JPS63198084A - Developing device - Google Patents

Abstract

PURPOSE:To sufficiently secure the electrification quantity even in case of a toner whose electrification property is inferior, by placing a toner supply cartridge which contains the toner whose electrification property is inferior, so as to be positioned at the upstream side to the rotational direction of a developing sleeve, seeing from a developing area. CONSTITUTION:Plural pieces of toner supply cartridges 10a, 10b, 10c and 10d which contain toners of each different color are placed so that each toner supply/collection roller 12 is opposed to the outside peripheral surface of a developing sleeve 5, and also, a toner supply cartridge 10d which contains a toner whose electrification property is inferior is positioned at the upstream side against the rotational direction of the developing sleeve 5, seeing from a developing area. Accordingly, the toner whose electrification property is inferior, which is supplied to the developing sleeve from the cartridge of the upstream side can gain a frictional contact time to a carrier before reaching the developing area, and also, even if the electrification property is inferior, its toner is not carried to the developing area in a state of an electrification failure, and the generation of toner powder smoke due to the electrification failure, and the generation of fog, etc. are prevented.

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 devices such as chargers, cleaning devices, and erasers are arranged close to each other around the photoreceptor drum, in commonly used image forming apparatuses, the surroundings of the photoreceptor drum are The number of developing devices that can be arranged is also limited to two to 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.

In this device, the developer container is rotated so that the toner supply/recovery roller in the developer chamber containing toner of a specified color faces the developing sleeve, and the toner of the specified color is applied to the surface of the developing sleeve. On the other hand, when switching toner to another color, the toner held on the developing sleeve is first collected into the developer chamber facing the developer chamber, and then the developer container is rotated to transfer the toner to another color. Toners of other colors are supplied from the toner container to the developing sleeve.

(Problems to be Solved by the Invention) However, as in the conventional developing device, one developing sleeve holding a magnetic carrier on the outer peripheral surface is shared;
In a device in which the toner color is switched by rotating and selecting a plurality of developer chambers each containing toner of a different color and each equipped with a toner supply/recovery roller, which toner color is selected? However, the position where the toner supply/collection roller faces the developing sleeve is the same. Therefore, after the toner is supplied from the toner supply/recovery roller in the toner supply area of the developing sleeve, the toner is charged by frictional contact with the magnetic carrier on the developing sleeve, and electrostatically charges the photoreceptor drum in the developing area. The time required for adsorption is constant regardless of the toner color selected.

However, in general, the chargeability of toner depends on its color.

It is known that it varies depending on the material composition. Therefore, if a toner color with poor chargeability is selected, the toner will
When the toner reaches the developing area with an insufficient amount of charge, there are problems such as generation of toner powder smoke and fogging due to insufficient charging.

The present invention has been made in view of such problems, and takes into account the quality of chargeability depending on the difference in toner color, and provides a developing device that can secure a sufficient amount of charge even for toner with poor chargeability. The purpose is to provide equipment.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention supplies toner to a magnetic carrier held on the outer peripheral surface of a developing sleeve that houses a plurality of magnets therein to generate two-component toner. In a developing device that adjusts a developer and develops an electrostatic latent image formed on the surface of an electrostatic latent image carrier using the developer, the toner is supplied to the surface of the developing sleeve; A plurality of toner supply cartridges each having a toner supply/collection roller that collects the supplied toner, each containing a different color of toner, each toner supply/collection roller facing the outer peripheral surface of the developing sleeve, and , a toner supply cartridge containing toner with poor charging properties is arranged so as to be located upstream with respect to the rotational direction of the developing sleeve when viewed from the developing area.

(Example) Next, one embodiment of the present invention will be described with reference to the accompanying drawings.

In FIG. 1, (1) is a developing device according to the present invention. (2) is a nousing of 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 (100) with a predetermined gap, and is rotatable in the direction of arrow (a). , a developing bias (Vb) is applied. A magnetic roller (6) in which a plurality of magnets with magnetic poles extending in the axial direction are disposed in the circumferential direction is fixedly housed inside the developing sleeve (5).

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 developer reservoir (8) is formed behind the height regulating member (7) and above the developing sleeve (5).

(10a), -, (10d) are toner supply cartridges (hereinafter referred to as "cartridges"), which have almost the same structure, and the opening formed in the front part of the box-shaped casing (11) has a A toner supply/recovery roller (hereinafter referred to as "supply roller" X12) having minute recesses 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).
) is pressure contact.

