JPH07181795A - Image density detecting device - Google Patents

Abstract

PURPOSE:To surely discharge an ADC patch part prior to the formation of a toner image for detecting an image density. CONSTITUTION:A image density detecting reference pattern 16 (ADC patch) is transferred to the paper sheet 15 of a transfer material carrier and the interimage of the paper sheet 15, a transmitted light quantity is measured by a density detector arranged on the downstream side of carrying, to detect the density of a transferred toner image. A means for shifting the ADC patch from a position where the previous toner image for detecting the image density is formed in the axial direction of an image carrier or the direction of processing or changing the patch part itself by the cycle of the transfer carrier or so, so that the ADC patch is not continuously transferred to the same position of the patch part, that is, a region not sufficiently discharged is selectively used, to adjust the density of a color image with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tandem system in which an electrostatic latent image formed on an image carrier is developed with toner and the visualized toner image is directly transferred to a transfer material on the transfer material carrier. In particular, the present invention relates to an image density detection device in an image forming apparatus such as an image density detection device, and particularly, to accurately detect a density by a density detection toner image (hereinafter referred to as an ADC patch) transferred to an intermediate transfer member or a transfer holding member (hereinafter referred to as a transfer material carrier) The present invention relates to an image density detection device suitable for frequent execution.

[0002]

2. Description of the Related Art In an image forming apparatus for forming a color image, in order to stabilize color tone reproducibility, it is necessary to accurately control the image density of each toner color used. Therefore, as the control method, some methods have been conventionally used. Here, a method of transferring a toner image onto a transfer material carrying member or an intermediate transfer member and detecting the density thereof will be described.

As a first method, there is known a method in which a light receiving element has a structure for detecting specular reflection light of a light emitted from a light emitting element in a toner image. In this case, when the density of the toner image to be detected becomes large, there is a drawback that the error starts to be influenced by irregularly reflected light by the toner itself, and the toner cannot be accurately detected.

As a second method, there is a method of detecting the amount of transmitted light of a toner image by light emitting / receiving elements arranged inside and outside the transfer material carrier (Japanese Patent Laid-Open No. 3-1745).
60). In this method, even in the case of a color toner image, it can be accurately detected even if the toner image density becomes large. In addition, JP-A-1-161384 and JP-A-2-1080
86, A disclosed in JP-A-3-226778, etc.
There is one that changes the creation cycle of the DC batch.

[0005]

However, in the embodiment disclosed in Japanese Patent Laid-Open No. 3-174560, the amount of transmitted light of the toner image is not detected in parallel with the image formation, and the detection timing is when the power is turned on. When the number of formed images reaches a predetermined number, it is assumed that the operation is artificial. Then, the developing conditions are changed and controlled so that the detected reference toner image density becomes constant. This is sequentially repeated for each color of yellow, magenta, cyan, and black. This not only does not allow accurate detection with high sensitivity because the transmission type cannot always be detected during normal image formation, but also the maintenance of the density during normal image formation is achieved by the toner density sensor in the conventional developing machine. A method for keeping the toner concentration of the agent constant must be taken. Further, when a plurality of developing machines are not required as in the color image forming apparatus, a toner density sensor is required for each of them, which leads to an increase in cost.

Further, the conventional method of changing the cycle of creating the ADC batch is to improve the instability of the density in the toner supply, and the AD depending on how the charge is removed from the ADC batch section.
Instability of C-batch concentration cannot be improved. Further, in FIG. 1, in the case where the transfer belt charge eliminator 12 is located upstream of the transfer belt cleaner 13, if the ADC batch 16 is continuously created at the same position on the transfer belt 9, the charge removal of the ADC batch portion of the transfer belt is performed. Is performed with toner on the transfer belt. Therefore, the charge removal is not normally performed, and the residual potential of the ADC batch portion on the transfer belt is partially increased. If the ADC batch is continuously created at this position, the transfer of the ADC batch from the image carrier to the transfer belt after the second cycle (second lap) of the transfer belt is not normally performed, and the ADC batch on the transfer belt is not performed. Uneven density occurs. Therefore, there is a problem that the value at the time of detecting the concentration fluctuates or shifts, and the correct concentration cannot be measured.

