarly, the third color image (cyan color in the illustrated example) is the detection result of the third registration sensor 26, and the fourth color image (black in the illustrated example) is the detection result of the fourth registration sensor 27. On the basis of the above, the images are sequentially superimposed and transferred onto the recording material S at a timing with each image forming process.

The fixing device 23 melts and fixes the recording material S on which the four-color developer images have been transferred, while being conveyed. Fixing device 23
Includes a fixing roller 35 that heats the recording material S, and a pressure roller 36 that brings the recording material S into pressure contact with the fixing roller 35. The fixing roller 35 is formed in a hollow shape and has a built-in heater for heating the recording material S. That is, 4
The recording material S on which the color developer images are transferred is fixed to the fixing roller 35.
The toner is fixed on the surface of the recording material S by being conveyed by the pressure roller 36 and subjected to heat and pressure.

Thereafter, the recording material S on which the toner is fixed
Is discharged out of the plane. The surface of the photoconductor drum 18 after the image is transferred to the recording material S is removed by the cleaning device 15 such as transfer residual toner. In this way, the image forming operation is completed.

Conventionally, the tandem type color image forming apparatus as described above has a position deviation (color deviation) correcting means for correcting the deviation of the image forming position in each of the image forming portions PY to PBk.

That is, referring to FIG. 6, the color image forming apparatus 100, prior to forming a color image, includes yellow (Y), magenta (M), cyan (C), and black (Bk). In order to remove the color shift between the colors, the color shift correction between the colors is performed.

First, an image (toner pattern) (hereinafter, simply referred to as “toner pattern”) 60 for measuring the amount of color misregistration is formed on the surface of the conveyor belt 30. As will be described in detail later, the toner pattern 60 generally has a recording material S conveyance direction (circulation movement direction of the conveyance belt 30),
It has a separate pattern in the scanning direction.

The toner pattern 60 is the toner detection sensor 5
Detected by 0. The toner detection sensor 50 is installed on the end of the image forming area of the conveyor belt 30 (the end portion in the direction orthogonal to the revolving movement direction) on the fixing device 23 side in the recording material conveying direction of the conveyor belt 30. . The toner detection sensor 50 usually has an optical sensor including a light emitting element such as an LED as a light emitting section and a light receiving element such as a PD as a light receiving section. Then, the reflected light of the light applied to the surface of the conveyor belt 30 by the light emitting element is detected by the light receiving element, and the position of the toner pattern (hereinafter, referred to as “toner position”) is detected by the amount of the reflected light.

To explain further, the toner detection sensor 50
Detects a toner pattern of each color as a light intensity distribution waveform by an optical sensor equipped with an optical semiconductor element and outputs it as a voltage signal. The voltage signal indicates that each image forming unit PY ...
It is sent to the CPU 41 of the image forming control unit (controller) 40 which is a control means for controlling the operation of the PBk, calculating the amount of color shift, controlling the image forming position of each color image, and the like. The CPU 41 calculates the color shift amount from the voltage signal,
The color misregistration correction value is transmitted to the RAM 42. And R
Based on the color misregistration correction value stored in the AM 42, the write timing of each color is reset to make it difficult for color misregistration between the colors to occur.

The color misregistration correction operation will be described in more detail with reference to FIGS. 7 and 8.

Step 1: (Cleaning Sequence Execution) First, in order to accurately detect the color misregistration between the respective colors, the toner remaining on the conveyor belt 30 is removed. For example, as shown in FIG. 5, a cleaning blade 37 is provided on the conveyor belt 30, and the adhered toner is scraped off and removed as the conveyor belt 30 rotates.
The conveyor belt 30 is cleaned. The removed toner is stored in a waste toner container 38 provided below the cleaning blade 37.

Step 2: (LED light quantity constant control) Further, in order to accurately detect the color misregistration, the conveyor belt 30 is used.
It is necessary to make constant the amount of light of the LED 51 as a light emitting element that irradiates light on the surface of the. In order to make the amount of light emitted from the LED 51 constant, a PD 53 for reference light is installed as a reference light receiving element close to the LED 51. When the reference light PD 53 receives the light emitted from the LED 51, a current proportional to the amount of received light flows through the reference light PD 53. FIG. 9 shows the relationship between the received light amount and the PD current value. PD for reference light
When a current flows through the resistor 53, a voltage value proportional to the current value is applied to the resistor R connected in series with the reference light PD 53.
Occurs on both ends of 2. This voltage value is amplified to a voltage value V1 via the amplifier 55, and V1 is input to the light amount control circuit 43.

In the light quantity control circuit 43, a voltage value V0 for keeping the light quantity constant is preset. The light quantity control circuit 43 compares the input V1 and V0, and V1> V0
If so, a Low (L) signal is output and V1 <V0
If so, a High (H) signal is output. The L signal and the H signal are input to the LED current control circuit 57 so that the current flowing through the LED 51 is reduced when the L signal is input, and the current flowing through the LED 51 when the H signal is input. Work to increase. This constant light amount control is loop control, and the LED 51
It monitors the amount of light and works so that the amount of light is constant.

Step 3: Toner pattern detection In order to detect the amount of color misregistration between the colors, the toner on the conveyor belt 30 is detected.
A toner pattern 60 is formed on the surface. Then, the position of the toner pattern 60 is detected by the toner detection sensor 50,
The color shift amount is detected based on the result.

As described above, the toner detection sensor 50 has the light emitting element (LED) 51 and the light receiving element (PD) 52, and the PD 52 detects the reflected light of the light irradiated on the surface of the conveyor belt 30 by the LED 51. The toner position is detected based on the reflected light amount. That is, a current proportional to the amount of received light flows through the PD 52. A voltage value proportional to this current value occurs across the resistor R1 connected in series with the PD 52. This voltage value is amplified to a voltage value V2 (described later) via the amplifier 54 and input to the reflected light amount determination circuit 56.

Here, referring also to FIG. 10 and FIG.
A method of detecting the toner pattern 60 will be described.

As shown in FIG. 10, the toner pattern 60 formed on the conveyor belt 30 is transferred to the toner detection sensor 50.
When it is detected by, as shown in FIG.
The voltage value output from the amplifier 54 when the toner is not on the surface 0 is Va. However, when the conveyor belt 30 rotates and the toner pattern 60 reaches the lower surface of the toner detection sensor 50 (the point where light is emitted), the voltage value of the voltage waveform V2 output from the amplifier 54 gradually decreases, Finally, it converges to the voltage value Vb.

Voltage waveform V2 output from the amplifier 54
Is input to the reflected light amount determination circuit 56. The reflected light amount determination circuit 56 includes a threshold value TH for measuring the reflected light amount.
1 is set. The reflected light amount determination circuit 56 compares the input voltage value V2 with the threshold value TH1, and V2> T
When it is H1, the L signal is input, and when V2 <TH1, the H signal is A / D converted and input to the CPU 41. As a result, the conveyor belt 30 rotates and the toner detection sensor 50
When the toner pattern 60 passes under the
A pulse waveform A as shown in FIG. 11 is input to 1. The CPU 41 calculates the center tm between the rising time t1 and the falling time t2 of the pulse waveform A, and recognizes the time tm as the toner position.