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

Cartridges (10a) with the above configuration, ~, (1
0d) is a cartridge (2) containing toner with good chargeability, such as black toner, in the rear part of the housing (2).
10a) is placed in the top layer, and a cartridge (lOd) containing a toner with poor chargeability, such as blue toner, is placed in the bottom layer, and the casing ('tt)
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 ('10a), . A certain gap is ensured between the developing 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 where the cartridges (10a), ~, (10d) are placed,
By mounting it in a fixed position, it can be driven and connected to a drive source (not shown).

Furthermore, cartridges (10a), ~, (10d
), each supply roller (12) is equipped with a switch (SW
), a recovery bias (Vs), which is a superimposition of an AC bias (V rss) on a DC bias (V ss), is selectively applied, and the DC bias (V ss) has a variable output, and the output voltage is A control device (not shown) changes the operating state of the developing device (1) as shown in the table below. In addition, AC bias (
The frequency of VrIls) is appropriately set in the range of 100 to 400 hertz.

The developer used in the developing device (1) is a two-component developer consisting of toner and a magnetic carrier, and the developer selected is one in which the toner is charged to a positive polarity and the carrier to a negative polarity when the two come into frictional contact. The carrier is magnetically held on the outer circumferential surface of the developing sleeve (5), and toner of different colors is stored in each hopper (15) of the cartridge (lOa), (10d). .

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

(i) At startup: When the print switch is turned on, the DC bias (Vss) is set to -200v by a signal from the control device, and the cartridge (10a) is supplied via the switch (SW). The roller (12) is supplied with direct current (
-200V) and a recovery bias (Vs) superimposed with alternating current (700V) is applied. At the same time, the developing sleeve (5)
A developing bias (Vb=-15OV) is applied to.

Next, when the drive source (not shown) is turned on, the developing sleeve (5), supply roller (12), conveyance blade (16), (
17), the respective arrows (a), (b), (
c) Start rotating in the (d) direction.

As a result, the hopper (
15) Inside, the toner lumps are crushed based on the rotation of the conveying blades (16) and (17), and the toner is gradually conveyed forward, and the toner is crushed into minute recesses on its surface based on the rotation of the supply roller (12). is taken in and filled.

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.

The toner in a film state is held on the developing sleeve (5) when it reaches the toner supply area (Ya), which is the part facing the developing sleeve (5), based on the rotation of the supply roller (12). The carrier is supplied to the surface of the developing sleeve (5) based on the scraping action of the carrier.

The toner supplied to the surface of the developing sleeve (5) is conveyed in the direction of arrow (a) 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.

When the developer reaches the developer reservoir (8) on the front side of the height regulating member (7), most of it is blocked, and is pushed by the developer sent from behind to the developer reservoir (8) on the front side of the height regulating member (7). 7), it curves up along the developing sleeve (
5) held on top. 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 manner passes between the brush height regulating member (7) and the developing sleeve (5) to form a magnetic brush, which is then used for subsequent exposure to light. Development area (X) that is the part facing the body drum (100)
After passing through the toner supply area (Ya), which is the part facing the supply roller (12), the toner supply area (Ya) faces the supply roller (12) again.
) is scraped off, and the toner concentration on the developing sleeve (5) gradually increases.

Note that the supply roller (12) 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).
) is electrostatically held on the surface of the supply roller (12) based on the bias voltage difference between the alternating current bias (V rm
s), 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 (
12) The operation of collecting toner is also performed in parallel. However, the developing bias (vb) and recovery bias (
Based on the bias voltage difference with Vs), the developing sleeve (5
) The amount of supplied toner is greater than the amount of collected toner until the toner concentration on the developing sleeve (5
) the 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 '-300
Can be switched to V.

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 (
When approaching X), the electrostatic latent image is rubbed by the magnetic brush on the developing sleeve (5) and electrostatically attracts toner to become a visible image.

This visualized toner image is transferred to copy paper in a subsequent transfer step (not shown), while
The surface of the sleeve (5) that has consumed toner continues to be transported in the direction of arrow (a) and reaches the developer reservoir (8).
At this point, new toner is uniformly replenished, and the toner consumption pattern 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 recovery is completed, a signal from the control device (not shown) causes the DC via X (
Vss) changes from -300V to -350Vt. 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 developing sleeve (
5) The above toner 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 (12).

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 (14). 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 recovery 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 (15) 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 is present on the developing sleeve (5), and all the toner used in the previous development has been collected in the cartridge (10a), so toners of different colors are present on the developing sleeve (5). There is no possibility that the colors will be mixed and then supplied to the electrostatic latent image on the photoreceptor drum (100), resulting in mixed colors in the copied image.

