JPH1184869A - Developing device, process cartridge and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device capable of suppressing/preventing the flowing through of a developer in the longitudinal direction of a developing sleeve and to prevent the leakage of the developer caused by impact, etc., a process cartridge and an image forming device. SOLUTION: The developing sleeve 31 having a magnet roller 32 inside is arranged in the opening part of a developing container 30 and magnet seal members 34 for regulating the movement of toner are arranged on the outer peripheries on the side of the developing container 30 at both ends of the developing sleeve 31, in states of noncontact with the developing sleeve 31. On the inner periphery of the magnet seal member 34 is magnetized to obtain many N- and S-magnetic poles. The magnet seal member 34 is formed so that a magnetic flux density value in the position between the magnetic poles on the surface of the sleeve 31 of the magnet seal member 34 is made into 80% to <=120% of that in the magnetic pole position on the surface of the sleeve 31 of the magnet seal member 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device, a process cartridge and an image forming apparatus for developing an image with a magnetic developer when an image is formed by an electrophotographic recording method or the like.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus for forming an image by an electrophotographic recording method or the like, an electrophotographic photosensitive member as an image carrier and a process means acting on the electrophotographic photosensitive member are integrally formed as a cartridge. In some cases, a process cartridge system in which this cartridge is configured to be detachable from the image forming apparatus main body is employed.

According to this process cartridge system,
The maintenance of the main members of the apparatus can be performed by the user himself without replacing the service cartridge by exchanging the process cartridge, so that the operability can be remarkably improved. Therefore, the process cartridge system is widely used in image forming apparatuses such as printers.

In a developing device which is a developing means incorporated in such a process cartridge, a developer image carrier capable of transporting the developer to a developing area for developing an electrostatic latent image by rotating while carrying the developer is provided. Sealing members for preventing the developer from flowing out of the developing area are provided at both ends of the developing sleeve.

[0005] As a seal member for preventing the developer from flowing out, an elastic material such as felt or foamed rubber is widely used. FIGS. 10 and 11 show examples in which a seal member is used. FIG. 10 is a front explanatory view showing a main part of a developing device incorporated in a conventional process cartridge, and FIG. 11 is a side explanatory view showing a main part of the developing device.

As shown in FIG. 10, a developing roller 31 for carrying a developer has a magnet roller 32 disposed therein. Further, as shown in FIG.
1 is rotatably supported by the developing container 30 via a sleeve bearing 35 provided at a predetermined position of the developing container 30 containing the developer, and the developer supplied from the developing container 30 After being adhered to the surface of the developing sleeve 31 by the magnetic force and the layer thickness is regulated to a predetermined thickness by the developing blade 33 in contact with the developing sleeve 31, the developing blade 31 rotates relative to the developing sleeve 31 as the developing sleeve 31 rotates. The developer is conveyed to a developing area, which is a position facing the latent image on the photosensitive drum disposed at a position where the developer is conveyed, and the developer conveyed to the developing area adheres to the latent image to perform development.

At this time, an elastic seal member 36 is attached to the developing container 30 side of the developing sleeve 31 mounted on the developing container 30 at both ends in the longitudinal direction outside the developing region of the developing sleeve 31. This elastic sealing member 36
Is formed in a substantially arc-shaped cross section along the outer peripheral surface of the developing sleeve 36 by, for example, felt or foam rubber.
The elastic seal member 36 is pressed against the outer peripheral surface of the developing sleeve 31 to prevent the developer from flowing from the surface of the developing sleeve 31 to the longitudinal end.

In the developing device using the elastic seal member having the above-described structure, the elastic seal member 36 is in pressure contact with approximately half of the outer peripheral surfaces of both ends of the developing sleeve 31, so that the developing sleeve that rotates during the developing operation is rotated. 31, the load is large,
The elastic seal member 3 is contacted with the developing sleeve 31 by contact.
In addition, there is a problem that the sealability is deteriorated due to the deterioration of the toner cartridge 6, and a small amount of toner may enter the gap between the developing sleeve 31 and the elastic seal member 36. In some cases, the rotation speed is increased or the fluctuation of the torque is increased to cause rotation unevenness, which may adversely affect image formation.

