JPH0943977A - Development device - Google Patents

Abstract

(57) [Summary] [Object] The present invention can maintain image stability from the initial stage of image formation to the long-term image formation, even when the above-described fine particles and rapid melting toner are used. It is an object of the present invention to provide a developing device capable of preventing the blotch phenomenon with a light load on the toner, keeping a thin toner layer on the developing sleeve and maintaining a high charge amount for a long period of time. [Structure] The magnetic blade 5 is in the first quadrant in the coordinate plane formed by a horizontal line and a vertical line passing through the rotation center O ₁ of the developing sleeve 3, and is opposite to the free end of the magnetic blade 5 which is close to the developing sleeve 3. The fixed end supported by the developing container 2 is disposed in a state of being inclined toward the upstream side in the rotation direction of the developing sleeve 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device used for developing a latent image formed on an image carrier in a copying machine, an image forming / recording apparatus, a printer, a facsimile, etc., and more particularly to a developer. The present invention relates to an arrangement position of a regulation member in a developing device having a developer supply roller that rotatably contacts a carrier.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, an image forming / recording apparatus, a printer or a facsimile, a latent image formed on an image carrier made of an electrophotographic photoreceptor or an electrostatic recording dielectric is developed. It is developed by a device and visualized as a toner image.

As one of such developing devices, various dry single-component developing devices have been proposed and put into practical use.
However, in any of the developing devices, it is extremely difficult to form a thin layer of toner, which is a one-component developer, on the developer carrying member. However, at the present time when improvement in image sharpness and resolution is required, development of a toner thin layer forming method and its apparatus is indispensable, and in response to this, some measures have been proposed.

For example, a developing sleeve which uses a magnetic toner and has a smooth surface having relatively smooth unevenness by blasting with fixed particles, and a magnetic blade which is arranged with a gap therebetween are provided. By using it, it is possible to form a thin layer of toner to which an appropriate electric charge has been applied, on the developing sleeve.

By the way, it is attempted to make the toner having a small particle diameter and a low melting point for the purpose of further improving the image quality and quick start of the copying operation. However, this toner has a higher aggregation degree than the conventional toner. . For this reason, toner blocking is likely to occur near the magnetic blade, and in a high humidity environment, an image with a lot of unevenness and fog may occur. In a low-quality environment, in addition to blocking, local toner aggregation and sticking occur on the developing sleeve due to charge-up (blotching phenomenon), which may appear as fogging or uneven density on the image. is there.

As a countermeasure against the above, Japanese Patent Publication No. 63-1673.
In Japanese Patent Laid-Open No. 6 and the like, an elastic blade made of rubber, resin, or metal is brought into light contact with the developing sleeve as a developer regulating member, and the toner stuck on the developing sleeve is peeled off at the contact portion to regulate. According to this, it becomes possible to form a uniform thin toner layer, and by applying the triboelectric charge from the blade, both the upper layer and the lower layer of the toner layer on the developing sleeve have sufficient electric charge. As a result, a good image without unevenness and fog can be provided.

As another measure, an open-cell polyurethane foam roller (sponge roller) that rotates in contact with the developing sleeve at a position upstream of the developing sleeve proximity portion of the magnetic blade in the developing sleeve rotation direction, or a fur. By disposing a roller having a brush structure, the toner stuck on the developing sleeve is swung at its contact portion so that the toner is easily separated from the developing sleeve and at the same time, triboelectric charge is applied to the toner. Further, the toner blocked in the vicinity of the blade is loosened by the rotation of the roller to maintain good fluidity. As a result, it is possible to provide a good image without blotches, unevenness, fog, etc., as in the case of using an elastic blade.

However, the above two measures (when using an elastic blade, when using a roller such as an open-celled sponge)
However, if the continuous copying operation for tens of thousands of sheets is performed, the following problems occur during the latter half of the copying operation and during toner replenishment.

(1) Due to local clogging of toner agglomerates at the contact portion between the elastic blade and the developing sleeve, uneven application of toner occurs on the developing sleeve.

(2) Toner is fused to the contact surface of the elastic blade with the developing sleeve, and the ability of the elastic blade to impart triboelectric charge to the toner is reduced.

(3) The continuous foam sponge roller is hardened due to the clogging of the toner, which causes the toner application to the developing sleeve, the reduction of the scraping force, and the fraying of the sponge roller.

As a means for solving these problems, Japanese Patent Application No. 5-20
A developing device as disclosed in Japanese Patent No. 4562 has been proposed. In this developing device, as shown in FIG. 5, as the toner supply roller arranged in the vicinity of the magnetic blade, a single-foam foam rubber without clogging of toner inside is used.
Compared to the open-cell rubber roller, even if the amount of invasion of the supply roller into the developing sleeve is the same, the substantial contact area increases, and as a result, toner is applied to and scraped from the developing sleeve, and charge is imparted to the toner. Even in the copying operation of tens of thousands of sheets, it can be maintained well.

