JPH1115262A - Developing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a developing device constituted so that a high-quality image can be formed by stabilizing toner carrying quantity by controlling the friction coefficient of the developer holding surface of a developing roller. SOLUTION: This developing device is provided with the developing roller 23K (63C, 63M and 63Y) holding and carrying the one-component developer. Then, the developer holding surface of the roller 23K is formed so that the friction coefficient (μs) thereof becomes 0.1<=μs<=0.4. Thus, the toner carrying quantity (m/a) of the developer holding surface of the roller 23K is set in a proper area that desired image density is obtained and the surface staining of the image is not caused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a developing device such as a copying machine, a facsimile, and a printer, and more particularly to a developing device having a developing roller for carrying and transporting a one-component developer.

[0002]

2. Description of the Related Art Conventionally, as a developing device of this type, a developing roller is formed by forming an elastic layer on a core metal as a rotating shaft,
A thin layer for carrying a one-component developer such as non-magnetic or magnetic toner supplied to the developing roller on the surface of the developing roller and regulating the layer thickness of the developer disposed on the transport path. By thinning the developer with a blade,
It is known that an electrostatic latent image formed on the photoconductor is visualized with toner by being conveyed to a photoconductor serving as an image carrier disposed opposite to the developing roller.

Incidentally, a developing roller comprising a single elastic layer as described above, for example, silicone rubber, NBR, E
A developing roller having an elastic layer formed of an elastic rubber such as PDM or an elastomer such as polyurethane has a thin layer blade for thinning the developer or a large frictional resistance with a photoreceptor. There is a drawback that blur occurs and density undulation called jitter occurs in the carried developer layer. Further, with this developing roller, the amount of developer transported at the initial stage is increased, and an abnormal image may be generated.

In order to solve such a problem, conventionally, in a developing roller having a conductive layer formed on the outer periphery of a good conductive shaft, the surface of the conductive layer has an average particle diameter of 30%.
In a developing roller having a surface treated with a fine powder having a particle diameter of not more than μm (Japanese Patent Application Laid-Open No. 8-179419) and a developing roller having a conductive layer formed on the outer periphery of a good conductive shaft, the surface of the conductive layer is a roller. DIN 4776 standard core depth roughness (Rk) in the circumferential direction is 0.5 to 3.5 μm, and the Rk ratio between the circumferential direction of the roller and the axial direction is the circumferential direction / axial direction>
A developing roller of 1.0 (JP-A-8-179620) has been proposed.

[0005]

However, in the developing roller described in Japanese Patent Application Laid-Open No. Hei 8-179419, the surface of the elastic roller is surface-treated with fine powder. However, the friction of the roller surface depends on the thickness of the surface treatment. Since the coefficient changes, there is a possibility that a thin layer defect in which the thickness of the developer thin layer becomes uneven depending on the thickness of the surface treatment may occur.

Further, in the developing roller described in JP-A-8-179620, DIN 4776 in the roller circumferential direction is used.
Although the standard core depth roughness (Rk) is specified to stabilize the toner transport amount, a roller using a material having a large coefficient of friction increases the developer transport force, so that the developer transport force is increased. There is a problem that thinning is difficult.

As described above, in the developing roller of the conventional developing device, a molding method for reducing the frictional resistance, or
Although the definition of the core depth roughness (Rk) for stabilizing the toner conveying force and the charging property has been performed, it has not been captured by the characteristic value of the friction coefficient.

The present invention has been made in view of the above problems, and an object of the present invention is to control the coefficient of friction of the developer carrying surface of the developing roller to stabilize the amount of toner transported, thereby improving the toner conveyance amount. An object of the present invention is to provide a developing device capable of obtaining a high-quality image.

[0009]

According to a first aspect of the present invention, there is provided a developing device having a developing roller for carrying and transporting a one-component developer. The surface has a coefficient of friction μs of 0.1 ≦ μs ≦
It is characterized by being formed in a surface state of 0.4. In this developing device, the developer carrying surface of the developing roller has a friction coefficient μs of 0.1 ≦ μs ≦
Since the surface state is formed to be 0.4, the toner conveyance amount of the developing roller is stabilized for the reason described later.

