JP4277670B2 - Developing device and image forming apparatus using the same - Google Patents

Description

  The present invention relates to a developing device used in an image forming apparatus such as a copying machine or a printer, and in particular, uses a two-component developer including a toner and a magnetic carrier to develop an electrostatic latent image on an image carrier with toner. The present invention relates to a developing device configured as described above and an improvement of an image forming apparatus using the developing device.

2. Description of the Related Art Conventionally, as a developing device used in an image forming apparatus such as a copying machine or a printer, a device adopting a so-called hybrid developing method is known.
This includes a donor roll that faces an image carrier such as a photoconductor and carries toner, and a toner transport roll that carries a two-component developer that contains the toner and a magnetic carrier and that faces this donor roll. A large amount of developer is supplied from a toner conveying roll by a magnetic brush to form a toner layer on a donor roll (see, for example, Patent Document 1).
In this hybrid development system, since the toner is normally charged by stirring the two-component developer, it is easy to ensure a sufficient charge amount, and the toner is supplied from the toner transport roll to the donor roll by electrostatic force. Therefore, the toner charged with the reverse polarity is not supplied to the donor roll. Therefore, there is no adhesion of toner to the non-image area of the image carrier and the occurrence of fog is prevented. Further, since only the toner is supplied to the donor roll, there is an advantage that adhesion of the magnetic carrier to the image carrier is prevented.

Japanese Patent Laid-Open No. 9-21970 (column of embodiment of the invention, FIG. 1) JP-A-9-251237 (column of embodiment of the invention, FIG. 1) JP-A-10-319708 (column of embodiment of the invention, FIG. 1) Japanese Patent Laid-Open No. 10-340003 (column of embodiment of the invention, FIG. 1)

  However, in this type of hybrid development method, a method of replenishing toner in the toner supply area with respect to a portion where the toner is consumed on the donor roll is adopted. However, not only the portion where the toner is consumed but also the toner The toner is also supplied to the non-consumed portion where the toner remains, and therefore, there is a problem of development history that the previous toner consumption pattern appears on the developed image.

  In addition, when toner supply and scraping are repeated on the donor roll, the difference in physical adhesion between the large particle size toner and the small particle size toner (the large particle size toner is physically attached to the donor roll). Because the adhesion force is small, it can be easily scraped against the scraping force received in the nip area, but the toner with a small particle size is difficult to be scraped.) It will turn. This change in particle diameter on the donor roll brings about a change in development characteristics and transfer characteristics. The toner remains on the donor roll without being developed, and a new toner is supplied to the area. There is a toner density difference between the supplied area and this may cause an image defect (development history).

Therefore, a method is known in which all the toner is once removed from the donor roll that has passed through the development area, and then the toner is again carried on the donor roll at a portion (toner supply area) between the donor roll and the toner supply roll. . For example, there is a system that uses a scraper as the toner removing means, but in this case, there is a problem that the toner is fused to each other at the contact portion between the scraper and the donor roll.
Therefore, a method of adding a new toner collecting roll separately from the toner supplying roll and scraping off the toner on the donor roll with the toner collecting roll is also disclosed (for example, see Patent Document 2).

However, in this new method of adding a toner collection roll, if the amount of developer supplied to the toner supply roll and the toner collection roll is unstable, the amount of toner on the donor roll becomes unstable. , Uneven density occurs in the image.
In particular, it becomes more prominent when the developer is easily stressed between the toner supply roll and the toner collection roll, and the fluidity of the developer decreases.

For this reason, there has been proposed a method of stabilizing the developer transport amount by rotating the toner supply roll and the toner collection roll in the same direction and further arranging them in close proximity to each other (see, for example, Patent Documents 3 and 4). .
However, in this case, the problem of bias leakage between the two rolls is likely to occur, and is particularly noticeable when the toner concentration is lowered and the operating environment is in a high humidity state. Furthermore, there is a problem that the developer entering between the two rolls is stressed, the developer is likely to be deteriorated, image fogging occurs, and stable development characteristics cannot be obtained over a long period of time. .
The present invention has been made in order to solve the above technical problem, and is a development in which the supply of a developer is stable, density unevenness can be suppressed over a long period of time, and development characteristics are stable over a long period of time. An apparatus and an image forming apparatus using the same are provided.