[0013]

In recent years, the digitization of electrophotography and the compounding of copying machines, facsimiles, and printers have progressed in recent years, so that toner used for development faithfully reproduces a minute dot latent image by laser irradiation or the like. 6 to reproduce
Fine particles having a size of μm or less, or particles having a spherical shape in addition to the particles, or particles capable of being melted more rapidly to meet the on-demand system have been used.

However, when such a toner is used to drive the developing device having the above-described structure in a low-quality environment to start copying, the above-mentioned blotch phenomenon may occur instantly in the entire developing sleeve. It was

Therefore, in order to prevent this phenomenon, the contact nip width of the single-foam supply roller with respect to the developing sleeve may be increased to enhance the scraping effect of blotch toner adhered to the developing sleeve. was suggested.

As a result, the blotch phenomenon is reduced and a good toner thin layer is formed on the developing sleeve. However, when tens of thousands of images are printed with this configuration, the density on the image gradually decreases, Fog was sometimes noticeable.

The cause of this is that the width of contact between the supply roller and the developing sleeve is increased, so that the load on the toner is increased, and the external additive may be embedded or the shape may be easily changed. As a result, it seems that the physical properties such as the charge amount changed.

Therefore, according to the present invention, even when the above-mentioned fine particles and rapid melting toner are used as described above, the stability of the image can be maintained from the initial stage of image formation to the state after long-term image formation. On the other hand, a light load can prevent the blotch phenomenon,
Another object of the present invention is to provide a developing device in which the toner on the developing sleeve is made thin and the charge amount is kept high for a long period of time.

[0019]

According to the first invention of the present application, the object is to carry the supplied one-component magnetic developer and rotate the developer so that the developer is opposed to the image carrier. And a developer carrying body that contains a magnetic field generating means having a plurality of magnetic poles and is conveyed close to the surface of the developer carrying body on the upstream side of the developing area with respect to the rotation direction of the developer carrying body. A magnetic plate-shaped regulating member that regulates the amount of the developer carried on the developer carrying member, and the developer carrying member that is in contact with the developer carrying member on the upstream side of the regulating member and rotates in the same direction. In a developing device having a supply roller for stripping and supplying a developer to and from a carrier, at least the surface of which comprises a foamed foam, a horizontal line passing through the rotation center of the developer carrier is used as the regulating member. And a vertical line is formed In the first quadrant in the coordinate plane, the fixed end of the regulating member, which is opposite to the free end of the regulating member and is close to the developer carrying member, is disposed in a state of being inclined toward the upstream side in the rotation direction of the developer carrying member. It

According to the second aspect of the present invention,
In the first aspect of the invention, the angle θ ₁ formed by the straight line passing through the center of rotation of the developer carrier and the free end of the regulating member and the vertical line satisfies 20 ° ≦ θ ₁ ≦ 70 °. Achieved by

Further, according to the third invention of the present application,
In the first or second aspect of the invention described above, the rotation center of the supply roller is located below the rotation center of the developer carrier, and the free end of the proximity member of the regulating member with respect to the developer carrier is located. The angle θ ₂ between the center and the center of the contact portion of the supply roller with respect to the rotation center of the developer carrier is 6
It is achieved by satisfying 0 ° ≦ θ ₂ ≦ 90 °.

According to a fourth aspect of the present invention,
The above object is achieved in any one of the first to third inventions, wherein the surface of the developer carrying member has a pseudo mirror surface which is not roughened by abrasive grains or the like.

Further, according to the fifth invention of the present application,
In the object of any one of the first to fourth inventions, the contact width of the supply roller with the developer carrying member is 0.5 to 6.0 mm, and the density of the supply roller is 0.1.
5 to 0.35 g / cm ³ , piece hardness is Asker C, 3
It is achieved by setting a load of 00 g to 8 ° to 30 ° and a cell number of 100 to 400 cells / inch ² .

[0024]

As described above, according to the first invention of the present application, the regulating member is the first quadrant in the coordinate plane formed by the horizontal line and the vertical line passing through the rotation center of the developer carrier. ,
Since the fixed end of the regulating member opposite to the free end close to the developer carrying member is disposed in a state of being inclined to the upstream side in the rotation direction of the developer carrying member, the facing gap portion between the regulating member and the developer carrying member is provided. In the above, since the component of gravity acting on the magnetic developer toward the center of the developer carrier is smaller than before, the adhesive force of the magnetic developer to the developer carrier is reduced, and the blotch phenomenon is significantly reduced. It Further, since the fixed end side of the regulating member is inclined to the upstream side in the rotation direction of the developer carrier with respect to the free end side, the developer conveyed near the regulating member is more likely to return to the inside of the developing container as compared with the conventional example, that is, circulates. As a result, the degree of cohesion does not rise and good fluidity is maintained, so the force pushing the ears in the gap between the regulating member and the developer carrier does not increase, and from this point also the blotch is reduced. Let

According to the second invention of the present application,
In the first aspect of the present invention, since the angle θ ₁ formed by the straight line passing through the rotation center of the developer carrier and the free end center of the regulating member and the vertical line is larger than 20 °, the gravity component is reduced to cause the blotch phenomenon. Suppress the occurrence of. Further, since it is 70 ° or less, the amount of developer conveyed to the facing gap between the regulation member and the developer carrier does not decrease excessively, unevenness does not occur in the longitudinal direction, and further, at the supply roller contact portion. The developer is not overloaded.

