JPH08137267A - Rotation control method of developing sleeve - Google Patents

Abstract

PURPOSE: To prevent a deterioration in image quality by removing a developer stuck to the developing sleeve of a nonused developing unit at the time of impressing a bias voltage, in a developing device for an image forming device which selectively uses one of plural developing units, for developing a latent image on an image carrier. CONSTITUTION: It is judged whether development is attained by the last developing unit used in development order, out of the developing units used or not and when the development is attained by the last developing unit used, it is judged whether a bristle cutting operation in the last developing unit used is completed or not. When the bristle cutting operation is completed, each developing sleeve of all the developing units is reversely rotated, the developer (toner) stuck to the developing sleeve of the nonused developing unit is removed at the time of impressing the bias voltage to the developing sleeve of the developing unit used and then, it is judged whether the developing sleeve is reversely rotated by a specified time or not. Then, the reverse rotation of the developing sleeve is stopped after a lapse of the specified time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention visualizes an electrostatic latent image formed on an image bearing member such as a photoconductor such as a copying machine, a printer or a facsimile, and transfers the visible image onto a sheet. The present invention can be applied to an image forming apparatus that forms an image. Specifically, it can be applied to a developing device that selectively uses one of a plurality of developing devices and develops a latent image on an image carrier. Of which
It can be applied to a type in which a magnet is provided inside the developing sleeve and a developer is attached to the outer periphery of the developing sleeve by the magnet. More specifically, it relates to a rotation control method for a developing sleeve in such a developing device.

[0002]

2. Description of the Related Art Conventionally, in a developing device of, for example, a color laser copying machine, black (Black), blue (Cyan), and red (Magen) are provided around a photoconductor as an image carrier.
There are four (ta) and yellow (Yellow) developing devices arranged in an array.

For example, as shown in FIG. 15, each of such developing devices has a construction in which a developing sleeve 2 is rotatably provided in a developing case 1 and a magnet 3 is fixedly provided in the developing sleeve 2.

During development, the developing sleeve 2 is rotated clockwise in the drawing and the magnet 3 is used to rotate the developing sleeve 2 clockwise.
A developer 4 is attached to the outer periphery of the developing sleeve 2 and is conveyed along with the rotation of the developing sleeve 2, and the attached developer 4 is regulated by a doctor 6, and then a photosensitive member is applied with a bias voltage applied to the developing sleeve 2. No. 5, the residual developer on the developing sleeve 2 after the development was removed by the non-magnetic pole portion 7.

At the end of the development, the developing sleeve 2 is reversed in the counterclockwise direction in the figure contrary to the developing time, the residual developer on the developing sleeve 2 is removed by the non-magnetic pole portion 7, and the developer is cut off. I was going.

However, in such a developing device, after the development is completed, as shown in FIG. 16, the developer 4 remains between the developing case 1 and the developing sleeve 2 at the location indicated by the arrow A. This is because the doctor 6 regulates the developer 4.
Further, the developer 4 also remains between the developing case 1 and the developing sleeve 2 at the location indicated by the arrow B. Since the perpendicular magnetic force is small as can be seen from the magnetic force distribution indicated by the chain double-dashed line, the force for pulling the developer 4 in the axial direction of the developing sleeve 2 is weak,
This is because it is difficult for the developing sleeve 2 to be conveyed when it is reversed.

[0007]

In the conventional developing device, when a bias voltage is applied to the developing sleeve 2 of one used developing device, the bias voltage is simultaneously applied to the developing sleeve 2 of another unused developing device. Was applied.

Therefore, in the unused developing device, the toner of the developer 4 remaining between the developing case 1 and the developing sleeve 2 electrostatically adheres to the developing sleeve 2.

However, conventionally, when developing with such a developing sleeve 2, a bias voltage is applied to the developing sleeve 2 with the toner adhered, so that only the portion where the toner adheres is effective. There has been a problem that the bias voltage becomes high and the amount of development increases, causing uneven development, and degrading image quality.

Therefore, an object of the present invention is to prevent the deterioration of image quality by removing the developer adhering to the developing sleeve of the unused developing device in such a developing device when a bias voltage is applied.

