JP3697885B2 - Black image density detection method and color image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a black image density detection method. , And More specifically, the color image forming apparatus has a function of forming a color image on the intermediate transfer member by transferring the color toner image and the black toner image onto the intermediate transfer member. The present invention relates to a black image density detection method for detecting the density of a toner image, an image position shift and image density detection method for detecting image position shift and image density in the color image forming apparatus, and the color image forming apparatus.
[0002]
[Prior art]
Conventionally, a plurality of image forming units are provided, and toner images of different colors (generally yellow (Y), magenta (M), cyan (C), black (K) toner images) are provided in each image forming unit). Is formed on a photoconductor, and a toner image formed on each photoconductor is transferred onto the same transfer material (for example, recording paper) to form a color image, a so-called tandem color image. Various forming apparatuses have been proposed.
[0003]
In such a color image forming apparatus, toner images of different colors formed by a plurality of image forming units are superimposed on the same transfer material. It is important to stabilize the concentration.
[0004]
Therefore, in the color image forming apparatus as described above, the density of the toner image formed on the photoconductor is detected by each image forming unit, and the density control is performed so that the detected density is within an appropriate range. It was.
[0005]
On the other hand, in recent years, for the purpose of enlarging the size of the transfer material to be supported and improving the stability of transferability, the toner images of each color of YMCK are transferred from the photoreceptor to the intermediate transfer body to form the desired color image, A tandem type color image forming apparatus using an intermediate transfer body that collectively transfers the color image from an intermediate transfer body to a transfer material has been proposed.
[0006]
However, in this tandem type color image forming apparatus using the intermediate transfer member, the toner image density is detected on the intermediate transfer member in order to remove the influence of the transfer property from the photosensitive member to the intermediate transfer member. It is necessary to detect the density of the formed toner image.
[0007]
By the way, the density of an image to be detected is often obtained from the ratio between the amount of light reflected from the image and the amount of light reflected from the background by irradiating the surface on which the image is formed with a predetermined amount of light. In this case, it is known that if the difference between the light reflectance of the image and the light reflectance of the ground is small, it is difficult to detect the density of the image with high accuracy.
[0008]
Considering the light reflectance of the toner of each color of YMCK described above, the light reflectance of YMC color toner is high, and particularly in the wavelength in the infrared region (900 nm to 1200 nm), FIG. 3 (B), FIG. 4 (B), As shown in FIG. 5B, it can be seen that the light reflectance is 90% or more. On the other hand, the light reflectance of the black toner is 10% or less in any wavelength region as shown in FIGS. On the other hand, the light reflectance of a dielectric that is generally used as an intermediate transfer member and whose volume resistance is adjusted by carbon is about 10 to 20%. For this reason, it may be difficult to accurately detect the density of the black toner image formed on the intermediate transfer member.
[0009]
As a method for solving the above problems, a method may be considered in which a color toner image serving as a base is formed on an intermediate transfer member, a black toner image is formed on the intermediate transfer member, and then the density of the black toner image is detected. It is done.
[0010]
In relation to this, Japanese Patent Laid-Open No. 7-168401 discloses a technique for controlling the density so that the density of the color toner image serving as the background becomes the target value before detecting the density of the black toner image as described above. It is disclosed. In this technology, before detecting the density of the black toner image, the density of the color toner image that is the background is always detected, and only when the density value is within the target range, the density of the black toner image is detected. If the density value of the color toner image is outside the target range, process control such as development bias and exposure amount is performed, and the density detection of the black toner image is performed when the color toner image density value falls within the target range. .
[0011]
However, in the above technique, since a single photoconductor is used, the density of the color toner image serving as the background is detected on the intermediate transfer body, and the density of the black toner image is detected after controlling the density as necessary. By the time, the intermediate transfer member needs to be driven at least one rotation or more, and may be two or more rotations. As a result, the processing efficiency at the start of the image forming process is abruptly reduced, and there is a possibility that the time from when the user issues a print output to when the print is output is prolonged.
[0012]
On the other hand, in a conventional tandem type color image forming apparatus, for example, as described in JP-A-6-289670, a black toner image forming unit is disposed upstream of a color toner image forming unit. It was common.
[0013]
However, when the black toner image forming unit is arranged on the most upstream side as described above, the density of the color toner image serving as the background is detected and the density is controlled, as in the case of using the single photoconductor described above. Further, it is necessary to drive the intermediate transfer member at least once or more before the density detection of the black toner image is performed. The processing efficiency at the start of the image forming process is drastically reduced, and the user instructs print output. Inconveniences such as prolonging the time from print to print output may occur.
[0014]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems, and a black image density detection method and a color image forming apparatus capable of efficiently performing accurate black toner image density detection that is not affected by the background. To provide Eyes Target Toss The
[0015]
[Means for Solving the Problems]
In order to achieve the first object, a black image density detection method according to a first invention corresponding to the first aspect of the invention is an intermediate transfer that is conveyed in a predetermined conveyance direction along a predetermined circulation path. A color toner image is formed on the body by a color image forming unit, and a black toner image is formed on the color toner image by a black image forming unit disposed downstream of the color image forming unit in the transport direction. A black image density detecting method for detecting a density of the black toner image in a color image forming apparatus for forming a color image on the intermediate transfer body, wherein the color toner image is applied to the intermediate transfer body by the color image forming unit. And detecting the density of the formed color toner image, and when the density detection value of the color toner image is within a predetermined appropriate density range, the black image forming unit performs intermediate transfer. Formed by superimposing a black toner image on a part of the color toner images on, for detecting the density of the formed black toner image, characterized in that.
[0016]
According to a second aspect of the invention, there is provided a black image density detection method according to a second aspect of the present invention, in which a color image forming unit applies a color image to an intermediate transfer member that is conveyed in a predetermined conveyance direction along a predetermined circulation path. A color image is formed on the intermediate transfer member by forming a toner image and forming a black toner image on the color toner image by a black image forming unit disposed downstream of the color image forming unit in the transport direction. A black image density detecting method for detecting a density of the black toner image in a color image forming apparatus that forms a plurality of color toner images formed on the intermediate transfer member by the color image forming unit. One of the plurality of color toner images is formed by superimposing a black toner image on a part of one color toner image by the black image forming unit, and any one of the plurality of color toner images is selected. Detecting the density of the color toner image, if the detected density of the color toner image is within a predetermined proper range of concentrations, for detecting the concentration of the black toner image, characterized in that.
[0017]
According to a third aspect of the present invention, there is provided a black image density detection method according to a third aspect of the present invention, in which a color image forming unit applies a color image to an intermediate transfer member conveyed in a predetermined conveyance direction along a predetermined circulation path. A color image is formed on the intermediate transfer member by forming a toner image and forming a black toner image on the color toner image by a black image forming unit disposed downstream of the color image forming unit in the transport direction. A black image density detection method for detecting the density of the black toner image in a color image forming apparatus for forming a color image, wherein a pair of color toner images having the same density is applied to the intermediate transfer member by the color image forming unit. A plurality of sets are formed so that the density of each set is different, and a black toner image is superimposed on a part of one of the formed color toner images by the black image forming unit. When the density of the other color toner image is detected from each set of color toner images and the density detection value of the other color toner image is within a predetermined appropriate density range, It is characterized in that the density of a black toner image formed on a part of the toner image is detected.
[0018]
Up Note Claims to achieve 6 Corresponding to the described invention 4 The color image forming apparatus according to the invention includes an intermediate transfer member conveyed in a predetermined conveyance direction along a predetermined circulation path, and a photosensitive member, and formed a color toner image on the photosensitive member, and formed the color toner A color toner image forming unit that forms a color toner image on the intermediate transfer member by transferring the image to the intermediate transfer member; and a downstream side in the transport direction with respect to the color toner image forming unit. A black toner image forming means for forming a black toner image on the intermediate transfer member by forming a black toner image on the photosensitive member and transferring the formed black toner image to the intermediate transfer member; Density detecting means for detecting the density of a color toner image and a black toner image formed on the intermediate transfer member, and a color toner image detected by the density detecting means Determining means for determining whether or not the density detection value is within a predetermined appropriate density range; and when the determination means determines that the density detection value of the color toner image is within a predetermined appropriate density range. A first control unit configured to control the black toner image forming unit to form a black toner image on a part of the color toner image and to detect the density of the formed black toner image by the density detection unit; It is characterized by having.
[0019]
Claims 9 Corresponding to the described invention 5 The color image forming apparatus according to the invention includes an intermediate transfer member conveyed in a predetermined conveyance direction along a predetermined circulation path, and a photosensitive member, and formed and formed a plurality of color toner images on the photosensitive member. A color toner image forming unit that forms a plurality of color toner images on the intermediate transfer member by transferring the color toner image to the intermediate transfer member, and disposed downstream of the color toner image forming unit in the conveying direction. A color toner image formed on the intermediate transfer body by the color toner image forming unit. The color toner image forming unit forms a black toner image on the intermediate transfer body. A black toner image forming unit that forms a black toner image on the intermediate transfer member by transferring it over a part of the image, and is disposed in the vicinity of the circulation path and formed on the intermediate transfer member. Density detecting means for detecting the density of the color toner image and the black toner image, and determining whether or not the density detection value of the color toner image detected by the density detecting means is within a predetermined appropriate density range. And determining the density of the black toner image formed by the black toner image forming means when the density detection value of the color toner image is determined to be within a predetermined appropriate density range by the determination means. And second control means for controlling to detect by the detection means.
[0020]
Claims 14 Corresponding to the described invention 6 The color image forming apparatus according to the invention includes an intermediate transfer member conveyed in a predetermined conveyance direction along a predetermined circulation path, and a photoconductor, and a set of two color toner images having the same density on the photoconductor. A plurality of color toner images formed on the intermediate transfer body by transferring the formed color toner images to the intermediate transfer body, thereby forming a plurality of color toner images on the intermediate transfer body. And a photoconductor provided on the downstream side in the transport direction with respect to the color toner image forming unit, forming a black toner image on the photoconductor, and forming the formed black toner image in the middle by the color toner image forming unit. A black toner image shape in which a black toner image is formed on an intermediate transfer body by transferring a black toner image on a part of one color toner image of each set of color toner images formed on the transfer body. Means, density detecting means for detecting the density of the other color toner image and the black toner image of each set of color toner images formed on the intermediate transfer member, which is disposed in the vicinity of the circulation path, and the density A determination unit that determines whether the density detection value of the other color toner image detected by the detection unit is within a predetermined appropriate density range; and the density detection value of the other color toner image is predetermined by the determination unit. And a third control means for controlling the density detecting means to detect the density of the black toner image formed on one color toner image of the same set when it is determined that the density is within the appropriate density range. It is characterized by having.
[0021]
In the color image forming apparatus to which the black image density detection method according to the first aspect of the invention is applied, the color toner image is formed by the color image forming unit on the intermediate transfer member that is conveyed in a predetermined conveyance direction along a predetermined circulation path. Form. Then, the black image forming unit disposed downstream of the color image forming unit in the transport direction forms the black toner image on the color toner image so as to form the color image on the intermediate transfer member.
[0022]
Here, the downstream side in the transport direction means an area within a half circumference of the circuit path along the transport direction from a predetermined position on the circuit path, and the upstream side in the transport direction means a predetermined value on the circuit path. It means an area within a half circumference of the circulation path along the direction opposite to the conveyance direction from the position.
[0023]
In such a color image forming apparatus, in the black image density detecting method according to the first invention, first, a color toner image is formed on the intermediate transfer member by the color image forming unit, and the density of the formed color toner image is detected. To do. Here, if the density detection value of the color toner image is within a predetermined appropriate density range, the black toner image is formed on a part of the color toner image on the intermediate transfer member by the black image forming unit.
[0024]
Here, the color toner image formed by superimposing the black toner images may be a color toner image whose density is to be detected, or a color toner image newly formed on the intermediate transfer member.
[0025]
Further, the black toner images may be overlapped so that the black toner image 94 is included in the color toner image 92 as shown in FIG. 20A, or the black toner image as shown in FIG. 20B. The image 94 may be overlapped so that a part of the image 94 protrudes from the color toner image 92.
[0026]
Then, the density of the black toner image formed as described above is detected. At this time, for example, if the black toner image forming portion of the intermediate transfer member is irradiated with a predetermined amount of light, the reflected light amount of the portion overlapping the color toner image in the black toner image and the black toner image overlapping in the color toner image It is possible to measure the amount of reflected light of the portion that did not exist and detect the density of the black toner image from the difference or ratio of these measured values.
[0027]
As described in the prior art, the light reflectance of a dielectric generally used as an intermediate transfer body and whose volume resistance is adjusted by carbon is about 10 to 20%. The YMC color toner has a high light reflectivity, and particularly at a wavelength in the infrared region (900 nm to 1200 nm), the light reflectivity is 90 as shown in FIGS. 3 (B), 4 (B), and 5 (B). % Or more. As shown in FIGS. 6A and 6B, the light reflectance of the black toner is 10% or less in any wavelength region.
[0028]
Therefore, the difference in diffuse reflectance between the base and the black toner image becomes larger than when the black toner image is formed using the intermediate transfer member as the base, and therefore the density of the black toner image can be detected with higher accuracy. .
[0029]
By the way, since the black image forming unit is disposed downstream of the color image forming unit in the transport direction of the intermediate transfer member, a portion where the color toner image is formed on the intermediate transfer member (hereinafter referred to as a color toner image forming unit). ) Reaches the black image forming portion before the intermediate transfer member makes a half turn.
[0030]
That is, the color toner image forming unit reaches the black image forming unit earlier than the conventional case where the black image forming unit is disposed upstream of the color image forming unit in the transport direction of the intermediate transfer member.
[0031]
Therefore, after a color toner image is formed on the intermediate transfer member, a black toner image can be formed earlier than before, and the density of the black toner image can be detected. Accordingly, it is possible to efficiently detect the density of the black toner image in the color image forming apparatus.
[0032]
On the other hand, when the density detection value of the color toner image is not within the predetermined appropriate density range, the color image forming unit may be adjusted so that the density of the formed color toner image is within the predetermined appropriate density range. desirable. Then, a color toner image may be formed on the intermediate transfer member by the adjusted color image forming unit, and the density of the formed color toner image may be detected again.
[0033]
Next, in the black image density detection method according to the second invention, first, a color image forming unit forms a plurality of color toner images on the intermediate transfer member, and one color toner among the formed color toner images. A black toner image is superimposed on a part of the image by the black image forming unit. In this way, prior to density detection, a color toner image and a black toner image are formed on the intermediate transfer member.
[0034]
Then, the density of any one of the plurality of color toner images (that is, the color toner image in which the black toner image is not formed in an overlapping manner) is detected, and the density detection value of the color toner image is predetermined. Is within the proper density range, the density of the black toner image is detected.
