JPH0443379A - Developing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION 1. The present invention relates to a developing device used to develop a latent image formed on a latent image supporting means in an image forming apparatus such as an electrophotographic copying machine, an electrostatic recording machine, or a magnetic recording machine. The present invention relates to an apparatus, and particularly to a developing apparatus that uses a one-component magnetic developer for development.

In an image forming apparatus such as an electrophotographic copying machine, an electrostatic recording machine, or a magnetic recording machine, a latent image formed on a latent image supporting means is developed by a developing device and visualized as a toner image. I am doing it.

Conventionally, a jumping development method using a -component magnetic developer has been known as the above-mentioned development method. This jumping development method involves applying a carrier-free one-component magnetic developer (hereinafter simply referred to as toner as necessary) to a predetermined thickness on the surface of a developer support means to form a uniform thin layer of developer. The coated layer is carried on a developer supporting means and conveyed to a development position facing the latent image supporting means, and the electrostatic latent image is supported on the latent image supporting means with the coated layer maintained at a required interval. This is a method of developing by making the developer fly from the developer supporting means to the electrostatic latent image bearing surface by the electrostatic attraction of the surface (for example, Japanese Patent Publication No. 41-9475, U.S. Pat. No. 2,833,400). (see book).

According to such a developing method, not only is the developer not attracted to the non-image area where there is no latent image potential on the electrostatic latent image bearing surface of the latent image supporting means, but also the developer is Since the developer carried on the support means does not come into contact with the non-image area, good development can be achieved without any fogging on the non-image area. Furthermore, since no carrier particles are used, good effects such as no fluctuation in the developer mixing ratio and no deterioration of the carrier particles can be obtained.

The present applicant has also proposed Japanese Patent Application No. 52-109240 (hereinafter referred to as "first developability") and Japanese Patent Application No. 53-92108 (hereinafter referred to as "first developability") as a developing method different from the above-mentioned developing method. We have previously proposed a completely new developing method as described in 2.

In the first developing method, the -component magnetic developer, developer support means (non-magnetic), and magnetic field generation means are arranged in this order,
A uniform thin coat layer of developer is formed on the surface of the developer supporting means by the magnetic force of the magnetic field generating means, and this developer coat layer is formed into a fine layer so as not to come into contact with the electrostatic latent image bearing surface of the latent image supporting means. The latent image supporting means is opposed to the latent image supporting means at a distance. and,
The portion of the developer coat layer facing the image area is stretched by the electrostatic attraction of the image area portion of the electrostatic latent image bearing surface of the latent image supporting means, and the developer coat layer is placed on the electrostatic latent image bearing surface. The image area is brought into contact with the image area, and the image area is developed. In this development method, the developer coat layer on the developer support means does not come into contact with the non-image area of the electrostatic latent image bearing surface of the latent image support means, and a developed image with no fog can be obtained during development. It will be done.

In the second development method described above, when carrying out the first development method,
A low frequency alternating current bias voltage is applied as a development bias voltage to the developer support means, and the distance between the electrostatic latent image bearing surface of the latent image support means and the surface of the developer support means opposing thereto is
It is designed to change over time. In this development method, the halftone portion of the image area on the electrostatic latent image bearing surface is developed while the developer reaches the non-image area of the electrostatic latent image bearing surface of the latent image supporting means at the initial stage of development. The developer that has reached the non-image area is returned to the original developer supporting means over time, so that the developer reaches only the image area and develops it. As a result, the reproducibility of the halftone portion by development is better than that of the above-mentioned jumping development method, and at the same time, fog-free development can be realized.

In this way, the method of developing by using a -component developer and moving the developer from the developer support means to the non-contact latent image support means using electrostatic attraction has a number of issues regarding development performance, image reproducibility, developer The lifespan etc. are extremely excellent.

However, even in the above-mentioned developing method, there are problems as described below when putting it into practical use.

That is, the difference in the image history of the electrostatic latent image bearing surface of the latent image supporting means causes a difference in the density of the obtained developed image. Density unevenness is particularly likely to occur in halftone areas, and in extreme cases, characters become thick or thin. The above-mentioned "one image history" means the progress of image formation, whether an image was formed or not formed on the electrostatic latent image bearing surface of the latent image supporting means. Image history of the electrostatic latent image bearing surface The difference in image density occurs because the content of the developer coat layer on the developer support means is influenced by the image history.

To elaborate on this point, in order to develop the image area on the electrostatic latent image bearing surface of the latent image supporting means, the developer coating layer on the developer supporting means is coated on the electrostatic latent image bearing surface at the development position. The portion corresponding to the image area is attracted to the electrostatic latent image bearing surface by electrostatic attraction and flies, and as a result, the developer is removed or only a small amount remains on the surface of the developer supporting means corresponding to the image area. The state will be as follows.

On the other hand, in the developer coating layer on the developer supporting means, the portion corresponding to the non-image area on the electrostatic latent image bearing surface of the latent image supporting means flies to the electrostatic latent image bearing surface at the development position. All or most of the developer remains on the surface of the latent image supporting means corresponding to the non-image area.

