JPS6175372A - Magnetic brush developing device - Google Patents

Abstract

PURPOSE:To obtain a developed image of invariably excellent picture quality stably for a long period by providing a hollow chamber where a magnetic carrier is charged previously. CONSTITUTION:The hollow chamber 7 where a constant amount of the magnetic carrier Ca is charged previously is formed on a front control plate 4, tufts height control plate 5, and partition plate 13, and this hollow chamber 7 is open to the outer peripheral surface of a developing sleeve 2 which is positioned at the upstream side of a development area A in a developer conveyance direction and above it. The constant amount of the magnetic carrier Ca is charged in this hollow chamber 7, but charged while mixed with a constant amount of insulating toner To. Consequently, the toner density of a magnetic developer is held constant and a developed image of invariably excellent picture quality is obtained for a long period.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention provides a magnetic carrier that is magnetically attracted to the outer peripheral surface of a developing sleeve by supplying toner stored in a toner replenishing tank. The present invention relates to a magnetic brush developing device in which a magnetic developer consisting of a mixture of magnetic carrier and toner is prepared on the outer circumferential surface of the developing sleeve, and an electrostatic latent image is developed using this magnetic developer. Photographer, etc. (This can be incorporated and used.

BACKGROUND OF THE INVENTION In recent years, as one of the above-mentioned magnetic brush developing devices, a developing sleeve is formed so as to open toward the outer circumferential surface of a developing sleeve located one spot upstream of the developing area in the direction of agent conveyance. The present applicant has developed a device (Japanese Patent Application No. 183633/1983) which is provided with a carrier loading chamber into which a certain amount of magnetic carrier is loaded in advance.

It has been experienced that, depending on the type of magnetic carrier used, development conditions, etc., a small amount of the magnetic carrier may adhere to the surface of the electrostatic latent image carrier and be consumed. When an electrostatic latent image equivalent to tens of thousands of sheets of A4 size paper is repeatedly developed using the magnetic brush developing device based on this black-like development, the amount of magnetic developer prepared on the outer circumferential surface of the developing sleeve increases. It has also been experienced that the toner density increases and the image quality of the developed image deteriorates, such as fogging occurring in the developed image.

Means for Solving the Problems An object of the present invention is to provide a magnetic brush developing device that can always obtain developed images of good quality even if the magnetic carrier is consumed as described above. .

[7] In order to achieve this object, the magnetic brush developing device according to the present invention is opened toward the outer circumferential surface of the developing sleeve located upstream of the developing region in the developer conveying direction,
In addition to having a carrier loading cavity in which magnetic carriers are loaded in advance, the present invention is characterized in that it further includes means for replenishing the magnetic carrier into the carrier loading cavity.

Function: In the magnetic brush developing device f according to the present invention, when the magnetic carrier is consumed under the action of the means for replenishing the magnetic carrier into the carrier loading cavity, the amount corresponding to the consumption is Since new magnetic carrier is substantially replenished into the carrier loading cavity, the toner concentration of the magnetic developer prepared on the outer peripheral surface of the developing sleeve always maintains a constant value. Therefore, even if the magnetic carrier is consumed, damage such as fogging in the developed image, which deteriorates the image quality of the developed image, can be prevented.

Embodiment FIG. 1 shows an embodiment of a magnetic brush developing device according to the present invention, which is shown installed in a powder image transfer type electrophotographic copying machine.

In FIG. 1, a magnetic brush developing device (MD) applies an electrophotographic photosensitive drum (1) to the surface of an electrophotographic photosensitive drum (1) which is rotated in the direction of arrow fa) while carrying an electrostatic latent image to be developed on the surface. The development area (Al) is provided so that the outer circumferential surface of the development sleeve (2) faces the surface of the photoreceptor drum (1) with a small gap maintained. (2) is made of a conductive non-magnetic material formed into a cylindrical shape, and has a magnetic roller (3) on the outer periphery of which S and N poles are sequentially magnetized.

Here, the developing sleeve (2) can rotate in the direction of arrow (b), while the magnetic roller (3) can rotate once in the direction of arrow fc1, and both are rotationally driven in each direction during development. The magnetic developer (De) is conveyed along the outer peripheral surface of the sleeve (2) in the direction of the arrow [b1]. Note that such conveyance of the magnetic developer (De) during development is carried out by the developing sleeve (2) or the magnetic roller (3).
) may be performed by rotationally driving either one of them, or if both are rotationally driven at the same time,
The direction of rotation can also be set arbitrarily. However, when such conveyance of the magnetic developer (De) is performed mainly by rotationally driving the developing sleeve (2), it is desirable that minute irregularities are formed on the outer circumferential surface of the developing sleeve (2).

