JP2001350318A - Magnetic brush electrifying device, process cartridge and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent magnetic carrier from being leaked from the end of an electrifying sleeve provided at the aperture part of a carrier container. SOLUTION: The rotatable electrifying sleeve 2b including a fixed magnet 2a is provided at the aperture part 2Ba of the carrier container in which the magnetic carrier is stored. An end sealing member (end magnetic plate) 41 constituted of rare earth resin magnet is provided at the end of the sleeve 2b through a gap (g). Since the magnetic carrier at the magnetized end of the fixed magnet 2a is restricted by the magnetic force of the fixed magnet 2a and that of the member 41, the leakage of the magnetic carrier is surely prevented even in the case of strong vibration or even if the magnetic force of the member 41 is not made strong particularly. Then, the member 41 is in non-contact with an insulating member at the end of the sleeve 2b, so that insulating property is maintained over a long term without damaging the insulating member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic brush charging device and a process cartridge used in an electrophotographic copying machine, a printer, a facsimile, and the like, and an image forming apparatus provided with the same.

[0002]

2. Description of the Related Art In recent years, a member to be charged (for example, a photosensitive drum) has been used.
As a charging device for uniformly charging the surface, a contact charging device has been put to practical use. This contact charging device uniformly charges the surface of a member to be charged by bringing a charging member into contact with the member to be charged and applying a charging voltage to the charging member. This contact charging device has an advantage that it is possible to reduce ozone and power consumption as compared with a conventionally known non-contact charging device such as a corona charger.

[0003] Among such contact charging devices, a magnetic brush charging device is preferably used in view of stability of charging contact.

The magnetic brush charging device forms a magnetic brush (contact charging member) by magnetically restraining conductive magnetic particles directly on the surface of a magnet or on the surface of a sleeve containing a fixed magnet. The magnetic particles are brought into contact with the member to be charged while being stopped or rotated, and a charging bias is applied to the magnetic brush to uniformly charge the surface of the member to be charged to a predetermined polarity and potential.

When the above-described magnetic brush charging device is used, and a photoreceptor having a surface layer in which conductive fine particles are dispersed on a normal organic photoreceptor, or an amorphous silicon photoreceptor is used as a member to be charged. Since the charge can be directly injected into the surface of the charged object via the magnetic particles of the magnetic brush, the charged potential is substantially equal to the DC component of the charging bias applied to the magnetic brush. It can be obtained on the surface of the charged body. According to such a charging method, that is, injection charging, unlike a non-contact charging device such as a corona charger, a discharge phenomenon is not used when charging an object to be charged, so ozone-less and low power consumption type charging is possible. It is.

FIG. 6 is a longitudinal sectional view showing a schematic configuration of the magnetic brush charging device 2.

The magnetic brush charging device 2 shown in FIG. 1 includes a fixed magnet 22 serving as a magnetic field generating means, and a carrier container formed by a charging sleeve 21 which is a rotatable cylindrical magnetic carrier carrier made of a nonmagnetic material. The magnetic carrier (magnetic particles) accommodated in the magnetic carrier 24 is carried, and the thickness of the carried magnetic carrier is regulated by a charging blade 53 so that a magnetic carrier thin layer of a predetermined thickness (hereinafter referred to as “magnetic brush 23” as appropriate). )) And transported to the charging section,
The surface of the photosensitive drum 1 is charged.

At the time of charging, a charging bias in which an AC voltage is superimposed on a DC voltage is applied between the charging sleeve 21 and the photosensitive drum 1, and the surface (outer peripheral surface) of the photosensitive drum 1 has a DC voltage value due to charge injection charging. They are almost equally charged.

Here, as shown in FIG. 6, the fixed magnet 22 has a plurality of magnetic poles in the circumferential direction such as magnetic poles N1, S1, N2 and S2. As the action of these magnetic poles, the magnetic pole S2 attracts the magnetic carrier in the carrier container 24 and carries it on the charging sleeve 21, and the magnetic pole Nl carries the magnetic carrier. The magnetic pole S1 is disposed opposite to the photosensitive drum 1 to inject electric charge onto the photosensitive drum 1 to be charged, and the magnetic pole N2 prevents the magnetic carrier from leaking from below the carrier container 24.

Generally, the fixed magnet 22 has a cylindrical shape, and each pole is magnetized to the longitudinal end.

An end seal member 27 made of felt, malt plain, or the like is provided at both ends in the longitudinal direction of the opening 24 a formed in the carrier container 24.
To prevent the magnetic particles from leaking from the end of the opening 24a.