According to a second aspect of the present invention, in the developing device of the first aspect, the developing roller is formed of a conductive resin. In this developing device, since the developing roller is formed by a single-layer roller made of a conductive resin, the molding of the developing roller can be simplified, and the device can be inexpensive.

According to a third aspect of the present invention, in the developing device of the first aspect, the surface of the developing roller is made of a conductive resin layer. In this developing device, the surface of the developing roller is made of a conductive resin layer, and the toner conveying force and the charging property of the developing roller are not affected by the friction coefficient of the core metal or the like as a base material. The degree of freedom in selecting the material of the material is increased.

According to a fourth aspect of the present invention, in the developing device of the first aspect, the thin layer blade for thinning the developer carried on the developing roller is arranged along a tangential direction of the developing roller. The developing roller is in pressure contact with the developing roller in a trailing relationship. In this developing device, a thin layer blade for thinning the developer carried on the developing roller is pressed against the developing roller in a trailing relationship along the tangential direction of the developing roller. By doing so, the thin toner layer formed on the developing roller can be managed by the friction coefficient of the developing roller surface and the pressure contact force of the thin layer blade, so that the thin layer blade is arranged along the normal direction of the developing roller. As in the case of the counter method described above, it is not necessary to obtain a fine positional accuracy of the thin layer blade, and a wide setting range of the bite amount of the thin layer blade with respect to the developing roller can be obtained.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a developing device of a color image forming apparatus will be described below. First, a schematic configuration and operation of the entire color image forming apparatus including the developing device according to the present embodiment will be described. FIG.
1 is a schematic configuration diagram of a color image forming apparatus provided with a developing device according to the present embodiment. In FIG. 1, a flexible belt-shaped photoreceptor (hereinafter, referred to as a “photoreceptor belt”) 1 is provided between support rollers 2 and 3, and driven by the rotation of the support rollers 2 and 3 in a direction indicated by an arrow A in FIG. (Clockwise).
Around the photoreceptor belt 1 as an image carrier, a charging charger 4 as a charging unit for uniformly charging the surface of the photoreceptor belt, a laser writing unit 5 as an exposure device for forming an electrostatic latent image, Developing devices 6Y and 6 containing color developers of magenta, magenta and cyan, respectively.
A rotary color developing unit (hereinafter referred to as a "color developing unit") 6 as a rotary developing device integrally provided with M and 6Y, and a black developer separate from the color developing unit 6 is accommodated. A black developing device 7 and the like as a developing device are provided. As the photoreceptor belt 1, for example, a substrate obtained by applying an organic photosensitive layer (OPC) on a substrate made of Ni electroforming can be used.

The laser writing unit 5 includes a semiconductor laser (not shown), a polygon mirror 5B rotated by a drive motor 5A, an f-θ lens 5C, and a mirror 5D.
Are housed in a unit case 5E as a holding housing, and are incorporated in a lower part of the apparatus main body. A bottom plate (not shown) is provided between the paper feed cassette 17 and the laser writing unit 5. A laser writing unit 5 is incorporated on the bottom plate, and side plates (not shown) of the apparatus main body provided on the left and right (rear side and front side in FIG. 1) in the roller axis direction to support each unit correspond to the bottom plate. Has been assembled.

The charging position of the charging charger 4, the irradiation position of the light beam L from the laser writing unit 5, and the cleaning position of the photosensitive member cleaning blade 15A are located on the lower side of the two support rollers 2, 3. Of the photosensitive belt 1 around the support roller 2.

The color developing unit 6 and the black developing device 7 are provided with a developing roller 23 as a developer carrying member which comes close to or in contact with the photosensitive belt 1 at a predetermined position.
K, 63M, 63Y, and 63C (see FIG. 2), and has a function of visualizing the electrostatic latent image on the photosensitive belt 1 by non-contact development or contact development. The color developing unit 6 has a rotation axis perpendicular to the plane of FIG. 1 so that any one of the developing units 6Y, 6M, and 6Y synchronizes with the development timing of the corresponding color and moves to a developable position. The rotation about the center is controlled. By the rotation of the color developing unit 6 by 120 degrees, the developing device facing the developing position is switched. When the color developing unit 6 operates, the rotation of the cam 45 is controlled such that the black developing device 7 moves to a position separated from the photosensitive belt 1.

