JP2005134767A - Developing device, processing cartridge, and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a developing device for sufficiently stirring newly replenished toner and developer while preventing an increase in the rotating torque of a stirring/conveying means for stirring/ conveying the developer and toner supplied into the developer storing part in the developing device, in order to prevent troubles caused by deficient electrification of toner. <P>SOLUTION: In the developing device 5Y, a magnet 58Y that is a magnetic field generating means for generating a magnetic field is disposed on the upper part of a stirring chamber 54Y which is an area where developer is stirred/conveyed by a second conveying screw 56Y being the developer stirring/conveying means in a developer storing container 57Y. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a developing device using a two-component developer containing toner and a magnetic carrier, a process cartridge, and an image forming apparatus using these.

In a developing device using a two-component developer containing this type of non-magnetic toner (hereinafter referred to as “toner”) and a magnetic carrier (hereinafter referred to as “carrier”), if the image is continuously output, the toner in the developer in the developing device Is consumed in the development area. Then, the toner is replenished from the toner replenishing port according to the consumed toner amount. At this time, the replenished toner and developer are agitated and conveyed in the developing device.
FIG. 12 is a schematic configuration diagram of a developer container that stirs and conveys developer in a conventional developing device. The developer accommodating portion includes a first developer agitating / conveying means (hereinafter referred to as a first screw) 55 having a rotation shaft parallel to a developing sleeve (not shown), and a second developer agitating / conveying means ( (Hereinafter referred to as a second screw) 56. The first screw 55 conveys the developer in the direction of arrow A while stirring the developer, and supplies the developer to the developing sleeve. The second screw 56 stirs and conveys the developer in the direction of arrow B.
Further, a partition plate is provided between the first screw 55 and the second screw 56, and constitutes a developing chamber 53 and a stirring chamber 54. The both ends of the partition plate are openings that connect the developing chamber 53 and the stirring chamber 54. The developer in the stirring chamber 54 is conveyed in the direction of arrow B by the second screw 56, and is conveyed to the developing chamber 53 through the opening at the end of the developer accommodating portion. The developer in the developing chamber 53 is conveyed in the direction of arrow A while being supplied to the developing sleeve, and is conveyed to the stirring chamber 54 through the opening at the end of the developer accommodating portion. Thus, the developer circulates in the developer accommodating portion.
In the developer accommodating portion of FIG. 12, the toner replenished from the toner replenishing port 62 is conveyed in the direction of arrow B while being agitated with the developer by the second screw 56. The developer containing the toner conveyed to the end of the developer accommodating portion is supplied to a developing sleeve (not shown) while being conveyed in the direction of arrow A by the first screw 55 and is conveyed to the developing region.
In the case of the developing device as described above, the toner replenished from the toner replenishment port 62 to the upper side of the second screw 56 is small and light in particle size, so that the toner is transported on the developer, and a toner concentration portion is formed above the developer. Form. For this reason, it is difficult to sufficiently stir the toner and the developer. If the replenished toner and the developer are not sufficiently stirred, all of the replenished toner cannot come into contact with the carrier surface in the developer. As a result, there is also toner that is conveyed through the developer accommodating portion while being rubbed only with the toner, supplied to the developing sleeve, and further conveyed to the developing region.
When this process is repeated, the toner in the developer has a charge of around 0 or charged with a polarity opposite to the desired polarity (plus when the desired polarity is negative). There are things to do. Such toner for which sufficient chargeability cannot be ensured may cause white background fog on the image and toner scattering in the machine.

  In order to prevent the above shortage of stirring, as a new stirring means, a diffusion brush provided near the second screw or a screw provided with a paddle for stirring has been proposed (see, for example, Patent Document 1). . However, if a new stirring means for applying a mechanical force in the rotational direction of the second screw is provided, the transport speed is slowed although the stirring is performed because of the movement in the rotational direction.

  Accordingly, a magnetic stirrer for generating a magnetic field is provided on the side or lower side of the second transport screw so that the new stirrer has little influence on the transport speed, and a new stirrer is proposed. (See Patent Document 2).