Further, according to the third invention of the present application,
In the first invention or the second invention, the center of rotation of the supply roller is located below the center of rotation of the developer carrier, and the center of the free end of the proximity portion of the regulating member to the developer carrier and the supply roller. The angle θ ₂ with respect to the center of the contact portion of the developer carrier with respect to the rotation center of the developer carrier is 60 ° ≦ θ ₂ ≦ 90 °
Since the above condition is satisfied, the developer that has returned to the developer container without passing through the gap between the regulation member and the developer carrier stagnates while smoothly replacing with the new developer sent from the developer container. It was found to form a developer circulation without. As a result, the deterioration of the developer and the blotch phenomenon do not occur, and it is possible to always obtain a stable and good image without a decrease in density or fog on the image.

Further, according to the fourth invention of the present application,
In any one of the first to third inventions,
The surface of the developer carrier has a pseudo mirror surface that is not roughened by abrasive particles, but since such a pseudo mirror surface has almost no minute irregularities, it is charged by friction with the developer carrier. The amount is likely to increase, and from that point the blotch phenomenon is likely to occur, but since the developer carrying force on the developer carrier is reduced, the developer in the vicinity of the facing gap between the regulation member and the developer carrier is reduced. This is offset by the reduction of excessive clogging.

Further, according to the fifth invention of the present application,
In any one of the first to fourth inventions,
Since the contact width of the supply roller with the developer carrying member is 0.5 mm or more, uneven coating of the developer does not occur, and since it is 6.0 mm or less, the fusion of the developer to the developer carrying member and the deterioration of the developer characteristics are caused. And drive torque does not increase. Furthermore, the density of the supply roller is a 0.15 g / cm ³ or more, bleeding of low-molecular oil is not generated from the supply roller, it by the developer carrying member contamination hardly occurs, 0.35 g / cm ³
Because of the following, the excessive contact pressure of the supply roller does not cause the fusion of the developer on the developer carrier, the deterioration of the developer characteristics, and the increase of the driving torque of the developer carrier. Further, since the piece hardness is 8 ° or more under Asker C and a load of 300 g, exudation of low-molecular oil does not occur from the supply roller, and the developer carrier is less likely to be contaminated due to it, and the supply roller is 30 ° or less. The excessive contact pressure does not cause the fusion of the developer on the developer carrier, the deterioration of the developer characteristics, and the increase in the driving torque of the developer carrier. 100 cells /
Since it is at least ² inches, the low molecular oil does not seep out from the supply roller, and it is difficult for the developer carrier to contaminate. 400 pieces / inch ² or less, so the contact pressure of the supply roller is too large to develop. It does not cause the fusion of the developer on the developer carrier, the deterioration of the developer characteristics, and the increase of the driving torque of the developer carrier.

[0029]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a schematic sectional view showing an embodiment of the developing device of the present invention. In FIG. 1, reference numeral 2 denotes a developing container containing a magnetic toner 7 which is a one-component developer, and the present developing device has a developing sleeve 3 as a developer carrying member in the developing container 2. The developing sleeve 3 is arranged so as to face the photosensitive drum 1 rotating in the direction of the arrow a in the figure, conveys the toner 7 in the container 2 to a developing area facing the photosensitive drum 1, and forms a static toner on the photosensitive drum 1. The latent image is visualized as a toner image by developing the latent image.

The photosensitive drum 1 is, for example, a so-called xerographic photoreceptor which forms an electrostatic latent image by the Carlson process, and the NP process having an insulating layer on the surface described in JP-A-42-23910. A photoconductor on which an electrostatic latent image is formed, an insulator on which an electrostatic latent image is formed by an electrostatic recording method, an insulator on which an electrostatic latent image is formed by a transfer method, and an electrostatic latent image (potential) by another appropriate method. A member forming a latent image) is used.

The developing container 2 has an opening extending in the longitudinal direction of the apparatus (direction perpendicular to the paper surface of FIG. 1), and the developing sleeve 3 is installed in the opening. Developing sleeve 3
Is made of a material such as aluminum or SUS. The developing sleeve 3 has a substantially semi-peripheral surface to the right of the container 2
It projects inwardly, exposes a substantially left half peripheral surface to the outside of the container 2, and is rotatably provided laterally so as to face the photosensitive drum 1. A slight minute gap is provided between the developing sleeve 3 and the photosensitive drum 1, and the developing sleeve 3 is rotationally driven in the arrow b direction with respect to the rotational direction a of the photosensitive drum 1.

