JP4375051B2 - 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 However, there is a problem in the development history that toner is supplied to the remaining non-consumed portion, and 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 the particle size on the donor roll causes a change in development characteristics and transfer characteristics, and a region where new toner is supplied without developing and the toner remains on the donor roll, and the toner is developed and developed. There is a possibility that a toner density difference occurs between the area where new toner is supplied in a state where the toner is consumed, 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. Further, the developer entering between the two rolls is stressed, the developer is likely to be deteriorated, and there is a problem that fog occurs, and there is a problem that 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. The developer supply amount is stable, density unevenness can be suppressed over a long period of time, and development characteristics are stable over a long period of time. A developing device and an image forming apparatus using the same are provided.

  That is, as shown in FIG. 1, the basic configuration of the present invention is such that a toner carrier 2 carrying a toner on the surface thereof facing an image carrier 1 carrying an electrostatic latent image, and a toner carrier 2 facing this toner carrier 2. A supply developer carrier 3 that carries and conveys a two-component developer G including toner and a magnetic carrier and supplies toner to the toner carrier 2, and a position facing the toner carrier 2. A collecting developer carrier 4 that carries and conveys the two-component developer G and collects toner from the toner carrier 2, and the two developer carriers 3, 4 and the toner carrier 2. A conveying member 5 that is disposed to face and transfers the two-component developer G between the two developer carriers 3 and 4, and disposed below the conveying member 5, Rotating to enable the two-component developer G to be stirred and conveyed along the axial direction and Those having a stirring conveying member 6 for supplying the two-component developer G recovered from a paper developer supporting member 3 Friction charged while the recovered developer supporting member 4.

  In particular, the present invention applies a developing device in which a two-component developer (hereinafter referred to as a developer) G is allowed to flow from a collecting developer carrier 4 to a supply developer carrier 3 via a conveying member 5. A return path regulating member 7 for returning the developer G peeled from the supply developer carrier 3 to the stirring and conveying member 6 is provided, and the return path regulating member 7 is peeled from the supply developer carrier 3. The release guide member 8 that separates the developer G that has been released into a range that is not affected by the magnetic force of the supply developer carrier 3 and the conveyance member 5, and the developer G guided by the release guide member 8 is conveyed to the conveyance member 5. A conveyance guide member 9 for guiding downward within a range not affected by the magnetic force of the toner, and supplying the developer to the collecting developer carrier 4 with a lower end portion from the upper end portion of the conveyance guide member 9. Providing a guide surface that is biased near the site It has a feature point. In addition, the return path | route control member 7 may be comprised with one member, and may be comprised with several members.

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 and the conveying member 5 may be appropriately selected as long as they have a magnetic field generating means inside and carry and convey the developer G, and can be rotated, for example. There is a mode in which a non-magnetic sleeve and a magnet member fixedly disposed in the non-magnetic sleeve and provided with magnetic field generating means are provided.
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, two developers The bias applied to the carriers 3 and 4 may be a DC voltage or an AC superimposed DC voltage.

The conveying member 5 in the present invention “deliver the two-component developer G between the two developer carriers 3 and 4” means that the developer G is collected between the two developer carriers 3 and 4. This is a mode in which the developer is not transferred directly from the developer carrier 4 to the supply developer carrier 3 but is passed through the conveying member 5.
Further, the conveying member 5 is preferably rotated in the same direction at a portion facing the two developer carriers 3, 4, whereby the conveying member 5 and the two developer carriers 3, 4 are rotated. In the opposite part, the stress of the developer G conveyed is reduced. Even if the transport member 5 and the two developer carriers 3 and 4 are rotated in different directions at the opposing portions, any mode that does not give stress to the flow of the developer G may be used. Reference numeral 10 in the figure denotes a guide cover that regulates the separation of the developer G carried and conveyed on the conveying member 5 from the conveying member 5.
The toner used in the present invention may be magnetic or nonmagnetic as long as it adheres to a magnetic carrier (carrier).

  Further, the agitating and conveying member 6 in the present invention is arranged below the conveying member 5 so that the developer G recovered from the supply developer carrier 3 can be supplied to the recovery developer carrier 4. . In this embodiment, the quantity of the agitating and conveying member 6 is not particularly limited. However, from the viewpoint of securing a desired charge amount and conveying performance of the developer G, a pair of augers (a pair of an admix auger and a supply auger) is used. It is preferable to provide a configuration in which a supply auger is provided on the collecting developer carrier 4 side.