[0011]

Therefore, the method for controlling the rotation of the developing sleeve according to the present invention is, for example, as shown in the following illustrated embodiment, a plurality of developing devices 25a, 25b, 25c.
.Developing device 2 of image forming apparatus for selectively developing one of 25d to develop a latent image on an image carrier such as photoconductor 20
5, the developing sleeve 47 of the used developing device is rotated in the normal direction to attach the developer 50 to the developing sleeve 47 and convey the developer 50, and a bias voltage is applied to the developing sleeve 47 to apply the bias voltage to the image. The residual developer on the developing sleeve 47 after the transfer is transferred to the carrier and is rotated normally to remove the residual developer on the developing sleeve 47. On the other hand, after applying the bias voltage, the developing sleeve 47 of the unused developing device is reversed. It is characterized in that the developer 50 attached when the bias voltage is applied is removed.

According to a second aspect of the present invention, for example, as shown in the following illustrated embodiment, in the method for controlling the rotation of the developing sleeve 47 according to the first aspect, the development attached to the developing sleeve 47 of the unused developing device is performed. A condition is set such that the amount of the developer 50 reaches a limit value, and when the condition is reached, the developing sleeve 47 is reversed to remove the developer 50 adhered when the bias voltage is applied.

According to a third aspect of the present invention, for example, as shown in the following illustrated embodiment, in the method for controlling the rotation of the developing sleeve 47 according to the first aspect, the development attached to the developing sleeve 47 of the unused developing device is performed. The reverse rotation time of the developing sleeve 47 is changed according to the amount of the agent 50.

According to a fourth aspect of the invention, in the method of controlling the rotation of the developing sleeve 47 according to the first aspect, for example, as shown in the following illustrated embodiment, the development adhered to the developing sleeve 47 of the unused developing device. The reverse rotation speed of the developing sleeve 47 is changed according to the amount of the agent 50.

[0015]

[Function] When developing, the developing sleeve 4 of the developing device used
7, the developer 50 is attached to the outer periphery of the developing sleeve 47 by the magnetic pole portion 48, and the attached developer 50 is transferred to the image carrier by the bias voltage applied to the developing sleeve 47 and developed. Then, the normal rotation is performed as it is, and the residual developer on the developing sleeve 47 after the development is removed from the developing sleeve 47 by the non-magnetic pole portion 51. After the completion of the development, the developing sleeve 47 of the developing device used is reversed to clean the outer circumference of the developing sleeve 47. On the other hand, the developing sleeve 4 of the unused developing device
7 is also reversed, and the developer 50 attached when the bias voltage is applied during development is removed.

In the second aspect, the developing sleeve 47 is reversed only when the amount of the developer 50 attached to the developing sleeve 47 of the unused developing device reaches the limit value.

According to the third aspect of the invention, when the amount of the developer 50 attached to the developing sleeve 47 of the unused developing device is large, the reverse rotation time of the developing sleeve 47 is lengthened, and when it is small, it is shortened.

According to the fourth aspect, when the amount of the developer 50 attached to the developing sleeve 47 of the unused developing device is large, the reverse rotation speed of the developing sleeve 47 is increased, and when it is small, it is decreased.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 5 is a schematic configuration diagram of a color laser copying machine provided with a developing device using a developing sleeve rotation control method according to an embodiment of the present invention.

This color laser copying machine is designated by reference numeral 10 in the drawing.
The copying machine main body 11 is placed on the paper storage stand indicated by, and the color scanner 12 is placed thereon.

The paper tray 10 has a paper feed cassette 1 inside.
Equipped with 3.14. The color scanner 12 is provided with a contact glass 15 on the upper surface thereof, a light source 16 and a mirror 1 inside.
7a, 17b, 17c, an imaging lens 18, and a color sensor 19, and read the color image information of the document G, for example, for each color separation light of black, blue, red, and yellow to obtain an electrical image signal. Convert.

The main body 11 of the copying machine is provided with a drum-shaped photoconductor 20 in the substantially center thereof. Around the photoconductor 20, the charging device 21, the developing device 25, and
A transfer belt 24, a photoconductor cleaning device 23, and a charge eliminating device 22 are provided. An optical writing device 26 is provided on the photoconductor cleaning device 23, and a transfer belt cleaning device 27 is provided on the developing device 25 side of the transfer belt 24.
Further, a conveying device 28 is provided below the developing device 25, a transfer roller 29 is provided on the right side of the conveying device 28 in the drawing so as to be able to come into contact with and separate from the transfer belt 24, and a fixing device 32 is provided on the left side.