To replenish toner to the cartridge (tOa), ~, (10d), the cartridge to be refilled with toner was pulled out from the rear opening (4) of the housing (2), the lid (not shown) was opened, and the prescribed toner was replenished. 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 (11), and a predetermined gap is created between the supply roller (12) and the developing sleeve (5) at the position where both stoppers abut. Because it is secured,
Even if the cartridge is inserted or removed, the developing conditions can be maintained constant.

By the way, 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
．． According to the experimental results of mixing with carrier at a ratio of 5 wt% and stirring, black toner approaches its saturated charge amount with a slow mixing time, and blue toner takes a long time to approach its saturated charge amount. It has been 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 toner supply area (Ya
) to the developing area (X) via the developer reservoir (8) is the distance from the developing sleeve (
5) The cartridge (lOd) located furthest upstream with respect to the rotational direction (direction of arrow (a)) is longer than the cartridge (10a) on the downstream side. For this reason,
The frictional contact time between the toner supplied from the upstream cartridge (10d) and the carrier is shorter than that of the downstream cartridge.

However, the blue toner, which has poor chargeability, is stored in the most upstream cartridge (10d), the black toner, which has good chargeability, is stored in the most downstream cartridge (10a), and the sepia toner is stored in the middle cartridge. (1
0b) or (10c). Therefore, from the upstream cartridge (10d) to the developing sleeve (5) 1
The blue toner, which has poor chargeability, is supplied to the developing sleeve (5) and reaches the developer reservoir (8). Aid the opposing part, and then the developing sleeve (5)
Since the developer is disturbed by passing through the small gap between the developer and the supply roller (12), the developer should be in frictional contact with the carrier on the developing sleeve (5) for as long as possible and as often as possible to improve the charging potential. Can be done.

As a result of the mixing and agitating operation in the developer reservoir (8), the developer 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 the toner particles caused by insufficient charging are not transported to the developing area (X). The generation of smoke, fog, etc. is prevented.

In addition, the highly chargeable black toner supplied from the cartridge (10a) on the downstream side to the developing sleeve (5) has a good charging rise and a short time to reach the saturated charge m, so it is stored in the developer reservoir (8). Even if the distance is short, sufficient charging potential can be ensured without causing charging failure.

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 OV is OV, 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 collection bias VsmiOv, the toner concentration on the developing sleeve (5) continues to rise rapidly and becomes uncontrollable, and when only direct current (DC) is applied, Vs=
Even if it is not as extreme as the OV case (1°), 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 the recovery bias (Vs), the supply roller (
The toner collection characteristics collected by the collection roller (12)
2) 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 rapidly 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 (lOc), (10d
) may contain different color toners.

(Effects of the Invention) As is clear from the above description, according to the present invention, a plurality of toners containing toner of different colors are provided around the developing sleeve and include toner supply/recovery rollers facing the developing sleeve. The toner supply cartridges are arranged such that the cartridge containing toner with poor chargeability is located on the upstream side, and while each cartridge supplies toner to the surface of the developing sleeve, the toner is fed into the cartridge from above the developing sleeve. We are trying to collect it.

Therefore, the toner with poor chargeability supplied from the upstream cartridge to the developing sleeve can earn time for frictional contact with the carrier before reaching the developing area, and the toner that is supplied to the developing sleeve from the upstream cartridge can gain frictional contact time with the carrier, and also When the toner supply/recovery roller of the cartridge passes through a small gap in the vicinity, it is disturbed together with the magnetic carrier and charging is promoted. Since the toner is not transported, it has the effect of preventing the generation of toner powder smoke, fogging, etc. due to poor charging.

[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, 10a
, ~, 10d...toner supply cartridge, ll...
・Casing, 12... Toner supply/collection roller, 1
3... Blade, 14... Toner return prevention film, 15... Hopper, 16° 17... Conveying blade, vb
...Development bias, Vs...Recovery bias, Vss
+...DC bias, Vrms...AC bias,
SW...Switch.

Claims (1)

[Claims] (1) Supplying toner to a magnetic carrier held on the outer peripheral surface of a developing sleeve containing multiple magnets;
In a developing device that adjusts component developers and uses the developer to develop an electrostatic latent image formed on the surface of an electrostatic latent image carrier, supplying toner to the surface of the developing sleeve, and It has a toner supply/collection roller that collects the supplied toner, and a plurality of toner supply cartridges each containing a different color of toner are connected to each toner supply/collection roller.
The collection roller is arranged so as to be close to and opposite to the outer peripheral surface of the developing sleeve, and the toner supply cartridge containing the toner with poor charging property is located on the upstream side with respect to the rotational direction of the developing sleeve when viewed from the developing area. A developing device characterized by: