JP3228822B2 - Developing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used in a multicolor image forming apparatus such as a color copying machine and a color printer.

[0002]

2. Description of the Related Art As a developing device used in a multi-color image forming apparatus such as a color copier, a casing having an opening facing a latent image carrier, provided in the opening of the casing, and capable of reversible rotation. A non-magnetic sleeve, a developing roller comprising a plurality of magnets provided in the sleeve, and carrying and transporting the developer, a paddle for transporting the developer to the vicinity of the developing roller, and provided near the sleeve. A doctor blade for controlling the height or amount of a magnetic brush made of a developer formed on the surface of the developing roller is known, and a color copying machine is provided with a plurality of such developing devices. In such a color copying machine, even when one of the plurality of developing devices is operating, the developing rollers of other developing devices face the latent image carrier.
Therefore, a developing device at the time of non-development prevents color mixing by cutting the magnetic brush formed on the developing roller.

There have been various proposals for this method of cutting ears. For example, Japanese Unexamined Patent Publication (Kokai) No. 63-229472 discloses a method in which a permanent magnet for restricting the spikes of a magnetic brush is mounted in front of a doctor blade. It is disclosed that the cutting of the ears is performed by stopping the conveying means. In Japanese Utility Model Laid-Open Publication No. 61-89863, ears are regulated by using a movable magnetic material. Further, an example of a method of cutting ears that has been put into practical use will be described with reference to FIG.

In FIG. 1, a photosensitive drum 1 as a latent image carrier is driven to rotate in the direction of the arrow. The developing roller 2 applies a developer 9 composed of the toner and carrier conveyed by the paddle 5 to a plurality of fixed magnets 3 in the developing roller 2.
By rotating the non-magnetic sleeve 4 carried and rotatable clockwise by the magnetic force, a magnetic brush is formed on the developing roller 2. This magnetic brush is used for the developing roller 2
The height or amount is controlled by the doctor blade 6 with the rotation of, and the photosensitive drum 1 is conveyed to a position facing the photosensitive drum 1. The magnet 3 is a magnet for pumping the developer 9 conveyed by the paddle 5 to the developing roller 2, and the magnet 3 b is a magnet for drawing the developer 9 from the developing roller 2 into the casing 7. Between these magnets 3a and 3b, there is a low magnetic portion 8 having a relatively low magnetic force that does not require the developer 9 to adhere.

When the nonmagnetic sleeve 4 is rotated in the counterclockwise direction, the developer drops in a portion that has passed through the low magnetic portion 8, and the developer drops and the developer does not adhere. The part is moved to a position facing the photosensitive drum 1. Thus, since the portion that has passed through the low magnetic portion 8 where the developer 9 is less adhered is opposed to the photosensitive drum 1, the portion is cut off, so that color mixing can be prevented.

[0006]

In the developing device described above, it is necessary to pump a large amount of the developer 9 to the developing roller 2 and control it by the doctor blade 6 in order to obtain a good developing property. I have. However, in the above-described ear-cutting method, the smaller the amount of the developer 9 adhered to the low-magnetic portion 8, the more advantageous the ear-cutting can be performed, and it is advantageous.

As described above, in the developing device, the pumping function and the head cutting function are contradictory. In order to satisfy both functions, the developing device is separated from the magnet 3a and the magnet 3b to be drawn in, and the interval between the low magnetic portions 8 is increased. Must spread. But,
In order to increase the distance between the low magnetic portions 8, the diameter of the developing roller 2 needs to be increased, and the position for drawing up the developer must be changed, and the size and arrangement of the developing device and / or its components are limited. There was a problem that it would.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, the present invention provides a developing device capable of satisfying a contradictory pumping function and a head cutting function without being restricted by the size and arrangement of the developing device and / or its components. It is intended to provide a device.