The upper support roller 3 of the photoreceptor belt 1
An intermediate transfer belt 10 as an image carrier is provided so as to come into contact with the wrapped portion. The intermediate transfer belt 10 is installed between the support rollers 11 and 12 so as to be inclined, and is rotated and conveyed in the direction of arrow B (counterclockwise) in the figure by driving the support rollers 11 and 12. Of the two stretched portions between the support rollers of the inclined intermediate transfer belt 10, the stretched portion on the photosensitive belt 1 side (lower left side in the figure) is supported by the upper support roller 3 of the photosensitive belt 1. Supported part (part wrapped around support roller 3)
Is in contact with Then, the first toner image on the photoreceptor belt 1 is transferred to the intermediate transfer belt 13 by a conductive bias brush 13 serving as a primary transfer member, which is a component of a charge applying unit, provided inside the intermediate transfer belt 10. Transfer belt 1
0 (primary transfer). This bias brush 1
3, a predetermined bias voltage is applied from a primary transfer power source (not shown), which is another component of the charge applying unit, and the leading end thereof contacts the back surface of the intermediate transfer belt 10 under predetermined conditions. A transfer roller 14 as a transfer opposing member (secondary transfer charge applying means) is provided so as to come into contact with and separate from the intermediate transfer belt 10 at a portion where the intermediate transfer belt 10 is wound around the support roller 11. ing. A predetermined bias voltage is applied to the transfer roller 14 from a secondary transfer power source (not shown) as a transfer electric field forming unit.
The transfer electric field formed at the contact facing portion between the transfer roller 14 and the intermediate transfer belt 10 causes the intermediate transfer belt 1
The image superimposed on the sheet 0 is transferred onto a transfer sheet as a sheet-like transfer material (secondary transfer). Here, the distance on the intermediate transfer belt 10 from the primary transfer position to the secondary transfer position is set to be equal to or longer than the maximum image output length.

Cleaning device 15 for photoreceptor belt
Is a cleaning blade 15A that constantly contacts the photoconductor belt 1 and cleans the toner on the photoconductor belt 1;
A waste toner collecting container 15B and the like are provided. The cleaning device 16 for the intermediate transfer belt includes a cleaning blade 16A for cleaning the surface of the intermediate transfer belt 10, an auger 16B for conveying the toner, and the like.
The cleaning blade 16A for the intermediate transfer belt is kept at a position separated from the surface of the intermediate transfer belt 10 when a toner image is transferred from the photoreceptor belt 1 during image formation by a blade contact / separation arm (not shown). Only at the time of cleaning after the secondary transfer, as shown in the drawing, it is brought into contact with the surface of the intermediate transfer belt 10 to scrape off the residual toner after transferring the toner image onto the transfer paper.

In the above-structured color image forming apparatus,
After the photoconductor belt 1 is uniformly charged by the charging charger 4, the laser beam (laser beam) L modulated based on image information is scanned by the laser writing unit 5 to be exposed, and the surface is electrostatically charged. A latent image is formed. Here, the image information used for the exposure is monochromatic image information obtained by decomposing a desired full-color image into yellow, magenta, cyan, and black color information. Laser light L generated by a semiconductor laser (not shown) based on this image information
Is rotationally scanned by a polygon mirror 5B rotated at high speed by a drive motor 5A, passes through an f-θ lens 5C,
The optical path is adjusted by the reflection mirror 5D.

The electrostatic latent image formed on the photoreceptor belt 1 is developed by a color developing unit 6 with a predetermined yellow toner, a magenta toner and a cyan toner, respectively. The electrostatic latent image formed based on the black color information is developed by the black developing device 7 with black toner. In this manner, the cleaning, latent image formation, and development of the photoreceptor belt 1 are repeated, and respective color images (toner images) are sequentially formed on the photoreceptor belt 1.

