JPS626231B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electrostatic latent image developing device, and more particularly, to an electrostatic latent image developing device used for visualizing an electrostatic latent image in an electrophotographic copying machine or the like. It is.

Conventionally, the electrostatic latent image developing device includes a developing sleeve that is rotationally driven in the same direction as the developer conveying direction, a magnet that is provided in the developing sleeve in a stationary state, and a magnet that is installed in the developing sleeve in a stationary state. Developing devices equipped with a scraping blade that removes developer conveyed along the surface of the developing sleeve from the surface of the developing sleeve have been widely put into practical use. On the other hand, in recent years, in order to improve the agitation performance of the developer, developing devices have been developed in which the direction of rotation of the developing sleeve is reversed and the magnet is driven to rotate in the same direction as the direction of rotation of the developing sleeve. has been proposed.

In this type of developing device, the force to convey the developer due to the rotation of the magnet and the force to convey the developer due to the rotation of the developing sleeve are:
Each acts in opposite directions on the developer. The conveying force due to the rotation of the magnet is the force that attempts to convey the developer by forming a brush of developer using the magnetic field of the magnet and causing this brush to rotate due to the rotation of the magnet. The object is to be conveyed in a direction opposite to the direction of rotation. On the other hand, the conveying force due to the rotation of the developing sleeve is a force that attempts to convey the developer in the rotating direction of the developing sleeve as the developing sleeve is rotated. As shown below, in this type of developing device, two conveying forces act in opposite directions on the developer, but the conveying force by the magnet is set to be larger than the conveying force by the developing sleeve. As a whole, the developer is transported in a direction opposite to the rotation direction of the developing sleeve.

However, in reality, some of the developer, such as non-magnetic toner, is not easily affected by magnetic force and therefore does not easily rotate due to the rotation of the magnet, and is simply attached to the developing sleeve. A phenomenon of movement in the rotational direction occurs. Then, in this adhered state, it reaches the back surface of the blade opposite to the scraping surface. Then, such developer is compressed and accumulated between the back surface of the blade and the developing sleeve, and as a result, it becomes agglomerated in the space formed between the back surface of the blade and the developing sleeve and the contact area between the two. . This is because the developer adheres to the developing sleeve itself and moves, and is pushed between the blade and the developing sleeve by the strong mechanical force accompanying the rotation of the developing sleeve.

Therefore, in order to put this type of developing device into practical use, it is first necessary to solve this problem.

The present invention has been made in view of these points, and includes a developing sleeve that is rotated in the opposite direction to the developer conveying direction, and a developing sleeve that is provided within the developing sleeve and rotates in the same direction as the rotating direction of the developing sleeve. a magnetic roller that is rotationally driven; and a cleaner member that removes, from the developer supplied to the surface of the developing sleeve, the developer that adheres to the surface of the developing sleeve and is moved in the opposite direction to the developer conveyance direction. and,
An electrostatic latent image developing device comprising a scraping blade that removes the developer conveyed along the surface of the developing sleeve from the surface of the developing sleeve after being used for development, the scraping blade having a thickness of 30 mm. It is made of a flexible sheet material with a thickness of ~100 μm, and the pressure angle with respect to the plane tangential to the developing sleeve on the downstream side in the developer transport direction is set to 0 to 30 degrees, so that it adheres to the surface of the developing sleeve and prevents the developer from flowing in the developer transport direction. The tip of the scraping blade can be pushed up by the developer moving in the opposite direction, and at the tip of the scraping blade,
It is characterized in that it allows passage of developer moved in a direction opposite to the developer transport direction.

That is, in the embodiment of the present invention described later, the developer scraping blade 8b that removes the developer transported along the surface of the developing sleeve 2 from the developing sleeve 2 after being used for development has a thickness of 130 to 100 μm. A flexible sheet material is used, and the pressure contact angle α with respect to the tangential plane with the developing sleeve 2 on the downstream side in the developer transport direction is set to 0 to 30°. As a result, the tip of the blade 8b can be pushed up by the developer that adheres to the surface of the developing sleeve 2 and moves in the opposite direction to the developer conveyance direction.
The developer that is moved in the opposite direction to the developer transport direction is allowed to pass through the leading end of the developer.

An embodiment of the electrostatic latent image developing device according to the present invention will be described below with reference to the accompanying drawings. In the examples described below, for convenience, a mixture of an insulating non-magnetic toner with an average particle size of 3 to 30 μm and a magnetic toner with an average particle size of 3 to 30 μm and a resistivity of 10 ³ to ^{10 16} Ω·cm is used. Although only a developing device using a magnetic developer such as Problems such as those mentioned above occur,
The present invention is also effective as an electrostatic latent image developing device using these magnetic developers.

