JP2001305823A - Color image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image forming device which enables to control stably and constantly the amount of toner adhesion in the best condition unaffected by the environmental changes such as temperature and humidity, the deterioration with time of toner, a photoreceptor, an intermediate transfer unit and the changes of the properties. SOLUTION: The device forms seriatim each color's toner patch P on the different locations of the intermediate transfer unit from the photosensitive unit 1 to the surface of the intermediate transfer unit 10 and is functioned to detect the amount of toner adhesion of each color's toner patch by a toner adhesion sensor 100. The timing of the toner adhesion sensor to detect the amount of toner adhesion of each color's toner patch is set to vary according to the transfer order on the intermediate transfer unit, i.e., the timing to detect the amount of the toner patch's toner adhesion of the transfer order's first color is the slowest and that of the last color is the fastest.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic color image forming apparatus such as a color copying machine, a color printer, a color facsimile apparatus, etc., and more particularly, to an adhesion amount of each color toner image transferred onto an image carrier for each color. The present invention relates to a color image forming apparatus provided with a toner adhesion amount detection function for accurately detecting a toner adhesion amount.

[0002]

2. Description of the Related Art Generally, in a color image forming apparatus, each time toner images of different colors are individually formed on the surface of a photoreceptor, each toner image is superimposed and transferred to the same position on an intermediate transfer member. An image is formed by transferring the upper toner image on a transfer sheet and then fixing it. By the way, in order to keep the image density on the transfer paper constant and good, it is necessary to stabilize the amount of toner adhered to the surface of the photoreceptor. Therefore, the amount of toner adhered to the surface of the photoreceptor is detected by a reflective toner density sensor. There is known a technique for controlling the amount of toner adhesion based on the detection result. Recently, a technique for measuring the amount of diffusely reflected light has been proposed in order to more accurately detect the amount of adhered color toner (for example, Japanese Patent Laid-Open No. 5-249787). That is, when the color toner is irradiated with infrared light, diffuse reflection light is generated. However, since the amount of diffuse reflection light shows a characteristic that increases in accordance with the toner adhesion amount, it can be measured with high sensitivity from a low adhesion amount to a high adhesion amount. it can. In general, a full-color image forming apparatus expresses full-color by superimposing four color toners of cyan, magenta, yellow, and black on transfer paper. For this reason, many methods use a method of forming a superimposed toner image from a photoconductor on an intermediate transfer member. However, even if the toner concentration is controlled by detecting the amount of toner attached to the photoconductor,
Since the toner image is subsequently transferred onto the intermediate transfer member, the transfer rate of the toner image varies due to fluctuations in environmental conditions and the degree of deterioration of the toner, the photoconductor, and the intermediate transfer member, and the toner image is actually transferred onto the transfer paper. The density of the toner image has a value different from the density detected on the photoconductor. Therefore, in order to realize control for stabilizing the amount of toner adhered to the transfer paper, it is necessary to perform detection under conditions where the influence of transfer can be minimized. It is more advantageous to detect the amount of toner attached on the intermediate transfer member.

Conventionally, as shown in FIG. 6, for example, after a toner patch for each color is transferred onto an intermediate transfer member (intermediate transfer belt) at a shifted position, the density of the toner patch of each color is detected immediately after the transfer. Was. That is, when the transferred toner patch first reaches the opposite surface of the toner adhesion amount sensor, the toner adhesion amount is detected. However, when forming a superimposed toner image on the intermediate transfer body, the operation of sequentially superimposing the toners of the four colors is performed. Therefore, the toner image (yellow toner image) having the earliest image forming order is formed on the intermediate transfer body. After the image is transferred, the image is rotated three times while being held on the intermediate transfer member. That is, in the image forming process for three colors, which is performed continuously after the transfer, the toner must be brought into contact with the photoreceptor three times in total, and every time the photoreceptor is contacted, the toner is reversely transferred from the intermediate transfer member to the photoreceptor. Occurs. The amount of reverse transfer varies due to fluctuations in environmental conditions such as temperature and humidity, and the degree of deterioration of the toner, photoconductor, and intermediate transfer body. Therefore, the amount of toner adhered to the transfer paper is stably controlled over time. It has become difficult. For this reason, even when toner patches for each color are formed on the intermediate transfer body and the toner adhesion amount of each toner patch is detected, if the toner adhesion amount of the toner patch immediately after the transfer is detected, the toner adhesion amount is actually determined on the transfer paper. Therefore, a value different from the toner density to be transferred is detected, and the finally obtained image density has a variation.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and relates to environmental fluctuations such as temperature and humidity, deterioration of a toner, a photoreceptor, an intermediate transfer body, and the like with time, and characteristic fluctuations. Another object of the present invention is to provide a color image forming apparatus capable of stably controlling the amount of toner adhered to an optimum state at all times.