Therefore, new developer is not supplied at the next developer supply to the area corresponding to the non-image area on the surface of the developer supporting means.
The developer coat layer remains formed with the previous old developer. In other words, in the area corresponding to the non-image area on the electrostatic latent image bearing surface on the surface of the developer supporting means, due to the image history of non-formation of an image on the electrostatic latent image bearing surface, the developer coat layer is exposed to the old development image from the previous time. It is maintained in its formed state by the agent. on the other hand,
At a portion of the surface of the developer supporting means corresponding to the image area on the electrostatic latent image bearing surface, a developer coat layer is formed with new developer due to the image history of forming an image on the electrostatic latent image bearing surface.

In areas corresponding to the non-image areas of the electrostatic latent image bearing surface on the surface of the developer supporting means, the developer coat layer is formed with old developer due to the image history of non-image formation on the electrostatic latent image bearing surface. If the same location on the surface of the developer support means is repeatedly influenced by the image history, the amount of triboelectricity of the developer at that location on the surface of the developer support means,
The amount of coating changes, and furthermore, deterioration of the developer and contamination of the surface of the developer support means may occur.

As a result, due to the difference in image history between image formation and non-image formation, the developer coating layer on the developer support means has a different state of the developer, resulting in a difference in developing ability, final image density, and quality. . This phenomenon becomes particularly noticeable when a large number of image originals having vertical black or white band images are copied.

Differences in density, etc. of images (particularly halftone images) due to differences in image history between image formation and non-image formation may vary due to various conditions (not limited to those mentioned above, for example, electrostatic charge of the latent image support means). Even if there is a location on the surface of the developer support means that corresponds to a region where there was an image history of image formation on the latent image bearing surface, if the supply of developer to that location is insufficient, the resulting image will not correspond to the region. In addition, the developer coating layer is applied to areas on the surface of the developer support means corresponding to areas where the image history of no image formation on the electrostatic latent image bearing surface of the latent image support means has been repeated. There is a phenomenon in which the triboelectricity of the developer to be formed increases and the amount of developer in the coat layer decreases, and in such a case, the density of the resulting image may decrease at the corresponding location.

In any case, the difference in developability due to the difference in image history can be solved by stripping off all the developer remaining on the surface of the developer support means after passing through the development position. This problem can be solved by supplying new developer to form a thin, uniform developer coat layer of a predetermined thickness.

For this reason, conventionally, as shown in FIG. 8, a developing sleeve 3 serving as a developer skin holding means and a photosensitive material are placed in the lower part of a hopper (developing container) l in which a one-component magnetic developer 2 is stored in a developing device. A scraper 12 is provided that contacts the surface of the developing sleeve 3 on the side opposite to the developing position where the drum 6 faces, and by rotating in the direction of arrow B, the scraper 12 that remains on the developing sleeve 3 after passing through the developing position is provided. developer 2, scraper 1
Peeling has already been carried out in step 2.

In FIG. 8, reference numeral 4 indicates a magnetic roller fixedly installed in the developing sleeve 3, 5 indicates a magnetic blade provided on the top of the developing sleeve 3 of the hopper 1 for regulating the developer, and 9 indicates a hopper. 1 is a developer pumping member that pumps up the developer 2 and supplies it to the developing sleeve 3; 20 is the developing sleeve 3;
This is a bias power supply that applies a developing bias to.

However, since the scraper 12 described above is made of a rigid body, when it comes into contact with the surface of the developing sleeve 3 and rubs it, it causes scratches on the surface of the developing sleeve 3, and as a result, the resulting image is Black streaks, white streaks, etc. may occur. Further, the scraper 12 is also damaged by wear and tear, and as a result, the remaining developer on the developing sleeve 3 cannot be effectively removed by the scraper 12.

The present invention has been made in view of the above circumstances.
The purpose of this is to remove the developer remaining on the surface of the developer support means after development that has passed through the development position, and supply new developer over the entire surface of the developer support means for the next stage of development. By forming a developer coat layer, the influence on developability due to the difference in image history between image formation and non-formation on the electrostatic latent image bearing surface of the latent image supporting means can be eliminated, and development can be performed. The object of the present invention is to provide a developing device that makes it possible.

A second object of the present invention is to provide an elastic roller that moves in contact with the surface of the developer support means as a developer removal means for removing residual developer from the surface of the developer support means. By flexibly removing the residual developer on the surface of the developer support means using the sliding force and the magnetic force generated by the magnetic field generating means within the developer support means, damage to the surface of the developer support means and the elastic roller can be avoided and durability can be improved. The object of the present invention is to provide a developing device with high performance.

A third object of the present invention is to provide a flow path for moving the developer removed from the surface of the developer supporting means by an elastic roller provided as a developer removing means into a developing container containing the developer. It is an object of the present invention to provide a developing device which avoids clogging, spillage, etc. of the developer when removing the developer from the surface of the developer supporting means.

The above-mentioned object is achieved by a developing device according to the present invention. In summary, the present invention provides a method for supporting a one-component magnetic developer contained in a developer container with a built-in developer supply means on the developer support means by the magnetic force of a magnetic field generating means installed within the developer support means. , while regulating the coating layer thickness of the developer on the developer support means with a regulating member, the developer is conveyed by the developer support means to a development position facing the latent image support means, and the developer is In a developing device that develops a latent image formed on an image supporting means with the developer, one of the magnetic poles provided on the magnet.

