JP2008139516A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of preventing cleaning defects, thereby extending the service life of a cleaning device, as well as, forming high-quality images. <P>SOLUTION: The image forming apparatus is equipped with a first image carrier 1, held turnably and carrying a recorded image to be formed; a second image carrier 2 held turnably, while carrying the recorded image to be transferred from the first image carrier 1; a reference pattern for adjusting image density 3, formed successively, at a position which is different from a position where the recorded image is formed previous time in the main scanning direction and transferred from the first image carrier 1 onto the second image carrier 2; an image density detection means 4 for detecting the optical density of the reference pattern 3 on the second image carrier 2; and an image density adjusting means 5 for adjusting the image density of the recorded image that is formed, based on the result of the detection by the image density detection means 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an image forming apparatus. Specifically, a copying machine, a facsimile machine, a printer, or a combination of these, which forms a toner recording image by a process such as an electrostatic recording method or an electrophotographic method in which a recorded image is formed by adjusting the image density with a reference pattern to be created The present invention relates to an image forming apparatus.

In an image forming apparatus using an electrophotographic method in a conventional image forming apparatus, a reference pattern is created on an image carrier under predetermined image forming conditions in order to stabilize image density. The predetermined image forming conditions are conditions such as a toner density of the developer, a potential on the image carrier and a bias applied to the developing sleeve.
Then, the image density is detected by an optical image density sensor of the image density detecting means, and this is fed back to the image forming conditions and developer density to stabilize the image density. Usually, the optical image density sensor is fixed at a predetermined position with respect to the longitudinal direction of the image forming apparatus, and the reference pattern is created at a position corresponding to the optical image density sensor.
When a repeated image forming operation is performed, a reference pattern is created between the transfer paper of the recording medium and the transfer paper, and the image density of the reference pattern is detected by the optical image density sensor. . The image density is controlled to be constant by feeding back the image forming conditions and the developer density according to the magnitude of the detected value.
Since this reference pattern passes through the transfer nip without the recording paper of the recording medium in the transfer portion, a part of the toner in the reference pattern portion is collected as it is in the cleaning portion on the image carrier. Become. In addition, the other part is transferred to the intermediate transfer belt of the intermediate transfer member and the transfer conveyance belt of the recording medium conveyance unit, and is collected by the cleaning unit facing the intermediate transfer belt and the transfer conveyance belt.
The amount of toner per unit area of the reference pattern portion collected by the cleaning portion is about 5 to 20 times that in the normal image forming operation, which is a heavy load on the cleaning unit.

FIG. 16 is a diagram showing a state of an edge portion of a reference pattern 1003 for image density adjustment created in a conventional image forming apparatus.
In addition, as shown in FIG. 16, the edge portion of the reference pattern 1003 adheres more strongly to the image carrier than the inner side of the reference pattern 1003 due to a higher potential due to the edge effect, and is thus cleaned. It is difficult to do.
FIG. 17 is a diagram showing the creation position of the reference pattern 1003 for adjusting the image density in the conventional image forming apparatus.
Normally, in a conventional image forming apparatus having a plurality of photoconductors, as shown in FIG. 17, the creation position of the reference pattern 1003 is fixed for each photoconductor, and the transfer residue of the reference pattern 1003 is input at a predetermined position every time. Has been. For example, K (black) toner is input at position P1, Y (yellow) toner is input at position P2, C (cyan) toner is input at position P3, and M (magenta) toner is input at position P4 every time. Has been.
When the reference pattern 1003 is formed at the same position in the main scanning direction indicated by the arrow (G) in the figure, toner that is difficult to clean is input to the edge portion of the reference pattern 1003 for each number of image formations. . Then, when the wear of the cleaning blade corresponding to the edge portion is accelerated and exceeds the limit, the toner slips through, resulting in poor cleaning.

Furthermore, in recent years, in order to cope with the improvement in quality of an image to be formed, a toner having a particle size smaller than that of a conventional toner such as a small particle size polymerized toner has been used. Such toners have a lower cleaning margin than conventional pulverized toners having a relatively large number of corners, and have a characteristic of easily passing through a cleaning blade, and it is difficult to ensure cleaning properties by conventional methods. ing. Conventional methods include improvements to the cleaning blade material, contact conditions, toner external additives, and the like.
As a conventional technique, it has been proposed that detection means for detecting development density can be moved to an arbitrary position in the main scanning direction to perform image density detection (see Patent Document 1). However, the creation position of this reference pattern is determined based on the detection value of the detection means. Then, detection may be performed at the same position in the main scanning direction.
Therefore, since the edge of the reference pattern is continuously input as described above, the wear of the cleaning blade is promoted, the replacement cycle is accelerated, and it is difficult to cope with high image quality.
Further, the density detection pattern data can be increased by increasing the density detection pattern on each image carrier and transferring the density detection pattern to the transfer transfer body at a plurality of positions different in the main scanning direction. It has been proposed (see Patent Document 2). However, the density detection pattern may be formed and transferred at the same position in the main scanning direction.
Therefore, as described above, since the edges of the density detection pattern are continuously input, cleaning failure occurs, the cleaning blade is accelerated, the replacement cycle is accelerated, and it is difficult to cope with high image quality. .
JP-A-8-262862 JP 2002-91114 A

In the conventional image forming apparatus, there has been a problem that a cleaning failure occurs, the wear of the cleaning blade is accelerated, the replacement cycle is accelerated, and it is difficult to cope with high image quality.
Therefore, an object of the present invention is to solve such problems. That is, an object of the present invention is to provide an image forming apparatus that forms a high-quality image in addition to preventing a cleaning failure and extending the life of the cleaning device.

In order to achieve the above object, the present invention described in claim 1 is a recording formed by being rotatably held in an image forming apparatus that forms a recorded image by adjusting an image density with a reference pattern to be created. A first image carrier that carries an image; a second image carrier that carries a recorded image transferred from the first image carrier and is rotatably held; and the second image carrier. An image density adjustment reference pattern which is sequentially formed and transferred from the first image carrier to a position different from the previously created position in the main scanning direction of the recorded image on the body; and the second image Image forming apparatus comprising: image density detecting means for detecting the optical density of the reference pattern on the carrier; and image density adjusting means for adjusting the image density of a recorded image formed based on the detection result of the image density detecting means. It is characterized by being.
According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the image forming apparatus includes a plurality of image forming units each including the first image carrier.
According to a third aspect of the present invention, in the image forming apparatus according to the second aspect, the image forming section is an image forming apparatus including a black image forming section and a plurality of color image forming sections. To do.

According to a fourth aspect of the present invention, in the image forming apparatus according to the first, second, or third aspect, the second image carrier is an image forming apparatus including an intermediate transfer member.
According to a fifth aspect of the present invention, in the image forming apparatus according to the first, second, or third aspect, the second image carrier is an image forming apparatus that also serves as a recording medium conveying unit. Features.
According to a sixth aspect of the present invention, in the image forming apparatus according to any one of the first to fifth aspects, the reference pattern is an image forming apparatus including a color toner.
According to a seventh aspect of the present invention, in the image forming apparatus according to any one of the first to sixth aspects, the reference pattern is formed and transferred at a position away from a previously created position by a predetermined distance. An image forming apparatus is provided.
According to an eighth aspect of the present invention, in the image forming apparatus according to any one of the first to seventh aspects, the reference pattern has a predetermined length in a main scanning direction of the reference pattern from a previously created position. It is an image forming apparatus which is formed and transferred at a position far away from the image forming apparatus.

According to a ninth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the reference pattern is formed and transferred at a position where the optical density of the image density detecting means is next. An image forming apparatus comprising: forming and transferring the next reference pattern at a position on the other end side of the optical density detectable range of the image density detecting means when the outside of the detection range is reached. To do.
According to a tenth aspect of the present invention, in the image forming apparatus according to any one of the first to eighth aspects, the position where the reference pattern is formed and transferred next is an optical density of the image density detecting means. The image forming apparatus is characterized in that when it reaches the outside of the detection range, the next reference pattern is formed and transferred at a position separated by a predetermined distance in the folding direction.
According to an eleventh aspect of the present invention, in the image forming apparatus according to any one of the first to tenth aspects, the image density detecting unit is an image forming apparatus including a plurality of image density sensors. Features.

According to a twelfth aspect of the present invention, in the image forming apparatus according to any one of the first to eleventh aspects, the image density detecting unit includes a plurality of image density sensors for black and color toner. It is an image forming apparatus.
According to a thirteenth aspect of the present invention, in the image forming apparatus according to any one of the first to twelfth aspects, the image density detection unit moves along a surface of the second image carrier. The image forming apparatus includes an image density detecting unit moving unit.
According to a fourteenth aspect of the present invention, in the image forming apparatus according to any one of the first to thirteenth aspects, the average particle diameter of the toner is 6 μm or less.
According to a fifteenth aspect of the present invention, in the image forming apparatus according to any one of the first to fourteenth aspects, the toner has an image formation having a shape factor (SF-1) representing a degree of sphericalness of 150 or less. It is a device.

  According to the present invention, it is possible to provide an image forming apparatus that forms a high quality image in addition to preventing cleaning failure and extending the life of the cleaning device.

