JPH03200983A - developing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] No. 1 The present invention relates to a developing device using a two-component developer having toner and a carrier, and particularly to a developing device that makes it possible to satisfactorily form a thin layer of toner on a developer carrier. It relates to a developing device.

藍朱桔1 A developing device using a two-component developer containing toner and carrier (magnetic particles) is known as shown in Japanese Patent Application Laid-Open No. 116240/1983.

In such a developing device, a two-component developer containing toner and a carrier is stirred by a stirring means, and the toner is triboelectrostatically charged.
The charged toner from the developer is attached to a conductive roller, carried on it, and conveyed to a development position between the image carrier and the conductive roller with a polarity opposite to that of the toner. A bias electric field is applied by a bias power source to attach toner to an electrostatic latent image formed on an image carrier,
The electrostatic latent image is visualized as a toner image.

However, in this type of developing device, if the toner concentration of the developer becomes higher than permissible, the amount of toner adhering to the conductive roller will be excessively large, causing image fogging and toner scattering. This causes the inconvenience of being stored away.

Another example of a developing device using a two-component developer includes a developing sleeve as a developer carrier with a built-in magnetic field generating means, and an image carrier that is in contact with the circumferential surface of the developing sleeve to regulate the carrier. A device is known in which an elastic blade is provided to apply toner to a predetermined thickness to be conveyed to a developing position, as disclosed in, for example, Japanese Patent Laid-Open No. 62-96956.

In this developing device, an elastic blade is brought into elastic contact with the developing sleeve, and the toner is agitated by circulating carrier near the blade, so that the toner is coated with a sufficient amount of so-called tribo. .

However, in order to circulate the carrier sufficiently, sufficient space is required, and the amount of carrier must also be kept small to obtain the tribo. The existence rate of carriers must be 10% or less. As a result, with such a small amount of carrier, the amount of toner conveyed is insufficient, and the toner cannot be sufficiently conveyed to the development position, resulting in a so-called ghost phenomenon.

In addition, in devices where the elastic blade itself is made of a magnetic material and uses magnetic force to regulate the carrier, an immobile layer of carrier is created near the blade, which prevents the circulation of the carrier and the supply of toner to the developing sleeve. However, there was a problem in that the image quality was insufficient, resulting in a ghost phenomenon.

Based on the above, it is possible to stabilize the thin layer of applied toner over a wide range of toner concentrations relative to the carrier of a two-component developer with a simple configuration that does not require toner concentration control IIIWJ. It is desired to develop a developing device that can easily produce high-density, high-quality images without fogging or toner scattering, and that can be made inexpensive and compact.

Therefore, an object of the present invention is to provide a developing device having the above characteristics.

・　゛　ruta　 The above object is achieved by a developing device according to the present invention.

To summarize, the present invention provides a developer carrier that supports a two-component developer having toner and a carrier and transports the developer while forming a magnetic brush of the developer, and a toner carrier disposed opposite to a region in which a magnetic brush of the developer is formed, the toner carrying member receives, carries, and conveys the toner in the developer by contacting with the magnetic brush of the developer; disposed at a downstream position in the toner transport direction of a portion facing the developer carrier;
The developing device further includes a toner regulating member that comes into contact with the developer magnetic brush and regulates the amount of toner carried on the toner carrier.

According to one aspect of the present invention, the toner regulating member is made of an elastic blade, and the elastic blade is disposed to face in a direction opposite to the toner conveyance direction. According to another aspect of the present invention, a DC electric field or an AC electric field superimposed thereon is formed between the developer carrier and the toner carrier.

X type E Examples of the present invention will be described in detail below.

FIG. 1 is a schematic diagram showing an embodiment of the developing device of the present invention.

As shown in FIG. 1, the developing device of the present invention faces a developer carrying roller 1 as a developer carrying member that rotates in the incoming direction and is disposed in a developing container 7 containing a two-component developer 9. A toner carrying roller 6 as a toner carrying member that rotates in the direction B is provided, and an elastic blade 8 that comes into contact with the toner carrying roller 6 is provided.