Utility Model Registration No. 2506225 JP 2000-89550 A

However, if the magnetic field generating means is provided below or on the side of the screw, the distance from the toner concentration portion above the developer is large. Therefore, a large magnetic force is required to perform sufficient stirring. Further, a strong magnetic field line passes through not the toner concentration portion but the developer concentration portion. As a result, a force to stay in many carriers in the developer near the magnetic field generating means is applied. As a result, a larger force is required to carry the sheet, and the rotational torque increases.
The present invention has been made in view of the above problems, and an object of the present invention is to provide a toner and a developer replenished in the developer accommodating portion in order to prevent problems caused by insufficient charging of the toner. Another object of the present invention is to provide a developing device capable of sufficiently stirring while preventing an increase in rotational torque of the stirring / conveying means.

In order to achieve the above object, the invention of claim 1 includes a developer carrying member that carries a developer containing nonmagnetic toner and a magnetic carrier on the surface and moves to the development area, and the nonmagnetic toner is replenished. A developer container that stores the developer supplied through the mouth and that supplies the developer carrier, and the developer and the non-magnetic toner that are agitated by the rotation in the developer container and transported in the axial direction. A developing device having a developer agitating / conveying means is characterized in that a magnetic field generating means for generating a magnetic field is provided above a developer agitating / conveying area by the developer agitating / conveying means.
According to a second aspect of the present invention, in the developing device of the first aspect, the magnetic pole forming portion of the magnetic field generating means is provided facing downward.
According to a third aspect of the present invention, in the developing device of the second aspect, two or more magnetic field generating means are provided, and the magnetic poles of the magnetic pole forming portions of the magnetic field generating means have the same polarity.
According to a fourth aspect of the present invention, in the developing device according to the first, second, or third aspect, the developer moves downward about the rotation axis of the agitating / conveying means in the agitating / conveying region. The magnetic field generating means is provided so as to face only a region where the magnetic field is present.
According to a fifth aspect of the present invention, in the developing device according to the first, second, third, or fourth aspect, the developer above the rotation axis in a cross section perpendicular to the rotation axis of the developer agitating / conveying means. The magnetic pole forming portion is formed so that the area of the magnetic pole forming portion of the magnetic field generating means becomes wider as it goes downstream in the moving direction.
According to a sixth aspect of the present invention, there is provided a process cartridge that integrally supports the image carrier and at least the developing device and is detachable from the main body of the image forming device, wherein the developing device is the first, second, third, 4 or 5 developing device.
According to a seventh aspect of the present invention, there is provided an image carrier, a latent image forming unit that forms a latent image on the image carrier, a developing unit that develops the latent image on the image carrier and forms a toner image, An image forming apparatus comprising a transfer unit that transfers a toner image on the image carrier onto a transfer material, wherein the developing unit of claim 1, 2, 3, 4, or 5 is used as the developing unit. To do.

In the developing device according to the first to seventh aspects, since the magnetic field generating means for attracting the magnetic carrier in the developer is provided above the agitation / conveyance area, the spikes of the developer are formed above the agitation / conveyance area. . As a result, the newly replenished toner that tends to concentrate on the upper portion of the developer and the ears of the developer come into contact with each other, so that the toner and the magnetic carrier can be efficiently brought into contact with each other.
Further, since the magnetic field generating means is provided above the stirring / conveying area, the toner concentration portion formed on the developer and the magnetic field generating means are compared with those provided with the magnetic field generating means on the side or below. The distance can be shortened. Since the distance between the toner concentrating part and the magnetic field generating means is short, the length of the developer ears may be shorter than that provided with the magnetic field generating means on the side or below the stirring / conveying area, and strong magnetic force is generated. do not need. As a result, the developer attracted by magnetic force can be suppressed to a minimum, and since the hindrance to the movement of the developer in the transport direction is small, an increase in the rotational torque of the developer agitating / conveying means can be suppressed.

