JPS61110177A - Developing device - Google Patents

Abstract

PURPOSE:To prevent a developer from being blown out of a developer container by providing a developer blow-out preventive member which projects toward a developing sleeve to the front edge part of the bottom surface wall of the developer container. CONSTITUTION:The developer blow-out preventive member 21 which has the upper side projected toward the developing sleeve 10 along the lengthwise edge part is provided to the front edge part of the developer container bottom surface wall 12a. The length of this member 21 is nearly equal to the length of the sleeve 10 or longer than the at least the maximum lateral width of a recording material in use. Consequently, air (a) containing tone made into a powder cloud in the container 12 flows along the bottom surface wall 12a to strike the internal wall 21a of the member 21, and is deflected in the direction to the sleeve 10. Consequently, the powder cloud of toner is caught in the deflected air flow in an intense magnetic field which operates on the periphery of the sleeve 10 to stick on the sleeve 10 and is recovered in the developer container as the sleeve 10 rotates.

Description

Detailed Description of the Invention A. Purpose of the Invention [Industrial Field of Application] The present invention is directed to the production of photoreceptors, insulators, magnetic materials, etc. using appropriate image forming techniques such as electrophotography, electrostatic recording, and magnetic recording. The present invention relates to a developing device that visualizes an electrical latent image, such as an electrostatic latent image, a potential latent image, or a magnetic latent image, formed on the surface of an image carrier using a dry powder developer.

More specifically, the dry powder developer stored in the developer container is formed and retained as a developer layer on the surface of the developer carrying member, and is continuously transported out of the developer container, and the transported developer layer is electrically latent. The developer is applied to the surface of the image carrier to develop the latent image, and the remaining developer layer that was not subjected to development is retained on the surface of the developer carrier and transported back into the developer container to develop the latent image. The present invention relates to an improvement in a developing device (hereinafter referred to as a developer layer circulating developer layer) that continuously performs the following steps.

[Conventional technology]

FIG. 5 is a schematic diagram of an example of a general electrophotographic apparatus equipped with a developing device of a developer layer circulation conveyance type.

1 is an electrophotographic photosensitive drum, which rotates in the direction of the arrow. After the photosensitive drum 1 is uniformly charged by the corona charger 2, an electrostatic latent image is formed by applying image exposure 3. This latent image is visualized using a dry powder developer (hereinafter referred to as toner) 11 in a developing device 4. On the other hand, the sheets 8 loaded in the cassette 12 are sent out by a pickup roller 13, once stopped by a register roller 9, and then sent out to the transfer charger 5 in synchronization with the image on the photosensitive drum 1. The transfer charger 5 applies corona charging to the back side of the sheet 8 with a polarity opposite to that of the toner, thereby transferring the toner image on the photoreceptor drum 1 to the sheet 8 side. After the transfer process, the sheet 8 is separated from the photoreceptor drum 1'' by the separating means 14.The sheet 8 is then guided to the fixing device 6 by the conveyance guide 15, and the toner image on the sheet is fixed on the drum. The toner remaining without being transferred is collected by the cleaner 7.

Thereafter, unnecessary charges remaining on the photoreceptor drum 1 are erased by the pre-exposure lamp 16, and the process of forming a latent image can be performed again.

FIG. 6 is an enlarged view of the developing device. Reference numeral 12 denotes a developer container, which contains monocomponent magnetic toner 11 as a developer. Reference numeral 10 denotes a non-magnetic developing sleeve made of aluminum or the like as a developer carrying member, which is located on the lower left side of the developer container 12, with approximately the left half circumferential surface exposed to the outside of the developer container, and the substantially left half circumferential surface being inside the developer container. It is positioned and supported by a bearing so that it can rotate freely, and is driven to rotate at a predetermined circumferential speed in the direction of the arrow. The developing sleeve 10 has a length that is approximately the same as the effective image forming width (in the drum generatrix direction) of the photosensitive drum 1, which is an image carrier. 18 is a fixed (non-rotating) magnetic roller inserted and built into the developing sleeve lO', N, -3,
・N2 and S2 are magnetic poles.

