JPH09171298A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent leakage occurring between a toner carrier and a toner supplying member and between the toner carrier and a latent image carrier in the case of using metallic material without forming new different material on the surface of the toner carrier by setting the average diameter of an unoxidized coating film part at least in the width of an image area on the surface of the toner carrier equal to or under a specified value. SOLUTION: The toner carrier 6 is rotated in contact with toner supplying member 7 at specified speed in a direction shown by an arrow A. The member 7 is disposed near the exit of a toner hopper 3 so that it may be rotated in a direction shown by an arrow C at its contact part B with the toner carrier 6 so as to carry toner to the toner carrier 6. In the developing device 2 provided with the member 7 and the toner carrier 6, at least whose surface is made of metal; the average diameter of the unoxidized coating film part at least in the width of the image area on the surface of the toner carrier 6 is set to <=100μm. Thus, even when voltage is impressed, the leak does not occur, and a distinct image free from faulty carrying of toner is obtained with inexpensive constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic developing device used in copying machines, printers, facsimiles and the like, and more particularly to a toner carrier.

[0002]

2. Description of the Related Art Conventionally, an image forming apparatus for forming an image by using a toner forms an electrostatic latent image on a latent image carrier using a photoconductive material based on a so-called Carlson process, and then, Fine powder called "toner" is selectively adhered to the latent image, and development is performed to visualize the latent image.
This visualized toner is transferred to a transfer material such as paper, if necessary, and then fixed by heat and pressure, solvent vapor or the like to obtain an image-formed product.

In the developing device used in the image forming apparatus, as proposed in Japanese Unexamined Patent Publication No. 61-238072, a toner supply means made of conductive foam or the like is provided with a toner carrying means made of conductive rubber or the like. It is generally arranged so as to rotate in contact with the body and apply a predetermined voltage between the toner carrier and the toner supply member.
In this method, the toner is attached to the surface of the toner carrier by the contact rotation of the toner supply means and the toner carrier, and the toner is uniformly transported by the mechanical carrier force and the electrostatic force by frictional charging. Further, as proposed in the above publication, a voltage is applied between the toner carrier and the toner supply member. Specifically, when the potential difference obtained by subtracting the voltage of the toner carrier from the voltage of the toner supply unit is applied to the same polarity side as the toner polarity, the toner on the toner supply member is positively charged. The toner will be conveyed to the toner, which leads to an improvement in the toner conveyability. Further, when applied to the negative polarity side with respect to the toner polarity, the residual toner after development works in the direction of collecting it to the toner supply member, so that the residual image and fog can be reduced.

However, the conventional toner carrier formed of an elastic material such as rubber increases the charge imparting property to the toner due to the tackiness of the rubber itself and deterioration of the toner due to bleeding out from the material. There was a limit.

A metal material has been proposed as a toner carrier in consideration of these.

However, when the toner carrier is a low resistance conductor such as metal, since the toner supply member is made of conductive foam, a voltage is applied between the toner carrier and the toner supply member. When applied, leakage may occur due to contact between the two. Further, it is well known that the leak similarly occurs in the non-image area of the toner carrier in which the toner is not present.

Therefore, the voltage cannot be normally applied between the toner supply member and the toner carrier, and problems such as poor toner transportability, afterimage, and fog occur.

Further, this problem may similarly occur with the latent image carrier.

More specifically, when a defective portion of the photosensitive layer, which is the latent image carrier, or a pinhole portion is present and a foreign substance such as dust penetrates into the defective portion to form a conductive path, a current is passed through this conductive path. Will flow intensively. When the toner carrier comes into contact with the defective portion or the pinhole portion in this state, the voltage supplied to the toner carrier causes a current to flow in the conductive path formed by the foreign material or the like in the defective portion or the pinhole portion with low impedance. It will be. When the value of the current flowing into the pinhole portion exceeds the value limited by the circuit, the voltage supplied to the toner carrier drops, resulting in defective toner supply, which significantly deteriorates the image quality.

Not only that, but since an excessively large current flows intensively in an extremely small area, foreign matter in the toner carrier and pinholes in contact with this area generates heat, which causes a change in material of the toner carrier and latent image carrying. There is a problem in that the pinhole part of the body is enlarged, causing fatal damage.