The developer carrying member is not limited to a sleeve-like cylindrical body such as the developing sleeve 3, but a rotatable endless belt-like member can be used, and a conductive rubber roller is used. You can also

A magnet 4 is provided in the developing sleeve 3 as a magnetic field generating means. In this embodiment, the magnet 4 is a permanent magnet. The magnet 4 is non-rotatably arranged in the developing sleeve 3 so as to generate a fixed magnetic field regardless of the rotation of the developing sleeve 3.

In the vicinity of the developing sleeve 3 in the developing container 2, there is provided a plate-shaped magnetic blade 5 as a developer regulating member, the fixed end of which is supported by the opening of the developing container and the free end of which is opposed to the developing sleeve 3. This magnetic blade 5 is provided
Further, one of the magnetic poles of the magnet 4 is positioned so as to substantially face each other. A toner supply roller 6 is provided at a position upstream of the magnetic blade 5 in the rotation direction of the developing sleeve 3.
Is rotatably installed. According to the present invention, this supply roller 6 has an elastic layer made of closed-cell foam rubber on a cored bar 8. Details of the proximity position of the magnetic blade to the developing sleeve 3 and the like will be described later.

In the developing device having the above structure, the toner supply roller 6 rotates in the same direction as the developing sleeve 3 in the direction of arrow c in the figure, and the rotation of the supply roller 6 causes the magnetic toner 7 in the container 2 to develop. 3, the supply roller 6
The toner 7 is rubbed against the supply roller 6 and the developing sleeve 3 at the nip portion where the developing sleeve 3 and the developing sleeve 3 contact each other.
As a result, the toner 7 is sufficiently triboelectrically charged, and the toner 7 is attached and carried on the developing sleeve 3 by the electrostatic force and the magnetic force of the magnet 4.

The magnetic toner 7 carried on the developing sleeve 3 is then conveyed to the developing sleeve facing portion of the magnetic blade 5 as the developing sleeve 3 rotates. Then, the layer thickness is regulated by the magnetic regulation formed in the gap between the magnetic blade 5 and the developing sleeve 3 to form a thin layer on the developing sleeve 3, and then the regulating portion is pulled out to exit from the photosensitive drum 1.
Then, it is conveyed to a developing area facing each other with a minute gap.
In the developing area, by applying an alternating voltage, which is a direct current and an alternating current, as a developing bias between the developing sleeve 3 and the photosensitive drum 1, the toner 7 on the developing sleeve 3 becomes an electrostatic latent image on the photosensitive drum 1. Transfer and adhere to each other,
The electrostatic latent image is visualized and developed as a toner image.

The toner 7 remaining on the developing sleeve 3 without being consumed for development in the developing area is collected in the container 2 from below the opening of the container 2 as the developing sleeve 3 rotates. The collected toner is peeled off from the developing sleeve 3 by the supply roller 6 at the contact portion. At the same time, new toner 7 is supplied to the developing sleeve 3 by rotation of the supply roller 6, and this new toner is conveyed again to the developing sleeve facing portion of the magnetic blade 5 as the developing sleeve 3 rotates. Most of the peeled toner is conveyed and mixed into the toner in the container 2 by the rotation of the supply roller 6, and the charged electric charge of the peeled toner is dispersed.

Next, the arrangement relationship of the magnetic blades in this embodiment will be described in detail.

In this embodiment, as shown in FIG.
The magnetic blade 5 is in the first quadrant in the coordinate plane formed by the vertical line and the horizontal line passing through the rotation center O ₁ of the developing sleeve, and
The fixed end of the magnetic blade 5 supported by the developing container 2 on the opposite side of the free end adjacent to the developing sleeve 3 is disposed in a state of being inclined toward the upstream side in the developing sleeve rotation direction.

With this configuration, the developing sleeve 3 of the supply roller 6 can be used even when a fine particle toner having a particle size of 6 μm or less is used.
A good toner coating with no blotch phenomenon was formed on the developing sleeve 3 without increasing the contact width with respect to the toner.

In describing this action, the mechanism of occurrence of the blotch phenomenon will be described.

According to the experiments by the present applicants, the blotch phenomenon in which the toner aggregates and adheres in a ripple pattern on the developing sleeve is mainly caused by the gap between the developing sleeve and the magnetic blade (hereinafter referred to as SB.
It was confirmed that this occurs when the balance of the forces acting on the magnetic toner formed by the gap) is lost. That is, the magnetic toner is applied to the surface of the developing sleeve by the magnetic force due to the change in the magnetic field formed by the magnet and the magnetic blade that are opposed to the magnetic blade adjacent portion in the developing sleeve and the electric charge of the magnetic toner in the SB gap passing portion. A uniform magnetic toner layer is formed on the surface of the developing sleeve by the effect of the mirroring force and the electrostatic cohesive force between the magnetic toners. However, if the charge amount of the magnetic toner becomes too high, The image force and the electrostatic cohesive force are increased, and as a result, the magnetic regulation force is relatively reduced, and the magnetic toner is likely to discontinuously aggregate and adhere onto the developing sleeve. This blotch phenomenon is likely to occur particularly at the most downstream portion of the SB gap portion in the developing sleeve rotation direction (where the concentration of magnetic flux is reduced), as shown in FIG.