By the way, the magnetic developer (De) is a developing sleeve (
2) Magnetic carrier (C
In contrast to a), m is produced on the outer peripheral surface of the developing sleeve (2) by supplying insulating toner (TO) stored in the toner supply tank (8), and a mixture of both. It consists of Note that the magnetic carrier (
As Ca), it is possible to arbitrarily use one consisting of 11 pieces of magnetic material such as ferrite, one coated with resin, or a so-called binder type magnetic carrier.

Further, as the insulating toner (TO), any one of non-magnetic toner and magnetic toner can be used. However, when using non-magnetic toner, the toner concentration of the magnetic developer (De) needs to be set lower than when using magnetic toner.

On the other hand, on the outer circumferential surface of the developing sleeve (2) located upstream of the developing area fA+ in the developer conveying direction, that is, in the arrow middle) direction, a front regulating plate (4) and a height regulating plate are arranged along the developer conveying direction. (5) etc. are installed facing each other.

The front regulating plate (4) at the top is attached to the arrow part of the toner replenishment tank (8), and the lower tip is aligned along the outer circumferential surface of the developing sleeve (2). A gap greater than the thickness of the magnetic developer (De) being conveyed is maintained, and it also functions as a partition plate that partitions the inside of the toner replenishing tank (8) into a developing section and a toner storage section. In addition, a toner supply passage (6) is formed between the lower horizontal portion of the front regulating plate (4) and the bottom of the toner supply tank (8). This toner supply passage (6) is in a state of conducting the toner storage section and the outer circumferential surface of the developing sleeve (2), and a supply regulating plate (9) is installed on the entrance side thereof. Further, the height regulating plate (5) is formed integrally with the inclined upper surface portion of the toner supply tank (8).

A carrier loading empty space (in which a certain amount of magnetic carrier (Ca) is loaded in advance) is formed by a front regulation plate (4), a height regulation plate (5), and a partition plate (13) (to be described later). 7
) is formed, and this empty space () is opened toward the outer circumferential surface of the developing sleeve (2) located on the upper upstream side of the developing area (A+) in the developer conveyance direction. , a certain amount of magnetic carrier (
At that time, the magnetic carrier (Ca) is not loaded alone, but is mixed with a certain amount of insulating toner (To).
) is preferably loaded. In order to make it possible to load the magnetic carrier (Ca) into such a vacant chamber (7),
An opening (11) for loading a magnetic carrier is provided in the upper surface of the toner replenishing tank (8) located above the empty chamber (7), and this opening (11) has a cover (11) that can be opened and closed. I2
) is covered. In addition, when loading the magnetic carrier (Ca) into the empty chamber (7), it is desirable for the loading operation that the partition plate (13) described later be removed by a negative number.

The upper part of the vacant room (7) is made of earth, and the partition plate (13
) is formed to form a supply carrier storage chamber (17), and this supply carrier storage chamber (17) is electrically connected to the mJ space (17) through a magnetic key. This supply carrier storage chamber (17) has an empty chamber (7) for carrier loading.
) When the magnetic carrier (Ca) is loaded in the empty space () and the initial setting of the magnetic brush developing device (MD) is completed, the magnetic carrier (Ca) to be replenished in the vacant space ( Alternatively, the magnetic carrier (Ca) is loaded in a mixed state with the insulating toner (To) and is loaded in the empty chamber (7).
is consumed, the amount of magnetic carrier (Ca) corresponding to the amount consumed is its own weight [therefore, the supply carrier storage chamber (1
7), the carrier passes through the opening and is sequentially replenished into the empty space for carrier loading.

Note that at this point, when the initial setting of the magnetic brush developing device (MD) is completed, the carrier loading empty chamber (7) is filled with the magnetic developer (De), and the supply carrier storage chamber (7) is filled with the magnetic developer (De). The magnetic carrier (Ca) in 17) is not replenished into the empty chamber (7) for carrier loading, and is not replenished into the empty chamber (7) for carrier loading as the magnetic carrier (Ca) is consumed. Only when a space corresponding to a flea of consumed magnetic carrier (Ca) is generated, magnetic carrier (Ca) is replenished to fill the space.