As a countermeasure against this, Japanese Patent Laid-Open No. 177865/1993
It has been proposed that an insulating layer is provided by a resin layer on the upper surface of the conductor on the surface of the toner carrier, and the surface of the insulating layer is made uneven so as to improve toner transportability.

According to such a toner carrier of the developing device, since the surface layer is newly formed by another material such as resin, the insulating layer has a surface roughness that affects toner transportability. Therefore, it becomes difficult to make the film uniformly. Further, there has been a problem that the cost is increased by increasing the number of production processes.

[0013]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and its main object is to carry a toner carrier when a metal material having a good toner charging property is used for the toner carrier. By preventing a leak that occurs between the body and the toner supply member and between the toner carrier and the latent image carrier without forming a new dissimilar material on the surface,
An object of the present invention is to provide a developing device that can be configured at low cost and that can easily obtain a clear image without poor toner transportability, afterimage, and fog.

Further, a toner carrier and a toner supply member,
An object of the present invention is to provide a developing device in which the material of the latent image carrier is not changed and fatal damage is not caused.

[0015]

In order to achieve the above object, a developing device according to a first aspect of the present invention is a developing device including a toner supply member and a toner carrier having at least a surface made of metal. The average diameter of the unoxidized film portion of the body surface is 100 μm or less at least in the width of the image region.

A developing device according to a second aspect is the developing device according to the first aspect, wherein the toner supply member is an elastic body made of foamed foam and has a contact depth of 1.5 mm or less with the toner carrier. It is characterized by rotating.

According to a third aspect of the present invention, in the developing device according to the first aspect, the toner carrier is made of aluminum.

A developing device according to a fourth aspect is the developing device according to the third aspect, wherein the aluminum of the toner carrier contains magnesium.

According to a fifth aspect of the present invention, in the developing device according to the fourth aspect, the content of metal components other than magnesium in aluminum of the toner carrier is 1.
It is characterized by being 5% or less.

A developing device according to a sixth aspect is the developing device according to the fifth aspect, wherein the metal component other than magnesium in the aluminum of the toner carrier is copper, silicon,
Alternatively, it is made of iron.

The developing device according to claim 7 is the developing device according to claim 3, characterized in that an anodized film or a chemical conversion film is formed on the surface of the toner carrier.

The developing device according to claim 8 is the developing device according to claim 1, wherein the diameter of the image area width of the toner carrier is smaller than the diameter of the non-image area width.

[0023]

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

<Embodiment 1> FIG. 1 is a view showing the first embodiment of the developing device according to the present invention, and is a schematic view showing the construction of the main part of the developing device.

In the figure, reference numeral 1 is a latent image carrier, which is rotationally driven in the direction of arrow E in the figure by a driving means (not shown).

Around the latent image carrier 1, along the direction of rotation thereof, a charging means, an exposing means, a developing device of the present invention, and a transfer means, not shown, are arranged (not shown). The latent image carrier 1 and each of the above means are configured by known techniques. In the developing device of this embodiment, since metal is used for the surface of the toner carrier 6, the contact may become unstable when the latent image carrier 1 is formed of a rigid drum. In this case, as the latent image carrier 1, a belt structure having a photosensitive layer formed on a film such as a nickel electroformed tube or a resin whose surface is coated with a conductive layer can also be used.

According to such an image forming apparatus, the latent image carrier 1 rotates in the direction of arrow E, and the surface thereof is uniformly charged by the charging means. Thereafter, the surface of the latent image carrier 1 is scanned by a laser beam or the like emitted from the exposing means to form an electrostatic latent image, and the latent image is developed by the developing device 2 to form a toner image T. To be done.

Reference numeral 2 denotes a developing device of the present invention using a non-magnetic one-component toner (hereinafter referred to as toner), which is the latent image carrier 1
In order to make a visible image by supplying toner to the upper electrostatic latent image, it has the following configuration.

In FIG. 1, 3 is a toner hopper for storing the toner used in this embodiment. In the toner hopper 3, a toner supply unit 4 having a function of conveying toner from the toner hopper 3 to the developing section is arranged.

Reference numeral 5 is a toner regulating means for uniformly thinning the toner layer pressure and uniformly charging the toner. It is arranged downstream of the toner supply member 7 along the rotation direction of the toner carrier 6. The toner regulating unit 5 has a rounded tip portion made of a plate material such as stainless steel or copper, and the tip R portion is evenly contacted with the surface of the toner carrier 6. Thereby, the toner layer pressure can be regulated uniformly.