Reference numeral 17 denotes a doctor blade made of a magnetic material and serving as a developer layer thickness regulating member, the lower end of which is disposed close to the upper surface of the developing sleeve 10 .

The developing device 4 is disposed with respect to the photosensitive drum 1 serving as an image carrier, with the externally exposed side of the developing sleeve 10 facing the surface of the drum 1 and with the sleeve axis parallel to the drum axis.

The S2 pole of the magnet roller 18 faces the toner (developer) reservoir in the developer container 12, and
The toner magnetically adheres to the surface, and in cooperation with the rotation of the sleeve 10, the toner near the sleeve surface is agitated to triboelectrically charge the toner. Nl pole is doctor blade 17
are opposed to each other, and the magnetic field formed between the two serves to regulate the thickness of the developer layer on the developing sleeve. The 51 pole faces the photosensitive drum 1 and functions as a developing pole. The N2 pole faces the bottom wall 1-2a of the developer container 12 and holds the single layer of toner that has not been subjected to development on the sleeve 10 surface. It acts as a collection pole for transporting the developer back into the developer container.

The substantially left half circumferential surface of the developing sleeve 10 is in constant contact with the toner reservoir in the developer container 12, and the toner near the sleeve is magnetically attached to the sleeve surface by the S2-like magnetic field, thereby driving the rotation of the sleeve IO. Doctor Blade 1
The layer thickness is regulated to a substantially uniform layer thickness in each part by rotation passing through that position.
A got an electric shock.

It passes facing the optical drum 1. A developing bias is applied to the developing sleeve 10, and the first layer 11a of the toner 11a passes through the drum 1 while the first layer 11a of the layer thickness regulating toner 11a passes through the drum 1.
The latent images on the circumferential surface of the drum 1 are sequentially developed (jumping development, Japanese Unexamined Patent Publication No. 18858/1983) by selectively shifting in accordance with the latent image pattern on the surface side, and are not subjected to development. The remaining toner fiLlb is transferred to the subsequent sleeve 10.
As the toner rotates, it is held as it is on the sleeve surface by the magnetic force of the N2 pole and returned to the developer container 11, where it mixes with the toner in the toner reservoir.Alternatively, although not shown in the figure, a portion of the toner is removed from the sleeve surface by a scraper. The toner is scraped off and mixed with the toner in the toner reservoir, and is again magnetically attached to the sleeve surface by the magnetic force of 52 poles, and is conveyed to the doctor blade 17 position.

There is also a configuration in which the developing sleeve 10 is rotationally driven in the opposite direction (counter direction) to the rotating direction of the photosensitive drum 1, which is an image carrier. There is also one in which the developing sleeve 10 is an endless rotating belt.

There is also a configuration in which the developing sleeve 10 is fixed (non-rotating) and the internal magnetic roller 18 is rotated clockwise or counterclockwise to transport a layer of toner along the circumferential surface of the fixed sleeve 10.

There is also a structure in which a layer of toner on the surface of the developing sleeve 10 is brought into direct contact with the surface of the photosensitive drum serving as an image carrier to develop a latent image (contact development).

Some use a one-component conductive developer or a two-component developer as the developer.

[Problem that the invention seeks to solve]

By the way, one of the problems with the developer layer circulation conveyance type developing device as described above is that the remaining developer layer 11b that has not been subjected to development is returned to the developer container 11 on the side where it is conveyed. Developer container wall 12a' and developer carrying member 1
An example of this is a phenomenon in which the developer in the container blows out from the gap α with the 0th surface. This phenomenon will be explained using the apparatus shown in FIG. 6 as an example.

