JPS63179374A - Developing device - Google Patents

Abstract

PURPOSE:To stably supply and collect toner by a simple constitution and to form an image with invariably constant density by arranging plural toner cartridges which contain toner supply and recovery rollers opposite a developing sleeve at the periphery of the developing sleeve. CONSTITUTION:The housing 2 of a developing device 1 is formed of a frame body, opening parts 3 and 4 are formed at the front and rear parts, and the developing sleeve 5 is arranged at the front part of the housing 2. This sleeve 5 is set opposite a photosensitive drum 100 across a specific gap and rotated as shown by an arrow (a) and applied with a developing bias Vb. An empty room 8 is formed at the rear part of the napping control member 7 of the sleeve 5 above the sleeve 5 and the box-type casing 11 of a toner supply cartridge where plural toner supply and recovery rollers 12 are arranged is mounted in the empty room 8. Then toner is supplied to the surface of the sleeve 5 and also recovered, thereby performing the supply and recover of the toner by the simple constitution.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a developing device used in an image forming apparatus such as a copying machine.

(Prior Art) Conventionally, as one aspect of an image forming apparatus having an electrophotographic copying process, a plurality of developing devices are disposed around a photoreceptor drum, each containing a developer of a different color, and a plurality of developing devices are arranged around a photoreceptor drum. Multicolor copying machines and printers that can reproduce images in different colors have been proposed.

However, since various charge dryers, cleaning devices, erasers, etc. (iS) are arranged close to each other around the photoreceptor drum, in commonly used image forming apparatuses, the photoreceptor drum The number of developing devices that can be arranged around the device is also limited to two or three at most.

Therefore, if a large photoreceptor drum is used in order to achieve multiple colors, this will lead to an increase in the size of the image forming device, going against the recent trend of miniaturization and compactness. .

In view of this, in recent years, a developing device capable of realizing multiple colors and downsizing the device has been proposed in Japanese Patent Application Laid-Open No. 61-201271.

This developing device has a circular developing container rotatably disposed on the side of a developing sleeve that holds a magnetic carrier on its outer circumferential surface, and the inside of the developing container is divided in the circumferential direction into a plurality of toner-containing developing containers. A developer chamber is formed to accommodate toner of a different color in each chamber, and an opening formed on the outside of each developer chamber allows a toner supply/recovery roller to be driven to rotate, and a developer sleeve. They are provided so that they can face each other closely.

Then, in step B, the developer container is rotated so that the toner supply/recovery roller in the developer chamber containing toner of the designated color faces the developing sleeve, and the designated color is coated on the surface of the developing sleeve. When switching the toner to another color, first collect the toner held on the developing sleeve into the facing developer chamber, and then rotate the developer container. Toner of another color is supplied to the developing sleeve from a separate developer container.

(Problem to be Solved by the Invention) However, in a developing device in which toner is supplied from a toner supply/recovery roller to a carrier held in a developing sleeve, such as in a multiplex system, the developing sleeve and toner If the distance between the supply and collection rollers is not set accurately, the toner supply and collection mechanism cannot be performed properly, which leads to the problem that the developer container rotation mechanism and stop position control mechanism become complicated. have.

Further, when one developer chamber and the toner supply/collection roller face the developing sleeve, it is located below any one of the other rollers and the developer chamber. j,
Therefore, toner spills from the developer chamber or from the roller surface, and this spilled toner is supplied to the surface of the developer sleeve based on the rotation of the developer container, or is collected into a developer chamber containing toner of another color. However, there is a problem in that the reproduced image has mixed colors.

Furthermore, with this system, it is not possible to replenish toner sequentially from a hopper, etc., and to replenish toner, the developer container itself must be removed from the developing device, which makes replenishment operations complicated, and the toner can be removed from clothing or other objects. It has the problem that it adheres to the body and becomes dirty.

Furthermore, since switching the color involves rotating the developer container, there is a problem in that the switching operation cannot be performed instantaneously.

(Means for solving the problems) Since the present invention was made to solve the above problems,
A two-component developer is prepared by supplying toner to a magnetic carrier held on the outer peripheral surface of a developing sleeve, and an electrostatic latent image is formed on the surface of an electrostatic latent image carrier using the developer. In a developing device for developing a toner, a toner storage cartridge having a supply/collection roller that supplies toner to the surface of the developing sleeve and collects the supplied toner is provided, and the supply/collection roller is connected to the outer circumferential surface of the developing sleeve. A plurality of them are arranged facing each other.

