JPH058431B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a developing device for an electrophotographic device used as a copying machine or a printer. The present invention relates to a developing device that visualizes an image.

[Prior art]

As shown in FIG. 1, a conventional electrophotographic developing device of this type has a cylindrical non-magnetic sleeve 2 attached to a photosensitive drum 1 having a photosensitive member on its surface with a predetermined gap therebetween.
by facing each other, supporting a cylindrical magnet roll 3 in this non-magnetic sleeve 2 in a non-contact manner, and rotating either or both of the non-magnetic sleeve 2 and the magnet roll 3. The magnetic toner 5 contained in the toner hopper 4 is conveyed by a non-magnetic sleeve 2, and the conveyed magnetic toner 5 is slid onto the surface of the photosensitive drum 1 for development.

In this configuration, development is performed by grounding the non-magnetic sleeve 2 or applying a bias potential to the electrostatic latent image potential of the photosensitive drum 1.
The non-magnetic sleeve 2 also serves as a developing electrode.

FIG. 2 is a graph showing the moving speed of the surface of the photosensitive drum 1 as it rotates, that is, the results of measuring the development density when developing under constant development conditions with respect to the photosensitive drum speed.As the photosensitive drum speed increases,
In other words, it can be seen that as the development time decreases, the developed density decreases. In other words, high-speed imaging results in a decrease in developed density.

One possible method for increasing the development time without reducing the speed of the photosensitive drum is to lengthen the development area. To achieve this, the diameters of the photosensitive drum 1 and the non-magnetic sleeve 2 can be simply increased, but this is disadvantageous in that it increases the size of the apparatus.

Therefore, conventionally, when performing high-speed development, a non-magnetic sleeve 2 containing the magnet roll 3 was used.
A plurality of these are arranged along the surface of the photosensitive drum 1, thereby increasing the developing time.However, this structure also has the drawbacks of a complicated mechanism and an increase in the size of the device.

[Purpose of the invention]

The present invention was made in order to solve the above-mentioned drawbacks of the prior art, and is an electrophotographic method that allows for a long development area without increasing the size of the device, and that enables high-speed development with sufficient density. The purpose is to realize a developing device automatically.

[Structure of the invention]

In order to achieve this object, the present invention includes a developing electrode plate disposed so as to face the outer circumferential surface of a photosensitive drum on which an electrostatic latent image is formed, with a certain gap in between;
a toner hopper containing magnetic toner for development;
A toner supply roll is disposed in the opening at the bottom of the toner hopper and rotates to supply the magnetic toner in the toner hopper to a developing area between the photosensitive drum and the developing electrode plate; The magnetic toner on the side of the developing electrode plate in the developing area is conveyed in a direction opposite to the rotating direction of the photosensitive drum, and the conveying speed is conveyed in the same direction as the rotating direction of the photosensitive drum on the side of the photosensitive drum in the developing area. a magnet roll that rotates in the same direction as the photosensitive drum so as to be faster than the conveying speed of the magnetic toner; a toner stopper formed of an electrical insulator that regulates the conveyance area of the magnetic toner being conveyed; and a toner stopper that is disposed upstream of the magnet roll in the rotational direction of the photosensitive drum, and is conveyed by the rotation of the magnet roll. a magnetic shielding plate made of a magnetic material that regulates a conveying area of the magnetic toner together with the toner stopper; and an edge of the magnetic toner on the rotating drum at a position downstream of the toner supply roll in the rotational direction of the photosensitive drum. a toner sensor arranged to detect the transfer section; and a magnetic material arranged downstream of the magnet roll in the rotational direction of the photosensitive drum to prevent the magnetic field of the magnet roll from affecting the transfer section. A magnetic shielding plate is formed.

[Effect]

In the present invention having such a configuration, the layer thickness of the magnetic toner supplied from the toner hopper to the developing area by the toner supply roll is increased by rotating the magnet roll inside the photosensitive drum in the same direction as the photosensitive drum. is held constant, and in this state, when the electrostatic latent image formed on the photosensitive drum is sent to the development area by the rotation of the photosensitive drum, magnetic toner adheres to this electrostatic latent image and is developed. At the same time, the magnetic toner is transferred to the development area by the toner supply roll according to the detection result of a toner sensor that detects the end of the magnetic toner on the rotating drum at a position downstream of the toner supply roll in the rotational direction of the photosensitive drum. The supply is controlled to maintain a constant amount of magnetic toner in the development area.

[Embodiment] FIG. 3 is a schematic side sectional view showing an embodiment of the present invention. In the figure, 6 is a photosensitive drum, which is a cylindrical base material made of a non-magnetic conductive material and has a photosensitive member on its outer peripheral surface. It is made up of layers. Arrow A indicates the direction of rotation.