(a) As the toner 11 in the developer container 12 is sequentially subjected to development and consumption progresses, as shown in FIG.
2, an eave-like protruding toner block portion 11C of the toner 11 is formed on the developing sleeve 10. This growth occurs because the toner conveyed by the rotation of the sleeve 10 in the direction of the arrow is blocked by the doctor blade 17 and is restrained by the magnetic field of the magnet roller 18. When the toner blowing portion 11c extends to a certain length, it breaks from the tip due to its own weight and vibrational force and falls to the bottom of the developer container. As the toner falls, a powder cloud of toner is generated inside the container 12, and a part of it is deposited in the gap α.
It easily passes through and blows out of the container 12 as shown by arrow a. In this case, if toner remains in the shaded area lid, it acts as a barrier to the toner 11c falling from the ball, so even if the toner 11c falls, the toner remains in the container 1.
2, the toner does not blow out, but the toner in this lid portion will eventually be consumed, and after that, the toner will be able to blow out.

(b) In recent years, electrophotographic devices have become more compact, and in particular, the developer 4, cleaner 7, charger 2, etc. located around the photoreceptor drum 1 have been grouped together and can be inserted and removed from the device body and replaced easily. Model 22 with process cartridge configuration
<It is starting to be adopted. Such a cartridge model is described in, for example, Japanese Patent Laid-Open No. 58-25650.

In this type of process cartridge, as shown in FIG. 8, before the cartridge is used, the toner 11 in the developer container 12 is separated from the lower part of the container where the developing sleeve 10 is located by the partition member 19, and during transportation, etc. Toner 1
1 is prevented from spilling.

However, when the partition member 19 is removed when the cartridge is used, the toner 11 that was in the upper part of the container 12 suddenly falls to the lower part of the container and forms a powder cloud, and part of it forms as shown by arrow a in FIG. It easily passes through the gap α and blows out of the container 12.

In both cases (a) and (b) above, especially when -component magnetic toner is used, the magnetic binding force acting between the developing sleeve and the toner is relatively weak and the toner tends to blow out easily. be.

Due to the above-mentioned toner blowout, the toner falls onto the transfer material and stains the transfer material, and also adheres to the surface of the photosensitive drum, causing clouds in the resulting image as shown in FIG. 10. The image quality deteriorates by causing stains such as spots and spots. In addition, toner particles scatter and adhere to various parts within the electrophotographic apparatus, contaminating the inside of the apparatus, and adhere to the optical system and charger, causing white streaks and black streaks in formed images.

Conventionally, the developing device used could take a sufficiently large shape, so the developer container 1 as shown in FIG.
A rotating acid is provided with an oscillating stirring rod 20 to restrict the growth of the eaves-like toner block 11C as shown in FIG. Ta. However, in order to make it into a cartridge,
It is necessary to downsize the developing device, and the inclusion of the stirring rod 2o is undesirable because it complicates the structure and shortens the durable life of the toner, and it is also undesirable from a cost perspective.

In addition, in order to make the developing device smaller and lighter, it is necessary to make the magnet roller 18 smaller.
- If sufficient magnetization is applied to each magnetic pole of the N2 pole, there will be no space to place the toner blowout prevention magnet M, and if the sleeve lO is made small in diameter, the toner coat (toner single layer) will tend to become unstable. , Magnet) M is disadvantageous in that white streaks occur in the toner coat on the sleeve 10 and areas with low density also appear on the image.

In addition, the developer container wall 12 in the shaded lid portion in FIG.
It is also possible to reduce the gap between the developing sleeve 1o and the developing sleeve 1o, but if the developer container 12 is bent, the container wall 12b will come into contact with the sleeve 10 and damage the sleeve. There is a drawback that a black bar-shaped pattern C appears periodically on the image as shown as the sleeve rotates.

The present invention effectively suppresses the phenomenon of developer blowing out of the container in a developer layer circulation conveyance type developing device as described above, and also effectively suppresses the phenomenon of developer blowing out of the container. It is an object of the present invention to make it possible to reduce the size and weight of a developing device without causing any hindrance to other devices, and to configure, for example, a compact process cartridge that is easy to handle.

