JP2001117370A - Developing device and image forming device using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device constituted so that image quality can be made higher by enhancing the responsiveness thereof required when the take in action and the take in stop action of toner is switched in accordance with the sudden change of toner consumption and a image forming device using this developing device. SOLUTION: In a developer housing part 17a, a cylindrical rotary member 23 driven to be rotated in an identical rotating direction to a developing sleeve 15 is disposed at the most upstream side in the rotating direction of the sleeve 15 by leaving fixed space between the sleeve 15. Since the fetching state of the toner is changed according to the change of the toner concentration of developer 14 at a part where the sleeve 15 and the rotary member 23 are opposed, the take in action of the toner is switched without awaiting the change of the toner concentration of the whole developer. Thus, the responsiveness is extremely enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, and the like.
By using a two-component developer containing a toner and magnetic particles, changing the state of taking in the toner into the developer based on the change in the toner concentration of the developer on the developer carrier, and taking in the toner with the movement of the developer The present invention relates to a developing device for self-controlling toner density and an image forming apparatus using the same.

[0002]

2. Description of the Related Art Conventionally, there has been known a developing device which takes in toner by the movement of a developer without requiring a toner density detecting means. However, in this type of developing device, the amount of toner taken in is different between a place where the movement of the developer is active and a place where the movement of the developer is not so, or a place where the amount of the developer is large and a place where the amount of the developer is small. Image density unevenness is likely to occur. Therefore, various proposals have been made. In Japanese Patent Application Laid-Open No. 9-197833, toner is developed by moving a developer in a developer accommodating portion for accommodating a developer whose progress has been prevented by a developer regulating member. There has been disclosed a developing device which takes in a developer on an agent carrier and self-controls the toner supply constantly and constantly. This developing device is downsized,
It is possible to easily adjust the toner density while reducing the cost, and it is effective for the above-mentioned problems.

However, in this type of developing device,
The toner is diffused by the circulation of the developer in order to make the toner concentration uniform, but a certain amount of time is required until the whole becomes uniform. On the other hand, the responsiveness of switching between the toner take-in and the stop operation may be slow. If the response is slow,
If the amount of toner consumption increases abruptly on the toner consumption side, the toner density decreases, so that a high image area density cannot be secured and the image density may be reduced. Also, when the toner consumption decreases sharply, the toner density increases,
There is a possibility that the background becomes dirty and the concentration becomes excessive.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and an object of the present invention is to provide a method for switching between a toner taking-in operation and a stopping operation in response to a rapid change in toner consumption. An object of the present invention is to provide a developing device capable of realizing higher image quality by improving responsiveness and an image forming apparatus using the same.

[0005]

According to a first aspect of the present invention, there is provided a magnetic recording medium having a magnetic field generating means therein for carrying and transporting a two-component developer containing a toner and a magnetic carrier. A developer carrying member, a regulating member that regulates the amount of the developer carried and conveyed by the developer carrying member, and a developer accommodating portion that accommodates the developer scraped by the regulating member,
A toner container adjacent to the developer accommodating portion and accommodating toner so as to be taken in contact with the developer on the developer carrier; and a toner for the developer on the developer carrier. In a developing device that changes a contact state between the developer and the toner in the toner storage unit by changing the density, thereby changing a state of taking in the toner into the developer, the developer storage unit includes: A rotating member that rotates in the same rotational direction as the developer carrier in contact with or in proximity to the developer carrier, and the rotating member is the most upstream in the surface movement direction of the developer carrier in the developer accommodating portion. It is characterized by being arranged at a position.