(Example) Hereinafter, the present invention will be described with reference to the accompanying drawings which are one example thereof.

In FIG. 1, (1) is a developing device according to the present invention. (2) is a housing for the developing device (1), and the housing (2) is a box-shaped frame, with openings (3) and (4) formed in the front and rear parts, respectively.

(5) is a developing sleeve, which is disposed at the front of the housing (2) to face the photosensitive drum (+00) with a predetermined gap, and can be driven to rotate in the direction of arrow (a). , and a developing bias (Vb) is applied. Inside the developing sleeve (5), a plurality of magnets having magnetic poles arranged in the axial direction are disposed in the circumferential direction, and 72 magnetic rollers (6) are housed in a fixed state.

Further, on the upper and lower sides of the housing (2) sandwiching the opening (3), there are brush height regulating members (7) facing the developing sleeve (5),
A toner spill prevention plate (9) is formed, and a vacant chamber (8) is formed behind the height regulating member (7) and above the developing sleeve (5).

(10a), -, (I Od) are toner supply cartridges (hereinafter referred to as "cartridges"), and these have almost the same structure, with an opening formed in the front part of the box-shaped casing (11). A toner supply/collection roller (hereinafter referred to as "supply roller" X12) having four minute parts formed on its outer peripheral surface is arranged rotatably in the direction of arrow (b), and the supply roller (12) has a casing ( 11) and the toner return prevention film (14).
) or press contact.

A toner hopper (15) is formed at the rear of the casing (11), and the toner hopper (15) is provided with a conveying blade (+
6) and (17) are arranged rotatably in the directions of arrows (c) and (d), respectively.

Cartridges (10a) with the above configuration, ~, (1
0d) has a cartridge (
The casing (11) is stacked and housed with the tea (tea) on the top layer and the cartridge (10d) on the bottom layer.
On the side wall of the housing (2) and the inner surface of the housing (2) opposite thereto,
A guide member and a stopper (not shown) are formed respectively, and each cartridge (IOa), . A certain gap is ensured between the supply roller (12) and the sleeve (5), and each supply roller (12) is arranged to face the magnetic pole of the magnetic roller (6).

Also, supply rollers (12), conveyance blades (16), (17
) is adapted to be driven and connected to a drive source (not shown) by mounting the cartridges (10a), -, (10d) in predetermined positions.

Furthermore, the supply rollers (12) of the force-tolidine (10a) to (10d) are connected to a DC bias (V ss) to an AC bias (V
rms) is selectively applied, and the DC bias (Vss) has a variable output, and the output voltage is controlled by a control device (not shown) to control the operating state of the developing device (1). It is changed as shown in the table below. In addition, AC Nokuiasu (Vr
ms) frequency ranges from 100 to 400 hertz.The developer used in the developing device (1) is a two-component developer consisting of toner and magnetic carrier, and due to frictional contact between the two, the toner is Polarity, the carrier is selected to be charged with negative polarity, and the carrier is attached to the developing sleeve (5
), and toners of different colors are stored in each hopper (15) of the cartridge (]Oa), . . . , (IOd).

Under such conditions, the top layer cartridge (1
Regarding the developing operation when the color of the toner stored in 0a) is selected, (1) at startup, (ii) at development,
(iii) At the time of collection, this will be explained sequentially in three parts.

(i) At start-up When the print switch is turned on, the DC bias (Vss) is set to -200V by a signal from the control device, and the supply roller of the cartridge (10a) is set to -200V by a signal from the control device. (12) contains direct current (-
A recovery bias (Vs) is applied, which is a superimposition of alternating current (700 V) on 200 V). At the same time, a developing bias (Vb=-15OV) is applied to the developing sleeve (5).

Next, when the drive source (not shown) is turned on, the phenomenon sleeve (5), supply roller (12), conveyance blade (16), (
+7), respectively arrows (a), (b),
Start rotating in the directions (c) and (d).

As a result, the hopper (
] Inside I5, toner lumps are pulverized based on the rotation of the conveying blades (16) and (+7), and the toner is gradually conveyed to the drum, and based on the rotation of the supply roller (I2). It is incorporated into the four microscopic parts of its surface and filled with it.

Any excess of the toner held on the surface of the supply roller (12) is scraped off at the part facing the subsequent blade (13), and when passing through the part facing the blade (13), this is removed. The toner is pre-charged to a positive polarity by contact with the toner, thereby forming a charged thin film layer of the toner.