Step 4: Color shift amount calculation toner patterns 60 are formed on the transport belt 30 at predetermined intervals for each color of yellow (Y), magenta (M), cyan (C), and black (Bk). . The toner pattern 60 is usually a pattern for detecting color misregistration in the transport direction (direction in which the transport belt 30 rotates),
And a pattern for detecting a color shift in the exposure scanning direction of the laser scanner 11 as an exposure unit. 12
FIG. 12A shows an example of the toner pattern 60a for detecting color misregistration in the carrying direction, and FIG. 12B shows an example of the toner pattern 60b for color misregistration detection in the scanning direction.

First, the color misregistration between the respective colors in the carrying direction of the carrying belt 30 is detected by the toner pattern 60 for detecting the color deviation in the carrying direction.
Use a to detect. For the toner pattern 60a for detecting color misregistration in the carrying direction, a reference color is set (for example, cyan),
The toner patterns 60a1 and 60a2 for detecting the color misregistration in the carrying direction of the reference color and the detected color (other than cyan) are detected to measure the color misregistration amount.

Specifically, as shown in FIG.
The color shift amount is obtained from the time interval between the time when the reference color toner pattern 60a1 is detected and the time when the detected color toner pattern 60a2 is detected. Let REFV be the time interval when no color shift occurs, and let ΔV be the actually measured time interval. The color misregistration amount is obtained by the color misregistration amount = ΔV−REFV.

Next, the color misregistration amount between the respective colors in the scanning direction is detected by using the scanning direction color misregistration detection toner pattern 60b. The toner pattern 60b for detecting color misregistration in the scanning direction is
A reference color is set (for example, cyan color), and the color misregistration amount is measured by detecting the scanning direction color misregistration detection toner patterns 60b and 60b2 of the reference color and the detected color (other than cyan color).

Specifically, as shown in FIG. 13 (b),
The time interval between the time interval ΔH1 between the line portion of the reference color toner pattern 60b1 extending in the horizontal direction in the figure and the diagonally intersecting diagonal line portion and the time interval ΔH2 between the similar portions of the detected color toner pattern 60b2. The color shift amount is calculated from the difference. Toner pattern 60b1 of the reference color actually measured
Is set to REFH (ΔH1), and the time interval of the toner pattern 60b2 of the detected color actually measured is ΔH2.
Then, the color misregistration amount is obtained by the color misregistration amount = (ΔH2−REFH) / 2 (where REFH = ΔH1).

Step 5: Before Setting Color Misregistration Correction Value The calculation result of the color misregistration amount in the scanning direction obtained in step 4 is sent to the image forming controller (controller) 40, and the calculation result of the color misregistration amount in the carrying direction is obtained. It is transmitted to the RAM 42.
Here, the calculation result of the color misregistration amount in the transport direction is subtracted from the color image formation timing currently set in the RAM 42, and new color image formation timing is set and stored. Then, at the next image formation or at the time of executing the color shift detection sequence, the image formation timing newly set in the RAM 42 is performed.

As described above, each image forming unit P is conventionally used.
The image forming positions Y to PBk are corrected to prevent color misregistration.

[0035]

However, when the toner pattern 60 is detected in order to correct the color misregistration between the colors of yellow (Y), magenta (M), cyan (C) and black (Bk), for example, If the transport belt 30 is damaged, the damage may be detected as the toner position.

Further, due to variations in the amount of toner applied on the toner pattern 60, the toner pattern 60 may not be detected, resulting in omission of pattern detection. If color misregistration correction is performed without considering such a pattern detection failure, the color misregistration correction accuracy may deteriorate.

In the above description, the color image forming apparatus in which the toner image is transferred from the photosensitive drum to the recording material conveyed on the conveyor belt has been described as an example, but the same problem occurs in the intermediate transfer type color image forming apparatus. Exists. The intermediate transfer type color image forming apparatus includes, as an intermediate transfer member, for example, a drum-shaped intermediate transfer drum in which a sheet is stretched over a frame, and the intermediate transfer member is provided with a plurality of colors from the photosensitive drum. After multiple transfer of toner images, the toner images are collectively secondarily transferred to a recording material to form a color image. Even in such an intermediate transfer type image forming apparatus, in order to correct the positional deviation (color misregistration) of the toner images of a plurality of colors which are superposed on the intermediate transfer body, the toner is formed on the intermediate transfer body in the same manner as in the case of the above-mentioned transport belt. A pattern is formed and this is detected.

Therefore, an object of the present invention is to provide a color image forming apparatus capable of accurately detecting an image for measuring color misregistration and appropriately performing color misregistration correction between respective colors.

Another object of the present invention is to detect a scratch on the surface of a transfer target such as a conveyor belt or an intermediate transfer member as a position of the developer, or to detect a color misregistration amount image due to a color defect. It is an object of the present invention to provide a color image forming apparatus capable of preventing deterioration of misregistration correction accuracy and detecting a color misregistration amount measurement image with high accuracy.

[0040]

The above object can be achieved by a color image forming apparatus according to the present invention. In summary, the present invention forms an image of a developer having different colors on a plurality of image bearing members, and transfers the developer to form an image of a developer having a plurality of colors on a transfer target. Means; conveying means for conveying the recording material, to which the developer is transferred from the plurality of image carriers, to the plurality of image carriers, and detecting means for detecting positional information of the developer image on the conveying means And a plurality of image forming means based on respective position information obtained by detecting the color shift measuring images of a plurality of colors continuously formed on the conveying means by the image forming means by the detecting means. A means for controlling the formation position of the color developer image; and at least one of the continuous color misregistration measurement images as a reference image,
It is formed thicker in the moving direction of the conveying means than the other color misregistration measurement images, and based on the position information of the reference image detected by the detection means, each of the other color misregistration measurement images by the detection means. A color image forming apparatus characterized by estimating a detection position range.

According to another aspect of the present invention, developer images of different colors are sequentially formed on the image carrier, and the developer images are transferred to form a plurality of color developer images on the transfer target. Image forming means for forming; an intermediate transfer body on which a developer image is sequentially transferred from the image carrier; a detecting means for detecting positional information of the developer image on the intermediate transfer body; the image forming means Based on the respective position information obtained by detecting the color shift measuring images of a plurality of colors continuously formed on the intermediate transfer member by the detecting means, the plurality of color developer images by the image forming means Means for controlling the formation position of;
In the color image forming apparatus having the above, at least one of the continuous color misregistration measurement images is used as a reference image, and is formed thicker in the moving direction of the intermediate transfer member than the other color misregistration measurement images, and the detection unit A color image forming apparatus is provided, which estimates the detection position range of each of the other color misregistration measurement images by the detection unit based on the position information of the reference image detected by.

