JPH11167275A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device which restricts a toner layer on a developing roller to a proper thickness and prevents fog and so on resulting from a decrease in an amount of electrification. SOLUTION: To the surface of the developing roller 10, toner is supplied from a toner hopper via a toner supply roller 6. On the developing roller 10, a layer thickness regulation roller 13 is so disposed as to rotate in contact with it. The outside diameters of the developing roller 10 and layer thickness regulation roller 13 are selected so that the ratio of the outside diameter d2 of the layer thickness regulation roller 13 to the outside diameter d1 of the developing roller 10, d2/d1, is below 0.75. Also, the position of the layer thickness regulation roller 13 is adjusted so that an angle θ formed between a straight line connecting the rotation center of the developing roller 10 and the rotation center of the layer thickness regulation roller 13 and a vertical line passing through the rotation center of the developing roller 10 during development is 5 or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus for visualizing an electrostatic latent image formed on a photoreceptor with toner particles in an electrophotographic apparatus or an electrostatic recording apparatus.

[0002]

2. Description of the Related Art Electrophotographic apparatuses which use dry toner have been the mainstream, and have been put into practical use as many copiers, laser printers, and plain paper facsimile machines, and have made remarkable developments. This electrophotographic device is a device to which the electrophotographic process technology is applied.After the electrostatic latent image formed on the photoreceptor is visualized by toner particles, it is transferred to recording paper, and printing is completed through a fixing process. I do.

[0003] A conventional image forming apparatus will be described below. FIG. 3 is a schematic cross-sectional view of a conventional image forming apparatus, and FIG. 4 is a schematic cross-sectional view around a developing roller during printing in the conventional image forming apparatus.

In FIG. 3 and FIG. 4, a photosensitive member 1 is made of a metal drum such as aluminum as a base material, and a photosensitive receiving layer such as selenium (Se) or an organic photoconductor (hereinafter referred to as OPC) is formed on an outer peripheral surface thereof. Is applied in a thin film form. The charger 2 disposed close to the photoreceptor 1, which is an electrostatic latent image carrier, includes a charging wire 2a such as a tungsten wire, a metal shield plate 2b, and a grid plate 2c. In the charger 2, the charging line 2a causes corona discharge, and uniformly charges the photoconductor 1 via the grid plate 2c. The exposure light beam 4 emitted from the exposure optical system 3 is obtained by subjecting an image signal to light intensity modulation or pulse width modulation by a laser driving circuit (not shown), and forms an electrostatic latent image on the photoconductor 1.

Next, the developing device 5 will be described. The toner supply roller 6 is rotatably supported at both ends by a toner hopper 7 and supplies the toner 9 stirred and conveyed by a toner stirring member 8 formed in a rectangular shape to the surface of a developing roller 10 as a toner carrier. A toner supply bias power supply 11 is connected to the metal shaft portion via a protection resistor 12.

The layer thickness regulating roller 13 is made of stainless steel and is arranged so that a straight line connecting the center of the developing roller 10 and the center of the layer thickness regulating roller 13 coincides with the vertical direction.
The developing roller 10 rotates in the same direction as the developing roller 10 in contact with the developing roller 10. Further, a bias power source 14 is connected to the layer thickness regulating roller 13. Further, the layer thickness regulating roller 13
A scraper 15 made of a stainless steel plate for scraping off the toner 9 attached to the layer 9 is mounted in contact with the layer thickness regulating roller 13.

The developing roller 10 and the toner supply roller 6 are made of a metal such as stainless steel, and elastic members such as urethane and silicone are formed in a layer on the outer peripheral surface thereof. ing. The outer diameters of the toner supply roller 6, the developing roller 10, and the layer thickness regulating roller 13 are 18 mm, 15 mm, and 14 mm, respectively.

The toner agitating member 8 draws a circular locus with the rotation of the toner supply roller 6, agitates the toner 9 in order to prevent the toner 9 contained in the toner hopper 7 from aggregating, and transfers the toner 9 to the toner supply roller 6. Transported to Toner 9 supplied by toner supply roller 6
Is formed in a thin layer state on the outer peripheral surface of the developing roller 10 by being layered by the layer thickness regulating roller 13 and frictionally charged. Thereafter, the developing roller 10 comes into contact with or close to the photoconductor 1, and the toner 9 is transferred and adhered to the portion of the photoconductor 1 on which the electrostatic latent image is formed by a bias voltage applied by the developing bias power supply 16, and the static electricity is applied. The latent image is visualized.

