JPH0572905A - Image forming device - Google Patents

Abstract

PURPOSE:To secure a contact area which can be easily and smoothly electrostatically charged on a photosensitive drum even when the device can be miniaturized and formed by forming plural developer banks along the moving direction of the photosensitive drum at a gap part interposed by both members of the photosensitive drum and a developing sleeve. CONSTITUTION:In the image forming device which executes the electrostatic charge of the photosensitive drum 1 at the linear position of a developing position by utilizing the rubbing of the developer bank in order to execute developing almost simultaneously with exposure, two-component developer is contained in the developing sleeve 20 and carried to a faced position between the drum 1 and the sleeve 20 by utilizing the magnetic force of a fixed magnetic pole assembly 21 while the drum 1 and the sleeve 20 are mutually reversely rotated. The two-component developer carried to the faced position forms the first developer bank A1 by the magnetic pole S of the assembly 21 first and forms the second developer bank A2 on the upstream side of the moving direction of the drum 1 by interposing a vertical line HH'. In such a case, insulating or high-resistance toner is used for the developer.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for charging while rubbing an image forming layer by a developer pool formed on the upstream side and the downstream side of a developing position, and in particular, developing is carried out almost simultaneously with exposure. For this reason, the present invention relates to an image forming apparatus that charges the image forming body at a position immediately before a developing position by utilizing the rubbing of the developer pool.

[0002]

2. Description of the Related Art Conventionally, on the inner peripheral side of a photosensitive drum formed by laminating a transparent conductive layer and a photoconductive layer on a transparent support,
Arrangement of exposure means for generating light output corresponding to image information,
After focusing the light output of the exposing means to form a latent image on the photoconductor layer, or immediately after that, the latent image is converted into a toner image through a developing means facing the photosensitive drum. An image forming apparatus is known in which the toner image can be transferred onto plain paper through a transfer roller or other transfer means. (JP-A-58-153957, etc.)

In this type of image forming apparatus, in order to further simplify the configuration, prevent ozone generation, etc., and prevent background fogging, the image forming apparatus does not have an independent charger and faces the photosensitive drum. The conductive magnetic toner is carried on the developing sleeve arranged in the same manner, and a so-called magnetic brush-shaped toner sliding area is provided immediately before the developing position by utilizing the magnetic force of the fixed magnetic pole or the like contained in the sleeve. After charging by charging the photoconductive layer of the drum through the rubbing area by utilizing the developing bias applied to the developing sleeve side while rubbing the surface of the photosensitive drum by the rubbing area, Immediately after the charging, a latent image is formed by using an exposure head contained in the drum, and a predetermined image is formed by developing with a toner.

[0004]

According to the paper of the Institute of Image Electronics Engineers of Japan, No. 16, No. 5, No. 5, the recording speed of the drum rubbing area due to the toner accumulation is 2.5 in the apparatus of the above construction. In the case of cm / sec, a contact area of about 10 mm width is required, but the height of the toner bristles formed by the magnetic force of the fixed magnet assembly contained in the sleeve is very small. In order to secure it, the photosensitive drum and the developing sleeve must have a large diameter, or the sleeve must be formed in a flat shape and the wedge-shaped space formed on the upstream side of the developing position must be set to be extremely narrow. It has been extremely difficult to form a developer pool that can be charged smoothly.

On the other hand, in order to satisfy the demand for downsizing, it is effective to reduce the diameters of the photosensitive drum and the developing sleeve. However, with this structure, the formation angle of the wedge-shaped space is widened. However, in the device having the above-mentioned configuration, in which a developer pool capable of securing the contact area cannot be formed, and as a result, a large restriction is imposed on achieving a reduction in the diameter of both members and a reduction in the size of the device. receive.

In view of the above-mentioned drawbacks of the prior art, the present invention can provide an image forming apparatus capable of easily ensuring a contact area on the photosensitive drum that can be smoothly charged even if the diameters of both the members and the apparatus are reduced. The purpose is to provide.
Another object of the present invention is to provide an image forming apparatus capable of surely performing development together with the charging, thereby forming a high quality toner image.