On the other hand, in addition to the above-mentioned electromagnetic force acting on the magnetic toner, from the experiments of the applicants, the magnitude of the component of gravity acting on the magnetic toner at the SB gap portion toward the developing sleeve center and the SB gap portion It was found that the carrying force of the carried toner is more effective in the blotch phenomenon.

For example, in the case of the magnetic blade position as described in the conventional example, the gravity of the toner in the SB gap portion is entirely directed to the center of the developing sleeve, and as a result,
Gravity is added to the reflection power, which makes it easier to cut the ears.

This phenomenon is more remarkable in a structure in which a large amount of toner is likely to accumulate near the magnetic blade.

However, since the magnetic blade in this embodiment has the above-mentioned positional relationship, the component of gravity acting on the magnetic toner in the SB gap portion toward the center of the developing sleeve becomes smaller than in the conventional case, and The toner on the side closer to the magnetic blade is magnetically regulated well and does not adhere to the developing sleeve, so that the blotch phenomenon is significantly reduced. Further, since the fixed end side of the magnetic blade is inclined to the upstream side in the developing sleeve rotation direction with respect to the free end side, the toner conveyed near the magnetic blade is likely to return to the inside of the developing container as compared with the conventional example, that is, to be easily circulated. As a result, the degree of cohesion does not increase and good fluidity can be maintained, so that the force for pushing the ears of the SB gap portion does not increase, and from this point also, the blotch can be reduced.

It should be noted that there is an angle formed by the vertical line with the magnetic blade proximity portion indicated by θ ₁ in FIG. 1, but according to the experiments by the present applicants, 20 ° ≦ θ ₁ ≦ 70 °, more preferably 35 °. It is preferable that ≦ θ ₁ ≦ 55 °. If it is less than 20 °, the magnitude of the gravity component becomes effective, and at the same time, the degree of cohesion rises, and the blotch phenomenon tends to occur. On the contrary, if it exceeds 70 °, the amount of toner conveyed to the SB gap portion decreases. Excessive or unevenness occurs in the longitudinal direction, resulting in low image density and unevenness. When the angle is in the range of 20 ° to 70 °, the blotch phenomenon can be prevented without overloading the toner at the contact portion of the supply roller, and a thin toner coating that is uniform in the longitudinal direction of the developing sleeve is achieved. .

Next, an experimental example in this embodiment will be described. First, the magnetic blade was 1.0 mm thick, the magnetic plate was spaced 200 μm from the surface of the developing sleeve, and θ ₁ was set to 40 °.

Further, the toner supply roller 6 has a metal cored bar 8 as a spindle, and silicone rubber, EPDM
A rubber layer formed by foaming rubber, CR rubber, neoprene rubber, or the like is provided in a roller shape, and the foaming form is a single foam in which the wall surfaces of adjacent bubble portions are not in communication with each other.

The toner supply roller 6 is in contact with the developing sleeve 3 and is rotationally driven in the direction of arrow c to be rubbed. Further, regarding the contact condition of the supply roller 6, according to the experiment of the present inventor, toner adhesion due to the magnetic force of the magnet,
Also, since the toner can be peeled off by using the strength of the magnetic force on the surface of the developing sleeve, it is necessary to use a conventional developing device that does not use the action of a magnet for supplying and peeling toner, especially a non-magnetic toner. Than the developing device
There is an advantage that the allowable range of the contact condition of the supply roller 6 can be widened or the range can be set so as not to cause harmful effects.

In terms of numerical values, (1) contact width of the supply roller with the developing sleeve = 0.5 to
6.0 mm (2) Rubber density of supply roller = 0.15 to 0.35 g /
cm ³ (3) Hardness of rubber piece of supply roller (Asker C, 30
0 g load) = 8 to 30 ° (4) Number of cells of foaming rubber on the surface of the supply roller = 100 to
It can be 400 / inch ² .

When the contact width of the above (1) becomes smaller than 0.5 mm, toner application unevenness occurs, and conversely 6.0.
If it is larger than mm, the toner is fused to the developing sleeve, the toner characteristics are deteriorated, and the driving torque is increased.
If the rubber hardness of (3) is less than 8 °, the low-molecular oil oozes out from the supply roller, and the developing sleeve is liable to be contaminated by it. If it exceeds 30 °, the supply roller abuts. Too much pressure causes fusion of toner on the developing sleeve, deterioration of toner characteristics, and increase in driving torque of the developing sleeve. The rubber density of (2) and the number of cells of the expandable rubber of (4) are also determined by the same reasoning as above.

As a specific example of the supply roller 6 in this experimental example, an Asker C hardness (300 g load) of 12 ° and a density of 0.25 g / c on a metal cored bar 8 having an outer diameter of 7 mm.
A neoprene rubber single-cell foam having m ³ and 200 cells / inch ² was coated in a roller shape with a thickness of 4 mm. The roller outer diameter is 15 mm. The supply roller 6 was brought into contact with the developing sleeve 3 with a contact width of 3.0 mm.