  That is, as shown in FIG. 1A, the basic configuration of the present invention includes a toner carrier 2 that faces an image carrier 1 carrying an electrostatic latent image and carries toner on its surface, and this toner carrier. A developer carrying body 3 for supplying and supplying a toner to the toner carrying body 2 and carrying a two-component developer (developer) G including toner and a magnetic carrier disposed at a position opposite to the toner 2; A developer carrier 4 for collection that carries the developer G and collects the toner from the toner carrier 2 disposed at a position facing the carrier 2, and two developers that have magnetic field generating means inside. A conveying member 5 is provided opposite to the carrier 3 and 4 and the toner carrier 2 and delivers the developer G between the two developer carriers 3 and 4.

  In particular, according to the present invention, as shown in FIGS. 1A and 1B, the developer G is rotated so as to be stirred and conveyed along the axial direction of the toner carrier 2, and the two developer carriers 3, 4 are rotated. A stirring and conveying member 6 (specifically, 6a and 6b) for supplying the developer G recovered from one developer carrying member to the other developer carrying member while being frictionally charged is provided, and at least one stirring and conveying member is provided. 6 is characterized in that the developer G is stirred and conveyed in a state where the developer G is biased to the side away from the conveying member 5.

In such technical means, the developing device according to the present application is of a type using the developer G, and therefore, toner having various color components can be used, and a single-color developing device is provided. Of course, the present invention can be applied to an image forming apparatus, for example, a full-color image forming apparatus having a plurality of developing devices.
The toner carrier 2 is preferably an elastic member at least on the surface, but may be a metal. In the case of an elastic member, the toner carrier 2 may be in contact with the image carrier 1.
The two developer carriers 3 and 4 may be appropriately selected as long as the developer carriers 3 and 4 are provided with a magnetic field generating means and carry and transport the developer G. For example, a rotatable nonmagnetic sleeve, There is an aspect including a magnet member fixedly disposed in the non-magnetic sleeve and provided with a magnetic field generating means.
Further, the magnetic field generating means may be any means having a plurality of magnetic poles. For example, as a configuration example of the magnetic poles, a development magnetic pole for contributing to development and a function of capturing the developer G are provided. Examples include a pickup magnetic pole, a conveyance magnetic pole for conveying the developer G, and the like, but are not limited thereto, and may be appropriately selected.
Furthermore, from the viewpoint of effectively transferring the toner between the two developer carriers 3 and 4 and the toner carrier 2, and between the developer carrier 3 for supply and the toner carrier 2 and the recovery. It is preferable that a predetermined electric field for supplying or collecting the toner to the toner carrier 2 is formed between the developer carrier 4 and the toner carrier 2, and at this time, the developer carrier The bias applied to 3 and 4 may be a DC voltage or an AC superimposed DC voltage.

On the other hand, like the two developer carriers 3 and 4, the conveying member 5 includes a magnetic field generating means inside, and the positions of the conveying member 5 are the supply developer carrier 3 and the recovery developer carrier. Any mode in which the toner carrier 2 is in contact with the toner carrier 2 is possible as long as the mode is separated from the toner 4 by a predetermined interval.
Here, “delivering the two-component developer G between the two developer carriers 3 and 4” means that the developer G is transferred between the two developer carriers 3 and 4 on the upstream side. This is not a mode in which the developer is conveyed directly from the body to the downstream developer carrier, but a mode in which the material is delivered through the conveying member 5.
The conveying member 5 is preferably rotated in the same direction at a portion facing the two developer carriers 3 and 4, whereby the conveying member 5 and the two developer carriers 3 and 4 are rotated. The stress of the developer G is reduced at the facing portion. Even if the transport member 5 and the developer carriers 3 and 4 are rotated in different directions, any mode that does not give stress to the flow of the developer G may be used.
The toner used in the present invention may be magnetic or nonmagnetic as long as it adheres to the magnetic carrier.