Rotating in contact with the developer support means at a position between two magnetic poles of the same polarity located upstream of the regulating member and downstream of the development position with respect to the moving direction of the developer support means. The developing device is characterized in that an elastic roller is provided in the developing container.

That is, the present invention eliminates the influence on the developability of the developer on the developer support means of the developing device due to the difference in image history between image formation and non-formation on the electrostatic latent image bearing surface of the latent image support means. Therefore, all of the developer on the developer supporting means is peeled off and a developer coat layer is formed using new developer, thereby obtaining a good image that is not affected by differences in image history.

In the present invention, since an elastic roller that rotates in contact with the developer support means is provided as a means for stripping off the developer on the developer support means, the elastic roller is used as the developer support means and developer stripping means. The developer on the developer supporting means can be peeled off without being damaged. Since the position where the elastic roller strips the developer is set between the two same magnetic poles of the magnetic field generating means built into the developer supporting means, the developer can be stripped more effectively. can be taken as a thing.

Large” 1 case Examples of the present invention will be described below.

FIG. 1 is a sectional view showing an embodiment of the developing device of the present invention. This developing device is applied to a reversal developing copying machine that uses a drum-shaped photosensitive drum 6 as a latent image supporting means. Although not shown in the figure, in addition to this developing device, there are a charging device used in an electrophotographic process, an image exposure device, etc. equipment, transfer equipment, cleaning equipment,
A static eliminator is installed.

This developing device is equipped with a developing container (hereinafter referred to as a hopper) 1 containing a ~component magnetic developer 2, and a developing device made of a non-magnetic material that rotates in the direction of arrow B as a developer supporting means at the opening of the hopper 1. The sleeve 3 is disposed facing the photosensitive drum 6 at a predetermined distance g2 so as to form a developing position therebetween. A magnet roller 4 serving as a magnetic field generating means is disposed inside the developing sleeve 3 so as not to rotate with respect to the rotation of the developing sleeve 3. In the developing sleeve 3,
A bias power supply 20 for applying a developing bias to this
is connected.

At a position above the top of the developing sleeve 3 of the hopper 1, there is a magnetic blade 5 as a developer layer thickness regulating member that regulates the developer 2 carried on the surface of the developing sleeve 3 to a predetermined developer coat layer thickness. It is provided with a required distance g+ from the developing sleeve 3.

Also, in the lower part of the hopper 1, there is a pumping device which rotates in the direction of the arrow to agitate the developer 2 that has been stripped off from the surface of the developing sleeve 3 by an elastic roller ruff, which will be described later. A member 9 is provided. Further, on the inner lower surface of the hopper 1, a magnetic plate 8 is provided near the surface of the developing sleeve 3 on the side opposite to the developing position as a magnetic sealing member for preventing the developer 2 in the hopper 1 from spilling out of the hopper 1. It is arranged to face the surface of the developing sleeve 3 with a predetermined distance therebetween.

Now, in the present invention, the elastic roller 7 is provided in the hopper 1, and as described above, the elastic roller 7 moves the developing sleeve 3.
Peel off the developer 2 from the surface.

The elastic roller 7 is rotatably provided in the hopper 1 in contact with the surface of the developing sleeve 3 on the side opposite to the developing position side.

The elastic roller 7 has a shaft 7 made of a rigid body such as iron or SUS.
An elastic layer 72 is provided on the outer surface of 1, and for the elastic layer 72, foams such as sponge rubber, maltbrene, and other elastic materials can be used alone or in appropriate combinations. For example, when the elastic layer 72 has a two-layer structure, the lower layer may be made of silicone sponge rubber and the upper layer may be made of urethane rubber. When the elastic layer 72 has such a configuration, dimensional accuracy of the outer circumference of the elastic layer 72 can be obtained.

In this embodiment, a magnet roller 4 fixedly provided within the developing sleeve 3 is arranged concentrically within the developing sleeve 3, and as shown in FIG. Magnetic poles N1, S+, Nx, Ss, S near the surface
s are arranged in this order in the circumferential direction and are formed parallel to the longitudinal direction of the roller 4.

The elastic roller 7 is rotatably supported in the hopper 1 at a position where the developing sleeve 3 and the photosensitive drum face each other with respect to the direction in which the developer 2 is conveyed by the developing sleeve 3.
It is set between the magnetic poles S2 and S of the magnet roller 4, which is located downstream of the development position where the latent image on the photosensitive drum 6 is developed and upstream of the magnetic blade 5. That is, one elastic roller 7 is set between magnetic poles S2 and S, which are repelling magnetic poles of the same polarity.

Further, the elastic roller 7 is configured to rotate in the direction shown by the arrow C, and at a position where the rotation direction C of the elastic roller faces the developing sleeve 3, the rotation direction B of the developing sleeve 3 and the counter direction are opposite to each other. It is set.

In such a developing device configuration, when the developing sleeve 3 receives a driving force from a driving source (not shown) and rotates in the direction of arrow B, the one-component magnetic developer 2 in the hopper 1 is affected by magnetic force, electrostatic force, etc. It is supported on the surface of the developing sleeve 3 by the supporting force, and is conveyed together with the developing sleeve 3 in its rotational direction.