The developing sleeve 3 has an appropriately roughened and roughened surface to improve the toner carrying property.

Supply roller 6 of single-foam rubber as in the present invention
In a developing device that does not use, the uneven surface on the surface of the developing sleeve cannot be finely divided in order to prevent deterioration of toner transportability and the blotch phenomenon where the toner on the developing sleeve is locally charged up abnormally. ,as a result,
In a high humidity environment, fog may occur due to insufficient triboelectric charge.

In the present invention, due to the position of the magnetic blade on the developing sleeve and the action of the supply roller 6 which is a single-foam rubber roller, even if the surface roughness of the developing sleeve 3 is made fine, the blotch phenomenon is surely achieved. Since it can be prevented and the mechanical adhesion of the toner to the developing sleeve 3 is also improved,
Since there is no reduction in the carrying force and therefore the performance of imparting the charged electric charge is further improved, the surface roughness of the developing sleeve 3 can be made fine.

The rough surface of the developing sleeve 3 is
It can be obtained by sandblasting the surface of the developing sleeve with irregular-shaped alundum abrasive grains or by sandblasting with regular glass beads so that the surface roughness Rz becomes 1 to 3 μm. Alternatively, by using conductive particles such as particles of metal oxide, graphite, or carbon, which can independently form the convex portion, a convex convex surface is formed on the surface of the developing sleeve, and the convex convex surface is formed. It is also possible to bind the particles with a binder resin such as a phenol resin or a fluororesin to form recesses on the surface of the binder resin, thereby obtaining a rough surface on the surface of the developing sleeve.

In the present experimental example, specifically, the developing sleeve 3 uses a SUS sleeve having a diameter of 20 mm as a substrate, and the surface of the developing sleeve 3 is subjected to a blasting treatment with regular glass beads (# 400) to obtain a surface roughness. Rz is about 2.0 μm
And

Further, the magnet 4 according to the present embodiment.
Has an outer diameter of 16 mm and four magnetic poles. Magnet 4
One of the magnetic poles of is facing the magnetic blade 5,
The peak value of the magnetic flux density is 1000 Gauss, and the full width at half maximum is 40 °. The magnet 4 may be replaced with a permanent magnet and an electromagnet may be used.

The magnetic toner 7 is made by dispersing a magnetic material such as ferrite in a thermoplastic resin such as styrene resin, acrylic resin or polyester resin. In this embodiment,
As the magnetic toner 7, a toner powder made of polyester resin and a magnetic material having an average particle size of 5.5 μm and externally added with 1.5% of colloidal silica was used.

In the present embodiment, the developing device having the above-described structure is incorporated in a GP-55 copying machine manufactured by Canon Inc., and a bias power source has a DC voltage of -550V superimposed on an AC voltage of frequency 2000Hz and a peak / peak voltage of 1400V. The surface potential of the latent image on the photosensitive drum 1 is set to -700 V for the dark portion and -250 V for the dark portion, and the gap between the developing sleeve 3 and the photosensitive drum 1 is set to 300 μm. FIG. 3 shows changes in the solid density and the reflectance of toner adhesion (fogging) to the non-image portion when the copying operation of No. 2 is performed. As a comparative example, the above-mentioned θ1 is 0 ° and the contact width between the supply roller and the developing sleeve is 8.0 mm,
Further, the results when θ ₁ is 90 ° are also shown in FIG.

As shown in FIG. 3, in this embodiment, the blotch phenomenon did not occur, and both the density and the fog were good. In the comparative example, a minute blotch phenomenon, a decrease in density due to toner deterioration, and fog and unevenness in density decrease due to toner conveyance failure were caused.

Further, when the developing device was used to continuously form an image on 1,000,000 sheets while replenishing the toner every 4000 sheets, a uniform thin toner layer could be satisfactorily formed on the developing sleeve. From the final image including the image at the time of replenishment, a good image having a reflection density of 1.4 and free from fog and uneven density was obtained. The charge amount of the toner was consistently −15 μC / g to −20 μC / g, which was a sufficient value.

(Second Embodiment) In addition to the first embodiment, the second embodiment is characterized in that the positional relationship between the magnetic blade 5 and the toner supply roller 6 is defined.

That is, in this embodiment, as shown in FIG. 4, the rotation center O ₂ of the supply roller 6 is located below the rotation center O _{1 of the} developing sleeve 3 and the developing sleeve 3
A straight line g passing through the center D of the magnetic blade 5 close to (opposing) and the rotation center O ₁ of the developing sleeve, and the center E of the contact portion of the supply roller 6 against the developing sleeve 3 and the rotation center O ₁ of the developing sleeve. The angle formed by the straight line h is θ ₂ . This angle θ ₂ was set in the range of 60 ° ≦ θ ₂ ≦ 90 °.