Embodiments of the present invention will be described below in detail with reference to the drawings.
FIG. 1 is a basic configuration diagram of a first example of an image forming apparatus 100 according to an embodiment of the present invention.
FIG. 2 is a diagram showing the creation position of the reference pattern 3 for image density adjustment in the first example of the image forming apparatus 100 according to the embodiment of the present invention.
1 and 2, in an image forming apparatus 100 that forms a recorded image by adjusting an image density with a reference pattern to be created, a first image carrier that carries a recorded image that is rotatably held. 1, a second image carrier 2 that carries a recorded image transferred from the first image carrier 1 and is rotatably held, and a first image carrier on the second image carrier 2 A reference pattern 3 for image density adjustment which is sequentially formed and transferred from the body 1 to a position different from the position previously created in the main scanning direction of the recorded image, and a reference pattern 3 on the second image carrier 2 The image density detecting means 4 for detecting the optical density of the image and the image density adjusting means 5 for adjusting the image density of the recorded image formed based on the detection result of the image density detecting means 4 are provided.

The image forming apparatus 100 has a drum shape that rotates in the clockwise direction indicated by an arrow (A) in the image forming unit 10 at a position facing the second image carrier 2 that also serves as the recording medium conveying unit 21. A first image carrier 1 that is a photosensitive drum is disposed. Around the first image carrier 1, a charging device 101, an exposure device 102, a developing device 103, a transfer device 104, and a cleaning device 105 are arranged in this order. By these devices, the first image carrier 1 is charged, exposed, developed, transferred, and cleaned. By performing these steps, a toner image is formed on the transfer sheet of the recording medium (P) conveyed onto the second image carrier 2 also serving as the recording medium conveying means 21 of the direct transfer system. Is done.
The developing device 103 is filled with a developer, and a toner image is formed on the first image carrier 1. Further, the developing device 103 includes a toner replenishing device 130 for replenishing toner into the developing device 103. The recording medium (P) on which the toner image is formed is transferred to the fixing device 106 by the second image carrier 2 that also serves as the recording medium conveying means 21 that moves counterclockwise in the direction of the arrow (B) shown in the figure. The conveyed toner image is fixed.

The transfer residual toner on the first image carrier 1 after the transfer is cleaned by the cleaning device 105. This operation is continuously performed to form an image on one or a plurality of recording media (P) of transfer paper. Further, a reference pattern on the second image carrier 2 is disposed between the first image carrier 1 and the fixing device 106 on the second image carrier 2 that also serves as the recording medium conveyance means 21. An image density detecting means 4 for detecting the image density of the third toner image is arranged. In the image density detecting means 4, four image density sensors 41, 42, 43, 44 are arranged in a line in the main scanning direction.
During the image forming operation, the image forming apparatus 100 is connected between the recording medium (P) on the second image carrier 2 that also serves as the recording medium conveying means 21, that is, the recording medium (P) and the recording medium. One reference pattern 3 is formed at a corresponding position between the recording media (P). Then, when the reference pattern 3 comes to a position facing the image density sensors 41, 42, 43, 44 of the image density detection means 4, the image density sensors 41, 42, 43, 44 of the image density detection means 4 change the image density. Detected. The toner image of the reference pattern 3 is cleaned by the belt cleaning device 107 as it is.
The toner replenishing device 130 detects the magnetic permeability of the developer (carrier) by a toner concentration sensor 131 attached to the developing device 103. Each time an image is formed on the recording medium (P), the toner replenishment amount is changed according to the current value of the output value of the toner density sensor 131 with respect to the target value, and the toner density of the developer is controlled to be constant. Yes.

However, the developing ability of the developer changes as the charging ability changes due to environmental fluctuations, deterioration with time, etc., and as a result, the image density changes under a constant imaging condition. Therefore, the image density adjusting means 5 is created at a position corresponding to the recording medium (P) on the second image carrier 2 also serving as the recording medium conveying means 21 in order to keep the image density constant. The image density of the reference pattern 3 is detected by the image density detection means 4.
The image density adjusting means 5 detects the image density of the reference pattern 3 by the image density sensors 41, 42, 43, 44 of the image density detecting means 4, and the output causes the toner density so that the image density approaches the target value. Feedback to density control. When it is determined that the current image density is higher than the target image density value, the toner density is set to be low, and when it is determined to be light, the toner is supplied by setting it high. As a result, the image density is controlled to be constant. In this embodiment, this reference pattern 3 is created for every 10 sheets of transfer paper that is the recording medium (P), and the image density is detected and fed back to toner density control.

In the image forming apparatus 100, the next reference pattern 3 is created at a position different from the position where the reference pattern 3 was created last time. An example of this will be described with reference to FIG.
The positions in the main scanning direction in the illustrated arrow (G) direction where the image density sensors 41, 42, 43, and 44 of the image density detecting means 4 are arranged are P1, P2, P3, and P4, respectively. The creation position of the first reference pattern 3 in the main scanning direction in the illustrated arrow (G) direction is sequentially formed as P2, P2 for the second time, P3 for the third time, and P4 for the fourth time. Created at a position that rotates the positions of P1, P2, P3, and P4 that are sequentially formed and transferred at positions different from the previously created position with respect to the main scanning direction indicated by the arrow (G) of the recorded image. Then, it is created again at the same position at the fifth time.
By changing the creation position of the reference pattern 3 in this way, the cleaning device 105 causes the number of transfers of the reference pattern 3 to enter the same position once every four times.
Normally, in the conventional image forming apparatus, the reference pattern creation position is fixed, and the transfer residual of the reference pattern is input at a predetermined position every time.
However, in the cleaning device 105 of the image forming apparatus 100 of the present embodiment, the ratio is once every four times, so that the wear of the cleaning blade 150 is reduced and the replacement cycle of the cleaning blade 150 can be extended.

FIG. 3 is a basic configuration diagram of a second example of the image forming apparatus 200 according to the embodiment of the present invention.
FIG. 4 is a diagram showing the creation position of the reference pattern 3 for image density adjustment in the second example of the image forming apparatus 200 according to the embodiment of the present invention.
3 and 4, the image forming apparatus 200 is positioned in the counterclockwise direction indicated by the arrow (C) in the figure at a position facing the intermediate transfer belt of the intermediate transfer body 20 that is the second image carrier 2. Four rotating photosensitive drums of the first image carrier 1 are arranged. The four first image carriers 1 are arranged in parallel in a black image forming unit 11, a yellow image forming unit 12, a cyan image forming unit 13, and a magenta (M) image forming unit 14.
Around each of the first image carriers 1, a charging device 101, an exposure device 102, a developing device 103, a primary transfer device 140, and a cleaning device 105 are sequentially arranged. By using these devices, the steps of charging, exposing, developing, transferring, and cleaning are performed on the photosensitive drums of the first image carriers 1, so that the second image carrier 2 of the intermediate transfer system is used. A toner image is formed on the intermediate transfer member 20 which is an intermediate transfer belt.

The developing devices 103 of the black image forming unit 11, the yellow image forming unit 12, the cyan image forming unit 13, and the magenta image forming unit 14 include K (black), Y (yellow), C (cyan), and M (magenta), respectively. ) Developer. K, Y, C, and M toner images are formed on the respective first image carriers 1. Each developing device 103 includes a toner replenishing device 130 for replenishing each toner into each developing device 103. The toner image formed on the intermediate transfer member 20 of the second image carrier 2 moving in the clockwise direction of the arrow (D) shown in the figure is transferred onto the recording medium (P) by the secondary transfer device 141. Transcribed.
Subsequently, the toner image transferred onto the recording medium (P) is conveyed to the fixing device 106 by the conveying belt 22 that moves in the counterclockwise direction indicated by the arrow (E) in the figure, and is fixed.
The transfer residual toner on the first image carrier 1 after the primary transfer is transferred to the residual toner on the intermediate transfer body 20 of the second image carrier 2 after the secondary transfer by each cleaning device 105. Are cleaned by the belt cleaning device 107. This operation is continuously performed to form a recorded image on one or a plurality of recording media (P) transfer paper. Further, on the intermediate transfer member 20 of the second image carrier 2, the black of the reference pattern 3 on the intermediate transfer member 20 between the most downstream first image carrier 1 and the secondary transfer device 141. And an image density detecting means 4 for detecting the image density of the color toner image. In the image density detecting means 4, four image density sensors 41, 42, 43, 44 are arranged in a line in the main scanning direction.

During the image forming operation, the image forming apparatus 200 is between the recording medium (P) on the second image carrier 2 of the intermediate transfer body 20, that is, the recording medium (P) and the recording medium (P ), One reference pattern 3 is formed at a corresponding position. Then, when the reference pattern 3 comes to a position facing the image density sensors 41, 42, 43, 44 of the image density detection means 4, the image density sensors 41, 42, 43, 44 of the image density detection means 4 change the image density. Detected. The black and color toner images of the reference pattern 3 enter the secondary transfer nip, that is, the portion where the second image carrier 2 of the intermediate transfer body 20 and the secondary transfer roller of the secondary transfer device 141 come into contact with each other.
In the secondary transfer nip, when a position corresponding to the recording medium (P) passes, no transfer bias is applied to the secondary transfer roller of the secondary transfer device 141, and most of the toner image of the reference pattern 3 is transferred. Remains on the second image carrier 2 of the intermediate transfer member 20 as it is.
Then, cleaning is performed by the belt cleaning device 107. Further, part of the black and color toner images of the reference pattern 3 are transferred onto the secondary transfer roller of the secondary transfer device 141 and cleaned by the secondary transfer cleaning device 142.