In the developing device of the first aspect, the developer is attracted to the surface of the developer carrier by the magnetic field generating means inside the developer carrier, and is conveyed along with the developer carrier. Further, in the opposed portion between the developer carrier and the rotating member, since the surfaces of both members move so as to be opposite to each other, the developer carried on the developer carrier and conveyed is A braking force is received by the rotating member. When the toner concentration of the developer decreases, the action of the magnetic force increases, and the above-described swiveling conveyance force increases. On the other hand, when the toner concentration increases, the conveying force decreases. This is because the ratio of the magnetic carrier in the developer increases or decreases. Therefore, as the toner concentration increases, the accompanying transporting force becomes relatively lower than the above-mentioned braking force, and there is generated a developer that cannot pass through the facing portion between the developer carrier and the rotating member. In this developing device, since the rotating member is provided at the most upstream position in the surface moving direction of the developer carrier in the developer accommodating portion, the developer carrier and the rotating member When the developer that cannot pass through the opposite portion of the toner occurs, the state of taking in the toner changes. As described above, the toner taking-in state changes due to the change in the toner concentration of the developer at the portion where the developer carrier and the rotating member are opposed to each other. The switching of the toner take-in is performed without waiting for the operation, and the responsiveness is extremely improved.

According to a second aspect of the present invention, in the developing device of the first aspect, the rotating member is made of a magnetic material.

In the developing device according to the second aspect, since the rotating member made of the magnetic material is magnetized and rotates, the developer is conveyed to the rotating member and stirred in the developer accommodating portion. In addition, since the surfaces of the developer carrier and the rotating member oppose each other so that the transport directions of the developer are opposite to each other, the developer passes between the developer carrier and the rotating member. The developer to be subjected to the transport force by the developer carrier and the transport force by the rotating member,
The frictional charging between the developers is promoted, and the charge rising property of the taken-in toner can be improved.

According to a third aspect of the present invention, in the developing device of the first or second aspect, the surface of the rotating member is roughened.

In the developing device according to the third aspect, the surface of the rotating member is roughened to increase the friction coefficient of the surface of the rotating member. When the friction coefficient of the surface of the rotating member increases, a greater braking force can be applied to the developer carried and conveyed on the surface of the developer carrier, and the frictional charging is more effectively performed. By changing the friction coefficient by changing the surface roughness of the rotating member, it becomes possible to obtain an optimum braking force matching the developer conveyed along with the developer carrier. It becomes possible to correspond to the developer possessed.

According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising: a latent image forming means for forming a latent image on a latent image carrier; and a developing device for developing the latent image on the latent image carrier to form a toner image. In the forming apparatus, the developing device according to claim 1, 2, or 3 is used as the developing device.

In the image forming apparatus according to the present invention, since the rotating member is provided at the most upstream position in the rotating direction of the developer carrying member in the developer accommodating portion, the toner can be prevented from suddenly changing the toner consumption. The responsiveness of switching between the take-in and the stop operation is improved, and development without density unevenness or the like can be performed.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a developing device of an electrophotographic copying machine (hereinafter, referred to as a printer) as an image forming apparatus will be described. FIG. 1 is a front view showing a schematic configuration of the printer according to the present embodiment. First, an outline of the printer will be described. The photosensitive drum 1 serving as a latent image carrier is uniformly charged by a charging roller 2 that contacts the photosensitive drum 1 and charges the surface thereof while being rotationally driven in the direction of arrow A in the figure, and then is subjected to optical writing. The scanning exposure is performed by the unit 3 based on the image information to form an electrostatic latent image on the surface. The electrostatic latent image formed on the photosensitive drum 1 is developed by a developing device 4 described later, and a toner image is formed on the photosensitive drum 1. Photoconductor drum 1
The transfer unit 5 transfers the toner image formed thereon from the paper cassette 6 to a paper feed roller 7 and a pair of registration rollers 8.
The image is transferred onto the sheet 9 conveyed through a and 8b. After the transfer is completed, the toner image is fixed on the sheet 9 by the fixing unit 10, and the sheet 9 is discharged outside the apparatus. The residual toner on the photosensitive drum 1 that has not been transferred is removed from the photosensitive drum 1 by the cleaning unit 11. Further, the residual charge on the photosensitive drum 1 is removed by the charge removing lamp 12.