[0005]

In order to solve the above-mentioned problems,
According to the first aspect of the present invention, a photoreceptor carrying a toner image and a plurality of color toners are provided on the photoreceptor by supplying toner of a different color for each color in a predetermined order each time the photoreceptor makes one rotation. A developing device that forms a toner image, an intermediate transfer body that carries thereon a toner image of each color sequentially transferred from the photoconductor every time the photoconductor makes one rotation, and a plurality of colors that are superimposed and transferred on the intermediate transfer body. A transfer unit that collectively transfers the toner image onto the transfer material, a toner adhesion amount sensor that detects the amount of toner adhesion of the toner image on the surface of the intermediate transfer body, and a photoconductor based on the toner adhesion amount detected by the toner adhesion sensor. A control unit for determining a correction value of a toner adhesion amount of a toner image to be carried, wherein a toner patch for each color is placed at a different position on the intermediate transfer member from the photosensitive member on the intermediate transfer member. Formed in order, and each color A function of detecting the amount of toner attached to the patch by the toner attachment sensor, and the timing at which the toner attachment sensor detects the amount of toner attached to the toner patch of each color is made different according to the transfer order on the intermediate transfer member. The transfer order is set so that the toner adhesion amount detection timing of the toner patch of the earliest color is the latest and the transfer order is set such that the toner adhesion amount detection timing of the toner patch of the last color is the earliest. Features. According to another aspect of the present invention, a toner image is formed on the photosensitive member by supplying a toner having a plurality of color toners and a different color toner for each color each time the photosensitive member makes one rotation. A developing device, an intermediate transfer member that carries thereon toner images of respective colors sequentially transferred from the photosensitive member each time the photosensitive member makes one rotation, and a transfer material that transfers toner images of a plurality of colors that are overlaid and transferred on the intermediate transfer member. A transfer unit for collectively transferring the toner image onto the intermediate transfer member, a toner adhesion amount sensor for detecting a toner adhesion amount of the toner image on the surface of the intermediate transfer member, and a toner image carried by the photoconductor based on the toner adhesion amount detected by the toner adhesion sensor. A control unit for determining a correction value of the toner adhesion amount, in the color image forming apparatus, a toner patch for each color is sequentially formed on the intermediate transfer body from the photosensitive body at different positions on the intermediate transfer body, Toner patches for each color A function of detecting the adhesion amount by the toner adhesion sensor, wherein the toner adhesion sensor detects the toner adhesion amount for each color toner patch after the transfer of all color toner patches onto the intermediate transfer member is completed. It is characterized by.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a color image forming apparatus according to the present invention will be described in detail with reference to the embodiments shown in the drawings. 1 and 2 are cross-sectional views showing the internal configuration of a color image forming apparatus according to one embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a flexible belt-shaped photoreceptor serving as a belt-shaped image carrier, and the photoreceptor belt 1 is bridged between rotating rollers 2 and 3, The sheet is conveyed in the direction of arrow A (clockwise) by rotation. Reference numeral 4 denotes a charging charger as a charging unit for uniformly charging the surface of the photoreceptor belt 1, reference numeral 5 denotes a laser writing system unit as an electrostatic image exposure unit, and reference numeral 6 denotes yellow, magenta, cyan, and black development described later. This is a rotary type color developing device in which four developing devices each having an agent (toner) are integrally formed. Furthermore,
Reference numeral 10 denotes an intermediate transfer belt, which is an intermediate transfer member. The intermediate transfer belt 10 is bridged between rotating rollers 11 and 12, and is driven by the rotation of the driving side rotating roller 11 in a direction indicated by an arrow B in FIG. Clockwise). The photoreceptor belt 1 and the intermediate transfer belt 10 are in contact with each other at the rotating roller 3 of the photoreceptor belt 1. On the intermediate transfer belt 10 side of the contact portion, a bias roller 13 having conductivity is in contact with the back surface of the intermediate transfer belt 10 under predetermined conditions. Here, an image forming operation of the color image forming apparatus according to the embodiment of the present invention will be described. In FIG. 1, a photoreceptor belt (latent image carrier) 1 is uniformly charged by a charging charger 4,
Scanning exposure is performed based on the image information to form an electrostatic latent image on the surface of the photoreceptor belt. Here, the image information to be exposed is any single-color image information obtained by decomposing a desired full-color image into yellow, cyan, magenta, and black color information, and a semiconductor laser (not shown) uses this image information. The generated laser beam L has been subjected to scanning and optical path adjustment by an optical device (not shown).