[0009]

In order to achieve the above object, the present invention provides a casing in which a developer is stored and an opening facing a latent image carrier is formed, and a casing is provided at the opening of the casing. A reversible rotatable non-magnetic sleeve, a developing roller including a plurality of magnets provided in the sleeve, for carrying and transporting the developer, a paddle for transporting the developer to near the developing roller, and the sleeve And a doctor blade for controlling the height or amount of a magnetic brush made of a developer formed on the surface of the developing roller, and facing the latent image carrier on the developing roller during non-development. In the developing device for cutting off the magnetic brush in a portion, the magnet is provided outside the casing and the developing roller that pumps up the developer conveyed by the paddle. The location is characterized in that a magnet and of opposite polarity of the permanent magnets.

The present invention is effective when the permanent magnet is supported by a variable distance mechanism for varying the distance to the developing roller. Further, according to the present invention, the variable distance mechanism and a stopper that holds the closure of the developer collection port are directly or indirectly connected to each other, the operation of separating the permanent magnet from the developing roller, and the closure of the developer collection port. It is effective if the release operation of the stopper is linked.

Still further, according to the present invention, there is provided a contact / separation means for directly or indirectly connecting the variable distance mechanism and a stopper for holding the developer collecting port closed, and for bringing the permanent magnet into and out of the developing roller. It is effective if an operation of separating the permanent magnet from the developing roller and an operation of releasing the stopper that closes and holds the developer collecting port are interlocked by the operation of the contacting / separating means.

Further, the present invention provides the above-mentioned permanent magnet,
It is effective that the permanent magnet is supported by an elastic member and pressed against the outside of the casing by means for pressing the permanent magnet.

Further, the present invention is effective when the permanent magnet is held at a position close to the developing roller at the time of development, and is moved away from the developing roller at the time of the cutting operation.

[0014]

According to the above arrangement, the developer conveyed by the paddle is positioned at a position facing the magnet of the developing roller for pumping up the developer.
Since a permanent magnet having a different polarity from the magnet is provided, a large amount of the developer can be guided to the pumping position by adding the magnetic force of the permanent magnet, and the developer pumping position is separated from the magnet that draws the developer into the casing. The distance between the low magnetic portions can be increased.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 2 is an explanatory view showing a main part of the developing device according to the present invention, and the same members as those of the conventional developing device shown in FIG.

In FIG. 2, in the developing device of this embodiment, a permanent magnet 10 having a polarity different from that of the magnet 3a is provided at a position facing and near the magnet 3a for pumping the developer 9 carried by the paddle 5. Have been. In this case, the permanent magnet 10 is mounted outside the casing 7 facing the magnet 3a.

In the developing device having such a configuration, the developer 9 conveyed by the paddle 5 is pumped up to the developing roller 2 by two magnetic forces of the pumping magnet 3a and the permanent magnet 10. Compared with the conventional developing device shown in FIG. 1, even if the pumping magnet 3a is shifted upward away from the magnet 3b to be drawn in, the developer 9 at the pumping position of the developing roller 2 does not run short.
Therefore, the interval between the low magnetic portions 8 can be widened without hindering the pumping function, and if the low magnetic portions 8 are widened, a good ear cutting can be obtained.

Thus, the developing device according to the present embodiment can satisfy the pumping function and the ear cutting function with a simple configuration in which the permanent magnet 10 is provided. When the built-in developer 9 deteriorates, the developing device collects the deteriorated developer 9 and replaces it with a new developer. At this time, if the permanent magnet 10 is provided, there is a problem that a part of the deteriorated developer 9 is attracted to the permanent magnet 10 and cannot be collected.

In order to solve such a problem, as shown in FIG. 3, a permanent magnet 10 is connected to a rotating shaft 11 as a variable distance mechanism.
It is attached to the front end of the support plate 12 fixed to. The rotating shaft 11 of the present example is manually rotated, and its rotation range is appropriately regulated by a stopper.

When the developer 9 is collected, the permanent magnet 10 is moved to the position shown by the dashed line when the developer 9 is collected, so that the permanent magnet 10 can be largely separated from the casing 7. As a result, a part of the developer 9 is not attracted to the permanent magnet 10, and there is no trouble in collecting the developer 9.