  According to the first to seventh aspects of the invention, since the toner and the magnetic carrier can be efficiently contacted, the developer can be sufficiently stirred, and problems caused by insufficient charging of the toner can be prevented. In addition, the developer attracted by the magnetic force can be minimized, and since there is little hindrance to the movement of the developer in the transport direction, it is possible to prevent the increase in the rotational torque of the developer agitating / conveying means.

Hereinafter, an electrophotographic printer (hereinafter simply referred to as a printer) will be described as a first embodiment of an image forming apparatus to which the present invention is applied.
First, the basic configuration of the printer will be described. FIG. 1 is a schematic configuration diagram of the printer. In the figure, the printer 100 includes four process cartridges 6Y, M, C, and K for generating toner images of yellow, magenta, cyan, and black (hereinafter referred to as Y, M, C, and K). Yes. These use Y, M, C, and K toners of different colors as the image forming material, but the other configurations are the same and are replaced when the lifetime is reached. Taking a process cartridge 6Y for generating a Y toner image as an example, as shown in FIG. 2, a drum-shaped photosensitive member 1Y as an image carrier, a drum cleaning device 2Y, a charge eliminating device (not shown), and a charging device 4Y. And a developing device 5Y. The process cartridge 6Y can be attached to and detached from the printer 100 main body, so that consumable parts can be replaced at a time.

  The charging device 4Y uniformly charges the surface of the photoreceptor 1Y that is driven to rotate clockwise in the drawing by a driving unit (not shown). The surface of the uniformly charged photoreceptor 1 </ b> Y is exposed and scanned by the laser beam L to carry an electrostatic latent image for Y. The Y electrostatic latent image is developed into a Y toner image by the developing device 5Y using Y toner. The Y toner image is intermediately transferred onto an intermediate transfer belt 8 as an intermediate transfer member. The drum cleaning device 2Y removes the toner remaining on the surface of the photoreceptor 1Y after the intermediate transfer process. Further, the static eliminator neutralizes residual charges on the photoreceptor 1Y after cleaning. By this charge removal, the surface of the photoreceptor 1Y is initialized and prepared for the next image formation. In the other process cartridges 6M, C, and K, M, C, and K toner images are similarly formed on the photoreceptors 1M, C, and K, and are intermediately transferred onto the intermediate transfer belt 8.

  In FIG. 1 described above, an exposure device 7 serving as a latent image forming unit is disposed below the process cartridges 6Y, 6M, 6C, and 6K in the drawing. The exposure device 7 irradiates the respective photosensitive members in the process cartridges 6Y, 6M, 6C, and 6K with the laser light L emitted based on the image information to perform exposure. By this exposure, electrostatic latent images for Y, M, C, and K are formed on the photoreceptors 1Y, 1M, 1C, and 1K. The exposure device 7 irradiates the photoconductor with a laser beam (L) emitted from a light source through a plurality of optical lenses and mirrors while scanning with a polygon mirror rotated by a motor.

  On the lower side of the exposure apparatus 7 in the figure, paper supply means having a paper storage cassette 26, a paper supply roller 27 incorporated therein, a registration roller pair 28, and the like are disposed. The paper storage cassette 26 stores a plurality of transfer papers P as transfer materials, and a paper feed roller 27 is in contact with each uppermost transfer paper P. When the paper feeding roller 27 is driven to rotate counterclockwise in the drawing by a driving means (not shown), the uppermost transfer paper P is fed toward the rollers of the registration roller pair 28 as a timing roller pair. . The registration roller pair 28 rotates so as to sandwich the transfer paper P. However, the registration roller pair 28 temporarily stops the rotation as soon as it is sandwiched. Then, the transfer paper P is sent out toward a later-described secondary transfer nip at an appropriate timing. In the paper feeding unit having such a configuration, a conveying unit is configured by a combination of the paper feeding roller 27 and the registration roller pair 28. This transport means transports the transfer paper P from a paper storage cassette 26 serving as a storage means to a secondary transfer nip described later.

