JPH01158469A - Developing device - Google Patents

Abstract

PURPOSE:To prevent a developer from passing and to eliminate a magnetic brush on a developing sleeve completely by providing a shutter with a magnetic pole which shields the developer supply area of a developing sleeve magnetically. CONSTITUTION:When a developing device 1 is selected, a developing device 2 positions a shutter 27 between a bucket roller 25 and a developing sleeve 23 so as to eliminate a magnetic brush on the developing sleeve 23, and then the supply of a developer to the developing sleeve 23, is cut off; and a developer on the developing sleeve 23 is collected to the bucket roller 25 nearby an N2 pole according to the rotation of the developing sleeve 23. Here, the developer which is left without being collected is to be conveyed to the side of an N3 pole, but the developer is scraped off or attracted by a magnetic brush formed on the magnet 28. Consequently, the developer never passes through the gap between the shutter 27 and developing sleeve 23 and the magnetic brush on the developing sleeve 23 is removed completely.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a developing device used in copying machines, printers, etc. It is related to the device.

(Prior Art) Conventionally, there has been provided a developing device in which a plurality of developing units containing developers of different colors are arranged around a photosensitive drum so that any color can be developed.

In this type of developing device, it is necessary to provide each developer so that it can be switched between an operating state and a non-operating state. Conventionally, as a method for switching to a non-operating state, a magnetic brush on a developing sleeve is used to generate an electrostatic latent image. There are a method of retracting the magnetic brush from the carrier, a method of not forming a magnetic brush on the developing sleeve, and a method of changing the developing bias voltage applied to the developing sleeve.

Among these methods, especially in small copying machines, there is no space to evacuate the developing device, so a shutter is installed to cut off the supply of developer to the developing sleeve to prevent the formation of a magnetic brush on the developing sleeve. The method is adopted.

FIG. 6 shows a developing device equipped with such a shutter, which consists of a developing device (1) and a developing device (2). The casings (11) and (21) of each of the developing devices (1) and (2) have magnetic rollers (12) and (22) arranged close to the photoreceptor drum (3) and having a plurality of magnetic poles inside. Developing sleeves (13), (23) fixedly accommodated therein, brush height regulating members (14), (24) facing the developing sleeves (13), (23) with a predetermined gap, and the developing sleeves ( Packet rollers (15) and (23) supply developer consisting of toner and magnetic carrier to
5) and the packet roller (15).

Conveyance rollers (16) and (26) that circulate and convey the developer while mixing and stirring the developer together with (25) are housed therein.

The packet roller (25) of the developing device (2) has
A shutter (27) is arranged in parallel, and a packet roller (
25) so as to be movable along the outer periphery.

That is, this shutter (27) is connected to the packet roller (25) and the developing sleeve (23) as shown by the solid line in FIG.
) and the packet roller (25
) can be switched by a solenoid or the like so that the position is above and .

In this developing device, when the developing device (1) is selected, the developer in the casing (11) is transferred to the developing sleeve (1) by the packet roller (15).
3), this developer is supplied to the magnetic roller (12)
The developer is held on the surface of the developing sleeve (13) by the magnetic force of the developer, and ears of developer (magnetic brush) are formed along the lines of magnetic force of the magnetic roller.

The developer held on the surface of the developing sleeve (13) is conveyed in the direction of arrow (a) based on the rotation of the developing sleeve (13), and the magnetic brush is cut into ears by the ear height regulating member (14) and conveyed. The amount is adjusted.

Thereafter, the developer is transported to a portion facing the photoreceptor drum (3), and rubs against the electrostatic latent image on the photoreceptor drum (3) to develop it.

The developer whose toner content ratio has decreased due to consumption of toner in the development area is subsequently conveyed in the direction of arrow (a), and when it reaches the part facing the packet roller (15), it is transferred to the development sleeve (1
3) and is collected by the packet roller (15).

Subsequently, new developer is supplied to the surface of the developing sleeve (13) by the packet roller (15), and the same developing operation as described above is repeated.

On the other hand, in the developing device (2), the shutter (27) is moved by a solenoid (not shown) to the position shown by the solid line in FIG.
The supply of developer to is blocked. Therefore, the developer held on the developing sleeve (23) is sequentially collected by the packet roller (25) as the developing sleeve (23) rotates, and the developing sleeve (23) is moved as shown in FIG. There is no magnetic brush. Therefore, no development is performed in the development area of the developing device (2).

Next, when the developing device (2) is selected, the shutter (27) of the developing device (2) moves above the packet roller (25) as shown by the two-dot chain line in FIG. The supply of developer from (25) to the developing sleeve (23) is started, and development becomes possible.