The above-described magnetic brush charging device 2 includes an end portion of the charging sleeve 21 in the longitudinal direction (the generatrix direction of the photosensitive drum 1),
That is, at the end of the magnetized area of the fixed magnet 22 included in the charging sleeve 21, the magnetic force decreases, the magnetic brush 23 becomes coarse, and the contact with the photosensitive drum 1 becomes unstable. There is a problem that it is difficult to uniformly charge even the region, and as a second problem, a potential difference is generated between the surface of the photosensitive drum 1 and the tip of the magnetic brush 23, and the magnetic carrier moves from the charging sleeve 21 to the photosensitive drum 1. There is a problem that it adheres to the surface. Due to the second problem, there is a problem that the magnetic carrier as a charging agent is reduced and the charging performance is deteriorated even in long-term durability. Also, due to the second problem, the photosensitive drum 1
There is a problem that the magnetic carrier adhering to the developing device is mixed into the developing device to lower the developing performance, or spills to contaminate the inside of the image forming apparatus main body.

Therefore, conventionally, an insulating member 2 for electrically insulating the charging sleeve 21 from the magnetic carrier at the end is provided.
8, the above-mentioned problem is prevented by cutting off the conductive path between the surface of the photosensitive drum 1 and the charging sleeve 21.
As the insulating member 28, an insulating tape such as a Mylar tape or a Teflon (registered trademark) tape has been used.

FIG. 7 is a potential diagram for explaining the surface potential on the photosensitive drum after charging. In FIG. 7, a indicates a DC bias applied to the magnetic brush charging device 2. When the insulating member 28 is not provided, the magnetic carrier at the end is located at the boundary between the charged area and the uncharged area, as shown by b in FIG. 7, and the magnetic brush 23 contacts the photosensitive drum 1 at the end. It is unstable, and an insufficiently charged area occurs in a fine area where the magnetic carrier is not in contact, and receives a force moving (adhering) to the photosensitive drum side. In addition, the gap of the charging potential is large between the inside and outside of the boundary of the charging region, and a magnetic carrier adhesion electric field is generated outward on the photosensitive drum.

Therefore, the coating area is extended in the longitudinal direction,
By applying an insulating region by applying a mylar tape (insulating member 28) to the extended portion, the potential drop at the end becomes a slope as shown in c in FIG. The potential also decreases, and the magnetic carrier adhesion electric field decreases.

In the magnetic brush charging device 2 as described above, the length of the opening 24a of the carrier container 24, the length of the charging sleeve 21, the length of the fixed magnet 22, the end sealing member 2
7. The longitudinal positions of the magnetic brush coat region and the insulating region at the end are set as follows. FIG. 8 is an explanatory cross-sectional view of the charging sleeve 21 in the longitudinal direction. That is, the image charging area (charge-guaranteed area B) is set according to the transport area of the recording material to be used (recording medium transport area A). An insulating member 28 is provided at least from the end side of the charge assurance area B to set an insulating area F, and the opening 24 of the carrier container 24 is set so that the insulating area F is at least 2 mm or more.
The opening width of a is set. Thereby, the charging sleeve 21
The upper portion is coated with a magnetic carrier corresponding to the width of the opening, so that the original charged potential is obtained inside the insulating region F, and the potential slope can be formed on the insulating region F as described above. Further, the length D of the fixed magnet 22 is set over the entire opening width, and the end seal members 27 are provided outside the both ends in the longitudinal direction of the fixed magnet 22. This is because the magnetic carrier of the fixed magnet 22 does not draw the magnetic carrier to the end seal member 27.

Further, recently, there is an end seal member 27 using a magnetic seal member formed of a magnetic material such as an iron plate. This is because a magnetic seal member is attached to the end of the opening 24a of the carrier container 24 at a small distance from the charging sleeve 21, and the magnetic carrier is attracted by the magnetic force of the magnetic seal member to prevent leakage of the magnetic carrier. Things.

The above-described magnetic seal member includes a charging sleeve 2
1 is an end seal member such as felt because it is not in contact with
7, the rotation torque of the charging sleeve 21 is smaller, and the motor for rotating the charging sleeve 21 can be reduced in size.

Further, the end seal member 27 such as a felt cannot be reused because the endurance is deteriorated due to the sliding contact with the charging sleeve 21, whereas the magnetic seal member has no endurance deterioration. There is an advantage that it can be reused when recycling.

Here, the cleanerless process (toner recycling process) will be described.

In recent years, the size of an image forming apparatus has been reduced. However, the overall size of the image forming apparatus can be reduced only by reducing the size of each process device for charging, exposing, developing, transferring, fixing, and cleaning. Conversion was limited. Also,
The transfer residual toner on the photosensitive drum after the transfer of the toner image is collected by a cleaning unit (cleaner) to become waste toner, but it is preferable that the waste toner does not come out from the viewpoint of environmental protection.