Based on the rotation of the supply roller (12), this thin film of toner reaches the toner supply area (Ya), which is the part facing the developing sleeve (5), and is transferred to the carrier held on the developing sleeve (5). is supplied to the surface of the developing sleeve (5) based on the scraping action of.

The toner supplied to the surface of the developing sleeve (5) is conveyed in the direction of arrow (b) based on the rotation of the developing sleeve (5), the toner is mixed with the carrier, and due to frictional contact between the two, the toner becomes positive. In terms of polarity, carriers are charged with negative polarity.

Then, the developer flows into the curved empty space (
8), most of the material is blocked, is pushed by the developer sent later, curves up along the height regulating member (7), and then falls further and falls onto the developing sleeve (5) again. Retained. That is, here, the developer is well mixed and stirred while forming a clockwise vortex, and the two-component developer is adjusted to have an improved potential suitable for development.

A portion of the developer sufficiently mixed and adjusted in this way passes between the brush height regulating member (7) and the developing sleeve (5) to form a magnetic brush, and the magnetic flanno is used for subsequent exposure to light. After passing through the development area (X) that faces the body drum (100), it reaches the part facing the supply roller (12).
The toner on the supply roller (12) is scraped off again, and the toner concentration on the developing sleeve (5) gradually increases.

Note that the supply roller (I2) is provided with a DC bias (VsS).
Since not only AC bias (Vrms) is also applied, the toner is distributed between the supply roller (12) and the developing sleeve (5).
), the alternating current bias (Vrms
), and the holding force also changes in strength periodically.

Therefore, the toner on the surface of the supply roller (12) comes into frequent contact with the carrier and the magnetic brush, is efficiently scraped off, and the toner concentration on the developing sleeve (5) rapidly increases.

By the way, along with the toner supply operation, in the toner supply area (Ya), the supply roller (
The operation of collecting toner in step I2) is also performed in parallel. However, the developing bias (Vb) and recovery bias (
Based on the bias voltage difference between the developing sleeve (
5) Until the toner concentration on the top reaches a certain value, the amount of supplied toner is greater than the amount collected, and during that time the developing sleeve (
5) The upper toner concentration increases.

Then, after a certain period of time has passed, when the balance between the toner supply amount and the toner collection amount is maintained and the toner concentration on the developing sleeve (5) reaches a constant value, the DC bias (Vss) is changed by a signal from a control device (not shown). -200V to -300V
can be switched to

As a result, some of the positively charged toner on the developing sleeve (5) is electrostatically collected by the supply roller (12), and the toner concentration on the developing sleeve (5) decreases slightly. Developing sleeve (5)
The upper toner concentration is maintained at a proper level.

(ii) During development With the developer having a constant concentration adjusted on the developing sleeve (5) in this way, after being uniformly charged (-600V) with a charger (not shown), A photosensitive drum (1) formed by image exposure from an optical system
The electrostatic latent image on 00) moves from the direction of arrow (e) to the development area (
X) When the electrostatic latent image approaches, when the magnetic brush on the developing sleeve (5) is rubbed, it electrostatically attracts toner and becomes a visible image.

This visualized toner image is transferred to copy paper in a subsequent transfer process (not shown), while the surface of the sleeve (5) that has consumed toner in the development area continues to be removed by the arrow (a). ), the vacant chamber (8) is uniformly replenished with new toner, and the consumption pattern of toner consumed in the previous development is erased.

In the toner supply area (Ya), an amount of toner corresponding to the amount consumed in development is supplied to the surface of the developing sleeve (5), and the toner concentration on the surface of the developing sleeve (5) is maintained at a constant state.

iii. After the development operation during collection is completed, the DC bias (Vss) in the collection bias (Vs) is switched from -300V to -350VtC by a signal from a control device (not shown). As a result, the electrical attractive force toward the supply roller (12) acts on the toner on the developing sleeve (5), which is charged with a positive polarity, greater than the attractive force with the carrier. The balance between toner supply and collection in the toner supply area (Ya) is disrupted, and the toner on the developing sleeve (5) is collected on the surface of the supply roller (12).

Note that since an alternating current is superimposed on the recovery bias (Vs), the electrical attraction force of the supply roller (12) acts on the toner on the developing sleeve (5) with periodic strength and weakness, and the toner and carrier are separated. The suction force of the toner is significantly weakened, and the toner is quickly collected by the supply roller (I2).

The toner collected by the supply roller (12) is conveyed in the direction of arrow (b) while being electrostatically held on the surface of the supply roller (12), and passes between the toner return prevention film (I4). Enter the hopper (I5) and insert the blade (13).
It is mechanically scraped off and collected in the hopper (15).