In addition, since the developing device (1) does not have a shutter, the developing sleeve (13) stops while holding the developer, and the magnetic brush rubs against the photoreceptor drum (3) to slightly create an electrostatic latent image. However, since the developing device (2) further develops the image, there is no problem of color mixing. In this case, in order to avoid development by the developing device (1), the developing bias voltage applied to the developing sleeve (13) may be set high, or the magnetic roller (12) may be rotated to (The middle part of No. is made to face the photoreceptor drum (3) so that the magnetic brush does not come into contact with it.

(Problems to be Solved by the Invention) However, in the developing device equipped with the shutter, it is necessary to set a narrow gap between the shutter (27) and the developing sleeve (23) (for example, between the insulating non-magnetic toner and the binder). (If a two-component developer consisting of a magnetic carrier and a magnetic carrier is used, the thickness must be 0.5 mm or less). If the gap is wide, uncollected developer will pass from the recovery area (N2 pole side) through the gap to the supply area (N3
(pole side), and the magnetic brush remains.

In addition, especially in small copying machines, there is no dimensional allowance for the height of the shutter (27), so the packet roller (25)
A part of the developer conveyed by the shutter (27) is scattered or pushed out and overcomes the shutter (27).
), that is, the gap between the shutter (27) and the inner wall of the casing (21) of the developing device (2) or a component of the developing device (2), such as the height regulating member (24), and the developing sleeve (23). may be supplied to

Therefore, the toner image formed by the developing device (1) is developed when passing through the developing area of the developing device (2), resulting in problems such as image disturbance and color mixing.

Therefore, in order to eliminate these gaps, the shutter (27)
may be brought into contact with the developing sleeve (23) and the inner wall of the casing (21) of the developing unit (2) or the height regulating member (24), but if it is brought into contact with the developing sleeve (23), it will be formed on the developing sleeve (23). The convex and concave portions are worn away, reducing the conveyance of the developer, and if it comes into contact with the inner wall of the casing (21) of the developing device (2) or the brush height regulating member, there is a drawback that the developer gets caught when returning.

The present invention has been made in view of such problems, and when the shutter cuts off the supply of developer to the sleeve so that the developing device is in a non-operating state, the gap between the shutter and the developing sleeve or It is an object of the present invention to provide a developing device that can prevent developer from slipping through the gap above the shutter and completely eliminate the magnetic brush on the developing sleeve.

(Means for Solving the Problems) In order to solve the above problems, the present invention supplies a developer onto a developing sleeve to form a magnetic brush, and slides the magnetic brush against an electrostatic latent image carrier. The developing device is equipped with a plurality of developing devices for developing an electrostatic latent image using a plurality of developing devices, and is provided with a shutter that cuts off the supply of developer onto the developing sleeve and removes the magnetic brush on the developing sleeve, so that the developing device is in an inactive state. In the developing device that can be switched between operating states, the shutter is provided with a magnetic pole that magnetically shields a developer supply area of the developing sleeve.

(Function) According to the above configuration, firstly, the magnetic brush of the developer that is attracted to the magnetic pole of the shutter closes the gap between the shutter and the developing sleeve and scrapes off the developer on the developing sleeve, so that the developer is collected in the collection area. to prevent it from slipping through to the supply area.

Further, the magnetic brush of the developer that is attracted to the magnetic pole of the shutter closes the gap above the shutter, and prevents the developer from slipping through from the developer supply side to the developing sleeve side.

Second, the magnetic pole of the shutter attracts the developer passing through the gap between the shutter and the developing sleeve by its attractive force, and prevents the developer on the developing sleeve from slipping from the collection area to the supply area.

In addition, the magnetic poles of the shutter attract the developer passing through the gap above the shutter due to its attractive force, and prevent the developer from slipping from the developer supply side to the developing sleeve side.

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

FIG. 1 shows a developing device according to the present invention, and the conventional developing device shown in FIG.
A magnet (28) is provided in the developing device (1).
are substantially the same except that they are similarly provided with a shutter (17) and a magnet (18), and corresponding parts are given the same numbers and their explanation will be omitted.

These magnets (18) and (28) are connected to the developing sleeves (1
3) and (23), and as shown in FIG. N are arranged alternately. Also, this magnet (18), (
28) is a developing sleeve (13).

(23) magnetic roller (12), (22) N2 pole and N
.

It is attached closest to the weak magnetic force part in the middle of the pole.

In addition, as shown in FIG. 3, the shutters (17) and (27
) may be provided with magnetic poles similar to those of the magnets (18) and (28).