Therefore, in order to solve these problems, a developing sleeve is provided at a position where an elastic seal member is provided.
Instead of the elastic seal member, a magnet seal member is arranged at predetermined intervals along the outer peripheral surfaces of both ends of the developing sleeve,
There has been proposed a method for preventing the developer from flowing out.

FIG. 12 is an explanatory front view showing a developing device using a magnet sealing member. The magnet seal members 37 provided at both ends of the developing sleeve 31 are magnets formed in a substantially arc-shaped cross section along the outer periphery of the developing sleeve 31, and NS poles are magnetized on the inner peripheral surface thereof into multiple magnetic poles. Further, the magnet seal member 37 is disposed at both ends of the developing sleeve 31 having the magnet roller 32 therein with a certain gap g from the outer peripheral surface on the side of the developing container, and the gap g is maintained. And is attached to the developing container together with the developing sleeve 31. The magnet seal member 37 has a magnetic pole provided on the inner peripheral surface of the magnet seal member at a position facing the magnetic pole of the magnet roller.

The magnet sealing member 37 restrains the developer between the end of the developing sleeve and the magnet sealing member by a magnetic field formed by the magnet roller 32 and the magnet sealing member 37 in the developing sleeve 31. By forming a seal portion and closing the developer that has moved to the longitudinal end of the developing sleeve with the seal portion, it is possible to prevent the developer from flowing out from the end of the developing sleeve.

When the above-mentioned magnet seal is used, the developing sleeve and the magnet seal member are kept out of contact with each other, and the rotational torque of the developing sleeve becomes extremely small. Therefore, the noise motor is small and inexpensive. In addition, the fluctuation of the rotation torque is small, the uneven rotation of the developing sleeve and the photosensitive drum hardly occurs, and there is no wear of the magnet seal member. Therefore, the use thereof is semi-permanent, and the device can be recycled.

[0013]

However, in the case where the above-mentioned conventional magnet seal member is used, sufficient consideration is not given to the relationship between the magnetic flux density and the magnetic force between the magnet inside the developing sleeve and the magnet seal member. Therefore, there is a problem that the developer may leak from the end of the developing sleeve depending on the use condition.

For example, when the developing device is used, a large amount of the developer carried on the developing sleeve is moved to the longitudinal end of the developing sleeve as the developing sleeve rotates, and the moved developer is moved to the end of the developing sleeve. In some cases, a problem such as slipping through a seal portion formed between the magnetic seal member and the magnet seal member may occur.

Accordingly, the present invention provides a developing apparatus, a process cartridge, and an image forming apparatus capable of suppressing and preventing the developer from passing through in the longitudinal direction of the developing sleeve, and suppressing and preventing the leakage of the developer caused by an impact or the like. It is intended to provide a device.

[0016]

According to a first aspect of the present invention, an object of the present invention is to provide a developing container for accommodating a magnetic developer, a plurality of rotatably supported by the developing container, A developer carrier capable of carrying and transporting the developer in a predetermined direction by arranging a magnet having a magnetic pole, and a predetermined interval at a position opposed to the developer carrier on the developing container side at both ends of the developer carrier at both ends of the developer carrier. In the developing device having the magnet seal member disposed therein, the magnet seal member is formed by magnetizing the NS poles to multiple magnetic poles on the inner peripheral surface thereof, and is formed on the surface of the developer carrier by the magnet seal member. The value of the magnetic flux density at the position between the magnetic poles is 80 times the value of the magnetic flux density at the magnetic pole position on the developer carrier surface by the magnet seal member.
% And 120% or less.