As shown in FIG. 4, the photoconductor cleaning device 23 includes the photoconductor cleaning blade 2
3a. The photoconductor cleaning blade 23a
Is made of rubber, is supported by the blade holder 23b, and has its tip pressed against the surface of the photoconductor 20. The transfer belt 24 is a drive roller 2 that is sequentially provided in the drive direction indicated by the arrow.
4a, bias roller 24b, backup roller 24
c and other driven rollers. Then, the driving force transmitted from the driving motor (not shown) is appropriately controlled so that it can be driven at the same speed as the photoconductor 20. The developing device 25 includes, in order from the top in the driving direction of the photoconductor 20, a black Bk developing device 25a and a blue (Cya) developing device.
n) C developing device 25b, red (Magenta) M developing device 25c, and yellow (Yellow) Y developing device 25d.

The transfer belt cleaning device 27 includes
A transfer belt cleaning blade 30 is provided. The transfer belt cleaning blade 30 is made of the same rubber as the photoconductor cleaning blade 23a, and is used for the blade holder 3
It is supported by 1 and its tip is pressed against the surface of the transfer belt 24. Then, the transfer belt cleaning device 27 is provided so as to be rotatable about the support shaft 27a, and the transfer belt cleaning blade 30 is provided with the transfer belt cleaning blade 30 according to the rotation.
It can be moved in and out of 4.

As shown in FIG. 5, the copying machine main body 11 is provided with a paper feed cassette 33 at its bottom and a paper feed cassette 34 on the right side in the figure. Then, sheets of various sizes are stored in the sheet feeding cassettes 33 and 34 and the sheet feeding cassettes 13 and 14. A manual paper feed tray 35 is provided above the paper feed cassette 34.

When copying the color original G, the original G is placed on the contact glass 15 and set, the full color mode is set, the paper size and the like are appropriately selected, and the copying operation is started. Then, for example, the paper P is sent out from the paper feed cassette 34 in the direction of the arrow A, and the paper P is transferred by the registration roller 37 at a timing.
4 to the lower side. The color scanner 12 reads, for example, a black image (image of the first color) on the color original G and converts it into an image signal.

On the other hand, the photosensitive member 20 is driven in the counterclockwise direction indicated by the arrow, and at that time, the surface of the photosensitive member 20 is uniformly charged by the charging device 21, and laser light is emitted by the optical writing device 26 based on the black image signal. To form an electrostatic latent image. Then, the electrostatic latent image is visualized when passing through the position of the black Bk developing device 25a. Then, by applying a predetermined bias voltage to the bias roller 24b, the black visible image is accurately aligned and transferred onto the transfer belt 24. After the transfer, the surface of the photoconductor 20 is cleaned by the photoconductor cleaning blade 23a.

Next, the color scanner 12 reads, for example, a blue image (second color image) on the color original G and converts it into an image signal. Based on the blue image signal, the optical writing device 26 similarly performs optical writing on the surface of the photoconductor 20 to form an electrostatic latent image on the photoconductor 20, and then the position of the blue C developing device 25b is changed. When passing, the electrostatic latent image is visualized. While the blue visible image is accurately aligned and transferred to the transfer belt 24,
Again, the surface of the photoconductor 20 is cleaned by the photoconductor cleaning blade 2
Clean with 3a.

By repeating the above-mentioned operation, a red visible image is formed on the photoconductor 20 by the M developing device 26c.
A yellow visible image is sequentially formed by the Y developing device 26d, these visible images are sequentially aligned and transferred onto the transfer belt 24, and a color image of four-color superposition is formed on the transfer belt 24. Complete.

Then, the surface of the photoconductor 20 after the image transfer is destaticized by the destaticizing device 22, while a predetermined bias voltage is applied to the transfer roller 29, the transfer roller 29 is brought into contact with the transfer belt 24, and the registration roller 37. The color image is transferred at once to the paper P conveyed by.