Of course, at this time, the toner filled in the minute recesses on the surface of the supply roller (12) passes between the blade (13) and is carried to the toner supply area (Ya), but the developing bias (
Based on the bias voltage difference between Vb) and the collection bias (Vs), toner is not newly supplied to the surface of the developing sleeve (5).

As a result, all the toner from the surface of the developing sleeve (5) is collected into the hopper (I5) of the cartridge (10a), leaving only the carrier on the developing sleeve (5).

Next, when the color of the toner contained in the lowest cartridge (10d) is selected using a color selection switch (not shown), the control device that receives the signal from the selection switch switches the switch (S W ) to switch the cartridge (
A recovery bias (Vs) is applied to the supply roller (12) of 10d).
Connect.

When a print switch (not shown) is turned on in this state, toner is supplied from the cartridge (10d) and the same developing operation as described above is performed.

Note that at this time, only the carrier was present on the developing sleeve (5), and it was used in the previous development! - Since all the toners are collected in the cartridge (10a), toners of different colors are mixed on the developing sleeve (5), and this is further supplied to the electrostatic latent image on the photoreceptor drum (100) to form a copied image. There is no mixing of colors.

To replenish toner to the cartridges (10a), . Then, put it back in its original position.

At this time, a stopper is formed on each of the housing (2) and the cartridge casing (l), and a predetermined gap is created between the supply roller (12) and the developing sleeve (5) at the position where both stoppers abut. Therefore, the developing conditions can be maintained constant even if the cartridge is inserted or removed.

Incidentally, toner has different charging properties depending on its color.

Regarding this point, as shown in Figure 4, three types of toners, black, sepia, and blue, were mixed at a mixing ratio of 7
．． The results of experiments in which black toner was mixed with carrier at a ratio of 5 wt% and stirred showed that black toner approaches its saturated charge amount in a short mixing time, while blue toner takes a long time to approach its saturated charge time. found. That is, it can be seen that the black toner has the best chargeability, and the blue toner has the poorest chargeability. The material composition of each toner is shown in the table below.

Toner Material Composition On the other hand, in the developing device (1), the distance from the toner supply area to the empty chamber (8) is longer in the upstream cartridge than in the downstream cartridge.

Therefore, the direction of rotation of the developing sleeve (5) (arrow (a)
) direction), the cartridge located furthest downstream (
If the toner with good chargeability is stored in order from the upstream side (IOa) to the upstream side (-/), the toner with poor chargeability will be stored from the time it is supplied to the developing sleeve (5) until it reaches the empty chamber (8). By passing through multiple magnetic pole opposing parts,
The charging potential can be improved by frictionally contacting the carrier on the developing sleeve (5) for as long as possible and as often as possible.

As a result of the mixing and agitating operation in the empty chamber (8), the toner powder is further charged to a state suitable for development, so that the toner powder is not transported to the development area (X) with insufficient charging, and toner powder smoke due to insufficient charging is prevented. The occurrence of fogging, fogging, etc. is prevented.

Therefore, if the developing device (1) according to the present invention uses the three types of toner, blue, sepia, and black are stored in the cartridge in the order of blue, sepia, and black from the downstream side in the rotational direction of the developing sleeve (5). There is a need.

Next, when a collection bias (Vs) in which direct current (DC) and alternating current (AC) are superimposed is applied to the supply roller (12) as in the developing device (1) according to the present invention, the supply roller (1
2) When the collection bias (Vs) applied to 0V is applied, when only direct current (DC) is applied as the collection bias (Vs), in the above three cases, the toner supplied onto the developing sleeve (5) FIG. 2 shows the results of examining the supply characteristics of the toner by measuring the toner concentration on the developing sleeve (5) over time.

As a result, when the recovery bias Vs=OV, the toner concentration on the developing sleeve (5) continues to rise rapidly and becomes uncontrollable, and when only direct current (DC) is applied, Vs=
Although not as extreme as the OV case, it can be seen that the toner concentration gradually increases and the toner concentration cannot be maintained constant.

On the other hand, direct current (DC) is used as recovery bias (Vs).
When an alternating current (AC) is superimposed on the toner, the toner concentration increases earlier than when only the direct current (DC) is applied, and the toner concentration stabilizes at a certain level, at which point the toner supply and collection amounts change. It can be seen that the balance is maintained.