With this configuration, the magnetic toner 7 sent from the developing container 2 to the vicinity of the supply roller 6 is then rotated by the supply roller 6, the rotation of the developing sleeve 3, and the magnetic force exerted by the magnet 4 in the developing sleeve 3. And magnetic blade 5
Due to magnetic restrictions in the vicinity of the magnetic blade 5
2 is divided into one that passes through the gap of the developing sleeve 3 and is used for development in the developing region, and one that forms a circulation without passing through the gap as indicated by an arrow d in FIG.

If this circulation is a small circulation in the vicinity of the developing sleeve 3 on the supply roller 6, the load on the toner becomes excessive and the toner is deteriorated. On the other hand, when the toner does not circulate and stays, the toner is clogged in the vicinity of the developing sleeve 3 to increase the toner aggregation degree in the vicinity of the blade and cause the blotch phenomenon.

According to the experiments by the present inventor, as described above,
When 60 ° ≦ θ ₂ ≦ 90 ° is set, the toner returned to the inside of the container 2 without passing through the gap of the magnetic blade 5 is smoothly replaced with new toner sent from the container 2 and stays there. Without forming a toner circulation. As a result, it was found that the toner deterioration and the blotch phenomenon did not occur, and a good image without density reduction and fog on the image was always obtained stably.

[0070] At this time, the relationship between the outer diameter R ₂ of the outer diameter R ₁ and the developing sleeve 3 of the supply roller 6, when the 0.5 R ₂ ≦ R ₁ ≦ R _2, above the toner circulation can be better formed It

When R ₁ <0.5R ₂ , the influence of the rotation of the supply roller 6 is reduced and the toner circulation is delayed. On the contrary, when R ₁ > R ₂ ,
Toner circulation tends to be small and closed, resulting in
This causes toner deterioration.

(Third Embodiment) The present embodiment is characterized in that the surface of the developing sleeve is a pseudo mirror surface. Other configurations of the present embodiment can be the same as those of the first and second embodiments.

That is, in this embodiment, the developing sleeve 3
Is a developing sleeve in which the surface of the sleeve substrate is not subjected to roughening treatment with abrasive grains or the like, and a pseudo mirror surface is formed by surface polishing. Specifically, a SUS pipe was used as the developing sleeve substrate, and a pseudo mirror surface having a roughness Rz≈1.0 μm was formed by grinder polishing.

With such a pseudo mirror surface, since there is almost no minute unevenness, the amount of charge due to friction with the developing sleeve is apt to increase, and from that point, the blotch phenomenon is likely to occur, but the toner is conveyed on the developing sleeve. Since the force is reduced, the excessive clogging of the developer in the vicinity of the SB gap portion is reduced to be offset. Further, since the positional relationship of the magnetic blades is the same as that of the configuration of the first embodiment, the blotch phenomenon is reduced. Further, since there is no minute unevenness, there is an effect that the scraping efficiency of undeveloped toner, particularly fine toner powder, on the contact portion of the toner supply roller is significantly improved.

[0075]

As described above, the first embodiment according to the present application is described.
According to the invention, a one-component developer is used, a fixed end of which is supported by the opening of the developing container, and a free end of the other end of which is in close proximity to the developer carrier, and a plate-like regulating member, Also in a developing device having a supply roller made of a single-foamed foam rubber that is rotatably brought into contact with the developer carrying member on the upstream side in the rotation direction of the developer carrying member, the position and the development of the free end of the regulating member with respect to the developer carrying member By optimizing the angle formed by the vertical line passing through the center of the agent carrier, the blotch phenomenon can be prevented without widening the contact width of the supply roller. In addition, the angle between the developer bearing member contact position of the supply roller and the proximity position of the regulating member, the surface shape of the developer bearing member, and the like are optimized, and the developer on the developer bearing member is thinned. Layering and a high charge amount can be maintained for a long period of time, and it is possible to stably provide a good image without density reduction, fog, and unevenness on the image.

According to the second aspect of the present invention,
In the first aspect of the invention, since the angle θ ₁ formed by the straight line passing through the rotation center of the developer carrier and the free end center of the regulating member and the vertical line is larger than 20 °, the gravity component is reduced to cause the blotch phenomenon. Can be suppressed. Also,
Since it is 70 ° or less, the amount of developer conveyed to the facing gap between the regulation member and the developer carrier does not decrease too much, and it is possible to suppress the occurrence of unevenness in the longitudinal direction. Thus, it is possible to prevent the developer from being overloaded.

Further, according to the third invention of the present application,
In the first invention or the second invention, the center of rotation of the supply roller is located below the center of rotation of the developer carrier, and the center of the free end of the proximity portion of the regulating member to the developer carrier and the supply roller. The angle θ ₂ with respect to the center of the contact portion of the developer carrier with respect to the rotation center of the developer carrier is 60 ° ≦ θ ₂ ≦ 90 °
Since the above condition is satisfied, the developer that has returned to the developer container without passing through the gap between the regulation member and the developer carrier stagnates while smoothly replacing with the new developer sent from the developer container. The developer circulation can be formed without any.
As a result, the deterioration of the developer and the blotch phenomenon do not occur, and it is possible to always stably obtain a good image without density reduction and fogging on the image.