Therefore, the cleaner is removed, and the transfer residual toner on the photosensitive drum is removed from the photosensitive drum by "developing simultaneous cleaning" by the developing means, and is collected by the developing means.
An image forming apparatus of a so-called “cleanerless process” having an apparatus configuration for reuse has also appeared. Simultaneous development and cleaning refers to a fogging bias (a fogging potential difference Vback, which is a potential difference between a DC voltage applied to a developing unit and a photosensitive drum surface potential) in a developing area, where transfer residual toner slightly remaining on a photosensitive drum after transfer is transferred. ). According to this method, since the transfer residual toner is collected by the developing means and reused thereafter, waste toner can be eliminated and maintenance can be simplified. In addition, the cleaner-less has a great advantage in terms of space, and the size of the image forming apparatus can be significantly reduced. Further, in the case where the charging device of the photosensitive drum is a contact charging device, the transfer member can be once recovered by the charging member in contact with the photosensitive drum, discharged again onto the photosensitive drum, and recovered by the developing device. .

[0023]

However, the conventional end seal member 27 and its arrangement have the following disadvantages.

In the end sealing member 27 of a contact system such as felt or malt plain, the above-mentioned insulating member 28 at the end is used.
And was placed in contact with a Mylar tape or Teflon tape, and proper sealing was applied to maintain the sealing properties at the end. Therefore, during the rotation operation of the charging sleeve 21 associated with long-term image formation, the insulating member 28 continues to be worn by the contact member of the end seal member 27, and eventually the mylar tape or the like is cut or peeled off. This results in damage such as wear.
Alternatively, the end seal member 27 itself may be peeled off or abraded and the sealing property may not be maintained. In particular, when the magnetic carrier invades between the end sealing member 27 and the insulating member 28 even a little, the deterioration is further accelerated.

When the insulating member 28 is damaged, the magnetic carrier adheres to the photosensitive drum 1 without maintaining the insulating property at the end portion, and is mixed into the developing device, and the stable developing performance cannot be maintained. Problems such as magnetic carriers spilling into the main body and contaminating occur. Also, fragments of the insulating member 28 may enter the carrier container 24 and the developing container, thereby deteriorating basic performance. Even when the end sealing member 27 is broken, the sealing performance of the end is not maintained, and the magnetic carrier spills into the main body of the image forming apparatus, causing contamination and the like. Also, fragments of the end seal member 27 may enter the carrier container 24 or the developing container, thereby deteriorating basic performance.

In the magnetic brush charging device 2,
In order to secure a long-term stable charging property, a region (charging nip portion) where the magnetic brush 23 and the photosensitive drum 1 are in contact with each other needs to be widened.
The weight per unit area of the magnetic carrier on the charging sleeve 21 needs to be very large with respect to the gap between the magnetic carrier and the photosensitive drum 1. For this reason, the magnetic carrier at the end of the charging sleeve is crushed by the charging sleeve 21 and the photosensitive drum 1 when passing through the gap between the charging sleeve 21 and the photosensitive drum 1, and the magnetic carrier tends to spread outward without being coated. If the magnetic carrier enters an area where there is no regulation, the magnetic carrier cannot be held on the charging sleeve 21 and causes leakage of the magnetic carrier regardless of the magnetic carrier adhesion electric field. In particular, when a user moves the entire image forming apparatus and uses it, such as a portable copying machine and a portable printer, intense vibration may be applied during the movement of the image forming apparatus. In the case of a process cartridge in which the photosensitive drum 1 and the magnetic brush charging device 2 are formed into a cartridge, an impact such as a vertical swing may be applied to the process cartridge when the process cartridge is attached to or detached from the image forming apparatus main body.

In order to ensure the sealing performance of the magnetic seal member against such severe vibrations and shocks, the conventional magnetic plate alone is not sufficient, and the magnetic force of the magnetic seal member or It is necessary to enhance the sealing performance.

In particular, in a system using a cleanerless system as described above, once a magnetic carrier leaks onto the photosensitive drum 1, there is no cleaning device capable of reliably collecting the leaked magnetic carrier. Therefore, there is a high possibility that the magnetic carrier is mixed into the developing device to lower the stable function of the developer or spills into the image forming apparatus main body to contaminate the transfer device and the like.

The present invention has been made in view of the above circumstances, and prevents the charging agent (magnetic carrier) in a magnetic brush charging device from leaking onto an image carrier even when vibration or impact is applied. It is an object of the present invention to provide a magnetic brush charging device, a process cartridge, and an image forming apparatus capable of ensuring sufficient sealing performance and long-term insulating performance of an insulating member.