According to each of the above embodiments of the present invention, the reference image is located at the head of the continuous color misregistration measurement images in the order of detection by the detection means.

According to each of the other embodiments of the present invention, from the detection time information as the position information of the reference image detected by the detecting means, each of the other color shift images of the continuous color shift measuring image is detected. The detection time information as the detection position range of is calculated.

In each of the above inventions, according to one embodiment, when the detection means detects a developer image outside the detection position range, the detection signal is not used for controlling the image forming position. According to another embodiment, when the detection unit detects a plurality of developer images in one of the detection position ranges, a detection signal within the detection position range is used for controlling the image forming position. Not in. Furthermore, according to another embodiment, in each of the detection position ranges, when the detection unit does not detect any developer image,
Within the detection position range, it is determined that there is a detection error of the color shift measurement image.

According to each of the other embodiments of the present invention, an optical semiconductor element is used as the detecting means. Further, the detecting means reflects the light emitting portion that irradiates the surface of the conveying means or the intermediate transfer body with light, and the surface of the conveying means or the intermediate transfer body, or the developer image on the conveying means or the intermediate transfer body. A light receiving unit that receives light is used.

According to each of the other embodiments of the present invention, the color image forming apparatus has a plurality of the detecting means.

[0047]

DETAILED DESCRIPTION OF THE INVENTION A color image forming apparatus according to the present invention will be described in more detail with reference to the drawings.

Embodiment 1 In this embodiment, the present invention is applied to the color image forming apparatus described with reference to FIG. Since the overall configuration and operation of the color image forming apparatus and the basic configuration and operation of the color misregistration correction unit are the same as those described above, elements having the same function and configuration will be assigned the same reference numerals and overlapping description will be omitted.

Image for measuring color shift amount (toner pattern) 6
The detection method of 0 is basically the same as the above-mentioned conventional one,
The conveyor belt 30 is irradiated with light, and when the reflected light amount falls below a predetermined amount, it is detected as the toner pattern 60. Therefore, if there is residual toner remaining on the transport belt 30, it is necessary to remove it, and the transport belt 30 is first cleaned. In order to clean the conveyor belt 30, for example, a cleaning blade 37 is provided on the conveyor belt 30, and the toner adhered by the rotation of the conveyor belt 30 is scraped off and removed. The removed toner is stored in a waste toner container 38 provided below the cleaning blade 37.

The method of detecting the toner pattern 60 in this embodiment will be described below with reference to the flowchart of FIG.

Step 1: (Start of toner pattern detection sequence) After the cleaning of the conveyor belt 30 is completed, the toner pattern 60 is formed on the surface of the conveyor belt 30. The toner pattern 60 has separate patterns for detecting color misregistration in the conveyance direction of the recording material S and the scanning direction. Figure 12 (a)
12A is an example of a toner pattern 60a for detecting color misregistration in the carrying direction for detecting color misregistration in the carrying direction, and FIG. 12B shows a toner pattern 60b for detecting color misregistration in the scanning direction for detecting color misregistration in the scanning direction. An example is shown.

Here, in order to facilitate understanding of the present invention, a case where a plurality of transport direction color misregistration detection patterns, which are straight lines extending in a direction substantially orthogonal to the transport direction of the recording material S, are formed. As described below. Although described later in detail, in the present embodiment, a case will be described in which a pattern set 600 including a plurality of (20) toner patterns as shown in FIG. 1 is formed (hereinafter, reference numerals 601 to 602 denote toner detection sensors, respectively). The toner patterns of the first to twentieth toners are shown in the detection order of 50). But,
As will be easily understood by those skilled in the art from the following description, the principle of the present invention is that a toner pattern of any shape, such as a scanning direction color misregistration detection pattern having a shape as shown in FIG. The same effects as those described below can be obtained.

In this embodiment, the toner patterns 601 to 620 forming the pattern set 600 are all formed of the same color toner. Further, the same pattern set is formed for toners of other colors, and the toner position of each toner pattern of the pattern set formed by the toners of each color is detected as described in detail below. Then, the toner patterns 601 to 62 of the reference color pattern set 600 are
Based on 0, the toner position of each toner pattern of the desired color pattern set is detected.

Step 2: (Detection of Toner Position of First Toner Pattern) Toner pattern 601 formed on the transport belt 30
When the transport belt 30 moves (circulates), 620 passes below the toner detection sensor 50 arranged above the transport belt 30, and is detected as a toner position.

The toner detection sensor 50 detects the toner patterns 601 to 620 in the same manner as described above. That is,
The toner detection sensor 50 includes a light emitting element (L
ED) 51 and a light receiving element (PD) 52 as a light receiving portion. Then, the PD 52 detects the reflected light of the light emitted to the surface of the conveyor belt 30 by the LED 51,
The toner position is detected based on the reflected light amount.

As described above, as shown in FIG. 10, the toner patterns 601 to 62 formed on the conveyor belt 30.
When 0 is detected by the toner detection sensor 50, as shown in FIG. 11, the voltage value of the voltage waveform V2 output from the amplifier 54 is Va when toner is not placed on the conveyor belt 30. However, when the conveyor belt 30 rotates and the toner patterns 601 to 620 reach the lower surface of the toner detection sensor 50 (the point where light is emitted), the voltage value output from the amplifier 54 gradually decreases, and finally. It converges to the voltage value Vb.

Voltage waveform V2 output from the amplifier 54
Is input to the reflected light amount determination circuit 56. The reflected light amount determination circuit 56 includes a threshold value TH for measuring the reflected light amount.
1 is set. The reflected light amount determination circuit 56 compares the input voltage value V2 with the threshold value TH1, and V2> T
When it is H1, the L signal is input, and when V2 <TH1, the H signal is A / D converted and input to the CPU 41. As a result, the conveyor belt 30 rotates and the toner detection sensor 50
When the toner patterns 601 to 620 pass under the, the pulse waveform A as shown in FIG. 11 is input to the CPU 41.

In this embodiment, this pulse waveform A
Of the rising time t1 and the falling time t2 (t
2-t1) is calculated by the CPU 41, and when the calculation result is larger than a predetermined value, the first toner pattern 6 in the conveyance direction of the recording material S, that is, the first toner pattern 6
It is recognized as 01.

In this embodiment, the length of the first toner pattern in the moving direction of the conveyor belt 30 (hereinafter referred to as "pattern width") is determined by the other toner patterns 602 to 620.
To be thicker than Then, when the calculated time from t1 to t2 is obviously longer than the toner patterns 602 to 620 after the second toner, it is recognized as the first toner pattern 601. In this embodiment, the pattern width of the first toner pattern 601 is 100 dots, and the pattern width of the second and subsequent toner patterns 602 to 620 is 50 dots.
I am trying.