According to the fourth aspect of the present invention,
In any one of the first to third inventions,
The surface of the developer carrier has a pseudo mirror surface that is not subjected to roughening treatment with abrasive particles, etc., but since such a pseudo mirror surface has almost no minute unevenness, it is charged by friction with the developer carrier. The amount is likely to increase, and from that point the blotch phenomenon is likely to occur, but since the developer carrying force on the developer carrier is reduced, the developer in the vicinity of the facing gap between the regulation member and the developer carrier is reduced. This can be offset by reducing excessive clogging.

Further, according to the fifth invention of the present application,
In any one of the first to fourth inventions,
Since the contact width of the supply roller with the developer carrying member is 0.5 mm or more, uneven coating of the developer does not occur, and since it is 6.0 mm or less, the fusion of the developer to the developer carrying member and the deterioration of the developer characteristics are caused. It is possible to prevent an increase in drive torque. Since the density of the supply roller is 0.15 g / cm ³ or more, the low-molecular-weight oil does not exude from the supply roller, and the contamination of the developer carrier is less likely to occur.
Since it is 5 g / cm ³ or less, it is possible to prevent the fusion of the developer on the developer carrier, the deterioration of the developer characteristics, and the increase of the driving torque of the developer carrier due to the excessive contact pressure of the supply roller. it can. Furthermore, piece hardness is Asker C, 300
Since the g load is 8 ° or more, it is possible to prevent the low-molecular oil from oozing out from the supply roller, and it is difficult for the developer carrier to be contaminated. The contact pressure of the supply roller is 30 ° or less. It is possible to prevent the fusion of the developer on the developer carrying member, the deterioration of the developer characteristics, and the increase of the driving torque of the developer carrying member due to the excessively large amount. 10 cells
Since it is 0 pieces / inch ² or more, exudation of low-molecular-weight oil from the supply roller does not occur, and the contamination of the developer carrier can be suppressed. 400 pieces / inch ²
Because of the following, it is possible to prevent the fusion of the developer on the developer carrier, the deterioration of the developer characteristics, and the increase of the driving torque of the developer carrier due to the excessive contact pressure of the supply roller.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a developing device showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a state of toner in the vicinity of the magnetic blade of the developing sleeve in the first embodiment of the invention.

FIG. 3 is a diagram showing changes in image density and fog in the first embodiment of the present invention and a comparative example.

FIG. 4 is a schematic sectional view of a developing device showing a second embodiment of the present invention.

FIG. 5 is a diagram showing a conventional example.

[Description of Reference Signs] 1 photosensitive drum (image bearing member) 3 developing sleeve (developer bearing member) 5 magnetic blade (regulating member) 6 toner supply roller (supply roller) 7 magnetic toner (developer)

Claims (5)

[Claims] 1. A developer having a built-in magnetic field generating means having a plurality of magnetic poles, which conveys the supplied one-component magnetic developer to a developing region opposed to the image carrier by carrying and rotating the one-component magnetic developer. With respect to the carrier and the rotation direction of the developer carrier, a magnetic plate that is close to the surface of the developer carrier on the upstream side of the developing region and that controls the amount of the developer carried on the developer carrier -Like regulating member and the developer carrying member is abutted on the upstream side of the regulating member and rotated in the same direction, whereby the developer is peeled off and supplied to the developer carrying member. In a developing device including a supply roller made of foam, the regulating member is a developer of the regulating member in a first quadrant within a coordinate plane formed by a horizontal line passing through a rotation center of the developer carrier and a vertical line. Self close to the carrier A developing device, wherein a fixed end opposite to the free end is disposed in a state of being inclined to the upstream side in the rotation direction of the developer carrying member. 2. The angle θ ₁ formed by the straight line passing through the center of rotation of the developer carrier and the center of the free end of the regulating member with respect to the vertical line satisfies 20 ° ≦ θ ₁ ≦ 70 °. The developing device described. 3. The center of rotation of the supply roller is located below the center of rotation of the developer carrier, and the center of the free end of the proximity member of the regulating member to the developer carrier and the center of the contact portion of the supply roller. The angle θ ₂ formed with respect to the rotation center of the developer carrying member satisfies 60 ° ≦ θ ₂ ≦ 90 °.
Alternatively, the developing device according to claim 2. 4. The developing device according to claim 1, wherein the surface of the developer bearing member has a pseudo mirror surface that is not roughened by abrasive grains or the like. 5. The contact width of the supply roller with the developer carrying member is 0.5 to 6.0 mm, and the density of the supply roller is 0.1.
5 to 0.35 g / cm ³ , piece hardness is Asker C, 3
5. A load of 00 g is 8 to 30 [deg.] And the number of cells is 100 to 400 cells / inch < ² >.
The developing device according to any one of the above.