The developer 2 carried on the developing sleeve 3 is regulated by magnetic cutting so that the magnetic blade 5 has a predetermined coating layer thickness, and as a result, the developer 2 is transferred onto the surface of the developing sleeve 3. A coating layer having a uniform predetermined thickness is formed. This developer coat layer is conveyed to the developing position as the developing sleeve 3 rotates, and by applying a developing bias to the developing sleeve 3 with the bias power supply 20, the developer 2
corresponds to the pattern of the electrostatic latent image on the photoreceptor drum 6 at the development position, electrostatically jumping a gap g2, transferred to the surface of the photoreceptor drum 6, and subjected to development.

Developing sleeve 3 after passing through the developing position in this way
As described above, the surface remains influenced by the image history of image formation and non-image formation. That is, if there is an image history of image formation on the photosensitive drum 6, the developer 2 at the corresponding location on the developing sleeve 3 is consumed by development, and there is no or almost no developer 2 at that location, and vice versa. If there is an image history in which no image is formed, there is no development with the developer 2 at the corresponding location on the developing sleeve 3, so it is not consumed, and the developer 2 at the corresponding location on the developing sleeve 3 remains there.

The developer 2 remaining on the developing sleeve 3 is collected into the hopper 1 by the rotation of the developing sleeve 3 in the direction of arrow B while being held by the magnetic force of the magnet roller 4. It is conveyed between the magnetic poles S- and Ss that form the repulsive magnetic field shown in the figure, and is completely or almost completely peeled off from the top of the developing sleeve 3 by the elastic roller 7.
The amount of developer removed and remaining on the surface of the developing sleeve 3 is approximately the same with the portion of the photosensitive drum 3 corresponding to the portion that has received the image history of image formation, and the portion corresponding to the portion of the photosensitive drum 3 that has received the image history of no image formation. do.

As described above, in this embodiment, since the elastic roller 7 is configured to strongly contact the developing sleeve 3 made of a non-magnetic material in the repelling magnetic field by the magnetic poles S, , S of the same polarity, the developing sleeve 3 The magnetic toner monocomponent developer 2 held on the surface of the developing sleeve 3 is easily separated from the developing sleeve 3 due to the action of a repulsive magnetic field at the contact portion of the elastic roller 7 with the developing sleeve 3, and the developer 2 Since the sliding force of the elastic roller 7 is applied, the developer 2 is effectively stripped off from the developing sleeve 3. Furthermore, since the elastic roller 7 is made of a flexible elastic member, the developing sleeve 3 will not be damaged.

At this time, if the contact force between the developing sleeve 3 and the elastic roller 7 is weak, the nip width is small, and the developer 2 on the developing sleeve 3 passes through the protrusion at the contact area between the developing sleeve 3 and the elastic roller 7. Therefore, the effect of peeling off and removing the developer 2 from the developing sleeve 3 is small (therefore, the effect of eliminating the influence of image history is reduced. Conversely, if the contact force is too strong, the influence of image history is eliminated). However, the nip width is large and the torque is large, which tends to cause image unevenness.
Although it cannot be said unconditionally depending on the hardness, it is preferably about 2 to 8 mm.

Further, as described above, the rotational direction of the elastic roller rough is set to be the rotational direction B of the developing sleeve 3 and the counter direction arrow C direction at the position where it contacts the developing sleeve 3. The direction of rotation of the elastic roller 7 is important, and it is preferable to rotate the elastic roller 7 in one direction for the following reasons.

The first reason is that the stripping action of the elastic roller 7 for stripping and removing the developer 2 on the developing sleeve 3 is enhanced when the rotating direction of the elastic roller rough is in one direction counter to the rotating direction of the developing sleeve 3. The developer stripping action is caused by two factors: the contact force between the elastic roller 7 and the developing sleeve 3 mentioned above, and the difference in moving speed between the surface of the elastic roller 7 and the surface of the developing sleeve 3. Therefore, if the above contact force is the same, the larger the difference in moving speed is, the more advantageous it is.

Now, if Vo is the moving speed of the elastic roller 7, Vme is the moving speed of the developing sleeve 3, and Vw is the difference in moving speed between the two when the counter is in one direction and VC1 is in the forward direction, then V C = V 11. +V,.

V w ” V * a - V Ha When the moving speeds of the elastic roller 7 and the developing sleeve 3 are set to be the same, it is obvious that setting the counter in one direction will increase the difference in moving speed between the elastic roller 7 and the developing sleeve 3. can do.

The second reason is that, as will be described later, it is more convenient to prevent the developer 2 from clogging and spilling if the rotation direction of the elastic roller rough is in one direction relative to the rotation direction of the developing sleeve 3. .

When the elastic roller 7 is brought into contact with the developing sleeve 3 as in this embodiment, the developer 2 on the surface of the developing sleeve 3 is peeled off and removed at the contact portion with the elastic roller 7.
The developer 2 tends to become clogged upstream of the contact portion and spill out of the hopper 1, so it is necessary to prevent this. As a countermeasure against this, the rotation direction of the elastic roller 7 is set in one direction counter to the rotation direction of the developing sleeve 3 as described above, and the other method is to peel and remove it from the developing sleeve 3 using an elastic roller rough. To provide a flow path for the developer 2 that allows the developer 2 to move inside the hopper 1 without moving outside the hopper 1.

