JPH09197815A - Developing device for image forming apparatus - Google Patents

Abstract

An object of the present invention is to provide a developing device of an image forming apparatus capable of reducing the bending of the developing roller without increasing the cost of the developing device. A supply roller 21BR to a developing roller 21
The direction of the resultant force FR of the load FRr and the load FRs applied to the BS, and the developing roller 21BS from the developing blade 21BB.
The directions of the resultant force FB of the load FBr and the load FBs given to the are set to be opposite to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a printer.

[0002]

2. Description of the Related Art First, a conventional color laser printer will be briefly described with reference to FIG. In FIG. 4, the rotary developing device 105 is a developing device of each color, that is, a developing device 105 provided with magenta, cyan, yellow, and black toners.
H, 105C, 105Y, and 105K. These four-color developing devices are rotatably arranged with respect to the shaft 105e, and the centers of the respective developing devices rotate in conjunction with the rotating gears arranged on the outer periphery of the revolving gear to maintain their postures constant. Has been done.

At the time of image formation, the developing devices 105H, 1
Of the 05C, 105Y, and 105K, the developing device for the color corresponding to the latent image stands still at a position facing the image carrier 104a,
For example, when the magenta developing device 105H is selected as shown in FIG. 4, the developing roller 105b, which is a developer carrier, is further positioned so as to face the surface of the image carrier 104a with a minute gap therebetween.

At the time of development, the developing roller 105b is applied with a bias and is rotationally driven, so that the image carrier 1
The latent image on 04a is developed to form a toner image.

Further, the supply roller 105a is in sliding contact with the developing roller 105b arranged in the developing device 105H, so that the toner not contributing to the development is scraped off so that the fresh developer is always supplied. It has become. The same applies to the other developing devices 105C, 105Y, and 105K.

[0006]

However, according to the above-mentioned conventional example, the developing blade 105c as the developer regulating member applies a predetermined amount to the developing roller 105b in order to uniformly apply the developer to the developing roller 105b. Since the developing roller 105a is pressed by pressure and the supply roller 105a as a developer supplying roller is also pressed and rotated against the developing roller 105b, the developing roller 105b is rotated by the developing blade 105a.
In some cases, a small amount (0 to 150 μm) of flexure occurs due to elastic deformation caused by the load of c and the supply roller 105a.

In the thin hollow developing roller, since the amount of bending becomes large, the change in the amount of the gap with the image carrier becomes large, which may cause uneven development.

Therefore, in the above-mentioned conventional example, the developing roller is formed of a solid cylinder in order to minimize the bending.

However, since the developing device has a structure in which the magnet roller is not used and the non-magnetite developer is used, the developing roller can be made solid, but the developer having magnetite is used. In a developing device using (usually black toner), disposing the magnet roller inside the developing roller is an essential constituent condition. That is, it is difficult to arrange the magnet roller unless the developing roller uses a hollow thin base material.

Therefore, as shown in the conventional example, since it is very difficult to make the developing roller solid, the amount of bending of the developing roller becomes significantly larger than that of the conventional example, and uneven development occurs. Sometimes occurred.

On the other hand, as another measure for reducing the amount of bending, it is considered to improve the mechanical strength of the base material of the developing roller.

That is, for example, the same mechanical strength can be secured even in the hollow thin wall structure by changing the conventional aluminum to a steel material.

However, since the magnet roller is arranged inside, the steel material must be a non-magnetic material, and this time the cost of the material may increase significantly.

Therefore, an object of the present invention is to provide a developing device of an image forming apparatus capable of reducing the bending of the developing roller without increasing the cost of the developing device.

[0015]

According to the first invention of the present application, the above-mentioned object is to provide a cylindrical or cylindrical developer carrier and a developer supply which rotates in contact with the developer carrier. In a developing device of an image forming apparatus having a roller and a developer regulating member for applying a developer to the developer carrying member, a bending direction of the developer carrying member due to a load given by the developer regulating member, and the developing Achieved by disposing the developer regulating member and the developer supply roller with respect to the developer carrier so that the bending directions of the developer carrier due to the load applied by the developer supply roller are opposite to each other. To be done.