The electrostatic latent image formed on the photoreceptor belt 1 is developed in a single color with predetermined yellow, cyan, magenta, and black toners by a rotary developing device 6 described later. Each color image is sequentially formed. Each single-color toner image formed on the photoreceptor belt 1 rotating in the direction of arrow A in the figure is yellow, cyan, and yellow on the intermediate transfer belt 10 rotating in the direction of arrow B in FIG. For each of the single colors of magenta and black, the transfer is sequentially performed by a predetermined transfer bias applied to the bias roller 13. The yellow, cyan, magenta, and black images superimposed on the intermediate transfer belt 10 are fed from a sheet feeding table (sheet feeding cassette) 17 to a sheet feeding roller 18, a pair of conveying rollers 19a and 19b, and a pair of registration rollers 20a and 20.
The transfer roller 14 collectively transfers the transfer paper 17a onto the transfer paper 17a that has been conveyed to the transfer section via the transfer roller 17b. After the transfer, the transfer paper 17
“a” is fixed by the fixing device 80 to complete a full-color image, and the print image is discharged to the discharge stack unit 82 via the discharge roller pairs 81a and 81b. In the figure, 15
Reference numeral denotes a cleaning device that includes a cleaning blade that is always in contact with the photoreceptor belt 1 and cleans toner on the photoreceptor belt 1, and a waste toner collecting device 15c.
Reference numeral 16 denotes a cleaning device for the intermediate transfer belt 10, and the cleaning blade 1 of the cleaning device 16.
6a is held at a position separated from the surface of the intermediate transfer belt 10 during the image forming operation, and the formed image is transferred to the transfer paper 17 described above.
After being transferred onto the surface of the intermediate transfer belt 10, the toner image is contacted. The waste toner scraped off from the intermediate transfer belt 10 by the cleaning blade 16a is conveyed toward the front of the drawing by an auger 16b provided in the cleaning device 16, and further provided on the front side surface of the process cartridge 31, as shown in FIG. The waste toner is conveyed to the waste toner collecting unit 15c by the omitted conveyance unit. The process cartridge 31 is replaced when the waste toner of a predetermined amount or more is stored in the waste toner collecting device 15c.
The service life of the process cartridge 31 is extended. Further, the photoreceptor belt 1, the charging charger 4, the intermediate transfer belt 10, and the cleaning devices 15 and 16 are integrally formed as a process cartridge 31, and the waste toner collecting device 15c is replaceable with the process cartridge 31. Be incorporated. The case exterior portion of the process cartridge 31 on the side of the registration roller 20b also has a function as a paper conveyance guide. Reference numeral 100 denotes a toner adhesion amount sensor for detecting the amount of toner adhesion (density) on the intermediate transfer belt 10. The toner adhesion amount sensor 100 used this time is of a type that uses an infrared light emitting diode as a light emitting unit and a photodiode as a diffuse reflection light receiving unit, and outputs a voltage according to the amount of received light.

Next, the configuration of the image forming apparatus main body according to the embodiment of the present invention will be described with reference to FIG. The apparatus main body structure includes a main body frame 9 as an immovable portion housing, and a front frame 8 as a front housing that can be opened and closed to open a transfer path of the transfer paper 17a.
A paper feed cassette 17 is disposed below the main body frame 9, a color developing device 6 and a process cartridge 31 are replaceably disposed inside the main body, and a fixing device 80 is further disposed above the main body frame 9. , A discharge stack 82 is formed. The front frame 8 is supported to be able to open and close around a rotation support shaft 9 a provided on the main body frame 9,
Normally, as shown in FIG. 1, the main body frame 9 is held in a closed state. When a transfer paper jam occurs in the transfer path of the transfer paper 17a, the front frame lock mechanism (not shown) is released, and the front frame 8 is opened as shown in FIG.
The front frame 8 includes a transport roller 19a, a registration roller 20a, and a transfer roller 1a that constitute a part of the transfer paper transport path.
4 and the like are held, and by opening the front frame 8, the transfer paper transport path is exposed, so that the jam processing can be easily performed. At this time, the other image forming units are stationary, and no problems such as toner scattering and leakage occur. FIG.
Indicates a state in which the toner patch P is formed on the intermediate transfer belt 10. The toner adhesion amount detection patch P formed on the photosensitive belt 1 is transferred onto the intermediate transfer belt at a contact position between the photosensitive belt 1 and the intermediate transfer belt 10, and adheres to the intermediate transfer belt. The state is shown. Amount of toner attached to each toner patch P (toner density)
Is detected by a toner adhesion amount sensor 100 attached opposite to the intermediate transfer belt 10. The operation of detecting the toner adhesion amount of the toner patch is performed in a process control mode that is distinct from the image forming operation, or is performed using an intermediate transfer belt surface corresponding to a space between sheets during the image forming operation. . The number of toner patches to be formed for one color is, for example, 20 to 30 if a 20 to 40 mm square toner patch is formed on an intermediate transfer belt having a total length of about 60 cm. When a plurality of toner patches having different densities and the like are transferred onto the intermediate transfer belt using one color toner, the toner adhesion amount detection unit detects each toner patch during the rotation of the intermediate transfer belt. . In this embodiment, the image forming order is yellow, cyan, magenta, and black. However, if it is not possible to transfer the toner patches of a plurality of colors on the intermediate transfer belt in a state in which the toner patches coexist, a single image is formed. In the adhesion amount detection, the detection is performed by transferring only one color toner patch.