The recording paper 18 stored in the recording paper cassette 17 is sent out from the recording paper cassette 17 to conveyance rollers 20a and 20b one by one by a half-moon shaped paper supply roller 19. The fed recording paper 18 is transported by the transport roller 2.
It is transported in the direction indicated by arrow A by 0a and 20b.

A registration roller 21 is provided for temporarily stopping the recording paper 18 in order to match the recording paper 18 with the toner image formed on the photosensitive member 1.
It is in contact with the driven roller 22.

The transfer unit 23 includes a transfer line 23a made of a tungsten wire or the like and a shield plate 23 made of a metal plate.
b. When a high voltage is applied to the transfer line 23a, the transfer line 23a causes a corona discharge to transfer the toner image on the photoconductor 1 onto the recording paper 18.
Further, a fixing device 26 including a heat roller 24 having a heat source therein and a pressure roller 25 forms a recording paper 18.
The toner image transferred onto the recording paper 18 receives pressure and heat as the heat roller 24 and the pressure roller 25 nip and rotate.
, And the printing is completed.

The cleaner section includes a cleaning blade 27 for scraping residual toner on the photoconductor 1 and a toner collecting container 28 for storing the scraped residual toner. 1 is provided with a static eliminator 29 for electrostatically cleaning 1.

[0013]

However, in the above-described conventional image forming apparatus, the layer thickness of the toner layer on the developing roller 10 is slid while rotating the layer thickness regulating roller 13 against the surface of the developing roller 10. It has been adjusted accordingly. In such a layer thickness regulating method, the regulating force of the layer thickness is lower than, for example, a method in which toner is scraped off at an edge portion of the blade and a predetermined layer thickness is established. Therefore, the layer thickness of the toner supplied onto the developing roller 10 becomes excessive, and the developing roller 1
The toner is not sufficiently charged due to the sliding contact between 0 and the layer thickness regulating roller 13, and the toner charge amount is reduced. As a result, there is an inconvenience that the phenomenon of so-called fogging, in which toner adheres to a white background portion of the photoreceptor 1, is likely to occur.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus in which the thickness of a toner layer on a developing roller is suppressed to an appropriate amount and fogging or the like due to a decrease in a charge amount does not occur.

[0015]

According to the present invention, there is provided an image forming apparatus comprising: a developing roller for carrying toner supplied to an electrostatic latent image formed on a photosensitive member; a toner storing section for storing toner; A layer thickness regulation that rotates in contact with a toner supply roller that supplies toner from the toner reservoir to the development roller and a development roller that carries the toner, and regulates a layer thickness of the toner carried on the surface of the development roller to a predetermined value. The ratio d2 / d1 of the outer diameter d1 of the developing roller and the outer diameter d2 of the layer thickness regulating roller is 0.75 or less.

In the image forming apparatus according to the present invention, the ratio d of the outer diameter d1 of the developing roller to the outer diameter d2 of the layer thickness regulating roller is used.
By setting 2 / d1 to 0.75 or less, the sliding contact state between the developing roller and the layer thickness regulating roller is optimized, thereby suppressing the toner layer thickness on the developing roller to an appropriate amount.
It is possible to prevent a decrease in the charge amount of the toner. This makes it possible to obtain a highly reliable image forming apparatus in which fogging and deterioration of toner or deterioration in image quality due to toner filming are prevented.

Further, the image forming apparatus according to the present invention includes a developing roller for carrying toner supplied to an electrostatic latent image formed on a photoreceptor, a toner storing section for storing toner, and a toner storing section. An image forming apparatus comprising: a toner supply roller that supplies toner to a developing roller; and a layer thickness regulating roller that rotates in contact with the developing roller that carries the toner and regulates a layer thickness of the toner on the surface of the developing roller to a predetermined value. In the device,
The angle formed by a straight line connecting the rotation center of the developing roller and the rotation center of the layer thickness regulating roller with a vertical line passing through the rotation center of the developing roller is 5 ° or more.