For example, if a space is provided below the abutment between the elastic roller 7 and the developing sleeve 3, the developer 2 peeled off and removed from the developing sleeve 3 by the elastic roller 7 can fill the space below the abutment. Since the developer 2 can be moved downward as indicated by the arrow A due to gravity, the developer 2 does not become clogged upstream of the abutting portion, and the developer 2 can be prevented from spilling out of the hopper 1.

In this embodiment, the developer 2 on the developing sleeve 3 is
After being peeled off and removed from the surface of the developing sleeve 3 by the elastic roller rough, it moves downward as shown by the arrow A due to the action of gravity, and a part of it adheres to the elastic roller 7 as shown by the arrow A, and becomes elastic. It moves upward as the roller 7 rotates, and the other large part moves further downward due to the action of gravity as shown by arrow A2, and is pumped upward while being stirred by the pumping member 9.

Further, the magnetic plate 8 described above is arranged substantially opposite the magnetic pole S of the magnetic roller 4 in the developing sleeve 3. A magnetic force acts between the magnetic plate 8 and the magnetic pole S2, and the magnetic force prevents the developer 2 in the hopper 1 from moving downward to the developing sleeve 3, thereby preventing the developer 2 from spilling out of the hopper 1. Ru.

Here, the reason why it is advantageous to prevent the developer 2 from clogging and spilling if the rotation direction of the elastic roller 7 is in the counter direction with respect to the rotation direction of the developing sleeve 3, as described above, will be explained. It is as follows.

That is, after the developer 2 on the developing sleeve 3 is peeled off and removed by the elastic roller rough, it moves downward as shown by arrow A due to the action of gravity, and then the developer 2 moves in the direction of rotation of the elastic roller 7. Even when the developing sleeve 3 is in the forward direction, it flows further due to the action of gravity as shown by the arrow A2, as in the case of the counter one direction. However, when the elastic roller 7 rotates in the forward direction, the developer 2 flows in the direction opposite to the arrow A1 direction, contrary to when the counter rotates in one direction, and the developer 2 flows into the developing sleeve. Returned to 3. Therefore, the developer 2 is transferred between the elastic roller 7 and the developing sleeve 3.
The rotation direction of the elastic roller 7 should be adjusted to the direction of rotation of the elastic roller 7 to prevent the developer 2 from clogging or spilling. On the other hand, it is better to use a counter in one direction.

In this embodiment, as described above, the elastic roller 7 has a magnetic pole S
2. The elastic roller 7 is brought into contact with the developing sleeve 3 in a repulsion magnetic field caused by S. The contact position of the elastic roller 7 will be explained in detail with reference to FIG.

In FIG. 2, the angle /5zOAS formed by the magnetic poles S2 and 83 with respect to the rotation center OA of the developing sleeve 3 is expressed as 2θ,
Assuming that the line segment dividing the angle ZSz OA 5s (2θl) into two equal parts is a dashed-dotted line M, and the intersection of the dashed-dotted line M with the surface of the developing sleeve 3 is Mo, the intersection M0 is the magnetic pole S.
This is the position on the surface of the developing sleeve 3 in the center between z and S (hereinafter, M is simply referred to as the center position of the magnetic pole S2.S).
.

Further, the developing sleeve 3 is connected to the rotation center OA of the developing sleeve 3 and the rotation center O of the elastic roller 7.
X is the intersection with the surface. Then, the intersection point is X.

is the center of the contact position between the elastic roller 7 and the developing sleeve 3.

There is an appropriate contact position between the elastic roller 7 and the developing sleeve 3. Although the present invention is not limited to this, the abutting position is such that the central position x0 is the magnetic pole S2.
Center position M of S3. It is preferable to be located further downstream in the rotational direction of the developing sleeve 3 and upstream of the downstream magnetic pole S3.

To explain the reason for this, in this embodiment, the magnetic poles S,
After the developer 2 is separated to some extent from the developing sleeve 3 by the action of the repelling magnetic field caused by S, the force in the direction of separating the developer 2Δ by the action of the anti-1g magnetic field remains in force, and the elastic roller 7 is Developing sleeve 3 due to sliding force
Since the developer 2 is peeled off and removed from the developer 2, it can be removed very effectively. Therefore, it is naturally important that the contact position between the elastic roller 7 and the developing sleeve 3 is between the magnetic poles S, , S. However, in addition, the center position of the contact position x0
magnetic pole S2. If it is downstream of the center position M0 of S,
After the developer 2 is sufficiently separated from the developing sleeve 3, the elastic roller 7 comes into contact with the developer 2, so that the developer 2 can be effectively peeled off and removed.