In particular, the return path regulating member 7 according to the present invention includes a release guide member 8 and a transport guide member 9, and guides the developer G peeled off from the supply developer carrier 3 to the stirring transport member 6 and returns it. Installed on the route. The return path regulating member 7 may be composed of a single member.
And the conveyance guide member 9 should just be the aspect provided with the guide surface 9a which guides the developer G from the release guide member 8 to the collection | recovery developer carrier 4 direction, The shape is not specifically limited. In addition, it is preferable that the upper end portion of the conveyance guide member 9 is positioned above the release guide member 8 so as to guide the developer G from the release guide member 8 to the conveyance guide member 9, but not limited thereto. Any configuration that can receive the developer G from the release guide member 8 at the upper end of the transport guide member 9 may be used. Note that the transport guide member 9 is preferably composed of a single member, but may be composed of a plurality of members, or may be composed of a part of a developing housing, for example.

Further, the guide surface 9a of the transport guide member 9 is preferably provided with a concave curved surface portion on the transport member 5 side in order to return the developer G to the developer supply site side of the collecting developer carrier 4. As a result, the conveyance guide member 9 can be disposed close to the conveyance member 5 as far as it is not affected by the magnetic force of the conveyance member 5 compared to the planar conveyance guide member 9, and a small-sized developing device is possible. become. In addition, the whole conveyance guide member 9 may be provided with the concave curved surface part at the conveyance member 5 side, and it does not interfere even if it is an aspect provided with a curved surface part in part.
Then, in the aspect using the paired auger as the stirring and conveying member 6, the lower end portion of the conveying guide member 9 can be disposed at the position of the supply auger close to the collecting developer carrier 4. Since the developer G that has finished supplying the developer to the two developer carriers 3 and 4 can be quickly returned to the supply auger, the circulation efficiency of the developer G can be increased.

Furthermore, in the present invention, from the viewpoint of arranging the position of the guide surface 9a of the conveyance guide member 9 in a range where the influence of the magnetic force of the conveyance member 5 does not reach, the influence of the magnetic force of the conveyance member 5 is quantified. A magnetic flux density index was set, and an attempt was made to arrange the transport guide member 9 using this magnetic flux density index.
Now, as shown in FIG. 2, the conveying member 5 is assumed to be a cylindrical body 11 having a plurality of magnetic poles (magnetic poles 1 to 3), and attention is paid to one of the magnetic poles (magnetic pole 2). It is assumed that the magnetic field lines on the surface of the surface of the cylindrical body 11 extend radially from the center of the cylindrical body 11 and there is no distortion.
Therefore, the magnetic flux density at the point P on the magnetic pole surface of the cylindrical body 11 is B ₀ (mT), the radius of the cylindrical body 11 is R (mm), and the point is extended in the radial direction from the center of the cylindrical body 11 through the point P. When the distance to Q is L (mm), the number of magnetic lines of force per unit length φ (Wb / m) passing through the range for the angle θ between the position of the radius R and the position of the distance L is constant. Therefore, the relational expression as shown in the expression (2) in FIG. 3 is established.
Thereby, the magnetic flux density index B at the point Q is expressed by the equation (1) in FIG. 3 using the magnetic flux density B ₀ on the outer peripheral surface of the cylindrical body 11.
The magnetic flux density index B is calculated on the assumption that the direction of the magnetic field lines is radial from the center of the cylindrical body 11, but strictly speaking, it is influenced by other magnetic poles of the cylindrical body 11, and the angle of the magnetic poles. The number of lines of magnetic force crossing the area occupied by θ decreases as the distance L from the center of the cylindrical body 11 increases. However, in the present invention, since it is assumed that the developer G is within the range where the magnetic poles are affected, it has been determined that the number of lines of magnetic force due to the distance L does not change.
Thus, if the point P is the magnetic pole position of the cylindrical body 11 and its vicinity position, the above assumption is established. Further, when the point P is at a position different from the magnetic pole position, the magnetic field lines do not become radial, but the number of magnetic field lines crossing the area occupied by the angle θ from the center of the cylindrical body 11 is such that the point P as described above It is considered that the relationship is the same as in the case of the position. Therefore, from the relationship of magnetic flux density between an arbitrary point P on the surface of the cylindrical body 11 and a point Q extending in the radial direction through this point P, the magnetic flux density index at the point Q is generally shown in FIG. It becomes possible to make it into a formula.