Further, according to the second invention of the present application, the above object is achieved by disposing a magnet inside a developer carrier in a fixed manner within the developer carrier, and at least a magnet sealing member and a magnet inside the developer carrier. This is achieved by providing magnetic poles of different polarities at positions facing each other.

According to a third aspect of the present invention, there is provided a process cartridge which is detachably formed in an image forming apparatus main body and has at least an image carrier and a developing device. Developing device,
This is achieved by the developing device according to the first or second invention.

Further, according to the fourth aspect of the present invention, the object is to provide at least a developing container containing a magnetic developer, and a plurality of magnetic poles rotatably supported by the developing container and inside the developing container. A developer carrying member capable of carrying and transporting the developer in a predetermined direction by disposing the magnet having the
In an image forming apparatus provided with a developing device having a magnet seal member disposed at a predetermined interval at a position opposite to the developer carrying member on the developing container side at both ends of the developer carrying member, the first as the developing device This is achieved by using the developing device of the invention of the second or the second invention, or by disposing the process cartridge of the third invention in the developing device.

In other words, according to the first aspect of the present invention, in the magnet seal member formed by magnetizing the NS pole to the multiple magnetic poles on the inner peripheral surface thereof, the surface of the developer carrying member by the magnet seal member is provided. The value of the magnetic flux density at the position between the magnetic poles at is
It is 80% or more and 120% or less of the value of the magnetic flux density at the magnetic pole position on the developer carrying member surface by the magnet seal member, and the normal magnetic field and the tangential magnetic field between each magnetic pole of the magnet seal member are reduced. By increasing the combined magnetic field and constraining the magnetic toner by the action of the magnetic field, good sealing properties can be maintained.

According to the second aspect of the present invention, magnetic poles having different polarities are provided at positions opposed to the magnet sealing member and the magnet fixedly arranged in the developer carrier. An NS forward magnetic field is formed between mutually facing magnetic poles of the seal member and the magnet in the developer carrier,
Since the peripheral developer is constrained by the magnetic field and exhibits a sealing property, the slip-through of the developer is suppressed / prevented, and the leakage of the developer even under a strong impact is suppressed / prevented.

Further, according to the third aspect of the present invention, the developing device disposed in the process cartridge includes:
Since the developing device according to the first or second aspect of the present invention is used, the leakage of the developer due to the passage of the developer or the impact in the process cartridge is suppressed or prevented.

According to the fourth invention of the present application, the developing device of the first or second invention is used as the developing device in the image forming apparatus, or the third developing device is used in the image forming apparatus. Since the process cartridge of the present invention is installed, leakage of the developer due to slippage or impact of the developer in the developing device in the image forming apparatus is suppressed or prevented.

[0024]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a schematic diagram showing a main part of an image forming apparatus using a transfer type electrophotographic process of a process cartridge detachable type to which the present invention is applied.

A process cartridge 10 detachably installed in an image forming apparatus such as a laser beam printer.
Denotes a photosensitive drum 1 which is a rotating photosensitive drum type electrophotographic photosensitive member as an image bearing member on which an electrostatic latent image is formed.
Are arranged so that they can be driven to rotate clockwise, and around the photosensitive drum 1, four process devices of a charging device 2, a developing device 3, and a cleaning device 6 are collectively disposed in a predetermined position of the cartridge housing 9. It is arranged at a position.

When the process cartridge 10 is mounted in the image forming apparatus main body, the process cartridge 10 and the image forming apparatus main body are mechanically and electrically coupled to each other.
The lower surface of the photosensitive drum 1 of the process cartridge 10 comes into contact with the transfer roller 4 disposed in the image forming apparatus main body in a predetermined manner, and the image forming is enabled. Further, when the process cartridge 10 is installed in the image forming apparatus, the process cartridge insertion / removal guide / holding portion 8 of the image forming apparatus main body comes into contact with a predetermined position of the cartridge housing 9.

