JPH08137270A - Developing device - Google Patents

Abstract

PURPOSE: To secure complete developing performance without disturbing an already formed toner image on a photoreceptor at the time of forming a multicolor image. CONSTITUTION: A magnet member 3 fixed and set in a rotatable non-magnetic sleeve 2 is provided with a developer regulating magnetic pole 6, a pair of developing magnetic poles 7 positioned on the downstream side of the magnetic pole 6 and consisting of a pair of magnetic poles having different polarity each other, where the magnetic pole having a different polarity from the magnetic pole 6 is arranged on an upstream side, and a pair of peeling and carrying magnetic poles 8 positioned on the downstream side of the pair of magnetic poles 7 and consisting of a pair of magnetic poles having the same polarity each other, which is different from the polarity of the magnetic pole on the downstream side of the pair of magnetic poles 7. In the vicinity of the interpole part of the pair of magnetic poles 7 on the sleeve 2, there exists an area where a component Fr in the normal direction of the magnetic force acting on developer G acts in a direction toward the center of a developer carrier 1 and a component Ft in the tangential direction of the magnetic force acts on the rotating direction of the sleeve 2, and further the ratio of the size of the components in the normal direction and the tangential direction of the magnetic force |Ft/Fr| may be >0.5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in an image forming apparatus such as an electrophotographic copying machine or a printer for forming a monochromatic or multicolor image,
In particular, the present invention relates to an improvement of a developing device that forms a magnetic brush on a developer bearing member to develop a latent image on a photosensitive member.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus in which an electrostatic latent image formed on a photoconductor is developed by a developing device and then transferred onto recording paper, a developer is brought into contact with the surface of the photoconductor to form an electrostatic latent image. A large number of developing devices using a two-component magnetic brush that visualizes a latent image have been proposed. This method uses toner density control,
Although it has a problem of increasing the size of the apparatus, it is a mainstream developing method from the viewpoint of image quality characteristics and maintainability. But,
In recent years, with the development of higher image quality and multicolor recording, a multicolor image forming process has been proposed in which an electrostatic latent image formed on a photoconductor is visualized with toner of plural colors and these are collectively transferred to a recording paper. Has been done. When the developing device using the contact type two-component magnetic brush described above for the developing process is adopted for the latent image of the second and subsequent stages of such a multicolor image forming process, the toner on the photoreceptor formed before the preceding stage is used. Technically appropriate problems such as rubbing and destroying an image and mixing toner on a photoconductor into a developing device have been found.

In order to solve such technical problems,
Many so-called non-contact developing devices have been proposed, which perform development without bringing the surface of the photoconductor into contact with the developer. As a non-contact developing device of this type, for example, as disclosed in Japanese Patent Publication No. 2-4903, a photoreceptor and a developing magnetic brush are brought into non-contact with each other, and the developer layer is magnetically, electrically or It is known to apply a disturbing effect by mechanical means to develop. In this developing device, when a multicolor image is formed, it is possible to form a good image that is not disturbed by mechanical contact between the magnetic brush of the developing device in the subsequent stage and the toner image on the photoconductor formed in the preceding stage, Further, it is possible to prevent the toner on the photoconductor from entering the developing device.

In particular, as disclosed in Japanese Examined Patent Publication No. 4-36383, the magnetic poles of the magnet roll are arranged so as to avoid the position where the developing sleeve and the photosensitive member are most closely contacted with each other, and the horizontal magnetic field component is formed in the developer layer. In the type that develops under an oscillating electric field while applying a magnetic field, a uniform thin layer of developer can be obtained, so during multi-color image formation, the mechanical contact between the magnetic brush and the toner image during the second and subsequent development processes. You can avoid the disturbance due to
In addition, a good image without color mixture can be obtained. However, these developing devices can be applied not only to the multicolor image forming process but also as a monochromatic recording developing device, and since the magnetic brush is not in contact with the surface of the photoconductor,
It is possible to expect faithful image reproduction for the input image.

[0005]

However, in the developing device disclosed in Japanese Patent Publication No. 4-36383, a horizontal and magnetic field component acts on the developer layer to obtain a thin and uniform developer layer. In order to prevent the toner image already formed on the photoconductor from being disturbed at the time of forming a color image, it has been found that the developing property of the toner itself cannot be sufficiently enhanced, that is, a so-called developing property is deteriorated.