Incidentally, the conventional method for detecting the amount of toner patch adhering, as described with reference to FIG.
After the toner patch P was transferred onto the upper side, the toner patch was detected when it first came to the opposite surface of the toner adhesion amount sensor. However, before the toner image is actually transferred to paper,
In the case of the yellow toner patch, the toner must be rotated while being held on the intermediate transfer belt three times after the transfer, and during this time, it contacts the photosensitive belt 1 three times. Toner 1 reverse transfer occurs. When the cyan toner patch rotates twice after transfer and the magenta toner patch rotates once after transfer, the cyan toner patch comes into contact with the photoconductor, so that reverse transfer occurs. The amount of reverse transfer changes due to environmental fluctuations such as temperature and humidity, and deterioration of the photoconductor, the intermediate transfer belt, and the like. Therefore, it is difficult to stably control the amount of toner adhered to transfer paper over time. . Therefore, as shown in the flow of FIG.
The toner patch P transferred from the photoreceptor belt 1 onto the intermediate transfer belt 10 is applied to the intermediate transfer belt according to the image forming order for the same period (the number of rotations of the intermediate transfer belt) as when an image is actually formed. After holding the toner, the toner adhesion amount is detected. That is, as shown in steps 14 and 15, while the intermediate transfer belt makes three rotations, the amount of toner attached to the yellow toner patch is not detected, and the amount of adhesion is detected at the fourth rotation. The control unit (not shown) compares the detected toner adhesion amount with a preset adhesion amount value, and when the two do not match, calculates a developing bias correction amount and performs a correction corresponding to the correction amount. The yellow toner is supplied (developed) to the photoreceptor belt 1 from the yellow toner developing device at the set developing bias value. As a method of adjusting the toner adhesion amount on the photoconductor, a method of adjusting the photoconductor charging potential or the exposure amount can be used in addition to correcting the developing bias.

When the toner patch P is formed on the intermediate transfer belt 10 as described above, the yellow toner patch is rotated three times on the intermediate transfer belt 10, the cyan toner patch is rotated two times, and the magenta toner patch is rotated. It is apparent that the more accurate detection of the amount of adhered toner becomes possible, the more the amount of adhered toner is detected after the rotation is held for one rotation. When the number of toner patches formed on the intermediate transfer belt 10 for one color toner is large as described above, only one color toner can be detected in one toner adhesion amount detection operation. On the other hand, when the number of toner patches formed on the intermediate transfer belt for one color toner is small, and the toner patches of a plurality of colors can be formed simultaneously on the intermediate transfer belt, the After the toner patches of a plurality of colors that can be formed are formed on the intermediate transfer belt, the attached amount of each toner patch may be detected at once. That is, in Steps 21 to 30, in the special process control mode or in the toner adhesion amount detection mode using the conveyance interval between sheets, the creation of a toner patch on the photosensitive member and the transfer to the intermediate transfer belt are performed. , Yellow toner, cyan toner, magenta toner, and black toner in this order, and after the toner patches of all colors have been transferred,
The procedure for detecting the amount of adhesion for each toner patch is shown. In step 31, as in step 16 in FIG. 4, the control unit compares the detected toner adhesion amount with a preset adhesion amount value. The yellow toner developing unit supplies (develops) the yellow toner from the yellow toner developing device to the photoreceptor belt 1 with the calculated and corrected development bias value corresponding to the correction amount. As a method of adjusting the toner adhesion amount on the photoconductor, a method of adjusting the photoconductor charging potential or the exposure amount can be used in addition to correcting the developing bias. According to this embodiment, the measurement efficiency can be improved and the measurement time can be reduced.