The single-color images (toner images) sequentially formed on the photosensitive belt 1 rotating in the direction of arrow A are yellow,
By a predetermined transfer bias applied to the bias brush 13 for each of the single colors of magenta, cyan, and black, transfer is sequentially performed at the same position on the intermediate transfer belt 10 that rotates in the direction of arrow B in synchronization with the photosensitive belt 1. Is done.

The yellow, magenta, cyan, and black color toner images superimposed on the intermediate transfer belt 10 are fed from a paper feed table (paper feed cassette)
The sheet is conveyed to the secondary transfer section via the pair of conveying rollers 19 and the pair of registration rollers 20 at a timing such that the position of the image on the transfer sheet becomes a regular position. On the transfer paper 17A conveyed to the secondary transfer section, the intermediate transfer belt 10
The images superposed on each other are collectively transferred by the transfer roller 14. After the transfer, the image is fixed by the fixing device 50 to complete a full-color image. The transfer paper 17A on which the full-color image has been formed is discharged to a discharge stack 52 via a discharge roller pair 51.

The waste toner scraped from the intermediate transfer belt 10 by the cleaning blade 16A is
An auger 16 </ b> B provided in the cleaning device 16 causes a conveyance unit (not shown) to use a waste toner collection container 1.
5B. When a predetermined amount or more of the waste toner is stored in the waste toner collecting container 15B, the container is appropriately replaced.

Next, the black developing device 7 used in the present color image forming apparatus will be described. FIG. 2 shows a black developing device 7.
1 is a schematic configuration diagram showing the inside of the device together with a color developing unit 6. The black developing device 7 contains a black developer (toner) in a developing container 71, and has a developing roller 23 </ b> K as a developer carrier in an opening 71 a of the developing container 71 facing the photoreceptor belt 1. This is a developing device integrally formed as a so-called developing cartridge in which the life of the developing device is replaced when the toner runs out.

In the developing container 71, a developing roller 23 is provided.
Parallel to K, and contacts the developing roller 23K at a predetermined contact pressure, and rotates so as to slide in a direction opposite to the developing roller surface moving direction at a contact portion with the developing roller 23K while forming a nip. For example, a toner supply roller 25K made of foamed polyurethane or the like is provided. In the vicinity of the opening 71a downstream of the sliding portion between the toner supply roller 25K and the developing roller 23K in the direction of movement of the developing roller surface, a toner layer regulation made of a springy thin plate such as stainless steel or an elastic material such as urethane rubber. A thin layer blade 26K as a member is provided such that the vicinity of one end thereof is in contact with the developing roller 23K.

In the developing container 71, a first agitator 73 for stirring the toner in the container and conveying the toner to the toner supply roller 25K and the developing roller 23K side.
The second agitator 7 also stirs the toner in the developing container 71 and conveys the toner to the first agitator 73 side.
4 are provided. The first and second agitators 73 and 74 are disposed such that their rotation axes are parallel to the toner supply roller 25K and the developing roller 23K. Both agitators 73 and 74 are provided with a film-like elastic sheet or the like at the tip thereof so that the tip thereof slides on the bottom surface of the developing container 71.
The toner in the developing container 71 can be efficiently transported, and the remaining amount of the toner in the developing container 71 can be reduced. It is desirable that the rotation speed of the agitators 73 and 74 be as low as possible so as not to apply extra stress to the toner.

The black developing device 7 is movable in the horizontal direction with respect to the photoreceptor belt 1, is separated from the photoreceptor belt 1 during non-development, and the developing roller 23K approaches or contacts the photoreceptor belt 1 during development. A separating operation for moving to the developing position is performed. Normally, the black developing device 7 is retracted to a position where the developing roller 23K does not come into contact with the surface of the photoreceptor belt facing the same, as shown in FIG. When developing an electrostatic latent image corresponding to a black image formed on the photoreceptor belt 1,
By the action of the cam 45, the entire developing device 7 is moved in a horizontal direction along a guide member (not shown), and the developing roller 23K is brought into contact with a surface of the photoreceptor belt in a state where a predetermined nip is formed.