  Above the process cartridges 6Y, 6M, 6C, and 6K, an intermediate transfer unit 15 that moves the intermediate transfer belt 8 endlessly while stretching is disposed. In addition to the intermediate transfer belt 8, the intermediate transfer unit 15 includes four primary transfer bias rollers 9Y, M, C, and K, a cleaning device 10, and the like. A secondary transfer backup roller 12, a cleaning backup roller 13, a tension roller 14 and the like are also provided. The intermediate transfer belt 8 is endlessly moved in the counterclockwise direction in the figure by the rotational drive of at least one of the rollers while being stretched around these three rollers. The primary transfer bias rollers 9Y, 9M, 9C, and 9K hold the intermediate transfer belt 8 that moves endlessly between the photoreceptors 1Y, 1M, 1C, and 1K, thereby forming primary transfer nips. . The primary transfer bias roller applies a transfer bias having a reverse polarity (for example, plus) to the toner to the back surface (loop inner peripheral surface) of the intermediate transfer belt 8. All of the rollers except the primary transfer bias rollers 9Y, M, C, and K are electrically grounded. The intermediate transfer belt 8 sequentially passes through the primary transfer nips for Y, M, C, and K along with the endless movement thereof, and Y, M, and C on the photoreceptors 1Y, M, C, and K , K toner images are superimposed and primarily transferred. As a result, a four-color superimposed toner image (hereinafter referred to as a four-color toner image) is formed on the intermediate transfer belt 8.

  The secondary transfer backup roller 12 sandwiches the intermediate transfer belt 8 between the secondary transfer roller 19 and forms a secondary transfer nip. The four-color toner image formed on the intermediate transfer belt 8 is transferred to the transfer paper P at the secondary transfer nip. Untransferred toner that has not been transferred onto the transfer paper P adheres to the intermediate transfer belt 8 after passing through the secondary transfer nip. This is cleaned by the cleaning device 10.

  In the secondary transfer nip, the transfer paper P is sandwiched between the intermediate transfer belt 8 and the secondary transfer roller 19 whose surfaces move in the forward direction, and is conveyed in the opposite direction to the registration roller pair 28 side. The When the transfer paper P sent out from the secondary transfer nip passes between the rollers of the fixing device 20, the four-color toner image transferred to the surface is fixed by heat and pressure. Thereafter, the transfer paper P is discharged out of the apparatus through a pair of paper discharge rollers 29. A stack unit 30 is formed on the upper surface of the printer body, and the transfer paper P discharged outside the apparatus by the discharge roller pair 29 is sequentially stacked on the stack unit 30.

  In FIG. 1 described above, a bottle container 31 is disposed between the intermediate transfer unit 15 and the stack portion 30 located above the intermediate transfer unit 15. The bottle container 31 stores toner bottles 32Y, 32M, 32C, and 32K containing Y, M, C, and K toners, respectively. The toner bottles 32Y, 32M, 32C, and 32K are installed on the bottle container 31 so as to be placed from above for each toner color. The Y, M, C, and K toners in the toner bottles 32Y, 32M, 32C, and 32K are appropriately replenished to the developing devices of the process cartridges 6Y, 6M, 6C, and 6K, respectively, by a toner conveyance device described later. These toner bottles 32Y, 32M, 32C, and 32K are detachable from the main body of the printer 100 independently of the process cartridges 6Y, 6M, C, and K.

  FIG. 3 is a perspective view of a toner replenishing device 40Y that replenishes toner from the toner bottle 32Y to the developing device 5Y. New toner filled in the toner bottle 32Y is supplied to the toner hopper 48Y of the toner supply device 40Y. The toner stored in the toner hopper 48Y is replenished to the developing device 5Y when the toner detecting means (not shown) in the developing device 5Y determines that the toner concentration in the developing device 5Y is low. The toner replenished to the developing device 5Y passes from the toner hopper 48Y through the transport pipe 43Y, and is supplied from the opening 45Y of the transport pipe 43Y to the replenishment port 62Y on the developing device side.