The toner replenishing device 130 detects the magnetic permeability of each developer (carrier) by a toner concentration sensor 131 attached to each developing device 103. Each time an image is formed on the recording medium (P), the toner replenishment amount is changed according to the current value of the output value of the toner density sensor 131 with respect to the target value, and the toner density of the developer is controlled to be constant. Yes.
However, the developing ability of the developer changes as the charging ability changes due to environmental changes, deterioration with time, and the like, and as a result, the image density changes under a constant imaging condition.
For this reason, the image density adjusting means 5 uses the reference pattern 3 created at a position corresponding to the recording medium (P) on the second image carrier 2 of the intermediate transfer body 20 in order to keep the image density constant. The image density is detected by the image density detection means 4.
The image density adjusting means 5 detects the image density of the reference pattern 3 by the image density sensors 41, 42, 43, 44 of the image density detecting means 4, and the output causes the toner density so that the image density approaches the target value. Feedback to density control. When it is determined that the current image density is higher than the target image density value, the toner density is set to be low, and when it is determined to be light, the toner is supplied by setting it high. As a result, the image density is controlled to be constant. In this embodiment, this reference pattern 3 is created for every 10 sheets of transfer paper that is the recording medium (P), and the image density is detected and fed back to toner density control.

In the image forming apparatus 200, the next reference pattern 3 is created at a position different from the position where the reference pattern 3 was created last time. An example of this will be described with reference to FIG.
The positions in the main scanning direction in the illustrated arrow (G) direction where the image density sensors 41, 42, 43, and 44 of the image density detecting means 4 are arranged are P1, P2, P3, and P4, respectively.
The creation positions of the reference pattern 3 in the main scanning direction in the illustrated arrow (G) direction in each black image forming unit 11, yellow image forming unit 12, cyan image forming unit 13, and magenta image forming unit 14 for the first time are as follows. In the position shown in FIG. That is, P1 for the first image carrier 1 of the black image forming unit 11, P2 for the first image carrier 1 of the yellow image forming unit 12, and P3 for the first image carrier 1 of the cyan image forming unit 13. In the first image carrier 1 of the magenta image forming unit 14, P4 is set.
In the second and subsequent times, as shown in FIG. 4, they are created at positions shifted one by one, and are created again at the same position in the fifth time. By changing the creation position in this manner, the number of times that the transfer residue of the reference pattern 3 enters the same position in each cleaning device 105 becomes a ratio of once every four times.
Normally, in a conventional image forming apparatus having a plurality of photoconductors, the reference pattern creation position is fixed for each photoconductor (toner), and the transfer residual of the reference pattern is input at a fixed position every time. For example, the transfer residual is input every time at the P1 position for the K toner, the P2 position for the Y toner, the P3 position for the C toner, and the P4 position for the M toner.
However, in the image forming apparatus 200 of the present embodiment, the ratio is once every four times, so that the wear of the cleaning blade 150 is reduced and the replacement cycle of the cleaning blade 150 can be extended.

Next, an example in which each of the K, Y, C, and M toners having an average particle diameter of 6 μm or less and an average particle diameter of 5.8 μm is used in the image forming apparatus 200 will be described.
In the conventional method for creating a reference pattern, when toner having an average particle diameter of 5.8 μm is used, the wear of the cleaning blade is accelerated over time at a position corresponding to the edge portion of the reference pattern of each toner. For example, K is P1, Y is P2, C is P3, and M is P4. And the replacement cycle of the cleaning blade tends to be shortened.
However, in the case of the image forming apparatus 200, the transfer residual toner of the reference pattern 3 is input to the cleaning apparatus 105 once in four times, and the wear of the cleaning blade 150 is reduced. Therefore, at the same time, it is possible to use a toner having a smaller particle diameter than the conventional one, and accordingly, it is possible to provide the image forming apparatus 200 that forms a high-quality image by improving the granularity of the toner image dots.

FIG. 5 is a basic configuration diagram of a third example of the image forming apparatus 300 according to the embodiment of the present invention.
FIG. 6 is a diagram showing the creation position of the reference pattern 3 for image density adjustment in the third example of the image forming apparatus 300 according to the embodiment of the present invention.
5 and 6, the image forming apparatus 300 rotates in the clockwise direction indicated by the arrow (A) in the figure at a position facing the second image carrier 2 that also serves as the recording medium transport unit 21. Four photosensitive drums of the first image carrier 1 are arranged. The four first image carriers 1 are arranged in parallel in a black image forming unit 11, a yellow image forming unit 12, a cyan image forming unit 13, and a magenta (M) image forming unit 14.
Around each of the first image carriers 1, a charging device 101, an exposure device 102, a developing device 103, a transfer device 104, and a cleaning device 105 are sequentially arranged. Each of the first image carriers 1 is conveyed onto the second image carrier 2 that also serves as the recording medium conveying means 21 by performing charging, exposure, development, transfer, and cleaning processes. A toner image is formed on the transferred recording medium (P).

The developing devices 103 of the black image forming unit 11, the yellow image forming unit 12, the cyan image forming unit 13, and the magenta image forming unit 14 are filled with K, Y, C, and M developers, respectively. On each first image carrier 1, toner images of K, Y, C, and M are formed. Each developing device 103 includes a toner replenishing device 130 for replenishing each toner into each developing device 103.
The recording medium (P) on which the toner image is formed is fixed to the fixing device 106 by the second image carrier 2 that also serves as the recording medium conveying means 21 that moves counterclockwise in the direction of the arrow (F) shown in the figure. And the toner image is fixed.
The transfer residual toner on each first image carrier 1 after the transfer is cleaned by each cleaning device 105. This operation is continuously performed to form an image on one or a plurality of recording media (P). In addition, on the recording medium transport unit 21 of the second image carrier 2, a reference on the recording medium transport unit 21 is provided between the most downstream first image carrier 1 and the belt cleaning device 107. Image density detecting means 4 for detecting the image density of the toner image of pattern 3 is arranged. In the image density detecting means 4, four image density sensors 41, 42, 43, 44 are arranged in a line in the main scanning direction.
Among these, the image density sensor 41 is a sensor dedicated to detecting the image density of K toner and cannot detect the image density of color toner. The image density sensors 42 to 44 are dedicated sensors for color toner image density detection, and cannot detect the image density of K toner.

During the image forming operation, the image forming apparatus 300 performs a recording medium (P) between the recording medium transporting means 21 of the second image carrier 2, that is, the recording medium (P) and the recording medium. One reference pattern 3 is formed at a position corresponding to (P). Then, when the reference pattern 3 comes to a position facing the image density sensors 41, 42, 43, 44 of the image density detection means 4, the image density sensors 41, 42, 43, 44 of the image density detection means 4 change the image density. Detected. The toner image of the reference pattern 3 is cleaned by the belt cleaning device 107 as it is.
The toner replenishing device 130 detects the magnetic permeability of the developer (carrier) by a toner concentration sensor 131 attached to the developing device 103. Each time an image is formed on the recording medium (P), the toner replenishment amount is changed according to the current value of the output value of the toner density sensor 131 with respect to the target value, and the toner density of the developer is controlled to be constant. Yes.
However, the developing ability of the developer changes as the charging ability changes due to environmental fluctuations, deterioration with time, etc., and as a result, the image density changes under a constant imaging condition. Therefore, the image density adjusting means 5 is created at a position corresponding to the recording medium (P) on the second image carrier 2 also serving as the recording medium conveying means 21 in order to keep the image density constant. The image density of the reference pattern 3 is detected by the image density detection means 4.
The image density adjusting means 5 detects the image density of the reference pattern 3 by the image density sensors 41, 42, 43, 44 of the image density detecting means 4, and the output causes the toner density so that the image density approaches the target value. Feedback to density control. When it is determined that the current image density is higher than the target image density value, the toner density is set to be low, and when it is determined to be light, the toner is supplied by setting it high. As a result, the image density is controlled to be constant. In this embodiment, this reference pattern 3 is created for every 10 sheets of transfer paper that is the recording medium (P), and the image density is detected and fed back to toner density control.

In the image forming apparatus 300, the reference pattern 3 for the next time is created at a position different from the position where the reference pattern 3 is created for the color toner only. An example of this will be described with reference to FIG.
The positions in the main scanning direction in the illustrated arrow (G) direction where the image density sensors 41, 42, 43, and 44 of the image density detecting means 4 are arranged are P1, P2, P3, and P4, respectively.
The creation positions of the reference pattern 3 in the main scanning direction in the illustrated arrow (G) direction in each black image forming unit 11, yellow image forming unit 12, cyan image forming unit 13, and magenta image forming unit 14 for the first time are as follows. In the position shown in FIG. That is, P1 for the first image carrier 1 of the black image forming unit 11, P2 for the first image carrier 1 of the yellow image forming unit 12, and P3 for the first image carrier 1 of the cyan image forming unit 13. In the first image carrier 1 of the magenta image forming unit 14, P4 is set.
From the second time onward, as shown in FIG. 6, the first image carrier 1 of the black image forming unit 11 is set to the same position P1. In the yellow image forming unit 12, the cyan image forming unit 13, and the magenta image forming unit 14, the positions of P2, P3, and P4 are generated at the rotation positions, and are generated at the same positions again at the fourth time. By changing the creation position in this way, in the cleaning device 105 other than the black image forming unit 11, the number of times the transfer residual of the reference pattern 3 enters the same position is once every three times.