Further, the center tm1 ((t
1 + t2) / 2) is calculated by the CPU 41, and the time tm
1 is recognized as information indicating the toner position p1 of the first toner pattern 601. The time tm1 is stored in the RAM 42.

Step 3: (estimate the toner positions of the second and subsequent toner patterns from the toner position of the first toner pattern) The toner patterns 601 to 620 have a predetermined pattern width,
A pattern set 600 having a predetermined number and a predetermined interval is preset. In this embodiment, as shown in FIG.
The pattern width of the first toner pattern 601 is 100 do
t, the pattern width of the second and subsequent toner patterns 602 to 620 is 50 dot, the number of patterns is 20, and the interval between adjacent toner patterns (hereinafter referred to as “pattern interval”) is set to 100 dots.

Therefore, when the toner position p1 of the first toner pattern 601 is determined in the previous step 2, the toner positions p2 to p20 of the second and subsequent toner patterns can be estimated.

Specifically, in the previous step 2, the pulse waveform A
When recognizing the toner position p1 of the first toner pattern 601, the second and subsequent toner patterns 602 to 62 are detected.
The toner positions p2 to p20 of 0 are: p2 = p1 + 175dot p3 = p2 + 150dot p4 = p3 + 150dot ... .

When the transport speed (moving speed) of the transport belt 30 is 100 mm / s, the time tm at which the center positions of the second and subsequent toner patterns 602 to 620 pass the toner detection sensor 50 is: tm2 = tm1 + 25.4 × 175 / (600 × 100) ≈tm1 + 0.0741s tm3 = tm2 + 25.4 × 150 / (600 × 100) = tm2 + 0.0635s tm4 = tm3 + 25.4 × 150 / (600 × 100) = tm3 + 0. 0635s ... tm20 = tm19 + 25.4 × 150 / (600 × 100) ≈tm19 + 0.0635s or tm2 = tm1 + 25.4 × 175 / (600 × 100) ≈tm1 + 0.0741s tm3 = tm1 + 25.4 × 325 /(600×100)≈tm1+0.1 76s tm4 = tm1 + 25.4 × 475 / (600 × 100) ≒ tm1 + 0.2011s ··· ··· tm20 = tm1 + 25.4 × 2875 / (600 × 100) is estimated to ≒ tm1 + 1.2171s.

However, in actuality, the pattern position estimated as described above is given a predetermined width in consideration of the cycle unevenness of the conveyor belt 30 and the variation of the toner detection sensor 50. In the present embodiment, a width of ± 10 dots is given and estimated as the detection position range of the second and subsequent toner patterns 602 to 620. When the transport speed of the transport belt 30 is 100 mm / s, the estimated toner positions of the second and subsequent toner patterns 602 to 620 based on the toner position (time) tm1 of the first toner pattern 601 are calculated as follows. Like

[0066]   tm2 '= tm1 + 25.4 × (175 ± 10) / (600 × 100)           ≈tm1 + (0.0741 ± 0.0042) s   tm3 '= tm2 + 25.4 × (150 ± 10) / (600 × 100)           ≈tm2 + (0.0635 ± 0.0042) s   tm4 '= tm3 + 25.4 × (150 ± 10) / (600 × 100)           ≈tm3 + (0.0635 ± 0.0042) s       ...       ...   tm20 '= tm19 + 25.4 × (150 ± 10) / (600 × 100)             ≈ tm19 + (0.0635 ± 0.0042) s Alternatively,   tm2 '= tm1 + 25.4 × (175 ± 10) / (600 × 100)           ≈tm1 + (0.0741 ± 0.0042) s   tm3 '= tm1 + 25.4 × (325 ± 10) / (600 × 100)           ≈tm1 + (0.1376 ± 0.0042) s   tm4 '= tm1 + 25.4 × (475 ± 10) / (600 × 100)           ≈tm1 + (0.2011 ± 0.0042) s       ...       ...   tm20 '= tm1 + 25.4 × (2875 ± 10) / (600 × 100)             ≈tm1 + (1.2171 ± 0.0042) s

The information of tm2 'to tm20' (detection position range information of the second and subsequent toner patterns 602 to 620: hereinafter referred to as "estimated toner position information") is RA.
It is stored in M42.

Step 4: (Detection of Toner Positions of Second and Later Toner Patterns) The toner detection sensor 50 detects the second and subsequent toner patterns 602 to 620 as pulse waveforms in the same manner as in Step 2. Then, from the pulse waveform, the CPU 41
And the second and subsequent toner patterns 602 to 62 are calculated.
The time tm ″ of the center position for 0 (however, there is a possibility of erroneous detection and does not necessarily indicate the actual position of the toner pattern. Hereinafter, referred to as “detection position information (tm ″)”). calculate. The calculation result is stored in the RAM 42.

Step 5: (Detection of Toner Positions of All Toner Patterns) Here, since there is a possibility that an erroneous detection due to a scratch or the like is included, all the toner patterns 601 to 62 depending on the number.
Even if the toner positions p1 to p20 of 0 are detected,
That is, in this embodiment, even if the detection position information that seems to be 20 toner patterns is obtained, it does not mean that the toner positions p1 to p20 of all the toner patterns 601 to 620 are actually detected.

Therefore, in this embodiment, the pattern width 100 dot of the first toner pattern 601 and the pattern width 50 of the second and subsequent toner patterns 602 to 620.
dot, pattern interval 100 dot, pattern number 20
Since it is set as a book, the following formula, (50dot × 19) + (100dot × 19) = 2
2 after detecting the first toner pattern 601 from 850 dots
It is determined that all the toner positions p1 to p20 have been detected by the rotation of the conveyor belt 30 by 850 dots.

For example, the transport speed of the transport belt 30 is 10
Since it is 0 mm / s, 2850 dot / 100 mm / s = 25.4 × 2850 / (600 × 100) = 1.2065s, and when 1.2065s have elapsed after the first toner pattern 601 was detected, all It is determined that the toner patterns 601 to 620 are detected.

Step 6: (Confirm whether or not toner position information that does not match the detection position range of the toner patterns of the second and subsequent toner patterns estimated in Step 3 is detected) In this step, the second and subsequent toner rollers estimated in Step 3 are detected. It is determined whether there is a detection position that does not match the estimated toner positions of the toner patterns 602 to 620. That is,
Estimated toner position information tm2 ′ stored in RAM 42
tm20 ′ and the detected position information t stored in the RAM 42
m ″ is compared to determine whether the detected position information tm ″ exists outside the range of the estimated toner position information tm2 ′ to tm20 ′.

If none of the detected position information tm ″ exists outside the range of the estimated toner position information tm2 ′ to tm20 ′, the process proceeds to step 8 and the toner pattern 60
The detection sequence of 1 to 620 is completed.