According to the second aspect of the present invention,
In the first aspect of the invention described above, the rotation direction of the developer supply roller is opposite to the rotation direction of the developer carrier, and the rotation speed of the developer supply roller is larger than the rotation speed of the developer carrier. It is achieved by being.

Further, according to a third invention of the present application, in the above-mentioned first invention or second invention, the above-mentioned object is such that the developer carrying member is arranged in proximity to the image carrying member,
The bending direction of the developer carrying member is achieved by facing the tangential direction of the image carrying member at the closest position.

According to a fourth aspect of the present invention,
The above object can be achieved by the developer carrying member according to any one of the first to third inventions, wherein the developer carrying member is a hollow thin cylindrical member and a magnet roller is provided therein.

Further, according to a fifth invention of the present application, the object is that the object is detachable from the image forming apparatus main body in any one of the first invention to the fourth invention. It is achieved by

That is, in the first aspect of the present invention, loads are applied to the developer carrying member from the developer regulating member and the developer supply roller, respectively. Are opposite to each other, so they cancel each other out and reduce the occurrence of bending of the developer carrier.

In the second invention of the present application, the rotation direction of the developer supply roller of the first invention is
Since it is in the opposite direction to the rotation direction of the developer carrier and the rotation speed of the developer supply roller is higher than the rotation speed of the developer carrier, it is possible to reliably scrape the highly charged developer on the developer carrier. And, unlike the first aspect of the invention, the bending is not generated.

Further, in the third invention according to the present application, the developer carrying member according to the first invention or the second invention is arranged in proximity to the image carrying member, and the bending direction of the developer carrying member is increased. Is oriented in the tangential direction of the image carrier at the closest position, so that the gap between the developer carrier and the image carrier is not changed even when the loads applied to the developer carrier are not equal to each other.

Further, in the fourth invention of the present application, the developer carrying member according to any one of the first to third inventions is a hollow thin cylinder, and a magnet roller is provided inside. Since it is provided, the development using the developer having magnetite is performed while reducing the bending of the developer carrier.

Further, in the fifth invention according to the present application, the developing device according to any one of the first to fourth inventions is detachable from the main body of the image forming apparatus. While improving the maintainability while reducing the bending of the.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the accompanying drawings. First, the overall configuration of a color image forming apparatus according to an embodiment of the present invention will be outlined with reference to FIG. FIG. 1 is a diagram illustrating the overall configuration of a laser printer that is one form of a color image forming apparatus.

As shown in FIG. 1, the color laser printer has an image carrier 15 rotating at a constant speed, a fixed black developing device 21B, a rotatable yellow developing device 20Y, a magenta developing device 20M, and a cyan developing device 20C. And an intermediate transfer member 9 for holding the color image developed and multiply-transferred by the image forming unit and further transferred to the transfer material 2 fed from the feeding unit. The transferred transfer material 2 is transferred to the fixing unit 25 to fix the color image on the transfer material 2, and is discharged to the discharge unit 37 on the upper surface of the apparatus by the discharge roller 36. The rotatable color developing devices 20Y, 20M, 20C and the fixed black developing device 21B are separately attachable to and detachable from the printer body.

Next, the structure of each part of the image forming apparatus will be sequentially described in detail. The drum unit 13 is integrally configured with an image carrier 15 such as a photosensitive drum and a container 14 of a cleaning device which also serves as a holder for the image carrier 15. The drum unit 13 is detachably supported on the printer main body, and the unit can be easily replaced according to the life of the image carrier 15.