As another means for controlling the toner, a means such as a plate material such as stainless steel or copper on which an elastic chip such as R-shaped rubber is formed can be used. As the rubber chip, silicone rubber, urethane rubber, natural rubber, isoprene rubber, styrene butadiene rubber, butadiene rubber, chloroprene rubber, butyl rubber, ethylene propylene rubber, epichlorohydrin rubber, nitrile butadiene rubber, acrylic rubber and conductive agents such as carbon are used. A dispersion-molded product can be used. Also, a single piece of these rubber materials can be similarly used. Furthermore, it is well known that the upper layer of the above material can be coated with a resin for use. Polyethylene, polystyrene, nylon, polyurethane, polyester and the like can be used as the coating material.

Next, the toner supply member will be described.

As the material of the toner supply member 7, it is preferable to select an elastic body for stabilizing the contact with the toner carrier. In this embodiment, silicone rubber, urethane rubber, natural rubber, isoprene rubber, styrene butadiene rubber, butadiene rubber, chloroprene rubber, butyl rubber, ethylene propylene rubber, epichlorohydrin rubber, nitrile butadiene rubber, acrylic rubber and conductive agents such as carbon. Although a dispersion-molded product can be used, urethane rubber is used in this embodiment.

A hardness of 80 ° (measured with an Asker C hardness meter) or less is suitable for stabilizing the contact with the toner carrier. A resistance value of 10 ³ to 10 ⁷ Ωcm (volume resistance value) was used.

Next, the toner carrier will be described.

The toner carrier 6 is in the natural atmosphere,
It is made of stainless metal that forms an oxide film.

In stainless steel, an oxide film CrO ₄ or the like is formed on the surface when the amount of chromium exceeds 13%, for example. Since this oxide film has a very good atomic spacing between the base and the crystal, it has good adhesion and is uniform, and the film itself is an insulator.

In this embodiment, stainless steel is used for the toner carrier 6, but other metals that easily form an oxide film are nickel, titanium, zinc, thallium, N.
b, Pt, etc. can be used.

The toner carrier has a pipe structure by extrusion molding.

The surface roughness of the toner carrier 6 is Rz1.
It was set to 10 μm. As the processing method, a sound blasting method, a paper method, a shot method, a steel wool method, a brush method, a honing method, a laser method or the like can be adopted.

A resistance value of 10 ⁷ Ωcm (volume resistance value) or less was used.

The toner carrier 6 and the toner supply member 7 as described above are arranged as follows.

The toner carrier 6 is rotated in contact with the toner supply member 7 in the direction of arrow A at a predetermined speed. Further, the toner supply member 7 has a contact portion B with the toner carrier 6 as shown in FIG.
Is arranged near the outlet of the toner hopper 3 so as to rotate in a counter (direction C in the figure), and is conveyed to the toner carrier 6. As a result, the toner can be conveyed at the portion D in the figure of the toner supply member 7.

Further, the toner carrier 6 and the toner supply member 7
The ratio of peripheral velocities is 1: 0.5 to 0.9, preferably 1 :.
It was set to 0.8. This is because if the peripheral speed of the toner supply member 7 is reduced below this, the transportability deteriorates, and conversely, if the peripheral speed is further increased, the transportability does not improve so much and the torque of the apparatus increases.

FIG. 2 is an enlarged view of the cross section of the toner carrier 6 used in this embodiment. The figure is a view of a cross section of the toner carrier 6 observed by an X-ray microanalyzer. In the figure, reference numeral 21 is stainless steel of this embodiment which is a metal base. 22 is an oxide film. The oxide film 22 is formed on the surface of the stainless steel 21 according to the above-mentioned principle. Reference numeral 23 is a dissimilar metal such as copper contained in stainless steel. The dissimilar metals 22 are various, such as those that are originally contained in the base metal and those that are contained for reasons such as strength UP of the material and workability. In many cases, these dissimilar metals 23 contain a large amount of materials such as copper, which are difficult to form an oxide film by themselves. If the dissimilar metal 23 exists on the surface of the toner carrier 6, that portion does not form an oxide film. Therefore, the surface of the dissimilar metal 23 remains low in resistance. Therefore, the toner is easily leaked from the toner supply member 7 made of a conductor.