The developing roller 23K is a photosensitive belt 1
In a state where the developing roller 23K is not in contact with the developing container 23, the driving of the developing roller 23K is stopped, the developing roller 23K is controlled not to rotate, the toner scatters and leaks from the opening 71a of the developing container 71, the developing roller 23K, and other developing devices. 7 prevents early deterioration of the components.

Next, the color developing unit 6 will be described. As shown in FIG. 2, the color developing unit 6 has an inner casing 21 that is a rotating body provided rotatably about a rotation axis O. The inner casing 21 is driven by a drive mechanism (not shown) as indicated by an arrow D in FIG. It can rotate in the direction (clockwise). The inner casing 21 is provided for each of the developing units 6 for yellow, magenta, and cyan.
Y, 6M, and 6C are integrally held. The developing units 6Y, 6M, and 6C of the respective colors have the same form and are configured to perform the same operation. Each of the developing units 6Y, 6M and 6C has
Cylindrical developing rollers 63Y and 63 as a developer carrier
M, 63C are provided. Each developing roller 63Y, 6
3M and 63C are arranged so that a part thereof is exposed to the outside from an opening formed in the inner casing 21, and are rotated in the direction of arrow C in the figure by a drive mechanism (not shown) in synchronization with color information. Driven to develop the corresponding electrostatic latent image. At this time, the black developing device 7 is held at a position where the developing roller 23K is separated from the surface of the photosensitive belt 1 by the cam 45 and a spring (not shown).

Each of the developing devices 6Y, 6M, and 6C is a developing device using a non-magnetic one-component developer, and contains a yellow toner, a magenta toner, and a cyan toner, respectively.
Then, as the inner casing 21 rotates about the rotation axis O, each of the developing devices 6Y, 6M, and 6C is selectively moved to the developing position, and the photosensitive belt 1 is sequentially moved as described above.
Is developed.

Since the developing units 6Y, 6M, and 6C of the respective colors have the same form and are configured to perform the same operation, only the developing unit 6C of one color (cyan) will be described below.

In FIG. 2, an opening is formed above the cyan developing device 6C. In this opening, a developing roller 63C is provided so as to face the photoreceptor belt 1. The developing roller 63C is moved in a direction indicated by an arrow C in FIG. Is driven to rotate. Below the developing roller 63C, a toner supply roller 64C as a toner supply member made of an elastic material such as foamed urethane is provided so as to rub against the developing roller 63C. The toner supply roller 64C is rotatably driven so as to move in the same direction as the surface movement direction of the roller 63C at a rubbing portion with the development roller 63C at a predetermined peripheral speed ratio with the development roller 63C.

In the vicinity of the opening, on the downstream side of the rubbing portion between the developing roller 63C and the toner supply roller 64C in the direction of movement of the developing roller surface, an elastic material such as stainless steel or a urethane rubber is used. Blade 65C as a toner layer regulating member made of a body
Is provided so that the vicinity of one end thereof is in contact with the surface of the developing roller. Further, a screw-shaped first toner conveying member 66C described later conveys toner as a developer from the near side to the far side in FIG.

A toner container (not shown) is provided at one end side (front side in FIG. 2) of the color developing unit 6 in the developing roller axial direction. The screw-shaped first
The toner conveying member 66C is arranged in parallel with the developing roller 63C and the toner supply roller 64C from the toner storage portion to the side plate of the developing device on the rear side of the color developing device unit 6 in FIG.

The inner casing 21 is disposed so that a part thereof is in contact with the toner supply roller 64C. The first toner conveying member 66C is formed by the developing roller 63C, the toner supply roller 64C and the inner casing 21. Is formed around the toner conveying space.