The image carrier 15 according to this embodiment has a diameter of about 6
An organic photoconductor layer is applied on the outside of a 2 mm aluminum cylinder, and is rotatably supported by a container 14 of a cleaning device that also serves as a holder for the image carrier 15. On the periphery of the image carrier 15, a cleaner blade 16,
The primary charging means 17 is arranged, and by transmitting the driving force of a drive motor (not shown) to one end on the back side of the drawing,
The image carrier 15 is rotated counterclockwise in the drawing according to the image forming operation.

The primary charging means 17 uses a contact charging method, and a conductive roller is brought into contact with the image carrier 15 and a voltage is applied to the conductive roller, whereby the image carrier 15 is charged. The surface is uniformly charged.

Further, the exposure of the image carrier 15 is performed from the scanner section 30. First, when an image signal is given to the laser diode, the laser diode irradiates the polygon mirror 31 with image light corresponding to the image signal. Next, the polygon mirror 31 is rotated at a high speed by the scanner motor, and the image light reflected by the polygon mirror 31 is selectively exposed on the surface of the image carrier 15 rotating at a constant speed through the imaging lens 32 and the reflection mirror 33. As a result, an electrostatic latent image is formed on the image carrier 15.

On the other hand, the developing means includes three rotary developing devices 20Y, 20Y capable of developing each color of yellow, magenta, cyan and black in order to visualize the electrostatic latent image.
M, 20C and one black developing device 21B.

The black developing device 21B is a fixed developing device, and a developing roller 21BS, which is a developer carrying member, is arranged at a position facing the image carrying member 15 with a minute gap (about 300 μm) from the image carrying member 15 to carry out image carrying. A visible image is formed on the body 15 with black toner.

The toner capacity of the black developing device 21B is more than twice the toner capacity of the other yellow developing device 20Y, magenta developing device 20M, and cyan developing device 20C in consideration of the documents and image patterns handled by the user and the toner consumption amount of 15000. Since the toner equivalent to the page (A4,5% printing) is included, by increasing the capacity of the black developing device 20K in this way, the frequency with which the user replaces the black developing device 20K is reduced and the print 1 It is also possible to reduce the running cost per sheet.

Further, as shown in FIG. 1, the arrangement positions of the black developing devices are a laser scanner portion 30 which is an exposing device, a yellow developing device 20Y which is a rotary developing device, and a magenta developing device 20.
By disposing it in the middle of the M and cyan developing units 20C, it is possible to prevent the toner leaking when the yellow developing unit 20Y, the magenta developing unit 20M, and the cyan developing unit 20C rotate from scattering to the optical components such as the laser scanner unit 30. To prevent. As a result, the toner becomes
It is possible to prevent a clear output image from being obtained by preventing it from being attached to the lens 1, the lens 32, the mirror 33, or the like and interfering with the latent image formation.

Further, three rotary developing devices 20Y, 20M,
The toner 20C contains toner corresponding to 6000 pages (A4, 5% printing) and is detachably held by the developing rotary 23 which rotates about the shaft 22.

At the time of image formation, while the developing devices are held by the developing rotary 23, the developing devices rotate about the shaft 22 and the predetermined developing device stops at a position facing the image carrier 15 and further develops. After the sleeve is positioned so as to face the image carrier 15 with a minute gap (about 300 μm), a visible image is formed corresponding to the electrostatic latent image of the image carrier 15.

At the time of forming a color image, the developing rotary 23 rotates for each rotation of the intermediate transfer member 9, and the yellow developing device 2
The developing process is performed in the order of 0Y, magenta developing device 20M, cyan developing device 20C, and then black developing device 20B.

Taking the yellow developing device 20Y as an example, the toner in the container is fed to the coating roller 20YR by the toner feeding mechanism and rotates clockwise in the drawing to the coating roller 20YR and the developing roller 20YS.
A thin layer of toner is applied to the outer circumference of the developing roller 20YS which is pressed against the outer circumference of the developing roller 20YB and rotates clockwise in the drawing by the developing blade 20YB, and a charge is applied to the toner by frictional charging. Then, by applying a developing bias to the developing roller 20YS facing the image carrier 15 on which the latent image is formed, toner development is performed on the image carrier 15 according to the latent image. Magenta developing device 20M, cyan developing device 2
For 0C, toner development is performed by the same mechanism as above.

