JPH06308810A - Image forming device - Google Patents

Abstract

PURPOSE:To make it possible for an image forming device to cope with an environmental change. CONSTITUTION:The image forming device is equipped with a developing device comprised of a developer carrier 34 which is in contact with or near to an electrostatic latent image carrier 32, composed of a conductive, elastic body, and carries developer 33 to the electrostatic latent image carrier 32 by rotating, a power source 35 for applying a voltage to the developer carrier 34, and a layer thickness control member 31 which is pressed to the developer carrier 34 at a prescribed pressure, electrifies the developer 33 to an prescribed amount of charges, and exerts control so that the thickness of the developer 33 on the developer carrier 34 is constant. In the image forming device, a constant current power source 30 which causes a prescribed current to flow between the layer thickness control member 31 and the developer carrier 34 is connected.

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 such as a printer or a copying machine having a one-component developing device, and more particularly, to an environment by injecting a certain amount of electric charge from a layer thickness regulating member into a developer. The present invention relates to an image forming apparatus that obtains an image with good print quality regardless of the temperature.

Copiers and printers using electrophotography are widely used because of their high speed, high resolution and low noise. In electrophotography, generally, a uniformly charged surface of a photoconductor is exposed by a laser or the like according to image information to form an electrostatic latent image. After that, a charged toner (developer; fine resin powder used for developing the electrostatic latent image) is made to adhere to the electrostatic latent image on the photoconductor to be visualized by a developing process. After the visible image of this toner is electrostatically transferred onto a recording paper, it is fixed by heat, pressure, light or the like to obtain a copy or print.

Conventionally, in the developing process, a two-component developing method in which a carrier which is a magnetic powder and a resinous toner are mixed and the toner is charged by frictional charging has been adopted. However, in the two-component development, it is necessary to control the mixing ratio of the carrier and the toner, the size of the device becomes large because the carrier is required in the developing device, and the frictional charging is used to charge the toner. There is a problem that the toner charge amount changes.

In order to solve the above-mentioned problems, in recent years, development and commercialization of an image forming apparatus having a one-component developing device in which only toner is required in the developing device and the device configuration is simplified has been actively carried out. ing.

[0005]

2. Description of the Related Art FIG. 5 is a block diagram of a laser printer, and FIG. 6 is a block diagram of a conventional developing device. FIG. 5 shows the printing principle of the laser printer. The basic configuration of the apparatus is that a uniform charging device such as a corona charger, a conductive brush brush charger, a conductive roller charger is provided around a photosensitive drum 1 such as an organic photosensitive member, a Se photosensitive member, and an a-Si photosensitive member. 2. Laser optical system, LED
Image exposure device 3, such as an optical system, an EL optical system, a liquid crystal optical system,
Two-component magnetic brush developing machine, magnetic one-component developing machine, non-magnetic one-component developing machine, developing machine 4, corona discharger, transfer roller 5 such as conductive roller transfer machine, brush cleaner, cleaner 6 such as blade cleaner, A static elimination lamp 7 is arranged, and a fixing device 9 is arranged on a conveying path for conveying the recording paper 8.

First, the surface of the photosensitive drum 1 is uniformly charged by the uniform charger 2. Next, the surface of the photosensitive drum is image-exposed by the image exposure device 3 according to a predetermined pattern corresponding to the image. In the exposed portion of the photosensitive drum 1, the charge is reduced and an electrostatic latent image is formed. When the photoconductor drum 1 rotates and passes through the developing device 4 (here, a one-component developing device is shown), the pre-charged toner adheres to the electrostatic latent image on the photoconductor drum 1 to form toner. An image is formed.

On the other hand, the paper 8 on which the image is printed is supplied to a position where it comes into contact with the toner image formed on the photosensitive drum 1. The transfer unit 5 is installed below the photoconductor drum 1 with the paper 8 sandwiched therebetween, charges the paper 8 with a polarity opposite to the toner charge, and electrostatically transfers the toner image on the photoconductor drum 1 onto the paper 8. The sheet 8 carrying the toner image is fixed on the fixing device 9
While passing through the sheet, it is fixed on the sheet 8 by heat and pressure, and the printing is completed.

On the other hand, the toner remaining on the photosensitive drum 1 after the toner image is transferred onto the paper 8 is cleaned by the cleaner 6. Further, the photoconductor drum 1 is provided with a static elimination lamp 7
Thus, the residual charge is removed, the initial state is restored, and the printing operation is repeated.

Next, the construction of the one-component developing machine 4 which is the main object of the present invention will be described with reference to FIG. In the figure, reference numeral 11 denotes a developer carrying member, which conveys and supplies the toner 13 to the developing unit of the photosensitive drum 1 by rotating around a metal rotating shaft 12. In the case of this apparatus, the toner 13 is a non-magnetic and insulating toner made of resin. As the material of the developer carrying member 11, an elastic body in which carbon is added to urethane rubber, silicon rubber, porous urethane sponge or the like to give conductivity is used.