When the problem of deterioration of developability in the non-contact state is examined, when a horizontal magnetic field component is applied to the developer layer, the developer particles are magnetically arranged along the lines of magnetic force and are densely arranged on the surface of the developing sleeve. It was found that the developer, which forms a uniform thin layer, but contributes to the development is only one or two surface layers. It is considered that this is because the developer layer is in a state of being strongly packed along the magnetic lines of force, so that the toner particles in the developer near the developing sleeve cannot move to the surface layer.

The present invention is intended to solve the above technical problems, and ensures sufficient developability without disturbing the toner image already formed on a photoconductor during multicolor image formation. The present invention provides a novel developing device that can be used.

[0008]

That is, the present invention provides:
As shown in FIG. 1, a rotatable non-magnetic sleeve 2 has a developer carrying member 1 on which a magnet member 3 is fixedly installed, and on the developer carrying member 1, two-component development including toner and magnetic carrier is carried out. In the developing device which carries the agent G and develops the latent image Z formed on the latent image carrier 4 by the two-component developer G of the developer carrier 1, the magnet member 3 is
A developer regulating magnetic pole 6 (S2 in the figure) that acts on the developer G together with the developer regulating means 5 to regulate the transport amount of the developer G, and a downstream side of the developer regulating magnetic pole 6 in the rotation direction of the non-magnetic sleeve 2. Side and a developer magnetic pole pair 7 composed of a magnetic pole pair having a polarity different from that of the developer regulating magnetic pole 6 and arranged on the upstream side.
(S1, N1 in the figure) and a magnetic pole pair which is further downstream in the rotation direction of the non-magnetic sleeve 2 of the developing magnetic pole pair 7 and which has a different polarity from the magnetic pole on the downstream side of the developing magnetic pole pair 7. The peeling / conveying magnetic pole pair 8 (N2, N3 in the figure) is provided, and in the vicinity of the gap between the developing magnetic pole pair 7 on the non-magnetic sleeve 2, the normal direction component Fr of the magnetic force acting on the developer G is The tangential component Ft of the magnetic force is directed toward the center of the developer carrying member 1.
Acts in the rotation direction of the non-magnetic sleeve 2, and the ratio of the magnitude of the normal direction component of the magnetic force to the tangential direction component | Ft / Fr
There is a region where | is 0.5 or more, and preferably | Ft / Fr | is 0.7 or more.

In such technical means, the region satisfying the magnetic force condition is a region where the sliding portion of the developer G is formed. The magnetic force condition will be described. First, when the tangential component Ft of the magnetic force acts on the developer G in the rotation direction of the sleeve 2, the frictional force between the sleeve 2 and the developer G causes the rotation direction of the sleeve 2. Acts in the opposite direction.
Therefore, when the tangential component Ft of the magnetic force exceeds the frictional force, the developer slides. If the tangential component Ft of the magnetic force is opposite to the rotation direction of the sleeve 2 and, for example, the ratio | Ft / Fr | of the magnitudes of the normal component Fr and the tangential component Ft of the magnetic force is 1.0 or more, The developer G is not conveyed and a pool is generated, and the developer carrier flies from the upper layer portion thereof, which causes troubles such as carrier adhesion during image formation.

When the normal component Fr of the magnetic force acts outward from the center of the sleeve 2, the developer G is separated from the sleeve 2 and flying occurs. When an image is formed in this case, the magnetic carrier adheres to the latent image carrier. Therefore, the normal direction component Fr of the magnetic force
Must be at least towards the center of the sleeve 2.

Further, even if the action direction of each component of the magnetic force satisfies the above condition, the ratio | Ft / Fr | of the magnitudes of the normal component Fr and the tangential component Ft of the magnetic force is less than 0.5. Then, since the developer G does not slide, | Ft / Fr | needs to be 0.5 or more, preferably 0.7 or more.

In order to form such a developer sliding portion, the direction of the tangential component Bt of the magnetic flux density in the vicinity of the developing magnetic pole pair 7 is slightly away from the non-magnetic sleeve 2 and the sleeve 2 in the normal direction. It is necessary to configure the magnet member 3 so that it acts in the opposite direction in the open position.