FIG. 2 is an enlarged view showing a schematic configuration of the developing device 4. The developing device 4 is disposed on the side of the photosensitive drum 1 and has a support case 13 having an opening formed toward the photosensitive drum 1 and a developer 14 composed of toner and a magnetic carrier on the surface thereof. A developing sleeve 15 as a developer carrying member disposed so as to be partially exposed from the opening; and a first developing device which regulates an amount of the developer 14 carried on the developing sleeve 15 and conveyed. A first doctor blade 16 as an agent regulating member, and a developing sleeve 1
5 mainly comprises a developer accommodating member 17 provided so as to form a developer accommodating portion 17a of the developer 14 between the surface of the sleeve and the first doctor blade 16.

The support case 13 has a toner 18 inside.
A toner hopper 19 is formed as a toner storage unit for storing the toner. The toner hopper 19 includes a developer container 17a.
Has a toner supply opening 20 at a position adjacent to the developing sleeve 15 from the upstream side in the developer conveying direction and opposed to the surface of the developing sleeve 15 so that the stored toner 18 can be developed through the toner supply opening. Developer 1 on sleeve 15
4 and is taken in. In the toner hopper 19, a toner replenishing agitator 21 as a toner stirring member for sending out the toner 18 in the toner hopper 19 while stirring it toward the toner supply opening 20 is arranged. Support case 13 near toner supply opening 20
A protrusion 13a having an opposing surface 13b is formed at the bottom of. Note that the opposing surface 13b is
It is formed with a predetermined length so as to be inclined downward from the side toward the developing sleeve 15 side.

The first doctor blade 16 has its tip directed toward the center of the developing sleeve 15 and
A constant gap is kept between the outer peripheral surface of the first and the fifth peripheral surfaces. Further, a second doctor blade 22 as a second regulating member is provided at a portion of the developer containing member 17 which is located near the toner supply opening 20.

The developing sleeve 15 is driven to rotate in the direction of arrow B by driving means (not shown). Inside the developing sleeve 15, there is provided a magnet 15a as a magnetic field generating means, which is disposed at a fixed position relative to the developing device 4. Have. The developer 14 in the developer accommodating portion 17 a is the developer accommodating portion 1 of the magnet 15 a fixedly arranged inside the developing sleeve 15.
It is carried on the developing sleeve 15 by a magnet 15a located at a position facing 7a.

With the above configuration, the toner 18 sent out from the inside of the toner hopper 19 by the toner agitator 21 passes through the toner supply opening 20 and the developing sleeve 1.
5 is supplied to the developer 14 carried on the
It is carried to 7a. Then, the developer 14 in the developer accommodating portion 17a is carried by the developing sleeve 15 and is conveyed to a developing area opposed to the outer peripheral surface of the photosensitive drum 1, where the toner 1
Only 8 is electrostatically coupled to the electrostatic latent image formed on the photosensitive drum 1 to form a toner image on the photosensitive drum 1. Thereafter, the developer 1 on the developing sleeve 15 is
Reference numeral 4 denotes a developer container which is conveyed to the toner supply opening 20 side with the rotation of the developing sleeve 15, takes in new toner 18 sent out by the toner agitator 21 in the toner hopper 19 from the toner supply opening 20, 17
Return to a.

Incidentally, the developing device 4 according to this embodiment
Changes the contact state between the developer 14 and the toner 18 by the circulating operation of the developer 14 in the developer accommodating portion 17a to take in the toner 18 into the developer 14 on the developing sleeve 15 so that the toner density is self-contained. It is possible to control. And the developing device 4 according to the present embodiment
In order to effectively circulate the developer 14 in the developer accommodating portion 17a, a rotating member 23 described later is provided in the developer accommodating portion 17a. Hereinafter, the configuration inside the developer accommodating portion 17a and the movement of the developer 14 will be described.

In the developer accommodating portion 17a, a cylindrical rotating member 23, which is rotationally driven in the same rotational direction as the developing sleeve 15 by a driving means (not shown), is provided at the most upstream side in the rotational direction of the developing sleeve 15. It is arranged with a certain gap kept. Then, in the facing portion between the developing sleeve 15 and the rotating member 23, the surfaces are moved so that their surfaces are opposite to each other. Note that the rotating member 23 may be cylindrical or columnar. Further, the second doctor blade 22 has a free end in close contact with the outer peripheral surface of the rotating member 23 and a direction in which the flow of the layer of the developer 14 formed on the surface of the developing sleeve 15 is obstructed. It is arranged toward.