SUMMARY OF THE INVENTION An object of the present invention is to provide an image density detecting device in which the charge of the ADC patch portion is always removed prior to the formation of a toner image for image density detection. Another object of the present invention is to provide an image density detecting apparatus which can always detect the amount of transmitted light of a toner image for image density detection during normal image formation and can detect it with high accuracy.

[0008]

In order to achieve the above-mentioned object, the present invention develops an electrostatic latent image formed on an image bearing member with a toner, and the toner image visualized thereby is carried on a transfer material. In an image forming apparatus that transfers to a transfer material on a body, a toner image for detecting an image density of an engine that forms a color image is transferred to a transfer material carrier, and the toner image is detected by an optical sensor. The apparatus is provided with a means for shifting the toner image for image density detection for each color with respect to the axial direction of the image carrier to create a gap between the transfer material on the transfer material carrier and the transfer material. In the configuration.

Another invention is characterized in that, in the invention described in claim 1, any one of the following configurations is provided. That is, (1) the optical sensor is arranged inside and outside of the transfer material carrier, and is composed of a light emitting element section for irradiating a toner image for density detection of each engine and a light receiving element section for detection, and the element sections are provided in an integrated housing. It is in a stored configuration. (2) In the case where a seam is present on the transfer material carrier, the image density detecting toner image is not formed in the gap between the transfer material on the transfer material carrier having seams. It is in. (3) The transfer material carrier is composed of a transfer belt, and when a number of images (a is a natural number) per one rotation of the transfer belt are created, the patch is created at a cycle other than about a few sheets of a. In the configuration. (4) The transfer material carrier is composed of a transfer belt, and when a number of images (a is a natural number) per one rotation of the transfer belt are to be formed, the patch should be formed at a cycle of a minimum value other than about several sheets of a. It is configured to do. (5) When the transfer material carrier is composed of a transfer belt and a number of images (a is a natural number) per one revolution of the transfer belt are created, odd-numbered cycles and even-numbered cycles of the transfer belt are even numbers. , Or odd-numbered cycles, even-numbered sheets and even-numbered cycles, odd-numbered sheets, respectively. (6) The transfer material carrier is composed of a transfer belt, and the patch forming position is changed in the process direction within the same patch forming area for each circumference of the transfer belt. (7) The transfer material carrier is composed of a transfer belt, and the patch formation position is changed in the axial direction of the photoconductor in the same patch formation region for each circumference of the transfer belt. (8) The static eliminator of the transfer carrier is arranged on the downstream side or both the upstream side and the downstream side of the cleaner for cleaning the transfer carrier.

[0010]

According to the first aspect of the present invention, the toner image for detecting the image density of the engine for forming a color image is shifted with respect to the axial direction of the image carrier and transferred to the transfer material on the transfer material carrier. By creating between the material (patch part),
It is possible to accurately adjust the color image density. Preferably, the toner image for detecting the image density is formed at the same position on the patch portion,
In other words, in order to prevent subsequent transfer to the area where the charge is not sufficiently removed, the position of the toner image for detecting the image density is shifted in the axial direction of the image carrier or in the process direction, or the patch itself is transferred. Means such as changing depending on the belt cycle can be selected and used.
Preferably, in order to surely perform static elimination and cleaning, by appropriately selecting the arrangement and the number of static eliminators of the transfer material carrier with respect to the cleaner of the transfer material carrier,
The required image density detecting toner image can be transferred onto the transfer material carrier. In addition, since the light emitting part and the light receiving part of the optical sensor are housed in a single housing, even if the transfer material carrier module is detached due to paper jam or the like, the amount of received light does not change before and after the transfer material carrier module, so there is variation in the detected value. Less. An optical sensor is preferably located after the final engine. Further, since the patch is formed while avoiding the seam of the transfer material carrier, the cleaning property of the transfer material carrier can be stably maintained.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows a color copying machine to which the present invention is applied. In this embodiment, the charging device, the exposure device, the developing device,
A xerographic module including a transfer device, a cleaner, a charge removing device, and a photosensitive drum as one unit will be referred to as an engine or xerographic engine. The original placed on the original glass (not shown) is exposed to the CCD by the exposure lamp.
The sensor is exposed. The read image signal is passed through an image processing unit (not shown), and each color (K, Y, M, C)
Image processing is performed for each. This processed color image signal is applied to the image forming laser optical system of the K, Y, M, and C engines. Each engine depends on its engine interval,
Similar operations are performed with a timing shift.