In the developing device having the above configuration, the casing (l
l), the developer in (21) is a magnet (1B).

(28), a magnetic brush is formed by the developer. For example, when the developing device (2) becomes inactive and the shutter (27) approaches the developing sleeve (23), as shown in FIG. 23), and the gap between the shutter (27) and the developing sleeve (23) is closed.

As shown in FIG. 1, when the developing device (1) is selected, in the developing device (2), the packet roller (27) is moved to eliminate the magnetic brush on the developing sleeve (23).
25) and the developing sleeve (23), the supply of developer to the developing sleeve (23) is cut off, and the developer on the developing sleeve (23) is transferred to N as the developing sleeve (23) rotates. , sequentially packet rollers (25) in the very vicinity
will be collected. Here, the developer remaining without being collected is N
, the magnet (28
) is scraped off or attracted by the magnetic brush formed on the shutter (27) and the developing sleeve (2).
3), and the magnetic brush on the developing sleeve (23) is completely removed.

In this embodiment, there is a dimensional margin in the height of the shutter (27) and the supply of developer is completely cut off, so the gap above the shutter (27), that is, the shutter ( 27) and spillage of developer from the gap between the height regulating member (24).

Although there is no scattering, it is safe if a magnetic pole is also provided on the top of the shutter (27) for shielding, as will be described later (see FIGS. 7 to 10).

On the other hand, in the developing device (1), since the shutter (17) is located on the packet roller (15), the packet roller (1)
5), the developer is supplied to the developing sleeve (13), a magnetic brush is formed by the developer on the developing sleeve (13), and a developing operation becomes possible.

Therefore, the photosensitive drum (3) developed by the developing device (1)
When the upper toner image passes through the developing section of the developing device (2), the image is neither disturbed nor color mixture occurs.

7 to 10 show other embodiments of the present invention,
A developing sleeve (13) is attached to the shutter (17), (27) of the developing device (1), (2) in the non-operating state.

(23) as well as the part facing the head height regulating member (1
4), magnetic poles are also formed in the portions facing (24).

That is, the one shown in FIG. 7 is the same as the one shown in FIG.
3), (23) and magnets (18), (
28), and the height regulating members (14), (2
There is also a magnet (18a) on the side opposite to 4).

(28a) is attached. The S and N magnetic poles of the magnets (18a) and (28a) are connected to the magnet (
Similar to the magnetic poles 18) and (28), the developing sleeve (13)
, (23) are formed linearly in the same direction as the long plane direction.

Therefore, the magnet (1) of the shutter (17), (27)
8), (28), (18a), and (28a) attract the developer in the casings (11) and (21), forming a magnetic brush as shown in FIG. As a result, for example, in the developing device (2) which is in a non-operating state, the shutter (2)
Since the gap between 7) and the developing sleeve (23) is closed, uncollected developer on the developing sleeve (23) is prevented from slipping through in the direction of arrow a, and the shutter (
27) and the height regulating member (24), the developer that was about to be pushed out toward the developing sleeve (23) in the direction of the arrow by the packet roller (25) over the shutter (27) is attracted to the magnetic brush. Therefore, developer is prevented from spilling from the packet roller (25) side to the developing sleeve (23) side.

The ones shown in Figure 8 are developing sleeves (13) and (23).
The magnet and the height regulating member (14) on the side facing the
The magnets (18b) and (28b), which are integrated with the magnet on the opposite side, are connected to the shutters (17) and (24).
7), and its function is the same as that shown in FIG. 7, so the explanation will be omitted.

The one shown in FIG. 9 has shutters (17), (27), developing sleeves (13), (2
From the part facing 3), the height regulating members (14) and (24
) (18
b) and (28b), and also attach the height regulating member (
14), the part facing (24) is connected to the height regulating member (1).
4) and (24) and are formed so as to be parallel to and close to each other. As a result, for example, in the developing device (2) which is in a non-operating state, the shutter (27) and the developing sleeve (2)
3) as well as the gap between the shutter (27) and the height regulating member (24) are closed by the magnetic brush.
This prevents uncollected developer on the developing sleeve (23) from slipping through in the direction of arrow a, as well as developer pushed out or scattered by the packet roller (25) from slipping through in the direction of arrow a. be done.

The one shown in Fig. 10 has magnetic poles similar to the magnets (18b) and (28b) shown in Fig. 9 formed on the shutters (17) and (27) themselves, and the effect is as shown in Fig. 9. is the same as , and its explanation will be omitted.

In the above embodiment, the gap above the shutter (27), that is, the gap between the shutter (27) and the height regulating member (24) was shielded. In the case of the inner wall of the casing (21) or other structural members, the gap can be similarly shielded.