[0030]

According to a first aspect of the present invention, there is provided an image forming apparatus comprising: a conductive magnetic particle to which a voltage is applied; In a magnetic brush charging device for charging a surface of an image carrier, a charging agent container having a storage portion for storing the magnetic particles and an opening facing the surface of the image carrier, and rotatably disposed in the opening At the end of the opening along the axial direction of the charging agent carrier, and a magnetic field generating means that is included in the charging agent carrier and has a plurality of magnetic poles in the circumferential direction. And an end seal member made of a rare earth resin magnet facing the outer peripheral surface of the charging agent carrier with a gap therebetween.

According to a second aspect of the present invention, in the magnetic brush charging device according to the first aspect, the end sealing member is formed of a Nd-Fe-B-based bonded magnet. .

According to a third aspect of the present invention, there is provided the first or second aspect.
Wherein the magnetic field generating means has two magnetic poles adjacent to each other with the same polarity among the plurality of magnetic poles.

According to a fourth aspect of the present invention, at least an image carrier and a charging means for charging the image carrier are integrally incorporated in a cartridge container, and are detachably attached to an image forming apparatus main body. 4. The process cartridge according to claim 1, wherein said charging unit is provided with said charging unit.
The magnetic brush charging device according to (1), wherein:

According to a fifth aspect of the present invention, there is provided an image bearing member, charging means for charging the image bearing member, and exposing means for exposing the charged surface of the image bearing member to form an electrostatic latent image. An image forming apparatus comprising: a developing unit that attaches toner to the electrostatic latent image to develop the toner image as a toner image; and a transfer unit that transfers the toner image to another member. A magnetic brush charging device according to 1, 2, or 3.

According to a sixth aspect of the present invention, there is provided an image bearing member, charging means for charging the image bearing member, and exposing means for exposing the charged image bearing member surface to form an electrostatic latent image. An image forming apparatus including: a developing unit that attaches toner to the electrostatic latent image to develop the toner image as a toner image; and a transfer unit that transfers the toner image to another member. A process cartridge detachably mounted to the forming apparatus main body, wherein the process cartridge is the process cartridge according to claim 6.

The present invention according to claim 7 is directed to claim 5 or 6.
Wherein the image carrier has a charge injection layer on a surface thereof.

The present invention according to claim 8 is based on claims 5, 6,
Or the image forming apparatus according to 7, wherein the developing unit also serves as a cleaning unit that collects transfer residual toner remaining on the surface of the image carrier after transferring the toner image on the image carrier to the other member. It is characterized by the following.

[0038]

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

Embodiment 1 FIG. 1 shows an example of an image forming apparatus according to the present invention. The image forming apparatus shown in FIG.
This is an electrophotographic laser beam printer.
It is a figure which shows the longitudinal section typically.

The image forming apparatus shown in FIG. 1 includes a drum type electrophotographic photosensitive member (hereinafter, referred to as "photosensitive drum") 1 as an image carrier. In this embodiment, the photosensitive drum 1 is an OPC photosensitive member (organic photosensitive member) having a diameter of 30 mm, and a process speed (peripheral speed) of 100 mm / sec in a direction of an arrow R1 (clockwise) by a driving unit (not shown). ) Is driven to rotate.

Around the photosensitive drum 1, the magnetic brush charger (charging means) 2, the exposure device (exposure means) 3, the developing device (developing means) 4, the transfer roller (transfer) Means) 5, a cleaning device (cleaning means) 6, and the like. Further, the transfer roller 5 is arranged along the conveying direction of the recording material P such as paper (the direction of arrow Kp).
A fixing device (transfer means 9) is disposed downstream of the fixing device.

The above-described magnetic brush charging device 2 has a magnetic brush 2c as a contact charging member. The magnetic brush charging device 2 includes a non-magnetic rotatable charging sleeve (charging sleeve) 2a, a magnet (fixed magnet) 2b fixedly disposed inside the charging sleeve 2a, and an adhesion to the surface of the charging sleeve 2a by the magnetic force of the magnet 2b. (Supported) conductive magnetic carriers (magnetic particles). This magnetic carrier constitutes the magnetic brush 2c. In the magnetic brush charging device 2, a charging bias in which a rectangular alternating voltage of 1000 Hz and 800 V are superimposed on a DC voltage of -700 V is applied from the charging bias applying power source S1 to the magnetic brush 2c. As a result, the surface (outer peripheral surface) of the photosensitive drum 1 is uniformly charged to approximately -700V.