  Using the magnetic flux density index B, the conveyance guide member 9 is set so that the magnetic flux density index B from the conveyance member 5 on the guide surface 9a is 40 or less, so that the flow of the developer G is It is possible to dispose the developer G within the range where the magnetic force of the conveying member 5 does not reach, prevent the developer G from adhering to the back surface of the guide cover 10 of the conveying member 5, and ensure the flow of the developer G.

  In the above-described aspect, the developer G peeled off from the supply developer carrier 3 can be quickly returned to a position close to the developer supply site to the recovery developer carrier 4. It can be applied to the case of designing with the aim of improving the circulation efficiency of At this time, the separated developer G is once separated in a range where the magnetic force of the supply developer carrier 3 and the conveying member 5 is not affected, and then the range where the magnetic force of the conveying member 5 is not affected. By returning through the path, it is possible to prevent the developer from adhering to the back surface of the guide cover 10 disposed in the vicinity of the conveying member 5. If the path is affected by the magnetic force of the conveying member 5, the developer G adheres to the back side of the guide cover 10, and the flow of the developer G is obstructed. There are concerns that it will occur.

The present invention can also be applied to a developing device according to another aspect.
For example, as a developing device intended to increase the speed, a developing region is disposed at a position facing an image carrier that carries an electrostatic latent image, carries and conveys a two-component developer, and develops at a portion facing the image carrier. And a plurality of developer carriers disposed at intervals between the upstream side and the downstream side in the developer transport direction, and two developer carriers adjacent to each other among the plurality of developer carriers one by one disposed between the body, and the conveying member to pass a two-component developer between these two developer carrying member and opposed to the image bearing member and the two of the developer carrying member, said plurality of A developer carrying member disposed below the developer carrying member and the conveying member, rotates so that the two-component developer can be stirred and conveyed along the axial direction of the developer carrying member, and is located on the most downstream side in the developer carrying direction. while frictionally charging a two-component developer collected from the body developer conveying direction And a stirring and conveying member for supplying the developer carrying member positioned at the upstream side, in the opposing portion between the image bearing member and the developer carrying member, include those that ensure a plurality of developing sites. In the this embodiment, the two-component developer which is peeled from the developer carrying member is located in the developer conveying direction downstream, between the developer carrying member adjacent to the developer carrying member and a developer carrying member A release guide member that is separated to a range that is not affected by the magnetic force of the arranged conveyance member, and the two-component developer guided by the release guide member is directed downward within a range that is not affected by the magnetic force of the conveyance member. What is necessary is just to provide the return path | route control member comprised with the conveyance guide member to guide.