Such a magnetic field forms a tangential component of the magnetic flux density on the sleeve 2 (a behavior promoting magnetic field component with respect to the developer), and a pair of different polarity magnetic poles, and the sleeve 2 arranged so as to sandwich the magnetic pole pair. Is formed by interaction with a pair of different polarity magnetic poles for forming a tangential component (horizontal magnetic field component) of the magnetic flux density at a position slightly away from the normal direction. At this time, two pairs of different magnetic poles as the magnetic poles forming the developer sliding portion may be arranged in the magnet member 3, but the magnet member 3
When the developer carrying member 1 having a diameter of 20 mm or less is formed, the degree of freedom of the angle occupied by each magnetic pole, the magnitude of the magnetic flux density, and the like becomes narrow, which makes it difficult to form. still,
Although it can be improved by the material of the magnet member 3, it is not preferable because it causes an increase in the cost of the device.

Therefore, as shown in the tangential direction component reversal region of the magnetic flux density in FIG. 2, the direction of the tangential direction component Bt of the magnetic flux density on the non-magnetic sleeve 2 is the developing magnetic pole pair 7 (N1, S).
In the direction of the magnetic flux density formed by 1), at a position slightly away from the non-magnetic sleeve 2 in the normal direction (in this example, at a position 1.5 mm away from the sleeve surface in the normal direction),
The magnetic flux density is oriented between the developer regulating magnetic pole 6 (S2) and the upstream pole (N2) of the peeling / conveying magnetic pole pair 8. That is, it is preferable that the developer magnetic pole 6 and the upstream pole of the peeling / conveying magnetic pole pair 8 are also used as the different polarity magnetic pole pair for forming the horizontal magnetic field component.

[Action]

According to the above-mentioned technical means, the area between the developing magnetic pole pairs 7 which satisfies the above-mentioned magnetic force condition, in other words, the sleeve 2 and a position slightly distant from the sleeve 2 in the normal direction. In the region where the tangential component of the magnetic flux density inverts and acts, the developer sliding portion on which the developer G slides in the rotation direction of the sleeve 2 is formed. Here, since the slidable developer hits the developer G layer on the downstream side, the toner is knocked out. Therefore, when developing is performed in a state where the developer G and the surface of the latent image carrier 4 are not in contact with each other, in addition to the activation of the movement of the developer G, the developer G layer is strongly packed. Therefore, the transfer of toner particles from the developer G layer to the latent image carrier 4 is promoted.

Further, when all or part of these regions are within the effective developing region that substantially contributes to the development and the developer G and the surface of the latent image carrier 4 are brought into contact with each other to perform the development, Since the contact is softer than in the case of contacting a normal high-density developer layer, higher developability can be obtained as compared with the conventional case. Further, even when a toner image is already formed as in a multicolor image forming apparatus, it is difficult to disturb the toner image.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the embodiments shown in the accompanying drawings. FIG. 3 shows an embodiment of a multicolor image forming apparatus using the developing device according to the present invention. In the figure, 11 is a negatively charged photosensitive member that rotates in the a direction, 12,
15 are the first and second chargers (scorotron), 13,
16 is the first and second ROS [Raster Output Scannor, respectively]
Abbreviation] (optical writing device: a semiconductor laser with a resolution of 400
(Spot per inch), 14 and 17 are first and second developing devices having the same charging polarity but different colors, and 18 is the photoconductor 11
A pre-transfer lamp for irradiating light onto the two-color toner image formed thereon to make the potentials uniform, and 20 for recording the two-color toner image on the photoconductor 11 processed by the pre-transfer lamp 18 for recording paper. A transfer charging device for collectively transferring to 19; a peeling charging device for peeling the recording paper 19 from the photoconductor 11 after the transfer;
Is a cleaner for removing the residual toner on the photoconductor 11, 23
Is a discharge lamp for removing the residual charge on the photoconductor 11. The recording paper 19 after transfer passes through a fixing device (not shown), and the unfixed toner image on the recording paper 19 is fixed.

In this embodiment, the first developing device 14 develops by a contact type magnetic brush developing method, and the second developing device 17 develops by a system in which the developer and the surface of the photoreceptor 11 are not in contact with each other in a static state. . The details of the second developing device 17 are shown in FIG. In the same figure, the second developing device 17 has a developing roller 171 having a magnet roller 173 in a rotatable non-magnetic sleeve 172 having an average surface roughness of 10 to 50 μm and a non-magnetic sleeve 172 and a constant gap. A developer layer thickness regulating member 174 made of a non-magnetic member, a paddle 175, and an auger 176 are main components.