The photosensitive drum 1 has a surface (charged surface) corresponding to a time-series electric digital pixel signal of target image information output from a laser beam scanner (exposure device 3) having a laser diode, a polygon mirror and the like. Scanning exposure L is performed by the intensity-modulated laser beam, and an electrostatic latent image corresponding to target image information is formed on the surface of the photosensitive drum 1. This electrostatic latent image is reversely developed as a toner image by the developing device 4 using magnetic one-component insulating toner (negative toner). Reference numeral 4a denotes a non-magnetic phenomenon developing sleeve having a diameter of 16 mm including the magnet 4b.
With the sleeve 4a coated with negative toner and the distance from the surface of the photosensitive drum 1 fixed at 300 μm, the sleeve 4a is rotated at the same speed as the photosensitive drum 1, and a developing bias voltage is applied to the developing sleeve 4a from a developing bias applying power source S2. I do. This voltage is a DC voltage of -500V and a frequency 18
The developing sleeve 4a and the photosensitive drum 1 are superimposed with a rectangular AC voltage of 00 Hz and a peak-to-peak voltage of 1600 V.
Cause a jumping phenomenon to occur.

On the other hand, a recording material P as a recording medium is supplied from a paper supply unit (not shown), and the photosensitive drum 1 is brought into contact with the photosensitive drum 1 with a predetermined pressing force, and is a medium transfer medium having a medium resistance. It is introduced at a predetermined timing into a pressure nip (transfer portion) T between the transfer roller 5 and the transfer roller 5. A predetermined transfer bias voltage is applied to the transfer roller 5 from a transfer bias application power source S3.

In this embodiment, the transfer roller 5 has a resistance value of 5 × 10 ⁸ Ω, and the transfer is performed by applying a DC voltage of + 2000V.

The recording material P introduced into the transfer section T is conveyed by nipping the transfer section T, and the photosensitive drum 1
The toner image formed and carried on the surface is sequentially transferred by electrostatic force and pressing force.

The recording material P to which the toner image has been transferred is separated from the surface of the photosensitive drum 1 and introduced into a fixing device 7 such as a heat fixing method, where the toner image is fixed, and is formed as an image formed product (print, copy). It is discharged outside the image forming apparatus main body.

Further, the surface of the photosensitive drum 1 after the transfer of the toner image to the recording material P is cleaned by removing contaminants such as untransferred toner by the cleaning device 6, and the subsequent image formation (image formation) is repeated. To be served.

In the image forming apparatus of the present embodiment, the four process devices of the photosensitive drum 1, the magnetic brush charging device 2, the developing device 4, and the cleaning device 6 are integrated into the cartridge container 30a to form the process cartridge 30.
The process cartridge 30 is configured to be detachable and replaceable with respect to the image forming apparatus main body. The image forming apparatus according to the present invention is not limited to the process cartridge type.

As the photosensitive drum 1 used in the present invention,
Can use a commonly used organic photoreceptor, etc.
Preferably, the resistance on the organic photoreceptor is 10⁹
-10 ¹⁴With a surface layer having a material of Ωcm,
When using amorphous silicon photoreceptor, charge injection
Charging can be achieved, preventing ozone generation and low power consumption
It is effective for reduction. It is also necessary to improve the chargeability.
It becomes possible.

Therefore, in the present embodiment, as shown in FIG. 2 (a partially enlarged vertical cross-sectional view of the photosensitive drum), the following first to first organic photosensitive members are formed on a 30 mm-diameter aluminum drum base. The photosensitive drum 1 provided with the fifth five layers in order from the bottom was used.

The first layer is a subbing layer 1b, which is a conductive layer having a thickness of 20 μm and provided for smoothing defects or the like of an aluminum substrate (hereinafter referred to as “aluminum substrate”) 1a.

The second layer is a positive charge injection preventing layer 1c, which serves to prevent positive charges injected from the aluminum substrate 1a from canceling out negative charges charged on the surface of the photosensitive drum, and comprises an amylan resin and methoxymethyl resin. This is a medium resistance layer having a thickness of 1 μm and a resistance adjusted to about 1 × 10 ⁶ Ω · cm by nylon nylon.

The third layer is a charge generation layer 1d, which is a layer having a thickness of about 0.3 μm in which a disazo pigment is dispersed in a resin, and generates positive and negative charge pairs upon exposure.

The fourth layer is a charge transporting layer 1e in which hydrazone is dispersed in a polycarbonate resin.
Type semiconductor. Therefore, negative charges charged on the surface of the photosensitive drum cannot move through this layer, and only positive charges generated in the charge generation layer 1d can be transported to the surface of the photosensitive drum.

The fifth layer is a charge injection layer 1f, which is a coating layer of a material in which ultrafine SnO ₂ particles are dispersed in a binder of an insulating resin. Specifically, SnO ₂ particles having a particle diameter of about 0.03 μm obtained by doping antimony, which is a light-transmitting insulating filler, to an insulating resin to reduce the resistance (conducting conductivity) are dispersed by 70% by weight in the resin. It is a coating layer of the material. The coating solution thus prepared was applied to a thickness of about 4 μm by a dipping coating method to obtain a charge injection layer 1f. At this time, a 5 mm uncoated area of the photosensitive layer was present at the far end of the photosensitive member.