In the above-described process cartridge, a charging unit, a developing unit or a cleaning unit, and a photosensitive drum are integrally formed into a cartridge, and this cartridge is detachable from the main body of the image forming apparatus. However, the present invention is not limited to this, and at least one of the charging unit, the developing unit, and the cleaning unit and the photosensitive drum may be integrally formed as a cartridge so as to be detachable from the image forming apparatus main body. Further, at least the developing unit and the photosensitive drum may be integrally formed as a cartridge so as to be detachable from the image forming apparatus main body.

When the image forming apparatus forms an image using the process cartridge having the above-described structure, the photosensitive drum 1 is uniformly charged by the charging device 2 and then is moved out of the process cartridge 10 in response to the image information signal. The surface of the photosensitive drum 1 is exposed to laser light from the provided image exposing means E to perform image exposure, whereby an electrostatic latent image is formed on the photosensitive drum 1.

The electrostatic latent image formed on the photosensitive drum 1 is
The image is developed by the developing device 3. This visible image is transferred to a transfer unit, which is a transfer unit facing the photosensitive drum 1, located outside the process cartridge 10 at a position facing the photosensitive drum 1. The image is transferred onto the transfer material by the pressing pressure. The transfer material onto which the image has been transferred is conveyed to a fixing device 5 such as a heat fixing method, where the visible image on the transfer material is fixed, and is discharged out of the device as an image formed product (print, copy). ing. Further, the surface of the photosensitive drum after the transfer of the toner image to the transfer material is cleaned by the cleaning device 6 of the process cartridge 10 by removing the adhered contaminants such as residual toner on the photosensitive drum 1 and repeatedly used for image formation. It has become so.

In the above, the peripheral speed of the photosensitive drum 1 is 94
mm / sec, the outer diameter is 30 mm, the peripheral speed of the developing sleeve 31 is 111 mm / sec, and the outer diameter of the developing sleeve 31 is 1 mm.
6 m. The rotation direction of the sleeve 31 was set to the forward direction with respect to the photosensitive drum 1. Photosensitive drum 1 and developing sleeve 31
Was 0.3 mm.

The developing device 3 arranged in the process cartridge 10 will be described with reference to FIGS. 2 is a partial cross-sectional explanatory view showing a main part of a main part of the developing device, FIG. 3 is a perspective explanatory view of a developing sleeve and a magnet seal member, and FIG. 5 is a perspective explanatory view showing a magnetization pattern of the magnet seal member. FIG.

As shown in FIG. 1, a developing container 30 containing a magnetic toner, which is a magnetic developer, has an opening provided at a position facing the photosensitive drum 1 so that the toner can be carried on the surface thereof and transported. A developing sleeve 31 as an agent carrier is arranged, and a regulating blade 33 as a developer layer thickness regulating means is in contact with the surface of the developing sleeve 31. Further, magnet seal members 34 for regulating the movement of the toner on the developing sleeve 31 in the longitudinal direction of the developing sleeve 31 are disposed on the developing container 30 at both ends of the developing sleeve 31 in a non-contact manner with the developing sleeve 31. In addition, the developing device 3 is configured by providing a stirring device and the like for stirring the toner in the developing container 30. The developing sleeve 31 is
A non-magnetic cylindrical sleeve made of aluminum, stainless steel, or the like is used.

As shown in FIG. 4, the developing sleeve 31 disposed at the opening of the developing container 30 holds the developing sleeve 31 rotatably via a sleeve bearing 35 provided at a predetermined position of the developing container 30. Have been. Further, a magnet roller 32 which is a roller-shaped magnet is fixedly arranged in the developing sleeve 31. In this embodiment, the developing sleeve 31 can rotate in a counterclockwise direction.