[0035]
As described above, even when the color toner image and the black toner image are first formed on the intermediate transfer body and then the density detection of the color toner image or the like is performed, the black image forming unit is more intermediate than the color image forming unit. Since a plurality of color toner images are formed, a part of one color toner image is formed immediately after a plurality of color toner images are formed (before the intermediate transfer member is transported at least half a round path). In addition, the black toner image can be formed in an overlapping manner, and the time required for forming the color toner image and the black toner image can be shorter than in the prior art. Accordingly, it is possible to efficiently detect the density of the black toner image in the color image forming apparatus.
[0036]
In addition, since the color toner image and the black toner image are first formed on the intermediate transfer body, for example, when density detection means is provided for each of the color toner image and the black toner image, the density of the color toner image After the detection, the density of the black toner image can be detected promptly (if the density detection value is within an appropriate density range). Further, for example, even when there is only one density detecting means, a plurality of color toner images are formed side by side along the conveyance direction of the intermediate transfer member, and a black toner image is formed on the color toner image other than the most downstream side among them. If the density of the color toner image formed downstream of the black toner image and detected in the conveyance direction is detected, the density of the black toner image can be detected quickly (when the density detection value is within an appropriate density range). it can.
[0037]
On the other hand, when the density detection value of the color toner image is not within the predetermined appropriate density range, the color image forming unit may be adjusted so that the density of the formed color toner image is within the predetermined appropriate density range. desirable. Thereafter, a plurality of color toner images are formed again on the intermediate transfer member by the adjusted color image forming unit, and a black image forming unit again blackens a part of one color toner image among the plurality of formed color toner images. The toner images may be formed in an overlapping manner, and the density of any one of the plurality of color toner images may be detected again.
[0038]
Next, in the black image density detection method according to the third aspect of the invention, first, a plurality of color toner images of the same density are applied to the intermediate transfer member by the color image forming unit so that the density of each group is different. Form a pair. For example, two sets of color toner images (total six sets of color toner images) having an image signal density (Cin) of 100%, 95%, 90%, 85%, 80%, and 75% are formed.
[0039]
Then, a black toner image is formed on a part of one color toner image of each set of formed color toner images by the black image forming unit. In this manner, similarly to the second invention, prior to density detection, a color toner image and a black toner image are formed on the intermediate transfer member.
[0040]
Furthermore, if the density of the other color toner image is detected from each set of color toner images and the density detection value of the other color toner image is within a predetermined suitable density range, one color toner of the same set is used. The density of the black toner image formed on a part of the image is detected.
[0041]
In such a black image density detection method according to the third aspect of the present invention, a plurality of sets of color toner images having different densities are formed on the intermediate transfer member. Therefore, at least one of the plurality of sets of color toner images has the other color. There is a high possibility that the density detection value of the toner image falls within a predetermined appropriate density range. In other words, the probability that the density detection values of all the color toner images are out of the predetermined appropriate density range and the density detection of the black toner image cannot be immediately performed can be avoided.
[0042]
For this reason, it is confirmed with high probability that the density of one color toner image is appropriate, and the density of the black toner image can be promptly detected. Therefore, the density detection of the black toner image in the color image forming apparatus can be performed. It can be executed efficiently.
[0043]
By the way, as a color image forming apparatus for performing black image density detection based on the black image density detection method according to the first invention described above, 4 And a color image forming apparatus according to the invention.
[0044]
This first 4 In the color image forming apparatus according to the invention, the color toner image forming means forms a color toner image on a photoconductor provided in the color toner image forming means, and the formed color toner image is passed along a predetermined circulation path. A color toner image is formed on the intermediate transfer member by transferring to the intermediate transfer member conveyed in a predetermined conveying direction.
[0045]
The density of the color toner image formed on the intermediate transfer member in this way is detected by a density detection unit arranged in the vicinity of the circulation path of the intermediate transfer member. Then, the determination unit determines whether or not the detected density value of the color toner image is within a predetermined appropriate density range.
[0046]
Here, when it is determined that the density detection value of the color toner image is within a predetermined appropriate density range, the first control unit applies a black toner image to a part of the color toner image by the black toner image forming unit. Overlapping to form. At this time, the black toner image forming unit forms a black toner image on the photoconductor provided in the black toner image forming unit, and transfers the formed black toner image to a part of the color toner image on the intermediate transfer member. Thus, a black toner image is formed. Then, the first control unit performs control so that the density of the formed black toner image is detected by the density detection unit.
[0047]
This first 4 In the color image forming apparatus according to the invention, since the black image forming portion is disposed downstream of the color image forming portion in the conveyance direction of the intermediate transfer member, the color toner image forming portion in the intermediate transfer member is the intermediate transfer member. Reaches the black image forming part before half-turning. That is, since the color toner image forming unit reaches the black image forming unit earlier than the conventional case where the black image forming unit is arranged upstream of the color image forming unit in the transport direction of the intermediate transfer member, After the color toner image is formed on the transfer body, a black toner image can be formed earlier than before, and the density of the black toner image can be detected. Accordingly, it is possible to efficiently detect the density of the black toner image in the color image forming apparatus.
[0048]
On the other hand, when it is determined that the density detection value of the color toner image is not within the predetermined appropriate density range, the first control unit causes the density of the color toner image to be within the predetermined appropriate density range. It is desirable to adjust the color toner image forming means. Then, the color toner image is formed again on the intermediate transfer member by the adjusted color toner image forming unit, the density of the formed color toner image is detected again by the density detecting unit, and the detected density detection value is a predetermined value. It is desirable to control the determination means to determine again whether or not it is within the appropriate concentration range.
[0049]
Incidentally, only one density detecting unit may be arranged in the vicinity of the circulation path of the intermediate transfer member, but it is arranged in the vicinity of the downstream side in the transport direction with respect to each of the black toner image forming unit and the color toner image forming unit. May be.
[0050]
In this case, immediately after the color toner image is formed on the intermediate transfer member by the color toner image forming means (that is, before the color toner image forming portion on the intermediate transfer member reaches the black image forming portion), the color toner is formed. The density of the image can be detected by a density detecting unit disposed in the vicinity of the color toner image forming unit. For this reason, when the density of the detected color toner image is within a predetermined appropriate density range, a black toner image can be formed on the color toner image to be detected, and the black toner image can be quickly formed. It is possible to detect the density of the toner image.
[0051]
Next, as a color image forming apparatus that performs black image density detection based on the above-described black image density detection method according to the second invention, the color image forming apparatus according to the tenth invention can be cited.
[0052]
This first 5 In the color image forming apparatus according to the present invention, the color toner image forming means forms a plurality of color toner images on a photoconductor provided in the color toner image forming means, and the formed color toner images are passed along a predetermined circulation path. A plurality of color toner images are formed on the intermediate transfer member by transferring to the intermediate transfer member conveyed in the predetermined conveying direction. The density of the plurality of color toner images to be formed may be uniform or may be different from each other.
[0053]
When the color toner image forming unit on the intermediate transfer body reaches the position of the black toner image forming unit disposed on the downstream side in the transport direction with respect to the color toner image forming unit, the black toner image forming unit A black toner image is formed on the intermediate transfer member by transferring the black toner image formed on the photosensitive member provided in the toner image forming unit to a part of one color toner image among a plurality of color toner images. .
[0054]
After the color toner image and the black toner image are formed on the intermediate transfer member in this way, the density of the color toner image on the intermediate transfer member is detected by the density detecting means, and the detected density detection value of the color toner image is detected. Is determined by the determining means.
[0055]
Here, when it is determined that the density detection value of the color toner image is within a predetermined appropriate density range, the second control unit performs control so that the density detection unit detects the density of the black toner image.
[0056]
Like this 5 Also in the color image forming apparatus according to the invention, since the black toner image forming means is disposed downstream of the color toner image forming means in the transport direction of the intermediate transfer member, immediately after forming a plurality of color toner images. In addition, a black toner image can be formed on a part of one color toner image (before the intermediate transfer member is conveyed at least half a round path), and the time required for forming the color toner image and the black toner image Is shorter than before. Accordingly, it is possible to efficiently detect the density of the black toner image in the color image forming apparatus.
[0057]
On the other hand, when the density detection value of the color toner image is not within the predetermined appropriate density range, the second control unit performs the color toner image forming unit so that the density of the color toner image is within the predetermined appropriate density range. It is desirable to adjust. Then, a plurality of color toner images are formed again on the intermediate transfer member by the adjusted color toner image forming unit, and a black toner image forming unit is formed on a part of one of the formed color toner images. The black toner image is formed again by the method, the density of any other color toner image is detected again by the density detecting means, and it is determined whether or not the detected density detection value is within a predetermined appropriate density range. It is desirable to control so as to make a determination again.
[0058]
By the way, the density detecting means may be constituted by a single sensor arranged on the downstream side in the transport direction with respect to the black toner image forming means. For example, the color toner image forming means converts YMC three color toner images into an intermediate transfer body. In this case, the density of the three color toner images may be sequentially detected by one sensor.
[0059]
Further, the density detecting means may be constituted by a plurality of sensors arranged for each color on the downstream side in the transport direction with respect to the black toner image forming means. For example, the color toner image forming means generates a YMC three color toner image. When formed on the intermediate transfer member, the density of the three color toner images can be detected in parallel by a plurality of (three) sensors arranged for each color, so that the density detection processing efficiency is good.
[0060]
Also, here, for example, as a plurality of color toner images, two color toner images for each color of YMC are formed on the intermediate transfer body side by side with a predetermined interval along the transport direction, and among these, the upstream side in the transport direction If the black toner image is formed so as to overlap a part of the color toner image, the density of the color toner image on the downstream side in the transport direction is detected by the sensor, and then the detected density is within a predetermined appropriate density range. If it is determined that the density of the black toner image superimposed on the color toner image on the upstream side in the transport direction can be immediately detected by the sensor, the density of the color toner image and the black toner image can be detected very efficiently. Can be detected.
[0061]
3B shows the spectral characteristics of the yellow toner image, FIG. 4B shows the spectral characteristics of the magenta toner image, and FIG. 5B shows the spectral characteristics of the cyan toner image. FIG. 6B shows the spectral characteristics of the black toner image. The reflectance of the yellow toner image is higher than that of the magenta or cyan toner image. It can be seen that the difference from the reflectance of the image is the largest.
[0062]
Therefore, when the density of the black toner image is detected using the yellow toner image as the background, the difference in reflectance between the background and the black toner image becomes the largest, for example, the reflected light amount of the background and the reflected light amount of the black toner image. When the density of the black toner image is detected from the ratio or difference (when a general black toner image density detection procedure is used), the density can be detected with the highest accuracy.
[0063]
As a result, when the color toner image forming unit is composed of a yellow image forming unit, a magenta image forming unit, and a cyan image forming unit, the yellow image forming unit is disposed closest to the black toner image forming unit. It is desirable to do. That is, the time from the formation of the yellow color toner image on the intermediate transfer member by the yellow image forming unit to the formation of the black toner image on the intermediate transfer member by the black toner image forming unit can be shortened. A black toner image with a yellow color toner image as a base, which can detect the density with the highest accuracy, can be formed on the intermediate transfer member in a shorter time, and the density can be detected.
[0064]
Next, as a color image forming apparatus for performing black image density detection based on the black image density detection method according to the third invention described above, 6 And a color image forming apparatus according to the invention.
[0065]
This first 6 In the color image forming apparatus according to the invention, the color toner image forming means applies two color toner images of the same density to the photosensitive member provided in the color toner image forming means so that the density of each set differs. And a plurality of sets of color toner images are formed on the intermediate transfer member by transferring the formed color toner images to the intermediate transfer member. The black toner image forming means disposed downstream of the color toner image forming means in the transport direction of the intermediate transfer member forms a black toner image on the photosensitive member provided in the black toner image forming means, and the black toner A black toner image is formed on the intermediate transfer member by transferring the image so as to overlap a part of one color toner image of each set of color toner images on the intermediate transfer member.
[0066]
Further, the density detection means detects the density of the other color toner image in each set of color toner images, and whether or not the detected density detection value of the other color toner image is within a predetermined appropriate density range. Is determined by the determining means.
[0067]
Here, if the density detection value of the other color toner image is within a predetermined appropriate density range, the third control means adjusts the density of the black toner image formed on one color toner image of the same set. Control is performed so as to be detected by the concentration detecting means.
[0068]
Similar to the above-described third invention, 6 Also in the color image forming apparatus according to the invention, a plurality of sets of color toner images having different densities are formed on the intermediate transfer member, so that at least one of the plurality of sets of color toner images is detected in the density of the other color toner image. There is a high possibility that the value falls within a predetermined appropriate concentration range. For this reason, it is confirmed with high probability that the density of one color toner image is appropriate, and the density of the black toner image can be promptly detected. Therefore, the density detection of the black toner image in the color image forming apparatus can be performed. It can be executed efficiently.
[0069]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, various embodiments according to the present invention will be described in detail with reference to the drawings.
[0070]
[First Embodiment]
First, claims 1, 2, and 6 , 7 A first embodiment corresponding to the invention will be described.
[0071]
(Configuration of color image forming apparatus)
Hereinafter, the configuration of the color image forming apparatus according to the present embodiment will be described first. As shown in FIG. 1, the color image forming apparatus 10 exposes and scans an image of a document 16 placed at a predetermined position on a platen glass 14 and converts it into image signal data read by a CCD sensor 13. 12 and an image forming unit 18 that forms a color image on a sheet 50 according to a procedure to be described later based on image signal data obtained by reading an image by the image reading device 12.
[0072]
Among these, the image forming unit 18 includes an image storage unit 82 that stores image signal data obtained by reading an image with the CCD sensor 13, and a process in the color image forming apparatus 10 that includes a CPU, ROM, RAM, and the like. A control unit 80 for controlling the whole is provided.
[0073]
The image forming unit 18 includes an endless belt-shaped intermediate transfer belt 30, a yellow image forming unit 20 that forms a yellow toner image on the intermediate transfer belt 30, and a magenta toner image on the intermediate transfer belt 30. A magenta image forming unit 22 that forms a cyan toner image on the intermediate transfer belt 30, and a black image forming unit 26 that forms a black toner image on the intermediate transfer belt 30. Is provided.