On the other hand, if there is even one of the detected position information tm ″ outside the range of the estimated toner position information tm2 ′ to tm20 ′, the process proceeds to step 7.

Step 7: (In the previous step 6, it is determined that the detection position that does not match the estimated toner position information tm2 'to tm20' is erroneous detection of the toner pattern, and the detected position information is ignored.) Detected position information tm '' Is estimated toner position information tm2'-
If there is at least one outside each range of tm20 ′, the detection position is considered to be a toner pattern detected at a position where the toner pattern should not originally exist. That is, of the detected position information tm ″,
The detected position information outside the respective ranges of the estimated toner position information tm2 'to tm20' is regarded as erroneous detection of the toner pattern due to a scratch or the like, and the detected position information is ignored. Then, this detected position information is not adopted as a reference value in color misregistration correction. In other words, the detected position information t
Only when m ″ is within the respective range of the estimated toner position information tm2 ′ to tm20 ′, the detected position information is regarded as correct and the process proceeds to step 8.

Step 8: (End of Toner Pattern Detection Sequence) As described above, by the control of Steps 1 to 7, for example, a flaw on the conveyor belt 30 is erroneously detected as a toner position.
Erroneous detection of a clear toner pattern can be eliminated. As a result, the toner pattern can be accurately detected, and by adopting the detection result as a reference value, it is possible to prevent deterioration of the color misregistration correction accuracy.

In FIG. 2, step 3 of estimating the detection position range of the second and subsequent toner patterns 602 to 620 from the toner position (time) tm1 of the first toner pattern 601 is performed after step 2. If it is before step 6, it does not matter where it is located.

With respect to toners of other colors, the same pattern set is formed and the toner position of each toner pattern is detected. Then, for example, the deviation amount of the toner pattern of the desired color can be calculated based on the toner position of the corresponding toner pattern in the pattern set of the reference color.
Here, from the toner position information of each toner pattern obtained as described above, that is, the one used as the reference value in the color misregistration correction, the color misregistration amount of each component (the color misregistration amount in the transport direction of the recording material S is calculated. , An amount of color shift in the main scanning direction, etc.) is as described above. However, there are various methods for calculating the color misregistration amount, and the present invention does not limit this. Also, formed of toner of multiple colors,
A pattern set composed of a plurality of toner patterns (the presence of a plurality of toner patterns of each color is not prevented)
In the above, the configuration of the pattern set is various, such as the arrangement mode of each toner pattern and the arrangement mode of the toner pattern for detecting various color misregistrations (color misregistration in the transport direction, color misregistration in the scanning direction), but the present invention is not limited thereto. Not something to do.

In this embodiment, the toner detection sensor 50
The first toner pattern 601 in the detection order by
The pattern width of the other toner patterns 602 to 62
Although it has been described as being thicker than 0, the present invention is not limited to this. It is preferable to make the pattern width of the first toner pattern 601 thicker in order to simplify the toner pattern detection process. However, at least one of a plurality of continuous toner patterns is used as a reference pattern, and the pattern width is set to other values. It may be thicker than the toner pattern.

Embodiment 2 Next, another embodiment of the present invention will be described. In this embodiment, in addition to the clear erroneous detection of the toner pattern performed in the first embodiment, the second and subsequent toner patterns 602 to 602 are removed.
In the respective ranges of the estimated toner position information tm2 ′ to tm20 ′ of 620, when two or more toner positions are detected although only one toner position should be detected originally, the detection result is invalid. It is characterized by

The toner pattern detecting method in this embodiment will be described with reference to the flowchart of FIG. In the present embodiment, the processes of steps 1 to 5 are the same as steps 1 to 5 of the embodiment 1, respectively. Therefore, the description of the same parts as those in the first embodiment is omitted, and the processing after step 6 that is characteristic of the present embodiment will be described.

Step 6: (Confirm whether or not a pattern that does not match the detection position range of the second and subsequent toner patterns estimated in Step 3 is detected) In this step, the second and subsequent toners estimated in Step 3 are detected. It is determined whether or not there is a detection position that does not match the estimated toner position information of the patterns 602 to 620. That is, the estimated toner position information tm stored in the RAM 42
2 ′ to tm20 ′ and the detected position information tm ″ stored in the RAM 42 are compared, and whether the detected position information tm ″ exists outside the respective ranges of the estimated toner position information tm2 ′ to tm20 ′. To judge.

If none of the detected position information tm ″ is outside the range of the estimated toner position information tm2 ′ to tm20 ′, the process proceeds to step 8. On the other hand, if there is even one of the detected position information tm ″ outside the range of the estimated toner position information tm2 ′ to tm20 ′,
Go to step 7.

Step 7: (In the previous step 6, the detected position information that does not match the estimated toner position information tm2 'to tm20' is determined to be an erroneous detection of the toner pattern, and the detected position information is ignored.) Detected position information tm ''Is estimated toner position information tm2' ~
If there is at least one outside each range of tm20 ′, the detection position is considered to be a toner pattern detected at a position where the toner pattern should not originally exist. That is, of the detected position information tm ″,
The detected position information outside the respective ranges of the estimated toner position information tm2 'to tm20' is regarded as erroneous detection of the toner pattern due to a scratch or the like, and the detected position information is ignored. Then, this detected position information is not adopted as a reference value in color misregistration correction. In other words, the detected position information t
Only when m ″ is within the respective range of the estimated toner position information tm2 ′ to tm20 ′, the detected position information is regarded as correct and the process proceeds to step 8.

Step 8: (Confirm whether or not the detection position information of the toner pattern overlaps within the detection position range of the second and subsequent toner patterns estimated in Step 3) In the previous step 7, the estimated toner position information tm2 '~
It was possible to eliminate erroneous detection of the toner pattern outside each range of tm20 ″. However, there is a possibility that two or more toner patterns will be detected within the respective ranges of the estimated toner position information tm2 ′ to tm20 ′.

Therefore, in this step, it is determined whether or not there are two or more pieces of detected position information tm ″ within the respective ranges of the estimated toner position information tm2 ′ to tm20 ′.
Then, the detected position information tm ″ is the estimated toner position information t.
When there are two or more overlapping areas in each of m2 ′ to tm20 ′, the process proceeds to step 9, and the detected position information tm ″ is estimated toner position information tm2 ′ to tm20 ′.
If there is only one in each of the ranges, go to step 10.

Step 9: (Ignore all detected position information determined to overlap within the range of estimated toner position information tm2 'to tm20' in the previous step 8) In this step, estimated toner position information tm2 'to tm
A plurality of detected position information t within each range of 20 '
m '', the estimated toner position information tm2'-
The detected position information tm ″ within the range of tm20 ′ is invalidated. That is, the estimated toner positions tm2 ′ to tm2
If two or more toner patterns are detected while one toner pattern should be detected in each range of 0 ', estimated toner position information tm2' to tm20 'in which two or more toner patterns are detected. The detected position information tm ″ within the range is not used as a reference value in color misregistration correction.