In FIG. 1, a developing device 1 generally includes a developing sleeve 2 installed in a developing area, a magnetic roller 3 installed inside the developing sleeve 2, and a casing 5 installed inside a developer tank 4. It is composed of a developer stirring/supplying mechanism 6. The developing sleeve 2 is made of a non-magnetic conductive material such as aluminum and is formed into a cylindrical shape. It is rotated at a speed of .pm. The magnetic roller 3 has an N pole and an S pole around it.
It is a roll-shaped product in which the poles are sequentially magnetized, and is driven to rotate in the same direction as the developing sleeve 2 at a speed of 2000 rpm. Here, when the diameter of the developing sleeve 2 is 31 mm, the developer on the surface of the developing sleeve 2 is conveyed by a conveying force clockwise relative to the developing sleeve 2 at a speed of about 10 cm/s due to the rotational drive of the magnetic roller 3. On the other hand, as the developing sleeve 2 is rotated, a force of approximately 5 is applied in a counterclockwise direction opposite to the conveying force.
It receives a conveying force at a speed of cm/S. Therefore, as a result, the developing sleeve 2 moves clockwise at a speed of about 5 cm/s.
It will be transported along the surface.

The lower part of the developing sleeve 2 is provided with a flexible non-magnetic sheet material, such as an appropriate synthetic resin sheet material,
Or a cleaner blade 8a made of metal or the like,
and the developer scraping blade 8b, and furthermore, the auxiliary cleaner blade 8c extends its tip to the developing sleeve 2.
It is provided in pressure contact with the surface. As shown in the figure, the cleaner blade 8a and the auxiliary cleaner blade 8c are arranged so that the pressing angle with respect to the tangential plane with the developing sleeve on the upstream side in the developer conveyance direction is an acute angle, while the developer scraping blade 8b is arranged to remove the developer. It is inclined so that the pressure contact angle with respect to the tangential plane with the developing sleeve on the downstream side in the transport direction is an acute angle.

The cleaner blade 8a and the auxiliary cleaner blade 8c adhere to the surface of the developing sleeve 2 as the developing sleeve 2 is rotated, out of the developer supplied to the surface of the developing sleeve 2, and move the developer in the developer conveying direction (clockwise). It has a function of removing the developer moving in the opposite direction from the surface of the developing sleeve 2. Note that when a large amount of developer is excessively supplied to the surface of the developing sleeve 2 by the developer stirring/conveying mechanism 6, the developer that is present at a position away from the surface of the developing sleeve 2 (the developer that is present on the tip side of the brush)
Since it is hardly affected by the magnetic force of the magnetic roller 3, it moves in the direction of rotation of the developing sleeve 2 without receiving almost any conveyance force based on the rotation of the magnetic roller 3, and is removed by the cleaner blade 8a. Therefore, the excessive amount of developer supplied to the surface of the developing sleeve 2 by the developer stirring/conveying mechanism 6 is removed from the surface of the developing sleeve 2 by the cleaner blade 8a, and an appropriate amount of developer is delivered to the developing area. transported to.

In addition, in this embodiment, while the developing sleeve 2 is always driven to rotate, the magnetic roller 3 is configured to be driven to rotate only during development and stop rotating when not in development. The developer is conveyed clockwise as shown in the figure, but it is returned counterclockwise during non-development. Therefore,
During non-development, the cleaner blade 8a also has the function of removing all the developer present on the surface of the developing sleeve 2. Therefore, in this embodiment, unnecessary contact of the developer with the surface of the photoreceptor drum 7 is avoided.