Assuming that the center position X0 of the contact position is upstream of the center position M0 of the magnetic poles S2, S, the elastic roller 7 comes into contact with the developer 2 before it is sufficiently separated from the developing sleeve 3. Therefore, the peeling and removal effect of the developer 2 is reduced, and the magnetic pole S2 on the upstream side of the magnetic poles S* and Ss
is located immediately upstream of the contact position, so the developer 2 peeled off and removed by the sliding friction of the elastic roller 7 is
The developer 2 may be attracted by the magnetic pole S2 and stagnate there, resulting in clogging or spillage of the developer 2.

For this reason, it is preferable that the contact position between the elastic roller 7 and the developing sleeve 3 be set downstream of the center position M0 of the magnetic poles S, , S, in the rotational direction of the developing sleeve 3.

Next, the present invention will be further explained using specific examples.

Example 1 An image was formed by developing using the developing device of the example shown in FIG.

Dark potential Vo-700V on photosensitive drum 6, bright potential VL
An electrostatic latent image of the image is formed at -130V, and a frequency of 1800 is applied to the developing sleeve 3 of the developing device using the bias power supply 20.
Development was performed by applying a developing bias in which a direct current of -300 V was superimposed on an alternating current with an amplitude of 1,600 V.

An OPC drum was used as the photosensitive drum 6, and its diameter was 60 mm. A cylindrical body made of Al1 was used as the developing sleeve 3, and its outer diameter was 20 mm.

In the elastic roller 7, an elastic layer 72 was formed using Everite on the outer surface of a shaft 71 made of a non-magnetic SUS material.

Its outer diameter is 16 mm. The elastic roller 7 was brought into contact with the developing sleeve 3 between the magnetic poles S- and Ss of the magnetic roller 4 and on the downstream side in the rotational direction of the developing sleeve 30 from the center position M0 of the magnetic pole S-1Ss. The nip width of the contact part is 4
It is mm. The direction of rotation of the elastic roller rough was one direction counter to the direction of rotation of the developing sleeve 3.

The magnetic roller 4 used had magnetic poles S and S both having a diameter of 600 Gauss.

The distance g between the developing sleeve 3 and the magnetic blade 5 is 240μ.
m1 The distance g between the developing sleeve 3 and the photosensitive drum 6 is 30
0 μm, and the circumferential speed of the photosensitive drum 6 was 21.1 mm/sec.
The circumferential speed of the developing sleeve 3 is 211 mm/sec, and the elastic roller 7 is
The circumferential speed was 211 mm/sec.

Developer 2 contains 6 magnetic particles in 100 parts of binder resin.
A magnetic toner containing 0 parts and an average particle size of 12 μm was used.

First, in order to provide an image history on the photoreceptor drum 6, the image is a black band image (
forming and printing an image having a white band image (adding an image history of image formation) and a white band image (adding an image history of non-image formation);
After printing 30 sheets of this, character images and halftone images were formed and printed. Then, it was investigated whether or not there was a difference in image density etc. due to the difference in image history between one image formation and one image non-formation for these character images and halftone images.

As a result, as shown in Table 1, the images were good, with little or no difference in image density for both character images and halftone images.Also, there was no developer clogging or spillage. .

Comparative Example 1 For comparison, an image was formed by developing using another conventional developing device shown in FIG.

This developing device differs from the conventional developing device shown in FIG. 8 in that it does not have a scraper 12, and also differs from the developing device of the embodiment shown in FIG. 1 in that it does not have an elastic roller 7 and a magnetic plate 8. They differ in some respects.

Other conditions were the same as in Example 1 to form an image.

As a result, as shown in Table 1 above, due to the difference in the image history of the photoreceptor drum 6, there was a significant difference in image density, and the difference in character images was also significant, and both images were difficult to see.

Note that the image in this comparative example has a higher density at a portion corresponding to a portion where there is an image history of image formation on the photoreceptor drum 6 than a portion corresponding to an image history portion where no image is formed. (The letters became thicker.

Comparative Example 2 In this comparative example, the conventional developing device shown in FIG. 8 was used. This developing device does not have the elastic roller 7 and magnetic plate 8 of the developing device of the embodiment shown in FIG. 1, but is provided with a scraper 12 as a mechanical developer removing means instead. Other conditions were the same as in Example 1 to form an image.

As a result, as shown in Table 1 above, although the influence of the difference in image history on the photoreceptor drum 6 was almost eliminated, the developing sleeve 3 was worn out by the scraper 12 due to long-term use. Since the surface shape of the developing sleeve 3 changed, the image properties changed, and image unevenness sometimes occurred in a low-temperature environment of 15° C. and 10% and low humidity.

In addition, the scraper 12 is worn out and the scraper spring becomes loose.
There were cases where black and white streaks appeared on the image. Furthermore, since the developer 2 that was peeled off and removed by the scraper 12 remained at the scraper 12, a window was provided in the scraper 12 to allow the developer 2 to pass through in order to prevent the developer 2 from agglomerating. However, when the formed image is a halftone image, the image portion corresponding to the portion of the developing sleeve 3 where the window of the scraper 12 is located and the image portion corresponding to the portion of the developing sleeve 3 where there is no window are as follows. A slight difference in concentration occurred.

Comparative example 3 In this comparative example, a comparative developing device shown in FIG. 10 was used.