Further, the rotary developing devices 20Y, 20M, 20
Each developing roller of C is connected to a high-voltage power source for driving each color provided in the printer main body and a drive when each developing device is rotationally moved to the developing position, and a voltage is sequentially and selectively applied for each color developing. , The drive is connected.

Next, the intermediate transfer body 9 carries out the toner image on the image carrier 15 visualized by each developing device four times (each image of four colors of yellow, magenta, cyan and black) during the color image forming operation. In order to receive the multiple transfer, the intermediate transfer member 9 rotated clockwise in the drawing in synchronization with the outer peripheral speed of the image carrier 15, and the intermediate transfer member 9 subjected to the multiple transfer is transferred by the transfer roller 10 to which the voltage is applied. The toner images of the respective colors on the intermediate transfer material are simultaneously and multiple-transferred onto the transfer material 2 by sandwiching and transporting.

The intermediate transfer member 9 according to this embodiment has a diameter of 18
The outer circumference of a 6 mm aluminum cylinder 12 is covered with an elastic layer 11 such as medium resistance sponge or medium resistance rubber. The intermediate transfer body 9 is rotated by being driven by a gear (not shown) which is rotatably supported and integrally fixed.

The cleaning means cleans the toner remaining on the image carrier 15 after the toner visualized on the image carrier 15 by the developing means is transferred to the intermediate transfer body 9, and is cleaned. The waste toner is stored in the cleaner container 14. The amount of waste toner stored in the container 14 does not fill the container 14 earlier than the life of the image bearing member 15, and therefore the cleaner container 14 is used as the image bearing member 1.
5 is replaced at the same time when the service life is replaced.

The paper feeding unit feeds the transfer material 2 to the image forming unit, and includes a cassette 1 containing a plurality of transfer materials 2, a paper feeding roller 3, a feeding roller 4, and a retard roller for preventing double feeding. 5, a paper feed guide 6, and a registration roller 8.

At the time of image formation, the paper feed roller 3 is driven and rotated in accordance with the image forming operation to separate and feed the transfer materials 2 in the cassette 1 one by one, and the guide plate 6 guides the transfer material 2 through the conveying roller 7. Then, the registration roller 8 is reached.

During the image forming operation, the registration roller 8 performs a non-rotating operation for holding the transfer material 2 in a stationary state and a rotating operation for conveying the transfer material 2 toward the intermediate transfer body 9 in a predetermined sequence. Image and transfer material 2 during the transfer process, which is a process
Align with.

The transfer portion is composed of a swingable transfer roller 10. The transfer roller 10 has a metal shaft wound with a medium resistance foamed elastic body, and is movable up and down as shown in the drawing and has a drive. .

While the toner images of four colors are being formed on the intermediate transfer member 9, that is, while the intermediate transfer member 9 is rotating a plurality of times, the transfer roller is indicated by the solid line in FIG. 1 so as not to disturb the image. 10 is located below and is separated from the intermediate transfer member 9.

After the four color toner images have been formed on the intermediate transfer member 9, the transfer roller 10 is moved to a position by a cam member (not shown) at the timing of transferring the color image onto the transfer material 2. As shown in FIG. 1, it is pressed against the intermediate transfer body 9 with a predetermined pressure via the transfer material 2 at the upper and lower positions indicated by thin lines. At this time, a bias is applied to the transfer roller 10 at the same time, and the toner image on the intermediate transfer body 9 is transferred to the transfer material 2.