Normally, in a conventional image forming apparatus having a plurality of photoconductors, the reference pattern creation position is fixed for each photoconductor (toner), and the transfer residual of the reference pattern is input at a fixed position every time. For example, Y toner is input to the position P2, C toner is input to the position P3, and M toner is input to the position P4 every time.
However, in the image forming apparatus 300 of the present embodiment, the transfer residual input is performed once every three times to the cleaning devices 105 of the yellow image forming unit 12, the cyan image forming unit 13, and the magenta image forming unit 14, respectively. The wear of the cleaning blade 150 of the yellow image forming unit 12, the cyan image forming unit 13, and the magenta image forming unit 14 is reduced, and the replacement cycle of the cleaning blade 150 can be extended.

Next, an example in which Y, C, and M toners having a shape factor (SF-1) representing the degree of toner sphericalness of 150 or less and a shape factor (SF-1) of 140 is used for the image forming apparatus 300 will be described. To do.
A substantially spherical toner having a convex shape, and a shape factor (SF-1) representing a degree of the spherical shape of the toner is defined by the following equation.
(SF-1) = (MXLNG) ² / AREA × π / 4 × 100
However, MXLNG represents the maximum length of a shape formed by projecting toner onto a two-dimensional plane. AREA represents the area of a figure formed by projecting toner onto a two-dimensional plane.
In the conventional method for creating a reference pattern, when a toner having a shape factor (SF-1) of 160 is used, the cleaning blade wears over time at a position corresponding to the edge portion of each toner reference pattern. For example, K is P1, Y is P2, C is P3, and M is P4. And the replacement cycle of the cleaning blade tends to be shortened.
However, in the case of the image forming apparatus 300, the transfer residual toner of the reference pattern 3 is input to the cleaning devices 105 and 107 of the yellow image forming unit 12, the cyan image forming unit 13, and the magenta image forming unit 14 three times. Once. Further, the wear of the cleaning blades 150 and 170 is reduced. Therefore, at the same time, it is possible to use toner whose shape is closer to a sphere than in the past, and accordingly, it is possible to provide an image forming apparatus 300 that forms a high-quality image by improving the granularity of toner image dots. .

FIG. 7 is a basic configuration diagram of a fourth example of the image forming apparatus 400 according to the embodiment of the present invention.
FIG. 8 is a basic configuration diagram of the image density detecting means moving means 40 of the image forming apparatus 400 (500) according to the embodiment of the present invention.
FIG. 9 is a diagram illustrating the detection timing of the reference pattern 3 and the update timing of the toner density target value of the image forming apparatus 400 (500) according to the embodiment of the present invention.
FIG. 10 is a diagram for explaining the operation of the image forming apparatus 400 according to the embodiment of the present invention.
7 to 10, the image forming apparatus 400 is positioned in the counterclockwise direction indicated by the arrow (C) in the figure at a position facing the intermediate transfer belt of the intermediate transfer body 20 that is the second image carrier 2. Four rotating photosensitive drums of the first image carrier 1 are arranged. The four first image carriers 1 are arranged in parallel in the black image forming unit 11, the yellow image forming unit 12, the cyan image forming unit 13, and the magenta image forming unit 14.
Around each of the first image carriers 1, a charging device 101, an exposure device 102, a developing device 103, a primary transfer device 140, and a cleaning device 105 are sequentially arranged. By these devices, the toner image is formed on the intermediate transfer member 20 of the intermediate transfer belt by performing the charging, exposure, development, transfer, and cleaning processes on the photosensitive drum of each first image carrier 1. It is formed.

The developing devices 103 of the black image forming unit 11, the yellow image forming unit 12, the cyan image forming unit 13, and the magenta image forming unit 14 include K (black), Y (yellow), C (cyan), and M (magenta), respectively. ) Developer. On each first image carrier 1, toner images of K, Y, C, and M are formed. Each developing device 103 includes a toner replenishing device 130 for replenishing each toner into each developing device 103. The toner image formed on the intermediate transfer member 20 of the second image carrier 2 moving in the clockwise direction of the arrow (D) shown in the figure is transferred onto the recording medium (P) by the secondary transfer device 141. Transcribed.
Subsequently, the toner image transferred onto the recording medium (P) is conveyed to the fixing device 106 by the conveying belt 22 that moves in the counterclockwise direction indicated by the arrow (E) in the figure, and is fixed.
The transfer residual toner on the first image carrier 1 after the primary transfer is transferred to the residual toner on the intermediate transfer body 20 of the second image carrier 2 after the secondary transfer by each cleaning device 105. Are cleaned by the belt cleaning device 107. This operation is continuously performed to form a recorded image on one or a plurality of recording media (P) transfer paper.

Further, on the intermediate transfer member 20 of the second image carrier 2, the toner image of the reference pattern 3 on the intermediate transfer member 20 between the most downstream first image carrier 1 and secondary transfer device 141. An image density sensor 41 of the image density detecting means 4 for detecting the image density of the image is arranged.
The image density sensor 41 of the image density detection means 4 is installed in a state that it can be moved in the main scanning direction by the image density detection means moving means 40. Details of a moving mechanism for moving the image density sensor 41 of the image density detecting means 4 by the image density detecting means moving means 40 will be described below with reference to FIG.
The image density sensor 41 of the image density detecting means 4 is slid along the main scanning direction indicated by the arrow (G) in the figure by a guide shaft 46 whose left and right ends are supported by left and right end support plates 45 (left and right). It is supported movably. The image density sensor 41 of the image density detection means 4 is mounted on an endless belt-like density detection means conveyance belt 48 that is rotationally driven by a motor 47. Then, the image density sensor 41 of the image density detection means 4 is moved by the controller 49 in the left-right direction along the main scanning direction indicated by the arrow (G) in the figure by the driving force of the motor 47.
Accordingly, the range from the left end support plate 45 (left) to the right end support plate 45 (right) in FIG. 8 is the movable range (H) of the image density sensor 41 of the image density detection means 4. The image density sensor 41 of the image density detection means 4 is a reference created within this range on the intermediate transfer body 20 of the second image carrier 2 with respect to the main scanning direction indicated by the arrow (G) in the figure. The image density of pattern 3 can be detected.

The toner density control of the developer will be described. The toner replenishing device 130 detects the magnetic permeability of each developer (carrier) by a toner concentration sensor 131 attached to each developing device 103. Each time an image is formed on the recording medium (P), the toner replenishment amount is changed according to the current value of the output value of the toner density sensor 131 with respect to the target value, and the toner density of the developer is controlled to be constant. Yes.
However, the developing ability of the developer changes as the charging ability changes due to environmental changes, deterioration with time, and the like, and as a result, the image density changes under a constant imaging condition.
For this reason, the image density adjusting means 5 uses the reference pattern 3 created at a position corresponding to the recording medium (P) on the second image carrier 2 of the intermediate transfer body 20 in order to keep the image density constant. The image density is detected by the image density detection means 4.
The image density adjusting means 5 detects the image density of the reference pattern 3 by the image density sensor 41 of the image density detecting means 4 and feeds back to the toner density control so that the image density approaches the target value by the output. When it is determined that the current image density is higher than the target image density value, the toner density is set to be low, and when it is determined to be light, the toner is supplied by setting it high. As a result, the image density is controlled to be constant.

The target value for detection of the reference pattern 3 and toner density control will be described with reference to FIG. One reference pattern 3 is created for each sheet of transfer paper on the recording medium (P). The sizes of the reference patterns 3 are all a length a (for example, 10 mm) in the main scanning direction and a length d (for example, 15 mm) in the sub-scanning direction. It is assumed that K (black) is used between the sheets after 4n + 1 sheets, Y is applied between the sheets after 4n + 2 sheets, C is applied between the sheets after 4n + 3 sheets, and M is applied between the sheets after 4 (n + 1) sheets. In this manner, one reference pattern 3 is created for each interval between transfer sheets of the recording medium (P), and the image density is detected.
When the image density of the reference pattern 3 of K toner between the sheets after the 4n + 1th sheet is higher / lower than the target image density, the target is set so that the toner density of the developer in the black image forming unit 11 becomes lower / higher. Toner density Tk (n) is set. From 4n + 2 to 4 (n + 1) + 1st sheet, an appropriate amount of K toner is supplied to the developing device 103 of the black image forming unit 11 with Tk (n) as a target value.

When the image density of the reference pattern 3 of Y toner between the sheets after 4n + 2 sheets is higher / lower than the target image density, the target is set so that the toner density of the developer in the yellow image forming unit 12 is lower / higher. Toner density Ty (n) is set. From 4n + 3 to 4 (n + 1) + 2nd sheet, an appropriate amount of Y toner is supplied to the developing device 103 of the yellow image forming unit 12 with Ty (n) as a target value.
When the image density of the reference pattern 3 of C toner between the sheets after the 4n + 3rd sheet is higher / lower than the target image density, the target is set so that the toner density of the developer in the cyan image forming unit 13 is lower / higher. Toner density Tc (n) is set. From 4 (n + 1) to 4 (n + 1) + 3rd sheet, an appropriate amount of C toner is supplied to the developing device 103 of the cyan image forming unit 13 with Tc (n) as a target value.
When the image density of the M toner reference pattern 3 between the sheets after the 4th (n + 1) th sheet is higher / lower than the target image density, the toner density of the developer in the magenta image forming unit 14 becomes lower / higher. In this way, the target toner density Tm (n) is set. From the 4th (n + 1) +1 to the 4th (n + 2) th sheet, an appropriate amount of M toner is supplied to the developing device 103 of the magenta image forming unit 14 with Tm (n) as a target value.