Next, the magnetic brush charging device 2 used in the present embodiment will be described in detail with reference to FIG. The magnetic brush charging device 2 is mainly composed of a magnetic brush charger 2.
A and a carrier container (charging agent container) 2B. The magnetic brush charger 2A is provided with a magnetic carrier (magnetic particles) 2d on a rotatable non-magnetic charging sleeve (charging agent carrier) 2b having an outer diameter of 16 mm and having a fixed magnet (magnetic field generating means) 2a provided therein. Are formed on a brush-like magnetic brush (charging member) 2c by a magnetic field, and the magnetic carrier 2d is conveyed in the same direction as the charging sleeve 2b rotates in the direction of the arrow R2. In the present embodiment, the fixed magnet 2a inside the charging sleeve 2b has a plurality of magnetic poles S1, N1, S2, S3, N2 in the circumferential direction,
The S poles (magnetic poles S2) are arranged on the opposite side of the opening 2Ba of the carrier container 2B where the charging sleeve 2b faces the photosensitive drum 1.
And the magnetic pole S3) have five poles including two poles arranged side by side.
Further, the charging sleeve 2b rotates in the counter direction (the direction of the arrow R2) with respect to the photosensitive drum 1, and in the present embodiment, the rotation speed of the photosensitive drum 1 is 100 mm.
/ Sec, the magnetic brush 2c is 150 mm / sec.
Spinning at. Then, by applying a charging voltage to the charging sleeve 2b by a charging bias applying power source E2, charges are directly given from the magnetic carrier 2d to the charge injection layer 1f on the surface of the photosensitive drum 1, and the surface of the photosensitive drum 1 is
It is charged to a potential corresponding to the charging voltage. Note that the higher the rotation speed of the magnetic brush 2c, the better the charging uniformity tends to be.

Magnetic carrier 2d used as a charging agent
The average particle diameter is 10 to 100 μm and the saturation magnetization is 2
0 to 250 emu / cm ³ , resistance 1 × 10 ² to 1 × 1
0 ¹⁰ Ω · cm is preferable.
In view of the existence of insulation defects such as pinholes, it is preferable to use those having a density of 1 × 10 ⁶ Ω · cm or more. In order to improve the charging performance, it is better to use a material having as small a resistance as possible. Therefore, in this embodiment, the average particle diameter is 25 μm, and the saturation magnetization is 200 emu / c.
A magnetic carrier 2d having m ³ and a resistance of 5 × 10 ⁶ Ω · cm was used.

Here, the resistance value of the magnetic carrier 2d is determined by adding 2 g of the carrier to a metal cell having a bottom area of 228 (mm ² ), applying a load of 6.6 kg / cm ² , and applying a voltage of 100 V. Measuring.

As the magnetic carrier 2d, a resin carrier formed by dispersing magnetite as a magnetic material in a resin and dispersing carbon black for conductivity and resistance adjustment, or a magnetite single surface such as ferrite is oxidized. A material which has been subjected to a reduction treatment to adjust the resistance, or a material which has been coated with a magnetite simple substance resin such as ferrite and the resistance has been adjusted is used.

The width of the contact portion between the magnetic brush 2c and the photosensitive drum 1, that is, the charging nip width N is approximately 6 mm.
It was adjusted to be.

The carrier container 2B has a storage section 2Bb for storing the magnetic carrier 2d and an opening 2Ba provided at a position facing the surface of the photosensitive drum 1. The opening 2Ba is formed long along the generatrix direction of the surface of the photosensitive drum 1 (the axial direction of the developing sleeve 2b). A developing sleeve 2b including the above-described fixed magnet 2a is provided in the opening 2Ba.

The fixed magnet 2 is provided in the carrier container 2B.
A regulating blade (magnetic carrier regulating blade) 2e for regulating the layer thickness of the magnetic carrier 2d carried on the surface of the developing sleeve 2b by the magnetic force a is attached. The regulating blade 2e is disposed in the axial direction of the developing sleeve 2b, and regulates the thickness of the magnetic brush 2c by a gap formed between the tip and the surface of the photosensitive drum 1.

The charging bias applying power source E2 applies a voltage between the regulating blade 2e and the developing sleeve 2b.
A charging bias in which an AC voltage is superimposed on a DC voltage is applied. In the present embodiment, good charging properties can be obtained by applying a charging bias in which a rectangular alternating voltage of 1000 Hz and 800 V are superimposed on a DC voltage of -700 V.