Since the intermediate transfer body 9 and the transfer roller 10 are respectively driven, the transfer material 2 sandwiched between the two is subjected to the transfer process and at the same time leftward in the drawing at a predetermined speed. And is sent to the fixing unit 25 which is the next step.

The fixing section 25 is for fixing the toner image formed on the transfer material 2 through the intermediate transfer body 9 to the toner image formed by the developing means 20 and 21, and as shown in FIG. It comprises a fixing roller 26 for applying heat to the transfer material 2 and a pressure roller 27 for bringing the transfer material 2 into pressure contact with the fixing roller 26. Each roller is a hollow roller and has heaters 28, 29 therein. The transfer material 2 is driven to rotate, and at the same time, the transfer material 2 is conveyed.

That is, the transfer material 2 holding the toner image is conveyed by the fixing roller 26 and the pressure roller 27, and
By applying heat and pressure, the toner is fixed on the transfer material 2.

Next, the configuration of the developing device used in the image forming apparatus of the present embodiment as described above will be described in detail with reference to FIG.

As shown in FIG. 2, in the black developing device 21B, the toner in the container is sent by the sending mechanism 21BT, and the coating blade 21B pressed against the outer circumference of the developing roller 21BS.
The developing roller 21 that rotates clockwise in the drawing by B
A thin layer of toner is applied to the outer periphery of the BS, and the toner is charged by frictional charging.

Further, by applying a developing bias to the developing roller 21BS, jumping development is performed in which toner is caused to fly corresponding to the electrostatic latent image on the image carrier 15, and electrostatic reversal development is performed on the image carrier 15. The latent image is visualized as a toner image.

Therefore, the highly charged toner that has not contributed to the development remains electrostatically on the surface of the developing roller 21BS after the development. Even when developing, it is not developed, rather,
This causes uneven development called a ghost image.

This ghost image has not been seen as a problem in a conventional monochrome image having a relatively low resolution, but in recent years, with the progress of computers, higher resolution (1200 dpi) of printers and full-color printers have been further developed in the market. In what is desired, it is not acceptable.

Therefore, in the apparatus of the present embodiment, as one measure for eliminating the ghost image, the supply roller 21BR is rotated in contact with the developing roller 21BS.
Highly charged toner remaining on the surface of the developing roller 21BS is forcibly scraped off. In order to enhance the scraping effect, the supply roller 21BR rotates counterclockwise in the drawing at a speed (1.2 to 2.0 times) higher than the rotation speed of the developing roller 21BS.

The supply roller 21BR applies a radial load FRr and a frictional force FRs in the roller tangential direction to the developing roller 21BS. Similarly, the developing blade 21BB also applies a radial load FBr and a frictional force FBs in the roller tangential direction to the developing roller 21BS.

In this embodiment, the supply roller 21BR is
The direction of the resultant force FR of the load FRr and the load FRs is opposite to the direction of the resultant force FB of the load FBr and the load FBs of the developing blade 21BB. That is, the resultant load force FR of the supply roller 21BR and the resultant load force FB of the developing blade 21BB cancel each other out, and the developing roller 21B
The load on S is greatly reduced.

Further, when the resultant load forces FR and FB are not equal, the developing roller 21 is moved to the one having the larger resultant load force.
Although the BS elastically deforms, the direction in which the developing roller 21BS elastically deforms is the developing roller 2 in the present embodiment.
It faces in a direction substantially equal to the tangential direction at the closest position of 1BS and the image carrier 15. That is, since the developing roller 21BS moves substantially parallel to the image carrier 15, the developing roller 21BS
Since the space gap between the BS and the image carrier 15 does not change significantly, uneven development can be suppressed.

In this embodiment, the positional relationship among the supply roller 21BR, the developing blade 21BB, and the developing roller 21BS in the black developing device 21B is configured as described above. It goes without saying that it is effective.