Furthermore, the probability of leakage increases as the particle size of the dissimilar metal increases.

The particle size of the dissimilar metal 23 appearing on the cross section of the toner carrier is larger than the size of the primary particles of the dissimilar metal itself. This largely depends on the diameter of the crystal grain boundary formed by the influence of stress, heat, etc. that occur during processing.

Table 1 shows the relationship between the leak that occurs between the toner carrier 6 and the toner supply member 7 when the grain boundary diameter of different metals is changed.

The size of the grain boundaries of the dissimilar metals was controlled as follows.

The toner carrier 6 of this embodiment was processed into a pipe by general extrusion molding. In this process, the grain boundary diameter of the dissimilar metal was changed by changing the conditions with the reduction rate during extrusion as a parameter.

Specifically, in the process of melting → casting → billet cutting → preheating → extrusion → cooling → stretch straightening → cutting, the reduction rate during extrusion was varied at 5-40%.

[0052]

[Table 1]

In the above table, the leak resistance was determined by measuring the leak current when the toner carrier and the toner supply member were placed in a high temperature and high humidity environment and 200 V was applied between the toner supply member and the toner carrier.

⊚ indicates that the leak current is 0, ◯ indicates that the leak current of 1 μA or less intermittently flows (a level where there is no problem in using the device), Δ indicates that the leak current of 1 μA or more intermittently flows, and × indicates the leak current. It was when the leakage current of 1 μA or more continuously flowed.

From the table, it can be seen that if the grain boundaries of dissimilar metal grains are larger than 100 μm, a leak easily occurs between the toner carrier 6 and the toner supply member 7.

In the above description, the toner carrier having an average grain size of different metal crystal grain boundaries of 50 μm is the toner carrier of the present embodiment extruded at a reduction rate of 40%, which is shown in FIG.

Further, the average diameter of grain boundaries of different metals is 500 μm.
In the case of m, the reduction rate at the time of extrusion was 5%. FIG. 3 is an enlarged view of a cross section of stainless steel when extruded at a reduction rate of 5%, when observed with an X-ray microanalyzer. The magnification in FIG. 3 is shown at the same magnification as the magnification when the reduction rate of 40% in FIG.

In FIG. 3, reference numeral 31 is stainless steel as a base material, and 32 is an oxide film. The oxide film 32 is formed on the upper layer of the stainless steel 31. 33 is a dissimilar metal. As shown in the figure, it can be seen that each grain boundary is considerably larger than when the reduction rate is 40%. The crystal grain boundary of the dissimilar metal 33 has expanded to about 500 μm. Further, no oxide film is formed on the upper layer of the dissimilar metal 33.

As described above, when the diameter of the dissimilar metal portion where the oxide film is hard to form is large, the toner supplying member, which is a conductor, is likely to come into contact with the dissimilar metal, which is a conductor, so that leakage easily occurs. .

From the above, it is understood that the average diameter of the unoxidized film portion on the surface of the toner carrier 6 is preferably 100 μm or less. Therefore, in this embodiment, the average diameter of the unoxidized film portion on the surface of the toner carrier 6 is set to 100 μm or less.

<Embodiment 2> FIG. 4 is a view showing the essential parts of a second embodiment of the developing device according to the present invention. In this figure, the same parts as those in the first embodiment described above are designated by the same reference numerals.

The second embodiment differs from the above-mentioned first embodiment in the structure of the toner supply member 7 and the arrangement of the toner carrier 6, and the other points are the same.

In the first embodiment, in order to improve the transportability in order to further improve the feeding performance, and further to improve the scraping effect of the residual toner after development in order to reduce the residual image, the toner made of foamed foam is used. The supply means is better.

Therefore, the toner supplying means 7 is made of conductive foam.

In FIG. 4, the toner supply means 7 is arranged near the outlet of the toner hopper 3 so as to rotate in a counter (direction C in the figure) at the contact portion B with the toner carrier 6, and transfers the toner to the toner. It is to be conveyed to the carrier 6.

As the material of the toner supply roller 7, polyurethane foam, polystyrene foam, polyethylene foam, polyester foam, ethylene propylene foam, nylon foam, silicone foam, etc. can be used. In this embodiment, polyurethane foam was used.