The magnetic roller 4 in this developing device has magnetic poles N1. St
, Nx, S-, Ns, S-, and the same magnetic pole S3 is located at almost the same position as the magnetic pole S3 of the magnetic roller 4 in the developing device of the embodiment shown in FIG. A different pole N3 is located at approximately the same position. In this developing device, there is a contact position of the elastic roller 7 with the developing sleeve 3 between the different magnetic poles N, , S, and the same magnetic poles S, , S as in the developing device shown in FIG. , there is no interval. Another difference is that the shape of the hopper 1 has almost no space below the above-mentioned abutting position, and that there is no pumping member 9.

Other conditions were the same as in Example 1 to form an image. As a result, as shown in Table 1 above, the white sushi image had unevenness and was difficult to see.

That is, the developer 2 stays and aggregates below the contact position of the elastic roller 7 with the developing sleeve 3, resulting in a white streak image, and the developer 2 sometimes spills from the hopper 1.

This is because the developer 2 peeled off and removed from the developing sleeve 3 at the contact position of the elastic roller 7 with the developing sleeve 3 does not form a flow path to move into the hopper 1. It is thought that the particles accumulated and agglomerated.

Comparative Example 4 In this comparative example, another comparative developing device shown in FIG. 11 was used. Similar to Comparative Example 3, this developing device has magnetic poles N and S.
, , Ni, S, , N3, S, there is a contact position between the magnetic poles Ns and Ss of the magnetic roller 4 with the developing sleeve 3 of the elastic roller rough. There are no magnetic poles S, S, of the same polarity as in the developing device.

The other aspects of this developing device are basically the same as the developing device shown in FIG.

When an image was formed under the same conditions as in Example 1, as shown in Table 1, a slight difference in density occurred in the halftone image.

That is, since the contact position of the elastic roller 7 with the developing sleeve 3 is between the magnetic poles S2 and Sx of the same polarity (between the magnetic poles Ni and Sx of different polarity, the developer 2 is not drawn by the magnetic field at this contact position). This is thought to be because the force for separating is not applied, and therefore the effect of separating and removing the developer 2 on the surface of the developing sleeve 3 is reduced.

This is thought to be due to a reduction in the effect of

Example 2 An image was formed by developing using a developing device according to another example of the present invention shown in FIG. The developing device of this embodiment has basically the same configuration as the developing device of the embodiment shown in FIG. 1, except that there is no pumping member 9, and in FIG. The same reference numeral indicates the same member.

When an image was formed under the same conditions as in Example 1, as shown in Table 1, a good image was obtained that was not affected by the difference in image history on the photoreceptor drum 6, and It's clogged! No damage occurred.

However, in this embodiment, there is no problem as long as there is enough developer 2 in the hopper 1, but if the amount of developer 2 is small (
Then, since there is no pumping member, the developer 2 is no longer supplied to the developing sleeve 3, and therefore, it becomes necessary to replenish the developer 2 into the hopper 1 earlier than in the first embodiment.

Example 3 An image was formed by developing using a developing device according to still another example of the present invention shown in FIG. The developing device of this embodiment differs from the developing device of the embodiment shown in FIG. 1 in that the lower part of the hopper 1 is wider and a wider space is created below the contact position of the elastic roller 7 with the developing sleeve 3. , two pumping members 9A and 911 are provided in the hopper l, and the magnetic pole configuration of the magnetic roller 4 is N, S, N,
, N, , S, except that the contact position of the elastic roller 7 is between the magnetic poles N* and Ns of the same polarity. The other configuration is basically the same as that of the developing device shown in Fig. 1.
In the drawings, the same reference numerals as in FIG. 1 indicate the same members.

When images were formed under the same conditions as in Example 1, the same excellent effects as in Example 1 were obtained as shown in Table 1. In particular, in this embodiment, since a wide space is formed below the contact position of the elastic roller 7 with the developing sleeve 3 in the hopper 1, a more excellent effect is achieved in preventing clogging and spillage of the developer 2. It was played.

Example 4 An image was formed by developing using a developing device according to another example of the present invention shown in FIG. The developing device of this embodiment is different from the developing device of the embodiment shown in FIG.
The major difference is that the members constituting the developing device including the developing sleeve 3 are arranged below the photosensitive drum 6. The hopper 1 in this developing device is a box with an open top, and there is a wide space below the contact point of the elastic roller 7 that contacts the developing sleeve 3 disposed at the top from below. 2
pumping members 9A, 9. is provided. The other configurations are basically the same, and the same reference numerals in FIG. 5 as in FIG. 1 indicate the same members.

When images were formed under the same conditions as in Example 1, the same excellent effects as in Example 1 were obtained as shown in Table 1. In addition, since a wide space is formed below the contact position of the elastic roller rough with the developing sleeve 3 in the hopper 1, similar to the case of Embodiment 3, it is more effective in preventing clogging and spilling of the developer 2. The effect was achieved.

Example 5 An image was formed by developing using a developing device according to still another example of the present invention shown in FIG. In the developing device of this embodiment, an elastic blade 10 is used as the developer regulating member in place of the magnetic blade 5 in the developing device of the embodiment shown in FIG. The feature is that the counter is brought into contact with the counter in one direction. The rest of the structure of this developing device is similar to that of the developing device of the embodiment shown in FIG. 1, and the same reference numerals in FIG. 6 as in FIG. 1 indicate the same members.