Power is supplied to the developer holding member 11 through the rotary shaft 12.
When a developing bias voltage is applied by 14, the toner image is stably formed on the photosensitive drum 1. This voltage is negative, for example, when an organic photoconductor is used for the photoconductor drum 1.

Reference numeral 15 denotes a layer thickness regulating member which charges the toner 13 to a predetermined charge amount and regulates the layer thickness of the toner layer 16 on the developer carrying member 11 to a constant thickness. The layer thickness regulating member 15 is a holder 17
It is fixed to. The holder 17 is rotatably mounted around a rotation fulcrum 18, and is pressed by a spring 19. Therefore, the layer thickness regulating member 15 is a developer carrying member.
It is pressed in the direction of 11.

The toner 13 is the developer carrying member 11 and the layer thickness regulating member.
When passing between the toner 13 and the toner 15, the toner 13 and the layer thickness regulating member 15 are triboelectrically charged, so that the toner 13 is charged. Further, a voltage is applied from the power source 20 between the developer carrier 11 and the layer thickness regulating member 15 to inject charges from the layer thickness regulating member 15 into the toner 13. Therefore, the toner 13 is charged by frictional charging and charge injection.

Reference numeral 21 is a reset member, which is the photosensitive drum 1.
The toner 22 remaining on the developer carrying member 11 after the electrostatic latent image is developed is collected, and the toner is left on the developer carrying member 11.
Supply 13. This has an auxiliary function of making the layer thickness of the toner layer 16 on the developer carrier 11 uniform. A conductive sponge is used for the reset member 21. A rotating shaft 23 made of metal applies a voltage to the reset member 21 made of a conductive material.

A voltage is applied between the reset member 21 and the developer carrying member 11 by a power source 24 so that the toner 13 negatively charged on the developer carrying member 11 can be electrically supplied in addition to mechanically. ing.

[0015]

In the non-magnetic one-component developing method described above, the resistance of the toner 13 and the developer carrying member 11 changes due to environmental changes, and the layer thickness regulation for regulating the charge amount of the toner 13 is regulated. The amount of charge injected from the member 15 into the toner 13 changes.

FIG. 7 is a diagram showing the environmental dependency of the toner layer potential in the conventional developing device, and FIG. 8 is a diagram showing the environmental dependency of print density and fog in the conventional developing device. (0 ° C, 20% RH), RT (25 °
C, 60% RH) and HH (40 ° C., 80% RH) are experimentally obtained. According to FIG. 7, the toner layer on the developer carrying member 11 changes depending on the environment.
It can be seen that the charge amount of 16 fluctuates, and the charge amount of the toner layer 16 changes the amount of toner adhered to the photosensitive drum 1 and affects the toner image formed on the photosensitive drum 1. . As a result, as shown in FIG. 8, the occurrence of fog is remarkable in HH.

In view of the above problems, it is an object of the present invention to provide an image forming apparatus that stabilizes the toner charge amount on the development carrier 11 and obtains good print quality without being influenced by the environment. .

[0018]

As shown in FIG. 1 of the principle of the present invention, the present invention makes contact with or approaches the electrostatic latent image carrier 32, is composed of an elastic body having conductivity, and rotates. Thereby, the developer carrier 34 that conveys the developer 33 to the electrostatic latent image carrier 32, the power source 35 that applies a voltage to the developer carrier 34, and the developer carrier 34 at a predetermined pressure. In an image forming apparatus including a layer thickness regulating member 31 which is disposed by pressing and which charges the developer 33 to a predetermined charge amount and regulates the developer 33 on the developer carrier 34 to a constant thickness, A constant current power supply 30 is connected to the layer thickness regulating member 31.

[0019]

When the developer (toner) 33 passes between the layer thickness regulating member 31 and the development carrier 34, the toner 33 and the layer thickness regulating member
A charge is applied to the toner 13 by frictional charging with the toner 31, but at the same time, a constant amount of charge is injected from the constant current power source 30 into the toner 33 via the layer thickness regulating member 31. This is because even if the resistance of the developing carrier 34, the toner 33, and the like change due to the environment, a constant current flows by the constant current power supply 30, and the amount of injected charges (integrated value of current) becomes constant.
Note that this point has been confirmed experimentally as described later.

As described above, by using the constant current power source 30 instead of the constant voltage power source as the power source for injecting the charges from the layer thickness regulating member 31, it is possible to keep the toner charge amount constant. It is possible to obtain stable printing against environmental changes.

[0021]

FIG. 2 is a block diagram of an embodiment, FIG. 3 is a diagram showing the environmental dependence of the toner layer potential which is improved, and FIG. 4 is a diagram showing the environmental dependence of improved print density and fog. .