A cylindrical magnet roll 7 has a structure in which a plurality of north poles and south poles are alternately magnetized in the circumferential direction. This magnet roll 7 is a photosensitive drum 6
The photosensitive drum 6 is arranged near the inner circumferential surface of the photosensitive drum 6 and rotates in the same direction as the photosensitive drum 6 as shown by arrow B.

Reference numeral 8 denotes a developing electrode plate, which faces the outer peripheral surface of the photosensitive drum 6 with a certain gap therebetween so as to correspond to the magnet roll 7, and is adapted to be grounded or applied with a bias potential during development. .

9 is a magnetic toner, and 10 is a toner hopper containing the magnetic toner 9. This toner hopper 10 is arranged near the developing electrode plate 8, and the photosensitive drum 6 and the developing electrode are placed in an opening provided at the bottom of the toner hopper 10. A toner supply roll 11 is rotatably mounted to supply magnetic toner 9 to the development area between the plate 8 and the toner supply roll 11 .

Reference numeral 12 denotes a toner stopper made of an electrical insulator, and one end of the toner stopper 12 is located at a predetermined position above the developing electrode plate 8, that is, at a position on the upstream side of the developing electrode plate 8 in the rotational direction of the photosensitive drum 6. It is installed so as to face the outer peripheral surface of the photosensitive drum 6 with a small gap therebetween.

Reference numeral 13 denotes a toner sensor which is a combination of a light emitting element and a light receiving element, for example, and is located at a predetermined position below the developing electrode plate 8, that is, at a position on the downstream side of the toner supply roll 11 in the rotational direction of the photosensitive drum 6. It is placed toward the outer circumferential surface of the

Magnetic shielding plates 14 and 15 are made of a soft magnetic material, and one magnetic shielding plate 14 is connected to the photosensitive drum 8.
The other magnetic shielding plate 14 is disposed on the downstream side of the magnet roll 7 in the rotational direction of the photosensitive drum 8 so as to be located between the magnet roll 7 and a transfer section (not shown) in the magnet roll. It is arranged upstream of the nettrol 7.

Next, we will explain the operation of the above configuration.
First, when the toner supply roll 11 is rotated, the magnetic toner 9 in the toner hopper 10 is sequentially taken out in a constant small amount by the toner supply roll 11, and the taken out magnetic toner 9 is transferred to the photosensitive drum 6 by the magnetic attraction force of the magnet roll 7. Supplied on top. When a certain amount of magnetic toner 9 is supplied, the rotation of the toner supply roll 11 is stopped.

The magnetic toner 9 supplied as described above forms a layer on the photosensitive drum 6 and is conveyed in a developing area between the photosensitive drum 6 and the developing electrode plate 8.

The pattern of this conveyance will be described with reference to FIG. First, the portion of the layer of magnetic toner 9 on the photosensitive drum 6 side is magnetically attracted by the rotation of the photosensitive drum 6 as shown by arrow a, in the same direction as the rotational direction of the photosensitive drum 6, that is, the direction of arrow A. and transported at the same speed.

On the other hand, the part of the layer of magnetic toner 9 far from the photosensitive drum 6, that is, the part on the side of the developing electrode plate 8, is indicated by the arrow B.
By the rotation of the magnet roll 7 in the direction, the photosensitive drum 6 is conveyed in the rotational direction of the photosensitive drum 6, that is, in the direction opposite to the direction of the arrow A, as shown by the arrow b.

The conveyance speed at this time is mainly determined by the rotation speed and the number of magnetic poles of the magnet roll 7, but in the present invention, the conveyance that depends on the rotation of the magnet roll 7 is in the opposite direction to the conveyance that depends on the rotation of the photosensitive drum 6. and set it to
In addition, the conveying speed due to the rotation of the magnet roll 7 is set higher than the conveying speed due to the rotation of the photosensitive drum 6. Therefore, the conveyance of the magnetic toner 9 in the direction of the arrow b overcomes the conveyance in the direction of the arrow a, but the conveyance in the direction of the arrow b stops when it hits the toner stopper 12 provided to restrict the upper end. At this point, the magnetic toner 9 turns toward the photosensitive drum 6 as shown by arrow c, and is further conveyed in the direction of arrow a. Furthermore, at the end of the layer of magnetic toner 9 opposite to the toner stopper 12, less magnetic toner 9 is transported in the direction of arrow b, so that the layer is transported in the direction of arrow a so that the thickness of the layer is constant. Here, the magnetic toner 9
direction, and from there it is conveyed in the direction of arrow b.

In this way, the thickness of the magnetic toner 9 during conveyance is determined by the conveyance speeds in mutually opposite directions indicated by arrows a and b. For example, if the transport speed in the direction of arrow a, that is, the rotation speed of the photosensitive drum 6 is kept constant, and the transport speed, which depends on the rotation speed of the magnet roll 7, is increased, the thickness of the layer of magnetic toner 9 increases.
By adjusting these transport speeds, a layer of desired thickness can be formed.