In the image forming apparatus according to the present invention, by optimizing the position of the outer peripheral surface of the developing roller where the layer thickness regulating roller contacts, the sliding contact state between the developing roller and the layer thickness regulating roller is optimized. Thus, the toner layer thickness on the developing roller can be regulated to an appropriate amount, and a decrease in the charge amount of the toner can be prevented. As a result, it is possible to obtain a highly reliable image forming apparatus in which the image quality is prevented from being reduced due to fogging or deterioration of the toner or toner filming.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An image forming apparatus according to the present invention includes a developing roller for carrying toner supplied to an electrostatic latent image formed on a photoreceptor, a toner reservoir for storing toner,
A layer thickness regulation that rotates in contact with a toner supply roller that supplies toner from the toner reservoir to the development roller and a development roller that carries the toner, and regulates a layer thickness of the toner carried on the surface of the development roller to a predetermined value. The ratio d2 / d1 of the outer diameter d1 of the developing roller and the outer diameter d2 of the layer thickness regulating roller is 0.75 or less.

Thus, the layer thickness of the toner on the developing roller can be suppressed to an appropriate amount, and a decrease in the charge amount of the toner can be prevented. Therefore, it is possible to obtain a highly reliable image forming apparatus in which the image quality is prevented from deteriorating due to toner fogging or deterioration or toner filming.

Further, the image forming apparatus according to the present invention includes a developing roller for carrying toner supplied to an electrostatic latent image formed on a photoreceptor, a toner storing section for storing toner, and a toner storing section. An image including a toner supply roller that supplies toner to the developing roller, and a layer thickness-regulating roller that rotates in contact with the developing roller that carries the toner and regulates the layer thickness of the toner on the surface of the developing roller to a predetermined value. In the forming apparatus, an angle formed by a straight line connecting the rotation center of the developing roller and the rotation center of the layer thickness regulating roller with a vertical line passing through the rotation center of the developing roller is 5 ° or more.

Thus, the thickness of the toner layer on the developing roller can be regulated to an appropriate amount, and a decrease in the charge amount of the toner can be prevented. Therefore, it is possible to obtain a highly reliable image forming apparatus in which the image quality is prevented from deteriorating due to toner fogging or deterioration or toner filming.

Hereinafter, embodiments of the present invention will be described. FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view around a developing roller during printing in the image forming apparatus of FIG. Since the configuration other than the vicinity of the developing roller shown in FIG. 2 is the same as the configuration of the conventional image forming apparatus shown in FIG. 3, detailed description is omitted by assigning the same numbers.

In FIG. 1 and FIG. 2, the tourist object 1 is a negatively charged OPC having an aluminum drum as a base material and an organic photoconductor applied in a thin film on the outer peripheral surface thereof.

The toner supply roller 6 is formed by forming a conductive foam having a resistance value of 10 ⁶ Ωcm or less around a metal shaft. This toner supply roller 6 has an outer diameter of 14
mm, and is in contact with the developing roller 10 with a bite amount of 0.5 mm.
And has a function of scraping off the toner 9 remaining without being developed from the developing roller 10. A toner supply bias power supply 11 is connected to a metal shaft of the toner supply roller 6 via a protection resistor 12.

The developing roller 10 has a single-layered structure in which a metallic shaft is used as a base material and silicone rubber, which is a conductive elastic member having a resistance value of 10 ⁶ Ωcm, is formed on the outer peripheral surface thereof. A developing bias power supply 16 is connected to a metal shaft of the developing roller 10. The rubber hardness of the developing roller 10 is preferably in the range of 5 to 60 degrees, and the surface roughness is preferably 7 μmRz or less. This is because the higher the smoothness of the developing roller 10, the more uniformly a thin layer of toner can be formed.

Although the layer thickness regulating roller 13 is a metal roller such as stainless steel, a silicone resin or a urethane resin may be applied to the outer periphery thereof if necessary. The layer thickness regulating roller 13 is provided with a 50 μm thick scraper made of stainless steel for scraping off the adhered toner.