The cleaning of the reference pattern 3 will be described. Each reference pattern 3 moves together with the second image carrier 2 of the intermediate transfer body 20 after the image density is detected by the image density sensor 41 of the image density detection means 4. As it is, it enters the secondary transfer nip, that is, the portion where the intermediate transfer member 20 of the second image carrier 2 and the secondary transfer roller of the secondary transfer device 141 come into contact with each other.
In the secondary transfer nip, no transfer bias is applied to the secondary transfer roller of the secondary transfer device 141 when the reference pattern 3 at a position corresponding to the recording medium (P) passes. Therefore, most of the toner image of the reference pattern 3 remains on the second image carrier 2 of the intermediate transfer body 20 as it is.
Then, cleaning is performed by the belt cleaning device 107. Further, part of the black and color toner images of the reference pattern 3 are transferred onto the secondary transfer roller of the secondary transfer device 141 and cleaned by the secondary transfer cleaning device 142.

The movement sequence of the position of the reference pattern 3 and the image density detection position of the image density sensor 41 of the image density detection means 4 will be described with reference to FIG.
In the above configuration, the image forming apparatus 400 creates the next reference pattern 3 at a position different from the position previously created with respect to the main scanning direction indicated by the arrow (G) in the image forming apparatus 400.
First, when the power is turned on, the control unit 49 drives the motor 47 to move the image density sensor 41 of the image density detection means 4 to HP (home position).
During the first image forming operation, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and stops at an arbitrary position P1 different from the home position (HP). . The K (black) reference pattern 3 is formed at a position opposite to P1 on the second image carrier 2 of the intermediate transfer member 20 between the first and second sheets of transfer paper on the recording medium (P). Then, the image density is detected.
During the image forming operation of the second sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and stops at an arbitrary position P2 different from P1. The Y (yellow) reference pattern 3 is formed at a position opposite to P2 on the second image carrier 2 of the intermediate transfer body 20 between the second and second sheets of transfer paper of the recording medium (P). Then, the image density is detected.

During the image forming operation for the third sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and stops at an arbitrary position P3 different from P2. The C (cyan) reference pattern 3 is formed at a position opposite to P3 on the second image carrier 2 of the intermediate transfer body 20 between the third sheet of transfer paper on the recording medium (P). Then, the image density is detected.
During the image forming operation for the fourth sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the drawing, and stops at an arbitrary position P4 different from P3. The M (magenta) reference pattern 3 is formed at a position opposite to P4 on the second image carrier 2 of the intermediate transfer body 20 between the fourth and subsequent sheets of transfer paper on the recording medium (P). Then, the image density is detected.
During the image forming operation for the fifth sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the drawing, and stops at an arbitrary position P5 different from P4. The K (black) reference pattern 3 is formed at a position opposite to P5 on the second image carrier 2 of the intermediate transfer body 20 between the fifth and subsequent sheets of the transfer paper of the recording medium (P). Then, the image density is detected.

Similarly, during the (4n + 1) -th image forming operation, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and an arbitrary position different from P (4n). Stop at P (4n + 1). Between the (4n + 1) th sheets of the transfer paper of the recording medium (P), the K reference pattern 3 is positioned at a position facing P (4n + 1) on the second image carrier 2 of the intermediate transfer body 20. Create an image and detect the image density.
During the (4n + 2) -th image forming operation, the motor 47 is driven to move the image density sensor 41 in the main scanning direction and stop at an arbitrary position P (4n + 2) different from P (4n + 1). Between the (4n + 2) th sheet of transfer paper on the recording medium (P), the Y reference pattern 3 is positioned at a position facing P (4n + 2) on the second image carrier 2 of the intermediate transfer body 20. Create an image and detect the image density.
During the (4n + 3) -th image forming operation, the motor 47 is driven to move the image density sensor 41 in the main scanning direction and stop at an arbitrary position P (4n + 3) different from P (4n + 2). Between the (4n + 3) th sheet of the transfer sheet of the recording medium (P), the C reference pattern 3 is positioned at a position facing P (4n + 3) on the second image carrier 2 of the intermediate transfer body 20. Create an image and detect the image density.

During the 4 (n + 1) th image forming operation, the motor 47 is driven to move the image density sensor 41 in the main scanning direction and stop at an arbitrary position P (4 (n + 1)) different from P (4n + 3). . Between the (4 (n + 1)) th sheet of transfer paper on the recording medium (P), the M reference pattern 3 is transferred to P (4 (n + 1)) on the second image carrier 2 of the intermediate transfer body 20. ) To detect the image density.
During the 4 (n + 1) + 1-th image forming operation, the motor 47 is driven to move the image density sensor 41 in the main scanning direction, and an arbitrary position P (4 (n + 1)) different from P (4 (n + 1)) Stop at +1). Between the (4 (n + 1) +1) th sheets of transfer paper on the recording medium (P), the reference pattern 3 of K (black) is transferred to P (2) on the second image carrier 2 of the intermediate transfer body 20. 4 (n + 1) +1), and the image density is detected. The following is omitted.
As described above, by repeatedly changing the image formation position of the reference pattern 3 and the image density detection position of the image density sensor 41 as a set, the toner image of the reference pattern 3 input to each cleaning device is at a different position each time. There is no input.

FIG. 11 is a basic configuration diagram of a fifth example of the image forming apparatus 500 according to the embodiment of the present invention.
FIG. 12 is a diagram for explaining the first operation of the fifth example of the image forming apparatus 500 according to the embodiment of the present invention.
FIG. 13 is a diagram for explaining the operation 2 of the fifth example of the image forming apparatus 500 according to the embodiment of the present invention.
In FIG. 11, the image forming apparatus 500 has four fourth rotations that rotate in the clockwise direction indicated by the arrow (A) in the figure at a position facing the second image carrier 2 that also serves as the recording medium transport unit 21. A photosensitive drum of one image carrier 1 is disposed. The four first image carriers 1 are arranged in parallel in the black image forming unit 11, the yellow image forming unit 12, the cyan image forming unit 13, and the magenta image forming unit 14.
Around each of the first image carriers 1, a charging device 101, an exposure device 102, a developing device 103, a transfer device 104, and a cleaning device 105 are sequentially arranged. Each of the first image carriers 1 is conveyed onto the second image carrier 2 that also serves as the recording medium conveying means 21 by performing charging, exposure, development, transfer, and cleaning processes. A toner image is formed on the transferred recording medium (P).

The developing devices 103 of the black image forming unit 11, the yellow image forming unit 12, the cyan image forming unit 13, and the magenta image forming unit 14 include K (black), Y (yellow), C (cyan), and M (magenta), respectively. ) Developer.
K, Y, C, and M toner images are formed on the respective first image carriers 1. Each developing device 103 includes a toner replenishing device 130 for replenishing each toner into each developing device 103.
The recording medium (P) on which the toner image is formed is fixed to the fixing device 106 by the second image carrier 2 that also serves as the recording medium conveying means 21 that moves counterclockwise in the direction of the arrow (F) shown in the figure. And the toner image is fixed.
The transfer residual toner on each first image carrier 1 after the transfer is cleaned by each cleaning device 105. This operation is continuously performed to form an image on one or a plurality of recording media (P).

Further, on the recording medium conveying means 21 of the second image carrier 2, the recording medium conveying means 21 is located between the first downstream image carrier 1 and the belt cleaning device 107. Image density detecting means 4 for detecting the image density of the reference pattern 3 is arranged. The image density detecting unit 4 is installed in a state where the image density sensor 41 can be moved in the main scanning direction by the image density detecting unit moving unit 40 and detects the image density of the toner image of the reference pattern 3. A moving mechanism for moving the image density sensor 41 of the image density detecting means 4 by the image density detecting means moving means 40 will be described with reference to FIG.
The image density sensor 41 of the image density detecting means 4 is slid along the main scanning direction indicated by the arrow (G) in the figure by a guide shaft 46 whose left and right ends are supported by left and right end support plates 45 (left and right). It is supported movably. The image density sensor 41 of the image density detection means 4 is mounted on an endless belt-like density detection means conveyance belt 48 that is rotationally driven by a motor 47. Then, the image density sensor 41 of the image density detection means 4 is moved by the controller 49 in the left-right direction along the main scanning direction indicated by the arrow (G) in the figure by the driving force of the motor 47.
Accordingly, the range from the left end support plate 45 (left) to the right end support plate 45 (right) in FIG. 8 is the movable range (H) of the image density sensor 41 of the image density detection means 4. The image density of the reference pattern 3 created within this range on the intermediate transfer member 20 of the second image carrier 2 can be detected with respect to the main scanning direction indicated by the arrow (G) shown in the figure.

Next, toner density control of the developer of the image forming apparatus 500 will be described. Each toner replenishing device 130 detects the magnetic permeability of each developer (carrier) by a toner concentration sensor 131 attached to each developing device 103. Each time an image is formed on the recording medium (P), the toner replenishment amount is changed according to the current value of the output value of the toner density sensor 131 with respect to the target value, and the toner density of the developer is controlled to be constant. Yes.
However, the developing ability of the developer changes as the charging ability changes due to environmental fluctuations, deterioration with time, etc., and as a result, the image density changes under a constant imaging condition. Therefore, the image density adjusting means 5 is created at a position corresponding to the recording medium (P) on the second image carrier 2 also serving as the recording medium conveying means 21 in order to keep the image density constant. The image density of the reference pattern 3 is detected by the image density detection means 4.
The output from the image density sensor 41 of the image density detection means 4 feeds back to the toner density control so that the image density approaches the target value. When it is determined that the current image density is higher than the target image density value, the toner density is set to be low, and when it is determined to be light, the toner is supplied by setting it high. As a result, the image density is controlled to be constant.