The developer scraping blade 8b has the function of removing the developer transported along the surface of the developing sleeve 2 from the surface of the developing sleeve 2 after being used for development, while also removing the developer that adheres to the surface of the developing sleeve 2 and is used for development. The developing sleeve is arranged so as to allow the passage of the developer moving in the direction opposite to the developer conveying direction (clockwise), and so that the pressure contact angle with respect to the tangential plane with the developing sleeve 2 on the downstream side of the developer conveying direction is an acute angle. It is pressed against 2. Therefore, the developer attached to the developing sleeve 2 that could not be completely removed by the cleaner blades 8a and 8c during development is
Since the developer scraping blade 8b is pushed up and passed through, the developer is not compressed and accumulated in the space formed between the back surface of the developer scraping blade 8b and the developing sleeve 2 and the contact area between the two. Further, during development, the developer scraping blade 8b cannot remove the developer and the developer accumulates in the space formed by the back surface of the auxiliary cleaner blade 8c and the developing sleeve (the space on the upstream side in the developer transport direction). The developer is also moved counterclockwise together with the developing sleeve 2 during non-development,
Since the developer passes through the tip of the developer scraping blade 8b and is removed by the cleaner blades 8a and 8c, this developer also enters the space formed between the back surface of the developer scraping blade 8b and the developing sleeve. It is not compressed and accumulated over a long period of time. Note that during development,
The developer cannot be completely removed by the developer scraping blade 8b,
The developer that may accumulate in the space formed between the back surface of the auxiliary cleaner blade 8c and the developing sleeve as a result of being transported in the clockwise direction is only subjected to the transporting force due to the action of the magnetic roller 3, and moreover, the developer is is rotationally driven in the opposite direction, so that a conveying force in the opposite direction to that conveying force is acting. Therefore, the force applied to the developer accumulated in the space formed by the back surface of the auxiliary cleaner blade 8c and the developing sleeve is accumulated in the space formed by the back surface of the developer scraping blade 8b and the developing sleeve 2. The force is very small compared to the force that the developer is subjected to, and even if the accumulation progresses, the developer is not compressed to the point where it forms an agglomerate.

Regarding the present embodiment, to specifically describe the components of the developer that behave as described above, they are not affected by the conveying force caused by the rotation of the magnetic roller 3, and adhere to the surface of the developing sleeve 2, in the direction opposite to the direction in which the developer is conveyed. Most of the developer that is moved is a component that is not easily affected by the magnetic field of the magnetic roller 3, that is, non-magnetic toner.
On the other hand, the developer accumulated in the space upstream of the auxiliary cleaner blade 8c in the developer transport direction is transported by the rotation of the magnetic roller 3, overcoming the transport force in the opposite direction caused by the rotation of the developing sleeve 2. These components are transported without being completely removed by the developer scraping blade 8b, and the magnetic toner accounts for a high proportion.

In the developing device configured as described above, the developer made of a mixture of magnetic toner and non-magnetic toner housed in the casing 5 is mixed and agitated by the developer agitation/supply mechanism 6 while being applied to the surface of the developing sleeve 2. After that, the developing sleeve 2,
Due to the influence of the conveying force caused by the rotational drive of the magnetic roller 3, a total of about 5
It is conveyed clockwise at a speed of cm/s, and the surface of the photoreceptor drum 7 is rubbed in the developing area where the developing sleeve 2 and the photoreceptor drum 7 face each other, and the electrostatic latent image previously formed on the surface is removed. develop. The developer on the surface of the developing sleeve 2 after being used for development is further conveyed clockwise, scraped off by the developer scraping blade 8b, and returned to the developer tank 4.

When the electrostatic latent image has negative polarity, it is necessary to set in advance so that the magnetic toner holds a negative charge and the non-magnetic toner holds a positive charge. In addition, a bias voltage having the same polarity as the electrostatic latent image is applied to the developing sleeve 2 in order to suppress fogging on the photosensitive drum 7 (adhesion of developer to non-image areas on the photosensitive drum). It is necessary to keep it.

Here, the developer scraping blade 8b, the cleaner blade 8a, and the auxiliary cleaner blade 8c
The configuration will be explained in more detail.

The tip of the developer scraping blade 8b is pushed up by the developer that adheres to the surface of the developing sleeve 2 and is moved in the opposite direction to the developer transport direction, and it is necessary to allow the developer to pass through. . Therefore,
For this purpose, the scraping blade 8b must have a moderately soft stiffness. In addition, while satisfying the above conditions, the material and the installation of the scraping blade 8b are selected so that the original function of the scraping blade 8b, that is, the function of removing the developer from the surface of the developing sleeve 2 after being used for development, can be achieved. You must pay close attention to it. Furthermore, if the thickness of the tip of the blade 8b is thick, a brake is applied to the conveyance of the developer to be removed, and excessive developer accumulates below the gap between the developing sleeve 2 and the photoreceptor drum 7. Since this can cause image fogging, etc., attention must also be paid to its thickness.

Therefore, in this embodiment, Mylar with a thickness of 50 μm is used as the developer scraping blade 8b, the contact angle is 7° (the value of α shown in FIG. 2), and the protrusion amount is: 10mm (l as shown in Figure 2)
values). According to experiments conducted by the present inventors, it is preferable to use a flexible sheet material with a thickness of 30 to 100 μm as the developer scraping blade 8b, and the contact angle is 0 to 30 degrees.
Furthermore, it has been confirmed that it is appropriate to set the protrusion amount to 5 to 20 mm.