In the developer accommodating portion 17a, due to the presence of the rotating member 23, a braking force for stopping the transport of the developer 14 carried on the developing sleeve 15 acts to reduce the transport speed. Get up, toner supply opening 2
Near 0, the layer thickness of the developer 14 on the developing sleeve 15 increases. Then, when the toner concentration increases, the frictional force between the developers 14 decreases and the transport speed decreases, so that the layer thickness of the developer 14 on the developing sleeve 15 further increases, and the second doctor blade 22 Halts its progress. As a result, when the toner concentration of the developer 14 reaches a predetermined toner concentration, the toner supply opening 20
Is stopped by the developer 14 which has been prevented from proceeding by the doctor blade 22, and the taking in of the toner 18 is stopped.
In this way, the toner density of the developer 14 is always kept below a certain density.

On the other hand, when the toner 18 is consumed in the developing area and the toner concentration in the developer accommodating portion 17a decreases, the transport speed of the developer 14 increases due to the decrease in the toner concentration.
A force acts to pull back the thicker layer of the developer 14 on the developing sleeve 15, so that the developer 14 does not block the toner supply opening 20. As a result, the toner supply opening 20
Of the toner 18 is started again, and the developer 1
The toner density of No. 4 is always kept at a certain density or higher.

Next, the operation when the toner density changes will be described in more detail with reference to the drawings. FIG. 3 shows the developing sleeve 15 and the rotating member 23, and the developer 14 at a portion sandwiched between them. The developer 14 is attracted to the developing sleeve 15 by a magnet 15 a fixed inside the developing sleeve 15, and is conveyed together with the developing sleeve 15. At the same time, the rotating member 23 receives a braking force. When the toner density of the developer 14 decreases, the action of the magnetic force increases, and the accompanying transporting force increases. Conversely, as the toner concentration increases, the conveying force decreases. This is because the ratio of the magnetic carrier in the developer increases or decreases. Accordingly, the developer 14 that cannot pass through this portion is generated because the entraining conveyance force becomes relatively low with respect to the braking force due to the increase in the toner concentration.
As shown by a dotted line in FIG. 3, the swelling is prevented by the second doctor blade 22.

According to the mechanism described above, the toner taking-in state changes due to the change in the toner concentration of the developer 14 in the area sandwiched between the developing sleeve 15 and the rotating member 23, so that the toner concentration of the entire developer changes. The switching of the toner take-in is performed without waiting, and the responsiveness is extremely improved. This prevents problems such as a decrease in image density when the amount of toner consumption rapidly increases on the toner consumption side and a background stain or excessive density when the amount of toner consumption rapidly decreases. Image formation with high image quality can be performed.

The rotating member 23 may be made of a magnetic material. Since the rotating member 23 made of a magnetic material is magnetized and rotates, the developer accommodating portion 1 is rotated.
The developer 14 is conveyed to the rotating member 23 in the inside 7a and is stirred. Further, in the facing portion between the developing sleeve 15 and the rotating member 23, the surface moves so that the transport directions of the developer 14 are opposite to each other.
The developer 14 passing between the developing member 15 and the rotating member 23 receives the stress of the transporting force of the developing sleeve 15 and the transporting force of the rotating member 23, so that the frictional charging between the developers 14 is promoted, and the toner 18 Of the toner can be improved. As the rotating member 23 made of a magnetic material, for example, a member obtained by plating an iron core with nickel, a magnetic stainless steel, or the like can be used.

By the way, in order to establish the above mechanism, the developer must properly change the frictional force in the magnetic field due to the change in the toner concentration. Additives are mixed. Therefore, there are various types having different widths of change in toner density and different magnitudes of frictional force. In order to make full use of the developing device according to the present embodiment with any type of developer, it is necessary to adjust the developing device to a device suitable for the characteristics of the developer.