[0074]
Among these, the yellow image forming unit 20 is provided with a photoconductor 20C which is substantially cylindrical and rotates around the central axis in the direction of arrow A and whose outer peripheral surface is in contact with the intermediate transfer belt 30. In the vicinity of the outer peripheral surface of 20C, a charging device 20D that charges the outer peripheral surface to a predetermined potential, and modulates laser light based on image signal data, and irradiates the outer peripheral surface of the charged photoreceptor 20C with the modulated laser light. The latent image forming unit 20A that forms a latent image corresponding to the yellow component of the image, the developing device 20B that develops the latent image formed by the latent image forming unit 20A, and the development by the developing device 20B A transfer device 20F that transfers the yellow toner image to the intermediate transfer belt 30 and a cleaning device 20E that removes the toner from the outer peripheral surface of the photoreceptor 20C are provided in order along the arrow A direction. . In addition, a toner supply unit 20G that supplies yellow toner to the developing device 20B is provided in the vicinity of the developing device 20B. The laser beam from the latent image forming unit 20A is reflected by the mirror 20H and then irradiated to the outer peripheral surface of the photoreceptor 20C.
[0075]
As is clear from FIG. 1, the configurations of the other image forming units, that is, the magenta image forming unit 22, the cyan image forming unit 24, and the black image forming unit 26 are the same as those of the yellow image forming unit 20 described above. It is.
[0076]
The intermediate transfer belt 30 is a dielectric whose volume resistance is adjusted by carbon to electrostatically transfer the developed toner image. The intermediate transfer belt 30 is driven by a drive roll 32, 34, 36, 38 in a predetermined direction (an arrow between the drive rolls 32, 38). B direction). Here, the peripheral length of the intermediate transfer belt 30 is 1920 mm as an example, and the conveyance speed (process speed) of the intermediate transfer belt 30 is 160 mm / second. For this reason, the intermediate transfer belt 30 rotates in 12 seconds.
[0077]
Above the intermediate transfer belt 30, the four image forming units are arranged in the order of the arrow B in the order of the yellow image forming unit 20, the magenta image forming unit 22, the cyan image forming unit 24, and the black image forming unit 26. A density detector 28 is provided downstream of the black image forming unit 26 in the direction of arrow B.
[0078]
On the other hand, on the upstream side in the arrow B direction with respect to the yellow image forming unit 20, an adsorption roll 40 that maintains the surface potential of the intermediate transfer belt 30 at a predetermined potential in order to improve the toner adsorption property of the intermediate transfer belt 30. A cleaning device 42 that removes toner from the transfer belt 30 and a reference position detection sensor 44 that detects a reference position in the intermediate transfer belt 30 are sequentially provided.
[0079]
On the upper surface of the color image forming apparatus 10, an operation unit 84 is provided that includes a display 84A for displaying messages and the like, and a keyboard 84B for an operator to input various commands and the like.
[0080]
A paper storage unit 54 that stores paper 50 is provided below the image forming unit 18, and the uppermost paper 50 in the paper storage unit 54 is sent out to a predetermined paper transport path by a feed roll 52. The fed paper 50 is conveyed on the paper conveyance path by conveyance rollers 55, 56, and 58 and reaches the vicinity of the intermediate transfer belt 30. A transfer roll 60 is provided on the sheet conveyance path so as to be opposed to the conveyance roll 36 with the intermediate transfer belt 30 interposed therebetween. When the sheet 50 is conveyed through the nipping portion between the conveyance roll 36 and the transfer roll 60, an intermediate position is provided. A color image formed on the transfer belt 30 (a color image forming process will be described later) is transferred to the paper 50.
[0081]
The transferred paper 50 is transported to the fixing device 46 by the transport roll 62, subjected to fixing processing by the fixing device 46, and then discharged to the paper tray 64.
[0082]
Incidentally, as shown in FIG. 9A, the detection position by the density detection unit 28 and the transfer position 26G of the black toner image by the black image forming unit 26 are set at an interval of 100 mm. The black toner image transfer position 26G by the black image forming unit 26, the cyan toner image transfer position 24G by the cyan image forming unit 24, the magenta toner image transfer position 22G by the magenta image forming unit 22, and the yellow image forming unit. The yellow toner image transfer positions 20G by 20 are set at an interval of 196 mm. Further, the transfer position 20G of the yellow toner image and the detection position by the reference position detection sensor 44 are set at an interval of 320 mm along the circumferential conveyance path of the intermediate transfer belt 30.
[0083]
In addition, the ROM in the control unit 80 is used to adjust the density detection value of each color of YMCK so that it is within the reference range, and to the developing device according to the amount of deviation of the density detection value of each color of YMCK from the reference range. Information on the adjustment amount of the toner supply amount is stored in advance.
[0084]
(Configuration related to concentration detection)
By the way, as shown in FIG. 2, an LED 70 is provided in the vicinity of the density detection unit 28, and the density detection unit 28 detects the amount of reflected light emitted from the LED 70 onto the detection target surface. The density of the detection target is detected from the amount of reflected light. In addition, as LED70, the infrared type LED which inject | emits the laser beam of the wavelength (900 nm-1200 nm) of an infrared region is used, The reason is demonstrated below.
[0085]
FIG. 3A shows the yellow spectral sensitivity characteristic in the visible region, and FIG. 3B shows the yellow spectral sensitivity property in the infrared region. As is clear from these figures, the yellow spectral sensitivity characteristic is shown in FIG. It can be seen that 95% or more is reflected at wavelengths in the infrared region (900 nm to 1200 nm). Similarly, as shown in FIGS. 4A and 4B showing the spectral sensitivity characteristics of magenta and FIGS. 5A and 5B showing the spectral sensitivity characteristics of cyan, the magenta and cyan colors are clear. It can be seen that both reflect at 95% or more at wavelengths in the infrared region (900 nm to 1200 nm).
[0086]
On the other hand, since the spectral sensitivity characteristic of the intermediate transfer belt 30 serving as the background of the density detection target image is about 10 to 20%, light is emitted between the underlying intermediate transfer belt 30 and each color toner image at wavelengths in the infrared region. The difference in reflectance (that is, the difference ΔRY, ΔRM, ΔRC in the amount of reflected light when a predetermined amount of light shown in FIG. 7 is irradiated) becomes large, and the density of each color toner image can be detected with high accuracy. In order to realize such accurate concentration detection, an infrared type LED that emits laser light having a wavelength in the infrared region (900 nm to 1200 nm) was used as the LED 70.
[0087]
6A and 6B showing the black spectral sensitivity characteristics, black has a spectral sensitivity characteristic of 10% or less in the region of 350 nm to 1200 nm, and the intermediate transfer belt 30 and the black toner. Since the difference in light reflectance from the image is small, it is difficult to accurately detect the density of the black toner image using the intermediate transfer belt 30 as a base.
[0088]
Therefore, in this embodiment, as shown in FIG. 7, a black toner image 86 is formed on a part of the color toner image 88 formed on the intermediate transfer belt 30, and the black toner image 88 is used as a background. A concentration of 86 is detected. As a result, the difference in light reflectance between the underlying color toner image 88 (yellow toner image as an example in FIG. 7) and the black toner image 86 (that is, the amount of reflected light when irradiated with the predetermined amount of light shown in FIG. 7). The difference ΔRK) becomes large, and the density of the black toner image 86 can be detected with high accuracy.
[0089]
In this embodiment, the YMC color toner image and the black toner image are respectively formed in the regions on both sides along the width direction of the intermediate transfer belt 30. For this reason, a pair of density detectors 28 and LEDs 70 shown in FIG. 2 are also provided.
[0090]
(Overview of color image formation processing)
Next, an outline of the color image forming process executed in the color image forming apparatus 10 will be described with reference to the flowchart of FIG. Note that the color image forming process described below is executed by the control unit 80.
[0091]
First, in step 100 of FIG. 8, the image reading device 12 reads an image of the document 16 placed at a predetermined position on the platen glass 14 by the CCD sensor 13, and in the next step 102, the reading of step 100 is performed. The image signal data obtained in the above is converted into YMCK color image signals.
[0092]
Then, in the next step 104, in each of the black image forming unit 26, the cyan image forming unit 24, the magenta image forming unit 22, and the yellow image forming unit 20, each color toner image based on the image signal of each color is as follows. Are formed on the photoreceptor of each forming portion. For example, in the yellow image forming unit 20, the surface of the photoreceptor 20C rotating in the direction of arrow A is charged to a predetermined potential by the charging device 20D, and the laser is modulated on the charged surface by the yellow image signal by the latent image forming unit 20A. By irradiating light, a latent image corresponding to the yellow component of the image is formed. The latent image is developed by the developing device 20B to be visualized as a yellow toner image. In the image forming units other than the yellow image forming unit 20, similarly, a toner image of each color or a black toner image is formed on the photoreceptor of each image forming unit.
[0093]
In the next step 106, the intermediate transfer belt 30 is conveyed, and the toner images of the respective colors are transferred onto the intermediate transfer belt 30 so as to form a target color image.
[0094]
Specifically, a yellow toner image is first transferred to the intermediate transfer belt 30 rotating in the direction of arrow A in FIG. 1 by the transfer device 20F of the yellow image forming unit 20 on the most upstream side in the direction of arrow B in FIG. Is done. Since the intermediate transfer belt 30 is conveyed in the direction of arrow B between the drive rollers 32 and 38 where the toner image is transferred by the image forming units to the intermediate transfer belt 30, the intermediate transfer belt 30 used below is used. The conveying direction of FIG. 1 means the direction of arrow B in FIG.
[0095]
Then, the magenta toner image is transferred onto the yellow toner image forming portion of the intermediate transfer belt 30 by the transfer device of the magenta image forming portion 22. Thereafter, similarly, a cyan toner image is transferred by the transfer device of the cyan image forming unit 24, and a black toner image is transferred in succession by the transfer device of the black image forming unit 26. As described above, the four color toner images of YMCK are transferred onto the intermediate transfer belt 30 so as to form a target color image on the intermediate transfer belt 30.
[0096]
In the next step 108, the color image formed on the intermediate transfer belt 30 as described above is transferred by the transfer roll 60 to the paper 50 that has been transported along a predetermined paper transport path. As a result, a target color image is formed on the paper 50.
[0097]
In the next step 110, as post-processing, the paper 50 on which the color image has been formed is discharged to the paper tray 64, the toner on the intermediate transfer belt 30 is removed by the cleaning device 42, and the cleaning device for each image forming unit. The toner on each photoconductor is removed by the above, and the process is terminated.
[0098]
Through the color image forming process as described above, the image of the document 16 is formed on the paper 50, and the paper 50 on which the image is formed can be obtained.
[0099]
Note that the image signal data to be converted into the YMCK color image signals in step 102 is not limited to the image signal data obtained by reading the document with the image reading device 12 in step 100, and the image signal data in advance. It may be image signal data that has been read by the reading device 12 and stored in the image storage unit 82, or image signal data that is input from an external image reading device via a communication line (not shown).
[0100]
(Operation of the first embodiment)
Next, as the operation of the first embodiment, the density adjustment processing of the black image according to the present invention among the density adjustment processing of each color of YMCK will be described with reference to the flowchart of FIG. This density adjustment processing is executed under the control of the control unit 80 when the color image forming apparatus 10 is turned on and at a predetermined time interval. Of course, even when the installation environment of the color image forming apparatus 10 changes suddenly, it is desirable that the operator manually execute the density adjustment process. For example, the temperature changes by 3 degrees or more after the previous density adjustment process is executed. It is desirable to execute the density adjustment process when the humidity has changed or when the humidity has changed by 20% or more.
[0101]
In step 120 of FIG. 10, the conveyance rolls 32, 34, 36, and 38 are driven to start conveyance of the intermediate transfer belt 30 in the arrow B direction. In the next step 122, the black image forming unit 26, the cyan image forming unit 24, the magenta image forming unit 22, and the yellow image forming unit 20 are based on image signal data of a pattern image to be described later stored in advance in the image storage unit 82. Each YMCK pattern image is formed on each photoconductor. Here, for each YMC color, a 15 mm × 15 mm square pattern image with an image signal density of 50% (hereinafter referred to as Cin = 50%) and a 20 mm × 20 mm square pattern image with Cin = 100% are formed. For black, a square pattern image of 15 mm × 15 mm with Cin = 50% is formed.
[0102]
Note that the image signal data of the pattern image may not be stored in the image storage unit 82 in advance, and image signal data of the pattern image supplied from a pattern generator (not shown) may be used.
[0103]
In the next step 124, the yellow image forming unit 20, the magenta image forming unit 22, and the cyan image forming unit 24 (hereinafter, these three are collectively referred to as a color image forming unit) 15 mm × Cin = 50% of each color of YMC. By transferring a 15 mm square pattern image from each photoconductor to the intermediate transfer belt 30, a YMC square pattern image is formed on the intermediate transfer belt 30. Hereinafter, a square pattern image of Cin = 50% of the color (any of YMC) formed on the intermediate transfer belt 30 is referred to as a 50% color density patch.
[0104]
Note that the formation timing of the 50% density patch on the intermediate transfer belt 30 in steps 122 and 124 is determined by the reference position sensor 44 using the reference mark of the intermediate transfer belt 30 (for example, # 850 polyester silver color manufactured by Sumitomo 3M Limited). ) Is detected by the yellow image forming unit 20 after 2.0 seconds (= distance 320 mm between the reference position sensor 44 and the yellow toner image transfer position 20G ÷ process speed 160 (mm / second)). Control is performed so that the yellow 50% density patch is transferred to the intermediate transfer belt 30.
[0105]
Thereafter, as shown in FIG. 9B, the magenta 50% density patch is spaced from the yellow 50% density patch by a distance of 5 mm by the magenta image forming unit 22, and the magenta color by the cyan image forming unit 24. A cyan 50% density patch is formed on the intermediate transfer belt 30 with a space of 5 mm from the 50% density patch.
[0106]
In the next step 126, when the 50% density patch of each color of YMC shown in FIG. 9B reaches the detection position of the density detection unit 28, each density is detected by the density detection unit 28. As described above, a pair of 50% density patches of each color of YMC is formed, and the density is detected by the density detection unit 28 for each of them. The two density detection values here are added and averaged in order to reduce the detection error, and this added average value is used as a density detection value in the subsequent determination processing and the like.
[0107]
In the next step 130, it is determined whether or not all the detected density values of the 50% density patches of each color of YMC are within a predetermined reference range. As the reference range here, for example, when the density is detected by an output voltage correlated with the amount of light reflected from the target density patch, a range of 1 V to ± 0.2% corresponding to 50% density may be adopted. it can.
[0108]
Here, if any one of the detected density values of each color of YMC is not within the reference range, the process proceeds to step 132, and it is determined whether or not all detected density values of each color of YMC are out of the reference range. If all the detected density values of each color of YMC are outside the reference range, the process proceeds to step 134, and the adjustment amount of the toner supply amount corresponding to the deviation amount of the detected density value of each color from the reference range is set in the ROM in the control unit 80. The toner supply amount by the toner supply unit is adjusted by the adjustment amount in each color image forming unit. Then, the process returns to step 122, and a pattern image is formed again by each adjusted color image forming unit.