The foaming cell of the toner supplying means 7 is a single foam,
Both open cells can be used, but closed cells are preferred.
When the foam cells are open cells, the toner enters inside the foam cells of the toner supply means 7, and eventually the toner agglomerates in the inside and the surface layer portion, the toner transportability is deteriorated, and further the torque UP of the entire apparatus is brought about. Therefore, closed cells are preferable.

A hardness of 10 ° to 40 ° (measured by an Asker C hardness meter) can be used, but optimally, a hardness of 35 ° to 40 °, which has a great effect of scraping residual toner, is more preferable. A resistance value of 10 ³ to 10 ⁷ Ωcm (volume resistance value) was used. The toner carrier 6 used was the same as that used in the first embodiment.

The peripheral speed ratio between the toner supply means 7 and the toner carrier 6 was also the same as in the first embodiment.

Table 2 shows the contact depth at which leakage occurs when the contact depth between the toner carrier 6 and the toner supply member 7 is changed in the above structure.

[0071]

[Table 2]

From the table, the toner carrier 6 and the toner supply member 7
If the contact depth with the deeper than 1.5 mm, the toner carrier 6
Leakage easily occurs between the toner supply member 7 and
It can be seen that it is better if it is less than or equal to mm.

This is because the walls constituting the cells of the foamed foam of the toner supply member, which is a conductor, are easily hard to enter into the dissimilar metal portion where the oxide film is hard to form because of the low hardness. Therefore, it is easy to leak.

From the viewpoint of reducing the torque of the developing device, it is preferable that the contact depth is shallow, preferably 1.0 m.
m or less was good.

From the above, even when the average diameter of the unoxidized film portion on the surface of the toner carrier 6 is 100 μm or less and the toner supply member 7 is a conductive elastic body made of foamed foam, the contact depth is 1.5 mm or less. By doing so, leakage can be further reduced, and if the device configuration is taken into consideration, 0.5 m
m or less is preferable.

<Third Embodiment> The third embodiment described above is the first embodiment.
The third embodiment is different from the first embodiment in that the metal of the first toner carrier 6 is made of aluminum, and the other points are the same.

In the first embodiment, in order to further reduce the size of the apparatus and reduce the cost after taking the developing performance and the measures against the leak, the weight of the toner carrier is reduced and the torque is reduced. It is important to go. For that purpose, aluminum, which has a very small specific gravity of the material forming the toner carrier, is excellent.

Further, aluminum has a better oxidizing property than the metals mentioned in the first embodiment, and an oxide film is easily formed.

Therefore, the toner carrier 6 is made of aluminum in this embodiment.

Table 3 shows the thicknesses of the oxide films of the stainless steel used in the first embodiment and the aluminum of this embodiment.

As the measuring method, for example, the eddy current method, S
IMS (Secondary Ion Mass Spectroscopy), FE-
SEM, XMA (X-ray microanalyzer) or the like can be used.

[0082]

[Table 3]

From the table, it can be seen that aluminum has a thicker oxide film.

As a result, the leak property with the toner supply member 7 can be further reduced.

Table 4 shows the relationship with the leak that occurs between the toner carrier 6 and the toner supply member 7 when aluminum is used for the toner carrier 6.

[0086]

[Table 4]

From the results in the above table, it can be seen that even if the toner carrier 6 is made of aluminum, no leak occurs between the toner carrier 6 and the toner supply member 7.

From the above, the metal on the surface of the toner carrier 6 is aluminum.

<Fourth Embodiment> The fourth embodiment is the same as the third embodiment described above.
The third embodiment is different from the first embodiment in that the metal of the third toner carrier 6 is made of aluminum and further contains magnesium as an oxide film promoting material, and the other points are the same.

Magnesium is easier to burn and harder to process than aluminum, and therefore is not suitable as a base material for the toner carrier 6 which requires severe surface roughness.

However, since magnesium is more easily oxidized than aluminum, it is a suitable material to be contained as an oxidation accelerator. Therefore, an aluminum alloy containing magnesium is easier to grow an oxide film than pure aluminum,
The Mg / Al ratio of the coating is higher than that of metal. Further, the film thickness is greatly affected by the temperature, but as the temperature rises, this ratio increases, and finally magnesium oxide becomes the main component of the film. Since the oxide film formed of magnesium oxide is more stable and uniform than the oxide film formed of aluminum oxide, the leakage resistance stability is further improved.