Furthermore, the agitating and conveying member 6 in the present invention may be any member that charges the internal developer G and enables the developer to be supplied to the developer carrying member. A typical embodiment is an auger. .
Moreover, the quantity of the stirring conveyance member 6 may be one, and may be provided with two or more. However, from the viewpoints of downsizing of the apparatus and supply capability of the developer G, an embodiment having two is preferable.
In the aspect including the plurality of agitation transport members 6 in the present invention, the developer G is caused to flow from the recovery developer support 4 to the supply developer support 3 via the transport member 5 (With). In the case of the system), the agitating / conveying member 6 may be in the vicinity of the collecting developer carrier 4 for supplying the developer G and in a position for receiving the developer G returned from the supplying developer carrier 3. Arranged horizontally. On the other hand, in a mode (Against method) in which the developer G flows from the supply developer carrier 3 to the recovery developer carrier 4 side via the conveyance member 5, the agitation conveyance member 6 supplies the developer G. It suffices if it is in the vicinity of the supply developer carrier 3 and a position for receiving the developer G returned from the recovery developer carrier 4 and is usually arranged in the vertical direction.
Further, in order to supply the developer G from the stirring / conveying member 6 side to the developer carrying member side, for example, a conveyance assisting member such as an auxiliary paddle can be used, and the stirring / conveying member from the developer carrying member side can be used. In order to facilitate transport of the developer G to the 6 side, a transport assisting member or the like may be used.

  In such an embodiment, the present inventors determine the developer G to be supplied to the developer carrier depending on the layout of the agitating and conveying member 6 and the conveying member 5, the developer G conveying method in the agitating and conveying member 6, and the like. The present inventors have found a technical problem that there is a concern that a supply failure and a non-uniform toner concentration in the developer G may be caused, and that the phenomenon may be further caused when the toner concentration of the developer G is lowered. In order to solve this technical problem, attention was paid to the conveyance surface trajectory of the developer G by the agitation conveyance member 6.

The developer G that is agitated and conveyed in the agitating and conveying member 6 has its conveyance surface locus normally biased depending on the rotation direction. Therefore, when the distance between the agitating / conveying member 6 and the conveying member 5 becomes short, the developer G having a deviated conveying locus surface depending on the rotation direction of the agitating / conveying member 6 may be affected by the magnetic force of the conveying member 5.
In that case, there is a concern that the original flow of the developer G in the agitating / conveying member 6 may be impaired, causing a supply failure of the developer G supplied to the developer carrying member and a non-uniform toner concentration in the developer G. .
In addition, the above problem is more likely to occur particularly when the toner concentration of the developer G is lowered. This is because the carrier concentration is relatively increased due to the decrease in the toner concentration, so that the adhesion between the carriers is increased and the carrier member 5 is more easily affected by the magnetic force.
Therefore, as a countermeasure against this problem, for example, in order to reduce the influence of the magnetic force, the agitating and conveying member 6 may be disposed with a distance to a position where the influence of the magnetic force of the conveying member 5 is not provided. Although it may be possible to increase the thickness of the guide member or the like between the conveying member 6, the problem arises that the developing device becomes larger or the cost increases.

Therefore, by controlling the rotation direction of the agitating and conveying member 6, the conveyance path surface of the developer G can be configured to be biased in a direction far away from the conveying member 5, and in the axial direction within the agitating and conveying member 6. Thus, the developer G can be moved smoothly, the stirring performance is not deteriorated, and the developer G can be uniformly supplied to the developer carrier side with a predetermined developer amount and toner concentration.
In the present invention, it is preferable to rotate all the agitating and conveying members 6 in a direction in which the influence of the magnetic force of the conveying member 5 is reduced. However, some of the agitating and conveying members 6 are less affected by the magnetic force of the conveying member 5. Further, for example, even if the stirring and conveying member 6 that is closest to the conveying member 5 is rotated as described above, the viewpoint of reducing the influence of the magnetic force of the conveying member 5 is also possible. Can be used. Furthermore, for example, even if the stirring and conveying member 6 that is closest to the magnetic field generating means of the conveying member 5 is rotated as described above, there is no problem from the viewpoint of reducing the influence of the magnetic force of the conveying member 5.
Furthermore, the present invention is also directed to an image forming apparatus using the above-described developing device.

According to the present invention, a toner carrier and two developer carriers for supplying and recovering toner to the toner carrier are provided, and further, between the two developer carriers at positions opposed to these. Since the conveying member for delivering the developer is provided, the flow of the developer becomes smooth and the stress received by the developer is reduced, so that a developing device free from development history, density unevenness and fogging can be provided.
In particular, since the developer flow on the agitating and conveying member is performed in a direction in which the influence of the magnetic force of the conveying member is reduced, the amount of developer supplied to the developer carrying member and the toner concentration are stabilized. Thus, an image free from uneven density and ghosting is possible.
Further, by using this developing device, it is possible to provide a small-sized image forming apparatus with stable development characteristics over a long period of time.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
Embodiment 1
FIG. 2 shows Embodiment 1 of an image forming apparatus to which the present invention is applied.
In the figure, reference numeral 21 denotes a photoconductor that carries an electrostatic latent image made of an organic photoconductor that rotates in the direction of an arrow. The photoconductor 21 is charged by a charging device 22 such as a scorotron, and a laser writing device or LED. An electrostatic latent image is written by the exposure device 23 having an array.
The electrostatic latent image is formed as a potential image based on contrast with a high potential portion not exposed to light because the surface potential of the photoreceptor 21 in the portion exposed to light is lowered.