[0109]
On the other hand, if at least one of the density detection values of each color of YMC is within the reference range in step 132, the process proceeds to step 136, and the color image formation in which the density detection value of the formed color density patch is out of the reference range. As with step 134, the toner supply amount is adjusted by the toner supply unit.
[0110]
After the adjustment in step 136 is completed, and if all the density detection values of each color of YMC are within the reference range in step 130, the process proceeds to step 138, and the color density where the density detection value is within the reference range. By transferring a 20 mm × 20 mm square pattern image of Cin = 100% of the color to the intermediate transfer belt 30 by the color image forming unit of the same color as the patch, the square pattern of the color is transferred onto the intermediate transfer belt 30. Form an image. Hereinafter, a square pattern image of Cin = 100% of the color (any of YMC) formed on the intermediate transfer belt 30 is referred to as a 100% color density patch.
[0111]
Specifically, as shown in FIG. 9 (B), a 100% density patch of magenta color is spaced from a yellow 100% density patch with an interval of 5 mm, and an interval of 5 mm is spaced from the 100% density patch of magenta color. A 100% density patch of cyan color is formed on the intermediate transfer belt 30.
[0112]
In the next step 140, as shown in FIG. 9B, a black Cin = 50% 15 mm × 15 mm square pattern image is superimposed and transferred onto the 100% density patch of each color by the black image forming unit 26. Thus, a black square pattern image is formed on the intermediate transfer belt 30 (however, FIG. 9B shows an example in which the density detection values of each color of YMC are all within the reference range). Hereinafter, the black square pattern image formed on the intermediate transfer belt 30 is referred to as a black density patch.
[0113]
In the next step 142, when the black density patch reaches the detection position of the density detection unit 28, the density is detected by the density detection unit 28. A pair of black density patches is also formed in the same manner as the density patches for each color of YMC, and the density is detected by the density detection unit 28 for each. The two density detection values here are added and averaged in order to reduce detection errors, and this added average value is used as a density detection value in subsequent determination processing and the like.
[0114]
In the next step 144, it is determined whether or not the density detection value of the black density patch is within a predetermined reference range. As the reference range here, for example, when the density is detected by an output voltage correlated with the amount of light reflected from the target density patch, a range of 1 V to ± 0.2% corresponding to 50% density may be adopted. it can.
[0115]
In this embodiment, as an example, as the density detection value of the black density patch to be determined in step 144, the density detection value of the black density patch with the yellow 100% density patch as the background, the 100% density of magenta color It is assumed that the density detection value of the black density patch with the patch as the background and the density detection value of the black density patch with the cyan 100% density patch as the background are used with priority. That is, from the spectral sensitivity characteristics of FIGS. 3B, 4B, and 5B, yellow, magenta, and black are used as the background of the black toner image in terms of the high reflectance and its stability. Since the colors are suitable in the order of cyan, the priority order as described above is adopted.
[0116]
If the black density detection value is not within the reference range, the process proceeds to step 146, where the toner supply amount adjustment amount corresponding to the deviation amount of the density detection value from the reference range is read from the ROM in the control unit 80, and the black color is detected. In the image forming unit 26, the toner supply amount by the toner supply unit is adjusted by the adjustment amount.
[0117]
After such adjustment is completed and if the black density detection value is within the reference range in step 144, the process proceeds to step 148 to inform the display 84A of the operation unit 84 that the black image density adjustment processing has been completed. As a post-processing, the toner on the intermediate transfer belt 30 is removed by the cleaning device 42 and the toner on each photoconductor is removed by the cleaning device of each image forming unit, and the conveyance of the intermediate transfer belt 30 is stopped. Then, the process ends.
[0118]
After determining that the density detection values of all the color density patches are out of the reference range in step 132 and completing the adjustment of each color image forming unit in step 134, the process returns to steps 122 and 124, and FIG. As shown in FIG. 9, color density patches (described as C complement, M complement, and Y complement in FIG. 9C) are formed again by each adjusted color image forming unit, and color density patches are executed in steps 126 to 132. The density detection and determination are performed again.
[0119]
According to the first embodiment described above, since the black image forming unit 26 is disposed downstream of the color image forming unit in the conveyance direction of the intermediate transfer belt 30, the color density patch on the intermediate transfer belt 30 is formed. The portion (color density patch forming portion) reaches the black image forming portion 26 before the intermediate transfer belt 30 makes a half turn.
[0120]
For this reason, since the color density patch forming unit reaches the black image forming unit 26 earlier than the conventional case where the black image forming unit 26 is arranged on the upstream side of the color image forming unit in the transport direction. It is possible to quickly form a black density patch on the color density patch and quickly perform density detection of the black density patch, density adjustment of a black image, and the like. This makes it possible to efficiently execute the black image density adjustment processing.
[0121]
[Second Embodiment]
Next, the claims described in the claims 8 A second embodiment corresponding to the invention will be described. The configuration of the color image forming apparatus 10 in the second embodiment is different from that in the first embodiment in that a density detection unit 28 is provided for each image forming unit as shown in FIG.
[0122]
That is, the density detection unit 28K corresponding to the black image forming unit 26, the density detection unit 28C corresponding to the cyan image forming unit 24, and the density detection unit 28M corresponding to the magenta image forming unit 22 form the yellow image. Corresponding to the unit 20, the density detection unit 28 </ b> Y is installed on the downstream side in the conveyance direction (arrow B direction) of the intermediate transfer belt 30. Further, the detection position by each density detection unit and the transfer position by the corresponding image forming unit are set at an interval of 100 mm (for example, 100 mm between the detection position by the density detection unit 28Y and the transfer position 20G of the yellow toner image). Set to). Since the configuration other than the above is the same as that of the first embodiment, the description thereof is omitted.
[0123]
(Operation of Second Embodiment)
Next, as an operation of the second embodiment, black image density adjustment processing will be described with reference to the flowchart of FIG. The execution timing of the density adjustment process in the second embodiment is the same as the execution timing of the density adjustment process in the first embodiment. In the flowchart of FIG. 12, the same step numbers are assigned to the same processing steps as those of the flowchart of FIG. 10 described above, and detailed description of the processing steps is omitted.
[0124]
In step 120 of FIG. 12, the conveyance rollers 32, 34, 36, and 38 are driven to start conveyance of the intermediate transfer belt 30 in the direction of arrow B. In the next step 122, the image is stored in advance in the image storage unit 82. Based on image signal data of a pattern image to be described later, the following YMCK pattern images are formed on each photoconductor in each image forming unit. Here, a 20 mm × 20 mm square pattern image of Cin = 100% is formed for each color of YMC, and a 15 mm × 15 mm square pattern image of Cin = 50% is formed for black.
[0125]
In the next step 123, each color image forming unit transfers a 20 mm × 20 mm square pattern image of Cin = 100% of each color of YMC from each photoconductor to the intermediate transfer belt 30, so that the YMC is transferred onto the intermediate transfer belt 30. A square pattern image (100% color density patch) of each color is formed, and in the next step 126, the density of the 100% density patch of each color of YMC is detected by the density detection unit 28 corresponding to each color image forming unit. That is, the density of the yellow color density patch is detected by the density detector 28Y, the density of the magenta color density patch is detected by the density detector 28M, and the density of the cyan color density patch is detected by the density detector 28C. In the second embodiment, since the density detection unit 28 is installed on the downstream side in the conveyance direction of the intermediate transfer belt 30 with respect to each image forming unit, after the 100% color density patch of each color is formed in step 123, immediately. Density detection can be performed by the density detection unit 28 corresponding to each color image forming unit.
[0126]
In the next step 130, it is determined whether or not all the detected density values of the 100% density patch for each color of YMC are within a predetermined reference range. As the reference range here, for example, when the density is detected by an output voltage correlated with the amount of light reflected from the target density patch, a range of 2 V to ± 0.2% corresponding to 100% density may be adopted. it can.
[0127]
Here, if any one of the detected density values of each color of YMC is not within the reference range, the process proceeds to step 132, and it is determined whether or not all detected density values of each color of YMC are out of the reference range. If all the detected density values of each color of YMC are outside the reference range, the process proceeds to step 134, and the adjustment amount of the toner supply amount corresponding to the deviation amount of the detected density value of each color from the reference range is set in the ROM in the control unit 80. The toner supply amount by the toner supply unit is adjusted by the adjustment amount in each color image forming unit. Then, the process returns to step 122, and a pattern image is formed again by each adjusted color image forming unit.
[0128]
On the other hand, if at least one of the density detection values of each color of YMC is within the reference range in step 132, the process proceeds to step 136, and the color image formation in which the density detection value of the formed color density patch is out of the reference range. As with step 134, the toner supply amount is adjusted by the toner supply unit.
[0129]
After the adjustment in step 136 is completed, and if the density detection values of each color of YMC are all within the reference range in step 130, the process proceeds to step 139, and as shown in the lower part of FIG. On the intermediate transfer belt 30, a black image forming unit 26 transfers a black Cin = 50% 15 mm × 15 mm square pattern image onto the color density patch whose density detection value was within the reference range. A black density patch is formed.
[0130]
In this way, in the second embodiment, as shown in FIG. 11B, a black density patch is formed on the color density patch that is the target of density detection in step 126, and the black density patch is formed in the next step 142. When the detection position of the concentration detector 28K is reached, the concentration is detected by the concentration detector 28K. However, FIG. 11B shows an example in which the density detection values of each color of YMC are all within the reference range.
[0131]
Thereafter, as in the first embodiment, it is determined whether or not the density detection value of the black density patch is within a predetermined reference range (step 144). If the density detection value of black is within the reference range, If not, the adjustment amount of the toner supply amount corresponding to the deviation amount of the density detection value from the reference range is read from the ROM in the control unit 80, and the toner supply amount by the toner supply unit in the black image forming unit 26 is set to the adjustment amount. Only the adjustment is made (step 146).
[0132]
Then, after the completion of such adjustment and if the black density detection value is within the reference range in step 144, the fact that the black image density adjustment processing has been completed is displayed on the display 84A of the operation unit 84. As post-processing, the toner on the intermediate transfer belt 30 is removed by the cleaning device 42 and the toner on each photoconductor is removed by the cleaning device of each image forming unit, and the conveyance of the intermediate transfer belt 30 is stopped ( Step 148), the process ends.
[0133]
Note that, after the density detection values of all color density patches are determined to be out of the reference range in step 132 and the adjustment of each color image forming unit is completed in step 134, the process returns to steps 122 and 123, and FIG. As shown in FIG. 11, each adjusted color image forming unit forms a color density patch (described as “Y” in FIG. 11C) again, and the density detection and determination of the color density patch are performed in steps 126 to 132. Try again.
[0134]
In the second embodiment described above, since the density detection unit 28 is disposed downstream of the image forming unit in the conveyance direction of the intermediate transfer belt 30, the 100% color density patch for each color as a base is formed and then quickly. In addition, it is possible to detect the density of the color density patch, and to form a black density patch on the color density patch that is the target of density detection, and to quickly detect the density of the black density patch. Therefore, it is possible to efficiently execute the black image density adjustment processing.
[0135]
[Third Embodiment]
Next, claims 3, 4, and 9 , 10 , 11 A third embodiment corresponding to the invention will be described. Note that the configuration of the color image forming apparatus 10 according to the third embodiment is the same as that of the first embodiment, and a description thereof will be omitted.
[0136]
(Operation of the third embodiment)
Next, as an operation of the third embodiment, black image density adjustment processing will be described with reference to the flowchart of FIG. The execution timing of the density adjustment process in the third embodiment is the same as the execution timing of the density adjustment process in the first embodiment. In the flowchart of FIG. 15, the same step numbers are assigned to the same processing steps as those in the flowchart of FIG. 10 in the first embodiment described above, and detailed description of the processing steps is omitted.
[0137]
In step 120 of FIG. 15, the conveyance rolls 32, 34, 36, and 38 are driven to start conveyance of the intermediate transfer belt 30 in the arrow B direction. Based on image signal data of a pattern image to be described later, the following YMCK pattern images are formed on each photoconductor in each image forming unit. Here, a 15 mm × 15 mm square pattern image with Cin = 50% and a 20 mm × 20 mm square pattern image with Cin = 100% are formed for each color of YMC, and 15 mm × Cin = 50% with black. A 15 mm square pattern image is formed.
[0138]
In the next step 125, each color image forming unit generates a 15 mm × 15 mm square pattern image of Cin = 50% and a 20 mm × 20 mm square pattern image of Cin = 100% from each photoconductor to the intermediate transfer belt 30. By transferring, 50% color density patches and 100% color density patches of each color of YMC are formed on the intermediate transfer belt 30.
[0139]
Note that the formation timing of the 50% density patch on the intermediate transfer belt 30 in steps 122 and 125 is determined by the reference position sensor 44 using the reference mark of the intermediate transfer belt 30 (for example, # 850 polyester silver color manufactured by Sumitomo 3M Limited). The yellow image forming unit 20 controls to transfer the yellow 50% density patch to the intermediate transfer belt 30 2.0 seconds after the detection of the (seal etc. in FIG. 14). (It is described that the first yellow 50% density patch Y1 is formed on the intermediate transfer belt 30 after 2.0 seconds from TR0).
[0140]
Thereafter, as shown in FIG. 13B, following the yellow 50% density patch, the magenta 50% density patch, the cyan 50% density patch, the yellow 100% density patch, and the magenta color 100%. A density patch and a cyan 100% density patch are formed on the intermediate transfer belt 30 with an interval of 5 mm along the conveyance direction of the intermediate transfer belt 30.
[0141]
In the next step 127, on the 100% color density patch of each color shown in FIG. 13B formed in step 125 above, the black image forming unit 26 uses a black Cin = 50% 15 mm × 15 mm square pattern image. As a result, the black density patch is formed on the intermediate transfer belt 30. As described above, in the third embodiment, the color density patch and the black density patch are formed on the intermediate transfer belt 30 before the density detection of the color density patch and the black density patch is performed.
[0142]
In the next step 128, when the 50% color density patch of each color of YMC shown in FIG. 13B reaches the detection position of the density detection unit 28, each density is detected by the density detection unit 28. In step 130, it is determined whether or not all the detected density values of the 50% density patches of each color of YMC are within a predetermined reference range.
[0143]
Here, if any one of the detected density values of each color of YMC is not within the reference range, the process proceeds to step 132, and it is determined whether or not all detected density values of each color of YMC are out of the reference range. If all the detected density values of each color of YMC are outside the reference range, the process proceeds to step 134, and the adjustment amount of the toner supply amount corresponding to the deviation amount of the detected density value of each color from the reference range is set in the ROM in the control unit 80. The toner supply amount by the toner supply unit is adjusted by the adjustment amount in each color image forming unit. Then, the process returns to step 122, and a pattern image is formed again by each adjusted color image forming unit.