[0062]

As described above, the first embodiment according to the present application is described.
According to the invention of claim 1, a load is applied to the developer carrying member from each of the developer regulating member and the developer supply roller, but the bending directions of the developer carrying member due to the respective loads are opposite to each other. It is possible to reduce the occurrence of bending of the agent carrier. As a result, it is not necessary to form the base material of the developer carrying member by a non-magnetic steel material, the conventionally used thin hollow cylinder can be used, and an extra cost increase can be prevented. Further, in the developer carrier using a solid cylinder, the cylinder can be made thin, so that the cost of the developing roller can be reduced and a lower cost developing device can be provided. In addition, unevenness in development can be suppressed by reducing bending.

According to the second invention of the present application,
Since the rotation direction of the developer supply roller of the first invention is opposite to the rotation direction of the developer carrier, and the rotation speed of the developer supply roller is higher than the rotation speed of the developer carrier.
The highly charged developer on the developer carrying member is scraped off reliably, and no bending is generated unlike the first invention. Therefore, good development without ghost and development unevenness can be realized without increasing cost.

Further, according to the third invention of the present application, the developer carrying member according to the first invention or the second invention is arranged in proximity to the image carrying member, and the developer carrying member bends. Since the direction is the tangential direction of the image carrier at the closest position, even if the loads applied to the developer carrier are not equal to each other, the gap between the developer carrier and the image carrier is not changed, A developing device capable of reliably preventing uneven development can be provided at low cost.

According to the fourth invention of the present application,
The developer carrying member according to any one of the first to third inventions is a hollow thin-walled cylindrical body, and the magnet roller is provided therein, so that the bending of the developer carrying member is reduced. Meanwhile, the development using the developer having magnetite can be performed at low cost.

Further, in the fifth invention of the present application, the developing device according to any one of the first invention to the fourth invention is detachable from the main body of the image forming apparatus. It is possible to provide a developing device that improves the maintainability while reducing the bending of the developing device at low cost.

[Brief description of drawings]

FIG. 1 is a sectional view of a color laser printer according to an embodiment of the present invention.

FIG. 2 is a sectional view showing a developing device according to an embodiment of the present invention.

FIG. 3 is a perspective view of a black developing device according to an embodiment of the present invention.

FIG. 4 is a sectional view of a conventional color laser printer.

[Explanation of symbols]

 15 image carrier 20Y yellow developing device (developing device) 20YB developing blade (developer regulating member) 20YR supply roller (developer supplying roller) 20YS developing roller (developer carrier) 20M magenta developing device (developing device) 20C cyan developing Developing device (developing device) 21B Black developing device (developing device) 21BB Developing blade (developer regulating member) 21BS Developing roller (developer carrying member) 21BR Supply roller (developer supplying roller)

Claims (5)

[Claims] 1. A cylindrical or columnar developer carrying member, and a developer supply roller which rotates in contact with the developer carrying member.
In a developing device of an image forming apparatus having a developer regulating member for applying a developer to the developer bearing member, a bending direction of the developer bearing member due to a load applied by the developer regulating member, and the developer supply roller. An image characterized in that the developer regulating member and the developer supply roller are arranged with respect to the developer carrier so that the bending directions of the developer carrier due to the load given by the developer carrier are opposite to each other. Developing device of forming device. 2. The rotation direction of the developer supply roller is opposite to the rotation direction of the developer carrier, and the rotation speed of the developer supply roller is higher than the rotation speed of the developer carrier. 1. The developing device of the image forming apparatus described in 1. 3. The developer carrying member is disposed in the vicinity of the image carrying member, and the bending direction of the developer carrying member is in the tangential direction of the image carrying member at the closest position.
Alternatively, the developing device of the image forming apparatus according to claim 2. 4. The image forming apparatus according to claim 1, wherein the developer carrying member is a hollow thin cylinder, and a magnet roller is provided inside. Development device. 5. The developing device of the image forming apparatus according to claim 1, wherein the developing device is detachable from the main body of the image forming apparatus.