Next, the configuration of the developing device 5Y in the process cartridge 6Y will be described.
As shown in FIG. 2, the developing device 5Y includes a developing sleeve 51Y as a developer carrying member that carries and conveys a two-component developer containing a carrier and toner on the surface. A doctor 52Y is provided as a developer regulating member that regulates the layer thickness of the developer carried and conveyed on the developing sleeve 51Y.
On the upstream side of the developer conveyance direction of the doctor 52Y, a developer accommodation that accommodates the developer supplied to the development sleeve 51Y and the developer regulated by the doctor 52Y without being conveyed to the development area facing the photoreceptor 1Y. A portion 57Y is formed. Inside the developer accommodating portion 57Y is a partition plate, which is divided into a developing chamber 53Y located closer to the developing sleeve 57Y and an agitating chamber 54Y located farther from the developing sleeve. In the developing chamber 53Y and the stirring chamber 54Y, a developer containing toner and a carrier is accommodated.
The developing chamber 53Y is a first developer agitating / conveying means that agitates and conveys the developer and toner in the developer accommodating portion 57Y in parallel with the developing sleeve 51Y and supplies the developer to the developing sleeve 51Y. One screw 55Y is provided. The agitating chamber 54Y is provided with a second screw 56Y as a second developer / agitating and conveying means for agitating and conveying the developer in a direction parallel to the first screw 55Y and facing the conveying direction of the first screw 55Y. It has been. The developer is circulated in the developer accommodating portion 57Y while being stirred by the first screw 55Y and the second screw 56Y.

  Next, the operation of this developing device will be described. In the developing device 5Y, a developer layer is formed on the developing sleeve 51Y. Further, the toner is taken into the developer from the developer accommodating portion 53Y by the movement of the developer layer conveyed by the rotation of the developing sleeve 51Y. The toner is taken in so that the developer is within a predetermined toner density range. The toner taken in the developer is charged by frictional charging with the carrier. The developer containing charged toner is supplied to the surface of the developing sleeve 51Y having a magnetic pole inside and is carried by magnetic force. The developer layer carried on the developing sleeve 51Y is conveyed in the direction of the arrow as the developing sleeve 51Y rotates. On the way, after the thickness of the developer layer is regulated by the doctor 52Y, it is transported to the developing area facing the photoreceptor 1Y. In the development area, development based on the latent image formed on the photoreceptor 1Y is performed. The developer layer remaining on the developing sleeve 51Y is conveyed to the upstream portion in the developer conveying direction of the developer accommodating portion 53Y as the developing sleeve 51Y rotates.

Next, a magnet 58Y, which is a magnetic field generating means, which is a feature of the present invention, is installed above a stirring chamber 54Y, which is a developer stirring / conveying area, having a second screw 56Y, which is a developer stirring / conveying means. The configuration will be described. Note that the magnet used in this embodiment may be either an electromagnet or a permanent magnet. Further, the magnet 58Y is installed downstream of the toner supply port 62Y in the conveying direction by the second screw 56Y.
FIG. 4A is a perspective view of the developer containing portion 57Y with the magnet 58 installed as seen through the upper wall surface. FIG. 4B is a perspective view showing a state where the magnet 58 of FIG. 4A is not installed. A black-colored portion at the top of the second screw 56Y is a toner concentration portion 60Y where toner concentrates.
5A and 5B are cross-sectional views of the developer accommodating portion 57Y for comparing the developing device of the present embodiment provided with a magnet with a conventional developing device not provided with a magnet.

  In the conventional configuration in which stirring is performed only with a screw that does not use a magnet, the toner replenished from the replenishing port 62Y has a toner concentration portion 60Y at the top of the developer as shown in FIGS. 4B and 5B. The developer is not sufficiently stirred with the developer. Although stirring is performed as a whole, it is difficult to stir to a fine place such as a small toner lump. If the agitation is not sufficiently performed, the toner and the carrier are less likely to come into contact with each other, and the toners often rub against each other. The charge of the toner becomes uneven and the charge distribution varies.