[0007]

In order to achieve the above-mentioned technical object, the present invention is provided in a space between both members of the image forming member and the developer carrying member along the moving direction of the image forming member. It is characterized in that a plurality of developer pools are formed.

As a method of forming such a plurality of developer pools, for example, the developer is formed of a magnetic developer, and magnetic fields are respectively provided on the upstream side and the downstream side of the closest position of the spacing portion. By forming the plurality of developer reservoirs by using the magnetic field, a wider rubbing area can be formed.

In this case, a plurality of developer reservoirs can be formed by setting the magnetic pole position of the magnet assembly included in the developing sleeve functioning as the developer carrying member, but a plurality of developer reservoirs can be formed at narrow positions. It is practically difficult to arrange the magnetic pole positions of. Therefore, in the present invention, the developer pool forming means is separated, one developer pool is formed by the magnet assembly, and the other developer pool is formed by a magnet body arranged on the inner peripheral surface side of the photosensitive drum. As a result, it becomes easy to form a plurality of developer reservoirs at narrow positions. Further, the magnetic pole may be provided with a thin line-shaped magnetic material in a space between the developing sleeve and the photosensitive drum.

On the other hand, it is preferable for the charging step to lengthen the rubbing area, but especially when a conductive toner is used as the developer, the developer again rubs the photoreceptor after exposure. If the area becomes longer, recharging tends to result in a decrease in image density due to the recovery of toner on the photoconductor and a decrease in resolution due to toner collision. In such a case, as described in claim 6, by forming the exposure position on the rubbing area with a slight shift to the downstream side in the moving direction of the image forming body from the closest position of the interval portion, the charging area is formed. Can be dealt with by shortening the rubbing area after exposure while taking longer.

Further, without using a conductive toner as the developer,
The use of the insulating toner is preferable, because even if the rubbing area after the exposure becomes long, the fog does not occur and the development can be surely performed on the contrary, which is preferable.

However, when a high-resistance or insulating toner is used, the charging step of injecting charges from the developing bias cannot be taken, and only frictional charging is performed, which makes smooth charging difficult. In this case, smooth charging can be easily performed by using a two-component developer composed of a combination with a conductive carrier as the developer. According to a preferred embodiment, the conductive carrier is formed by fixing conductive fine particles 17 on the surface of particles 13 in which a magnetic material 15 is dispersed in a binder resin as shown in FIG. Is preferably set to 1 to 5 times the toner diameter so that both the carrier and the toner can form a pool due to the magnetic field.

Further, by making the image forming body and the developer carrying body movable in opposite directions, the rubbing speed between both members becomes high, which is preferable for charging. Yes.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described in detail below as an example with reference to the drawings. However, unless otherwise specified, the dimensions, materials, shapes, relative positions, etc. of the components described in this embodiment are not intended to limit the scope of the present invention thereto, but are merely illustrative examples. Not too much. Figure 1
FIG. 1 is a basic configuration diagram showing the present invention. Reference numeral 1 denotes a photosensitive drum, which is formed in a flat plate shape in order to allow the present invention to be schematically understood. In this embodiment, the transparent conductive layer 1b and the photoconductive layer 1c are formed on the drum-shaped transparent support 1a.
And a developing bias is applied between the translucent conductive layer 1b and a developing sleeve 20 described later, and can be rotated clockwise (rightward in the drawing) by a drive motor (not shown). Is configured. Next, the photosensitive drum will be described in detail. Translucent support 1a
Is a transparent inorganic material such as glass, quartz, sapphire,
There are transparent resins such as fluororesin, polyester, polycarbonate, polyethylene, polyethylene terephthalate, vinylon, epoxy and mylar, which are formed in a drum shape. The transparent conductive layer 1b is made of a transparent conductive material such as ITO (indium / tin / oxide), lead oxide, indium oxide, or copper iodide, or is semitransparent to a metal such as AI, Ni, or Au. It may be formed as thin as possible. Photoconductor layer 1
c is a photoconductor made of a-Si: H, and contains non-doped or a Va group element in order to increase electron mobility when the developing bias is positive, and when the developing bias is negative, In order to enhance the mobility of holes, it is preferable to contain a Group IIIa element. If necessary, elements such as C, O and N may be contained in order to obtain desired characteristics such as electrical characteristics such as dark conductivity and photoconductivity, and optical bandgap. Further, the photoconductor layer 1c is formed from two layers, that is, a photoexcitation layer region having a function of generating photocarriers from the back side and a layer region having a function of carrier transport, thereby enhancing photosensitivity and withstand voltage. You can