Summary: Structure of the Invention [Means for Solving Problems] The present invention provides a developer container in which dry powder developer contained in the developer container is formed and held as a developer layer on the surface of a developer carrying member. The developer layer is continuously transported outside, and the transported developer layer is applied to the surface of the electrical latent image carrier to develop the latent image, and the remaining developer layer that has not been subjected to development is applied to the surface of the developer carrier member. In a developing device that continuously develops a latent image by holding the layer as it is and transporting it back into the developer container, the remaining developer layer that has not been subjected to development is returned to the developer container. A member for preventing blow-out of the developer inside the container is provided in a gap between the developer container wall on the side to be carried in and the surface of the developer carrying member by protruding from the developer container wall toward the developer carrying member. The gist is a developing device characterized by the following.

[For production]

When the developer blowout prevention member is provided as described above,
The powder cloud wind of the developer that is about to blow out from inside the developer container to the outside through the above-mentioned gap hits the inner surface of the blowout prevention member and is deflected toward the developer carrying member, so that the developer carrying member surface side It is captured and collected in the developer container together with the undeveloped developer layer on the surface of the developer carrier, which is transported back into the developer container, and the formed developer is prevented from being substantially blown out to the outside. It is something that will be done.

〔Example〕

Embodiment 1 (FIG. 1) Reference numeral 21 denotes a developer blow-out prevention member, which is provided at the tip edge of the bottom wall 12a of the developer container along the length of the edge, with its upper side protruding toward the developing sleeve 10. The length of the zero member 21 is approximately the same as the length of the sleeve IO, or at least longer than the maximum width of the recording material (transfer material) 8 used.

The air a containing the toner that has formed into a powder cloud due to the reasons described in (a) and (b) in the developer container 12 is removed from the container through the gap α along the bottom wall 12a of the developer container as shown by the arrow. flows in the direction of exit. This flow of air a hits the inner surface 121a of the developer blow-out prevention member 21, and its flow direction is deflected toward the developing sleeve 10 as shown by the arrow.

As a result, the powder cloud-shaped toner in the deflected air flow is caught in the strong magnetic field acting around the developing sleeve 10, adheres to the sleeve 10, and is collected inside the developer container as the sleeve 10 rotates. be done. In this way, in order to collect the toner that blows out, in order to direct the flow of air containing toner in the form of a powder cloud flowing out along the bottom wall iza of the developer container toward the developing sleeve 10. The angle θB between the inner wall 21a of the blowout prevention member 21 and the bottom wall 12a of the developer container is 00>θE.
＞90°. In addition, the blowout prevention member 2
The extension line of the inner wall 21a (DE) of 1 is the sleeve lO
The point where it intersects with the surface of DE is defined as B, and the angle OB formed by the tangent line of the sleeve 10 at that point B and the extension line of DE is 180°.
It is necessary that θB<45°. This is because developing sleeves have become more compact in recent years, and the magnetic flux density B, the distance r from the axis of the magnet roller 18, and the angle 9 in the circumferential direction of the sleeve have characteristics that make it easy for the magnetic flux density B to change rapidly in the circumferential direction of the sleeve. More and more people have this. For such items, if air is blown against the sleeve surface in a state where θB is 45 degrees or less, the velocity component (V r, Vt) of the air flow will be Vr<Vy, so in the circumferential direction of the sleeve. The air containing toner moves quickly in the direction of the flow, and may quickly escape from the magnetic field that can sufficiently restrain the toner. Therefore, as a condition for restraining the toner even in such a case, it is necessary that V<Vr, that is, each θB>45° at which the air flow hits the sleeve.

Further, the outer wall 2l of the developer blowout prevention member 21
b (Also for 1(:), its extension line is sleeve lO
Let A be the point where it intersects with the surface of the sleeve, and considering the air flow indicated by arrow J, the angle θA between the tangent to the sleeve at point A and the extended line of the IC is 18Q for the same reason as before. °〉OA>45° holds true.