Step 10: (End of Toner Pattern Detection Sequence) As described above, under the control of Steps 1 to 9, for example, a flaw on the conveyor belt 30 is erroneously detected as a toner position.
Erroneous detection of a clear toner pattern can be eliminated. As a result, the toner pattern can be accurately detected, and by adopting the detection result as a reference value, it is possible to prevent deterioration of the color misregistration correction accuracy.

In FIG. 3, step 3 of estimating the detection position range of the second and subsequent toner patterns 602 to 620 from the toner position (time) tm1 of the first toner pattern 601 is performed after step 2. If it is before step 6, it does not matter where it is located.

Embodiment 3 Next, another embodiment of the present invention will be described. In the present embodiment, when the toner pattern is not detected within each range of the estimated toner position information tm2 ′ to tm20 ′ of the second and subsequent toner patterns 602 to 620,
It is judged that the toner pattern detection is missing (detection error),
It is characterized in that it is not referred to as a reference value in color misregistration correction.

The toner pattern detecting method in this embodiment will be described with reference to the flowchart of FIG. In the present embodiment, the processes of steps 1 to 5 are the same as steps 1 to 5 of the embodiment 1, respectively. Therefore, the description of the same parts as those in the first embodiment is omitted, and the processing after step 6 that is characteristic of the present embodiment will be described.

Step 6: (Confirm whether or not the toner pattern is detected in each of the detection position ranges of the second and subsequent toner patterns estimated in Step 3) In this step, the second and subsequent toner patterns estimated in Step 3 It is determined whether the toner patterns 601 to 620 are present in the detection position ranges of the toner patterns 601 to 602, respectively. That is, the estimated toner position information tm2 ′ to tm20 ′ stored in the RAM 42 is compared with the detected position information tm ″ stored in the RAM 42, and the detected positions within the respective estimated toner position tm2 ′ to tm20 ′ are detected. It is determined whether at least one piece of information tm ″ is present.

If there is at least one detected position information tm ″ in each range of the estimated toner position information tm2 ′ to tm20 ′, the process proceeds to step 8, while the detected position information tm ″ is the estimated toner position information tm ″. tm2'-tm2
If there is even one that does not exist within each range of 0 ', go to step 7.

Step 7: (Determination of Missing Detection of Toner Pattern) In this step, the estimated toner positions tm2 'to tm2
If there is at least one that does not have the detected position information tm ″ in each range of 0 ′, it is determined that the toner pattern detection has been omitted (detection error), and the estimated toner position information t
The detection position information in m2 'to tm20' is not referred to as a reference value for color misregistration correction.

Step 8: (End of Toner Pattern Detection Sequence) As described above, the erroneous detection of the toner pattern can be eliminated by the control of Steps 1 to 7. This allows
Although the reference value for color misregistration correction is reduced, it is possible to prevent the adoption of an apparently wrong value and consequently prevent the accuracy of color misregistration correction from being reduced.

In FIG. 4, step 3 of estimating the detection position range of the second and subsequent toner patterns 602 to 620 from the toner position (time) tm1 of the first toner pattern 601 is performed after step 2. If it is before step 6, it does not matter where it is located.

Needless to say, the accuracy of color misregistration correction can be further improved by combining the toner pattern detection method of this embodiment with the first or second embodiment.

Embodiment 4 In Embodiments 1 to 3, a latent image is formed on an image bearing member, and a plurality of color developer images obtained by developing the latent image are transferred onto a transfer material conveyed by a conveyor belt. Sequentially superimpose and transfer,
In a color image forming apparatus forming a color image, a color misregistration measuring toner pattern formed on a conveyor belt is accurately detected.

In the present embodiment, the present invention is applied to a color image forming apparatus using an intermediate transfer member to accurately detect a color misregistration measuring toner pattern. In the intermediate transfer body method, a latent image is formed on the image carrier, and the developer images of a plurality of colors obtained by developing the latent image are sequentially superimposed and transferred onto the intermediate transfer material to form a color image. To do.

An example of a color image forming apparatus using an intermediate transfer body to which the present invention can be applied will be described with reference to FIG. 14, elements having the same functions and configurations as those of the image forming apparatus shown in FIG. 5 are designated by the same reference numerals.

The color image forming apparatus 200 of FIG. 14 is an intermediate transfer type color laser beam printer. First, a latent image is formed by the laser scanner unit 11 on the photosensitive drum 18 that is uniformly charged by the charging roller 16 as a charging unit based on image information sent for each color based on the TOP signal. . Photoconductor drum 18
The latent image formed on the developing device is sequentially developed by the developing devices 14Y (yellow), 14C (cyan), 14Bk (black), and 14M (magenta) held in the developing device holder D that is a rotating body, and the intermediate image is formed. The image is transferred to the transfer body (intermediate transfer drum) 33 multiple times. As a result, a multicolor image is formed on the intermediate transfer body 33. In this embodiment, the charging roller 16,
Laser scanner unit 11, developing devices 14Y, 14C,
An image forming unit that forms a toner image of a plurality of colors on the intermediate transfer member 33 is provided by including the rotary developing device 140 that holds 14Bk and 14M in the holding member D. A transfer bias is applied to the intermediate transfer member 33 to form a primary transfer unit.

After that, the plain paper cassette 22 (22a,
22b, 22c, 22d), a recording material S such as a recording paper selected and extracted is conveyed between the intermediate transfer body 33 and a transfer belt 70 as a secondary transfer means, and the recording material S is transferred onto the intermediate transfer body 33. Transfer the multicolor image of. The transfer belt 70 is
The recording material S also has a function as a carrying means for carrying and carrying the recording material S thereon.

The multicolor image transferred onto the recording material S is thermally fixed on the recording material S by the fixing device 23. After that, the recording material S
Is discharged from the recording material discharge section 72 to the upper tray section 39a or the lower tray section 39b.

The operation of the color laser beam printer will be described more specifically. First, the photosensitive drum 1
8 is uniformly charged to a predetermined polarity by the charging roller 16 (for example, -600V). The photoconductor drum 18
Is scanned and exposed by the laser beam light 13 according to the image data sent from the controller on the basis of the TOP signal to form a latent image. For example, the latent image formed on the photoconductor drum 18 according to the magenta color image information as the first color is developed by the magenta color developing device 14M, and the first color developer image ( A toner image) is formed.

On the other hand, at a predetermined timing, the primary transfer high voltage (for example, +2) of the opposite polarity (for example, positive polarity) to the toner image is obtained.
00V) is applied to the intermediate transfer member 33, and the photosensitive drum 18
The upper first color toner image is transferred to the intermediate transfer member 33. After that, the toner of the first color remaining on the photoconductor drum 18 is removed by the cleaner (cleaning device) 15 to prepare for the next latent image formation and development process.