On the other hand, the developing sleeve 2 with the drum 1 interposed therebetween.
An exposure head 3 is fixedly arranged on the back side of the drum 1 facing 0. The exposure head 3 is formed of an LED or EL head array 31 that generates a light output corresponding to image information and a converging lens 32 (trade name: SELFOC lens), and the image forming position of the lens 32 is set to the photosensitive drum 1. On the vertical line connecting the axis of the developing sleeve 20 with the developing sleeve 20 and slightly deflected to the downstream side (right side) in the moving direction of the drum 1 so as to form an image on the photoconductor layer 1c in the drum 1. Is configured.

On the other hand, a belt-shaped magnet body 10 extending in the drum axial direction is formed on the drum rear surface side slightly upstream of the vertical line, and the magnetic field of the magnet body 10 causes the drum at the exposure position. On the upstream side in the moving direction, the developer pool A2
Is formed. The development pool A1 is easily formed by reversing the moving directions of the drum and the developer, or may be formed by the magnetic pole position of the fixed magnet assembly 21.

The fixed magnet assembly 21 contained in the developing sleeve 20 has eight magnetic poles, and one S pole 21a of the magnetic poles is positioned slightly downstream of the vertical line. The reason why the magnetic pole arranged on the downstream side is the S pole is that it is necessary to set the adjacent magnetic pole N pole 21b so that the magnetic pole S having the opposite polarity to the magnetic pole S of the facing strip-shaped magnet body 10 comes. Is. Further, the developing sleeve 20 is configured to be rotatable in a counterclockwise direction opposite to the photosensitive drum 1. Thereby, the moving directions of the developer and the drum 1 are set in opposite directions.

Next, the composition of the developer will be described. Figure 3
FIG. 3 is a schematic view showing an example of a carrier used in the developer of the present embodiment, in which conductive fine particles 17 are fixed on the surface of carrier mother particles 13 in which a magnetic material 15 is uniformly dispersed in a binder resin. 11 are configured.

The carrier 11 has a volume resistivity of 10 ⁴ Ω.
・ It is preferably not more than cm, more preferably 10
^{It is 2} to 10 ⁴ Ω · cm. The conductivity of the carrier 11 is mainly given by the conductive fine particles 17. The volume resistivity of the carrier 11 was measured by putting 1.5 g of the carrier 11 into a Teflon cylinder having an inner diameter of 20 mm and having an electrode at the bottom, inserting an electrode having an outer diameter of 20 mmφ, and applying a load of 1 kg from the top. The hour value.

The magnetic force of the carrier 11 needs to be large to some extent or more, and the maximum magnetization in a magnetic field of 5 kOe (Oersted) is preferably 55 emu / g or more, more preferably 55 to 80 emu / g. Carrier 1
If the magnetic force of 1 becomes too small, the developer transportability deteriorates, and the carrier 11 is developed together with the toner.
The average particle size of the carrier 11 is preferably set to 1 to 5 times that of the toner. For example, when the toner has an average particle size of 5 to 10 μm, 10 to 50 μm is preferable, and 1 is more preferable.
It is preferable to set it to 5 to 25 μm. If the carrier 11 becomes too large, it will be difficult to uniformly charge the photoconductor, and the image formation will be hindered.
It becomes impossible to increase C. On the other hand, if it is too small, the transportability of the developer on the developing sleeve deteriorates,
In addition, it becomes difficult to apply a constant potential.