As shown in FIG. 2, the magnet roller 32 disposed in the developing sleeve 31 has two N poles N
, N2 and a plurality of magnetic poles of two south poles S1 and S2, and the developing sleeve 31 rotates in a counterclockwise direction so that the magnetic toner supplied in the developing container 30 is magnetized. The toner is adhered to the surface by the magnetic force of the roller 32 and can be conveyed in the direction of the photosensitive drum. Further, the regulating blade 33 abutting on the surface of the developing sleeve 31 presses the surface of the developing sleeve 31 at the opening of the developing container 30 to regulate the amount of the developer on the developing sleeve 31 so that the developing sleeve 31 It regulates the thickness of the developer layer that is carried and conveyed to the development area facing the photosensitive drum.

The magnetic toner carried and conveyed by the developing sleeve 31 with the layer thickness regulated by the regulating blade 33 is
In the developing area, the electrostatic latent image formed on the photosensitive drum 1 rotating clockwise can be visualized and developed. When developing the electrostatic latent image, a vibration bias voltage in which a DC voltage is superimposed on an AC voltage is applied to the developing sleeve 31. Note that a rectangular wave, a sine wave, or the like can be used as the waveform of the vibration bias voltage.

As shown in FIG. 5, the magnet seal members 34 disposed at both ends of the developing sleeve 31 have N
It is formed by magnetizing the S pole to multiple magnetic poles. Specifically, four S poles S11, S12, S13,
S14 and three N poles N11, N12, N13 are provided, and SN poles are alternately arranged. The developing sleeve 31 includes a magnet portion 34 a formed in a substantially arc-shaped cross section along the outer circumference of both ends of the developing sleeve 31 and a locking portion 34 b for locking the magnet seal member 34 to the developing container 30. The locking portion 34b of the magnet seal member 34 can be attached to the developing container 30 while being arranged with a gap g from the outer peripheral surface of the developing device 31.

As shown in FIG. 2, the magnet roller 32 and the magnet seal member 34 are connected to the N1 pole of the magnet roller 32, S2
The magnet seal member 34 is disposed at a position facing the magnetic pole and the N2 pole, and the magnet seal member 3 faces the magnetic pole of the magnet roller 32.
The magnetic poles S11, N12, and S14 are arranged to form an N-S forward magnetic field between the magnetic pole of the magnet roller 32 and the magnetic pole of the magnet seal member 34. It is possible to suppress and prevent leakage of toner due to impact, and by arranging the magnetic poles of the magnet seal member 34 between the magnetic poles of the magnet roller 32 to restrict the magnetic toner to the magnet seal member 34. Also, the sealability is improved even between the magnetic poles.

More specifically, the magnet seal member 34 includes three magnetic poles N1, S3 of the magnet roller 32 in the developing sleeve 31.
2, S11 pole, N12 pole, S
Fourteen poles are arranged and cooperate with the magnet roller 32 to form an NS forward magnetic field. Further, the magnetic pole N of the magnet roller 32
N1 pole, S12 pole, S13 pole, and S13 pole, respectively, at positions facing between 1-S2 and between magnetic poles S2-N2.
The N13 pole is arranged, and the NS pole is magnetized into multiple magnetic poles on the inner peripheral surface of the magnet seal member 34, and the magnetic toner is also restrained at the magnetic poles N11, S12, S13, and N13 of the magnet seal member 34. And good sealing performance.

At this time, the magnetic field obtained by combining the magnetic field in the normal direction and the magnetic field in the tangential direction between the magnetic poles of the magnet seal member 34 is increased, and the magnetic toner is constrained by the action of this magnetic field. Sealability can be improved. Specifically, the value of the magnetic flux density B at the position between the magnetic poles on the surface of the developing sleeve 31 when the magnet sealing member 34 is alone (in a state where it is not arranged on the developing sleeve) is determined by the developing sleeve 31 according to the single state of the magnet sealing member. 80% or more of the value of the magnetic flux density B at the magnetic pole position on the surface of
Hereinafter, the magnet seal member 34 is formed so as to be preferably 90% or more and 110% or less.