Further, in order to allow the air to flow as indicated by the arrow, it is desirable that 180°>OA>90°, which is a condition for flowing air into the developer container. This makes it possible to further push the toner-containing air that tends to blow out of the developer container back into the developer container. In addition, it is preferable that the quadrilateral formed by B-C-D has a relationship of sides ACABD, which means that when air flows from BD to AC, AC>B
It is obvious that the slower the flow of air containing toner, the easier it is to collect on the sleeve, which is determined by the fact that D allows the flow of air to be slower.

The distance ra (gap) between the sleeve 10 and the upper surface of the developer blowout prevention member 21 is 1.0 to 4.01, especially 2 to 3+a.
m is preferable, if the gap is narrowed to less than this value.

When the developing device is bent, the blow-out prevention member 21 may come into contact with the sleeve 10 and cause scratches. On the other hand, if the gap is widened further than this, the blowout prevention effect cannot be sufficiently obtained.As mentioned above, the gap is 2.0 to 3.0H, and the magnetic flux density in this gap is at least 200 Gauss or more. If so, a good developer blow-out prevention effect can be obtained.

Further, the gap between the drum 1 and the developer blowout prevention member 21 is preferably 1t+s or more. This is necessary so that the developer blowout prevention member 21 does not come into contact with the drum 1 and does not disturb the toner image on the drum. It is a distance. Further, in order to prevent the toner on the drum l from being electrostatically attracted, the developer blow-out prevention member 21 preferably has a frictional charge polarity that is the same as that of the developer.

Embodiment 2 (FIG. 2) In this example, in the developing device shown in FIG. along the length of the tip edge of the bottom wall 12a, and the upper side of the bottom wall 12a
It is provided so as to protrude toward the developing sleeve 10 so as to face a portion other than the boundary between the Sl pole and the N2 pole of No. 8.

When the plate member 21, which is a developer blowing member, is made of a magnetic material, the blown toner accumulates at the tip of the plate member 21 and becomes brush-like and comes into contact with the developing sleeve 10, so that the toner coat on the sleeve 10 is reduced. This is undesirable because the image becomes non-uniform and excessive unevenness occurs on the image.

In addition, when the tip of the plate-like member 21 is brought close to and opposed to the weak magnetic field part at the boundary between the S1 pole and the N2 pole, the magnetic field prevents the toner that is about to blow out from the gap between the sleeve 10 and the plate-like member 21. Therefore, in this embodiment, the magnetic field between the blowout prevention member 21 and the sleeve is preferably 150 Gauss or more.

Moreover, the installation state of the blowout prevention member 21 is different from θE and θAllθB explained in the first embodiment.
EE = 58.8°, θx = 70°, θa = 78c'L
was set, and good results were obtained in preventing developer blow-out.

That is, the flow of air containing toner that is about to blow out from the developer container 12 through the gap α to the outside of the container is caused by the plate member 2.
1, the developer is directed toward the N2 pole, is almost caught by the magnetic field of the N2 pole, is attracted onto the sleeve 10, and is collected in the developer container. Furthermore, the toner that attempts to come out beyond the plate member 21 is also guided close to the sleeve and N2
It is captured by the strong magnetic field of the pole or S+ pole.

Embodiment 3C (FIG. 3) In this example, a sponge-like member is provided as the developer blow-out prevention member 21 instead of the plate-like member shown in FIGS. 1 and 2. By using such a sponge-like member 2゛C.1, it is possible to reduce not only the flow direction but also the flow velocity of the air containing toner, and the developer can be collected into the developing sleeve more efficiently. is possible.

Further, by using the developer blowout prevention member as a resin material having frictional charging polarity that is the same as that of the developer, it is possible to electrostatically repel the developer and further improve the blowout prevention effect.