As the magnetic material, magnetite (F
e ₃ O ₄ ), ferrite (Fe ₂ O ₃ ) and the like are used, and magnetite is particularly preferable, but not limited to this. As the conductive fine particles 17, carbon black, tin oxide, conductive titanium oxide (titanium oxide coated with a conductive material), silicon carbide, or the like is used, and the conductivity is not lost by oxidation by oxygen in the air. Things are desirable. As the binder resin used for the carrier mother particles 13, a resin such as a vinyl resin typified by a polystyrene resin, a polyester resin, a nylon resin, a polyolefin resin, or the like that is heat-melted by a fixing device is used. As with the toner, it is preferable to use a resin colored in black.

The conductive fine particles 17 are fixed to the surface of the carrier mother particles 13 by, for example, uniformly mixing the carrier mother particles 13 and the conductive fine particles 17, and attaching the conductive fine particles 17 to the surface of the carrier mother particles 13. After that, a mechanical and thermal impact force is applied and the conductive fine particles 17 are fixed by being driven into the carrier mother particles 13. The conductive fine particles 17 are not completely embedded in the carrier mother particles 13, but are fixed so that a part thereof protrudes from the carrier mother particles 13.

By fixing the conductive fine particles 17 on the surface of the carrier 11 in this manner, the carrier 11 can be efficiently used.
It can provide high conductivity. In addition, carrier mother particles 13
Since it is not necessary to mix the conductive fine particles 17 therein, a larger amount of the magnetic material 15 can be mixed in the carrier mother particles 13, and the magnetic force of the carrier 11 can be increased.

The above carrier and toner are mixed to form a developer. As a toner, a normal average particle diameter is 5 to 20 μm.
m insulating toner is used, and the volume resistivity thereof is preferably 10 ¹⁴ Ω · cm or more, more preferably 1
0 ¹⁶ Ω · cm or more. This value is measured as for the carrier. The toner composition is a binder resin,
A colorant, a charge control agent, an offset preventive agent, and the like are mixed, and a magnetic substance is added to obtain a magnetic toner.

According to this embodiment, the fixed magnetic pole assembly 21 in which the two-component developer is contained in the sleeve 20 while rotating the photosensitive drum 1 and the developing sleeve 20 in opposite directions.
The two-component developer, which has been conveyed to the facing position between the drum 1 and the sleeve 20 by utilizing the magnetic force of the magnetic field, is first transferred to the first developer pool A1 by the magnetic pole S of the fixed magnet assembly. Also, a second developer pool A2 is formed on the upstream side in the drum moving direction across the vertical line, and as a result, the developer sliding areas B and C can be greatly expanded. In this case, since magnetic powder is contained in the carrier 11 like the toner, the carrier 11 is smoothly held in the rubbing area.

Further, since the exposure position of the exposure head 3 is set on the side of the first developer pool A1 with respect to the vertical line, it is inevitable that the charging and rubbing area B can be long. In the rubbing area B, charges are injected into the photoconductive layer 1c of the drum 1 via the carrier 11 mixed in the rubbing area B by utilizing the developing bias applied to the developing sleeve 20 side. After charging, immediately after the charging, an exposure image is formed by using the exposure head 3 included in the drum 1, and toner is attached to the exposed portion to perform development.

Further, since the toner is an insulating toner, there is no fear of injecting reverse polarity charges from the drum side such as conductive toner once the toner adheres to the exposed portion,
As a result, the reliability of the development can be ensured even when the development area C on the downstream side of the exposure position is set to be large to some extent.

When the conductive fine particles 17 on the surface of the carrier mother particles 13 are peeled off due to the rubbing and the resistance value is increased and a developing force exceeding the magnetic force absorbed by the sleeve 20 is generated, the carrier 11 becomes toner. With photoconductor drum 1
It is attached to the side, developed and consumed. Therefore, the rubbing areas B, C
It is preferable that the new carrier is always replenished without fatigue.

Next, FIG. 2 shows the structure of an image forming apparatus according to an embodiment of the present invention, which is constructed based on the basic configuration diagram. The photosensitive drum 1, the exposure head 3 and the strip-shaped magnet body 10 inserted in the drum 1 have the same configurations as described above. A developing device 2 is composed of a toner container 22 and a container body 23 containing a carrier and toner.
Of the fixed magnet assembly 21 on the side facing the photosensitive drum 1.
And a developing sleeve 20 that encloses the developing sleeve 20. The developing sleeve 20 is configured to be rotatable in the counterclockwise direction opposite to the photosensitive drum 1.