Further, the developing device 30 contains a two-component developer composed of toner and a magnetic carrier in a developing housing 31, a donor roll 32 that carries the toner, a toner supply roll 33 for supplying toner, and a toner for collecting toner. A collection roll 34 and a transport roll 35 for transporting the developer are provided.
In the present embodiment, the toner image on the photoreceptor 21 is visualized by the developing device 30 and then transferred onto the recording material 28 by the transfer roll 26, and the transferred recording material 28 is fixed. The toner image on the recording material 28 is fixed by the fixing device 50. The fixing device 50 has, for example, a heat roll method, and includes a heating roll 51 and a pressure roll 52. By passing the recording material 28 between the heating roll 51 and the pressure roll 52, a toner image is obtained. Is fixed to the recording material 28.
The toner remaining on the photoreceptor 21 is removed by, for example, a doctor blade type cleaning device 29.

Here, the developing device 30 which is a feature of the present invention will be described in detail with reference to FIG. In this embodiment, the two-component developer (developer) G is configured to flow from the toner recovery roll 34 to the toner supply roll 33 via the transport roll 35 (With method).
In FIG. 2, the developing device 30 has a developing housing 31 (see FIG. 2) that opens toward the photosensitive member 21, and faces the opening of the developing housing 31 and faces the photosensitive member 21. The donor roll 32 is rotatably accommodated. A bias power source 37 is connected to the donor roll 32 so that a predetermined developing bias VB is applied.
In the present embodiment, the outer peripheral portion of the donor roll 32 is configured to be covered with an elastic member. However, for example, a metal roll made of aluminum or stainless steel may be used. Further, the donor roll 32 and the photoconductor 21 are in contact with each other, but they may be non-contact.

A toner supply roll 33 and a toner recovery roll 34 are disposed behind the donor roll 32 (on the side opposite to the photoconductor 21) with a predetermined gap from the donor roll 32.
The toner supply roll 33 and the toner collection roll 34 are connected to bias power supplies 38 and 39, respectively, and supply bias VS for supplying toner from the toner supply roll 33 to the donor roll 32. A collection bias VR for collecting the toner is applied to the collection roll 34.
Further, at the rear of the toner supply roll 33 and the toner collection roll 34, a conveyance roll 35 for carrying and conveying the developer G so as to deliver the developer G on the outer periphery of the toner supply roll 33 to the toner collection roll 34 is arranged. It is installed.

In the present embodiment, the magnet body 33b of the toner supply roll 33 has magnetic poles (N2, S1, N1, S2, S3) on the outer periphery thereof, and the magnetic pole S1 is provided at a position facing the donor roll 32. It arrange | positions so that the conveyance roll 35 may be opposed in the vicinity of the magnetic pole N2.
Further, the magnet body 34b of the toner recovery roll 34 includes a plurality of magnetic poles (S5, N3, S4, N4) on the outer peripheral portion thereof, and the magnetic pole S4 is provided at a position facing the donor roll 32. It is arranged so that the middle of N5 is positioned to face the transport roll 35.
Further, the magnet body 35 b of the transport roll 35 is disposed so that the magnetic pole S 7 is positioned opposite the toner recovery roll 34 among the plurality of magnetic poles (S 7, N 6, S 6).

  Further, a first guide piece 43 that guides the developer conveyance is provided at the rear part of the conveyance roll 35 in a semicircular shape that is substantially concentric with the conveyance roll 35, and the developer G is disposed on the outer periphery of the conveyance roll 35. It is designed to be transported efficiently. A second guide piece 44 for suppressing the flow of the developer G is provided at a position facing the toner supply roll 33, and at a position facing the toner recovery roll 34 with a predetermined interval, A trimmer 42 for regulating the layer thickness of the developer G on the toner collecting roll 34 is provided.