On the other hand, when the magnet 58Y is provided above the conveying screw, the developer replenished with toner at the toner replenishing port 62Y is attracted to the magnet 58Y as shown in FIGS. 4 (a) and 5 (a). No. 59Y is formed.
The toner replenished at the replenishing port 62Y falls on the top of the developer, and its particles are small and light, so that the toner concentration portion 60Y is formed on the top of the developer and conveyed. When the toner is conveyed below the magnet 58Y, the developer under the toner concentration portion 60Y is attracted upward, and the toner and the developer are agitated. Further, the small toner lump is pressed against the developer ear 59Y, and the lump is broken and scattered and mixed. At substantially the same time as this step, the developer that has formed the ears 59Y by the magnetic force of the magnet 58Y is also transported downstream of the transport direction together with the dispersed toner by the blades of the screw.
With such a configuration, the toner is less solid, the toner is uniformly dispersed in the developer, and the opportunity for the toner to come into contact with the carrier is increased. Further, the charge distribution of the toner becomes sharp and partial transfer omission does not occur.

  Here, the magnet 58Y is installed so as to face the upper surface of the developer on the downstream side in the transport direction from the supply port 62Y where the toner tends to concentrate, so that the developer below the toner concentration portion is attracted upward. Increases the chance of contact with developer. Further, since the toner concentrating portion and the magnet 58Y are close to each other, a magnetic force as large as a configuration in which the magnet is installed on the side or the lower side of the screw is not required. By forming the developer head 59Y with a relatively weak magnetic force in this way, the force to separate the ear 59Y from the magnet 58Y by the screw wings is small, and the amount of developer attracted is small. An increase in rotational torque can be prevented.

The magnet 58Y is preferably installed with the magnetic pole facing downward.
6 (a) and 6 (b) are explanatory diagrams for comparing the magnet 58Y with the magnetic pole facing downward and the magnet 58Y with the magnetic pole facing sideways. The arrow in the figure indicates the developer transport direction. When the magnetic pole is directed to the side as shown in FIG. 6B, the magnetic lines of force are parallel to the upper surface of the developer, and the developer ear 59Y and the toner cannot be efficiently contacted. On the other hand, as shown in FIG. 6A, by making the upper surface of the developer and the magnetic field lines perpendicular to each other, the developer ear 59Y to be formed is also perpendicular, so that the toner can be dispersed most efficiently.

Further, two or more magnets 58Y may be arranged side by side. In this case, it arrange | positions so that all the magnetic poles which face the downward direction of each magnet 58Y may become the same polarity.
FIGS. 7A and 7B are explanatory diagrams for comparing the shape of the magnetic field lines and the developer ear 59Y to be formed, in which the magnetic poles directed downward of adjacent magnets are the same and different. is there. The arrow in the figure is the developer transport direction. When the magnetic poles directed downward are different, as shown in FIG. 7B, the magnetic field lines of adjacent magnets are attracted and connected to each other, and a portion where the ear 59Y is not perpendicular to the developer is generated, and the efficiency of stirring is increased. Deteriorate. On the other hand, if the magnetic poles directed downward are the same, the magnetic field lines of adjacent magnets do not repel each other and are not connected as shown in FIG. As a result, the developer head 59Y to be formed becomes perpendicular to the lower surface of the magnet 58, and diffusion can be performed efficiently.

Further, the magnet 58Y may be installed so as to face only the region where the developer is moving downward around the rotation axis of the second screw 56Y in the stirring chamber 54Y. This is relative to the conveyance direction of the second screw 56Y, when the rotation direction of the second screw is counterclockwise, it is only on the left side of the rotation axis, and when the rotation direction is clockwise rotation, it is only relative to the rotation axis. The magnet 58Y is installed only in the right region.
This configuration will be described with reference to FIG. In FIG. 8, since the second screw 56Y rotates counterclockwise in the second screw, the magnet 58Y is installed only on the left side of the rotation axis. Since the second screw 56Y rotates counterclockwise, the replenished toner concentrated portion is often transported to the downstream side in the transport direction and at the same time moves to the left with respect to the transport direction of the second screw 56Y. For this reason, by providing a magnet only on the left side where more toner is present with respect to the rotating shaft, the toner and the carrier can be efficiently contacted, and the size can be reduced, and the cost can be reduced.