The target value for the detection of the reference pattern 3 and the toner density control in the image forming apparatus 500 will be described with reference to FIG. One reference pattern 3 is created for each sheet of transfer paper on the recording medium (P). The sizes of the reference patterns 3 are all a length a (for example, 10 mm) in the main scanning direction and a length d (for example, 15 mm) in the sub-scanning direction. K between 4n + 1 sheets, Y between 4n + 2 sheets, C between 4n + 3 sheets, and M between 4 (n + 1) sheets. In this manner, one reference pattern 3 is created for each interval between transfer sheets of the recording medium (P), and the image density is detected.
This is the case when the image density of the reference pattern 3 of K toner between the sheets after the 4n + 1th sheet is higher or lower than the target image density. In such a case, the target toner concentration Tk (n) is set so that the toner concentration of the developer in the developing device 103 of the black image forming unit 11 is low or high. From 4n + 2 to 4 (n + 1) + 1st sheet, an appropriate amount of K toner is supplied to the developing device 103 of the black image forming unit 11 with Tk (n) as a target value.

This is the case when the image density of the reference pattern 3 of Y toner between the 4n + second sheet is higher or lower than the target image density. In such a case, the target toner concentration Ty (n) is set so that the toner concentration of the developer in the developing device 103 of the yellow image forming unit 12 is low or high. From 4n + 3 to 4 (n + 1) + 2nd sheet, an appropriate amount of Y toner is supplied to the developing device 103 of the yellow image forming unit 12 with Ty (n) as a target value.
This is the case when the image density of the reference pattern 3 of C toner between the sheets after the 4n + 3rd sheet is higher or lower than the target image density. In such a case, the target toner concentration Tc (n) is set so that the toner concentration of the developer in the developing device 103 of the cyan image forming unit 13 is low or high. From 4 (n + 1) to 4 (n + 1) + 3rd sheet, an appropriate amount of C toner is supplied to the developing device 103 of the cyan image forming unit 13 with Tc (n) as a target value.
This is the case when the image density of the M toner reference pattern 3 between the 4th (n + 1) th sheets of paper is higher or lower than the target image density. In such a case, the target toner concentration Tm (n) is set so that the toner concentration of the developer in the developing device 103 of the magenta image forming unit 14 is low / high. From the 4th (n + 1) +1 to the 4th (n + 2) th sheet, an appropriate amount of M toner is supplied to the developing device 103 of the magenta image forming unit 14 with Tm (n) as a target value.
After detecting the image density, each reference pattern 3 moves together with the second image carrier 2 that also serves as the recording medium conveying means 21 and is cleaned as it is by the belt cleaning device 107.

A moving sequence of the position of the reference pattern 3 and the image density detection position of the image density sensor 41 of the image density detection unit 4 in the image forming apparatus 500 will be described with reference to FIG.
In the above configuration, in the image forming apparatus 500, the next reference pattern 3 is created at a position bmm, for example, 20 mm away from the position where the reference pattern 3 is created the last time with respect to the main scanning direction indicated by the arrow (G). Create
First, when the power is turned on, the control unit 49 drives the motor 47 to move the image density sensor 41 of the image density detection means 4 to HP (home position).
A K reference pattern 3 is formed at a position opposite to P1 on the second image carrier 2 that also serves as the recording medium conveying means 21 between the first and second sheets of the recording medium (P). And image density is detected.
During the image forming operation of the second sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and stops at a position P2 that is a distance b (20 mm) from P1. . Between the second sheet of transfer paper on the recording medium (P), the Y (yellow) reference pattern 3 faces P2 on the second image carrier 2 that also serves as the recording medium conveying means 21. An image is formed at the position, and the image density is detected.

During the image forming operation for the third sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and stops at a position P3 that is a distance b (20 mm) away from P2. . A C reference pattern 3 is formed at a position opposite to P3 on the second image carrier 2 that also serves as the recording medium conveying means 21 between the third and third sheets of the recording medium (P). And image density is detected.
During the image forming operation of the fourth sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and stops at a position P4 that is a distance b (20 mm) away from P3. . An M reference pattern 3 is formed at a position opposite to P4 on the second image carrier 2 which also serves as the recording medium conveying means 21 between the fourth and subsequent sheets of the recording medium (P). And image density is detected.
During the image forming operation for the fifth sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure and stop at a position P5 that is a distance b (20 mm) away from P4. . Between the fifth and subsequent sheets of the transfer paper of the recording medium (P), the K (black) reference pattern 3 faces P5 on the second image carrier 2 that also serves as the recording medium conveying means 21. An image is formed at the position, and the image density is detected.

Similarly, during the (4n + 1) -th image forming operation, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and the distance b (20 mm) from P (4n). It stops at a position P (4n + 1) that is far away. Between the (4n + 1) th sheets of transfer paper of the recording medium (P), the reference pattern 3 of K (black) is used as P (2) on the second image carrier 2 that also serves as the recording medium conveying means 21. 4n + 1), the image density is detected.
During the (4n + 2) -th image forming operation, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and is separated from P (4n + 1) by a distance b (20 mm). Stop at position P (4n + 2). Between the (4n + 2) th sheet of the transfer paper of the recording medium (P), the Y reference pattern 3 is applied to P (4n + 2) on the second image carrier 2 that also serves as the recording medium conveying means 21. An image is formed at the opposite position, and the image density is detected.

During the (4n + 3) -th image forming operation, the motor 47 is driven, and the image density sensor 41 is moved in the main scanning direction indicated by the arrow (G) in the figure to be separated from P (4n + 2) by a distance b (20 mm). Stop at position P (4n + 3). Between the (4n + 3) th sheet of transfer paper on the recording medium (P), the C reference pattern 3 is applied to P (4n + 3) on the second image carrier 2 that also serves as the recording medium conveying means 21. An image is formed at the opposite position, and the image density is detected.
During the image forming operation for the 4th (n + 1) th sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction in the direction of the arrow (G) shown in the figure and away from P (4n + 3) by a distance b (20 mm). Stops at the position P (4 (n + 1)). Between the (4 (n + 1)) th sheets of transfer paper of the recording medium (P), the reference pattern 3 of M is used as P (2) on the second image carrier 2 that also serves as the recording medium conveying means 21. 4 (n + 1)), and image density is detected.
During the 4 (n + 1) + 1-th image forming operation, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and the distance b (from P (4 (n + 1)) It stops at a position P (4 (n + 1) +1) separated by 20 mm). Between the (4 (n + 1) +1) th sheets of transfer paper of the recording medium (P), the reference pattern 3 of K is used as P on the second image carrier 2 that also serves as the recording medium conveying means 21. An image is formed at a position facing (4 (n + 1) +1), and the image density is detected.

As described above, the image formation position of the repeated reference pattern 3 and the image density detection position of the image density sensor 41 are changed as a set. If this repetition is continued, the reference pattern 3 and the image density sensor 41 will exceed one end of the movable range (H) of the image density sensor 41. Processing in this case will be described with reference to FIG.
It is assumed that the K reference pattern 3 is detected at the position P (m) at the mth time. In the (m + 1) th time, the Y reference pattern 3 is detected at a position separated from the position P (m) by a distance b (20 mm), which is one end of the movable range (H) of the image density sensor 41. Will be exceeded. Therefore, the position returns to the position P1 where the first reference pattern 3 on the other end side is imaged, and the image density detection of Y of the (m + 1) th reference pattern 3 is performed at that position.
After that, the next reference pattern 3 is created at a position away from the previously created position of the reference pattern 3 in the arrow (G) direction in the illustrated main scanning direction by a distance b (20 mm) in the positive direction. Repeat the sequence. When the image density sensor 41 again exceeds one end of the movable range (H), the same operation is repeated.
As described above, by repeatedly changing the image formation position of the reference pattern 3 and the image density detection position of the image density sensor 41 as a set, the toner image of the reference pattern 3 input to each cleaning device is at the same position every time. There is no input. For example, when the moving distance b is 20 mm and the movable width (H) of the image density sensor 41 is 300 mm, the reference pattern 3 is input to the cleaning blades 150 and 170 once every 15 times.

FIG. 7 is a basic configuration diagram of a sixth example of the image forming apparatus 600 according to the embodiment of the present invention.
FIG. 14 is a diagram for explaining the operation 1 of the sixth example of the image forming apparatus 600 according to the embodiment of the present invention.
FIG. 15 is a diagram for explaining the operation 2 of the sixth example of the image forming apparatus 600 according to the embodiment of the present invention.
7, 14, and 15, the image forming apparatus 600 is counterclockwise in the direction indicated by the arrow (C) at a position facing the intermediate transfer belt of the intermediate transfer body 20 that is the second image carrier 2. Four first image carriers 1 rotating in the rotation direction are arranged. The four first image carriers 1 are arranged in parallel in a black image forming unit 11, a yellow image forming unit 12, a cyan image forming unit 13, and a magenta (M) image forming unit 14.
Around each of the first image carriers 1, a charging device 101, an exposure device 102, a developing device 103, a primary transfer device 140, and a cleaning device 105 are sequentially arranged. By these devices, the toner image is formed on the intermediate transfer member 20 of the intermediate transfer belt by performing the charging, exposure, development, transfer, and cleaning processes on the photosensitive drum of each first image carrier 1. It is formed.