Furthermore, a stirring unit 41 is disposed below the first guide piece 43 via a partition plate 45, and two stirring members 41a and 41b are accommodated in the cases 411a and 411b. Yes. These agitating members 41a and 41b are composed of, for example, a spiral auger, and are configured to supply the developer G to the toner collecting roll 34 after the developer G is agitated and charged. In addition, in this Embodiment, although it is set as the aspect provided with two stirring members 41a and 41b, this number is not specifically limited, One may be sufficient and it may be three or more. Reference numeral 412 denotes a part of each of the cases 411a and 411b of the stirring members 41a and 41b. In the present embodiment, the partitioning walls of the two stirring members 41a and 41b are configured.
In particular, in the present embodiment, the two agitating members 41a and 41b rotate in the directions of the arrows in the figure (the agitating member 41a is clockwise in the figure and the agitating member 41b is counterclockwise in the figure). The developer G is biased to the left side of the drawing in the stirring member 41a and to the right side of the drawing in the stirring member 41b.

FIG. 4 shows the stirring unit 41, and is a perspective view of the stirring unit 41 in FIG. In the figure, the stirring member 41a is provided with spiral blades 414a around the rotation shaft 413a, and the developer G flows in the direction of arrow E. On the other hand, the stirring member 41b is provided with spiral blades 414b around the rotation shaft 413b, and the developer G flows in the direction of arrow F.
Reference numeral 414 is a trickle for discharging excess developer, reference numeral 415 is a supply unit for supplying a new developer, and reference numeral 416 is for easily supplying the developer G from the stirring member 41a to the toner collecting roll 34. An auxiliary paddle (not shown).

Here, in order to determine the configuration of the stirring members 41a and 41b, the following sequence is performed.
First, the conveyance direction of the developer G by the stirring members 41a and 41b is determined. For example, as in the present embodiment, the stirring member 41a is determined in the direction of arrow E, and the stirring member 41b is determined in the direction of arrow F.
Next, in order to bias the developer G in a direction far from the transport roll 35, the rotation directions of the stirring members 41a and 41b are determined. For example, in the present embodiment, the stirring member 41a is clockwise and the stirring member 41b is counterclockwise. At this time, the developer G in the stirring members 41a and 41b is uniquely determined by the rotation direction of the rotation shafts 413a and 413b.
Next, the direction of the spiral blades 414a and 414b (how to wind the right screw or the left screw) is determined so that the developer G inside is conveyed when rotated in this rotation direction.
In this manner, by configuring the agitating members 41a and 41b, desired conveyance characteristics of the developer G can be obtained.

Next, the operation of the developing device according to the present embodiment will be described.
In FIG. 3, the developer G is agitated by the agitating members 41a and 41b, and after the toner is negatively charged and the magnetic carrier is positively charged, the developer G is upstream of the magnetic pole S5 in the magnet body 34b of the toner recovery roll 34. In the developer supply area on the side, the toner is supplied from the stirring member 41 a to the toner collecting roll 34. When the developer G reaches the vicinity of the trimmer 42, it forms a spike by the magnetic pole N3. Further, the rising of the developer G is controlled by the trimmer 42, so that it is held on the outer periphery of the toner collecting roll 34 as a developer layer and conveyed along with the rotation of the rotating sleeve 34a. At this time, the developer G constitutes a magnetic brush along the lines of magnetic force formed by the magnet body 34b.

  Next, when the developer G enters the toner recovery area where the toner recovery roll 34 and the donor roll 32 face each other, a magnetic brush is formed by the magnetic attractive force of the magnetic pole S4, and the toner on the donor roll 32 is scraped off. take. At this time, an electrostatic force that attracts toner from the donor roll 32 to the toner collection roll 34 side is acted on by the electric field between the donor roll 32 and the toner collection roll 34, and toner collection from the donor roll 32 to the toner collection roll 34 side is ensured. I have to.

The developer G that has finished collecting the toner in the toner collecting area is in the vicinity of the area where the toner collecting roll 34 and the conveying roll 35 face each other due to the attractive magnetic field of the magnet body 34b of the toner collecting roll 34 and the magnet body 35b of the conveying roll 35. Then, it is delivered to the transport roll 35 side.
The developer G transferred to the transport roll 35 is held by the transport roll 35 by the magnetic field attracted by the magnet body 35b, and is transported on the outer periphery of the transport roll 35 along with the rotation of the rotating sleeve 35a. In a region facing the roll 33, the magnetic field is transferred from the transport roll 35 to the toner supply roll 33 side by an attractive magnetic field between the magnet body 35 b of the transport roll 35 and the magnet body 33 b of the toner supply roll 33.
The developer G transported on the outer periphery of the toner supply roll 33 forms a magnetic brush by the magnetic attractive force of the magnetic pole S1 in the toner supply region near the magnetic pole S1, and the toner in the developer G that has formed this magnetic brush. Only the toner is electrostatically attracted from the toner supply roll 33 to the donor roll 32 side by the influence of the electric field formed between the toner supply roll 33 and the donor roll 32, and adheres on the donor roll 32.