Furthermore, the magnetic pole area of the magnet 58Y becomes larger as it goes downstream in the developer movement direction above the rotation axis in the cross section perpendicular to the rotation axis of the second screw 56Y. The shape may be formed. This increases the shape of the magnet 58Y toward the left side of the stirring chamber 54Y when the rotation direction of the second screw 56Y is counterclockwise with respect to the conveying direction of the second screw 56Y. On the contrary, when the rotation direction of the second screw is clockwise, the shape of the magnet 58Y is formed so that the area of the magnetic pole is increased toward the right side of the stirring chamber 54.
This configuration will be described with reference to FIG. In FIG. 9, since the second screw 56Y rotates counterclockwise, the area increases toward the left side and decreases toward the opposite side. The amount of toner supplied from the replenishing port 62Y increases as the second screw 56Y rotates to the left in the drawing on the upper surface of the developer. Therefore, by increasing the area of the magnet 58Y toward the left side in the figure and decreasing toward the right side, the toner can efficiently contact the carrier, can be reduced in size, and the cost can be reduced.
In addition, as the shape of the magnet 58Y described above, a shape obtained by dividing an existing shape as shown in FIG. 10 may be used. By using an existing magnet, it is not necessary to prepare a new standard for the shape, so that it can be easily implemented and the cost can be reduced.

As described above, in the developing device of this embodiment, in the developing device 5Y, the magnet 58Y, which is a magnetic field generating means for generating a magnetic field, is provided above the stirring chamber 54Y having the second screw 56Y. By providing the magnet 58Y above the stirring chamber 56Y, the newly replenished toner that tends to concentrate on the upper portion of the developer comes into contact with the ears of the developer, so that the toner and the magnetic carrier can be efficiently stirred. .
Further, since the magnet 58Y is provided near the toner concentration part 60Y, the magnet 58Y and the toner are compared with those provided with the magnet 58Y away from the toner concentration part 60Y, such as on the side or under the stirring chamber 54Y. The distance to the concentrated portion 60Y is shortened. Since the distance between the magnet 58Y and the toner concentration portion 60Y is short, the length of the developer spike may be short, and the magnet 58Y does not require a strong magnetic force. As a result, the developer attracted by the magnetic force can be suppressed to a minimum, and since the hindrance to the movement of the developer in the transport direction is small, an increase in the rotational torque of the second screw 56Y can be suppressed.
Further, the magnetic pole of the magnet 58Y in the present embodiment is installed facing downward. With such a configuration, the developer ear 59Y can be formed perpendicular to the upper surface of the developer, and the toner and the developer can be contacted more efficiently. Stirring can be sufficiently performed by efficiently bringing the toner and the developer into contact with each other.
When two or more magnets 58Y are provided in the present embodiment, the polarities of the magnetic poles directed downward from the magnets 58Y are all set to the same polarity. With such a configuration, the magnetic lines of force of adjacent magnets 58Y are not connected, and the formed developer spikes 59Y can be formed perpendicular to the magnetic pole surface. Stirring can be performed.
In the present embodiment, the magnet 58Y is provided so as to face only the region of the stirring chamber 54Y where the developer is moving downward about the rotation axis of the second screw 56Y. . With such a configuration, the toner can be efficiently contacted with the carrier, the size can be reduced, and the cost can be reduced.
In the present embodiment, the area of the magnetic pole of the magnet 58Y becomes wider as it goes downstream in the developer movement direction above the rotation axis in the cross section perpendicular to the rotation axis of the second screw 56Y. The magnet 58Y is formed so as to go. With such a configuration, the toner can be efficiently contacted with the carrier, the size can be reduced, and the cost can be reduced.