The thickness regulating roller 13 is 50 to 400 μm, preferably 100 to 200 μm with respect to the developing roller 10.
With the developing roller 10. Thereby, the layer thickness of the toner 9 of the developing roller 10 is regulated. The layer thickness regulating roller 13 rotates in the same direction as the rotation direction of the developing roller 10, and the peripheral speed ratio with respect to the developing roller 10 is set to 0.1 to 0.3. If the peripheral speed ratio is less than 0.1, the layer thickness regulating force of the toner 9 on the developing roller 10 is reduced. Conversely, if the peripheral speed ratio exceeds 0.3, the stress on the toner 9 increases, and the deterioration of the toner 9 and toner filming on the developing roller 10 or the layer thickness regulating roller 13 occur.

The thickness of the toner layer on the developing roller 9 is 0.2 to
1.0mg / cm^Two, Preferably 0.4 to 0.6 mg /
cm^TwoIs set to Developing roller 10 and layer thickness regulating roller
The toner 9 is charged at the contact portion with the toner 13, and
The thickness of the layer is 0.6mg / cm ^TwoOver the toner 9
Insufficient charging, toner charge decreases and fog
It is easy to occur. Particularly, when the layer thickness of the toner is 1.0 mg / c
m^TwoWhen it exceeds, the tendency becomes remarkable and is not preferable. Ma
Conversely, the layer thickness is 0.4 mg / cm^TwoIf less than, print image
, The image density becomes thin, especially 0.2 mg / cm^Two
If it is less than 1, the image density sharply decreases, which is not preferable.

In FIG. 2, a broken line B indicates a vertical line passing through the center of rotation of the developing roller 10 during development, and a broken line C indicates a straight line connecting the center of rotation of the developing roller 10 and the center of rotation of the layer thickness regulating roller 13. , Θ indicate the angle between the broken line B and the broken line C.

The transfer unit 23 includes a transfer wire 23a made of a tungsten wire and a metal shield plate 23b.
The cleaner section includes a cleaning blade 27 and a toner collection container 28. The toner 9 is a non-magnetic one-component toner, and is made of a polyester resin in which carbon, wax, a charge control agent and the like are uniformly dispersed, and uses a negatively charged toner. The bias voltage value of the developing bias power supply 16 is -30.
0 V, the voltage value of the bias power supply 14 to the layer thickness regulating roller 13 is -300 V, the bias voltage value of the toner supply bias power supply 11 is +300 V, and the resistance value of the protection resistor 12 is 22 M.
Ω.

The operation of the image forming apparatus configured as described above will be described below.

The process speed is 96 mm / sec, the peripheral speed of the developing roller 10 is 192 mm / sec, and the peripheral speed ratio to the photosensitive member 1 is 2. The layer thickness regulating roller 13 rotates in contact with the developing roller 10 at a peripheral speed ratio of 0.2 in the same direction as the rotating direction of the developing roller 10 with a bite amount of 200 μm.

The peripheral speed of the toner supply roller 6 is 132 mm
/ Sec. The rotation directions of the photoconductor 1, the developing roller 10, and the toner supply roller 6 are in the directions of arrows shown in FIG. 1, respectively, and the respective contact portions are in frictional contact.

The photoreceptor 1 is uniformly charged to -700 V by the charger 2, and the photoreceptor 1 is exposed to an exposure optical system 3 in accordance with an image signal.
, The potential of the unexposed portion becomes -700 V and the potential of the exposed portion becomes about -100 V, and an electrostatic latent image is formed on the photoreceptor 1. Is done.

After the toner 9 is stirred and conveyed by the toner stirring member 8, the toner 9 is supplied to the surface of the developing roller 10 as a toner carrier by the toner supply roller 6. Further, the layer thickness of the toner is regulated by the layer thickness regulating roller 13, and the toner is frictionally charged to form a thin layer on the outer peripheral surface of the developing roller 10. Thereafter, the toner 9 is transferred and adhered to a portion of the photoconductor 1 where the electrostatic latent image is formed by a bias voltage applied by the developing bias power supply 16 to visualize the electrostatic latent image.

Next, a corona discharge is caused by applying a voltage of 1 kV to the transfer line 23a made of a tungsten wire, and the toner image on the photosensitive member 1 is transferred onto the recording paper 18. The toner image transferred onto the recording paper 18 is pressed and heated by a fixing device 26 composed of a heat roller 24 and a pressure roller 25 and is fixed on the recording paper 18. Thereby, printing is completed.