Next, the end processing of the magnetic brush charging device 2 used in this embodiment will be described. FIG. 4 shows the charging sleeve 2b and the photosensitive drum 1 according to the present embodiment.
In the longitudinal direction (the direction along the generatrix of the photosensitive drum 1, or
FIG. 3 is a schematic configuration diagram illustrating an arrangement of a charging sleeve 2b (in an axial direction). The recording medium transport area A, which is the width of the recording material P when passing from the center, is one length.
In contrast, the charge assurance area B is 159.4 m wider than that.
m. And, outside the charging guarantee area B (end side)
Is provided with an insulating member 43 on the outer peripheral surface of the charging sleeve 2b to form an insulating region F. On the other hand, the length of the magnetic carrier regulating blade 2e, that is, the coating region C of the magnetic carrier 2d is 165 mm, and the insulating region F and the coating region C of the magnetic carrier overlap 5.6 mm.
Therefore, no current flows from the insulating region F on the charging sleeve 2b, so that the magnetic carrier 2d of 159.4 mm or less ends.
The charging potential at the contact portion between the photosensitive drum and the photosensitive drum 1 is 159.
It gradually decreases from the position of 4 mm, and becomes 0 at the position of 165 mm.
A slope of V is formed (corresponding to the formation of the end portion charging potential slope in FIG. 4), and a potential difference between the tip of the magnetic brush 2c and the surface of the photosensitive drum 1, that is, a magnetic carrier adhesion electric field does not greatly occur. Further, the thickness of the carrier container 2b is 1 mm, the inner wall thereof is located at 166 mm from the center, and a seal member for preventing leakage of the magnetic carrier exists outside the carrier container 2b. A 0.5 mm magnetic plate is attached. The length up to the end of the fixed mug 2a included in the charging sleeve 2b is 167 mm, and the charging sleeve 2b
The length between the ends is 180 mm.

Here, the seal configuration at the end of the charging sleeve 2b will be described.

As shown in FIG. 5A which is a longitudinal sectional view along the longitudinal direction of the charging sleeve 2b, the carrier container 2
At both ends in the longitudinal direction (the axial direction of the charging sleeve 2b) of the opening 2Ba of B, a plate-shaped Nd-
A Fe-B based rare earth resin magnet (hereinafter, referred to as “end magnet plate”) 41 is attached. However, only one of them is shown in FIG. This end magnet plate 41 is shown in FIG.
As shown in FIG. 1B, which is a view taken along the line XX of FIG. 1A, the minute interval g (0.4 mm in the present embodiment) is set so as not to be in contact with the surface of the charging sleeve 2b. The charging sleeve 2 is attached to the edge of the opening 2Ba at a distance.
b has a constant width in the axial direction (the longitudinal direction of the opening 2Ba). The charged area of the charging sleeve 2b is formed between the end magnet plates 41 attached to both ends of the charging sleeve 2b, and even if the magnetic carrier in the charged area leaks from the longitudinal end of the opening 2Ba to the outside, the end of the charging sleeve 2b is not removed. Part magnet plate 41
The magnetic carrier is prevented from leaking outside.

In the above-described embodiment, an image forming apparatus in which the process cartridge 30 (see FIG. 1) is attached to and detached from the image forming apparatus main body has been described. In such an image forming apparatus, even if an impact or the like is given to the process cartridge 30 when the process cartridge 30 is attached to or detached from the main body of the image forming apparatus, the end magnet plate 41 and the outer peripheral surface of the charging sleeve 2b may be in contact with each other. It is possible to reliably prevent the magnetic carrier from leaking from the minute gap g therebetween.

That is, in order to prevent carrier leakage even when an impact is applied to the process cartridge 30,
Although it is necessary to increase the magnetic force of the end magnet plate 41, in the present embodiment, as described above, the end magnet plate 41
Is composed of a plate-like Nd-Fe-B-based rare earth resin magnet, so that its magnetic force can be sufficiently increased. Therefore, it is possible to ensure sufficient sealing performance against vibrations and the like, and also ensure long-term insulating performance of the insulating member 43, thereby reliably preventing carrier leakage.

Here, the process cartridge is generally a cartridge in which a photosensitive drum (image carrier) and at least one process device are integrated into a cartridge container 30a to form a cartridge. Are at least a photosensitive drum 1 and a magnetic brush charging device 2
Means what is incorporated in the cartridge container 30a. In addition to the photosensitive drum 1 and the magnetic brush charging device 2 described above, other process equipment is used for the cartridge container 3.
Needless to say, the process cartridge 30 may be configured by incorporating the process cartridge 30 into the process cartridge 30.

Further, the magnetic brush charging device 2 described above
Instead of being incorporated in the process cartridge 30, it may be incorporated directly into the image forming apparatus main body.

For example, when a user moves the entire image forming apparatus and uses the apparatus, such as a portable copying machine or a portable printer, intense vibration may be applied during the movement of the image forming apparatus. Even for such a severe vibration or impact, the above-mentioned end magnet plate 41 ensures a sufficient sealing property and reliably prevents carrier leakage.