After the color transfer, the paper P is conveyed by the conveying device 28.
Then, the color image is conveyed to the fixing device 32, and the fixing device 32 fixes the color image. After fixing, the paper P is discharged onto the paper discharge tray 40 by the paper discharge roller 39.

After color transfer, the transfer belt 24 is
The surface is cleaned by the transfer belt cleaning blade 30.

By the way, one of a plurality of developing devices provided in the developing device 25, for example, red (Mag)
The enta) M developing device 25c is configured as shown in detail in FIG. Reference numeral 45 in the figure denotes a developing case. The developing case 45 is formed in a box shape that is horizontally long in the axial direction of the photoconductor 20, a developing window hole 45a is opened facing the photoconductor 20, and a toner concentration sensor 46 is attached on the opposite side. In the developing case 45, a rotatable developing sleeve 47 is provided with its outer periphery facing the developing window hole 45a, and a paddle 49 is rotatably provided below the developing sleeve 47 in the drawing. A magnet 48 is provided inside the developing sleeve 47 so as to be fixed to the developing case 45.

Although not shown, the remaining three developing devices, that is, the black Bk developing device, the blue (Cyan) C developing device 25b, and the yellow (Yello).
The Y developing device 25d of w) has the same structure as the M developing device 25c.

During development, the paddle 49 is rotated clockwise in the figure to stir and convey the developer 50, and the developing sleeve 47 is normally rotated clockwise in the figure. Then, it conveyed periphery developer 50 attached to the developing sleeve 47 by the magnetic poles N ₂ pumping magnets 48, with the developer 50 having its adhering to the rotation of the developing sleeve 47 pole S ₂
And a doctor 45b in the middle of the conveyance to regulate the amount to a certain amount, apply a bias voltage to the developing sleeve 47, and transfer to the photoreceptor 20 at the main developing pole N ₁ to form a visible image. . After the visible image, the developing sleeve 47
Is normally rotated and the residual developer is transported by the transport magnetic pole S ₁ , and the residual developer on the developing sleeve 47 is removed from the developing sleeve 47 by the non-magnetic pole portion 51.

After the completion of the development, the residual developer on the developing sleeve 47 which does not reach the non-magnetic pole portion 51 is removed by the non-magnetic pole portion 51 by reversing the developing sleeve 47 in the counterclockwise direction in the figure. The agent is cut off to clean the outer circumference of the developing sleeve 47.

However, the developing sleeve 47 after the development is completed.
As shown in FIG. 3, the developer 50 is magnetically trapped between the developing case 45 and the developing sleeve 47 and remains on the upper portion.

When the bias voltage is applied to the developing sleeve 47 of the used developing device, the bias voltage is also applied to the developing bias 47 of the unused developing device at the same time. The toner of the developer 50 magnetically trapped is electrostatically attached.

Therefore, when developing with such a developing sleeve 47, if it is used as it is, when the bias voltage is applied to the developing sleeve 47, the bias voltage is effectively increased only in the portion where the toner adheres, and the developing amount is increased. Increase, uneven development occurs and the image quality deteriorates.

Therefore, according to the method of controlling the rotation of the developing sleeve 47 of the present invention, as shown in FIG. 1, it is judged whether or not developing is performed by applying a bias voltage to the last used developing device in the developing order among the used developing devices. If it is the last developing device, it is judged whether or not the ear-cutting operation is completed. If the ear-cutting operation is completed, the developing sleeves 47 of all the developing devices are sequentially or simultaneously one by one. Reverse. Then, the toner adhering to the developing sleeve 47 of the unused developing device is mechanically removed by rubbing with the rest of the magnetically trapped developer 50, and further removed by frictional charging with the carrier. . Next, it is determined whether the reverse rotation of the developing sleeve 47 has passed for a predetermined time, and after the predetermined time has passed, the reverse rotation of the developing sleeve 47 is stopped.

In the above-described embodiment, the developing sleeves 47 of all the developing devices including the last developing device are reversed. However, as shown in FIG. 6, the developing sleeve 47 may be reversed except for the last used developing device. By doing so, it is possible to eliminate a wasteful reversing operation of reversing the developing sleeve 47 to which the developer is not attached.