  Thereafter, the developer G that has finished supplying the toner is separated from the toner supply roll 33 by the repulsive magnetic field between the magnetic pole S2 and the magnetic pole S3, and is returned to the stirring member 41b side along the second guide piece 44. The developer G returned to the stirring member 41b is supplied again to the toner collection roll 34 side through the stirring member 41a while charging with stirring.

Therefore, the toner recovery performance and the developer supply amount in the toner recovery area are stabilized, and further, there is no stress of the developer G, and a developing device without bias leak is possible, and there is no development history, density unevenness and fogging. A developing device is possible.
In particular, in the present embodiment, the developer G inside thereof is transported in a direction far from the transport roll 35 due to the rotation direction of the respective stirring members 41a and 41b. The effect of magnetic force is reduced. Therefore, the flow of the developer G in the stirring members 41a and 41b can maintain a good flow even when the toner concentration is lowered, and can suppress the occurrence of image defects such as uneven density and ghost.

If the rotation direction of the agitating members 41a and 41b is different from the present embodiment, the developer G in the agitating members 41a and 41b is biased in a direction different from that in FIG. 3, as shown in FIG. . Therefore, the developer G in the stirring members 41a and 41b is closer to the transport roll 35, and is both attracted by the magnetic force of the transport roll 35 in the direction of the broken arrow H.
As described above, when the developer G is sucked toward the transport roll 35, the flow of the developer G inside the stirring members 41a and 41b is impaired, and the developer transportability and toner recovery inside the stirring members 41a and 41b are impaired. This affects the developer supply performance to the roll 34 side, and increases the possibility of image defects such as uneven density and ghost in the output image.

Embodiment 2
FIG. 6 shows a second embodiment of a developing device used in an image forming apparatus to which the present invention is applied.
In the figure, the present embodiment is configured in substantially the same manner as the developing device in the first embodiment, but the flow of the developer G is different from that in the first embodiment, and the toner supply roll 33 to the transport roll 35 and the toner collection roll 34 (Against method).
In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and the detailed description is abbreviate | omitted.

In the present embodiment, the magnet body 33b of the toner supply roll 33 includes magnetic poles (N3, S2, N1, S1, N2) on the outer peripheral portion thereof, and the magnetic pole S1 is provided at a position facing the donor roll 32. It arrange | positions so that the conveyance roll 35 may be opposed in the vicinity of the magnetic pole N2.
Further, the magnet body 34b of the toner recovery roll 34 has a plurality of magnetic poles (S4, N4, S3, N5, N6) on the outer periphery thereof, and a magnetic pole S3 is provided at a position facing the donor roll 32, and the magnetic pole S4. And the magnetic pole N <b> 4 are arranged so as to be in a position facing the transport roll 35. Further, the magnet body 35 b of the transport roll 35 is arranged so that the vicinity of the magnetic pole S 6 among the plurality of magnetic poles (S 5, N 7, S 6) faces the toner collection roll 34.

  Further, a first guide piece 43 that guides the developer conveyance is provided at the rear part of the conveyance roll 35 in a semicircular shape that is substantially concentric with the conveyance roll 35, and the developer G is disposed on the outer periphery of the conveyance roll 35. It is designed to be transported efficiently. A second guide piece 44 for suppressing the flow of the developer G is provided at a position facing the toner recovery roll 34, and at a position facing the toner supply roll 33 with a predetermined interval, A trimmer 42 for regulating the layer thickness of the developer G on the toner supply roll 33 is provided.