As the elastic blade 10, a blade made of silicone rubber, urethane rubber, etc. can be used. In this example, an elastic blade made of urethane rubber with a hardness of 67 degrees and a thickness of 2 mm was used, and its free length was 10 mm.

When images were formed under the same conditions as in Example 1, the same excellent effects as in Example 1 were obtained as shown in Table 1.

In this example, there was no scattering of the image (the image was clear, which was particularly favorable for improving the image quality. The reason for this is that the elastic blade 10 rubs the developer 2 strongly, so that the developer 2 This is thought to be due to increasing the triboelectric charge.

Further, in this embodiment, since the elastic blade 10 is brought into contact with the counter in one direction, there is also an effect of reducing the torque compared to the case where it is in the forward direction.

Example 6 An image was formed by developing using a developing device according to still another example of the present invention shown in FIG.

In the developing device of this embodiment, as in the fifth embodiment, an elastic blade 10 was used in place of the magnetic blade 5 in the developing device of the embodiment shown in FIG. The feature is that the contact is made in the forward direction with respect to the rotational direction of , contrary to the fifth embodiment. The rest of the structure of this developing device is similar to that of the developing device of the embodiment shown in FIG. 1, and the same reference numerals in FIG. 7 as in FIG. 1 indicate the same members.

As in the case of Example 6, the elastic blade 10 was made of urethane rubber with a hardness of 67 degrees and a thickness of 2 mm, and the free length was similarly set to 10 mm.

When images were formed under the same conditions as in Example 1, the same excellent effects as in Example 1 were obtained as shown in Table 1.

In this example as well, the image was clear with no image scattering, and was particularly favorable for improving image quality. The reason for this is thought to be that, as described above, the triboelectric charge of the developer is increased by strongly rubbing the developer 2 with the elastic blade 10.

In all of the above embodiments, a developing bias is applied to the developing sleeve 3 in the form of superimposing a direct current on an alternating current, but it is also possible to use only a direct current as the developing bias. Furthermore, an example has been shown in which the developer 2 on the developing sleeve 3 is electrostatically caused to jump or extend without contacting the photosensitive drum 6, but the developer 2 on the developing sleeve 3 is not in contact with the photosensitive drum 6. The present invention can also be applied to the case where development is performed by rubbing against the drum 6.

Further, the developer supporting means is not limited to the cylindrical developing sleeve 3, but may be configured to adopt a developer conveying form using an endless belt, or may be configured by an elastic roller.

1 As described above, in the present invention, the one-component magnetic developer contained in the developer container with built-in developer supply means is developed by the magnetic force of the magnetic field generation means installed in the developer support means. while controlling the coating layer thickness of the developer on the developer supporting means with a regulating member;
In the developing device, the developer is conveyed by the developer support means to a development position opposite to the latent image support means, and the latent image formed on the latent image support means is developed with the developer. A position between two magnetic poles of the same polarity, which are located upstream of the regulating member and downstream of the development position with respect to the moving direction of the developer supporting means, among the magnetic poles provided in the developer supporting means. Since an elastic roller is provided which rotates in contact with the developer supporting means, it is effective to obtain a good image regardless of the difference in image history.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of the developing device of the present invention. FIG. 2 is an explanatory diagram for explaining the contact position between the elastic roller and the developing sleeve. FIG. 3 is a sectional view showing another embodiment of the developing device of the present invention. FIG. 4 is a sectional view showing still another embodiment of the developing device of the present invention. FIG. 5 is a sectional view showing another embodiment of the developing device of the present invention. FIG. 6 is a sectional view showing still another embodiment of the developing device of the present invention. FIG. 7 is a sectional view showing still another embodiment of the developing device of the present invention. FIG. 8 is a sectional view showing a conventional developing device. FIG. 9 is a sectional view showing another conventional developing device. FIG. 10 is a sectional view showing a comparative developing device. FIG. 11 is a sectional view showing another comparative developing device. 2: 3: 4: 5 Near: 8: 1 O Near 2. S 2 , N 2 , one-component magnetic developing agent Developing sleeve Magnet roller Magnetic blade Elastic roller Magnetic plate lifting member Elastic blade Elastic layer S3: Two magnetic poles of the same polarity N3 Two magnetic poles of the same polarity L: Hopper Fig. Figure 3 Figure 2 Figure 4 Figure 7 Figure 6 Figure 8 Figure 9 Figure 10

Claims (1)

[Claims] 1) A one-component magnetic developer contained in a developer container with a built-in developer supply means is supported on the developer support means by the magnetic force of a magnetic field generating means installed in the developer support means, and the developer is supported. transporting the developer by the developer support means to a development position facing the latent image support means while regulating the thickness of the coating layer of the developer on the means by a regulating member;
In a developing device that develops a latent image formed on the latent image supporting means with the developer, one of the magnetic poles provided on the magnet is located upstream of the regulating member with respect to the moving direction of the developer supporting means. Further, an elastic roller is provided in the developer container and rotates in contact with the developer support means at a position between two magnetic poles of the same polarity located downstream of the development position. Developing device.