[0073]

As described above, according to the present invention,
At the end of the opening of the charging agent container, an end sealing member made of a rare earth resin magnet is provided so as to face the image carrier through a gap. The magnetic particles at the magnetized end of the magnetic field generating means can be restrained by the magnetic force of the magnetic field generating means and the magnetic force of the end seal member in a non-contact state. For this reason,
For example, even when the vibration is severe, even if the magnetic force of the end seal member is not particularly increased, the leakage of the magnetic particles can be reliably prevented, and the insulating region is formed at the end of the charging agent carrier. When the insulating member is provided, the end sealing member is not in contact with the insulating member, so that the insulating property can be maintained for a long time without damaging the insulating member.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically illustrating a schematic configuration of an image forming apparatus according to a first embodiment.

FIG. 2 is an enlarged vertical sectional view showing a configuration of a photosensitive drum according to the first embodiment.

FIG. 3 is a vertical sectional view showing a configuration of a magnetic brush charging device according to the first embodiment.

FIG. 4 is a diagram illustrating a configuration near an end of a charging sleeve and a positional relationship of each member in a charging sleeve axial direction according to the first embodiment.

FIG. 5A is a front view of the vicinity of an end of the charging sleeve according to the first embodiment. (B) is an XX line arrow view of (a).

FIG. 6 is a perspective view showing a configuration of a conventional magnetic brush charging device.

FIG. 7 is a diagram illustrating a charging potential in the longitudinal direction of the photosensitive drum during injection charging.

FIG. 8 is a diagram showing a conventional configuration near the end of a charging sleeve and a positional relationship of each member in the axial direction of the charging sleeve.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Image carrier (photosensitive drum) 2 Magnetic brush charging device (charging means) 2a Magnetic field generating means (magnet roller, fixed magnet) 2B Charging agent container (carrier container) 2Ba Opening 2Bb accommodating part 2b Charging agent carrier (charging sleeve) 2c Magnetic brush 2d Magnetic particles (magnetic carrier) 3 Exposure means (exposure device) 4 Developing device (developing device) 5 Transfer device (transfer device) 30 Process cartridge 30a Cartridge container 40 Magnetic seal member 40a Magnetic field lines 41 End seal member ( 43) Insulating member N1, N2, S1, S2, S3 magnetic pole P Recording material

Claims (8)

[Claims] 1. A magnetic brush charging device for charging a surface of an image carrier by bringing conductive magnetic particles to which a voltage is applied into contact with the surface of the image carrier as a charging agent, wherein a storage unit for storing the magnetic particles is provided. A charging agent container having an opening facing the surface of the image carrier; a rotatable charging agent carrier disposed in the opening; and a plurality of circumferentially enclosing the charging agent carrier. A magnetic field generating means having a magnetic pole, and a rare-earth resin magnet facing an outer peripheral surface of the charging agent carrier via a gap at an end of the opening along an axial direction of the charging agent carrier. And an end seal member comprising: (a) a magnetic brush charging device; 2. The method according to claim 2, wherein the end sealing member is Nd—Fe—B.
The magnetic brush charging device according to claim 1, wherein the magnetic brush charging device is configured by a system bond magnet. 3. The magnetic brush charging device according to claim 1, wherein the magnetic field generating means has two adjacent magnetic poles of the plurality of magnetic poles. 4. A process cartridge, wherein at least an image carrier and a charging unit for charging the image carrier are integrally incorporated in a cartridge container, and the process cartridge is detachably mounted to an image forming apparatus main body. A process cartridge, wherein the charging means is the magnetic brush charging device according to claim 1, 2 or 3. 5. An image carrier, charging means for charging the image carrier, exposure means for exposing the charged image carrier surface to form an electrostatic latent image, and 4. An image forming apparatus comprising: a developing unit that applies toner to develop a toner image as a toner image; and a transfer unit that transfers the toner image to another member. An image forming apparatus, comprising: the magnetic brush charging device according to claim 1. 6. An image carrier, charging means for charging the image carrier, exposure means for exposing the charged image carrier surface to form an electrostatic latent image, and An image forming apparatus including: a developing unit that applies toner to develop the toner image as a toner image; and a transfer unit that transfers the toner image to another member. An image forming apparatus, comprising: a process cartridge freely mounted; wherein the process cartridge is the process cartridge according to claim 6. 7. The image forming apparatus according to claim 5, wherein the image carrier has a charge injection layer on a surface. 8. The image forming apparatus according to claim 1, wherein the developing unit also serves as a cleaning unit that collects transfer residual toner remaining on the surface of the image carrier after transferring the toner image on the image carrier to the other member. The image forming apparatus according to claim 5, 6 or 7.