Further, a stirring unit 41 is disposed behind the first guide piece 43 via a partition plate 45 for preventing the developer G from entering the transport roll 35 side. In the stirring unit 41, two stirring members 41a and 41b are accommodated in the cases 411a and 411b.
The agitating members 41 a and 41 b are constituted by, for example, a spiral auger, and are configured to supply the developer G to the toner supply roll 33 after the developer G is agitated and charged. In the present embodiment, two stirring members 41 are provided. However, this number is not particularly limited, and may be one or three or more.
In particular, in the present embodiment, the two agitating members 41a and 41b rotate in the direction of the arrows in the figure (both counterclockwise), and therefore the developer G is on one side of the agitating members 41a and 41b (specifically In particular, it is biased to the right side of the figure. The spiral blades 414a and 414b (see FIG. 4) are determined depending on the transport direction of the developer G in the stirring members 41a and 41b.
An auxiliary paddle (not shown) is provided between the stirring member 41 a and the toner supply roll 33, so that the developer G is smoothly supplied to the toner supply roll 33.

Next, the operation of the developing device according to the present embodiment will be described.
In FIG. 6, the developer G is agitated by the agitating members 41 a and 41 b, and after the toner is negatively charged and the carrier is positively charged, the developer G is upstream of the magnetic pole S <b> 2 on the magnet body 33 b of the toner supply roll 33. In the developer supply area, the toner is supplied to the toner supply roll 33.
When the developer G reaches the vicinity of the trimmer 42, it forms a spike by the magnetic pole S2.
Further, the rising of the developer G is controlled by the trimmer 42 so that the developer layer is held on the outer periphery of the toner supply roll 33 and is conveyed along with the rotation of the rotating sleeve 33a.
At this time, the developer G constitutes a magnetic brush along the lines of magnetic force formed by the magnet body 33b.

  Next, when the developer G enters the toner recovery area where the toner supply roll 33 and the donor roll 32 face each other, a magnetic brush is formed by the magnetic attractive force of the magnetic pole S1 and the toner is supplied to the donor roll 32. . At this time, an electrostatic force that attracts toner from the toner supply roll 33 to the donor roll 32 is activated by the electric field between the donor roll 32 and the toner supply roll 33, and toner supply from the toner supply roll 33 to the donor roll 32 is ensured. .

The developer G to which the toner has been supplied reaches the conveyance roll 35 in the vicinity of the region where the toner supply roll 33 and the conveyance roll 35 face each other due to the attractive magnetic field of the magnet body 33 b of the toner supply roll 33 and the magnet body 35 b of the conveyance roll 35. Delivered.
The developer G transferred to the transport roll 35 is held on the transport roll 35 by the magnetic field attracted by the magnet body 35b and transported on the outer periphery thereof. The magnet body 35b of the transport roll 35 and the magnet body 34b of the toner recovery roll 34 are conveyed. Is transferred to the toner collection roll 34 in a region where the conveyance roll 35 and the toner collection roll 34 face each other.

The developer G conveyed on the outer periphery of the toner recovery roll 34 forms a magnetic brush by the magnetic attractive force of the magnetic pole S3 in the toner recovery area near the magnetic pole S3, and is formed between the toner recovery roll 34 and the donor roll 32. Under the influence of the applied electric field, the toner on the donor roll 32 is recovered from the donor roll 32 to the developer G on the toner recovery roll 34.
After that, the developer G conveyed on the outer periphery of the toner collection roll 34 is separated from the toner collection roll 34 by the repulsive magnetic field between the magnetic pole N5 and the magnetic pole N6, and then along the second guide piece 44 to the stirring member 41b. Returned.

In this embodiment as well, the toner collection performance and developer supply amount in the toner collection region are stable, and further, a developing device free from the stress of the developer G and free from bias leakage becomes possible. Therefore, also in the present embodiment, a developing device without development history, density unevenness and fog is possible.
In particular, also in the present embodiment, because the developer G inside thereof is transported in a direction far from the transport roll 35 depending on the rotation direction of the respective stirring members 41 a and 41 b, the magnet body 35 b of the transport roll 35. The effect of magnetic force is reduced. Therefore, the flow of the developer G in the stirring members 41a and 41b becomes smooth, and it is possible to suppress the occurrence of image defects such as density unevenness and ghost.

If the rotation direction of the agitating members 41a and 41b is different from the present embodiment, as shown in FIG. 7, the developer G in the agitating members 41a and 41b is biased in a direction different from that in FIG. .
Therefore, the developer G in the stirring member 41 becomes closer to the transport roll 35 and is attracted by the magnetic force of the transport roll 35 in the direction of the broken arrow J.
As described above, when the developer G is sucked toward the transport roll 35, the flow of the developer G inside the stirring members 41a and 41b is impaired, and the developer transportability and toner supply inside the stirring members 41a and 41b are impaired. This affects the developer supply performance to the roll 33 side, and increases the possibility of image defects such as density unevenness and ghost in the output image.