In addition, as for the collection bias (V s), the amount of water collected from the developing sleeve (5) to the supply roller (12) is determined when alternating current (AC) is superimposed on direct current (DC) and when only direct current (DC) is applied. The toner collection characteristics can be adjusted using the collection roller (
12) The results obtained by measuring the toner concentration above are shown in FIG.

As a result, when AC is superimposed on the recovery bias (Vs),
It can be seen that the toner on the developing sleeve (5) is collected by the supply roller (12) more quickly than when only direct current is applied.

That is, from the above experimental results, the developing device according to the present invention (
As shown in 1), if the collection bias (Vs) applied to the supply roller (12) is a combination of direct current (DC) and alternating current (AC), the supply roller (12)
2) The upper toner is quickly supplied to the developing sleeve (5), and the toner concentration on the developing sleeve (5) can be quickly raised to a predetermined concentration, and the toner concentration during development can be stably maintained. Can be done. Also, when collecting toner, the toner on the developing sleeve (5) is removed by the collecting roller (I2).
is quickly recovered.

In addition, in the said Example, a cartridge (10a).

~, (10d) are supplied with toner from each cartridge (10d).
Although the cartridges 0a), . You can also do this.

In this way, it is not necessary to take out the cartridge every time toner is replenished, and the toner replenishing operation can be simplified.

Further, in the above embodiment, the toner on the developing sleeve (5) is collected into the hopper (I5) every time development is completed, but the present invention is not limited to this, and the color selection switch is used to select the toner color. The toner may be collected only when the toner is changed. However, if the toner is collected after each development as in the above embodiment, there is an advantage that the properties of the toner can be maintained normally even when the developing device (1) is not used for a long period of time.

Furthermore, in the embodiment, each cartridge (10a), .
, (10d) are configured to store toners of different colors, but the invention is not limited to this. For example, the upper cartridges (lOa) and (10b) store the frequently used black toner, and the lower cartridges (lOa) and (10b) store toner of different colors. Cartridge (IOc), (l O
d) may contain different color toners.

(Effects of the Invention) As is clear from the above description, the developing device according to the present invention includes a plurality of toner cartridges disposed around a developing sleeve and housing toner supply/recovery rollers facing the developing sleeve, Toner is supplied from each cartridge to the surface of the developing sleeve, while toner is collected into the cartridge from above the developing sleeve.

Therefore, the gap between each supply roller and the developing sleeve is always maintained in a constant state, and toner supply and collection operations can be performed stably, making it possible to always obtain images with a constant density.

Further, since a complicated mechanism is not required for attaching and detaching the cartridge, the configuration becomes simple.

Furthermore, since the supply roller always faces the developing sleeve at a fixed position, there is a low risk of toner spilling out from the supply roller or the cartridge, and there is no chance of contaminating the interior of the image forming apparatus equipped with this developing device. There is no possibility that toners of different colors will be mixed in the developing device or housing, or that toners of different colors will be collected in other cartridges, resulting in color mixture of images.

Furthermore, when replenishing toner, if you take out only the necessary cartridges or replenish toner from a separate hopper to the necessary cartridges, the toner replenishment operation will be simple and easy, and It doesn't stain your body.

When changing the toner color, it is only necessary to change the drive system and bias voltage of the toner supply roller, so it can be done instantly.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a developing device according to the present invention, FIG. 2 is a diagram showing toner supply characteristics, FIG. 3 is a diagram showing toner recovery characteristics, and FIG. 4 is a diagram showing toner charging characteristics. ! ...Developing device, 2...Housing, 3, 4...
opening, 5... developing sleeve, 6... magnetic roller,
7... Height regulating member, 8... Developer reservoir, lOa
, ~, lOd...toner supply cartridge, 11.
...Casing, 12...Toner supply/collection roller,
I3... Blade, I4... Toner return prevention film, 15... Hopper, 16° 17... Conveying blade, v
b...Development bias, Vs...Recovery bias, Vs
s...DC bias, V tms...AC bias, SW...switch.

Claims (1)

[Claims] (1) A two-component developer is prepared by supplying toner to the magnetic carrier held on the outer peripheral surface of the developing sleeve, and the electrostatic charge formed on the surface of the electrostatic latent image carrier using the developer In a developing device that develops a latent image, a toner storage cartridge is provided with a supply/collection roller that supplies toner to the surface of the developing sleeve and collects the supplied toner, and the supply/collection roller is connected to the developing sleeve. A developing device characterized in that a plurality of developing devices are arranged opposite to the outer peripheral surface of the developing device.