In this embodiment, the magnet roll 17
As shown in FIG. 5, 3 has an upstream side developing magnetic pole N1 and a downstream side developing magnetic pole S1 as a developing magnetic pole pair arranged with an effective developing area m that substantially contributes to the development interposed therebetween. A trimming magnetic pole S2 which is arranged on the upstream side of the magnetic pole N1 at a position facing the developer layer thickness regulating member 174 to form a thin layer of the developer, and an effective developing area which is arranged on the downstream side of the downstream developing magnetic pole S1. The pick-off magnetic pole N2 that removes the developer after passing m from the sleeve 172, and the developer that is disposed on the downstream side of the pick-off magnetic pole N2 to remove the developer.
It has a pickup magnetic pole N3 to be attracted to the top.

The paddle 175 has a pickoff magnetic pole N3.
Has a function of sending the developer separated from the sleeve to the auger 176 side. The auger 176 has a function of stirring the separated developer and stirring the toner supplied from a toner hopper (not shown) and the developer in the developing device.

FIG. 6 shows the distribution of the magnetic flux density on the sleeve 172 of the magnet roll 173 used in this embodiment, and FIG. 7 shows the direction of the magnetic flux density near the developing magnetic pole pair. In FIG. 6, the solid line represents the component Br of the magnetic flux density in the normal direction.
The dashed-dotted lines respectively indicate the tangential component Bt of the magnetic flux density. The trimming magnetic pole S2 is 530 G (Gauss), the upstream developing magnetic pole N1 is 310 G, and the downstream developing magnetic pole S1 is 300.
G, the pickoff magnetic pole N2 is 575G, the pickup magnetic pole N3 is 350G, and the angle between S2 and N2 is 185.
The angle between N1 and S1 is 57.5.

Further, as shown in FIG. 7, the developing magnetic pole pair N
On the sleeve 172 between the poles of 1 and S1 or in the vicinity thereof, the direction of the magnetic flux density is from the upstream developing magnetic pole N1 to the downstream developing magnetic pole S1, whereas the normal line of the sleeve 172 is more than that. It is understood that at a position slightly distant in the direction (a position 1.25 mm apart from the surface of the sleeve 172 in this embodiment), the direction is opposite. At this time, the direction of the magnetic flux density on or in the vicinity of the sleeve 172 between the poles of the developing magnetic pole pair N1 and S1 coincides with the direction of the magnetic flux density formed by the developing magnetic pole pair N1 and S1. The direction of the magnetic flux density at a position slightly apart from the normal direction of the sleeve 172 matches the direction of the magnetic flux density formed by the trimming magnetic pole S2 and the pickoff magnetic pole N2 pair sandwiching the developing magnetic pole pair N1 and S1.

Further, FIG. 8 shows a normal direction component Fr and a tangential direction component Ft of the magnetic force at a position 100 μm away from the sleeve.
And its ratio | Ft / Fr |. Development magnetic pole pair N
The normal direction component Fr of the magnetic force near the gap between 1 and S1 is negative, which indicates that the developer acts on the sleeve 172 in the carrying direction. Also, the tangential component F of the magnetic force
t is a region where the value changes from negative to positive. That is, it indicates that the force is changing from the direction opposite to the rotating direction of the sleeve 172 to the rotating direction. Here, there is a region where | Ft / Fr | exceeds 0.7, and this region is considered to be a factor for sliding the developer.

However, the normal direction component Fr and the tangential direction component Ft of the magnetic force used here are obtained by the following equations 1 and 2. Br (r, θ) and Bt (r, θ) used in these equations are r = 9.1 m
m and Δr = 50 μm and Δθ = 0.36 °, which are the normal direction component and the tangential direction component of the magnetic flux density. Further, the magnetic force that originally acts on the developer is determined by the magnetic field (magnetic flux density) formed by the magnet roll, the shape of the developer, the magnetic characteristics, and the like. However, here, since it is assumed that the developer has a uniform shape and magnetic characteristics and the developer chain is formed along the magnetic field, it is expressed as a coefficient C.