Furthermore, the present invention can also be applied to a developing device that reduces the influence of a magnetic force that changes the concept based on the idea of the present invention.
For example, a developing device that reduces the influence of the magnetic force from the conveying member includes a toner carrier that carries an electrostatic latent image on the surface thereof and a toner carrier that carries toner on the surface, and a position that faces the toner carrier. A supply developer carrier for carrying and transporting a two-component developer (developer) including toner and a magnetic carrier and supplying the toner to the toner carrier, and a position facing the toner carrier. A developer carrying body for collecting and carrying the developer and collecting the toner from the toner carrying body, and the two developer carrying bodies and the toner carrying body disposed opposite to each other and the two developer carrying bodies. A conveying member provided with a plurality of magnetic poles for delivering the developer to and from the body, and disposed below the conveying member so that the developer can be agitated and conveyed along the axial direction of the toner carrier. Rotating and supplying developer carrier A stirring and conveying member that supplies the collected developer to the collecting developer carrying member while being frictionally charged, and a return path regulating member that returns the developer peeled off from the supplying developer carrying member to the stirring member. The return path regulating member includes a release guide member that separates the developer peeled off from the supply developer carrying member into a range not affected by the magnetic force of the supply developer carrying member and the carrying member, and one of the carrying members. And a guide cover that forms a developer transport path around the transport member. The guide cover is provided with a magnetic shield effect on the back side so as not to be affected by the magnetic force of the transport member. You can do it.
In this case, it is possible to prevent the developer guided by the release guide member from adhering to the developer peeled off from the developer carrier for supply, and to adhere to the back surface of the guide cover of the transport member, and to use an embodiment without using the transport guide member. . In addition, this makes it possible to further reduce the size of the apparatus. Note that a conveyance guide member may be used as necessary.
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 or 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 is smooth, the stress received by the developer can be reduced, and a developing device free from development history, density unevenness and fogging can be provided. . Further, the two developer carriers can be spaced apart, and there is no problem of bias leakage or the like.
In particular, a release guide member that separates the two-component developer peeled from the supply developer carrying member into a range that is not affected by the magnetic force of the supply developer carrying member and the conveying member, and a guide by the release guide member. Among the members having a guide surface that dams the two-component developer and guides it within the range not affected by the magnetic force of the conveying member, the lower end portion is closer to the developer supply site from the upper end portion to the collecting developer carrier. Since the return path regulating member composed of the transport guide member biased to the surface is provided, the developer peeled off from the supply developer carrier does not stay and the developer circulation performance is improved. The occurrence of image defects such as ghost and uneven density can be suppressed.
Further, according to another aspect of the present invention, it is disposed at a position facing the image carrier that bears the electrostatic latent image, and is spaced from the upstream side to the downstream side in the developer transport direction. It is also possible to develop and develop the electrostatic latent image directly on the image carrier by carrying and transporting the two-component developer by the plurality of developer carriers thus formed, and forming a development region at the portion facing the image carrier. Thus, a developing device corresponding to high-speed development can be provided. Further, the two-component developer guided by the release guide member can be guided downward by the transport guide member within a range not affected by the magnetic force of the transport member. Further, the two-component developer recovered from the developer carrying member located on the most downstream side in the developer carrying direction is frictionally charged by the plurality of developer carrying members and the stirring and carrying member disposed below the carrying member. The developer can be supplied to the developer carrying member located on the most upstream side in the developer transport direction.
Further, by providing the guide cover with a magnetic shielding effect, it is possible to block the influence of the magnetic force from the conveying member, and return the developer peeled off from the supply developer carrying member through a path closer to the conveying member. And a smaller developing device is possible.
Furthermore, by using these developing devices, it is possible to provide an image forming apparatus having 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. 4 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 accommodates a two-component developer (developer) composed of toner and a magnetic carrier (carrier) in a developing housing 31, a donor roll 32 that carries the toner, and a toner supply roll 33 for supplying toner. A toner collecting roll 34 for collecting toner, and a conveying roll 35 for conveying the developer.
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 transferred to the fixing device 50. 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 the drawing, the developing device 30 has a developing housing 31 (see FIG. 4) 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 accommodated so as to be rotatable in the direction of the arrow. 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 covered with a polyurethane resin-based elastic member having a predetermined volume resistivity. For example, the donor roll 32 is a metal roll made of aluminum or stainless steel. There is no problem. 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 toner supply roll 33, the toner collection roll 34, and the transport roll 35 are fixedly disposed inside the rotatable sleeves 33 a to 35 a and the rotatable sleeves 33 a to 35 a, and have a plurality of magnetic poles. Magnet bodies 33b to 35b having
The magnet body 33b of the toner supply roll 33 is provided with a plurality of magnetic poles (N2, S1, N1, S2, S3) on the outer periphery thereof, the magnetic pole S1 is provided at a position facing the donor roll 32, and in the vicinity of the magnetic pole N2. Is arranged to face the transport roll 35. The magnetic pole S2 and the magnetic pole S3 constitute a repulsive magnetic pole, and the developer G on the toner supply roll 33 is separated from the toner supply roll 33 by the action of the repulsive magnetic pole.
Further, the magnet body 34b of the toner recovery roll 34 has a plurality of magnetic poles (S5, N3, S4, N4, N5) on the outer periphery thereof, and a magnetic pole S4 is provided at a position facing the donor roll 32, so that the magnetic pole N4 is provided. And in the vicinity of the middle of the magnetic pole N5 so as to face the transport roll 35.
Further, the magnet body 35b of the transport roll 35 includes a plurality of magnetic poles (S7, N6, S6) on the outer peripheral portion thereof.

In addition, a guide cover 43 that guides the developer conveyance is provided in the semicircular shape substantially concentric with the conveyance roll 35 at the rear of the conveyance roll 35, and the developer G efficiently conveys the outer periphery of the conveyance roll 35. To be. A trimmer 42 that regulates the layer thickness of the developer G is provided at a position facing the toner collection roll 34.
Further, below the conveying roll 35, a pair of augers 41 (specifically 41a and 41b) as stirring and conveying members for supplying the developer G collected from the toner supply roll 33 to the toner collecting roll 34 are provided. And a supply auger 41a that mainly supplies the developer G to the toner collecting roll 34 and an admix auger 41b that mainly mixes and stirs the developer G behind the auger 41a.