First, in the K engine, the photosensitive drum 5 charged by the charging corotron 1 is exposed by the image forming laser beam 2 to form an electrostatic latent image, and the electrostatic latent image is toner by the developing device 4. Become a statue. The toner image formed on the photosensitive drum 5 is transferred to the position of the transfer corotron 6 on the transfer material carrier 9. On the other hand, the transfer material (hereinafter referred to as paper) is supplied from a paper feed cassette (not shown), adsorbed and held by the transfer material carrier 9, and transferred to the position of the transfer corotron 6. Then, the formed toner image is transferred onto the paper by the corotron 6.

The photosensitive drum 5 after the transfer is cleaned by a cleaner 7 and discharged by a discharge lamp 8. Y,
The same operation is performed in the M and C engines, and the toner image is transferred onto the paper. After that, it passes through the peeling corotron 11 and is transferred and fixed to a fixing device (not shown).
The reference for matching the timing of the sheet transfer and the timing of forming the toner image on the photosensitive drum 5 is the registration adjusting sheet transport roll 14 (hereinafter referred to as a registration roll) provided between the sheet cassette and the transfer material carrier 9. The drive start signal of (Note) is used.

(First Embodiment) Simultaneously with the image forming operation described above, exposure is performed by the image forming laser beam 2 on the basis of the driving start signal of the registration roll 14, an electrostatic latent image is formed, and the developing device 4 is formed. As shown in FIG. 2, the image density detection reference pattern 16 (hereinafter referred to as an ADC patch) which has become a toner image by the paper 15 and the paper 15 of the transfer material carrier 9 are formed.
Is transferred onto the transfer material carrier 9. This ADC patch 16 is
A density detector (light emitting section) 10-2 arranged inside and outside the transfer material carrier 9 measures the amount of transmitted light to detect the density of the transferred toner image.

At this time, the ADC patch 16 is formed so as to be shifted in the axial direction of the photosensitive drum 5 so as not to overlap on the transfer material carrier 9. 16-K is created by the K engine, and similarly, 16-Y, 16-M, and 16-C are created by the Y, M, and C engines, respectively. Here, the image formation timing of the image density detection reference pattern is
Although it is based on the drive start signal that conveys the paper,
The writing start signal of the image forming laser beam of the first engine may be used as a reference.

FIG. 3 shows the structure of the concentration detector. See also FIG.
Indicates the arrangement of the concentration detector. In FIG. 3, a concentration detector (light emitting unit) 10-1 and a concentration detector (light receiving unit) 10-
2 is an ADC for detecting K, Y, M, C image density
The light-emitting elements / light-receiving elements for K, Y, M, and C are housed in respective integral housings so as to coincide with the centers of the patches 16-K, Y, M, and C in the axial direction. The light emitting element portion is attached to a portion where the axial position of the image forming apparatus main body is defined, and the light receiving element portion is attached to the transfer material carrier module. That is, when the transfer material carrier module is pulled out due to paper jam or the like, the light receiving element portion is also pulled out, and the optical axis of the light emitting element / light receiving element is displaced each time.