Table 5 shows the relationship between the magnesium content of aluminum and the leakage resistance stability occurring between the toner carrier 6 and the toner supply member 7.

[0093]

[Table 5]

From the table, it is understood that as the content of magnesium in aluminum is increased, the leak generated between the toner carrier 6 and the toner supply member 7 is further reduced and becomes stable.

This is because magnesium forms an oxide film more easily than aluminum as described above.

Aluminum alloys that can be used in this embodiment include aluminum-copper-magnesium alloys (JI
S designation 2000 series), aluminum-manganese alloy (3000 series), aluminum-silicon alloy (4 series)
000 series), aluminum-magnesium alloy (5
000 series), aluminum-magnesium-silicon series alloy (6000 series), and aluminum-zinc-magnesium alloy (7000 series). In this example, JIS-named 5052 of aluminum-magnesium alloy is used. did.

From the above, the metal of the toner carrier 6 is an aluminum alloy containing magnesium.

<Fifth Embodiment> The fifth embodiment described above is the fourth embodiment.
The fourth embodiment is different from the first embodiment in that the metal of the fourth toner carrier 6 is made of an aluminum alloy containing magnesium and the content ratio of other different metal components is set to 1.5% or less. The point is the same.

Since different metals other than magnesium are less likely to form an oxide film than aluminum, the higher the content of the different metal, the lower the coverage of the oxide film on the surface of the toner carrier 6. Therefore, a leak easily occurs between the toner carrier 6 and the toner supply member 7 that is in contact with the toner carrier 6.

In this example, zinc was used as the dissimilar metal.

Table 6 shows the relationship with the leak occurring between the toner carrier 6 and the toner supply member 7 when the content of zinc is changed.

[0102]

[Table 6]

From the table, it can be seen that when the content of zinc in aluminum is increased to exceed 1.5%, a leak occurs between the toner carrier 6 and the toner supply member 7.

This is because zinc is less likely to form an oxide film than aluminum as described above, and the coverage of the oxide film existing on the surface of the toner carrier 6 decreases as the content of zinc increases. Is.

The main points of the aluminum alloy that can be used in this embodiment are aluminum-manganese alloys (JIS
Examples thereof include an aluminum-magnesium alloy (5000 series), an aluminum-magnesium-silicon alloy (6000 series), and the like. In this example, JIS-named 6063 of aluminum-magnesium-silicon alloy was used.

In this example, the aluminum alloy having a zinc content of 6% given as a comparative example was JIS-7003 of aluminum-zinc-magnesium alloy.

From the above, the metal of the toner carrier 6 is an aluminum alloy containing magnesium, and the different metals are 1.
It was set to 5% or less.

<Sixth Embodiment> The sixth embodiment described above is the fifth embodiment.
5 is different from the example in that the metal of the fifth toner carrier 6 contains magnesium, and the content ratio of the different metal components is 1.5%.
It is composed of the following aluminum alloy, and the different metal is copper, silicon, or iron, and there is no change in other points.

Generally, aluminum is apt to cause corrosion called pitting corrosion. What is pitting corrosion? A few ppm of chlorine ions in the air are adsorbed on the defective part due to scratches on the surface oxide film,
This is a phenomenon in which the oxide film is locally dissolved to form pits. Electrochemically, there is a potential called the pitting potential, and when the spontaneous potential of aluminum is higher than this, pitting occurs and is promoted.

Further, when the dissimilar metals are copper, silicon and iron,
Since the pitting potential of the dissimilar metal is higher than the pitting potential of aluminum, the pitting corrosion of aluminum in contact with these grain boundaries is promoted.

Table 7 shows the degree of corrosion at the contact portion using the dissimilar metal in contact with aluminum as a parameter.

[0112]

[Table 7]

From the above table, it can be seen that copper is most likely to corrode at the aluminum contact portion.

Therefore, an aluminum alloy containing a dissimilar metal that promotes the above-described corrosion, that is, pitting corrosion, easily breaks the oxide film, so that leakage easily occurs.

In the present embodiment, copper is used, which easily corrodes dissimilar metals.

Table 8 shows the relationship between the copper content and the leak occurring between the toner carrier 6 and the toner supply member 7.