In particular, in the present embodiment, the developer G peeled off by the repulsive magnetic poles S2 and S3 of the toner supply roll 33 is obliquely downward from the toner supply roll 33 and the transport roll 35 side at a position facing the toner supply roll 33. A release guide 44 is provided. Further, below the release guide 44, a guide guide 45 for guiding the developer G guided by the release guide 44 to the supply auger 41a is provided.
The guide guide 45 in the present embodiment has a shape in which the lower end portion is biased closer to the transport roll 35 than the upper end portion, and has a curved surface shape in which the curvature is gradually increased toward the lower end direction. The lower end portion of the guide guide 45 reaches the supply auger 41a. The developer G from the release guide 44 is blocked by the upper end portion, the guide surface 45a is slid, and then returned to the supply auger 41a. . Further, the guide surface 45a is positioned such that the magnetic flux density index by the magnetic poles of the transport roll 35 is 40 or less. Therefore, the developer G dropped from the release guide 44 does not adhere to the guide cover 43 and smoothly slides down the guide surface 45a to reach the supply auger 41a.
As a specific method for measuring the magnetic flux density for determining the magnetic flux density index, a Gauss meter MODEL HGM-8300-5 manufactured by ADS Co., Ltd. was used, and the probe was used as the surface of the toner supply roll 33 and the transport roll 35. Measured in the state of being close to the vertical direction.

6 shows a cross-sectional view of the structure of the auger 41 in the present embodiment, and two augers 41 (specifically, a supply auger 41a and an admix auger 41b) are arranged in the auger case 46. Has been. Each auger 41 has a rotating shaft 51 (specifically 51a, 51b) with spiral blades 52 arranged in a predetermined direction. Depending on the direction of the blades 52 and the rotating direction of the rotating shaft 51, the developer is developed. A predetermined flow of G is ensured. In this example, the developer G in the auger 41 circulates in the auger 41 through a circulation path as shown by a two-dot chain line in FIG.
In general, in a method using a pair of augers 41 (specifically 41a and 41b), as in the present embodiment, the developer roll G is supplied from the supply auger 41a and the donor roll 32 is supplied. After the toner is transferred to the supply auger 41a, the developer G used between the development route and the auger 41 is returned to the supply auger 41a side again (returned to the broken line α area in the figure). There is little damage to the circulation.
On the other hand, a configuration is adopted in which the developer G supplied from the supply auger 41a and delivered to the donor roll 32 is returned to the admix auger 41b (returned to the broken line β region in the figure). Then, a large amount of developer G needs to pass through the conveyance path 53 between the augers from the admix auger 41b to the supply auger 41a, and there is a concern that stagnation may occur.
As shown in FIG. 5, in this embodiment, the developer G from the guide guide 45 is returned to the supply auger 41a, so that the developer G does not stay in the auger 41. ing. In the figure, reference numeral 47 denotes a partition wall between the augers 41.

Next, the operation of the developing device according to the present embodiment will be described.
In FIG. 5, the developer G is agitated by the auger 41, and after the toner is negatively charged and the carrier is positively charged, the developer supply region in the vicinity of the magnetic pole S <b> 5 on the magnet body 34 b of the toner recovery roll 34. Then, the toner is supplied 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 the developer layer is held on the outer periphery of the toner collecting roll 34, and in the direction of the portion facing the donor roll 32 as the rotating sleeve 34a rotates. Be transported. 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 consumed for development on the donor roll 32. Scrap off the toner that was not used. At this time, the toner collection from the donor roll 32 to the toner collection roll 34 is ensured by the electric field between the donor roll 32 and the toner collection roll 34.

The developer G from which the toner has been collected is transferred from the toner collection roll 34 to the conveyance roll 35 by an attractive magnetic field between the magnet body 34 b of the toner collection roll 34 and the magnet body 35 b of the conveyance roll 35.
The developer G delivered to the transport roll 35 is held by the transport roll 35 by the magnetic field attracted by the magnet body 35 b, transported on the outer periphery thereof, and then the magnet body 35 b of the transport roll 35 and the magnet of the toner supply roll 33. Due to the attraction magnetic field with the body 33b, the toner is transferred to the toner supply roll 33 in a region where the transport roll 35 and the toner supply roll 33 face each other.