The developing sleeve 47 described above may be reversed when the bias voltage is applied, or may be reversed when the bias voltage is not applied, as shown in FIG. When the bias voltage is not applied, the developing sleeve 4
If 7 is reversed, toner adhesion on the developing sleeve 47 can be reduced.

Further, in the above-described embodiment, the reverse rotation of the developing sleeve 47 of the unused developing device is stopped until the cutting operation of the developing device used is completed. However, as shown in FIG.
For example, when the Bk developing device is used, the developing sleeve 47 for non-use development such as the C developing device and the M developing device may be reversed until the brush cutting operation of the used developing device is completed. With this configuration, the developing sleeve 47 is applied when the bias voltage is applied.
Since the toner is rotating, it is possible to prevent toner from adhering.

By the way, FIG. 9 shows the relationship between the toner adhesion amount on the developing sleeve 47 of the unused developing device and the number of scans. As can be seen from this figure, the amount of adhesion on the developing sleeve 47 gradually increases as the number of scans after developing with the developing sleeve 47 until the next developing with the developing sleeve 47 increases. When the adhered amount W ₁ is exceeded,
Next, when developing with the developing sleeve 47, uneven development occurs. Therefore, the adhesion amount W ₁ is set as a limit value, and the number of scans at that time is set as K ₁ .

However, in the rotation control method of the developing sleeve of the present invention, as shown in FIG. 10, if the number of scans Kn is K ₁ or less compared with the number of scans K ₁ , the adhesion amount W ₁ or less. It ends without it. On the other hand, the number of scans K
When n is larger than the number of scans K _1, it is considered that the adhered amount Wn on the developing sleeve 47 exceeds the adhered amount W _1, and the reverse rotation time Tn of the developing sleeve required for removing the adhered amount Wn from FIG. The development sleeve after the job
Reverse rotation for n hours. In this way, when the adhered amount W ₁ is exceeded, the developing sleeve 47 is reversed to remove the adhered developer, so that unnecessary operation can be eliminated and the developer can be efficiently removed.

In the embodiment shown in FIGS. 9 and 10, the amount of adhesion on the developing sleeve 47 is known from the number of scans. However, as shown in FIG. 12, the amount of adhesion of the developing sleeve 47 may be known from the integrated amount of the developing bias. Here, the development bias integration amount is the total of the bias voltage application time × the bias voltage magnitude (V). Reference numeral S _{1 in the} figure is the development bias integration amount corresponding to the adhesion amount W ₁ which is the limit value.

Therefore, in the rotation control method of the developing sleeve of the present invention, as shown in FIG.
When n is larger than the integrated bias amount S ₁ , the adhesion amount Wn on the developing sleeve 47 exceeds the adhesion amount W ₁ .
The reverse rotation time Tn of the developing sleeve 47 for removing the adhesion amount Wn from 1 is obtained, and the developing sleeve 47 is reversely rotated for the time Tn after the job. In this way, since the amount of adhesion of the developing sleeve 47 is known from the integrated amount of the developing bias, the amount of adhesion can be known more accurately.

As can be seen from FIG. 11, when the number of revolutions M ₁ of the developing sleeve 47 is constant, the developing sleeve 4
If the amount of toner adhering on 7 is small, the reverse rotation time of the developing sleeve necessary for its removal is short, and if the amount of adhering toner is large, the reverse rotation time of the developing sleeve 47 is long.

Therefore, according to the rotation control method of the developing sleeve of the present invention, the developing sleeve 4 of the unused developing device is used.
The reverse rotation time of the developing sleeve 47 may be changed in accordance with the amount of toner attached to the developing sleeve 47. By doing so, it is possible to remove the toner with the minimum necessary operation according to the amount of toner attached on the developing sleeve 47 of the unused developing device.

As can be seen from FIG. 14, when the reverse rotation time for removing the toner adhering to the developing sleeve 47 is set to a constant value, the rotation speed of the developing sleeve 47 during reverse rotation is increased. Good.

Therefore, in the rotation control method of the developing sleeve of the present invention, the reverse rotation speed of the developing sleeve 47 may be changed according to the amount of toner attached to the developing sleeve 47 of the unused developing device. This way,
The toner can be removed by the minimum necessary operation according to the amount of toner attached on the developing sleeve 47 of the unused developing device.