[0144]
On the other hand, if at least one of the density detection values of each color of YMC is within the reference range in step 132, the process proceeds to step 136, and the color image formation in which the density detection value of the formed color density patch is out of the reference range. As with step 134, the toner supply amount is adjusted by the toner supply unit.
[0145]
After the adjustment in step 136 is completed, and in step 130, if all the density detection values of each color of YMC are within the reference range, the process proceeds to step 141, and the color density where the density detection value is within the reference range. The density detection unit 28 detects the density of the black density patch on the 100% color density patch of the same color as the patch when the black density patch reaches the detection position of the density detection unit 28.
[0146]
Thereafter, as in the first embodiment, it is determined whether or not the density detection value of the black density patch is within a predetermined reference range (step 144). If the density detection value of black is within the reference range, If not, the adjustment amount of the toner supply amount corresponding to the deviation amount of the density detection value from the reference range is read from the ROM in the control unit 80, and the toner supply amount by the toner supply unit in the black image forming unit 26 is set to the adjustment amount Only the adjustment is made (step 146).
[0147]
Then, after the completion of such adjustment and if the black density detection value is within the reference range in step 144, the fact that the black image density adjustment processing has been completed is displayed on the display 84A of the operation unit 84. As post-processing, the toner on the intermediate transfer belt 30 is removed by the cleaning device 42 and the toner on each photoconductor is removed by the cleaning device of each image forming unit, and the conveyance of the intermediate transfer belt 30 is stopped ( Step 148), the process ends.
[0148]
If it is determined in step 132 that the density detection values of all the color density patches are out of the reference range, each color image forming unit is adjusted in step 134, and then the process returns to steps 122 and 125, and FIG. As shown in (C), a color density patch (correction patch in FIG. 13C) is formed again by each adjusted color image forming unit, and the density detection of the color density patch is performed again.
[0149]
Here, as shown in FIG. 14, for example, for the corrected yellow color density patch (Y complement), the density detection is performed on the previous yellow color density patch (Y1), and then 4. After 5 seconds, density detection is performed. The 4.5 seconds is obtained by (the distance between the yellow image forming unit 20 and the density detecting unit 28 / process speed) + the response time, where the response time is 200 milliseconds. That is, (688/160) + 0.2 = 4.5.
[0150]
In the third embodiment described above, unlike the first and second embodiments, the color density patch and the black density patch are first formed on the intermediate transfer belt 30, and then the density of the color density patch and the black density patch is changed. Although the detection is executed, even in such a procedure, the black image forming unit 26 is arranged downstream of the color image forming unit in the transport direction of the intermediate transfer belt 30, and thus two color density patches. After forming (Cin = 50%, 100%), the black density patch can be immediately formed on the 100% color density patch on the upstream side in the transport direction, thereby forming the color density patch and the black density patch. The time required is shorter than before.
[0151]
Also, since the black density patch is formed on the 100% color density patch on the upstream side in the transport direction of the two color density patches, the density of the 50% color density patch on the downstream side in the transport direction is detected in step 128 and then immediately. In step 141, the density of the black density patch on the 100% color density patch upstream in the transport direction can be detected.
[0152]
As described above, according to the third embodiment, it is possible to efficiently execute the black image density adjustment processing.
[0153]
[Fourth Embodiment]
Next, the claims described in the claims 12 , 13 A fourth embodiment corresponding to the invention will be described.
[0154]
In the color image forming apparatus 10 according to the fourth embodiment, as shown in FIG. 16A, four image forming units along the conveyance direction (arrow B direction) of the intermediate transfer belt 30 are magenta image forming units. 22, the cyan image forming unit 24, the yellow image forming unit 20, and the black image forming unit 26 are arranged in this order, and the density detecting unit 28 on the downstream side of the black image forming unit 26 is as shown in FIG. The three density detectors 28Y, 28M, and 28C are arranged along the width direction of the intermediate transfer belt 30. Since other configurations are the same as those of the first embodiment, description thereof is omitted.
[0155]
(Operation of the fourth embodiment)
Next, black image density adjustment processing will be described as an operation of the fourth embodiment. The procedure of black image density adjustment processing in the fourth embodiment is the same as in the third embodiment, and the flowchart of FIG. 15 can be applied.
[0156]
However, in the fourth embodiment, in step 125 of FIG. 15, 50% color density patches (15 mm × 15 mm) of each color of YMC are formed along the width direction of the intermediate transfer belt 30 as shown in FIG. Further, 100% color density patches (20 mm × 20 mm) of each color of YMC are formed along the width direction of the intermediate transfer belt 30 with an interval of 5 mm along the transport direction.
[0157]
In the next step 127, a black 50% density patch (15 mm × 15 mm) is superimposed on the 100% color density patch of each color shown in FIG. 16B formed in step 125 by the black image forming unit 26. Form.
[0158]
In the next step 128, the density detection unit 28Y in FIG. 16B sets the density of the yellow 50% color density patch, the density detection unit 28M sets the density of the magenta 50% color density patch, and the density detection unit 28C. The density of the cyan 50% color density patch is detected in parallel.
[0159]
Thereafter, when the density detection of the black density patch is performed in step 141, the color closest to the black image forming unit 26 among the background color density patches whose density detection value is determined to be within the reference range in step 130. The density of the black density patch on the color density patch formed by the image forming unit is detected by the corresponding density detection unit 28 (any one of the density detection units 28Y, 28M, and 28C).
[0160]
By the way, assuming a case where the density of the color density patch is not appropriate and the process returns to step 122 again to recreate the color density patch as the background, as shown in FIG. 16C and FIG. The yellow color density patch re-formed by the yellow image forming unit 20 closest to 26 is detected in 2.05 seconds after the previous density detection / determination. The 2.05 seconds is obtained by (the distance between the yellow image forming unit 20 and the density detecting unit 28 / process speed) + the response time, where the response time is 200 milliseconds. That is, (296/160) + 0.2 = 2.05.
[0161]
On the other hand, the density of the cyan color density patch re-formed by the cyan image forming unit 24 is detected in 3.275 seconds, and that of the magenta color density patch re-formed by the magenta image forming unit 22 is 4.5 seconds. The concentration is detected. Note that 3.275 = (distance between cyan image forming unit 24 and density detecting unit 28 / process speed) + response time = ((492/160) +0.2). 4.5 = (distance between magenta image forming unit 22 and density detecting unit 28 / process speed) + response time = ((688/160) +0.2).
[0162]
Therefore, by setting the density of the black density patch on the color density patch formed by the color image forming unit closest to the black image forming unit 26 as described above as the detection target, the density of the color density patch is not appropriate and color When the density patch is re-formed, the color density patch can be re-formed and the density can be detected earliest.
[0163]
In the fourth embodiment, the density of the YMC 50% color density patch can be detected in parallel by the three density detection units, so that the density detection processing efficiency is good and the color density patch is restored as described above. Formation can be performed quickly, and black density adjustment processing can be performed efficiently.
[0164]
3B shows the spectral characteristics of the yellow toner image, FIG. 4B shows the spectral characteristics of the magenta toner image, and FIG. 5B shows the spectral characteristics of the cyan toner image. FIG. 6B shows the spectral characteristics of the black toner image. The reflectance of the yellow toner image is higher than that of the magenta or cyan toner image. It can be seen that the difference from the reflectance of the image is the largest. Therefore, when the density of the black density patch is detected using the yellow color density patch as the background, the difference in reflectance between the background and the black density patch is the largest, and the density can be detected with the highest accuracy.
[0165]
In the fourth embodiment, since the yellow image forming unit 20 is disposed closest to the black image forming unit 26, when recreating a color density patch as a base, the density detection of the black density patch is most accurately performed. Possible yellow background black density patches can be formed on the intermediate transfer belt 30 in a shorter time. That is, it is possible to efficiently execute the black density patch density detection with high accuracy.
[0166]
[Fifth Embodiment]
Next, claim 5 described in the claims, 14 A fifth embodiment corresponding to the invention will be described.
[0167]
In the color image forming apparatus 10 according to the fifth embodiment, as shown in FIG. 18A, four image forming units are arranged along the conveyance direction (arrow B direction) of the intermediate transfer belt 30 as yellow image forming units. 20, a magenta image forming unit 22, a cyan image forming unit 24, and a black image forming unit 26 are arranged in this order. The density detecting unit 28 on the downstream side of the black image forming unit 26 is as shown in FIG. As in the fourth embodiment, the image forming apparatus includes three density detection units 28Y, 28M, and 28C arranged along the width direction of the intermediate transfer belt 30. Since other configurations are the same as those of the first embodiment, description thereof is omitted.
[0168]
(Operation of the fifth embodiment)
Next, as an operation of the fifth embodiment, black image density adjustment processing will be described with reference to the flowchart of FIG. The execution timing of the density adjustment process in the fifth embodiment is the same as the execution timing of the density adjustment process in the first embodiment.
[0169]
In step 170 of FIG. 19, the conveyance rollers 32, 34, 36, and 38 are driven to start conveyance of the intermediate transfer belt 30 in the direction of arrow B, and in the next step 172, the image is stored in advance in the image storage unit 82. Based on image signal data of a pattern image to be described later, the following YMCK pattern images are formed on each photoconductor in each image forming unit. Here, for each color of YMC, two square pattern images having a different size of Cin = 100%, two square pattern images having a different size of Cin = 95%, and a size of Cin = 90% shown in FIG. Two different square pattern images, two square pattern images with different sizes of Cin = 85%, two square pattern images with different sizes of Cin = 80%, and two square pattern images with different sizes of Cin = 75% Form. The sizes are 15 mm × 15 mm and 20 mm × 20 mm. On the other hand, three square pattern images of 15 mm × 15 mm with Cin = 50% arranged side by side are formed in order.
[0170]
In the next step 174, as shown in FIG. 18B, each of the color image forming units forms the above-mentioned two sets of square pattern images for six sets (Cin = 100% to 75%) of the intermediate transfer belt 30. Then, the light is transferred from each light body to the intermediate transfer belt 30 so as to be formed in parallel with the YMC along the transport direction. Thus, two sets of color density patches are formed on the intermediate transfer belt 30 for six sets (Cin = 100% to 75%) in parallel with the YMC along the conveyance direction. However, in each of the above groups, the color density patch on the upstream side in the conveyance direction is formed to be 15 mm × 15 mm, and the color density patch on the downstream side is formed to be 20 mm × 20 mm.
[0171]
In the next step 176, as shown in FIG. 18B, the black image forming unit 26 applies black Cin = 50% 15 mm × on the 20 mm × 20 mm color density patch upstream in the transport direction in each set. A black density patch is formed on the intermediate transfer belt 30 by transferring the 15 mm square pattern image in an overlapping manner.
[0172]
In the next step 178, the density of the 100% density patch of each color of YMC is detected by the density detection unit 28 corresponding to each color image forming unit. That is, the density of the yellow color density patch is detected by the density detector 28Y, the density of the magenta color density patch is detected by the density detector 28M, and the density of the cyan color density patch is detected by the density detector 28C.
[0173]
Then, in the next step 180, it is determined whether or not all the density detection values of the color density patches for each color of YMC are within a predetermined reference range. As the reference range here, for example, when the density is detected by an output voltage correlated with the amount of light reflected from the target density patch, a range of 2 V to ± 0.2% corresponding to 100% density may be adopted. it can.
[0174]
Here, if any one of the detected density values of each of the YMC colors is not within the reference range, it is confirmed in step 181 that the above determination has not been completed for all color density patches, and the process proceeds to step 182. The adjustment processing of the color image forming unit in which the color density patch whose density detection value is outside the reference range is formed is activated. That is, the adjustment amount of the toner supply amount corresponding to the deviation amount of the density detection value of the color density patch from the reference range is read from the ROM in the control unit 80, and the toner supply amount by the toner supply unit in the target color image forming unit. Is adjusted by the adjustment amount.
[0175]
In step 182, the density of the color density patch of the next density is detected by the density detection unit 28 corresponding to each color image forming unit. Here, the density of the color density patch of the next Cin = 95% of 100% is the detection target, and the process returns to step 180, and the density detection values of the color density patches of each color of YMC are all within the predetermined reference range. It is determined whether or not. If the determination in step 180 is negative again, the process proceeds to step 182 again, and the density detection of the color density patch of the next density (Cin = 90%) is performed together with the adjustment process of the color image forming unit.
[0176]
If the density detection values of the color density patches of the respective colors of the YMC of the next density (Cin = 90%) are all within the reference range, the process proceeds to step 184, and the upstream side in the transport direction with the same set as the color density patch at that time. The densities of the three black density patches formed on the color density patch are detected by the density detection units 28Y, 28M, and 28C.
[0177]
As described above, in the fifth embodiment, the density detection / determination is performed in a predetermined order for a plurality of sets of color density patches formed on the intermediate transfer belt 30, and the black density is determined when the density of the color density patch is determined to be normal. Performs patch density detection. Therefore, the density of the three black density patches (black density patches K1, K2, and K3 shown in FIG. 18C) on the upstream side in the transport direction of the set of density (Cin = 90%) determined to be normal as described above. Is detected.
[0178]
Thereafter, as in the first embodiment, it is determined whether or not the detected density value of the black density patch is within a predetermined reference range (step 186), and if the detected density value of black is within the reference range. If not, the adjustment amount of the toner supply amount corresponding to the deviation amount of the density detection value from the reference range is read from the ROM in the control unit 80, and the toner supply amount by the toner supply unit in the black image forming unit 26 is set to the adjustment amount. Only the adjustment is made (step 188).
[0179]
Then, after completing such adjustment and if the black density detection value is within the reference range in step 186, the fact that the black image density adjustment processing has been completed is displayed on the display 84A of the operation unit 84 ( Step 190) As post-processing, the toner on the intermediate transfer belt 30 is removed by the cleaning device 42 and the toner on each photoconductor is removed by the cleaning device of each image forming unit, and the conveyance of the intermediate transfer belt 30 is stopped. (Step 192), and the process ends.
[0180]
If all the density detection values of each color are not determined to be within the reference range in step 180 for all sets of color density patches, an affirmative determination is made in step 181 to perform density detection and density adjustment of the black density patch. Instead, the post-process of step 192 is executed, and the process is terminated.
[0181]
In the fifth embodiment described above, a plurality of sets (for example, 6 sets) of color density patches having different densities are formed on the intermediate transfer belt 30 as color density patches serving as the background of the black density patch. In one set of color density patches, the density detection value of the color density patch is likely to be within the reference range. For this reason, it is possible to avoid a situation in which the color density patch as the background of the black density patch is formed again with a high probability, and it is possible to quickly detect and adjust the density of the black density patch. That is, the black image density adjustment process can be executed efficiently.