As described above, in the present invention, by reciprocating the magnetic toner 9 on the outer peripheral surface of the photosensitive drum 6, a layer of the magnetic toner 9 having a constant thickness is formed in the development area.

Note that the toner stopper 1 of this layer of magnetic toner 9
The position of the end opposite to 2 is determined by the amount of magnetic toner 9 supplied onto the photosensitive drum 6.

Further, as described above, the toner stopper 12 is
Although the tip thereof is provided so as to face the surface of the photosensitive drum 6 through a small gap, the magnetic toner 9 does not leak through the gap when the magnetic toner 9 is conveyed. Because Magnetrol 7
Conveyance dependent on the rotation of the photosensitive drum 6 is caused by a chain of magnetic toner 9 rotating on its own axis due to a substantially rotating magnetic field. Therefore, in a minute gap, the chain of magnetic toner 9 is shortened, and as a result, the conveyance speed is lower than that of the photosensitive drum 6. , and cannot pass through the gap.

Now, although not shown here, the electrophotographic apparatus has an electrostatic latent image forming means, and this electrostatic latent image forming means generates an electrostatic charge on the outer peripheral surface of the photosensitive drum 6 which is rotating at a constant speed. A latent image is formed, and this electrostatic latent image is sent to a developing area between the photosensitive drum 6 and the developing electrode plate 8 by rotation of the photosensitive drum 6. At this time, the electrostatic latent image passes near the toner stopper 12, but since the toner stopper 12 is formed of an electrically insulating material as described above, it will not have any adverse effect on the electrostatic latent image. .

In the development area, the magnetic toner 9 is conveyed on the photosensitive drum 6 as described above, and when the electrostatic latent image is sent to this development area, the magnetic toner 9 is electrostatically attracted and the development is completed. It will be done.

Then, as the photosensitive drum 6 further rotates, the electrostatic latent image moves out of the development area of the magnetic toner 9, and along with this, the magnetic toner 9 attracted to the electrostatic latent image also moves away from the development area. , and is sent as a toner image to the next transfer section (not shown). Further, at this time, the magnetic toner 9, which has a weak attraction force, is pulled back to the developing area by the conveying force caused by the rotation of the magnet roll 7, so that clear and high quality development can be performed.

In this way, when successive development is performed, the photosensitive drum 6
The magnetic toner 9 being conveyed above is consumed and reduced accordingly. Therefore, the consumed magnetic toner 9 is supplied as follows.

That is, as described above, in the present invention, the photosensitive drum 6
The state of conveyance of the magnetic toner 9 on the top is a layer of constant thickness with the toner stopper 12 at one end, and the position of the other end is determined by the amount supplied onto the photosensitive drum 6. Therefore, a toner sensor 1 consisting of, for example, a light emitting element and a light receiving element is placed at a predetermined position.
3, it is possible to detect whether the other end extends between the toner sensor 13 and the photosensitive drum 6 based on the difference in reflectance between the magnetic toner 9 and the photosensitive drum 6. Based on this, the magnetic toner 9 in the toner hopper 10 can be supplied onto the photosensitive drum 6.

In other words, when the magnetic toner 9 on the photosensitive drum 6 is consumed by development and decreases, the toner sensor 1
3 detects the end of the layer of magnetic toner 9, and the detection signal causes the toner supply roll 11 to rotate and supply the required amount of magnetic toner 9 onto the photosensitive drum 6. Therefore, a constant amount of magnetic toner 9 is always held in the development area, and stable development can be performed.

By the way, one of the characteristic features of the present invention is that the magnet roll 7 for toner transport is provided inside the photosensitive drum 6, so that the magnetic field from the magnet roll 7 is reduced in the transfer area near the development area. If it is too strong, it may affect the quality of the transferred image.

The magnetic shielding plate 14 is provided between the portion of the photosensitive drum 6 corresponding to the transfer portion and the magnet roll 7 in order to deal with such problems.
This magnetic shielding plate 14 can prevent the influence of the magnetic field on the transfer section.

Note that the process of forming an electrostatic latent image on the photosensitive drum 6 by the electrostatic latent image forming means is not affected by the magnetic field from the magnet roll 7.

In addition, a magnetic shielding plate 1 is used as a toner transport regulating means.
5 is placed between the photosensitive drum 6 and the magnet roll 7 to block the magnetic field from the magnet roll 7, the conveying force of the magnet roll 7 will no longer reach the toner, so the magnetic field can be removed even without installing the toner stopper 12. Conveyance of the toner 9 can be restricted.