As described above, in the developing device according to the present invention, the shutter (
17) and (27) allow the developing units (1) and (2) to be quickly switched between operating and non-operating states, and the magnetic brushes of the shutters (17) and (27) allow the developing sleeve (
The magnetic brushes on 12) and (13) can be completely eliminated. Therefore, by switching between the developer (1) and the developer (2) during the - times of document scanning, - sheets of the original are copied in different colors in the paper passing direction, as shown in Fig. 5. , so-called l-scan two-force error operation can be performed.

Hereinafter, a case in which the copying machine equipped with the developing device according to the present invention performs this l-scan double-color operation will be explained with reference to the time chart shown in FIG.

First, in FIG. 1, red developer is stored in the developing device (1), and black developer is stored in the developing device (2). Let us copy the image in red and the X2 part in black.

Then, the exposure point on the photoreceptor drum (3) by an optical system (not shown), the development part by the Pis developer (1) is P3, the development part by the developer (2) is P, and the time is defined as follows. .

tl: The photosensitive drum (3) rotates 01 times and the latent image becomes 2 times.
Time to move from point 1 to point 22, t2+ The photosensitive drum (3) rotates 022 times and the latent image becomes 2
Time to move from point 1 to point 28, t, i Time required to scan the document by Xl from the leading edge to the boundary t4: Time required to scan the document by X from the boundary to the rear edge, t ,; When the print switch is turned on, the main The motor is driven to drive the developing sleeve, photoreceptor drum, etc., and the shutter solenoids of the developing units (1) and (2) are turned on to move the developing sleeve (1),
(2) With no developer on the original, the optical system starts scanning the original.

When the document leading edge switch is turned on and the leading edge of the document is detected, the leading edge of the document is exposed to light at 28 points and an electrostatic latent image is formed.The leading edge of this latent image reaches P and is developed. The shutter (
17) is turned off and developer is supplied onto the developing sleeve (13) to make it ready for development. Three hours after the solenoid of the shutter (I7) is turned off, the development of the X8 portion of the document is completed and the latent image at the boundary approaches P2, so the solenoid of the shutter (17) is turned on and the developing sleeve ( 13) Remove the developer on top.

After the document leading edge switch is turned on (Lz+ts), the boundary of the document reaches 21 points, so t,
Before this time, the solenoid of the shutter (27) is turned off and developer is supplied onto the developing sleeve (23) to make it ready for development. When time t4 has elapsed since the solenoid of the shutter (27) was turned off, the development of the X2 portion of the document has been completed and the latent image at the trailing edge approaches P.
Turn on the solenoid 7) to remove the developer on the developing sleeve (23). When time t6 has passed thereafter, the developer on the developing sleeve (23) runs out at point 21, and at the same time, the development of the trailing edge of the original ends.

(Effects of the Invention) As is clear from the above description, according to the present invention, in the developing device in the non-operating state, the developer passes from the developer collection area on the developing sleeve to the supply area through the gap between the shutter and the developing sleeve. This prevents the developer from slipping through and from the developer supply side through the gap above the shutter to the developing sleeve side, completely eliminating the magnetic brush of the developer on the developing sleeve. The toner image developed by the upstream developing device in an operating state is not disturbed.
This has the effect that color mixing does not occur.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of the developing device according to the present invention, FIG. 2 is an enlarged view of the shutter, FIG. 3 is an enlarged view showing another embodiment of the shutter, and FIG. 4 is a sectional view of the developing device according to the present invention. A time chart of the developing operation to be carried out; FIG. 5 is a diagram showing the paper feeding direction of the document and the boundary between colors; FIG. 6 is a cross-sectional view of a conventional developing device;
FIGS. 7 to 1O are enlarged views showing other embodiments of the shutter. 1.2...Developer, 3...Photosensitive drum (electrostatic latent image carrier), 13.23.
...Developing sleeve, 17.27...Shutter, 18.
28...Magnet. Patent applicant Minolta Camera Co., Ltd. Agent
People Patent Attorneys Aobai Ao and 2 others Figure 1 Figure 2 Figure 3 Figure 6

Claims (1)

[Claims] (1) A magnetic brush is formed by supplying a developer onto the developing sleeve, and a plurality of developing devices are provided to develop the electrostatic latent image by rubbing the magnetic brush against the electrostatic latent image carrier. In the developing device, the developing device is provided with a shutter that removes the magnetic brush on the developing sleeve by cutting off the supply of developer to the developing device, and is capable of switching the developing device between a non-operating state and an operating state. A developing device characterized by being provided with a magnetic pole that magnetically shields a developer supply area.