The developer 9 is a mixture containing the toner 4 and the carrier 3 made of magnetic particles having a larger particle size. A doctor blade 5 that regulates the amount of developer 9 applied onto the roller 1 is arranged on the top of the developer carrying roller 1 with an interval from the roller 1. Inside the developer carrying roller l,
Magnet roller 2 as a magnetic field generating means is connected to roller 1
It is installed immovably against the rotation of. Magnet roller 2
has four magnetic poles of Nr, Sl, Na, and Si in the rotational direction of the roller 1 from the doctor blade 5.

The toner carrying roller 6 is arranged in an area on the 81 side of the magnet 2, which forms a magnetic brush for the developer 9 of the developer carrying member 1.
A photosensitive drum 1 serving as an image carrier is placed in contact with and facing the magnetic brush of the developer 9 on the developer carrying roller 1.
It is disposed at the opening of the developer container 7 facing the developer container 7.

The elastic blade 8 is provided at a portion of the toner carrying roller 6 facing the developer carrying roller 1 so as to be in contact with the magnetic brush of the developer 9 formed on the developer carrying roller l, and is It is in contact with the downstream side in the toner conveyance direction (rotation direction of the roller 6), inclined from above toward the counter. The elastic blade 8 is deformed as shown in the figure by the pressure applied to the toner carrier roller 6, and the blade 8 is deformed as shown in the figure.
The tip of the roller 6 is urged to contact the roller 6.

Next, the operation of the present developing device will be explained.

The developer 9 accommodated in the developer container 7 forms a circulating flow C by the action of the rotational force of the developer carrying roller 1, the magnetic force of the magnet roller 2, and gravity, and the carriers in the developer 9 are formed by this circulating flow C. 3 and toner 4 are mixed and stirred,
Furthermore, an electric charge is applied to the toner 4 by frictional charging.

On the other hand, the developer 9 carried on the developer carrying roller 1 is
The coating amount is determined by the doctor blade 5, and the developer 9
A certain amount of the developer is applied onto the roller l, and the remainder is returned to the developer container 7 and incorporated into the circulating flow C of the developer l.

In this embodiment, the doctor blade 5 and the developer carrying roller l are
The gap between the two is set to 800LLm, and the magnetic pole N1 of the magnet roller 2 facing the doctor blade 5 is positioned at an angle θ upstream of the blade 5 in the rotational direction of the roller l.
It is located on a slight slope. Thereby, the circulating flow C of the developer 9 can be smoothly formed.

The developer 9 coated on the developer carrying roller 1 is conveyed by the roller l to a portion facing the toner carrying roller 6. A magnetic pole S1 of the magnet roller 2 is arranged in a portion facing the toner carrying roller 6, and the developer 9 forms a magnetic brush by the action of the magnetic pole S1 and slides over the surface of the roller 6. Rub. During this rubbing, a portion of the toner 4 in the developer 9 is applied to the surface of the toner carrying roller 6. In this case, the toner 4 adheres to the surface of the toner carrier roller 6 mainly due to the reflection force of the charged toner 4.

The gap between the developer carrying roller 1 and the toner carrying roller 6 must be set with care so that the developer 9 does not accumulate too much therebetween, and is set to 700 μm in this embodiment.

The amount of toner 4 transferred from the developer carrying roller l to the toner carrying roller 6 largely depends on the concentration of toner 4 in the developer 9. When the toner concentration is high, the amount transferred is large, and when the toner concentration is low, the amount transferred is small. becomes less. If the amount of toner transferred and applied to the toner carrying roller 6 is too large, it may cause image fogging or toner scattering, and if it is too small, a sufficient image density may not be obtained. Therefore, it is necessary to always control the amount of toner 4 applied to the toner carrying roller 6 to be constant.

Therefore, the tip of the elastic blade 8 is brought into contact with the toner carrying roller 6 as described above. By doing so, excess toner applied to the toner carrying roller 6 is scraped off, and only an appropriate amount of toner 4 is allowed to pass through.