In the above image forming apparatus, the outer diameter d1 of the developing roller 10 and the outer diameter of the layer thickness regulating roller 13 are adjusted so that the toner layer thickness M / A (mg / cm ² ) on the developing roller 10 becomes an optimum value. An experiment was performed to determine the ratio d2 / d1 of the diameter d2. The experimental results are shown in (Table 1) and (Table 2).

[0039]

[Table 1]

[0040]

[Table 2]

From the above results, the outer diameter d of the developing roller 10
1 and the ratio d2 / d1 of the outer diameter d2 of the layer thickness regulating roller 13 to d
If 2 / d1 ≦ 0.75, an appropriate toner layer thickness of 0.5
A value around mg / cm ² could be obtained.

Further, the toner layer thickness M /
An experiment was performed to determine the position of the layer thickness regulating roller 13 so that A (mg / cm ² ) was optimal. Here, θ is a straight line connecting the rotation center of the developing roller 10 and the rotation center of the layer thickness regulating roller 13 in FIG.
This is an angle formed with a vertical line passing through the center of rotation of 0. And
The layer thickness M / A of the toner when θ was set to various values was determined. The experimental results are shown in (Table 3).

[0043]

[Table 3]

From the above results, it was possible to obtain an appropriate toner layer thickness around 0.5 mg / cm ² when θ ≧ 5 °.

From the above results, an image recording apparatus in which the outer diameter d1 of the developing roller 10 is set to 18 mm, the outer diameter d2 of the layer thickness regulating roller 13 is set to 12 mm, and θ = 7 ° is obtained as a more preferable example. .

[0046]

As described above, according to the present invention, the ratio d2 / d1 of the outer diameter d1 of the developing roller and the outer diameter d2 of the layer thickness regulating roller is determined as follows.
By increasing the relative curvature of the layer thickness regulating roller with respect to the developing roller with d2 / d1 ≦ 0.75, the mechanical layer thickness regulating force of the toner on the developing roller is improved, and thereby the toner on the developing roller is regulated. It is possible to obtain a highly reliable image forming apparatus by suppressing a decrease in the toner charge amount due to an excessive amount and preventing the occurrence of fog and the like.

Further, the angle between a straight line connecting the rotation center of the developing roller and the rotation center of the layer thickness regulating roller to a vertical line passing through the rotation center of the developing roller is θ such that θ ≧ 5 °. By arranging the thickness regulating roller relatively,
An effective toner layer thickness regulation can be performed by utilizing gravity acting on the toner. As a result, it is possible to suppress a decrease in the toner charge amount due to an excessive amount of toner on the developing roller, thereby preventing the occurrence of fog or the like. Further, it is possible to prevent the toner from staying in the wedge formed by the developing roller and the layer thickness regulating roller. It is possible to prevent ming.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of an image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view around a developing roller during printing in the image forming apparatus of FIG. 1;

FIG. 3 is a schematic cross-sectional view of a conventional image forming apparatus.

FIG. 4 is a schematic cross-sectional view around a developing roller during printing in a conventional image forming apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor 5 Developing device 6 Toner supply roller 7 Toner hopper 9 Toner 10 Developing roller 13 Layer thickness regulating roller

Claims (2)

[Claims] A developing roller for carrying a toner to be supplied to an electrostatic latent image formed on a photoreceptor; a toner storing section for storing the toner; and supplying the toner from the toner storing section to the developing roller. An image forming apparatus comprising: a toner supply roller that rotates, a layer thickness regulating roller that rotates in contact with the developing roller that carries toner, and regulates a layer thickness of the toner on a surface of the developing roller to a predetermined value. The ratio d between the outer diameter d1 of the developing roller and the outer diameter d2 of the layer thickness regulating roller.
An image forming apparatus wherein 2 / d1 is 0.75 or less. 2. A developing roller for carrying toner supplied to an electrostatic latent image formed on a photoreceptor, a toner storing section for storing toner, and supplying the toner from the toner storing section to the developing roller. An image forming apparatus comprising: a toner supply roller that rotates, a layer thickness regulating roller that rotates in contact with the developing roller that carries toner, and regulates a layer thickness of the toner on a surface of the developing roller to a predetermined value. An image forming apparatus, wherein an angle between a straight line connecting the rotation center of the developing roller and the rotation center of the layer thickness regulating roller to a vertical line passing through the rotation center of the developing roller is 5 ° or more.