When the developer G transferred to the toner supply roll 33 enters the toner supply 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 this magnetic Only the toner in the developer G that forms the brush is electrostatically attracted from the toner supply roll 33 to the donor roll 32 by the influence of the electric field formed between the toner supply roll 33 and the donor roll 32, and Adhere to.
Then, after supplying the toner, the developer G conveyed on the toner supply roll 33 is peeled off from the toner supply roll 33 by the magnetic field formed by the repulsive magnetic poles S2 and S3 of the magnet body 33b.

  The developer G peeled from the toner supply roll 33 flows along the release guide 44 and falls from the rear end thereof by the action of gravity. The dropped developer G is conveyed along the guide surface 45a of the guide guide 45 and returned to the supply auger 41a. At this time, due to the curved surface shape of the guide surface 45a of the guide guide 45, the developer G dropped from the release guide 44 flows through the guide surface 45a vigorously and reaches the supply auger 41a without staying. Further, since the guide surface 45a has a magnetic flux density index set to 40 or less by the magnetic poles of the transport roll 35, the developer G transported on the guide surface 45a is not attracted by the magnetic force of the transport roll 35. The guide cover 43 is prevented from adhering to the back surface. Therefore, the developer G flows smoothly on the guide surface 45a.

Further, even when the toner concentration (TC) of the developer G used is reduced or when the developer G using a small carrier diameter is used, the developer G is hardly sucked by the transport roll 35. In addition, an image having no image defects such as ghost and density unevenness can be obtained without causing the developer G to stay, and further, since the stress of the developer G is reduced, stable development characteristics can be obtained over a long period of time. It becomes possible.
Further, in the present embodiment, the developer G is transported closer to the toner collection roll 34 by the guide surface 45a of the guide guide 45, so that the auger 41 can be brought closer to the toner collection roll 34 side, and the small size can be achieved. A developing device becomes possible.
Furthermore, by using this developing device, an image forming apparatus capable of obtaining a stable image over a long period of time becomes possible. In the present embodiment, a configuration in which the curvature gradually changes as the guide guide 45 is shown, but the shape of the guide guide 45 is not particularly limited as long as it can guide and convey the developer G.

Embodiment 2
FIG. 7 shows a second embodiment of the developing device according to the present invention. Unlike the first embodiment, the present embodiment is a developing device adopting a so-called high-speed developing configuration in which an electrostatic latent image on a photoreceptor is directly developed with a two-component developer.
In the figure, the configuration is substantially the same as the developing device in the first embodiment, but the donor roll 32 in the first embodiment is removed.

In the developing device according to the present embodiment, a first developing roll 62 and a second developing roll 63 are arranged at a position facing the photoconductor 61 with a predetermined gap from the photoconductor 61. Further, bias power sources 71 and 72 are connected to the first developing roll 62 and the second developing roll 63, respectively, and the toner in the developer G from the first developing roll 62 and the second developing roll 63 is transferred to the photoreceptor 61. A supply bias to be supplied to the side is applied.
Further, a transport roll 64 that delivers the developer G on the first developing roll 62 to the second developing roll 63 is disposed behind the first developing roll 62 and the second developing roll 63.

In the present embodiment, the first developing roll 62, the second developing roll 63, and the transporting roll 64 have a rotatable rotating sleeves 62a to 64a and a magnet body having a plurality of magnetic poles fixedly disposed therein. 62b to 64b. The arrangement of magnetic poles is substantially the same as in the first embodiment.
A guide cover 73 that restricts the developer G on the transport roll 64 from being separated from the transport roll 64 is provided around the transport roll 64. Furthermore, the first developing roll 62 hands beneath the guide cover 73, on the lower side of the second developing roll 63 and the transport roller 64, a developer auger pair configuration for agitating and conveying the G 81 (specifically, 81a, 81b) The developer G is supplied from the supply auger 81a to the first developing roll 62. Reference numeral 74 denotes a trimmer that regulates the layer thickness of the developer G on the first developing roll 62, reference numeral 82 denotes an auger case, and reference numeral 83 denotes a partition wall that partitions the paired augers 81a and 81b.

In particular, in the present embodiment, the release guide 75 disposed in the vicinity of the second developing roll 63 is disposed downward from the vicinity of the center of the repulsive magnetic poles S2 and S3 of the second developing roll 63. Further, a guide guide 76 for guiding the developer G falling from the release guide 75 is disposed behind the release guide 75. The guide guide 76 extends behind the guide cover 73 in a gentle curved surface toward the supply auger 81a, and the downstream end reaches the supply auger 81a.
Further, the guide guide 76 is disposed at a position where the guide surface 76 a has a magnetic flux density index of 40 or less due to the magnetic force of the transport roll 64.