Therefore, in the present invention, the optical axis shift due to the attachment / detachment of the transfer material carrier module, the optical axis shift due to the mounting error of the light emitting element housing and the light receiving element housing,
As shown in FIG. 4, in order to prevent the sensitivity to the transferred toner image density from fluctuating due to the deviation of the optical axis due to the slit position of the light emitting element / light receiving element in the housing and the mounting error of the element, as shown in FIG. The mounting position in the height direction is far from the transfer carrier, and specifically, the distance a between the detection surface of the light emitting element section and the transfer material carrier is 7 to 10 mm.
By setting the diameter of the light emitting element slit 20-1 to about 3 mm, the amount of light entering the light receiving element does not fluctuate. Further, the housing 10-2 of the light receiving element portion is mounted so that the distance b between the housing 10-2 and the transfer material carrying member 9 is brought close to 0.3 to 1.0 mm so as to increase the detection sensitivity without picking up irregular reflection of toner. ing. Also, the light emission for each engine /
The distance between the light receiving elements is set sufficiently in the axial direction of the photosensitive drum 5 so that the mutually emitted lights are not affected.

In FIG. 5, the distance b from the transfer material carrier 9 is 0.7.
When the distance a between the detection surface of the light emitting element and the transfer material carrier is changed by 5 mm to 10 mm, the latitude for the deviation of the optical density of the transferred toner image density detection sensitivity (allowable range ± 3%) is determined. Shows. As is apparent from FIG. 5, when the distance a = 7 mm, the total optical axis deviation can be allowed up to 1.9 mm. Since the optical axis shift in the actual image forming apparatus is 1.5 mm or less including the optical axis shift due to the attachment / detachment of the transfer material carrier module, the problem of the detection sensitivity variation can be solved by the above configuration. I understand. In this embodiment, a hole (not shown) for position detection is provided in the transfer material carrier so that the position of the seam of the transfer material carrier can always be stored. That is, A
When the DC patch 16 and the seam do not overlap, the image for the ADC patch 16 is not written. As a result, the cleaning failure of the transfer material carrier at the seam portion does not occur.

(Second Embodiment) This embodiment is characterized by the position and interval at which the ADC patch is created. FIG. 6 shows the relationship between the division number of the transfer belt and the ADC patch formation interval. A sheet per rotation of the transfer belt (a sheet
Is a natural number) will be described. (1) In the case where ADC patches are created in a cycle other than about several sheets of a, the ADC patch creation interval shown in the middle column of FIG. 6 is applied (Specific Example 1). By creating the ADC patch at this interval, it is possible to realize that the ADC patch is not created twice in the same place on the transfer belt. At such a position, A
By creating a DC patch, the ADC patch is not created twice at the same place on the transfer belt.
Prior to the creation of the DC patch, the ADC patch section can always be destaticized. As a result, the transfer from the photosensitive drum onto the transfer material carrier is performed in a stable state, and the ADC
The density of the patch can be accurately detected, and the stable density can always be maintained during image formation.

(2) A in the cycle of the minimum value other than about several sheets of a
In the case of creating a DC patch, the shortest interval is applied in a cycle other than about several sheets of a shown in the right column of FIG. 6 (concrete example 2). By performing the ADC patch formation at this interval, in addition to the improvement effect of the first specific example, the concentration detection is performed at the shortest interval, and a more stable concentration can be maintained. Further, even when the number of divisions of the transfer belt is changed by changing the paper size or the like, the ADC patch creation interval can be changed within the range satisfying the conditions of the first specific example or the second specific example. As an example, when the paper size is A3, divide the transfer belt into 5
In the case of, when the transfer belt is divided into 10 parts, A3 is ADC once every two sheets, and A4 is ADC once every three sheets.
Create a patch.

(3) The odd number of the transfer belt is the odd number, the even number is the even number, the odd number is the even number, and the even number is the odd number.
A DC patch is created (specific example 3). FIG. 7 shows an example in which the number of divisions is 5, and only the transfer material carrier 9 and the ADC patch 16 are extracted. In FIG. 7, in the first cycle, the first sheet 16-K, Y, M, C-1, the third sheet 16-
K, Y, M, C-3, 5th sheet 16-K, Y, M, C-5
The ADC patch is created at the position of, and in the second cycle, the second sheet 16-K, Y, M, C-2, the fourth sheet 16-K, Y, M,
Create an ADC patch at position C-4. And so on
1st, 3rd, 5th sheets in 3rd cycle, 2nd, 4th in 4th cycle
An ADC patch is created at the position of the first sheet.