The developing devices 103 of the black image forming unit 11, the yellow image forming unit 12, the cyan image forming unit 13, and the magenta image forming unit 14 are filled with K, Y, C, and M developers, respectively. On each first image carrier 1, toner images of K, Y, C, and M are formed. Each developing device 103 includes a toner replenishing device 130 for replenishing each toner into each developing device 103. The toner image formed on the intermediate transfer member 20 of the second image carrier 2 moving in the clockwise direction of the arrow (D) shown in the figure is transferred onto the recording medium (P) by the secondary transfer device 141. Transcribed.
Subsequently, the toner image transferred onto the recording medium (P) is conveyed to the fixing device 106 by the conveying belt 22 that moves in the counterclockwise direction indicated by the arrow (E) in the figure, and is fixed.
The transfer residual toner on the first image carrier 1 after the primary transfer is transferred to the residual toner on the intermediate transfer body 20 of the second image carrier 2 after the secondary transfer by each cleaning device 105. Are cleaned by the belt cleaning device 107. This operation is continuously performed to form a recorded image on one or a plurality of recording media (P) transfer paper.

Further, on the intermediate transfer member 20 of the second image carrier 2, the toner image of the reference pattern 3 on the intermediate transfer member 20 between the most downstream first image carrier 1 and secondary transfer device 141. An image density sensor 41 of the image density detecting means 4 for detecting the image density of the image is arranged.
The image density sensor 41 of the image density detection means 4 is installed in a state that it can be moved in the main scanning direction by the image density detection means moving means 40. Details of a moving mechanism for moving the image density sensor 41 of the image density detecting means 4 by the image density detecting means moving means 40 will be described below with reference to FIG.
The image density sensor 41 of the image density detecting means 4 is slid along the main scanning direction indicated by an arrow (G) in the figure by a guide shaft 46 whose left and right ends are supported by left and right end support plates 45 (left and right). It is supported movably. The image density sensor 41 of the image density detection means 4 is mounted on an endless belt-like density detection means conveyance belt 48 that is rotationally driven by a motor 47. Then, the image density sensor 41 of the image density detection means 4 is moved by the controller 49 in the left-right direction along the main scanning direction indicated by the arrow (G) in the figure by the driving force of the motor 47.
Accordingly, the range from the left end support plate 45 (left) to the right end support plate 45 (right) in FIG. 8 is the movable range (H) of the image density sensor 41 of the image density detection means 4. The image density sensor 41 of the image density detection means 4 is a reference created within this range on the intermediate transfer body 20 of the second image carrier 2 with respect to the main scanning direction indicated by the arrow (G) in the figure. The image density of pattern 3 can be detected.

The toner density control of the developer will be described. The toner replenishing device 130 detects the magnetic permeability of each developer (carrier) by a toner concentration sensor 131 attached to each developing device 103. Each time an image is formed on the recording medium (P), the toner replenishment amount is changed according to the current value of the output value of the toner density sensor 131 with respect to the target value, and the toner density of the developer is controlled to be constant. Yes.
However, the developing ability of the developer changes as the charging ability changes due to environmental changes, deterioration with time, and the like, and as a result, the image density changes under a constant imaging condition.
For this reason, the image density adjusting means 5 uses the reference pattern 3 created at a position corresponding to the recording medium (P) on the second image carrier 2 of the intermediate transfer body 20 in order to keep the image density constant. The image density is detected by the image density detection means 4.
The image density adjusting means 5 detects the image density of the reference pattern 3 by the image density sensor 41 of the image density detecting means 4 and feeds back to the toner density control so that the image density approaches the target value by the output. When it is determined that the current image density is higher than the target image density value, the toner density is set to be low, and when it is determined to be light, the toner is supplied by setting it high. As a result, the image density is controlled to be constant.

The target value for detection of the reference pattern 3 and toner density control will be described with reference to FIG. One reference pattern 3 is created for each sheet of transfer paper on the recording medium (P). The sizes of the reference patterns 3 are all a length a (for example, 10 mm) in the main scanning direction and a length d (for example, 15 mm) in the sub-scanning direction. K between 4n + 1 sheets, Y between 4n + 2 sheets, C between 4n + 3 sheets, and M between 4 (n + 1) sheets. In this manner, one reference pattern 3 is created for each interval between transfer sheets of the recording medium (P), and the image density is detected.
When the image density of the reference pattern 3 of K toner between the sheets after the 4n + 1th sheet is higher / lower than the target image density, the target is set so that the toner density of the developer in the black image forming unit 11 becomes lower / higher. Toner density Tk (n) is set. From 4n + 2 to 4 (n + 1) + 1st sheet, an appropriate amount of K toner is supplied to the developing device 103 of the black image forming unit 11 with Tk (n) as a target value.
When the image density of the reference pattern 3 of Y toner between the sheets after 4n + 2 sheets is higher / lower than the target image density, the target is set so that the toner density of the developer in the yellow image forming unit 12 is lower / higher. Toner density Ty (n) is set. From 4n + 3 to 4 (n + 1) + 2nd sheet, an appropriate amount of Y toner is supplied to the developing device 103 of the yellow image forming unit 12 with Ty (n) as a target value.

When the image density of the reference pattern 3 of C toner between the sheets after the 4n + 3rd sheet is higher / lower than the target image density, the target is set so that the toner density of the developer in the cyan image forming unit 13 is lower / higher. Toner density Tc (n) is set. From 4 (n + 1) to 4 (n + 1) + 3rd sheet, an appropriate amount of C toner is supplied to the developing device 103 of the cyan image forming unit 13 with Tc (n) as a target value.
When the image density of the M toner reference pattern 3 between the sheets after the 4th (n + 1) th sheet is higher / lower than the target image density, the toner density of the developer in the magenta image forming unit 14 becomes lower / higher. In this way, the target toner density Tm (n) is set. From the 4th (n + 1) +1 to the 4th (n + 2) th sheet, an appropriate amount of M toner is supplied to the developing device 103 of the magenta image forming unit 14 with Tm (n) as a target value.

The cleaning of the reference pattern 3 will be described. Each reference pattern 3 moves together with the second image carrier 2 of the intermediate transfer body 20 after the image density is detected by the image density sensor 41 of the image density detection means 4. As it is, it enters the secondary transfer nip, that is, the portion where the intermediate transfer member 20 of the second image carrier 2 and the secondary transfer roller of the secondary transfer device 141 come into contact with each other.
In the secondary transfer nip, no transfer bias is applied to the secondary transfer roller of the secondary transfer device 141 when the reference pattern 3 at a position corresponding to the recording medium (P) passes. Therefore, most of the toner image of the reference pattern 3 remains on the second image carrier 2 of the intermediate transfer body 20 as it is.
Then, cleaning is performed by the belt cleaning device 107. Further, part of the black and color toner images of the reference pattern 3 are transferred onto the secondary transfer roller of the secondary transfer device 141 and cleaned by the secondary transfer cleaning device 142.

A moving sequence of the position of the reference pattern 3 in the image forming apparatus 600 and the image density detection position of the image density sensor 41 of the image density detection unit 4 will be described with reference to FIG.
In the above configuration, in the image forming apparatus 600, the next reference pattern 3 is created at a position a distance amm, for example, 10 mm away from the position previously created with respect to the main scanning direction indicated by the arrow (G) in the figure. Create
First, when the power is turned on, the control unit 49 drives the motor 47 to move the image density sensor 41 of the image density detection means 4 to HP (home position).
A K reference pattern 3 is formed at a position opposite to P1 on the intermediate transfer body 20 of the second image carrier 2 between the first and second sheets of transfer paper of the recording medium (P). Detect concentration.
During the image forming operation of the second sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the drawing, and stops at a position P2 that is a distance a (10 mm) away from P1. . A Y reference pattern 3 is formed at a position opposite to P2 on the intermediate transfer body 20 of the second image carrier 2 between the second and second sheets of transfer paper on the recording medium (P). Detect concentration.

During the image forming operation of the third sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and stops at a position P3 that is a distance a (10 mm) away from P2. . A C reference pattern 3 is formed at a position facing P3 on the intermediate transfer body 20 of the second image carrier 2 between the third sheet of transfer paper of the recording medium (P), and the image is formed. Detect concentration.
During the image forming operation of the fourth sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and stops at a position P4 that is a distance a (10 mm) away from P3. . An M reference pattern 3 is formed at a position opposite to P4 on the intermediate transfer body 20 of the second image carrier 2 between the fourth and subsequent sheets of transfer paper on the recording medium (P), and the image Detect concentration.
During the image forming operation for the fifth sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and stops at a position P5 that is a distance a (10 mm) away from P4. . The K (black) reference pattern 3 is formed at a position opposite to P5 on the intermediate transfer body 20 of the second image carrier 2 between the fifth and subsequent sheets of the transfer paper of the recording medium (P). Then, the image density is detected.

Similarly, during the (4n + 1) -th image forming operation, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and the distance a (10 mm) from P (4n). It stops at a position P (4n + 1) that is far away. Between the (4n + 1) th sheets of transfer paper on the recording medium (P), the K reference pattern 3 is positioned at a position facing P (4n + 1) on the intermediate transfer body 20 of the second image carrier 2. Create an image and detect the image density.
During the (4n + 2) -th image forming operation, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and is separated from P (4n + 1) by a distance a (10 mm). Stop at position P (4n + 2). Between the (4n + 2) th sheet of transfer paper on the recording medium (P), the Y reference pattern 3 is positioned at a position facing P (4n + 2) on the intermediate transfer body 20 of the second image carrier 2. Create an image and detect the image density.
During the (4n + 3) -th image forming operation, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and is separated from P (4n + 2) by a distance a (10 mm). Stop at position P (4n + 3). Between the (4n + 3) th sheet of transfer paper on the recording medium (P), the C reference pattern 3 is positioned at a position facing P (4n + 3) on the intermediate transfer body 20 of the second image carrier 2. Create an image and detect the image density.