Next, modified examples to which the present invention can be applied will be described.
FIG. 11 is a perspective view of a developer accommodating portion in which a rod-like magnet 58Y that is long in the developer conveying direction is installed instead of installing a plurality of magnets as in the above-described embodiment.
By using the bar-shaped magnet 58Y, it is possible to reduce the labor in the manufacturing process of installing a plurality of magnets while obtaining the same effect as that obtained by installing a plurality of magnets.
Further, as shown in FIG. 11, the magnet is installed only on the left side of the rotation axis because the rotation direction of the second screw 56Y is viewed from above, that is, the second screw 56Y is rotated counterclockwise in the figure. May be.

1 is a schematic configuration diagram of a printer according to an embodiment. FIG. FIG. 3 is a perspective view of a replenishing device from a toner bottle to a developing device. The perspective view of a developer accommodating part. Sectional drawing of a developer accommodating part. Direction of magnetic pole and shape of developer spike. The direction of the magnetic poles of adjacent magnets and the shape of the developer spike. The top view of a developer accommodating part. The perspective view of the developer accommodating part characterized by the shape of a magnet. Example of magnet shape. The perspective view of the developer accommodating part which installed the rod-shaped magnet. The top view of the conventional developer accommodating part.

Explanation of symbols

1Y, M, C, K photoconductor 2Y, M, C, K drum cleaning device 4Y, M, C, K charging device 5Y, M, C, K developing device 6Y, M, C, K process cartridge 7 exposure device 8 Intermediate transfer belt 9Y, M, C, K Primary transfer bias roller 10 Cleaning device 12 Secondary transfer backup roller 13 Cleaning backup roller 14 Tension roller 15 Intermediate transfer unit 19 Secondary transfer roller 20 Fixing device 26 Paper storage cassette 27 Paper feed roller 28 Registration roller pair 30 Stack unit 31Y, M, C, K Bottle container 32Y, M, C, K Toner bottle 40Y Toner transport device 41Y Toner transport wagon 45Y Transport pipe opening 48Y Toner hopper 51Y Developer sleeve 52Y Doctor 52Y
53Y Developing chamber 54Y Stirring chamber 55Y First screw 56Y Second screw 57Y Developer container 58Y Magnet 59Y Developer head 60Y Toner concentration portion 62Y Toner supply port

Claims (7)

A developer carrying member that carries a developer containing a non-magnetic toner and a magnetic carrier on the surface and moves to the development area;
A developer containing portion for containing a developer supplied with non-magnetic toner through a replenishing port and supplied to the developer carrying member;
In the developing device having a developer agitating / conveying means for agitating the developer and the nonmagnetic toner by the rotation in the developer accommodating portion and conveying the developer in the axial direction.
A developing device comprising magnetic field generating means for generating a magnetic field above a developer agitating / conveying area by the developer agitating / conveying means. The developing device according to claim 1.
A developing device comprising a magnetic pole forming portion of the magnetic field generating means facing downward. The developing device according to claim 2.
2. A developing device according to claim 1, wherein two or more magnetic field generating means are provided, and the magnetic poles of the magnetic pole forming portions of each magnetic field generating means have the same polarity. The developing device according to claim 1, 2 or 3,
The magnetic field generating means is provided so as to face only the area where the developer is moving downward around the rotation axis of the stirring / conveying means in the stirring / conveying area. Development device. The developing device according to claim 1, 2, 3 or 4,
In the cross section perpendicular to the rotation axis of the developer agitating / conveying means, the area of the magnetic pole forming portion of the magnetic field generating means increases as it moves downstream in the developer moving direction above the rotation axis. A developing device characterized in that the magnetic pole forming portion is formed so as to become. In the process cartridge that integrally supports the image carrier and at least the developing device and is detachable from the image forming apparatus main body,
6. A process cartridge according to claim 1, wherein the developing device is the developing device according to claim 1, 2, 3, 4 or 5. An image carrier, latent image forming means for forming a latent image on the image carrier, developing means for developing a latent image on the image carrier to form a toner image, and a toner image on the image carrier. In an image forming apparatus comprising a transfer unit that transfers onto a transfer material,
An image forming apparatus using the developing device of claim 1, 2, 3, 4 or 5 as the developing means.

Images