Therefore, the developer G peeled from the second developing roll 63 is affected by the magnetic force of the transport roll 64 disposed between the second developing roll 63 and the first developing roll 62 adjacent to the second developing roll 63. Since it is returned to the auger 81 so as not to reach, adhesion to the guide cover 73 can be suppressed, and the flow of the developer G is not impaired. Further, since the developer G is returned to the supply auger 81a, the developer G does not stay in the auger 81.
Further, in the present embodiment, the developer G supplied from the supply auger 81 a is supplied to the first developing roll 62, and this developer amount is supplied as it is to the second developing roll 63 via the transport roll 64. . Therefore, it is possible to perform stable development in the development region at the opposite portion between the two developing rolls 62 and 63 and the photoreceptor 61. In the present embodiment, since the flow of the developer G is performed via the transport roll 64, the flow of the developer G becomes smooth and stress on the developer G is reduced. It becomes possible to prevent image defects.
Furthermore, two development areas can be provided, and a sufficient image density can be realized even for high-speed development.
In the present embodiment, the configuration in which the two developing rolls of the first developing roll 62 and the second developing roll 63 are used is shown. However, there is a gap between the upstream side and the downstream side in the developer transport direction. Even if it is a structure provided with many developing rolls arrange | positioned in this way , it does not interfere. In this case, the same effects as in the present embodiment can be obtained by providing a transport roll between the adjacent development rolls among the many development rolls .
An image forming apparatus capable of high-speed development can be realized by using the developing device in the present embodiment.

Embodiment 3
FIG. 8 shows a third embodiment of the developing apparatus according to the present invention. Although the present embodiment is configured in substantially the same manner as the first embodiment, it is possible to bring the guide guide 45 closer to the transport roll 35 by providing the guide cover 43 with a magnetic shielding effect. This is different from the first embodiment. In addition, the same code | symbol is attached | subjected about the component similar to Embodiment 1, and the detailed description is abbreviate | omitted.

In the present embodiment, the guide cover 43 is configured to shield between the transport roll 35 and the guide guide 45 using a high magnetic permeability material such as permalloy, for example. Therefore, the magnetic flux density index on the guide surface of the guide guide 45 can be reduced, and the guide guide 45 can be disposed close to the guide cover 43 side.
Therefore, the auger 41 can be arranged closer to the toner collecting roll 34 side, and a smaller developing device can be realized.

In this example, the relationship between the magnetic flux density index on the guide surface of the guide guide in Embodiment 1 (see FIG. 5) and the development failure (mainly evaluation for density unevenness) is evaluated and confirmed.
In this embodiment, the developer carrier diameter is further divided into two levels of 35 μm and 50 μm, the toner density (TC) is a normal density (8%), and the low density (5%) is high to increase the magnetic attractive force. The comparison was confirmed.
As a result, as shown in FIG. 9, when the magnetic flux density index on the guide surface exceeds 60, density unevenness was confirmed under any of the conditions, and it was confirmed that the developer pooled. On the other hand, at 40 or less, no occurrence of density unevenness was confirmed under any condition, and it was confirmed that the developer did not accumulate.
Thereby, according to the present invention, even when the toner concentration fluctuates due to supply or consumption of the toner or when a carrier having a small particle diameter is used, the developer flow can be kept stable. It was confirmed that the development failure caused by the developer pool can be prevented.

It is explanatory drawing which shows the outline | summary of the image development apparatus concerning this invention. It is explanatory drawing which shows a magnetic flux density parameter | index. It is explanatory drawing which shows the numerical formula which calculates | requires a magnetic flux density parameter | index. 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. 2 is a cross-sectional view showing a configuration of an auger according to Embodiment 1. FIG. FIG. 10 is an explanatory diagram illustrating a developing device according to a second embodiment. FIG. 10 is an explanatory diagram illustrating a developing device according to a third embodiment. It is explanatory drawing which shows the 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 ... Agitation conveyance member, 7 ... Return path | route control member, 8 ... Release guide member, 9 ... conveying guide member, 9a ... guide surface, 10 ... guide cover, G ... two-component developer

Claims (7)