During the image forming operation for the 4th (n + 1) th sheet, the motor 47 is driven to move the image density sensor 41 in the main scanning direction in the direction of the arrow (G) shown in the figure and away from P (4n + 3) by a distance a (100 mm). Stops at the position P (4 (n + 1)). Between the (4 (n + 1)) th sheet of transfer paper of the recording medium (P), the M reference pattern 3 is transferred to P (4 (n + 1)) on the intermediate transfer body 20 of the second image carrier 2. ) To detect the image density.
During the 4 (n + 1) + 1-th image forming operation, the motor 47 is driven to move the image density sensor 41 in the main scanning direction indicated by the arrow (G) in the figure, and the distance a (from P (4 (n + 1)) It stops at a position P (4 (n + 1) +1) separated by 10 mm). Between the (4 (n + 1) +1) th sheets of transfer paper of the recording medium (P), the K reference pattern 3 is transferred to P (4 (n + 1) on the intermediate transfer body 20 of the second image carrier 2. ) Image is formed at a position opposite to +1), and the image density is detected.

As described above, the image formation position of the repeated reference pattern 3 and the image density detection position of the image density sensor 41 are changed as a set. If this repetition is continued, the reference pattern 3 and the image density sensor 41 will exceed one end of the movable range (H) of the image density sensor 41. Processing in this case will be described with reference to FIG.
Assume that the K reference pattern 3 is detected at the position P (m) at the mth time. In the (m + 1) th time, the Y reference pattern 3 is detected at a position separated by a distance a (10 mm) from the position P (m). This position is one end of the movable range (H) of the image density sensor 41. Will be exceeded. Therefore, the position returns to the position P (m + 1) separated by the distance a (10 mm) in the direction opposite to the direction in which the reference pattern 3 has moved from the position P (m), and the Y of the (m + 1) th reference pattern 3 is returned at that position. Image density detection is performed.
After that, the next reference pattern 3 is created at a position away from the previously created position by the distance a (10 mm) with respect to the main scanning direction indicated by the arrow (G) in the figure. Repeat the sequence. When the image density sensor 41 again exceeds one end of the movable range (H), the image density sensor 41 is folded in the forward direction. This operation is repeated.

As described above, by repeatedly changing the image formation position of the reference pattern 3 and the image density detection position of the image density sensor 41 as a set, the toner image of the reference pattern 3 input to each cleaning device is at the same position every time. There is no input and the rate is once every m times. For example, when the moving distance a is 10 mm and the movable width of the image density sensor 41 is 300 mm, the reference pattern 3 is input to the cleaning blades 150 and 170 once every 30 times.
Accordingly, the image forming apparatuses 100 to 600 can input the reference pattern 3 evenly over the image width in the main scanning direction, thereby eliminating the wear of the cleaning blades 150 and 170 at specific positions and extending the replacement cycle. . In the electrophotographic image forming apparatus that creates the reference pattern 3 and adjusts the image density, it is possible to prevent defective cleaning and extend the life of the cleaning device 105 and the belt cleaning device 107. Even if the reference pattern 3 reaches the end of the movable range (H) of the image density detecting means 4, the next image density can be detected continuously. Further, in the intermediate transfer method and the direct transfer method, it is possible to prevent defective cleaning, extend the life of the cleaning device, and form a high-quality image.

1 is a basic configuration diagram of a first example of an image forming apparatus according to an embodiment of the present invention; FIG. 3 is a diagram illustrating a position where a reference pattern for image density adjustment is created in the first example of the image forming apparatus according to the embodiment of the present invention. It is a basic composition figure of the 2nd example of the image forming device concerning the embodiment of the present invention. It is a figure which shows the production position of the reference pattern for image density adjustment of 2nd Example of the image forming apparatus concerning embodiment of this invention. It is a basic composition figure of the 3rd example of the image forming device concerning the embodiment of the present invention. It is a figure which shows the production position of the reference pattern for image density adjustment of 3rd Example of the image forming apparatus concerning embodiment of this invention. FIG. 6 is a basic configuration diagram of fourth and sixth examples of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a basic configuration diagram of an image density detection unit moving unit of the image forming apparatus according to the embodiment of the present invention. FIG. 5 is a diagram for explaining reference pattern detection timing and toner density target value update timing of the image forming apparatus according to the embodiment of the present invention. It is a figure explaining operation | movement of the 4th Example of the image forming apparatus concerning embodiment of this invention. FIG. 10 is a basic configuration diagram of a fifth example of the image forming apparatus according to the embodiment of the present invention; It is a figure explaining the operation | movement 1 of the 5th Example of the image forming apparatus concerning embodiment of this invention. It is a figure explaining the operation | movement 2 of the 5th Example of the image forming apparatus concerning embodiment of this invention. It is a figure explaining the operation | movement 1st of the 6th Example of the image forming apparatus concerning embodiment of this invention. It is a figure explaining the operation | movement 2 of the 6th Example of the image forming apparatus concerning embodiment of this invention. It is a figure which shows the state of the edge part of the reference pattern for image density adjustment produced in the conventional image forming apparatus. It is a figure which shows the creation position of the reference pattern for image density adjustment in the conventional image forming apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... 1st image carrier, 2 ... 2nd image carrier, 3 ... Reference pattern, 4 ... Image density detection means, 5 ... Image density adjustment means, 10 ... Image formation part, 11 ... Black image formation part, DESCRIPTION OF SYMBOLS 12 ... Yellow image formation part, 13 ... Cyan image formation part, 14 ... Magenta image formation part, 20 ... Intermediate transfer body, 21 ... Recording medium conveyance means, 22 ... Conveyance belt, 40 ... Image density detection means movement means, 41 42, 43, 44 ... Image density sensor, 45 (left, right) ... Left and right end support plates, 46 ... Guide shaft, 47 ... Motor, 48 ... Concentration detection means conveying belt, 49 ... Control unit, 100 ... Image forming apparatus DESCRIPTION OF SYMBOLS 101 ... Charging device 102 ... Exposure device 103 ... Development device 104 ... Transfer device 105 ... Cleaning device 106 ... Fixing device 107 ... Belt cleaning device 130 ... Toner replenishing device 131 ... Toner density sensor 40 ... first transfer device, 141 ... secondary transfer device 142 ... secondary transfer cleaning device, 150 ... cleaning blade 170 ... cleaning blade, 200,300,400,500,600 ... image forming apparatus, 1003 ... reference pattern

Claims (15)

  In an image forming apparatus for forming a recorded image by adjusting an image density with a reference pattern to be created, a first image carrier that carries a recorded image that is formed rotatably and the first image carrier A second image carrier that holds the recording image transferred from the body and is rotatably held, and the first image carrier on the second image carrier in the main scanning direction of the recording image On the other hand, a reference pattern for image density adjustment which is sequentially formed and transferred at a position different from the previously created position, and an image density detection means for detecting the optical density of the reference pattern on the second image carrier. An image forming apparatus comprising image density adjusting means for adjusting an image density of a recorded image formed based on a detection result of the image density detecting means.   The image forming apparatus according to claim 1, further comprising a plurality of image forming units each including the first image carrier.   The image forming apparatus according to claim 2, wherein the image forming unit includes a black image forming unit and a plurality of color image forming units.   The image forming apparatus according to claim 1, wherein the second image carrier includes an intermediate transfer member.   The image forming apparatus according to claim 1, wherein the second image carrier includes a recording medium conveying unit.   6. The image forming apparatus according to claim 1, wherein the reference pattern includes a color toner.   The image forming apparatus according to claim 1, wherein the reference pattern is formed and transferred at a position away from a previously created position by a predetermined distance. apparatus.   8. The image forming apparatus according to claim 1, wherein the reference pattern is formed and transferred at a position separated from a previously created position by a predetermined length in the main scanning direction of the reference pattern. And an image forming apparatus.   9. The image forming apparatus according to claim 1, wherein the reference pattern is formed when a position to be formed and transferred next time is out of an optical density detection range of the image density detection unit. An image forming apparatus comprising: forming and transferring the next reference pattern at a position on the other end side of the optical density detectable range of the image density detecting means.   9. The image forming apparatus according to claim 1, wherein the reference pattern is folded when a position to be formed and transferred next time is outside an optical density detection range of the image density detection unit. An image forming apparatus comprising: forming and transferring the next reference pattern at a position separated by a predetermined distance in the direction.   11. The image forming apparatus according to claim 1, wherein the image density detecting unit includes a plurality of image density sensors.   12. The image forming apparatus according to claim 1, wherein the image density detecting means includes a plurality of image density sensors for black and color toner.   13. The image forming apparatus according to claim 1, wherein the image density detecting unit includes an image density detecting unit moving unit that moves along a surface of the second image carrier. A featured image forming apparatus.   The image forming apparatus according to claim 1, wherein the toner has an average particle diameter of 6 μm or less.   15. The image forming apparatus according to claim 1, wherein the toner has a shape factor (SF-1) representing a degree of sphere of 150 or less.

Images