On the other hand, the exit side of the toner supply passage (6), that is, the left side in FIG. 1, is in a state facing the outer circumferential surface of the developing sleeve (2). Therefore, the insulating toner (To) stored in the toner storage portion of the toner supply tank (8) is magnetically attracted onto the outer peripheral surface of the developing sleeve (2) through this toner supply passage (6). The magnetic developer (De) is supplied to the magnetic carrier (Ga). The insulating toner ('1''O>) stored in the toner storage portion of the toner supply tank (8) is stirred and the insulating toner (-r○) is transferred to the toner supply passage ( A toner delivery blade (10) that is rotatably driven in the direction of arrow id) is provided in order to send the toner to the outer circumferential surface side of the developing sleeve (2) through the developing area (10). In order to prevent the IC from leaking out of the magnetic developer (De) to the outside of the magnetic brush developing device (MD), there is a , developer leakage prevention plate (1) made of magnetic material
4) and (15) are also provided.

By the way, the magnetic brush developing device (
MD) When trying to develop an electrostatic latent image from I,
j As a preparation step, first open the cover (12) and remove the partition plate (13) to open the empty space (7) for carrier loading.
) After the magnetic carrier (Ca) is loaded and the developing sleeve (2) and magnetic roller (3) are pre-rotated, the insulating toner (To) is loaded into the toner storage section of the toner supply tank (8). In this state, the developing sleeve (2) and the magnetic roller (3) are loaded with the magnetic carrier (Ca) into the developing sleeve (2) and the magnetic roller (3) until the electrostatic latent image has been developed to some extent. It is also possible to do so at a later point in time.

During development, as the developing sleeve +21 is rotated in the direction of the arrow (in the middle) and the magnetic roller (3) is rotated in the direction of the arrow (C1), the toner passes through the toner supply passage (6) and returns to the developing sleeve (2). The insulating toner (To) is supplied at a constant mixing ratio to the magnetic developer (De) which is magnetically adsorbed on the outer peripheral surface of the magnetic developer (D).
The developing sleeve (2) is transported along the outer peripheral surface of the developing sleeve (2) in the direction of the arrow (in the middle), and when passing through the empty chamber (7), it is mixed and stirred with the ζ magnetic carrier (,Ca,), and both As a result of this mixing and stirring, the insulating toner (To) and magnetic carrier (Ca), which are each component of the magnetic developer (De), are integrated at this point, and the developing area (In Al, a magnetic brush made of magnetic developer (De) is reliably formed. The magnetic brush formed here rubs the surface of the photoreceptor drum (1) and is supported on the surface. The electrostatic latent image is developed and visualized.

At this time, although it is common that the electrostatic latent image is developed while a DC developing bias is applied to the developing sleeve (2), it is also possible to apply an AC developing bias to the developing sleeve (2). Alternatively, the developing sleeve (2) may be grounded.

Further, after being subjected to development, the magnetic developer (De) remaining on the circumferential surface of the developing sleeve (2) is further transported in the direction of the arrow (b1), and when passing through the exit side of the toner supply passage (6),
After being replenished with this insulating toner (To), it is used again for development. In addition, when developing an electrostatic latent image, the magnetic carrier (Ca) in the magnetic developer (De) is consumed,
゛When the amount of magnetic carrier (Ca) in the empty chamber (7) for carrier loading is reduced (in this case, the magnetic carrier (Ca) stored in the replenishment carrier storage chamber (17) is The magnetic carrier (Ca) passes through the opening (16) and falls into the empty chamber (7) under its own weight and is automatically replenished, and the amount of magnetic carrier (Ca) in the empty chamber (7) is constantly maintained at a constant level. In other words, even if the magnetic carrier (Ca) is consumed, the absolute amount of magnetic carrier (Ca) present in the empty space (inside the space) and the magnetic adsorption on the outer circumferential surface of the developing sleeve (2) will be reduced. Magnetic carrier (
The absolute amount of Ca) is constantly maintained at a constant level.

By the way, the amount of magnetic developer (De) that reaches the developing area (~) is regulated by the height regulating plate (5), which is formed between the front regulating plate (4) and the developing sleeve (2). Front regulation gap or height regulation plate (5) and developing sleeve (2)
), the magnetic carrier (Ca) present on the outer peripheral surface of the developing sleeve (2) all passes through the pre-regulating gap and enters the vacant chamber (7). ). Here, the magnetic carrier (Ca) regulated by the height regulating plate (5) and the insulating toner ('r
o) refers to the developing sleeve (2) that accumulates in the empty chamber (7).
Perhaps they are also mixed and stirred in the axial direction of the magnetic carrier (Ca), and the magnetic carrier (Ca) is stirred only in the empty chamber (7).
There is no ○ that is diffused into the insulating toner ('l''O) stored in the toner storage section of the toner supply tank (8). Developer (De3 toner concentration is within empty chamber (7)
c Depends on the amount of magnetic carrier (Ca) retained. Therefore, the toner concentration of the magnetic developer 11 (De) in the development area fA) will maintain a constant value corresponding to the concentration of the magnetic carrier (Ca), and this toner concentration will be
) (This can be adjusted by adjusting the poison of the magnetic carrier (Ca) loaded in advance, and when it becomes too large, the toner concentration tends to increase.