[0182]
In the first to fifth embodiments, the density adjustment of the color image and the black image is performed by adjusting the toner supply amount to the developing device in each image forming unit. You may carry out by adjusting a voltage, the charging bias voltage applied with a charging device, the transfer bias voltage in a transfer device, etc.
[0183]
The color image forming apparatus 10 according to the first to fifth embodiments is characterized in that the black image forming unit 26 is disposed downstream of the color image forming unit along the conveyance direction of the intermediate transfer belt 30. It is said. Among these, the fourth embodiment is characterized in that, among the three color image forming units, the yellow image forming unit 20 is arranged on the most downstream side and is closest to the black image forming unit 26. Therefore, in the fourth embodiment, the arrangement of the magenta image forming unit 22 and the cyan image forming unit 24 along the transport direction is not particularly limited. In the first to third and fifth embodiments, yellow image formation is performed. There are no particular restrictions on the arrangement of the three color image forming units of the unit 20, the magenta image forming unit 22, and the cyan image forming unit 24 along the transport direction.
[0184]
In addition to the black image density detection procedure of the first to fifth embodiments, a color density patch and a black density patch are formed on the intermediate transfer belt 30 to detect not only the density of the color density patch but also the black density patch. If density detection is also performed, and then the density detection value of the color density patch is within the reference range, the density detection value of the black density patch is adopted, and the density detection value of the color density patch is outside the reference range Alternatively, the procedure of not using the density detection value of the black density patch can be adopted.
[0185]
[ First reference Form]
next First reference A form is demonstrated.
[0186]
In addition, First reference The color image forming apparatus 10 in the embodiment has the same configuration as that of the first embodiment. However, First reference The color image forming apparatus 10 according to the embodiment has a function of forming a misregistration detection pattern (hereinafter referred to as a resist pattern) 600 shown in FIGS. 21 and 22A.
[0187]
Details will be described later. First reference 21, the color image forming apparatus 10 forms a registration pattern 600 on the intermediate transfer belt 30 at odd-numbered rotations of the intermediate transfer belt 30 and detects the position of the registration pattern 600, as shown in FIG. When the amount of deviation of the detected position from the position (hereinafter referred to as registration deviation) exceeds a prescribed allowable value, registration deviation correction processing is executed. In addition, the color image forming apparatus 10 forms a density detection pattern 700 (hereinafter referred to as a process control pattern) 700 on the intermediate transfer belt 30 at an even number of rotations of the intermediate transfer belt 30, and detects the density of the process control pattern 700. Then, based on the detected density, the density correction processing as in the first to fifth embodiments described above is executed as necessary.
[0188]
(Registered pattern and its position detection method)
Here, the resist pattern 600 formed on the intermediate transfer belt 30 in this embodiment will be described. As shown in FIG. 22A, the registration pattern 600 includes a rectangular pattern 600A that is long in the width direction of the intermediate transfer belt 30 (left and right in FIG. 22A) and the conveyance direction of the intermediate transfer belt 30 (FIG. 22). It is roughly divided into a rectangular pattern 600B that is long in the direction of arrow H in FIG.
[0189]
The pattern 600A and the pattern 600B are both a yellow pattern (hereinafter referred to as a Y regicon pattern), a magenta pattern (hereinafter referred to as a M regicon pattern), and a cyan pattern along the conveyance direction H of the intermediate transfer belt 30. (Hereinafter referred to as a C-resin pattern) and a black pattern (hereinafter referred to as a K-resin pattern). The black pattern is formed so as to be superimposed on the yellow toner image.
[0190]
Each of the register control patterns 601A, 601B, 601C, and 601D is sized to be included in a 15 mm × 15 mm process control pattern, and is formed by the same image forming units 20, 22, 24, and 26 as the process control pattern formation. Is done.
[0191]
The resist pattern 600 formed on the intermediate transfer belt 30 is irradiated with laser light from the infrared type LED 70, and the amount of reflected light is detected by the density detector 28. The detection signal is shown in FIG. On the right side of FIG. 23, the correspondence between the detection location of the concentration detector 28 and the detection signal is shown in time series.
[0192]
For example, when the position of the Y resister pattern 602 is detected by the density detector 28, the positions G1 and G2 where the magnitude of the detection signal Q1 exceeds a predetermined threshold value J are detected as the left and right boundary positions of the Y resister pattern 602. To do. Also for the Y register pattern 604, the points G3 and G4 where the magnitude of the detection signal Q1 exceeds a predetermined threshold value J are detected as the left and right boundary positions of the Y register pattern 604.
[0193]
Further, regarding the upper and lower boundary positions of the Y register pattern 602, the upper boundary position is determined when the magnitude of the detection signal Q1 at the predetermined position C near the central portion has changed from a state not exceeding the threshold value J to an exceeding state. The lower boundary position is detected when the magnitude of the detection signal Q1 at the predetermined position C has changed from a state where the threshold value J has been exceeded to a state where the threshold value J has not been exceeded.
[0194]
The position detection of the M register pattern 606, 608 and the C register pattern 610, 612 is the same as that of the Y register pattern 602, 604.
[0195]
The K regicon patterns 614 and 616 are formed so as to overlap the yellow toner image. For this reason, for example, when detecting the position of the K regicon pattern 614, the point G5 where the magnitude of the detection signal Q2 changes from a state where the predetermined threshold value J exceeds the predetermined threshold J (a surrounding yellow toner image region) to a state where it does not exceed. , G6 are detected as the left and right boundary positions of the K regicon pattern 614.
[0196]
As for the upper and lower boundary positions of the K regicon pattern 614, the magnitude of the detection signal Q2 at the predetermined position C near the center is changed from the state where the threshold value J has been exceeded (the surrounding yellow toner image region) to the state where it is not exceeded. The upper boundary position is detected when it changes, and the lower boundary position is detected when the magnitude of the detection signal Q2 at the predetermined position C changes from a state where it does not exceed the threshold value J to an excess state.
[0197]
By the way, the registration misalignment (registration pattern misalignment) detected in this embodiment includes (1) skew (inclination of the entire resister pattern), (2) magnification error in the main scanning direction, and (3) main scanning direction misalignment. There are four types of misalignment and (4) misalignment in the sub-scanning direction.
[0198]
Among these, (2) the magnification error in the main scanning direction is obtained from the length of the pattern 600A obtained from the left and right boundary positions of the pattern 600A of each color in FIG. (3) The positional deviation in the main scanning direction is obtained from the left and right boundary positions of the color pattern 600A and the specified left and right boundary positions.
[0199]
(4) The positional deviation in the sub-scanning direction is obtained from the left and right boundary positions of the color pattern 600B in FIG. 22A and the specified left and right boundary positions.
[0200]
(1) The skew is obtained from the difference between the upper boundary positions or the difference between the lower boundary positions of each color pattern 600A on both sides of the intermediate transfer belt 30 in the width direction. Alternatively, it may be obtained from the difference between the left boundary positions or the difference between the right boundary positions of the plurality of patterns 600 </ b> B separated in the conveyance direction of the intermediate transfer belt 30.
[0201]
(Register misalignment correction)
Here, an outline of various misregistration correction processing executed in the present embodiment will be described.
[0202]
(1) Skew correction
The skew is corrected by adjusting the angle of the mirror 20H of each image forming unit 20.
[0203]
(2) Correction of magnification error in the main scanning direction (magnification correction)
FIG. 34 shows an apparatus configuration relating to driving of an LD 668 as a light source. The source clock signal output from the frequency setting circuit 652 and the horizontal synchronization signal (SOS signal) output from the horizontal synchronization signal generation circuit 654 are input to the phase synchronization circuit 656.
[0204]
Here, the horizontal synchronization signal generation circuit 654 includes, for example, a one-shot multivibrator, and outputs a horizontal synchronization signal composed of pulses having a predetermined time width triggered by detection of horizontal synchronization. The phase synchronization circuit 656 adjusts the phase of the source clock signal to the phase of the horizontal synchronization signal and outputs a synchronization source clock signal delayed for a predetermined time from the trailing edge of the horizontal synchronization signal.
[0205]
The first timing control circuit 658 receives the horizontal synchronization signal and the synchronization source clock signal, and the first timing control circuit 658 is a predetermined first register in the control unit 650 constituted by a microcomputer or the like. A video clock having a phase setting based on the value set to 650A is output.
[0206]
The video clock is supplied to the second timing control circuit 660 and the image buffer memory 662. The second timing control circuit 660 uses a value set in a predetermined second register 650B in the control unit 650 as an enabling signal for allowing the image buffer memory 662 to read out the image signal from the input of the horizontal synchronizing signal. The output is delayed by the timing based on. By this permission signal, the writing line writing position on the photosensitive drum 20C is controlled.
[0207]
The image buffer memory 662 sequentially reads the stored image signals for one line one pixel at a time in synchronization with the video clock from the time when the permission signal is input, and supplies the image data to the screen generator 664 as image data.
[0208]
The screen generator 664 modulates the image data in synchronization with the video clock, and supplies an image signal obtained thereby to the laser driving circuit 666. As a result, the laser driving circuit 666 controls on / off of the LD 668 based on the image signal, and an electrostatic latent image is formed on the photosensitive drum 20C by the laser light from the LD 668.
[0209]
In the configuration as described above, the magnification correction in the main scanning direction of the image is performed based on the Y color printed first among the four colors of YMCK. That is, when the laser beam scans the photosensitive drum from the image writing position to the position where the image ends is called a print line, the print line of another color is based on the length L of the Y print line. The frequency of the video clock used for recording each color is adjusted so that the length of the video is matched with the length L.
[0210]
For example, the control unit 650 adjusts the frequency of the video clock by adjusting the frequency of the source clock signal output from the frequency setting circuit 652.
[0211]
(3) Correction of misalignment in the main scanning direction (main scanning direction correction)
The main scanning direction correction is performed by changing the count value of the video clock (set value of the first register 650A) from the horizontal synchronization signal detection position to the print line writing position and resetting the video clock phase.
[0212]
Specifically, by changing the value set in the second register 650B in the control unit 650, the timing at which the permission signal is output by the second timing control circuit 660 is changed, and printing on the photosensitive drum 20C is performed. Correct the line start position.
[0213]
Further, by changing the value set in the first register 650A in the control unit 650, the phase of the video clock is reset and the writing position of the print line is corrected.
[0214]
(4) Correction of displacement in the sub-scanning direction (sub-scanning direction correction)
In this embodiment, as a correction of the positional deviation in the sub-scanning direction, correction in units of one dot is performed by changing the number of clocks of the line sync signal, and correction for one dot or less is performed in the rotary polygon mirror drive motor control circuit for each color. This is done by changing the phase of the supplied reference clock. The line sync signal is an image writing timing signal for one line in the main scanning direction, and is output based on the SOS signal.
[0215]
The above four correction processes are executed in the order of magnification correction, main scanning direction correction, and sub-scanning direction correction as shown in FIG. 24A when skew correction is not performed. In the case of performing the skew correction, as shown in FIG. 24B, the skew correction is performed at the head, and thereafter, magnification correction, main scanning direction correction, and sub-scanning direction correction are executed in this order.
[0216]
( First reference Effect of form)
next, First reference As an operation of the embodiment, registration error correction and density correction processing will be described with reference to the flowchart of FIG. This process is executed under the control of the control unit 80 when the color image forming apparatus 10 is powered on and at a predetermined time interval. Of course, even when the installation environment of the color image forming apparatus 10 changes suddenly, it is desirable that the operator manually execute the density adjustment process. For example, the temperature changes by 3 degrees or more after the previous density adjustment process is executed. It is desirable to execute the density adjustment process when the humidity has changed or when the humidity has changed by 20% or more.
[0217]
In step 202 in FIG. 25, the conveyance rolls 32, 34, 36, and 38 are driven to start conveyance of the intermediate transfer belt 30 in the direction of arrow B in FIG. In the next step 204, it is determined whether or not it is an odd number of rotations from the start of conveyance of the intermediate transfer belt 30. Since the first cycle (first rotation) is an odd-numbered rotation, an affirmative determination is made in step 204 and the process proceeds to step 206 where the yellow image forming unit 20 applies a yellow regicon pattern along the width direction of the intermediate transfer belt 30. Form. As a result, a pair of yellow pattern portions in the regicon pattern shown in FIG. 22A is formed on the intermediate transfer belt 30. However, only one of the pair is shown in FIG. Note that the yellow pattern portion also includes a region serving as a base for the black regicon pattern.
[0218]
Thereafter, in steps 208 to 212, a magenta regicon pattern is formed by the magenta image forming unit 22, a cyan regicon pattern is formed by the cyan image forming unit 24, and a black regicon pattern is formed by the black image forming unit 26, respectively. 30 is formed. As a result, the regicon pattern shown in FIG. 22A is formed on the intermediate transfer belt 30.
[0219]
In the next step 214, the position of each of the resist pattern is detected by the density detector 28 in the manner described above. At this time, the skew is also detected by obtaining the positional deviation between the pair of resister patterns for each color.
[0220]
In the next step 216, it is determined whether or not the misregistration pattern misregistration (registration misalignment) exceeds a predetermined allowable value. Here, if the registration error does not exceed the allowable value, it can be determined that the correction of the registration error is not particularly necessary, and the process returns to step 204. On the other hand, if the registration error exceeds the allowable value, the process proceeds to step 218, and various registration error corrections (skew correction, magnification correction, main scanning direction correction, sub-scanning direction correction) as described above are executed.
[0221]
When the registration error detection and correction for the first rotation of the intermediate transfer belt 30 is completed as described above, the second rotation of the intermediate transfer belt 30 is entered. Since this is an even number of rotations, a negative determination is made in step 204 and the process proceeds to step 220 to execute the density adjustment processing described in the first to fifth embodiments. In this density adjustment processing, the density detection unit 28 used in the registration error detection is used.
[0222]
As the density adjustment processing here, any of the processing in FIGS. 10, 12, 15, and 19 may be adopted. However, it is not necessary to start conveyance of the intermediate transfer belt 30 at the beginning of each density adjustment process.
[0223]
As above, the book First reference In the registration misregistration correction and density correction processing of the form, registration misregistration detection / correction is executed on the odd-numbered circumference from the start of conveyance of the intermediate transfer belt 30, and the density detection / correction is performed using the same density detection unit 28 on the even-numbered circumference. Execute.
[0224]
As described above, the registration deviation detection / correction and the density detection / correction are executed by using the same density detection unit 28, so that an increase in the size of the color image forming apparatus 10 and an increase in apparatus cost can be avoided.