The magnetic flux density B on the developing sleeve
Can be obtained by B = (Br ² + Bθ ² ) ^1/2 . Here, Br is the magnetic flux density [Gauss] in the normal direction on the developing sleeve, and Bθ is the magnetic flux density [Gauss] in the tangential direction on the developing sleeve.

A method for measuring the magnetic flux density will be described with reference to FIG. FIG. 6 shows the measurement of the magnetic flux density Br in the normal direction to the surface of the developing sleeve of the magnet sealing member and the magnetic flux density Bθ in the tangential direction at a position on the developing sleeve in a state where the magnet sealing member is alone (the magnet roller is not opposed). FIG. 4 is a schematic configuration diagram showing a method. A Gauss meter model 9903 manufactured by Bell Inc. was used for the measurement. FIG. 6A is an explanatory plan view showing a state in which a Gauss meter is installed.
(B) is an explanatory side view.

As shown in FIG. 6, the magnet seal member 34
However, it is fixed on the rotary table 40 such that its inner peripheral surface is substantially concentric with the rotation center of the rotary table 40. Further, the biaxial probe 42 is disposed at a position facing the inner peripheral surface of the magnet seal member 34, and the measurement surface of the biaxial probe 42 and the inner peripheral surface of the magnet seal member 34 They are opposed to each other with a distance corresponding to the distance g from the sleeve 31. The two-axis probe 42
The rotary table 40 is connected to a Gauss meter 41.
By measuring the magnetic flux density of the magnet seal member 34 while rotating, the magnetic flux density in the normal direction and the tangential direction at the position on the developing sleeve by the magnet seal member can be measured.

The magnet seal member 34 is made of Nd-Fe
A 4 mm wide injection-molded article provided with a nylon binder containing -B magnetic powder, and the gap g between the magnet seal member 34 and the developing sleeve 31 was 0.1 to 0.7 mm.
The peak value of the magnetic flux density on the sleeve surface of each magnetic pole of the magnet seal member 34 in the direction normal to the sleeve surface is 1
2,000 to 2,200 × 10 ⁻⁴ T (tesla). Also,
The peak value of the magnetic flux density in the direction normal to the sleeve surface of each magnetic pole of the magnet roller 32 fixed in the developing sleeve 31 was 400 to 900 × 10 ⁻⁴ T (tesla).

The position of the magnetic roller of the present embodiment opposite to the magnetic pole and the magnetic seal member provided with the magnetic pole between the magnetic poles, as shown in FIG. The graph showing the distribution form of the magnetic flux density and the magnet seal member having the magnetic pole only at the position facing the magnetic pole of the conventional magnet roller shown in FIG. The present embodiment and the conventional example will be compared and described with reference to a graph showing the distribution of the magnetic pole position and the magnetic flux density. The horizontal axis of the graph indicates the position in the circumferential direction of the developing sleeve 31 by an angle, and the vertical axis indicates the magnitudes of the magnetic flux densities B, Br, and Bθ on the sleeve.

According to FIG. 8, in the conventional magnet seal member, the magnetic flux density B between the magnetic poles is
It is clear that the sealability of this part cannot be expected. In comparison, FIG. 7 shows that in the magnet seal member of the present embodiment, the magnetic flux density B between the magnetic poles and the magnetic flux density B at the magnetic pole portions are almost the same. From this, it can be seen that by increasing the magnetic flux density B between the magnetic poles as in the present embodiment, it is possible to improve the sealing performance even between the magnetic poles.

As described above, according to the developing device of the present embodiment, it is possible to suppress and prevent the developer from passing in the longitudinal direction of the developing sleeve while being a compact developing device. It is possible to suppress and prevent the developer from being scattered toward the end portion. By using this developing device for the process cartridge, it is possible to prevent a shock applied to the process cartridge when a user attaches or detaches the process cartridge from the image forming apparatus main body. As a result, good sealing properties without leakage of the developer can be obtained.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the magnet roller in the developing sleeve is rotatably arranged.