Embodiment 4 (FIG. 4) In this example, a developer blow-out prevention member according to the present invention is applied to a developing device 4 of a type in which a developing sleeve 10 is rotated in a counter direction with respect to the rotating direction of a photosensitive drum 1 serving as an image carrier. This is an example in which 21 is provided.

C. Effects of the Invention As described above, according to the present invention, it is possible to effectively prevent the developer from blowing out from the inside of the developer container to the outside, and the above-mentioned conventional problems caused by the developer blowing out can be solved. It will be resolved.

Furthermore, since a compact developing device can be configured, it is possible to make the electrophotographic device small and lightweight, which also has the advantage of providing an easy-to-use device for users. Further, the present invention is effective even in ordinary developing devices, and is particularly effective in developing devices in which toner is replenished by dropping toner into a developer container little by little.

Furthermore, the developer container can be made smaller and lighter, and can easily be made into a process cartridge. In particular, some process cartridges are used again when toner runs low by swinging the cartridge to drop the toner blocking the developer container onto the sleeve.

It also has the effect of preventing inconveniences such as toner blowing out from the cartridge and staining the user's clothes in such a case.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the main parts of the first embodiment of the developing device of the present invention;
Figures 2 to 4 are cross-sectional views of the second to fourth embodiments;
The figure is a schematic diagram of an example of an electrophotographic device, the rfS6 figure is an enlarged cross-sectional view of the developing device part, FIG. gS9 is a diagram explaining the cause of developer blowout that occurs when the partition member is removed, Figure 10 is a plan view of a copy with toner stains, and Figure 11 is a diagram showing the developer stirring member and developer blowout prevention magnet. FIG. 12 is a cross-sectional view of the developing device provided, and FIG. 12 is a plan view of a copy in a state where sushi-shaped toner stains have occurred. 1 is a photosensitive drum as an image carrier, 10 is a developing sleeve as a developer carrying member, 11 is a developer, 12 is a developer container, and 21 is a developer blow-out prevention member. Figure 1 Figure 5 Figure 6 Figure 9

Claims (5)

[Claims] (1) Form and hold the dry powder developer stored in the developer container as a developer layer on the surface of the developer carrying member, and continuously transport it out of the developer container, and convert the transported developer layer into an electrical latent image. The developer layer is applied to the surface of the carrier to develop the latent image, and the remaining developer layer that was not subjected to development is held as it is on the surface of the developer carrier and transported back into the developer container to develop the latent image. In a continuous developing device, the gap between the developer container wall and the surface of the developer carrying member on the side where the remaining developer layer that has not been subjected to development is carried back into the developer container. A developing device further comprising: a member for preventing developer from blowing out inside the container, the member projecting from the wall of the developer container toward the developer carrying member. (2) According to claim (1), the length of the developer layer prevention member is approximately the same as the width dimension of the developer carrying member, or at least longer than the maximum width of the recording material used. The developing device described. (3) The developer is a one-component magnetic developer, and the developer blowout prevention member is a non-magnetic material.
Developing device described in section 2) (4) The developer carrying member has a magnet that adheres and holds the developer as a developer layer on the surface of the member using a magnetic field, and the opposing gap between the developer carrying member and the developer blowout prevention member is 2.
~3 mm, and the magnetic flux density within the opposing gap is 150 mm.
The developing device according to claim (1), which is Gauss or higher. (5) When the wall surface on the developer container side of the developer blow-out prevention member is the first wall surface, and the wall surface on the opposite side is the second wall surface,
The angle θ_E formed by the first wall surface and the developer container wall surface is 90° or less, and the angle θ_E between the first wall surface and the surface of the developer carrying member at the intersection of the extending surface and the developer carrying member surface is The angle on the developer container side formed by the extension surface of the second wall surface and the surface line of the developer carrying member at the intersection of the surface of the developer carrying member of the extension surface is defined as θ_A. Then, 180°>θ_B>45° and 180°>θ_A>45, respectively.
The developing device according to claim 1, wherein the developing device has an angular range of .degree.