Alternatively, in the first cycle, the second sheet 16-K,
Y, M, C-2, 4th sheet 16-K, Y, M, C-4 ADC patch is created at the position, the second cycle is the first sheet 16
-K, Y, M, C-1, 3rd sheet 16-K, Y, M, C-
ADC patches are created at the positions of the third and fifth sheets 16-K, Y, M, and C-5, and ADC patches are created at the same positions thereafter. Here, FIG. 8 is an example of division numbers 1 to 5, and shows the division number of the transfer belt and the positional relationship between the odd-numbered and even-numbered ADC patches. By adopting the configuration of the above specific example, it is possible to realize that the ADC patch is not formed twice in the same place on the transfer belt.

(4) An ADC patch is created by changing the process direction in the same inter-image for each circumference of the transfer belt (Specific Example 4). 9 to 12 show a transfer belt 1
The relationship between the ADC patch creation positions of the second and second rounds is shown. An ADC patch is created at the position A shown in FIG. 10 on the first round of the transfer belt, and an AD patch is created at the position B shown on FIG. 12 on the second round.
Create a C patch.

(5) An ADC patch is prepared by changing the photosensitive drum in the axial direction in the same inter-image for each circumference of the transfer belt (concrete example 5). 13 to 15 show the relationship between the ADC patch formation positions on the first and second rounds of the transfer belt. On the first turn of the transfer belt, an ADC patch is created at the position A shown in FIG. 14, and on the second turn, the ADC patch is created at the position B. By creating the ADC patch at such a position, the same effect as in the above-described specific example 4 can be obtained.
In addition, in the specific example 5, two sets of ADC sensors are required for each color.

(Third Embodiment) This embodiment is characterized by the arrangement of a transfer belt charge eliminator and a transfer belt cleaner. 16 and 17 show the transfer belt static eliminator 12-
1 shows the relationship between 1 and the transfer belt cooler 13. The transfer belt charge eliminator 12-1 is arranged upstream and / or downstream of the transfer belt cleaner 13. In the example of FIG. 1, the transfer belt charge eliminator 12-1 is arranged on the downstream side of the transfer belt cleaner 13, the downstream side of the example of FIG. 16, and the upstream side and the downstream side of the example of FIG. There is. In the example of FIG. 17, the second transfer belt charge eliminator 12-
It is also possible to make 2 work. According to the above-described embodiment, since the ADC patch portion is always destaticized prior to the ADC patch, the transfer from the photosensitive drum onto the transfer material carrier is performed in a stable state, and the density of the ADC patch is reduced. It can be detected well, and a stable density can always be maintained during image formation.

[0026]

As described above, according to the present invention, the ADC
Since the charge of the ADC patch portion is always removed before the patch is created, the toner image for image density detection is transferred from the image carrier to the transfer material carrier in a stable state and the ADC patch The density can be detected accurately, and a stable density can always be maintained during image formation.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a color copying machine to which the present invention is applied.

FIG. 2 is a diagram illustrating a position where an ADC patch is created.

FIG. 3 is a perspective view showing a configuration of a concentration detector.

FIG. 4 is a layout view of a light emitting element section and a light receiving element section.

FIG. 5 is a diagram showing a latitude with respect to an optical axis shift of a transfer toner image density detection sensitivity variation when a distance between a detection surface of a light emitting element section and a transfer material carrier is changed.

FIG. 6 is a diagram showing the relationship between the number of divisions of the transfer belt and the ADC patch creation interval.

FIG. 7 is a diagram showing a relationship between ADC patch creation intervals when the number of divisions is 5.

FIG. 8 is a diagram for explaining the positional relationship between the number of divisions of the transfer belt in the number of divisions 1 to 5 and the odd and even number of ADC patches.

FIG. 9 is an explanatory diagram of the first round of the transfer belt when the ADC patch creation position is changed in the process direction.

FIG. 10 is a partially enlarged view of FIG.