[0025]

[Equation 1]

[0026]

[Equation 2]

In this embodiment, as shown in FIG. 5, the vicinity of the magnetic poles of the developing magnetic pole pair N1 and S1 of the magnet roll 173 is closest to the photosensitive member 11, and the developer layer thickness regulating member 174.
Because the amount of developer supplied by is regulated,
The developer layer does not contact the surface of the photoconductor 11 in a static state. Further, the direction of the tangential direction component of the magnetic flux density is inverted in the vicinity of the sleeve 172, and the direction of the tangential direction component of the magnetic flux density at a position distant from the sleeve 172 in the normal direction is the direction of the tangential direction component of the magnetic flux density near the sleeve 172. The area that reverses the direction is included in the effective developing area m.

FIG. 9 is a schematic view showing a case where the developer G layer is formed on the sleeve 172. As shown in the figure, in this embodiment, the developer G is in a static state when the sleeve 17
There is a prohibited area K on the surface 2 where it is difficult to adhere. In the dynamic state where the sleeve 172 rotates, the carrier chain of the developer G slides and moves in the prohibited area K.

Next, the image forming process of the multicolor image forming apparatus according to this embodiment will be described with reference to FIG. In the charging step a, the surface of the photoconductor is uniformly charged (first initial charging potential VDDP
1) In the first exposure step b, after forming a first latent image corresponding to the original information (the image portion potential of the original is VL1 and the non-image portion potential VH1), the reverse development is performed in the first developing step c. The image portion of the first latent image is developed by (developing bias potential VB1). Next, in the recharging step d, the surface of the photoconductor is uniformly recharged (second initial charging potential VDDP2), and in the second exposure step e, the second latent image (of the original document) corresponding to other information of the original document. After forming the image portion potential VL2 and the non-image portion potential VH2), the image portion of the second latent image is inverted by the second developing step f (developing bias potential VB2) having a color different from the first developing step. develop. Through these steps, two color toner images are formed on the photoconductor.

Images were formed under the following experimental conditions according to the above image forming process. ● Photoreceptor Organic photoreceptor (negative charging type) Drum outer diameter 84mm ● Process speed 160mm / sec ● First developer (toner concentration 3.0%) ・ Two-component system (negatively charged red toner) ・ Carrier average Ferrite carrier having a particle size of 100 μm ・ Red toner 90 parts of styrene-n-butyl methacrylate copolymer, 8 parts of red pigment resole scarlet (manufactured by BASF), and 2 parts of charge control agent (E-84, manufactured by Orient Chemical Co.) Are mixed, melt-kneaded, and then finely pulverized to have an average particle size of 12 μm, and the carrier is negatively charged. ● Second developer (toner concentration 8.0%) ・ Two-component system (negatively charged black toner) ・ Carrier Polymethylmethacrylate copolymer (35 parts) and magnetite (65 parts) are mixed, melt-kneaded, and then finely pulverized. Powder-dispersion type, average particle diameter 45 μm, density 2. 2 g / cm
³ things. Black toner 93 parts of styrene-n-butylmethacrylate copolymer and 7 parts of carbon black are mixed, melt-kneaded, and then finely pulverized to have an average particle size of 11 μm, which is negatively charged to the carrier. ● Parameters of first developing device (contact type development) ・ DRS (gap between photoconductor and sleeve) 0.6mm ・ MSA (set angle of main development pole) +5 degrees ・ TG (gap between layer thickness control member and sleeve) 0.50mm -Development sleeve outer diameter 20 mm-Development sleeve rotation speed 480 mm / sec-Development sleeve rotation direction With (same direction as the photoconductor) -Second development device parameter (development according to the present invention) -DRS 0.5 mm-MSA Between magnetic poles・ TG 0.2 mm ・ Development sleeve outer diameter 18.0 mm ・ Development sleeve rotation direction With ● Applied voltage to transfer charger AC 400 Hz. VP-P
8.5 kV. DC + 2.5kV

In addition, the potential condition for latent image formation shown in FIG. 10 is that the first initial charging potential VDDP1 is -55 as the first image.
0 V, the first non-image portion potential VH1 is −550 V, the first image portion potential VL1 is −100 V, and the first developing bias potential VB1 is D.
C-450V, while the second image has a second initial charging potential VDDP2 of -550V and a second non-image portion potential VH2 of -5.
The second image portion potential VL2 was set to -100V and the second developing bias potential VB2 was set to DC-450V. Furthermore,
For the second developing bias, VP-P 1.0 kV, frequency 2.
An alternating voltage of 0 kHz was applied.