[0011]

As described above, according to the present invention, the amount of adhered toner is always constant irrespective of environmental fluctuations such as temperature and humidity, deterioration of the toner, photoconductor, and intermediate transfer body over time, and characteristic fluctuations. It is possible to stably control to an optimal state. Claim 1
According to the invention, the timing from the transfer of a toner patch composed of a plurality of color toners used for development onto the intermediate transfer member to the detection of the amount of adhesion by a toner adhesion sensor,
The toner adhesion amount is controlled depending on the development order in the actual image forming process, including the variation in the toner adhesion amount due to reverse transfer from the intermediate transfer member to the photosensitive member. For this reason, it is possible to always detect a more accurate amount of adhered toner without being affected by environmental fluctuations, deterioration of the toner, the photoreceptor, the intermediate transfer body, and the like. It is also possible to provide a stable color image forming apparatus free of abnormal images. The invention of claim 2 is
When toner patches of a plurality of colors can be simultaneously formed on the intermediate transfer belt, these densities can be detected simultaneously in one toner amount detection operation, thereby improving measurement efficiency and shortening measurement time. be able to.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an internal configuration of a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a view for explaining another state of FIG. 1;

FIG. 3 is a diagram illustrating a state in which a toner patch is formed on an intermediate transfer member.

FIG. 4 is a flowchart showing a control procedure according to one embodiment of the present invention.

FIG. 5 is a flowchart showing a control procedure according to another embodiment of the present invention.

FIG. 6 is a flowchart illustrating a conventional example.

[Explanation of symbols]

Reference Signs List 1 photoreceptor belt, 2, 3 rotating roller, 4 charger, 5 laser writing system unit, 6 color developing device, 10 intermediate transfer member (intermediate transfer belt), 1
1, 12 rotating roller, 13 bias roller, 100
Toner adhesion amount sensor.

Claims (2)

[Claims] 1. A photoreceptor carrying a toner image and a plurality of toners of a plurality of colors, each time the photoreceptor makes one rotation, supply a different color toner for each color in a predetermined order to supply the toner image onto the photoreceptor. Developing device for forming an image, an intermediate transfer member for carrying thereon a toner image of each color sequentially transferred from the photosensitive member each time the photosensitive member makes one rotation, and a multi-color toner image overlap-transferred on the intermediate transfer member Means for collectively transferring the toner onto the transfer material, a toner adhesion amount sensor for detecting the amount of toner adhesion of the toner image on the surface of the intermediate transfer body, and a photoconductor carried based on the amount of toner adhesion detected by the toner adhesion sensor. A control unit for determining a correction value of a toner adhesion amount of a toner image, wherein a toner patch for each color is sequentially arranged at a different position on the intermediate transfer body from the photosensitive body on the intermediate transfer body. Forming and toner of each color A function of detecting the amount of toner adhered to the toner patch by the toner adhesion sensor. The timing at which the toner adhesion sensor detects the amount of toner adhered to the toner patch of each color is different depending on the transfer order on the intermediate transfer body. The transfer order is set such that the toner adhesion amount detection timing for the toner patch of the earliest color is the latest, and the toner adhesion amount detection timing for the toner patch of the last color is the earliest. A color image forming apparatus. 2. A developing device, comprising: a photosensitive member carrying a toner image; and a plurality of color toners, each of which supplies a different color toner for each rotation of the photosensitive member to form a toner image on the photosensitive member. And an intermediate transfer body that carries toner images of each color sequentially transferred from the photosensitive body every time the photosensitive body makes one rotation,
A transfer unit that collectively transfers a plurality of color toner images superimposedly transferred on the intermediate transfer body onto a transfer material; a toner adhesion amount sensor that detects a toner adhesion amount of the toner image on the surface of the intermediate transfer body;
A control unit for determining a correction value of a toner adhesion amount of a toner image carried by the photoconductor based on the toner adhesion amount detected by the toner adhesion sensor. A toner patch for each color is sequentially formed at different positions on the intermediate transfer member, and a function of detecting the toner adhesion amount of the toner patch of each color by the toner adhesion sensor is provided. A color image forming apparatus comprising: detecting a toner adhesion amount of each color toner patch after the transfer of all color toner patches is completed.