FIG. 9 is a partially sectional explanatory view showing a main part of a main part of a developing device in which a magnet roller is configured to be rotatable. The present embodiment has the same configuration as the first embodiment except that the configuration of the magnet roller inside the developing sleeve is different.

As shown in FIG. 9, the magnet roller 32 'arranged in the developing sleeve 31 has four N poles N
1, N2, N3, N4 and four south poles S1, S
2, S3, and S4, and is disposed so as to be rotatable clockwise in the direction of arrow a in FIG. 9, and is rotated counterclockwise in the direction of arrow b in FIG.
The magnetic toner on the first roller 1 can be transported in the direction of arrow b while being attached to the surface by the magnetic force of the magnet roller 32. Further, the magnet seal member 34 is attached to the developing sleeve 3.
At both end portions of the device 1, there are arranged three S poles S 11, S 12, S 13 and three N poles N 11, N 12, N 13 on the inner circumferential surface.

In the developing device of the present embodiment, even if the magnet roller 32 'rotates as described above, the magnetic flux density B of the magnet seal member 34 alone at the position between the magnetic poles on the surface of the developing sleeve 31 is reduced. The magnet seal member 34 is formed so that the value thereof is 80% or more and 120% or less of the value of the magnetic flux density B at the magnetic pole position on the surface of the developer carrier when the magnet seal member is in a single state. The magnetic field obtained by combining the magnetic field in the normal direction and the magnetic field in the tangential direction between the magnetic poles is increased, and the magnetic toner is constrained by the action of the magnetic field so that the sealing property between the magnetic poles is improved. Therefore, even though the developing device is a compact developing device, it is possible to suppress or prevent the developer from passing through in the longitudinal direction of the developing sleeve to some extent. Good sealing performance without leakage of the developer can be obtained even when a considerably strong impact or the like is applied to the image forming apparatus when it is attached to or detached from the image forming apparatus main body.

In the above embodiments, the case where the magnetic toner is used as the magnetic developer has been described as an example. However, the same applies to the case where a two-component magnetic developer composed of a non-magnetic toner and magnetic particles (carrier) is used as the developer. The effect of is obtained. Further, the developing device of each of the above-described embodiments is provided in the process cartridge. However, the present invention is not limited to this, and the developing devices having the above-described configurations may be arranged in the image forming apparatus.

[0054]

As described above, according to the first invention of the present application, a magnet seal member formed by magnetizing NS poles with multiple magnetic poles on its inner peripheral surface is provided. The value of the magnetic flux density at the position between the magnetic poles on the surface of the developer carrying member is 80% or more of the value of the magnetic flux density at the position of the magnetic pole on the surface of the developer carrying member by the magnet sealing member, and 1
Since it is 20% or less, the magnetic field obtained by combining the magnetic field in the normal direction and the magnetic field in the tangential direction between the magnetic poles of the magnet seal member is increased, and the magnetic toner is constrained by the action of this magnetic field. Good sealing properties between the magnetic poles can be maintained, and with a compact structure, leakage of the developer due to slip-through or impact of the developer can be suppressed or prevented. Further, even when the magnet in the developer carrying member is configured to be rotatable, it is possible to obtain a developing device capable of suppressing and preventing leakage of the developer due to slipping of the developer or impact.

According to the second aspect of the present invention, magnetic poles having different polarities are provided at positions facing each other between the magnet seal member and the magnet fixedly arranged in the developer carrier. An N-S forward magnetic field is formed between mutually facing magnetic poles of the magnet sealing member and the magnet in the developer carrying member, and the peripheral developer is constrained by the magnetic field to exhibit sealing properties; It is possible to obtain a developing device capable of suppressing and preventing the developer from passing through the magnetic poleless portion on the developer carrying member, and also suppressing and preventing the leakage of the developer against a strong impact.