[0117]

[Table 8]

From the table, it is understood that when the content of copper in aluminum is increased to more than 1.5%, a leak occurs between the toner carrier 6 and the toner supply member 7.

As described above, this is because, as the copper content is increased, the oxide film existing on the surface of the toner carrier 6 is easily destroyed in order to promote the corrosion called pitting corrosion that occurs on the aluminum surface. This is because the coverage of the oxide film is reduced.

This phenomenon becomes more remarkable as the durability increases.

The aluminum alloy that can be used in this embodiment is an aluminum-manganese alloy (3000
Type), aluminum-magnesium type alloy (the same 5000
System), aluminum-magnesium-silicon alloy (6000 system), and the like.

In this example, JIS-named 3005 of aluminum-manganese alloy (copper 3000 series) was used.

In this example, copper 5.
The alloys containing 0% and 2.2% are aluminum-copper-magnesium alloy JIS Nos. 2014 and 211.
7 was used.

From the above, the content of copper, iron, and silicon in the aluminum alloy containing magnesium as the metal of the toner carrier 6 is set to 1.5% or less.

<Embodiment 7> The seventh embodiment is the same as the third embodiment described above.
The third embodiment is different from the second embodiment in that the metal of the third toner carrier 6 is made of aluminum and an anodic oxide film or a chemical conversion film is formed on the surface thereof, and the other points are the same.

In the third embodiment, it is important to roughen the surface of the toner carrier so as not to have tackiness in order to further improve the toner transportability while taking measures against leaks. become. For that purpose, it is necessary to uniformly form unevenness finer than the toner particle size. The anodic oxide film and the chemical conversion film have fine irregularities during film formation. In particular, the anodized film is porous, and the recess diameter is about 100 to 200 angstroms, which is smaller than the toner particle diameter, and is suitable for forming fine irregularities on the surface of the toner carrier made of aluminum. Further, in order to improve the rolling of the toner for the purpose of improving the chargeability of the toner, it is possible to slightly fill the concave portion of the anodized film to make it smooth. Specifically, a sealing process is performed.

Further, since the anodic oxide film and the chemical conversion film are also oxide films and are formed in the upper layer portion of the passivation film formed on the aluminum surface, the oxide film becomes thicker and more uniform, and leakage resistance stability is also improved. improves.

Therefore, the toner carrier 6 is made of aluminum having an anodized film formed on its surface in this embodiment.

The chemical film that can be used in this embodiment is as follows.
Examples thereof include alkali-chromate type, chromate type, phosphoric acid-chromate type, zinc phosphate type, non-chromate type, coating type chromate type and oxide film type.

Further, as an anodized film that can be adopted,
Acid baths such as sulfuric acid, oxalic acid, chromic acid and boric acid, alkaline baths, non-aqueous baths, hard films, colored films and the like can be mentioned.

Furthermore, examples of the method for sealing the anodized film include a steam method, a pure boiling water method, a nickel acetate method, a dichromic acid method, and a sodium silicate method.

From the above, the metal surface of the toner carrier 6 is aluminum with an anodized film or a chemical conversion film.

<Embodiment 8> The above-described first embodiment of the eighth embodiment
The present embodiment is different from the first embodiment in that it is made of the metal of the first toner carrier 6 and is related to the diameter of the toner carrier, and the other points are the same.

In the first embodiment, if the diameter of the width of the image area of the toner carrier 6 is larger than the diameter of the width of the non-image area, the pressure at the portion in contact with the toner supply member 7 becomes high and more leak occurs. It will be easier. Further, the image area width is generally subjected to blasting or the like in order to improve the toner transportability. In the blasting process, the blast ball is depressed where the ball hits, but the area around the hit bulges. As a result, the diameter of the image area width becomes large. This bulging portion locally contacts the toner supply member 7 with a high pressure, and leaks easily occur.

Therefore, it is better that the diameter of the image area width of the toner carrier 6 is smaller than the diameter of the non-image area width.

Table 9 shows the relationship with the leak that occurs between the toner carrier 6 and the toner supply member 7 when the diameter of the image area width of the toner carrier 6 is changed.

[0137]

[Table 9]

From the table, it is understood that when the diameter of the width of the image area of the toner carrier 6 is smaller than the diameter of the width of the non-image area, the leak is less likely to occur between the toner carrier 6 and the toner supply member 7.