After the above steps for the first color are completed, a latent image of the second color (for example, cyan) is formed on the photosensitive drum 18 by the laser beam light 13, and then a developing device of the second color (cyan color) is formed. A developer image is formed by the developing device 14C). Then, the second-color developer image is transferred to the intermediate transfer member 33 in the same manner as described above in conformity with the tip position of the first-color toner image previously transferred to the intermediate transfer member 33.

Similarly, latent images of the third color (for example, yellow) and the fourth color (for example, black) are sequentially formed on the photosensitive drum 18, and sequentially developed by the developing units 14 for the third and fourth colors, respectively. To do. Then, the toner images of the third color and the fourth color are sequentially transferred in alignment with the toner images previously transferred to the intermediate transfer member 33.

Thus, the toner images of four colors are formed on the intermediate transfer member 33 in an overlapping state. After that, when the image front end portion of the intermediate transfer body 33 on which the toner images of four colors are superimposed and transferred approaches the transfer (secondary transfer) position to the recording material, a high voltage (for example, +2 kV) is applied to the transfer belt 70, The transfer belt 70 is brought into contact with the intermediate transfer body 33. Then, between the intermediate transfer body 33 and the transfer belt 70, the plain paper cassette 2
The recording material S picked up from any one of No. 2 (22a to 22d) is conveyed according to the leading end position of the toner image and transferred.

Further, a high voltage (for example, -1 kV) having a reverse polarity of the bias applied to the transfer belt 70 is applied to the static elimination needle 71 arranged at a downstream portion of the transfer belt 70 in the conveyance direction of the recording material S or grounded. The recording material S is operated until the trailing edge of the recording material S leaves the transfer belt 70. As a result, the recording material S
The upper residual charge is removed. When the trailing edge of the recording material S reaches the transfer end position (the exit of the nip portion formed by the intermediate transfer body 33 and the transfer belt 70), the primary transfer high voltage applied to the intermediate transfer body 33 is turned off (ground potential). ).

Further, when the trailing edge of the recording material S separates from the transfer belt 70, the high voltage applied to the transfer belt 70 and the discharging needle 71 is turned off. At this time, the transfer belt 71 is separated from the intermediate transfer body 33.

The recording material S separated from the transfer belt 70 is conveyed to the fixing device 23, where the toner image on the recording material S is thermally fixed. Then, the recording material S is discharged to the upper tray portion 39a or the lower tray portion 39b.

When the transfer of the developer image from the intermediate transfer member 33 to the recording material S starts and the tip of the transfer portion after the transfer approaches the cleaning roller 37, the cleaning roller 3
7 is brought into contact with the intermediate transfer member 33. A bias having the same polarity as that of the transfer belt 70 is applied to the cleaning roller 37, and the residual transfer developer having the opposite polarity on the intermediate transfer body 33 is drawn to the cleaning roller 37 to perform cleaning.
Further, after the polarity is changed to the same polarity, the transfer residual developer is returned to the photosensitive drum 18 by further strengthening the polarity, and is prepared for the next image forming sequence of the intermediate transfer body 33.

When performing double-sided printing on the recording material S, the recording material S which has undergone the above-described image forming sequence is placed on the manual feed tray 28 with the surface on which the toner image is fixed on the back surface, and the same image forming sequence as described above is performed. Or the recording material S that has undergone the above-mentioned image forming sequence is placed on the plain paper cassette 22 (22a ...
22d), and the same image forming sequence as described above is performed again.

Alternatively, after the developer image is fixed on the recording material S by the above-mentioned image forming sequence, the duplex unit 7
The recording material S is conveyed to the 3 side. And the duplex unit 73
The switchback roller 74 is rotated in the paper feed direction to guide the recording material S into the switchback path 73a, and before the trailing end of the recording material S reaches the switchback roller 74, The recording material S is conveyed to the conveyance path 73b of the double-sided unit 73 provided in the lower portion of the fixing device 23 by rotating in the opposite direction. After that, the recording material S is picked up from the duplex unit 73 and the above-mentioned image forming sequence is performed. After that, the recording material S having the developer images fixed on both sides is recorded on the upper tray portion 39.
a or to the lower tray portion 39b. Thus, the recording material S printed on both sides is formed.

FIG. 15 shows a schematic structure of the intermediate transfer member 33. The intermediate transfer member 33 is formed by covering the outer circumference of an aluminum cylinder 33a with an elastic layer 33b such as medium resistance sponge or medium resistance rubber.

An image forming start position detection sensor (TOP sensor) A, a paper feed start timing sensor (RS sensor) B, and a toner detection sensor C are provided around the intermediate transfer member 33.

The toner detection sensor C eliminates color misregistration among the colors of yellow (Y), magenta (M), cyan (C), and black (Bk) in the color image, and performs intermediate transfer to obtain an appropriate image. The color shift amount measuring toner pattern 60 is formed on the body 33 for a test, and is used to adjust the writing timing of the image of each color based on the detection result.

In this embodiment, the operation of the color misregistration correction means, that is, the method of detecting the toner pattern by using the toner detection sensor C and controlling the image forming position of the toner image of each color based on the detected color misregistration amount. Is the toner detection sensor 50 in the color image forming apparatus 100 of the first to third embodiments.
And the like. Therefore, here, the description of Examples 1 to 3 is incorporated by replacing the toner pattern with that formed on the intermediate transfer member.

The first to fourth embodiments have been described by taking the laser beam printer using the laser beam as the exposure method as an example. However, it goes without saying that it can be applied to an LED printer that uses LEDs as an exposure method.

In each of the above embodiments, the color image forming apparatus has been described as having one toner detection sensor.
The present invention is not limited to this. For example, the toner detection sensors are provided near both ends in the direction (main scanning direction) substantially orthogonal to the moving direction of the conveyor belt 30 or the intermediate transfer member 33, and the conveyor belt 30 or the intermediate belt is provided. The toner patterns formed on the transfer body 33 near both ends in the scanning direction may be detected by the respective toner patterns.

[0121]

As described above, according to the present invention,
The image for measuring the amount of color misregistration can be accurately detected, and the color misregistration between the colors can be properly corrected. In addition, it is possible to prevent the scratches on the surface of the transfer target such as the conveyor belt and the intermediate transfer member from being detected as the position of the developer, and to prevent the deterioration of the color misregistration correction accuracy due to the missing detection of the image for measuring the color misregistration amount. The color misregistration amount measurement image can be detected at.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of a toner pattern for measuring a color shift amount according to the present invention.

FIG. 2 is a flow chart diagram for explaining an embodiment of a toner pattern detection operation according to the present invention.

FIG. 3 is a flow chart for explaining another embodiment of the toner pattern detecting operation according to the present invention.

FIG. 4 is a flow chart for explaining still another embodiment of the toner pattern detecting operation according to the present invention.