In this example, an experiment with the same configuration as that of the first embodiment was performed, and the uniformity of the developer amount on the toner recovery roll was confirmed.
The experimental conditions in this example were as follows.
Developer toner concentration: 5%, 8% (equivalent to normal toner concentration)
Photoconductor peripheral speed: 220 mm / s
Donor roll peripheral speed: 280 mm / s
Toner supply roll, transport roll, toner collection roll peripheral speed: 450 mm / s
Gap between toner supply roll and trimmer: 0.7 mm
Gap between donor roll and toner recovery roll: 0.5 mm
Gap between donor roll and toner supply roll: 0.5 mm
Photoconductor surface potential: -650V
Development bias (VB): -450V
Supply bias (VS): -575V
Recovery bias (VR): -250V

The evaluation was carried out by visually evaluating the uniformity of the developer amount in the axial direction of the toner recovery roll after operating for 1 minute under the above conditions. As a comparative example, the same evaluation was performed in a direction (specifically, refer to FIG. 5) in which the rotation direction of the stirring member is different from that of the present example.
As a result, as shown in FIG. 8, in this example, even when the toner concentration of the developer was lowered, the amount of developer on the toner collecting roll was uniform. Therefore, it was confirmed that the developer supply performance from the stirring member was good, and the developer flow in the developing device was smoothly performed.
On the other hand, when the rotation direction of the stirring member is different from that of the present embodiment, it was confirmed that the amount of developer on the toner recovery roll becomes non-uniform.

(A) (b) is explanatory drawing which shows the outline | summary of the image development apparatus concerning this invention. 1 is an explanatory diagram showing Embodiment 1 of an image forming apparatus to which the present invention is applied. FIG. 2 is an explanatory diagram illustrating a developing device according to the first embodiment. It is a perspective view which shows the stirring unit seen from the arrow D direction in FIG. FIG. 3 is an explanatory view showing a developing device provided with a stirring member in a rotational direction different from that of the first embodiment. FIG. 10 is an explanatory diagram illustrating a developing device according to a second embodiment. FIG. 10 is an explanatory view showing a developing device provided with a stirring member in a rotational direction different from that of Embodiment 2. It is explanatory drawing which shows the evaluation result of an Example.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image carrier, 2 ... Toner carrier, 3 ... Supply developer carrier, 4 ... Collecting developer carrier, 5 ... Conveyance member, 6 (6a, 6b) ... Stir conveyance member, G ... Two component Developer

Claims (5)

A toner carrying member facing the image carrying member carrying the electrostatic latent image and carrying toner on the surface;
A developer carrying body for supply, which is disposed at a position facing the toner carrying body, carries and conveys a two-component developer containing toner and a magnetic carrier, and supplies the toner to the toner carrying body;
A collecting developer carrier that is disposed at a position facing the toner carrier, carries and conveys the two-component developer, and collects toner from the toner carrier;
A conveying member having a magnetic field generating means therein and disposed opposite to the two developer carriers and the toner carrier, and delivering a two-component developer between the two developer carriers;
One or a plurality of the developer carrying member that rotates so that the developer can be agitated and conveyed along the axial direction of the toner carrying member, and is supplied to the other developer carrying member while frictionally charging the developer collected from one developer carrying member. A stirring and conveying member,
At least one agitating and conveying member is a developing device characterized in that it agitates and conveys the developer in a state where the developer is biased to the side away from the conveying member. In the aspect which has a some stirring conveyance member among the developing devices of Claim 1,
The developing device, wherein at least the agitating and conveying member closest to the conveying member agitates and conveys the developer in a state where the developer is biased to the side away from the conveying member. In the aspect which has a some stirring conveyance member among the developing devices of Claim 1,
2. A developing device according to claim 1, wherein at least the agitating / conveying member closest to the magnetic field generating means of the conveying member agitates and conveys the developer in a state where the developer is biased toward the side away from the conveying member. In the aspect which has a some stirring conveyance member among the developing devices of Claim 1,
A developing device, wherein the plurality of agitating and conveying members agitate and convey the developer in a state where the developer is biased toward the side away from the conveying member.   An image forming apparatus comprising the developing device according to claim 1.

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