On the other hand, the cleaner blade 8a and the auxiliary cleaner blade 8c are for removing developer that adheres to the surface of the developing sleeve 2 and is moved as the developing sleeve 2 is rotated.
The developer is subjected to a relatively large mechanical force at the tip portions a and 8c. Therefore, the developer at the tip is easily solidified under the influence of mechanical pressure, heat, and the like. If the thickness of the tips of the blades 8a, 8c is thick, solidified developer particles with a large diameter are formed at the tips, and then these developer particles are conveyed to the developing section, and the photosensitive drum 7. It metastasizes to the surface and adversely affects the reproduced image. A typical example of this is the photosensitive drum 7.
When the developed image on the surface is transferred to a transfer paper or the like, black spots with white spots around the periphery are generated in the image. Therefore, the blades 8a, 8c
The thickness of the tip must be appropriately thin. Further, while satisfying the above conditions, the blades 8a, 8
The material and the location of the material are selected so that the original function of c is achieved, that is, the function of removing the developer that adheres to the surface of the developing sleeve 2 and is moved in the opposite direction to the developer conveyance direction from the surface of the developing sleeve 2. It is necessary to be careful about

Therefore, in this embodiment, Mylar with a thickness of 200 .mu.m is used for the cleaner blade 8a and the auxiliary cleaner blade 8c, the contact angle is set to 15 degrees, and the protrusion amount is set to 5 mm. According to experiments conducted by the present inventors, the cleaner blade 8a and the auxiliary cleaner blade 8c
The thickness is 100 to 500 μm, preferably 150 to 500 μm.
250μm thick flexible sheet material or tip thickness
It is preferable to use a knife-edge member with a diameter of 500 μm, preferably 250 μm or less, and in the case of the former, the pressure contact angle is 0 to 45 degrees, preferably 10 to 30 degrees.
It has also been confirmed that it is appropriate to set the protrusion amount to 2 to 15 mm.

However, if the cleaning action of the cleaner blade 8a is sufficient, only a small amount of developer should be removed by the auxiliary cleaner blade 8c, so the auxiliary cleaner blade 8c may not necessarily satisfy the above conditions. Above, there is no problem. Further, the auxiliary cleaner blade 8c can also be omitted.

In this embodiment, the developer scraping blade 8b is provided with a support member 8b' as its support. In order to prevent the developer removed from the surface of the developing sleeve 2 from being adsorbed to the surface of the developing sleeve 2 again, the removed developer is not influenced by the magnetism of the magnetic roller 3. It is designed to guide you to your location. Similarly, the cleaner blade 8a includes a support member 8a' as its support.

As is clear from the above description, according to the electrostatic latent image developing device of the present invention, the scraping blade removes the developer that adheres to the surface of the developing sleeve and moves in the direction of rotation of the sleeve. Since the developer that cannot be removed due to the scraping blade is allowed to pass through, the developer is not compressed and accumulated in the space formed between the back surface of the scraping blade and the developing sleeve and the contact area between the two. Various harmful effects caused by such problems can also be prevented.

[Brief explanation of the drawing]

FIG. 1 is a drawing showing an embodiment of an electrostatic latent image developing device according to the present invention, and FIG. 2 is a partially enlarged view thereof. 1...Developing device, 2...Developing sleeve, 3...
Magnetic roller, 7... Photosensitive drum, 8a... Cleaner blade, 8a'... Support member, 8b... Developer scraping blade, 8b... Support member, 8c... Auxiliary cleaner blade, α... Press contact angle , l...protrusion amount.

Claims (1)

[Claims] 1. A developing sleeve that is rotationally driven in a direction opposite to the developer conveyance direction, a magnetic roller that is provided inside the developing sleeve and that is rotationally driven in the same direction as the rotational direction of the developing sleeve, and a magnetic roller that is supplied to the surface of the developing sleeve. A cleaner member removes from the developing sleeve surface the developer that adheres to the developing sleeve surface and moves in the opposite direction to the developer conveyance direction, and An electrostatic latent image developing device comprising a scraping blade that removes the transported developer from the surface of the developing sleeve, wherein the scraping blade is made of a flexible sheet material with a thickness of 30 to 100 μm, and The pressure angle with respect to the tangential plane with the developing sleeve on the downstream side of the developer conveyance direction is set to 0 to 30 degrees, and the developer adheres to the surface of the developer sleeve and moves in the opposite direction to the developer conveyance direction. An electrostatic latent image developing device, characterized in that the tip of the scraping blade can be pushed up, and the tip of the scraping blade allows the developer moved in a direction opposite to the developer conveyance direction to pass therethrough.