The screw-shaped first toner conveying member 66C is provided with a developing roller 63C and a toner supplying roller 64 so as to convey the toner from the near side to the far side in FIG.
In conjunction with C, they are rotationally driven so as to rotate at a predetermined linear velocity ratio with them. Due to this rotation, the first toner conveying member 66C conveys the toner from the toner storage section into the toner conveying space, and supplies the toner onto the toner supply roller 64C. The toner supplied on the toner supply roller 64C is supplied while being charged on the surface of the developing roller 63C by the toner supply roller 64C, and is carried on the surface of the developing roller 63C. The toner carried on the surface of the developing roller 63C is thinned to a uniform and predetermined thickness by the thin layer blade 65C, and is used for developing the electrostatic latent image formed on the surface of the photoreceptor belt 1. This development
It is performed by contact development or non-contact development.

The toner not used in the developing step is conveyed by the first toner conveying member 66C to the rear end of the developing device on the side opposite to the front side where the toner container is provided. The toner reaches a toner circulating portion provided outside the effective diameter portion in the axial direction of the developing roller 63C and the toner supply roller 64C, and the toner drops to the lower part of the developing device by gravity.

At the bottom of the developing device in the developing position, a screw-shaped second toner conveying member 67C is provided.
The developing roller 63C, the toner supply roller 64C and the first
Is disposed in parallel with the toner conveying member 66C, and is rotationally driven to convey the toner in a direction opposite to that of the first toner conveying member 66C. Transport. By appropriately setting the toner transport amount of the first toner transport member 66C and the second toner transport member 67C, the toner amount can be detected without performing the detection of the toner amount in the developing device and the complicated toner supply amount control. A small color developing unit 6 can supply toner onto the supply roller 64C, has a large degree of freedom in layout, and has a small cross-sectional occupation ratio with respect to the photosensitive belt 1. (Hereinafter, margin)

Next, the developing rollers 23K, 63C, 63Y and 63M, which are characteristic parts of the developing device according to the present embodiment, will be described. Here, each of the developing rollers 23K, 63C,
Since the developing rollers 63Y and 63M have the same configuration, the developing rollers 23K, 63C, 63Y and 63M are hereinafter simply referred to as developing rollers.

The developing roller has a surface on which the developer is carried so that the friction coefficient μs satisfies 0.1 ≦ μs ≦ 0.4. FIG. 3 is a graph showing the relationship between the friction coefficient μs of the developer carrying surface of the developing roller and the amount of toner transport m / a (toner weight per unit area) on the developer carrying surface. Note that the conditions at the time of collecting the data of the graph shown in FIG. 3 are as follows: the potential difference between the developing roller, the toner supply roller and the thin layer blade is 200 V; Interchange (AC)
A bias (Vp-p) was applied. The surface roughness Rz of the developing roller was set to 2 to 4. As the developing roller, a roller made of urethane rubber as a base material and coated with a fluorine-based (or silicon-based) conductive resin is used. The friction coefficient μs of the surface is determined by the conductive resin coating. It was changed according to the thickness. Friction coefficient μs
Was performed by placing the developing roller in a horizontal position and contacting a muse (metal probe) made by HEIDON in the longitudinal direction.

As can be seen from the measurement data shown by the solid line in FIG. 3, the friction coefficient μs of the developer carrying surface of the developing roller is 0.1
When the value is less than the above range, the toner conveying force of the developing roller is reduced, and the thin toner layer is disturbed (haze). Also, the friction coefficient μ
When s exceeds 0.4, the toner conveying force of the developing roller is excessively increased, and the toner conveying amount m / a of the developer carrying surface becomes excessive, so that the background image is stained on the developed image.

Accordingly, by forming the developer carrying surface of the developing roller in such a state that the friction coefficient μs satisfies 0.1 ≦ μs ≦ 0.4, the toner conveyance amount m / a is reduced.
A desired image density is obtained, and the image is set to an appropriate area where background stain does not occur.

Further, in the case of a developing roller composed of a conductive resin roller formed of a conductive resin single layer, as can be seen from the measurement data indicated by the dotted line in FIG. 3, the friction coefficient μs of the developer carrying surface is 0.2 to 0.2. Since it is in the range of 0.3, the toner transport amount m / a in an appropriate area can be obtained. As the conductive resin roller, for example, PP (polypropylene),
There are PA (polyamide), PAE (polyamide / elastomer), EEA (ethylene ethyl acrylate) and the like mixed with a conductive agent.