[0225]
Also, since registration error detection / correction is executed in the first cycle (the first cycle of the intermediate transfer member), after correcting the registration error in the first cycle, the next cycle (with the registration error corrected) The image density detection process can be executed in the second round of the intermediate transfer member. Accordingly, there is an advantage that it is possible to avoid the image density detection process being executed in a state where there is a registration error.
[0226]
[ Second reference Form]
next Second reference A form is demonstrated.
[0227]
Book Second reference As shown in FIG. 26, the color image forming apparatus 10 according to the embodiment forms a resister pattern and a process control pattern alternately on the intermediate transfer belt 30 with the resister pattern at the head, and each color is detected by the same density detector 28. And the density of the toner image of each color is detected.
[0228]
here, Second reference The registration error correction and density correction processing in the embodiment will be described with reference to the flowchart of FIG. In step 232 in FIG. 27, the transport rollers 32, 34, 36, and 38 are driven to start transport of the intermediate transfer belt 30 in the direction of arrow B in FIG. In the next step 234, a pair of yellow regicon patterns is formed along the width direction of the intermediate transfer belt 30 by the yellow image forming unit 20. Accordingly, a pair of yellow pattern portions in the regicon pattern shown in FIG. 26 is formed on the intermediate transfer belt 30. However, only one of the pair is shown in FIG. Note that the yellow pattern portion also includes a region serving as a base for the black regicon pattern. In the next step 236, the yellow image forming unit 20 forms a pair of yellow process control patterns 404 along the width direction of the intermediate transfer belt 30.
[0229]
Thereafter, in steps 238 to 248, a magenta pattern portion, a magenta procon pattern 408, a cyan pattern portion, a cyan procon pattern 412, a black pattern portion, and a black procon pattern 416 in the registration control pattern are each paired as an intermediate transfer belt. 30 is formed. As a result, the regicon pattern and the procon pattern shown in FIG. 26 are formed on the intermediate transfer belt 30.
[0230]
In the next step 250, the same density detection unit 28 sequentially executes position detection and density detection of each of the above-mentioned regicon patterns. At this time, the skew is also detected by obtaining the positional deviation between the pair of resister patterns for each color.
[0231]
In the next step 252, it is determined whether or not the misregistration pattern misregistration (registration misalignment) exceeds a predetermined allowable value. Here, if the registration error exceeds the allowable value, the process proceeds to step 254, and various registration error corrections (skew correction, magnification correction, main scanning direction correction, sub-scanning direction correction) as described above are executed. Then, after the registration deviation correction is completed, the process returns to step 234, and the registration control pattern and the process control pattern for each color are re-formed.
[0232]
On the other hand, if the registration error does not exceed the allowable value in step 252, the process proceeds to step 256 to determine whether or not density correction is required. If it is determined that density correction is required, density correction is performed in step 258 as in the first embodiment described above. After the density correction is completed, a process control pattern of each color of yellow, magenta, cyan, and black is formed in step 260, and density detection is performed again in the next step 262. Then, the process returns to step 256 to determine again whether or not density correction is required. Here, if the density correction is unnecessary, the registration error correction and the density correction process are ended.
[0233]
More than Second reference As in the embodiment, even when the regicon pattern and the procon pattern are alternately formed on the intermediate transfer belt 30, the same density detection unit 28 detects the displacement of the regicon pattern of each color and the density of the toner image of each color. With that First reference Similar to the configuration, an increase in the size and cost of the apparatus can be avoided. In addition, since the positional deviation of the resist pattern is detected before the toner image density in each color, the image density can be detected in a state where the image positional deviation is corrected.
[0234]
[ Third reference Form]
next , 3rd reference A form is demonstrated. this Third reference The form is effective in a case where it can be considered that there is no great difference in density between images formed using both end portions of the intermediate transfer belt 30 in the width direction.
[0235]
Book Third reference As shown in FIG. 28, the color image forming apparatus 10 according to the embodiment has a resister pattern near one end in the width direction of the intermediate transfer belt 30 and a process control pattern of each color near the other end. The registration error is detected by the common density detection unit 28A for the registration pattern, and the density is detected by the common density detection unit 28B for the process control pattern.
[0236]
here, Third reference The registration error correction and density correction processing in the embodiment will be described with reference to the flowcharts of FIGS. In step 272 of FIG. 29, the conveyance rolls 32, 34, 36, and 38 are driven to start conveyance of the intermediate transfer belt 30 in the direction of arrow B in FIG. In the next step 274, the yellow image forming unit 20 causes the yellow pattern portion of the registration control pattern to be near one end in the width direction of the intermediate transfer belt 30, and the yellow process control pattern 424 to be near the other end. Form in parallel.
[0237]
Thereafter, in step 276, the magenta pattern portion and the magenta proc pattern 428 of the regicon pattern, the cyan pattern portion and the cyan proc pattern 432 in step 278, and the black pattern portion and the black proc pattern 436 in step 280, respectively. Each is formed on the intermediate transfer belt 30. As a result, the resist pattern and the process pattern shown in FIG. 28 are formed on the intermediate transfer belt 30.
[0238]
In the next step 282, the registration deviation is detected by the common density detection unit 28A for the registration pattern, and the density is detected by the common density detection unit 28B for the process control pattern.
[0239]
In the next step 284, it is determined whether or not the misregistration pattern misregistration (registration misalignment) exceeds a predetermined allowable value. Here, if the registration error exceeds the allowable value, the process proceeds to step 286, and magnification correction, main scanning direction correction, and sub-scanning direction correction among the above-described registration error correction are executed. Then, after the registration deviation correction is completed, the process returns to step 274, and the registration control pattern and the process control pattern for each color are re-formed.
[0240]
On the other hand, if the registration error does not exceed the allowable value in step 284, the process proceeds to step 288, and the density pattern is detected. If the density pattern cannot be detected normally due to a large skew (see FIG. 35 for details such as two colors other than black overlapping or black cannot be detected because they do not overlap), go to step 298. Then, the subroutine of the skew correction process shown in FIG. 30 is executed.
[0241]
On the other hand, if the density pattern has been detected normally in step 288, the process proceeds to step 290 to determine whether or not density correction is required. If it is determined that density correction is required, density correction is performed in step 292 as in the first embodiment. After the density correction is completed, a yellow, magenta, cyan, and black color process control pattern is formed in step 294, and density detection is performed again in the next step 296. Then, the process returns to step 290 to determine again whether density correction is required. If density correction is unnecessary, the process proceeds to step 298 to execute a subroutine of skew correction processing in FIG.
[0242]
In step 302 in FIG. 30, the yellow image forming unit 20 forms yellow pattern portions of the regicon pattern in the vicinity of both ends in the width direction of the intermediate transfer belt 30. Thereafter, in steps 304 to 308, a pair of magenta pattern portion, cyan pattern portion, and black pattern portion is formed on the intermediate transfer belt 30. In the next step 310, the skew is detected by obtaining the positional deviation between the resister patterns for each color.
[0243]
In the next step 312, it is determined whether or not the detected skew exceeds a predetermined allowable value. If the skew exceeds the allowable value, the process proceeds to step 314, and the angle of the mirror of the image forming unit of the color that has caused the skew as described above (for example, the mirror 20H in the case of the yellow image forming unit 20). The skew correction is performed by adjusting. After the skew correction is completed, the process returns to step 302.
In this way, the processing is continued until the skew is within the allowable value. When the skew is within the allowable value, the process returns from the subroutine of FIG. 30, and proceeds to step 299 of FIG. , Main scanning direction correction and sub-scanning direction correction). The correction process is illustrated in FIG. 24B as a case with skew. This completes the registration error correction and density correction processing of FIG.
[0244]
More than Third reference As in the embodiment, when the registration control pattern and the process control pattern are formed on the intermediate transfer belt 30 in parallel and the registration shift detection and the density detection are executed in parallel, the registration control pattern and the process control pattern are sequentially formed. The registration error correction and density correction processing can be completed faster than when registration error detection and density detection are sequentially executed. That is, it is possible to improve the efficiency of the registration error correction and the density correction processing.
[0245]
Further, since the registration deviation is detected by the common density detection unit 28A for the registration control pattern and the density is detected by the common density detection unit 28B for the process control pattern, two density detection units are sufficient, and the large size of the apparatus And cost increase can be avoided.
[0246]
The positional deviation of the registration control pattern and the density of the toner image may be detected by separate sensors 28A and 28B as shown in FIG. 28, or a single line whose detection target is the entire width direction of the intermediate transfer member. You may detect with a sensor.
[0247]
[ 4th reference Form]
next , 4th reference A form is demonstrated. this 4th reference The configuration is effective in a case where it can be considered that there is no significant difference between the density of an image formed using both ends of the intermediate transfer belt 30 in the width direction and the density of an image formed using the center. is there.
[0248]
Book 4th reference As shown in FIG. 31, the color image forming apparatus 10 of the embodiment has a resister pattern near both ends in the width direction of the intermediate transfer belt 30 (left and right in FIG. 31), and a pair of procon patterns for each color near the center. The resist pattern is detected by the common density detectors 28A and 28D, and the resist pattern is detected by the common density detectors 28B and 28C.
[0249]
here, 4th reference The registration error correction and density correction processing in the embodiment will be described with reference to the flowchart of FIG. In step 322 in FIG. 32, the conveyance rolls 32, 34, 36, and 38 are driven to start conveyance of the intermediate transfer belt 30 in the direction of arrow B in FIG. In the next step 324, the yellow image forming unit 20 causes the yellow pattern portion of the regicon pattern near the both ends in the width direction of the intermediate transfer belt 30 and the yellow procon patterns 444 and 446 near the center simultaneously. Form with.
[0250]
Thereafter, in steps 326 to 330, a resister pattern and a process control pattern are formed on the intermediate transfer belt 30 for each of magenta, cyan, and black.
[0251]
In the next step 332, the registration deviation is detected by the common density detectors 28A and 28D for the resist pattern, and the density is detected by the common density detectors 28B and 28C for the process control pattern.
[0252]
In the next step 334, it is determined whether or not the displacement of the registration control pattern (registration displacement) exceeds a predetermined allowable value. Here, if the registration error exceeds the allowable value, the process proceeds to step 336, and various registration error corrections (skew correction, magnification correction, main scanning direction correction, sub-scanning direction correction) as described above are executed. Then, after the registration error correction is completed, the process returns to step 324, and the registration control pattern and the process control pattern for each color are re-formed.
[0253]
On the other hand, if the registration error does not exceed the allowable value in step 334, the process proceeds to step 338, where it is determined whether density correction is required. If it is determined that density correction is required, density correction is performed in step 340 as in the first embodiment. After completing the density correction, in step 342, a yellow, magenta, cyan, and black color process pattern is formed, and in the next step 344, density detection is performed again. Then, the process returns to step 338 to determine again whether or not density correction is required. If density correction is unnecessary, the registration error correction and density correction processing ends.
[0254]
More than 4th reference As in the embodiment, when the regicon pattern and the procon pattern are simultaneously formed on the intermediate transfer belt 30, and the registration shift detection and the density detection are simultaneously performed, the regicon pattern and the procon pattern are sequentially formed. The registration error correction and density correction processing can be completed more quickly than when registration error detection and density detection are sequentially executed. That is, it is possible to improve the efficiency of the registration error correction and the density correction processing.
[0255]
In addition, since the misregistration pattern of each color and the density of the toner image of each color are detected at two locations for each color, the misregistration detection result and image density with little variation and error are obtained by averaging the detection results. A detection result can be obtained. In addition, the skew can be detected based on the detection result of the misregistration pattern detected at two locations.
[0256]
In addition, since the registration deviation is detected by the common density detectors 28A and 28D for the resist pattern, and the density is detected by the common density detectors 28B and 28C for the pro-con pattern, a maximum of four density detectors is sufficient. It is.
[0257]
The registration pattern displacement and toner image density may be detected by a total of four sensors 28A, 28B, 28C, and 28D as shown in FIG. 31, or the entire width direction of the intermediate transfer belt 30 is detected. You may detect by one line sensor made into object. Alternatively, detection may be performed by a total of two line sensors: a line sensor whose detection target is one side from the central portion in the width direction of the intermediate transfer belt 30 and a line sensor whose detection target is the other side.
[0258]
Incidentally, as an example of the resist pattern and the process control pattern formed on the intermediate transfer belt 30, an example shown in FIG. In the example of FIG. 33, in the first row R1, yellow registration control patterns (= registration control patterns including a yellow pattern portion long in the conveyance direction of the belt 30) 502 and 506, and magenta registration control patterns (= belt 30 of the belt 30). (Registered pattern including magenta pattern portions long in the transport direction) 504 and 508.
[0259]
The second row R2 includes cyan registration control patterns (= registration pattern including a cyan pattern portion that is long in the conveyance direction of the belt 30) 510 and 514 and black registration control patterns (= black black that is long in the conveyance direction of the belt 30). (Register pattern including pattern portion) 512 and 516 are formed.
[0260]
In the third row R3, a yellow toner image 518, a magenta toner image 520, a cyan toner image 522, and a black toner image 524 are formed.
[0261]
In such a regicon pattern and a procon pattern, with respect to three of the regicon patterns 502 and 510 and the procon pattern 518 arranged along the conveyance direction of the belt 30, the density detector 28A causes the misregistration of the regicon pattern and the procon pattern. The concentration is detected. Similarly, with respect to three of the registration control patterns 504 and 512 and the process control pattern 520 arranged along the conveyance direction of the belt 30, the density detection unit 28B detects the displacement of the registration control pattern and the density of the process control pattern.
[0262]
Similarly, the resister pattern 506, 514 and the procon pattern 522 are detected by the density detector 28C, and the resister pattern 508, 516 and the procon pattern 524 are detected by the density detector 28D. The concentration of the procon pattern is detected.
[0263]
With respect to the resister pattern and the process control pattern arranged as shown in FIG. 33 as described above, the detection of misalignment and the detection of the density are performed on the resister pattern and the process control pattern in three rows along the conveyance direction of the belt 30. It ’s fine. For this reason, the sixth to the above-mentioned 4th reference The time required for the detection process can be shortened as compared to the case where the positional deviation and the density are detected for at least four columns of the resist control pattern and the process control pattern as in the embodiment.
[0264]
In the above description, the intermediate transfer belt is used as the intermediate transfer member. However, other image carriers such as a photosensitive drum may be used.
[0265]
In the above, the square density patch is formed on the intermediate transfer belt as the process control pattern. However, the density patch may have another shape such as a circle, an ellipse, or a rectangle, and the size thereof is also particularly limited. It is not a thing.
[0266]
Similarly, the shape and size of the regi-con pattern can be set to an arbitrary shape and size, and is not particularly limited.