At this time, the toner concentration of the developer 9 carried on the developer carrying roller 1 is made relatively high, and the roller l
By constantly increasing the amount of toner 4 supplied to the toner carrying roller 6 and removing excess toner and carrier by the elastic blade 8, a constant amount of toner 4 is always kept on the toner carrying roller 6. Toner 4 can be applied,
There is no possibility that the density of the image will be low due to a decrease in the amount of toner applied.

Next, stabilization of toner application by the elastic blade 8 will be described in more detail.

FIG. 2 is a schematic diagram showing a contact portion of the elastic blade 8 that contacts the toner carrying roller 6. As shown in FIG.

The magnetic brush of the developer 1 formed on the developer carrying roller l rubs against the toner carrying roller 6 to transfer and apply the toner 4 to the roller 6. Then, a portion of the applied toner 4 and carrier 3 are adhered by frictional force or electrostatic force, and are carried to the contact portion with the elastic blade 8 by the rotation of the roller 6.

At this contact portion, the relatively strongly charged toner 4 out of the applied toner 4 has a strong adhesion force to the toner carrying roller 6, so it resists the elastic blade 8 and fills the gap at the contact portion. However, the toner 4 with a weak charge is scraped off, and the carrier 3 with a large particle size cannot pass through the gap and is similarly scraped off.

In this way, a thin layer of the toner 4 coated with an appropriate amount can be formed on the surface of the toner carrying roller 6 after passing through the contact portion of the elastic blade 8 .

At the contact portion of the elastic blade 8, excess toner is scraped off, so when supplying the toner 4 from the developer carrying roller l to the toner carrying roller 6, as described above, the amount of toner 4 supplied must be at least an appropriate amount. Bye. According to experiments conducted by the inventors, the T/T of the developer 9 carried on the developer carrying roller l
It has been found that a sufficient amount of toner can be supplied if the C ratio (weight ratio of toner 4 and carrier 3) is 12% or more.

The T/C ratio of the developer 9 carried on the developer carrying roller 1 may be any value as long as it is 12% or more, but it is important that the toner is sufficiently charged and the developer 9 is circulated within the developer container 7. In order to perform this process smoothly, it is preferable to set it to 40% or less.

The toner and carrier scraped off by the contact portion of the elastic blade 8 are magnetically removed by arranging the contact portion at a position where it comes into contact with the magnetic brush of the developer 9 formed by the developer carrying roller 1. It is swept away by the brush and returned to the developer container 7 as the magnetic brush moves. This results in
Since the toner 3 and carrier 4 do not stay in the contact area of the elastic blade 8, the toner 3 may be fused to the elastic blade 8, and the carrier may not accumulate between the toner carrying roller 6 and the elastic blade 8. The inconvenience of streaks occurring due to 4 being caught does not occur.

Further, in this configuration, the magnetic brush formed on the developer carrying roller l constantly rubs the surface of the toner carrying roller 6 on which the toner 4 is applied, and scrapes the thin layer of toner 4 on the roller 6. By disturbing and appropriately scraping, the toner 4 is replaced, so that the toner 4 is not excessively charged and can maintain a certain amount of charge on the toner 4.

For details on how to set the elastic blade 8, refer to the elastic blade 8
There are two types: a type in which the ridge at the corner of the tip end is brought into pressure contact with the toner carrying roller 6, and a type in which the abdomen at the end part is brought into pressure contact with the toner carrying roller 6. In the former case, as shown in FIG. 3, if the elastic blade 8 is set too high relative to the toner carrying roller 6,
In the latter case, as shown in FIG. 4, if the tip of the elastic blade 8 rises too far from the toner carrying roller 6, the carrier 3 is removed in the lifted area 11. It becomes easy to get clogged and cause uneven coating. Therefore, it is necessary to urge the tip of the elastic blade 8, that is, the tip and the vicinity thereof, so as to come into contact with the toner carrying roller 6.

FIG. 5 is an explanatory diagram illustrating the amount of penetration of the elastic blade 8.

In FIG. 5, the dotted line indicates the position of the tip of the elastic blade 8 assuming that the toner carrying roller 6 is not present, and the solid line indicates the actual position of the elastic blade 8 when the toner carrying roller 6 is present. It shows.