FIG. 4 shows another embodiment of the developing device according to the present invention. The paddle 5 is constituted by a dual cross mixing roller, and the outer screw 1
3 transports the developer 9 to the near side of the developing device, and the inner screw 14 transports the developer 9 to the far side of the developing device. An end of the paddle 5 on the front side of the developing device protrudes outward from the side portion 7a of the casing 7, and a developer recovery port 15 is provided at this protruding portion. Developer recovery port 15
Is closed by a recovery lid 16 shown in FIGS.

As shown in FIGS. 5 and 6, the recovery lid 16 holds the developer recovery port 15 in a closed position by a stopper 17. The stopper 17 is connected to the rotating shaft 11
The stopper 17 is rotated by the rotation of the rotating shaft 11, and is rotated to a position outside the position for holding the collection lid 16. Therefore, the rotating shaft 11
When the permanent magnet 10 is largely separated from the casing 7 by the rotation of, the stopper 17 is set so as to deviate from the position for holding the collection lid 16.

With this configuration, the operation of separating the permanent magnet 10 from the casing 7 and the operation of collecting the developer can be linked, and a part of the developer 9 remains when the developer 9 is collected. It can be avoided reliably.

FIG. 7 shows still another embodiment of the developing device according to the present invention, wherein the permanent magnet 10 is connected to a solenoid 18 via a support member 19,
0 indicates that the casing 7 is energized and demagnetized by the solenoid 18.
Is automatically connected to and detached from.

FIG. 8 is a timing chart of the developer collection mode, the driving of the paddle 5, and the operation of the solenoid 18.
When the developer is collected, the operation of driving the paddle 5 and the operation of exciting the solenoid 18 shown in FIG. 7 to separate the permanent magnet 10 from the casing 7 are matched.

According to this structure, the operation of separating the permanent magnet 10 from the casing 7 at the time of collecting the developer can be automatically performed in conjunction with the operation of the stopper 17 coming off the position where the recovery lid 16 is held.

FIG. 10 shows still another embodiment of the developing device according to the present invention. The permanent magnet 10 is attached to a supporting member 12 via a leaf spring 20 as an elastic member. Is urged by a spring 21 in a direction to press the permanent magnet 10 against the casing 7.

With this configuration, when the permanent magnet 10 is pressed against the casing 7 by the spring 21, the leaf spring 20 bends and the permanent magnet 10 can be brought into close contact with the casing 7.

By the way, when cutting ears during non-development,
The portion where the developer has dropped through the low magnetic portion 8 is opposed to the photosensitive drum 1. At this time, the sleeve 4 is rotated in the reverse direction because the portion where the developer has passed through the low magnetic portion 8 and has dropped. This is because the developer is opposed to the photosensitive drum 1 so that the developer is not pumped up through the pumping position. However, in the embodiment shown in FIG. 7, if the permanent magnet 10 is largely separated from the casing 7, the amount of the developer 9 at the pumping position becomes extremely small. Therefore, the developing device according to the present invention is provided with the sleeve 4
Rotating either forward or reverse can cut the ears.

When cutting the ears by rotating the sleeve 4 forward,
As shown in the timing chart of FIG.
The permanent magnet 10 is separated from the casing 7 in synchronism with the time of forward rotation and the time of ear cutting.

When the sleeve 4 is rotated in the reverse direction, the permanent magnet 10
12 can be sufficiently removed without removing the permanent magnet 10 from the casing 7 even when the sleeve 4 is rotated in the reverse direction and in synchronization with the cutting of the ears, as shown in the timing chart of FIG. Disappears,
More reliable ear cutting can be obtained.

[0032]

According to the above construction, in the present invention, a permanent magnet having a different polarity from the magnet is provided at a position facing the magnet of the developing roller for pumping up the developer conveyed by the paddle. A large amount of the developer can be guided to the pumping position by the addition of the magnetic force, and the developer pumping position can be separated from the magnet that draws the developer into the casing, thereby increasing the interval between the low magnetic portions. Therefore, the size and arrangement of the developing device and / or its components are not restricted, so that the degree of freedom is increased and the size can be reduced.