FIG. 5 is a schematic sectional view of an example of a color image forming apparatus to which the present invention can be applied.

FIG. 6 is a block diagram for explaining color misregistration correction using a toner detection sensor.

FIG. 7 is a block diagram illustrating a circuit configuration of a toner detection sensor.

FIG. 8 is a flowchart for explaining a schematic procedure of a color misregistration correction operation.

FIG. 9 is a graph showing the relationship between the amount of light received by the light receiving portion (PD) of the toner detection sensor and the current value flowing through the PD at that time.

FIG. 10 is a schematic diagram showing a relationship between a toner pattern on a conveyor belt and a toner detection sensor.

FIG. 11 is a graph showing a detected voltage waveform V2 when a toner pattern is detected by a toner detection sensor and a pulse waveform A created from the detected waveform.

12A is a schematic diagram of an example of a toner pattern for detecting color misregistration in the transport direction, and FIG. 12B is a schematic diagram of an example of a toner pattern for detecting color misregistration in the scanning direction.

FIG. 13 is a schematic diagram for explaining (a) color misregistration in the transport direction and (b) color misregistration in the scanning direction.

FIG. 14 is a schematic sectional view of another example of a color image forming apparatus to which the present invention can be applied.

FIG. 15 is a schematic view of an intermediate transfer member.

[Explanation of symbols]

11 Laser Scanner Unit (Exposure Means) 14 Developing Device (Developing Means) 15 Cleaning Device (Cleaning Means) 16 Charging Roller (Charging Means) 18 Photoreceptor Drum (Image Bearing Body) 30 Conveying Belt (Conveying Means) 33 Intermediate Transfer Drum ( Intermediate transfer member) 50 Toner detection sensor (detection means) 60 (601 to 620) Toner pattern (image for measuring color misregistration amount)

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 2C061 AQ06 AR01 KK18 KK22 KK26                       KK28 KK35                 2H027 DA39 DE02 DE07 DE10 EB06                       EC04 EC06 EC07 ED06 ED24                       EF09 ZA07                 2H030 AA01 AB02 AD16 BB02 BB16                       BB24 BB42 BB44 BB56 BB63                 2H200 FA04 GA12 GA23 GA34 GA47                       GA49 GB11 GB22 GB25 GB44                       HA02 HA28 HB12 JA02 JA16                       JA18 JB06 JB16 JB20 JB26                       JB42 JB50 JC03 JC12 JC13                       JC15 JC20 LA24 LB02 LB03                       LB09 LB13 LB15 MA03 MA08                       PB13 PB16 PB17 PB39

Claims (18)

[Claims] 1. An image forming unit for forming developer images of different colors on a plurality of image carriers, and transferring the developer images to form developer images of a plurality of colors on a transfer target. A conveying unit that conveys a recording material onto which a developer image is transferred from the plurality of image carriers to the plurality of image carriers, and a detection unit that detects position information of the developer image on the conveying unit. A plurality of colors formed by the image forming unit based on respective position information obtained by detecting the color shift measuring images of a plurality of colors formed continuously on the conveying unit by the image forming unit by the detecting unit. And a means for controlling the image forming position of the developer image, wherein at least one of the continuous color misregistration measurement images is used as a reference image, and the color misregistration measurement images are more than the other color misregistration measurement images. Direction of movement of carrier A color image forming apparatus, wherein the detection position range of each of the other color misregistration measuring images by the detecting unit is estimated based on the position information of the reference image detected by the detecting unit. . 2. The color image forming apparatus according to claim 1, wherein the reference image is located at the head of the continuous color misregistration measurement images in the order of detection by the detecting means. 3. Detection time information as detection position range of each of the other color shift images of the continuous color shift measurement image is obtained from detection time information as position information of the reference image detected by the detecting means. 3. The color image forming apparatus according to claim 1, which is calculated. 4. When the detection means detects a developer image outside the detection position range, the detection signal is not used for controlling the image forming position. 3. The image forming apparatus of 3. 5. When the detection unit detects a plurality of developer images in one of the detection position ranges, a detection signal within the detection position range is not used for controlling the image forming position. The color image forming apparatus according to any one of claims 1 to 4. 6. In each of the detection position ranges,
6. When any one of the developer images is not detected by the detection means, it is determined that a detection error of the color misregistration measurement image is within the detection position range. The described color image forming apparatus. 7. The color image forming apparatus according to claim 1, wherein the detecting unit uses an optical semiconductor element. 8. The detecting means includes a light emitting portion that irradiates the surface of the conveying means with light, and a light receiving portion that receives light reflected by the developer image on the surface of the conveying means or on the conveying means. The color image forming apparatus according to any one of claims 1 to 7, further comprising: 9. The color image forming apparatus according to claim 1, further comprising a plurality of the detecting means. 10. An image forming means for sequentially forming developer images of different colors on an image carrier and transferring the developer images to form developer images of a plurality of colors on a transfer target, An intermediate transfer member on which a developer image is sequentially transferred from the image carrier, a detection unit for detecting positional information of the developer image on the intermediate transfer member, and an image forming unit on the intermediate transfer member. The image forming positions of the developer images of a plurality of colors are controlled by the image forming means based on the respective position information obtained by detecting the color shift measuring images of a plurality of colors formed continuously by the detecting means. In a color image forming apparatus having a means, at least one of the continuous color shift measurement images is used as a reference image, and is formed thicker in the moving direction of the intermediate transfer member than other color shift measurement images, By the detection means A color image forming apparatus, which estimates a detection position range of each of the other color misregistration measurement images by the detection unit, based on the position information of the reference image detected by the detection unit. 11. The color image forming apparatus according to claim 10, wherein the reference image is located at the head of the continuous color misregistration measuring images in the order of detection by the detecting means. 12. The detection time as detection position range of each of the other color misregistration measurement images of the continuous color misregistration measurement images from the detection time information as position information of the reference image detected by the detection means. The color image forming apparatus according to claim 10, which calculates information. 13. The detection signal is not used for controlling the image forming position when the detection unit detects the developer outside the detection position range. Color image forming apparatus. 14. In one of the detection position ranges, when the detection unit detects a plurality of developer images, the detection signal within the detection position range is not used for controlling the image forming position. The color image forming apparatus according to any one of claims 10 to 13. 15. The color misregistration measurement image detection error is determined within the detection position range when the detection unit does not detect any developer in each of the detection position ranges. Item 15. The color image forming apparatus according to any one of items 10 to 14. 16. The color image forming apparatus according to claim 10, wherein the detecting unit uses an optical semiconductor element. 17. The detecting means includes a light emitting portion that irradiates the surface of the intermediate transfer member with light, and a light receiving portion that receives the light reflected by the surface of the intermediate transfer member or the developer image on the intermediate transfer member. And 10 are included.
The color image forming apparatus according to any one of 1. 18. The color image forming apparatus according to claim 10, further comprising a plurality of the detecting means.