When an image is formed under the above conditions, there is no color mixture of the second developing toner in the first image, and the second image is 1.
A reflection density of 4 or more was obtained. Further, FIG. 11 shows the relationship between the contrast potential (VL2-VB2) and the reflection density of the second image at this time.

Further, in this embodiment, the fixing position of the magnet roll 173 of the second developing device 17 is deviated, and the developer sliding portion is changed so as to be closest to the photosensitive member 11, and other conditions are set. An experiment was conducted in the same manner as in. In this case, a relatively weak portion of the magnetic force normal direction component Fr comes into closest contact with the photoconductor 11 and an AC voltage is applied to the second developing bias, so that the second developing in the first image is performed. Although there was no toner color mixture and the second image also had a reflection density of 1.4 or higher, a relatively large amount of carrier adhesion was observed between the lines of the high frequency line image. Therefore, it is confirmed that it is preferable to set the developer sliding portion at a position deviated from the position closest to the photoconductor 11.

Further, in this embodiment, an experiment was conducted in which the developer carrying amount of the second developing device 17 was increased and other conditions were the same as in the embodiment. At this time, the developer accompanies the rotation of the sleeve 172, and the developer near the sleeve 172 is the first embodiment.
In the same manner as in the case of (1), at the position apart from the sleeve 172, it flew along the magnetic line of force at that position and moved to the downstream side. Therefore, a phenomenon was observed in which the upper layer portion of the developer layer was brought into contact with the surface of the photoconductor 11 to perform development. Even in this case, there is no color mixture of the second developing toner in the first image and a reflection density of 1.4 or more can be obtained in the second image portion, but a relatively large amount of carrier adhered between the lines of the high frequency line image. Was observed. Therefore, it is confirmed that it is preferable to select an appropriate amount of developer that does not cause carrier adhesion.

Comparative Example As the magnet roll 173 of the second developing device 17 used in the example, the magnetic flux density pattern shown in FIG. 12 (this magnetic flux density pattern shows the normal direction component of the magnetic flux density, and the trimming magnetic pole S2 is used). 630G (Gauss), upstream developing magnetic pole N1
Is 790G, the downstream developing magnetic pole S1 is 830G, the pickoff magnetic pole N2 is 680G, and the pickup magnetic pole N3 is 500G.
Further, the S2-N2 angle is 215 ° and the N1-S1 angle is 80 °. ) Magnetic roll (developing sleeve outer diameter 18.0 mm) was used and image formation was performed using the parameters of Example 1, but no color mixing of the second developing toner in the first image was observed, but 0 Only a reflection density of about 0.8 was obtained. In addition, the contrast potential (V
FIG. 13 shows the relationship between the reflection density of the second image and L2-VB2).
Shown in

[0036]

As described above, according to the present invention,
By devising the action direction and magnitude of the magnetic force in the vicinity of the gap between the developing magnetic pole pairs, a developer sliding portion is generated near the gap between the developing magnetic pole pairs, and the sliding developer and the downstream developer layer are formed. The collision of the toner promotes the transfer of the toner from the developer layer to the latent image bearing member, so that it is possible to obtain sufficient developability in non-contact development, and it is possible to form a toner image already formed during multicolor image formation. It is possible to secure sufficient developability without disturbing the toner image on the latent image carrier.

Further, in the present invention, in order to form the developer sliding portion, the direction of the tangential direction component of the magnetic flux density in the vicinity of the developing magnetic pole pair is slightly separated from the sleeve in the normal direction. It is necessary to dispose a pair of magnetic poles having different polarities so as to act in opposite directions at the position so as to sandwich the developing magnetic pole pair. Since the number of magnetic poles of the magnet member is reduced by also serving as the upstream magnetic pole of the carrier magnetic pole pair, even when a developer carrying member having a diameter of 20 mm or less is formed by using a small-diameter magnet member. Further, it is possible to easily manufacture with a stable magnetic flux density, and it is possible to easily realize an inexpensive and small developing device.

Further, in the present invention, since the magnetic poles of different polarities are alternately arranged as the upstream poles of the developer regulating magnetic pole, the developing magnetic pole pair, and the peeling / conveying magnetic pole pair, the same polarity is provided near the effective developing area. As compared with the case where the magnetic pole pair is formed, the magnet member can be easily manufactured at low cost.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a developing device according to the present invention.