Therefore, as a result of intensive studies by the present inventors, it has been found that various developers can be accommodated by changing the surface roughness of the rotating member 23. By performing roughening on the surface of the rotating member 23, the friction coefficient of the surface of the rotating member 23 increases. When the friction coefficient of the surface of the rotating member 23 increases, a greater braking force can be applied to the developer 14 carried and conveyed on the surface of the developing sleeve 15, and the frictional charging is more effectively performed. By changing the surface roughness of the rotating member 23, the friction coefficient is changed, and an optimum braking force matching the developer conveyed along with the developing sleeve 15 can be obtained. Specifically, the surface of the rotating member 23 was subjected to a roughening process such as sandblasting so that the surface roughness was optimal for the developer used.

[0028]

According to the first to third aspects of the present invention, the toner taking-in state changes due to the change in the toner concentration of the developer at the portion where the developer carrying member and the rotating member face each other. There is an excellent effect that the responsiveness of the switching between the toner taking-in and the stopping operation with respect to the change in is improved, and higher image quality can be realized.

In particular, according to the second aspect of the present invention, the rotating member made of the magnetic material is magnetized and rotates.
In the developer accommodating section, the developer is conveyed to the rotating member and stirred. Further, the developer passing between the developer carrying member and the rotating member receives the conveying force of the developer carrying member and the conveying force of the rotating member, so that frictional charging between the developers is promoted, There is an excellent effect that the charge rising property of the taken-in toner can be improved.

In particular, according to the third aspect of the present invention, the surface of the rotating member is roughened to increase the coefficient of friction on the surface of the rotating member, and is conveyed while being carried on the surface of the developer carrying member. There is an excellent effect that a greater braking force is applied to the developer and triboelectric charging is more effectively performed. By changing the friction coefficient by changing the surface roughness of the rotating member, it becomes possible to obtain an optimum braking force matching the developer conveyed along with the developer carrier. There is also an excellent effect that it is possible to correspond to the developer possessed.

According to the fourth aspect of the present invention, a high-response developing device is provided for switching between the toner taking-in operation and the stopping operation in response to a rapid change in the amount of toner consumption. There is an excellent effect that you can.

[Brief description of the drawings]

FIG. 1 is a front view illustrating a schematic configuration of a printer according to an embodiment.

FIG. 2 is a schematic configuration diagram of a developing device of the printer.

FIG. 3 is a diagram illustrating a developing sleeve 15 and a rotating member 23, and a portion of the developer 14 interposed therebetween.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum 4 developing device 13 support case 14 developer 15 developing sleeve 15a magnet 16 first doctor blade 17 developer accommodating member 17a developer accommodating portion 18 toner 19 toner hopper 20 toner supply opening 21 toner replenishing agitator 22 second Doctor blade 23 rotating member

Claims (4)

[Claims] 1. A developer carrier having a magnetic field generating means therein for carrying and transporting a two-component developer containing a toner and a magnetic carrier, and a developer carrier carried and transported by the developer carrier. A regulating member for regulating the amount of the developer, a developer accommodating portion for accommodating the developer scraped by the regulating member, and the developer on the developer carrying member adjacent to the developer accommodating portion and on the developer carrying member And a toner storage portion for storing toner so as to be taken in contact with the toner, and a contact state between the developer and the toner in the toner storage portion due to a change in the toner concentration of the developer on the developer carrying member. In the developing device that changes the state of taking in the toner into the developer by changing
A rotating member that rotates in the same rotational direction as the developer carrier in contact with or in proximity to the developer carrier, and the rotating member is the most upstream in the surface movement direction of the developer carrier in the developer accommodating portion; A developing device disposed at a side position. 2. The developing device according to claim 1, wherein said rotating member is made of a magnetic material. 3. The developing device according to claim 1, wherein a surface of said rotary member is roughened. 4. An image forming apparatus comprising: a latent image forming means for forming a latent image on a latent image carrier; and a developing device for developing the latent image on the latent image carrier to form a toner image. An image forming apparatus using the developing device according to claim 1, 2, or 3 as a developing device.