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 provided with a plurality of magnetic poles arranged opposite to the two developer carriers and the toner carrier and delivering a two-component developer between the two developer carriers;
The two-component developer disposed below the conveying member, rotated so as to be able to stir and convey the two-component developer along the axial direction of the toner carrier, and recovered from the supply developer carrier An agitating and conveying member that supplies the collected developer carrier while frictionally charging;
A return path regulating member for returning the two-component developer peeled from the supply developer carrying member to the stirring and conveying member;
The return path regulating member includes a release guide member that separates the two-component developer peeled from the supply developer carrying member into a range not affected by the magnetic force of the supply developer carrying member and the conveying member, and
A conveyance guide member that guides the two-component developer guided by the release guide member downward in a range not affected by the magnetic force of the conveyance member;
2. A developing device according to claim 1, wherein the conveying guide member is provided with a guide surface having a lower end portion arranged in a biased manner closer to a developer supply portion to the collecting developer carrier from the upper end portion. The developing device according to claim 1,
The developing device, wherein the guide surface of the transport guide member includes a curved surface portion having a concave shape on the transport member side. The developing device according to claim 2, wherein
The conveying member is a cylindrical body having a plurality of magnetic poles therein and capable of conveying the two-component developer, wherein the magnetic flux density at an arbitrary point P on the surface of the cylindrical body is B ₀ (mT), and the radius of the cylindrical body is R (mm), where L (mm) is the distance from the center of the cylindrical body to the point Q extending in the radial direction through the point P, the numerical value obtained by B (mT) = B ₀ R / L As a magnetic flux density index at point Q,
The developing device according to claim 1, wherein the conveyance guide member is arranged so that a magnetic flux density index from the conveyance member on the guide surface is 40 or less. The developing device according to claim 2, wherein
The agitating / conveying member is constituted by a pair of agitating / conveying members, and the downstream end position of the conveying guide member is arranged on the member side close to the developer supply site to the collecting developer carrying member among the paired members. A developing device provided. A two-component developer is carried and conveyed at a position facing the image carrier that carries the electrostatic latent image, and a development area is formed at a portion facing the image carrier, from the upstream side in the developer conveyance direction. A plurality of developer carriers disposed at intervals between the downstream sides ;
Each of the plurality of developer carriers is disposed between two adjacent developer carriers, and faces the two developer carriers and the image carrier, and the two developer carriers. A conveying member that delivers the two-component developer between
The two-component developer is disposed below the plurality of developer carrying members and the conveying member, and rotates so that the two-component developer can be stirred and conveyed along the axial direction of the developer carrying member, and is located on the most downstream side in the developer conveying direction. A stirring and conveying member that supplies the two-component developer recovered from the developer carrying member to the developer carrying member located on the most upstream side in the developer carrying direction while frictionally charging;
A return path regulating member for returning the two-component developer peeled from the developer carrying member located at the most downstream in the developer transport direction to the stirring transport member;
The return path regulating member, the two-component developer which is peeled from the developer carrying member positioned at the most downstream, is disposed between the developer bearing member adjacent to the developer carrying member and a developer carrying member A release guide member that is separated to a range that is not affected by the magnetic force of the conveying member;
A conveyance guide member that guides the two-component developer guided by the release guide member downward in a range not affected by the magnetic force of the conveyance member;
2. A developing device according to claim 1, wherein the transport guide member is provided with a guide surface that is biased and arranged closer to a developer supply portion to a developer carrying member whose lower end is positioned on the uppermost stream from the upper end. 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 provided with a plurality of magnetic poles arranged opposite to the two developer carriers and the toner carrier and delivering a two-component developer between the two developer carriers;
The two-component developer disposed below the conveying member, rotated so as to be able to stir and convey the two-component developer along the axial direction of the toner carrier, and recovered from the supply developer carrier An agitating and conveying member that supplies the collected developer carrier while frictionally charging;
A return path regulating member for returning the two-component developer peeled from the supply developer carrying member to the stirring and conveying member;
The return path regulating member includes a release guide member that separates the two-component developer peeled from the supply developer carrying member into a range not affected by the magnetic force of the supply developer carrying member and the conveying member, and
A guide cover that surrounds a part of the transport member and forms a developer transport path around the transport member;
A developing device characterized in that the guide cover is provided with a magnetic shield effect on the back surface side so as not to be affected by the magnetic force of the conveying member. An image carrier for carrying an electrostatic latent image;
An image forming apparatus comprising: the developing device according to claim 1 for developing an electrostatic latent image on the image carrier.

Images