The toner container 22 and the container body 23 are separated from each other by a partition wall 24. A replenishing roller 25 is arranged in a slit opening provided at the center of the partition wall 24, and the container body 23 is responsive to a signal from a sensor 26. The replenishing roller 25 is rotated every time the carrier / toner compounding ratio (toner density) is decreased, and is always maintained at an appropriate density ratio. Further, a pair of mixers 27 composed of magnet rolls and the like are arranged in the container body 23 to maintain the carrier / toner compounding ratio in the container body 23 at a uniform concentration.

Further, a doctor blade 28 is attached to the inlet end of the container 23 on the lower surface side of the developing sleeve 20 so that the developer introduced to the developing position can be regulated in a thin film.
Further, in the figure, 4 is a transfer roller, 5 is a registration roller, and 6 is a paper detection sensor. As the transfer roller 4, a conductive roller is used in order to improve transfer efficiency, a transfer bias having a polarity opposite to the charging potential of the toner is applied, and the transfer roller 4 is uniformly pressed against the peripheral surface of the photosensitive drum 1 to synchronize with the drum 1. And make it rotatable. The material of the transfer roller 4 need not be electrically conductive because the toner to be transferred is an insulating toner.

According to this embodiment, the image forming operation of the present invention can be smoothly achieved, and the carrier is always supplied from the developing container side due to the consumption of the carrier, but when the carrier is consumed to some extent, The toner container 22 is interrupted by interrupting the image forming operation based on a replenishment signal (not shown).
It is preferable that the developing container 23 is detached and the carrier is replenished in the developing container 23. ..

[0033]

As described above, according to the present invention, it is possible to easily secure a contact area in which the photosensitive drum can be charged smoothly even when the diameters of both the members are reduced and the apparatus is downsized. Further, according to the present invention, it is possible to surely perform the development together with the charging, which makes it possible to form a high quality toner image. And so on.

[Brief description of drawings]

FIG. 1 shows a basic configuration diagram of the present invention.

FIG. 2 illustrates a cross-sectional configuration of an image forming apparatus according to an exemplary embodiment of the present invention.

FIG. 3 is a composition diagram of a conductive carrier that constitutes a developer.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 2 Development means 3 Exposure means 21 Magnet assembly 11 Carrier 10 Strip-shaped magnet bodies A1, A2 Developer pool

Claims (6)

[Claims] 1. An image forming apparatus for performing charging substantially simultaneously with exposure after charging while rubbing the surface of the image forming body with a developer pool interposed between the image forming body and the developer carrying body, Insulating or high-resistance toner was used as the developer, and a plurality of developer reservoirs were formed along the moving direction of the image forming body at the space between the members of the image forming body and the developer carrying body. A characteristic image forming apparatus. 2. The developer is a magnetic developer, and
The image forming apparatus according to claim 1, wherein a magnetic field is formed on each of an upstream side and a downstream side of the closest position of the space portion, and the plurality of developer reservoirs are formed by using the magnetic field. 3. The magnetic developer is used as the developer, and
2. The image forming apparatus according to claim 1, wherein magnetic poles are respectively arranged on the back side of the image forming body and the back side of the developer carrying body, and the developer pool is formed by using the two magnetic poles. 4. The image forming apparatus according to claim 1, wherein the developer is a two-component developer including a conductive carrier and high-resistance or insulating toner. 5. The image forming apparatus according to claim 1, wherein the image forming body and the developer carrying body are movable in opposite directions. 6. An image forming apparatus for performing charging substantially simultaneously with exposure after charging while rubbing the surface of the image forming body with a developer pool interposed between the image forming body and the developer carrying body, A plurality of developer reservoirs are formed along the moving direction of the image forming body at a gap portion sandwiched between the image forming member and the developer carrying member, and the exposure position is formed from the closest position of the gap portion to form an image. An image forming apparatus characterized in that it is formed with a slight shift to the downstream side in the body movement direction.