The amount of penetration of the elastic roller 8 into the toner carrying roller 6 d() The intersection point P between the elastic blade 8 and the toner carrying roller 6 and the toner carrying at the tip of the elastic blade 8 assuming that the toner carrying roller 6 does not exist. The length between the corner Q on the roller 6 side) is 0.5 to 2 mm in order to urge the tip of the elastic blade 8 (the tip and its vicinity) to come into contact with the toner carrying roller 6. is preferred.

As for the material of the elastic blade 8, it is preferable to use a material that can regulate the carrier 3 and also impart a charge of a desired polarity to the toner 4 through friction when it comes into contact with the toner 4.

Although it depends on the material of the toner, for example, in order to positively charge a toner whose main component is polystyrene, ethylene propylene, fluororubber, natural rubber, polychlorobudiene, N, B, R, etc. are effective. . On the other hand, silicone rubber, polyurethane, styrene-butadiene rubber, etc. are effective for negatively charging.

Note that the hardness of the rubber described above is preferably 50 to 70 degrees in terms of JISA hardness. If it is 70' or more in JISA, the elasticity of the rubber is strong and the pressure at the contact part becomes too high, and the thin layer of toner 4 formed on the toner carrying roller 6 becomes excessively thin, making it difficult to obtain a sufficient image. This means that the concentration of . On the other hand, if it is less than 50', the elasticity of the rubber itself is weak and it becomes difficult to obtain sufficient pressure to keep the contact portion in place.

As the carrier 3 used in this example, conventionally known ferromagnetic or paramagnetic particles can be used, such as metal particles of iron, chromium, nickel, cobalt, etc., triiron tetroxide, gamma ferric oxide, etc. Metal oxides such as iron, chromium dioxide, manganese oxide, and ferrite, alloys such as manganese and copper alloys, resin carriers in which the above magnetic particles are dispersed in resin materials, and coated carriers in which the above magnetic particles are coated with resin materials. Can be used. Further, since the carrier 3 is not applied to the surface of the toner carrying roller 6, it is possible to use either a conductive carrier or an insulating carrier.

Regarding the particle size of the carrier 3 and toner 4, in order to reliably regulate the carrier 3 by the above-mentioned elastic blade 8, the particle size of the toner 4 is 1 to 20 μm, and the particle size of the carrier 3 is in the range of 40 to 200 μm. It is preferable that there be. If the particle size of the carrier 3 is less than 40 μm, it will be difficult to control the carrier 3 by the elastic blade 8, and if it exceeds 200 μm, the ability to hold the toner 4 on the toner carrying roller 6 will be significantly reduced.

Furthermore, rather than making the surfaces of the developer carrying roller l and the toner carrying roller 6 mirror-finished, it is preferable to add minute irregularities to the surface in order to uniformly apply the toner 4. Furthermore, in order to control the charge imparting ability, it is preferable to add minute irregularities to the surfaces. Alternatively, a resin or a resin in which conductive particles such as carbon are dispersed may be applied.

FIG. 6 is a schematic diagram showing another embodiment of the developing device of the present invention.

The developing device of this embodiment is characterized in that a bias power supply 12 is provided between the developer carrying roller l and the toner carrying roller 6 for forming a direct current electric field or an alternating current electric field superimposed thereon. be. The other structure of the developing device of this embodiment is basically the same as that shown in FIG. 1, and the same reference numerals in FIG. 6 as in FIG. 1 indicate the same members.

The above DC electric field or an AC electric field superimposed on it is:
The toner is applied in a direction to transfer the toner from the developer carrying roller 1 to the toner carrying roller 6.

In this embodiment, when negatively charged toner is used, a DC power supply is used as the bias power supply 12 and an electric field of -300 V DC is applied to supply sufficient toner from the developer carrying roller l to the toner carrying roller 6. were able to supply it.

In addition, an AC power source is used as the bias power source 12, and the frequency is 100.
0Ht, peak-to-peak voltage 1000. By applying an electric field in which a DC voltage of 1,300 V was superimposed on an AC voltage of V, it was possible to similarly supply sufficient toner from the developer carrying roller 1 to the toner carrying roller 6.