[0267]
【The invention's effect】
As explained above, the first and the second 4 According to the invention, the black image forming unit is disposed downstream of the color image forming unit in the conveyance direction of the intermediate transfer member, and the color toner image forming unit reaches the black image forming unit earlier than the conventional one. After the color toner image is formed on the intermediate transfer member, a black toner image can be formed earlier than before, and the processing relating to the density detection of the black toner image can be executed efficiently.
[0268]
Second, second 5 According to the invention, the black image forming portion is arranged downstream of the color image forming portion in the transport direction of the intermediate transfer member, and immediately after the formation of a plurality of color toner images (the intermediate transfer member is at least circulated). Since a black toner image can be formed on a part of one color toner image (before being transported halfway through the path), the time required for forming the color toner image and the black toner image can be shorter than before. Therefore, it is possible to efficiently execute the processing relating to the density detection of the black toner image.
[0269]
The third and third 6 According to the invention, a plurality of sets of color toner images having different densities are formed on the intermediate transfer body, and at least one of the plurality of sets of color toner images has a density detection value of the other color toner image having a predetermined suitability. Since there is a high possibility that the density is within the density range, it is confirmed with high probability that the density of one color toner image is appropriate, and the density of the black toner image can be quickly detected. Concentration detection can be executed efficiently.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram of a color image forming apparatus.
FIG. 2 is a configuration diagram of a concentration detection unit.
3A is a graph showing spectral characteristics in a visible region of a yellow toner image, and FIG. 3B is a graph showing spectral characteristics in an infrared region of a yellow toner image.
4A is a graph showing spectral characteristics in a visible region of a magenta toner image, and FIG. 4B is a graph showing spectral characteristics in an infrared region of a magenta toner image.
5A is a graph showing spectral characteristics in a visible region of a cyan toner image, and FIG. 5B is a graph showing spectral characteristics in an infrared region of a cyan toner image.
6A is a graph showing spectral characteristics in a visible region of a black toner image, and FIG. 6B is a graph showing spectral characteristics in an infrared region of a black toner image.
FIG. 7 is a diagram for explaining density detection of a color density patch and a black density patch.
FIG. 8 is a flowchart showing a basic processing procedure of a color image forming process.
FIG. 9A is a schematic configuration diagram of an image forming unit in the first embodiment, and FIG. 9B is formed on an intermediate transfer belt when the density of a color density patch as a base is appropriate. FIG. 10C is a diagram illustrating density patches formed on the intermediate transfer belt when the density of the color density patch serving as the background is not appropriate.
FIG. 10 is a flowchart showing a processing routine of black image density adjustment processing in the first embodiment;
FIG. 11A is a schematic configuration diagram of an image forming unit in the second embodiment, and FIG. 11B is formed on an intermediate transfer belt when the density of a color density patch serving as a base is appropriate. FIG. 10C is a diagram illustrating density patches formed on the intermediate transfer belt when the density of the color density patch serving as the background is not appropriate.
FIG. 12 is a flowchart showing a processing routine of black image density adjustment processing in the second embodiment.
13A is a schematic configuration diagram of an image forming unit in the third embodiment, and FIG. 13B is formed on an intermediate transfer belt when the density of a color density patch serving as a base is appropriate. FIG. 10C is a diagram illustrating density patches formed on the intermediate transfer belt when the density of the color density patch serving as the background is not appropriate.
FIG. 14 is a time chart showing timings at which various density patches are formed in the third embodiment.
FIG. 15 is a flowchart showing a processing routine of black image density adjustment processing in the third and fourth embodiments.
16A is a schematic configuration diagram of an image forming unit according to the fourth embodiment, and FIG. 16B is formed on an intermediate transfer belt when the density of a color density patch serving as a base is appropriate. FIG. 10C is a diagram illustrating density patches formed on the intermediate transfer belt when the density of the color density patch serving as the background is not appropriate.
FIG. 17 is a time chart showing timings at which various density patches are formed in the fourth embodiment.
FIG. 18A is a schematic configuration diagram of an image forming unit according to a fifth embodiment, and FIG. 18B is formed on an intermediate transfer belt when the density of a color density patch serving as a base is appropriate. FIG. 10C is a diagram illustrating density patches formed on the intermediate transfer belt when the density of the color density patch serving as the background is not appropriate.
FIG. 19 is a flowchart showing a processing routine of black image density adjustment processing in the fifth embodiment.
FIGS. 20A and 20B are diagrams showing various examples in which a black density patch is formed on a base color density patch, and FIG. 20A shows an example in which a black density patch is formed so as to be included in a color density patch. (B) is a figure which shows the example which forms so that a part of black density patch may protrude from a color density patch, respectively.
FIG. 21 First reference It is a perspective view which shows the resiston pattern and the process control pattern which are formed with a form.
FIG. 22A is a diagram showing a regicon pattern formed at odd-numbered rotations, and FIG. 22B is a diagram showing a process control pattern formed at even-numbered rotations.
FIG. 23 is a diagram for explaining a position detection method using a resiston pattern.
24A is a diagram showing an outline of misalignment correction when it is assumed that there is no skew, and FIG. 24B is a diagram showing an outline of misalignment correction including skew correction.
FIG. 25 First reference 6 is a flowchart showing a control routine of registration deviation correction and density correction processing in the embodiment.
FIG. 26 Second reference It is a top view which shows the resiston pattern and the process control pattern which are formed with a form.
FIG. 27 Second reference 6 is a flowchart showing a control routine of registration deviation correction and density correction processing in the embodiment.
FIG. 28 Third reference It is a top view which shows the resiston pattern and the process control pattern which are formed with a form.
FIG. 29 Third reference 6 is a flowchart showing a control routine of registration deviation correction and density correction processing in the embodiment.
FIG. 30 is a flowchart showing a subroutine of skew correction processing.
FIG. 31 4th reference It is a top view which shows the resiston pattern and the process control pattern which are formed with a form.
FIG. 32 4th reference 3 is a flowchart showing a control routine of registration deviation correction and density correction processing in the embodiment.
FIG. 33 4th reference It is a top view which shows the register control pattern and the process control pattern in the modification of form.
FIG. 34 is a block diagram showing a configuration of an apparatus related to magnification correction and position shift correction in the main scanning direction.
FIG. 35 is a diagram illustrating a case where a density pattern cannot be normally detected because a skew remains after performing magnification correction, main scanning direction correction, and sub-scanning direction correction.
[Explanation of symbols]
10 Color image forming apparatus
18 Image forming unit
20 Yellow image forming section
22 Magenta image forming section
24 Cyan image forming unit
26 Black image forming section
28 Concentration detector
30 Intermediate transfer belt
80 Control unit

Claims (14)

A color toner image is formed by a color image forming unit on an intermediate transfer member that is transported in a predetermined transport direction along a predetermined circulation path, and a black image disposed downstream of the color image forming unit in the transport direction A black image density detecting method for detecting a density of the black toner image in a color image forming apparatus that forms a color image on the intermediate transfer member by forming a black toner image on the color toner image by forming a black toner image. There,
Forming a color toner image on the intermediate transfer member by the color image forming unit;
Detect the density of the formed color toner image,
When the density detection value of the color toner image is within a predetermined appropriate density range, the black image forming unit forms a black toner image on a part of the color toner image on the intermediate transfer member,
Detecting the density of the formed black toner image;
Black image density detection method. If the density detection value of the color toner image is not within a predetermined appropriate density range, the color image forming unit is adjusted so that the density of the formed color toner image is within the predetermined appropriate density range;
A color toner image is formed on the intermediate transfer member by the adjusted color image forming unit,
Detect again the density of the formed color toner image,
The black image density detection method according to claim 1. A color toner image is formed by a color image forming unit on an intermediate transfer member that is transported in a predetermined transport direction along a predetermined circulation path, and a black image disposed downstream of the color image forming unit in the transport direction A black image density detecting method for detecting a density of the black toner image in a color image forming apparatus that forms a color image on the intermediate transfer member by forming a black toner image on the color toner image by forming a black toner image. There,
A plurality of color toner images are formed on the intermediate transfer member by the color image forming unit;
A black toner image is formed on a part of one color toner image among the plurality of formed color toner images by the black image forming unit,
Detecting the density of any one of the plurality of color toner images;
Detecting the density of the black toner image when the density detection value of the color toner image is within a predetermined appropriate density range;
Black image density detection method. If the density detection value of the color toner image is not within a predetermined appropriate density range, the color image forming unit is adjusted so that the density of the formed color toner image is within the predetermined appropriate density range;
A plurality of color toner images are formed on the intermediate transfer member by the adjusted color image forming unit,
A black toner image is formed on a part of one color toner image among the plurality of formed color toner images by the black image forming unit,
Detecting again the density of any one of the plurality of color toner images;
The black image density detection method according to claim 3. A color toner image is formed by a color image forming unit on an intermediate transfer member that is transported in a predetermined transport direction along a predetermined circulation path, and a black image disposed downstream of the color image forming unit in the transport direction A black image density detecting method for detecting a density of the black toner image in a color image forming apparatus that forms a color image on the intermediate transfer member by forming a black toner image on the color toner image by forming a black toner image. There,
A plurality of sets of two color toner images having the same density are formed on the intermediate transfer member by the color image forming unit so that the density of each set is different.
A black toner image is formed by superimposing a part of one color toner image of each set of formed color toner images by the black image forming unit,
Detect the density of the other color toner image in each set of color toner images,
When the density detection value of the other color toner image is within a predetermined appropriate density range, the density of the black toner image formed on a part of one color toner image of the same set is detected.
Black image density detection method. An intermediate transfer member transported in a predetermined transport direction along a predetermined circulation path ;
A color toner image forming unit that includes a photoconductor, forms a color toner image on the photoconductor, and forms the color toner image on the intermediate transfer body by transferring the formed color toner image to the intermediate transfer body;
Disposed on the downstream side in the transport direction with respect to the color toner image forming means, provided with a photoconductor, forming a black toner image on the photoconductor, and transferring the formed black toner image to the intermediate transfer member, thereby A black toner image forming means for forming a black toner image on the transfer member;
A density detecting unit that is disposed in the vicinity of the circulation path and detects the density of a color toner image and a black toner image formed on the intermediate transfer member;
Determination means for determining whether or not the density detection value of the color toner image detected by the density detection means is within a predetermined appropriate density range;
When the determination unit determines that the density detection value of the color toner image is within a predetermined appropriate density range, the black toner image forming unit forms a black toner image on a part of the color toner image; First control means for controlling the density of the formed black toner image to be detected by the density detection means;
A color image forming apparatus. The first control unit determines that the density of the color toner image falls within the predetermined appropriate density range when the determination unit determines that the detected density value of the color toner image is not within the predetermined appropriate density range. The color toner image forming unit is adjusted as described above, the color toner image is formed again on the intermediate transfer member by the adjusted color toner image forming unit, and the density of the formed color toner image is detected again by the density detecting unit. 7. The color image forming apparatus according to claim 6, wherein control is performed so that the determination means again determines whether or not the detected density detection value is within a predetermined appropriate density range. 8. The density detecting unit according to claim 6, wherein the density detecting unit is disposed in the vicinity of the downstream side in the transport direction with respect to each of the black toner image forming unit and the color toner image forming unit. Color image forming apparatus. An intermediate transfer member transported in a predetermined transport direction along a predetermined circulation path ;
A color toner image having a photoconductor, forming a plurality of color toner images on the photoconductor, and transferring the formed color toner images to the intermediate transfer member to form a plurality of color toner images on the intermediate transfer member Forming means;
It is disposed downstream of the color toner image forming means in the conveying direction, and includes a photoconductor, and forms a black toner image on the photoconductor, and the formed black toner image is transferred to the intermediate transfer body by the color toner image forming means. A black toner image forming means for forming a black toner image on the intermediate transfer member by transferring the color toner image over a part of one of the plurality of color toner images formed thereon;
A density detecting unit that is disposed in the vicinity of the circulation path and detects the density of a color toner image and a black toner image formed on the intermediate transfer member;
Determination means for determining whether or not the density detection value of the color toner image detected by the density detection means is within a predetermined appropriate density range;
When the determination unit determines that the density detection value of the color toner image is within a predetermined appropriate density range, the density detection unit detects the density of the black toner image formed by the black toner image formation unit. Second control means for controlling to do,
A color image forming apparatus. The second control means has the density of the color toner image within the predetermined appropriate density range when the determination means determines that the detected density value of the color toner image is not within the predetermined appropriate density range. Adjust the color toner image forming means so that adjusted A plurality of color toner images are formed again on the intermediate transfer member by the color toner image forming unit, and a black toner image is formed on a part of one color toner image by the black toner image forming unit. Is formed again, the density of any other color toner image is detected again by the density detecting means, and it is judged again by the judging means whether or not the detected density detection value is within the predetermined appropriate density range. The color image forming apparatus according to claim 9, wherein the color image forming apparatus is controlled as follows. 11. The color image forming apparatus according to claim 9, wherein the density detecting unit is configured by a single sensor disposed on the downstream side in the transport direction with respect to the black toner image forming unit. . The density detection unit includes a plurality of sensors arranged for each color of the color toner image formed on the intermediate transfer member by the color toner image forming unit on the downstream side in the transport direction with respect to the black toner image forming unit. The color image forming apparatus according to claim 9, wherein the color image forming apparatus is configured. The color toner image forming means includes a yellow image forming unit that forms a yellow toner image, a magenta image forming unit that forms a magenta toner image, and a cyan image forming unit that forms a cyan toner image. 13. The color image forming apparatus according to claim 12, wherein the yellow image forming unit is disposed closest to the black toner image forming unit . An intermediate transfer member transported in a predetermined transport direction along a predetermined circulation path;
A plurality of sets of color toner images having the same density are formed on the photoconductor so that each set has a different density, and the formed color toner images are transferred to the intermediate transfer body; Color toner image forming means for forming a plurality of sets of color toner images on the intermediate transfer member;
It is disposed downstream of the color toner image forming unit in the transport direction, and includes a photoconductor, and forms a black toner image on the photoconductor, and the formed black toner image is transferred to the intermediate transfer member by the color toner image forming unit. A black toner image forming means for forming a black toner image on the intermediate transfer member by transferring a black toner image on a part of one color toner image of each set of color toner images formed thereon;
A density detection means for detecting the density of the other color toner image and the black toner image of each set of color toner images disposed on the intermediate transfer member and disposed in the vicinity of the circulation path;
Determination means for determining whether the density detection value of the other color toner image detected by the density detection means is within a predetermined appropriate density range;
When the determination unit determines that the density detection value of the other color toner image is within a predetermined appropriate density range, the density of the black toner image formed on one color toner image of the same set is Third control means for controlling the detection by the density detection means;
A color image forming apparatus.

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