Further, the problem that a part of the developer due to the provision of the permanent magnet is not attracted to the permanent magnet and cannot be recovered is also caused by moving the permanent magnet away from the casing 7 when recovering the developer. In addition, a part of the developer is not attracted to the permanent magnet, and there is no trouble in collecting the developer.

Further, since the operation of separating the permanent magnet from the casing and the operation of collecting the developer can be linked, it is possible to reliably prevent a part of the developer from remaining at the time of collection.

Further, the operation of separating the permanent magnet from the casing when the developer is collected can be automatically performed in conjunction with the operation of the stopper coming off the position holding the collection lid.

Further, when the permanent magnet is pressed against the casing 7, the permanent magnet is bent by the leaf spring, and the permanent magnet can be brought into close contact with the casing. Further, according to the present invention, the ears can be cut by rotating the sleeve 4 in either the forward direction or the reverse direction.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a main part of a conventional developing device.

FIG. 2 is an explanatory diagram showing a main part of the developing device according to the present invention.

FIG. 3 is an explanatory view showing another embodiment of the present invention.

FIG. 4 is a perspective view showing a paddle portion.

FIG. 5 is an external perspective view of the developing device.

FIG. 6 is a side view of FIG. 5;

FIG. 7 is an explanatory view showing still another embodiment of the present invention.

FIG. 8 is a timing chart of a developer collection mode, driving of a paddle, and a solenoid.

9 is an explanatory diagram showing a state where the permanent magnet of FIG. 7 is separated from a casing.

FIG. 10 is an explanatory view showing still another embodiment of the present invention.

FIG. 11 is a timing chart when the ear is cut by rotating the sleeve forward.

FIG. 12 is a timing chart when the sleeve is reversed and the ears are cut.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoreceptor drum 2 Developing roller 3 Magnet 3a Pumping magnet 3b Pull-in magnet 4 Sleeve 5 Paddle 6 Doctor blade 7 Casing 8 Low magnetic part 9 Developer 10 Permanent magnet 11 Rotating shaft 15 Developer recovery port 16 Recovery lid 17 Stopper 18 Solenoid 20 Leaf spring

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-4-338774 (JP, A) JP-A-63-60472 (JP, A) JP-A-59-147369 (JP, A) 96569 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G03G 15/09 G03G 15/08

Claims (6)

(57) [Claims] 1. A casing for storing a developer and having an opening facing a latent image carrier, a non-magnetic material sleeve provided in the opening of the casing and reversibly rotatable, provided in the sleeve. A plurality of magnets, a developing roller for carrying and transporting the developer, a paddle for transporting the developer to the vicinity of the developing roller, and a developer provided near the sleeve and formed on the surface of the developing roller. A doctor blade for controlling the height or the amount of the magnetic brush comprising: a developing device for cutting off the magnetic brush at a portion of the developing roller facing the latent image carrier during non-development; A permanent magnet having a polarity different from that of the magnet is provided at a position facing the magnet on the outside of the developing roller for pumping up the developer transported by the paddle. A developing device for. 2. The developing device according to claim 1, wherein the permanent magnet is supported by a variable distance mechanism that changes a distance to a developing roller. 3. The developing device according to claim 2, wherein the variable distance mechanism is directly or indirectly connected to a stopper that holds the developer collecting port closed, and an operation of separating the permanent magnet from the developing roller. And a releasing operation of a stopper for closing and holding the developer collecting port is linked with the developing device. 4. The developing device according to claim 2, wherein the variable distance mechanism is directly or indirectly connected to a stopper for holding the developer collecting port closed, and the permanent magnet is connected to a developing roller. An operation of separating the permanent magnet from the developing roller and an operation of releasing a stopper for closing and holding the developer collecting port are linked by the operation of the contacting / separating means. apparatus. 5. The developing device according to claim 1, wherein the permanent magnet is supported via an elastic member, and is pressed against the outside of the casing by means for pressing the permanent magnet. Developing device. 6. The developing device according to claim 1, wherein the permanent magnet is held at a position close to the developing roller at the time of development, and is moved to a position distant from the developing roller at the time of the cutting operation. A developing device.