FIG. 11 is an explanatory diagram of the second round of the transfer belt when the ADC patch creation position is changed in the process direction.

FIG. 12 is a partially enlarged view of FIG. 11.

FIG. 13 is an explanatory diagram of the first round of the transfer belt when the ADC patch creation position is changed in the axial direction.

FIG. 14 is a partially enlarged view of FIG.

FIG. 15 is an explanatory diagram of the second round of the transfer belt when the ADC patch creation position is changed in the axial direction.

16 is a system configuration diagram in which a transfer belt static eliminator 12-1 is arranged on the downstream side of the transfer belt cooler 13. FIG.

FIG. 17 is a system configuration diagram in which transfer belt charge eliminators 12-1 are arranged on the upstream side and the downstream side of the transfer belt cooler 13.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Charging corotron, 2 ... Laser light for image formation, 3 ... Potential sensor, 4 ... Development machine, 5 ... Photosensitive drum, 6 ... Transfer corotron, 7 ... Cleaner, 8 ... Electrification lamp, 9 ... Transfer material carrying body, 10 -1 ... Density detector (light emitting part), 10-2 ... Density detector (light receiving part), 11 ... Peeling corotron, 12 ... Transfer material carrying body static eliminating corotron, 13 ... Transfer material carrying body cleaner, 14 ... Registration adjustment Transfer material transport roll, 15 ... Transfer material (paper), 16 ... Image density detection reference pattern (ADC patch)

Claims (9)

[Claims] 1. An image forming apparatus for transferring a toner image formed on an image carrier to a transfer material on a transfer material carrier,
An image density detecting device for transferring an image density detecting toner image of an engine for forming a color image to the transfer material carrier and detecting the toner image by an optical sensor, wherein the image density detecting toner image for each color is An image density detecting device comprising means for shifting the image carrier axially so as to form a gap between the transfer material on the transfer material carrier and the transfer material. 2. The optical sensor is arranged inside and outside of a transfer material carrier and comprises a light emitting element portion for irradiating a toner image for density detection of each engine and a light receiving element portion for detection, and the element portions are provided in an integral housing. The image density detecting device according to claim 1, wherein the image density detecting device is housed. 3. When the transfer material carrier has a seam, a toner image for image density detection is prevented from being formed in the gap between the transfer material and the transfer material on the transfer material carrier having the seam. The image density detecting apparatus according to claim 1, wherein the image density detecting apparatus is configured. 4. The transfer material carrier comprises a transfer belt, and when a number of images (a is a natural number) per one rotation of the transfer belt are produced, the toner for image density detection is carried out at a cycle other than about a few sheets of a. The image density detecting apparatus according to claim 1, wherein an image is created. 5. The transfer material carrier is composed of a transfer belt, and when a number of images (a is a natural number) per one rotation of the transfer belt are created, the image is transferred at a cycle of a minimum value other than about several sheets of a. The image density detecting device according to claim 1, wherein a toner image for density detection is created. 6. The transfer material carrier is composed of a transfer belt, and when a number of images (a is a natural number) per one revolution of the transfer belt are produced, odd-numbered cycles and even-numbered cycles of the transfer belt are even 2. The image density detecting device according to claim 1, wherein toner images for image density detection are formed on the even numbered sheets of the odd numbered cycles and the even numbered sheets of the odd numbered cycles, respectively. 7. A transfer material carrying member is composed of a transfer belt, and a position where a toner image for detecting image density is formed is arranged in a process direction within a same toner image forming region for detecting image density for each revolution of the transfer belt. The image density detecting device according to claim 1, wherein the image density detecting device is changed. 8. A transfer material carrying member is constituted by a transfer belt, and a position where a toner image for image density detection is formed is set for each rotation of the transfer belt within a same image density detection toner image forming region. The image density detecting device according to claim 1, wherein the image density detecting device is changed in an axial direction. 9. The image density detecting apparatus according to claim 1, wherein the static eliminator of the transfer carrier is arranged on the downstream side or both the upstream side and the downstream side of the cleaner for cleaning the transfer carrier.