For this reason, it is desirable to adjust the toner concentration while also considering the volume of the empty chamber (7). Preferably, when the initial setting of the magnetic brush development device (MD) is completed, the vacant chamber (7) is completely filled with the magnetic developer (g! agent (De), and in this state, the magnetic development area + AI is It is necessary to appropriately set the volume of the empty chamber (7) so that the toner concentration of the developer (De) reaches a desired value.

In addition, in the above configuration, the pre-regulating gap holds the magnetic developer (
In addition to being large enough to pass through all of De), the front regulating plate (4) separates the empty chamber (7) from the toner storage section of the toner replenishing tank (8). It must be able to prevent the accumulation of magnetic carriers (Ca) from diffusing. For example, if the front regulation gap is narrow and the amount of magnetic developer (De) passing through is smaller than the brush height regulation gap, the magnetic carrier (Ca
) accumulates and passes through the toner supply path (6) and diffuses into the magnetic carrier (Ca) or the toner storage portion of the toner supply tank (8). On the other hand, magnetic carrier (Ca
) or accumulated in the vacant room (7) (thus,
When the magnetic developer (De) passes through the empty chamber (7), the insulating toner (TO) and the magnetic carrier (Ca) are sufficiently triboelectrically charged, and the magnetic developer (De) in the axial direction of the developing sleeve (2) ) is also effectively eliminated.

[Experiment example]

Regarding the magnetic brush developing device (MD) shown in FIG. 1, excellent effects have already been reported based on various experimental results. Here, among the experiments conducted by the present inventor, representative ones are shown below, and the above-mentioned excellent effects are specifically clarified as follows.

Experimental example - ■ Concerning the magnetic brush developing device (MD) shown in Fig. 1, Magnetic roller Magnetic crab 750G Number of poles: 6 poles Rotation speed: 9oOrpm (direction of arrow C) Phenomenon sleeve
Outer diameter: 245 Rotation speed: 8 orpm (in the direction of the arrow) Process speed (photosensitive drum circumferential speed): l 30F1
1N/sec Brush height regulation gap: o, 3sym Pre regulation gap; 12 gate development gap; 0.45 Homomagnetic carrier; 100 parts by weight of styrene/acrylic resin, magnetite 2
00 parts by weight, carbon black double M parts, silica 1.5
Binder-type magnetic carrier insulating toner with an average particle size of 40 μm obtained by heating, kneading, cooling, pulverizing, and classifying parts by weight; polyester resin (weight average molecular weight: 23,300) 1
00 parts by weight, 30 parts by weight of magnetite, 2 parts by weight of negatively charged dye
Parts by weight of carbon black, 4 parts by weight of wax, and 2.5 parts by weight of wax are heated, kneaded, cooled, pulverized, and classified. (however, 70 g of a 7:3 mixture of magnetic carrier: insulating toner); 15 g of magnetic carrier loaded in the supply carrier storage chamber (17) (however, 7:3 of magnetic carrier: insulating toner) (mixture of 15g) Toner replenishment h'ff Amount of insulating toner loaded into the toner storage section in +8+; 100g (however, supplemented sequentially)
Capacity of empty chamber (7); 112 d photoreceptor in terms of cross-sectional area in Figure 1; Se-based photoreceptor electrostatic latent image potential; +500V (highest potential) development bias;
A copying experiment was carried out using a powder image transfer type electrophotographic copying machine under the following conditions: DC +150V AC 400Vrm3 400f-1z. This result shows that until 50,000 copies of A4 size sheets were completed, good quality copies were consistently obtained. Furthermore, when the copying of 50,000 sheets is completed, the magnetic carrier (
When we observed the amount of Ca), it decreased from 15g at the time of loading to 9g, and from this, 6g of magnetic carrier (Ca) was found in the empty chamber (7) during the copying experiment.
It was also confirmed that supplies were being supplied to the interior.

On the other hand, during the copying experiment, the toner concentration of the magnetic developer (De) in the development area fAl was also observed, and it was found that the toner concentration was always maintained at a value of 3Qwt%. In addition, at the time when the initial settings of the magnetic brush developing device (M D ) are completed prior to starting the copying experiment, the vacant chamber (7) is completely filled with the magnetic developer ('De) with a toner concentration of 30 wt%. , and a magnetic developer (
The toner concentration of De) was also 30wtX.