Further, this embodiment can cope with a leak due to contact with the latent image carrier.

More specifically, since the diameter of the image area width of the toner carrier 6 can be made smaller than the diameter of the non-image area width, the distance between the toner carrier 6 and the latent image carrier 1 is different from that of the toner carrier 6. Since the diameter in the image area width and the diameter of the latent image carrier are determined, the image area of the toner carrier 6 does not come into contact with the latent image carrier. Therefore, even if there is a pinhole or the like on the latent image bearing member, the toner bearing member 6 does not come into contact with the latent image bearing member, so that the leak does not occur and the toner bearing member 6 and the latent image bearing member 1 are not fatally damaged. Absent.

Furthermore, if an insulating film such as an oxide film is formed in the width of the non-image area of the toner carrier 6 which is in contact with the latent image carrier 1, no leak will occur in the non-image area.

As a method for reducing the diameter of the image area width which can be adopted in this embodiment, a sound blast treatment, a shot method, a steel wool method, a brush method, a honing method, a paper method is used after mechanical cutting, polishing or the above-mentioned processing. There is a method of performing processing such as.

If the image area width is processed by etching, chemical polishing, electric field polishing, etc., the surface is roughened while eroding the entire area. Therefore, the diameter of the image area width to be processed is smaller than that of the non-image area width. Can be made smaller.

Examples of the etching method include alkali etching and acid etching.

If a step or an edge is present on the toner carrier 6 during the processing, the toner supply member 7 and the latent image carrier 1 may be damaged and cause a new leak. Therefore, if the corners and steps of the toner carrier 6 are chamfered or processed into an R shape, the leak countermeasure becomes better.

As described above, the toner carrying member 6 is formed so that the diameter of the image area width is smaller than the diameter of the non-image area width.

Although the present invention has been described above focusing on the relationship with the toner supply member, the present invention is not limited to the above-mentioned embodiments, and is within the scope of the present invention. Can be appropriately modified.

For example, in the first, second, third, fourth, fifth, sixth and seventh embodiments, in the developing device in which the latent image bearing member and the toner bearing member are brought into contact with each other, a countermeasure against leakage of the latent image bearing member is taken. Can also be adopted as

[0149]

As described above, according to the present invention, when a metal material is used for the toner carrier, the toner carrier and the toner supply member are separated from each other and the toner carrier and the latent image carrier are separated from each other. Even if a voltage is applied between them, a leak does not occur, and a clear image with no toner conveyance failure can be obtained with a low cost structure.

Further, a toner carrier and a toner supply member,
It is possible to obtain a developing device in which there is no change in the material of the latent image carrier or fatal damage.

It is particularly effective to apply the apparatus of the present invention to an image forming apparatus such as a printer, a video printer, a facsimile and a copying machine.

[Brief description of the drawings]

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

FIG. 2 is an enlarged sectional view of the toner carrier used in the first embodiment of the present invention.

FIG. 3 is an enlarged cross-sectional view of a comparative toner carrier used in the first embodiment of the present invention.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Latent image carrier 2 Developing device 3 Toner hopper 4 Toner supply means 5 Toner regulating means 6 Toner carrier 7 Toner supply member

Claims (8)

[Claims] 1. A developing device comprising a toner supply member and a toner carrier having at least a surface made of metal, wherein an average diameter of an unoxidized film portion at least in an image region width on the surface of the toner carrier is 100 μm or less. A developing device characterized by the above. 2. The toner supply member is an elastic body made of foam and has a contact depth of 1.5 with the toner carrier.
2. The developing device according to claim 1, wherein the developing device is contact rotated at a distance of not more than mm. 3. The developing device according to claim 1, wherein the toner carrier is made of aluminum. 4. The developing device according to claim 3, wherein aluminum of the toner carrier contains magnesium. 5. The developing device according to claim 4, wherein the content of metal components other than magnesium in aluminum of the toner carrier is 1.5% or less. 6. The developing device according to claim 5, wherein the metal component other than magnesium in aluminum of the toner carrier is copper, silicon, or iron. 7. The anodic oxide coating or the chemical conversion coating is formed on the surface of the toner carrier.
The developing device described. 8. The developing device according to claim 1, wherein the diameter of the image area width of the toner carrier is smaller than the diameter of the non-image area width.