FIG. 4 shows the upper and lower limits of the penetration of the thin layer blade of the developing roller (friction coefficient μs = 0.2 and friction coefficient μs = 0.4) of the same material as the developing roller shown in FIG. 6 is a graph showing a relationship between (mm) and a toner conveyance amount m / a. Here, the configuration of the developing device used is the same as that shown in FIG. 2, and the thin layer blade is pressed against the developing roller in a trailing relationship so as to be along the tangential direction of the developing roller. Other conditions are the same as those in FIG.

As is apparent from the measurement range of the bite amount of the thin layer blade in FIG. 4, the setting range of the bite amount of the thin layer blade is about 0.6 mm, and there is a margin in the lower limit of the bite amount. . Therefore, like this developing device,
So that the thin layer blade is in the tangential direction of the developing roller,
By contacting the developing roller with the developing roller in a trailing relation, the thin toner layer formed on the developing roller can be controlled by the friction coefficient of the developing roller surface and the pressing force of the thin layer blade. The setting range of the bite amount of the blade can be widened.

[0046]

According to the present invention, the developer carrying surface of the developing roller has a friction coefficient μ of 0.1 ≦ μ ≦
By being formed in a surface state such as 0.4,
Since the toner conveyance amount of the developing roller is stabilized, there is an excellent effect that a high-quality image can be obtained.

According to the second aspect of the present invention, since the developing roller is formed by a single-layer roller made of a conductive resin,
There is an excellent effect that the molding of the developing roller can be simplified and the apparatus can be made inexpensive.

According to the third aspect of the present invention, the surface of the developing roller is formed of a conductive resin layer, and the toner conveying force and the charging property of the developing roller are affected by the coefficient of friction of the core metal as the base material. Therefore, there is an excellent effect that the degree of freedom in selecting the material of the developing roller base material is increased.

According to the fourth aspect of the present invention, the thin-layer blade for thinning the developer carried on the developing roller is provided with respect to the developing roller so as to be along the tangential direction of the developing roller. By pressing the toner in a trailing relationship, the thin toner layer formed on the developing roller can be controlled by the friction coefficient of the surface of the developing roller and the pressing force of the thin layer blade. As in the case of the counter method in which the thin-layer blades are arranged, it is not necessary to obtain the fine positioning accuracy of the thin-layer blades, and there is an excellent effect that the setting range of the biting amount of the thin-layer blade with respect to the developing roller can be widened.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a color image forming apparatus including a developing device according to an embodiment.

FIG. 2 is a schematic configuration diagram of a developing device in the color image forming apparatus.

FIG. 3 is a graph showing a relationship between a coefficient of friction of a developing roller of the developing device and a toner conveyance amount.

FIG. 4 is a graph showing the relationship between the amount of bite of a thin blade at the upper and lower limits of the developing roller and the amount of toner transported.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 photoconductor belt 6 color developing unit 7 black developing device 23K, 63C, 63M, 63Y developing roller 25K, 64C, 64M, 64Y toner supply roller 26K, 65C, 65M, 65Y thin blade μs developer carrying surface of developing roller Coefficient of friction m / a Amount of toner transported on developer carrying surface of developing roller

Claims (4)

[Claims] In a developing apparatus having a developing roller for carrying and transporting a one-component developer, the developer carrying surface of the developing roller is adjusted so that a friction coefficient μs is 0.1 ≦ μs ≦ 0.4. A developing device characterized in that the developing device is formed in a suitable surface state. 2. The developing device according to claim 1, wherein said developing roller is formed of a conductive resin. 3. The developing device according to claim 1, wherein a surface of said developing roller is made of a conductive resin layer. 4. The developing device according to claim 1, wherein a thin layer blade for thinning the developer carried on the developing roller is disposed on the developing roller so as to be along a tangential direction of the developing roller. A developing device that is in pressure contact with the device in a trailing relationship.