〔Effect of the invention〕

As explained above, the present invention provides a magnet roll inside the photosensitive drum, and uses the magnetic attraction force of the magnet roll to directly attract the magnetic toner supplied from the toner hopper onto the photosensitive drum. The rotation of the nettrol transports the magnetic toner back and forth on the photosensitive drum in the development area between the photosensitive drum and the developing electrode plate facing the photosensitive drum, thereby developing the electrostatic latent image formed on the photosensitive drum. Therefore, if the developing electrode plate is formed and installed to have a cylindrical curvature concentric with the photosensitive drum, a sufficiently long developing area can be obtained with a simple configuration, and it is possible to cope with high-speed development. You can get the effect that you can.

Further, in the present invention, as described above, the rotation of the magnet roll and the photosensitive drum reciprocates the magnetic toner on the photosensitive drum, and the rotation of the magnet roll causes the magnetic toner to be conveyed on the electrode plate side in the opposite direction to the rotational direction of the photosensitive drum. The conveying speed of the magnetic toner conveyed in the same direction as the rotating direction of the photosensitive drum is made larger than the conveying speed of the magnetic toner conveyed in the same direction as the rotational direction of the photosensitive drum, and the edge of the magnetic toner on the rotating drum is The supply of magnetic toner to the developing area by the toner supply roll is controlled based on the detection result of the toner sensor, so that a constant amount of magnetic toner is maintained, so the layer thickness of magnetic toner in the developing area is kept constant. This also provides the effect that high-quality development can be performed.

Furthermore, since the magnet roll is provided inside the photosensitive drum as described above, the components of the developing device disposed outside the photosensitive drum include the developing electrode plate,
There is only a toner hopper, toner stopper, and toner sensor with a toner supply roll, which has the effect of realizing a very compact developing device.Furthermore, there is a magnet roll located upstream of the magnet roll in the photosensitive drum. Since a magnetic shielding plate is provided that regulates the conveyance area of the magnetic toner conveyed by the rotation of the toner stopper, it is possible to reliably prevent the magnetic toner from being conveyed upstream of the toner stopper, and also to prevent the magnetic toner inside the photosensitive drum from being conveyed upstream. A magnetic shielding plate is provided upstream of the roll to prevent the magnetic field of the magnet roll from affecting the transfer area, which also has the effect of making it possible to perform good transfer in the post-development process. It will be done.

As described above, the present invention can perform high-speed development with a simple configuration and high quality, and can also reduce the size of the device. It can be effectively used as a device.

[Brief explanation of the drawing]

FIG. 1 is a schematic side sectional view showing a conventional electrophotographic developing device, FIG. 2 is a graph showing the relationship between photosensitive drum speed and developer density, and FIG. 3 is an embodiment of the electrophotographic developing device according to the present invention. FIG. 4, which is a schematic side sectional view showing an example, is an explanatory diagram for conveying magnetic toner in the present invention. 6...Photosensitive drum, 7...Magnetic roll,
8...Development electrode plate, 9...Magnetic toner, 10...
Toner hopper, 11... Toner supply roll, 12
...Toner stopper, 13...Toner sensor, 1
4,15...Magnetic shielding plate.

Claims (1)

[Scope of Claims] 1. A developing electrode plate arranged to face the outer circumferential surface of the photosensitive drum on which an electrostatic latent image is formed, with a certain gap in between, and a toner hopper containing magnetic toner for development. , placed in the opening at the bottom of this toner hopper,
a toner supply roll that rotates to supply magnetic toner in a toner hopper to a developing area between the photosensitive drum and the developing electrode plate; The magnetic toner is conveyed in a direction opposite to the rotational direction of the photosensitive drum, and the conveyance speed is greater than the conveyance speed of the magnetic toner that is conveyed in the same direction as the rotational direction of the photosensitive drum on the photosensitive drum side in the development area. a magnet roll that rotates in the same direction as the photosensitive drum; and a transport area for the magnetic toner that is disposed upstream of the developing electrode plate in the rotational direction of the photosensitive drum and is transported by the rotation of the magnet roll. a toner stopper formed of an electrically insulating material to regulate the magnetic toner; and a toner stopper disposed at a position upstream of the magnet roll in the rotational direction of the photosensitive drum so as to control the transport area of the magnetic toner transported by the rotation of the magnet roll. a magnetic shielding plate made of a magnetic material that regulates the rotation of the photosensitive drum; and a toner sensor arranged to detect an end of the magnetic toner on the rotating drum at a position downstream of the toner supply roll in the rotational direction of the photosensitive drum. and a magnetic shielding plate formed of a magnetic material, which is disposed downstream of the magnet roll in the rotational direction of the photosensitive drum and prevents the magnetic field of the magnet roll from affecting the transfer section, The electrostatic latent image formed on the photosensitive drum is developed by attaching magnetic toner to the electrostatic latent image in the development area, and the supply of the magnetic toner to the development area is controlled based on the detection result of the toner sensor. Electrophotographic development equipment.