According to the third aspect of the present invention, the developing device arranged in the process cartridge is
Since the developing device according to the first or second aspect of the present invention is used, it is possible to obtain a process cartridge in which the leakage of the developer due to the slip-through or impact of the developer is suppressed or prevented. Good sealing properties can be obtained in which the developer does not leak even when an impact or the like is applied to the apparatus main body when it is attached or detached.

According to the fourth invention of the present application, the developing device of the first or second invention is used as the developing device in the image forming apparatus, or the third developing device is used in the image forming apparatus. Since the process cartridge of the invention is installed, it is possible to obtain an image forming apparatus capable of performing easy maintenance and good image formation by suppressing and preventing the leakage of the developer due to the slip-through or impact of the developer. it can.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a main part of an image forming apparatus using a transfer type electrophotographic process of a process cartridge attachment / detachment type according to a first embodiment.

FIG. 2 is a partial cross-sectional explanatory view showing a main part of the developing device.

FIG. 3 is a perspective explanatory view showing a developing sleeve and a magnet sealing member.

FIG. 4 is a partial cross-sectional explanatory view in a longitudinal direction of a main part of the developing device.

FIG. 5 is an explanatory perspective view showing a magnetization pattern of a magnet seal member.

FIG. 6 is a schematic configuration diagram showing a method of measuring a magnetic flux density of a magnet seal member.

FIG. 7 is a graph showing a distribution form of a magnetic pole position and a magnetic flux density at a surface position of a developing sleeve using only the magnet seal member of the embodiment.

FIG. 8 is a graph showing a distribution form of a magnetic pole position and a magnetic flux density at a surface position of a developing sleeve by a conventional magnet seal member alone.

FIG. 9 is a partial cross-sectional explanatory view showing a main part of a main part of a developing device in which a magnet roller according to a second embodiment is configured to be rotatable;

FIG. 10 is an explanatory front view showing a conventional developing device.

FIG. 11 is an explanatory side view in a longitudinal direction of a main part of a conventional developing device.

FIG. 12 is an explanatory front view showing a developing device using a conventional magnet seal member.

[Explanation of symbols]

 Reference Signs List 1 photosensitive drum (image carrier) 3 developing device 10 process cartridge 30 developing container 31 developing sleeve (developer carrier) 32 magnet roller (magnet in developer carrier) 34 magnet seal member

Claims (4)

[Claims] 1. A developing container which stores a magnetic developer and a magnet rotatably supported by the developing container and having a plurality of magnetic poles inside the developing container so that the developer can be carried and transported in a predetermined direction. In a developing device having a developer carrier and a magnet seal member disposed at a predetermined interval at a position opposite to the developer carrier on the developing container side at both ends of the developer carrier, the magnet seal member includes: NS on the circumference
The magnetic flux density at the position between the magnetic poles on the surface of the developer carrier by the magnet seal member is determined by magnetizing the poles to the multiple magnetic poles. Is 80% or more and 120% or less of the developing device. 2. A magnet inside a developer carrier is fixedly arranged in the developer carrier, and magnetic poles of different polarities are provided at least at positions where the magnet seal member and the magnet inside the developer carrier oppose each other. The developing device according to claim 1. 3. The developing device according to claim 1, wherein the developing device is formed detachably with respect to the image forming apparatus main body and has at least an image carrier and a developing device. A process cartridge, characterized in that: 4. A developer container containing at least a magnetic developer and a magnet rotatably supported by the developer container and having a plurality of magnetic poles inside the developer container to carry and transport the developer in a predetermined direction. An image forming apparatus provided with a developing device having a developer carrier capable of being provided and magnet seal members arranged at predetermined intervals at positions opposite to the developer carrier on the image container side at both ends of the developer carrier. Wherein the developing device according to claim 1 or 2 is used as a developing device, or the process cartridge according to claim 3 is arranged in an image forming apparatus. apparatus.