Experimental Example-2 The shape of the partition plate (13) shown in Fig. 1 was changed to the partition plates (23) and (33) shown in Figs. 2 and 3,
When a copying experiment similar to Experimental Example-1 was conducted, Experimental Example-
Almost the same good results as in Example 1 were obtained. However, due to the use of partition plates (23) and (33) having such shapes, free space (
18) is formed, and the mixing and agitation of the insulating toner (To) and the magnetic carrier (Ca) in the empty chamber (7) becomes smoother, resulting in an improvement in the triboelectric charging property of the insulating toner (To). It was seen.

Regarding Experimental Example 2, the copying experiment was conducted with the capacity of the vacant room (7) expanded by an amount corresponding to the free space (18).

Experimental example-3 The partition plate (13) shown in Fig. 1 was replaced with the partition plate (13) shown in Fig. 4.
Replaced with two partition plates (,13) and (53), Experimental example-1
When a copying experiment similar to the above was conducted, good results substantially similar to Experimental Example 1 were obtained. As a concrete experimental result, m
= Isn't there two partition plates like this (・+3),
The adoption of (53) is considered to be effective in preventing the magnetic developer (+) e) from entering into the replenishment carrier storage chamber (17), and is therefore effective in implementing the present invention (in this case, , second
, the partition plate (23) shown in Figure 3.

(33) Or these two partition plates (・43)i(
53) is considered desirable.

Comparative Experimental Example-1 A copying experiment similar to Experimental Example-14 was conducted by removing the partition plate (13) shown in FIG. 1 and omitting the loading of the magnetic carrier (Ca) into the supply carrier storage chamber. This result is
It was observed that fogging occurred in the copied images from around the time when 10,000 copies were completed, and that the image quality, sharpness, uniformity of halftone reproducibility, etc. gradually deteriorated.

This is because as the magnetic carrier (Ca) is consumed and its absolute amount decreases, the toner concentration of the magnetic developer (De) in the development area fA+ gradually reaches the aforementioned toner concentration of 40 wt%. It was rising.

Effects of the Invention Depending on the type of magnetic carrier used and/or the surface condition of the electrostatic latent image carrier carrying the electrostatic latent image to be developed, the magnetic brush developing device according to the present invention may Even if the phenomenon of toner adhering to the surface of the electrostatic latent image carrier and being consumed occurs, the toner concentration of the magnetic developer prepared on the outer peripheral surface of the developing sleeve maintains a constant value, and as a result, the toner concentration always remains constant. Developed images of good quality can be stably obtained over a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing one embodiment of a magnetic brush developing device according to the present invention, and FIGS. 2 to 4 are drawings showing modifications of essential parts of the above embodiment. \fl) -Magnetic development device 1)e...Magnetic developer Ca -Magnetic carrier TO...Toner,
~ -Representation area ゛)...Developing sleeve; 3
・・Magnetic roller 7・・Empty room for carrier loading 8
- Toner supply tank 13, 23, 33, 43.53 - Partition plate 115 - Opening 17 for carrier supply - Supply carrier storage chamber

Claims (1)

[Scope of Claims] 1. By supplying toner stored in a toner replenishment tank to the magnetic carrier magnetically attracted on the outer circumferential surface of the developing sleeve, A magnetic brush developing device that prepares a magnetic developer made of a mixture of a magnetic carrier and a toner, and develops an electrostatic latent image using this magnetic developer, the magnetic brush developing device having a development area upstream in the developer transport direction. It is formed to open toward the outer circumferential surface of the developing sleeve in which it is located, and includes a carrier loading cavity into which magnetic carrier is loaded in advance, and a means for replenishing the magnetic carrier into the carrier loading cavity. A magnetic brush developing device characterized by: 2. The magnetic brush developing device according to claim 1, wherein the empty chamber for loading the carrier is opened toward the outer peripheral surface of the developing sleeve located at the upper part. 3. The carrier replenishing means has a replenishment carrier storage chamber for storing magnetic carriers to be replenished, and the magnetic carriers stored in the replenishment carrier storage chamber are replenished into the empty chamber for carrier loading. A magnetic brush developing device according to claim 2, characterized in that: 4. The supply carrier storage chamber is located above the carrier loading cavity, is electrically connected to the carrier loading cavity through an opening through which the magnetic carrier can pass, and is stored in the supply carrier storage chamber. 4. The magnetic brush developing device according to claim 3, wherein the magnetic carrier is replenished into the carrier loading cavity by its own weight.