As described above, in this embodiment, since the toner is forcibly transferred from the developer carrying roller 1 to the toner carrying roller 6 using an electric field, the toner supply capacity is increased and the toner is carried on the developer carrying roller 1. Even for a developer having a T/C of 6% or more, sufficient toner can be supplied to the toner carrying roller 6.

FIG. 7 is a schematic diagram showing still another embodiment of the developing device of the present invention.

The developing device of this embodiment has an equipolar arrangement (
In this embodiment, a magnetic roller 13 with an 8-pole equipolar arrangement is used, and the magnetic roller 13 is rotated in a direction opposite to that of the developer carrying roller 1. It is basically the same as the developing device shown in the figure, and the same reference numerals in FIG. 7 as in FIG. 1 indicate the same members.

As described above, by arranging the equipolar magnet roller 13 within the developer carrying roller l and rotating it in the opposite direction to the developer carrying roller 1, the developer carried on the developer carrying roller 1 is This increases the amount of contact between the magnetic brush of the developer and the toner carrying roller 6, thereby increasing the supply of toner from the developer carrying roller l to the toner carrying roller 6. ability can be increased.

According to this embodiment, since the conveyance speed of the developer is increased, the toner and carrier are well mixed, and the magnetic brush of the developer smoothly rubs on the toner carrying roller 6, so that the toner carrying roller 6 can be smoothly mixed. Since the toner applied on the toner 6 is frequently replaced with the newly supplied toner, the toner can be applied with a more stable charge amount.

The same effect can be obtained even when the magnet roller 2 is installed immovably inside the developer carrying roller l, as in the developing device shown in FIG. 1 and the developing device shown in FIG. This can be achieved by increasing the rotational speed of the carrier roller 1.

As explained above, in the developing device of the present invention, the toner carrier is disposed opposite to the developer carrier carrying and conveying the two-component developer, and the toner carrier is placed on the developer carrier. By bringing the toner carrier into contact with the magnetic brush of the formed developer, the toner in the developer is applied onto the toner carrier,
Since the toner regulating member is brought into contact with the toner carrier to regulate the amount of toner applied on the toner carrier, it is possible to control the developer carrier with a simple configuration that does not require a toner concentration control mechanism. A thin layer of applied toner can be stably obtained over a wide range of toner concentrations. Therefore, high-density, high-quality images without fogging or toner scattering can always be obtained, and the developing device can also be made inexpensive and compact.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the developing device of the present invention. FIG. 2 is a schematic diagram showing the contact portion of the elastic blade that contacts the toner carrying roller in the developing device shown in FIG. 1. FIG. FIGS. 3 and 4 are explanatory diagrams showing the manner in which the elastic blades of FIG. 2 come into contact, respectively. FIG. 5 is an explanatory diagram showing the amount of penetration of the elastic blade shown in FIG. 2 into the toner carrying roller. FIG. 6 is a schematic diagram showing another embodiment of the developing device of the present invention. FIG. 7 is a schematic diagram showing still another embodiment of the developing device of the present invention. l: Developer carrying roller 13: Magnet roller: Carrier: Toner: Doctor blade: Toner carrying roller: Elastic blade: Two-component developer 12: Bias power supply Figure 3 Figure 4 Figure 5

Claims (1)

[Scope of Claims] 1) A developer carrier that carries a two-component developer having toner and a carrier and transports the developer while forming a magnetic brush of the developer; disposed opposite to the area where the magnetic brush of the developer is formed;
A toner carrier that receives, carries, and transports the toner in the developer by contacting the magnetic brush of the developer, and a downstream portion of the toner carrier in the direction in which the toner is transported, at a portion of the toner carrier that faces the developer carrier. A developing device comprising: a toner regulating member disposed at a position that contacts the developer magnetic brush and regulates the amount of toner carried on the toner carrier. 2) The developing device according to claim 1, wherein the toner regulating member is made of an elastic blade, and the elastic blade is disposed facing in a direction opposite to a direction in which the toner is conveyed. 3) A direct current electric field or an alternating current electric field superimposed thereon is formed between the developer carrier and the toner carrier.
Or the developing device described in 2.