FIG. 2 is an explanatory diagram showing a tangential component of a magnetic flux density near a sleeve in the developing device of FIG.

FIG. 3 is an explanatory diagram showing an embodiment of a multicolor image forming apparatus using a developing device to which the present invention is applied.

FIG. 4 is an explanatory diagram showing a schematic configuration of a second developing device according to the embodiment.

FIG. 5 is an explanatory diagram showing a magnet roll configuration of the second developing device according to the embodiment.

FIG. 6 is a graph showing a magnetic flux density distribution of the magnet roll.

FIG. 7 is an explanatory diagram showing the direction of magnetic flux density on the sleeve of the magnet roll.

FIG. 8 shows a normal direction component Fr and a tangential direction component F of the magnetic force at a position 100 μm away from the sleeve of the second developing device.
It is a graph which shows t and its ratio | Ft / Fr |.

FIG. 9 is an explanatory diagram showing the behavior of the developer on the sleeve near the pair of developing magnetic poles of the magnet roll.

FIG. 10 is an explanatory diagram illustrating an image forming process of the multicolor image forming apparatus according to the embodiment.

FIG. 11 is an explanatory diagram showing the relationship between the contrast potential and the reflection density in the second development according to the embodiment.

FIG. 12 is an explanatory diagram showing the magnetic flux density on the sleeve of the magnet roll used in the comparative example.

FIG. 13 is an explanatory diagram showing the relationship between the contrast potential and the reflection density in the second development in the comparative example.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Developer carrying body, 2 ... Non-magnetic sleeve, 3 ... Magnet member, 4 ... Latent image carrying body, 5 ... Developer regulating means, 6 ... Developer regulating magnetic pole, 7 ... Developing magnetic pole pair, 8 ... Separation / true phase Magnetic pole pair, G
... two-component developer, Z ... electrostatic latent image, Ft ... tangential component of magnetic force, Fr ... normal component of magnetic force

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yoichi Watanabe 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.Ebina Business Office (72) Inventor Shigehiko Hasenami 2274 Hongo, Ebina City, Kanagawa Fuji Xerox Co., Ltd.Ebina Co., Ltd. In the office

Claims (2)

[Claims] 1. A rotatable nonmagnetic sleeve (2) has a developer carrier (1) on which a magnet member (3) is fixedly installed, and toner and magnetic material are provided on the developer carrier (1). A two-component developer (G) composed of a carrier is carried, and the latent image (Z) formed on the latent image carrier (4) is developed by the two-component developer (G) on the developer carrier (1). In such a developing device, the magnet member (3) acts on the developer (G) together with the developer regulating means (5) to regulate the amount of the developer (G) conveyed. ) And a magnetic pole having a polarity different from that of the developer regulating magnetic pole (6) on the downstream side in the rotation direction of the non-magnetic sleeve (2) and on the upstream side. A developing magnetic pole pair (7) composed of a magnetic pole pair, and a change in the rotation direction of the non-magnetic sleeve (2) of the developing magnetic pole pair (7). On the non-magnetic sleeve (2), there is a peeling / conveying magnetic pole pair (8) which is located on the downstream side and which is of the same polarity as that of the developing magnetic pole pair (7). In the vicinity of the gap between the developing magnetic pole pair (7), the normal component Fr of the magnetic force acting on the developer (G) is directed toward the center of the developer carrier (1), and the tangential component Ft of the magnetic force is applied. Acts in the rotation direction of the non-magnetic sleeve (2), and further, there is a region where the ratio | Ft / Fr | of the magnitudes of the normal component and the tangential component of the magnetic force is 0.5 or more. And developing device. 2. The developing device according to claim 1, wherein the tangential component Bt of the magnetic flux density is near the developing magnetic pole pair (7).
The orientation is on the non-magnetic sleeve (2) and the sleeve (2)
The tangential component Bt of the magnetic flux density on the non-magnetic sleeve (2) acts in the opposite direction at a position slightly away from the normal direction.
Is the direction of the magnetic flux density formed by the developing magnetic pole pair (7), and the direction of the tangential direction segment Bt of the magnetic flux density at a position slightly distant in the normal direction from the sleeve (2) is the developer magnetic pole. A developing device characterized in that the direction of the magnetic flux density is formed between (6) and the upstream pole of the peeling / conveying magnetic pole pair (8).