[0052]

Therefore, according to the present invention, for example, when the cutting operation of the last developing device in the developing order is completed,
Since the developing sleeve of the unused developing device is reversed and the developer that adheres when the bias voltage is applied during development is removed, the bias voltage partially increases even when developing with this developing sleeve. It is possible to obtain a high-quality image without uneven development, without increasing the amount.

According to the second aspect of the invention, since the developing sleeve is reversed only when the amount of the developer adhered to the developing sleeve reaches the limit value, the wasteful operation is eliminated and the developer is adhered. The developer can be removed efficiently.

Further, according to the third aspect of the present invention, the reverse rotation time of the developing sleeve is changed according to the amount of the developer adhered to the developing sleeve of the unused developing device. If you change the reverse rotation speed of the developing sleeve,
The developer can be removed with the minimum necessary operation depending on the amount of the developer attached to the developing sleeve of the unused developing device.

[Brief description of drawings]

FIG. 1 is a flow chart of a developing sleeve rotation control method according to an embodiment of the present invention.

FIG. 2 is an enlarged schematic configuration diagram of one developing device including the developing sleeve.

FIG. 3 is a state diagram after the use.

FIG. 4 is an enlarged schematic configuration diagram around a developing device including a plurality of the developing devices.

FIG. 5 is an overall schematic configuration diagram of a color laser copying machine including the developing device.

FIG. 6 is a flowchart of a developing sleeve rotation control method according to another embodiment of the present invention.

FIG. 7 is a flowchart of a developing sleeve rotation control method according to still another embodiment.

FIG. 8 is a flowchart of a rotation control method of a developing sleeve according to still another embodiment.

FIG. 9 is a graph showing the relationship between the amount of adhesion on the developing sleeve and the number of scans.

FIG. 10 is a flowchart of a developing sleeve rotation control method according to still another embodiment of the present invention.

FIG. 11 is a graph showing the relationship between the amount of adhesion on the developing sleeve and the reverse rotation time of the developing sleeve necessary for its removal.

FIG. 12 is a graph showing the relationship between the amount of adhesion on the developing sleeve and the integrated amount of developing bias.

FIG. 13 is a flow chart of a developing sleeve rotation control method according to still another embodiment of the present invention.

FIG. 14 is a graph showing the relationship between the amount of adhesion on the developing sleeve and the reverse rotation speed of the developing sleeve necessary for removing the amount.

FIG. 15 is an enlarged schematic configuration diagram of one developing device included in the developing device of the conventional color laser copying machine.

FIG. 16 is a state diagram after the use.

[Explanation of symbols]

 20 Photoreceptor 25 Developing Device 25a Black (Black) Bk Developing Device 25b Blue (Cyan) C Developing Device 25c Red (Magenta) M Developing Device 25d Yellow (Yellow) Developing Device 47 Developing Sleeve 48 Magnet 50 Developer 51 Non-Pole Part

Claims (4)

[Claims] 1. One of a plurality of developing devices is selectively used,
In a developing device of an image forming apparatus for developing a latent image on an image bearing member, a developing sleeve of a developing device used is normally rotated to attach a developer to the developing sleeve and convey the developer. A bias voltage is applied to the sleeve to transfer the image to the image carrier, and normal rotation is performed to remove the residual developer on the developing sleeve after the transfer. A method of controlling the rotation of the developing sleeve by reversing the developing sleeve of the container and removing the developer adhering when the bias voltage is applied. 2. A condition in which the amount of the developer adhered to the developing sleeve of the unused developing device reaches a limit value, and when the condition is reached, the developing sleeve is reversed to develop the toner adhered when a bias voltage is applied. The method for controlling rotation of the developing sleeve according to claim 1, wherein the agent is removed. 3. The rotation control method for the developing sleeve according to claim 1, wherein the reverse rotation time of the developing sleeve is changed according to the amount of the developer adhered to the developing sleeve of the unused developing device. 4. The rotation control method of the developing sleeve according to claim 1, wherein the reverse rotation speed of the developing sleeve is changed according to the amount of the developer attached to the developing sleeve of the unused developing device.