In FIG. 2, reference numeral 1 denotes a photosensitive drum, for example, an aluminum drum coated with a function-separated organic photosensitive member. In this embodiment, the photosensitive drum 1 is rotated in the direction of the arrow at a peripheral speed of 23 mm / S. The surface of the photosensitive drum 1 is uniformly charged in advance by a charging brush (not shown) so that the surface potential becomes about -650 V, and then an electrostatic latent image is formed by a laser optical unit (not shown).

Reference numeral 42 denotes a developing roller as a developer carrying member, which conveys and supplies the developer 43 to the electrostatic latent image on the photosensitive drum 41 by rotating about a metal rotating shaft. In this apparatus, the developer 43 is a non-magnetic insulating material and uses a resin one-component toner. The toner 43 is a styrene acrylic toner having a volume resistivity of 10 ¹¹ Ω · cm, an average particle diameter of 8 μm, and a silica external additive.

The developing roller 42 has a volume resistivity of 10 ⁸ Ω.
A silicone-containing urethane rubber roller having a cm and a hardness of about 45 degrees (JIS-A hardness meter) was used. Then, the peripheral speed was rotated at 46 mm / s, which is 2.0 times the peripheral speed of the photosensitive drum 41.

Reference numeral 44 denotes a variable power source which can vary the output voltage by a signal from the outside and is used to apply a developing bias to the developing roller 42. This voltage is applied to the photosensitive drum 4
The surface potential of No. 1 was -650V, while it was set to about -350V.

Reference numeral 45 denotes a charging blade as a layer thickness regulating member, which charges the toner 43 to a predetermined charge amount and regulates the layer thickness of the toner 46 on the developing roller 42 to a constant thickness. The charging blade 45 is fixed to the support block 47. The support block 47 is mounted rotatably around a rotation fulcrum 48, and receives a constant pressure by a spring 49. Therefore, the charging blade 45 is pressed in the direction normal to the center of the developing roller 42.

The charging blade 45 is made of stainless steel (SUS304-CSP-3 / 4H) and has a 0.1 mm-thick plate (R = 0.
05mm) and the bending length from the support block 47 is 4mm
And the pressure applied to the developing roller 42 was set to be 35 gf / cm.

Reference numeral 51 is a reset roller as a reset member. The reset roller 51 is the photosensitive drum 41.
By collecting the toner 52 remaining on the developing roller 42 after developing the electrostatic latent image thereon and supplying the toner 43 to the developing roller 42, the layer thickness of the toner 46 on the developing roller 41 is reduced. It has an auxiliary function to make it uniform.
The reset roller 51 has about 40 cells / inch,
An ester type urethane sponge (Everlite SK-E manufactured by Bridgestone) having a volume resistivity of 10 ⁴ Ω · cm was used and the peripheral speed was set to 70 mm / s.

Between the reset roller 51 and the developing roller 42, the toner 4 negatively charged on the developing roller 42 is provided.
A voltage is applied by the power supply 53 so that the 3 can be electrically supplied. This voltage is about -100V.

Numerals 54 and 55 are paddle rollers for moving the toner 43 to the vicinity of the developing roller 42 and are made of resin. The experimental results obtained with the developing device having the above-described structure are shown in FIGS. Note that FIGS. 7 and 8 are obtained from the same developing device as this embodiment, and will be described below in comparison with FIGS. 7 and 8.

In FIG. 7, when a constant voltage source is connected to the charging blade 45 and a voltage is applied to inject charges into the toner 43, a change in the current value flowing through the charging blade 45 and a change in the roller due to a change in environment. FIG. 8 shows changes in the toner layer potential, and FIG. 8 shows changes in the value of the current flowing through the charging blade 45, changes in the print density on the paper, and changes in the fog on the drum due to changes in the environment. Development roller 4
2 causes the resistance value to change, but when the resistance value or the like changes, the current value flowing into the resistance value changes. From Figure 7, RT (25 °
C, 60% RH) was 1.85 μA, but the current value flowing through the blade was 0.61 at LL (0 ° C, 20% RH).
At HH (40 ° C., 80% RH), the value changes to 2.7 μA, and accordingly, the toner layer potential on the developing roller 42 changes significantly at LL and HH as compared with RT.

The toner layer potential on the developing roller 42 is one of the parameters for determining the toner charge amount that affects the print quality, so that the change in this value causes the change in the charge amount. Further, as shown in FIG. 8, the print density on the paper is reduced in the LL environment, and the fog on the drum is significantly increased in the HH environment.

Next, when a constant current power source 50 is connected to the charging blade 45 and a constant current is applied to inject charges into the toner, the change of the toner layer potential on the roller due to the environmental change is shown in FIG.
FIG. 4 shows changes in print density on paper and fog on the drum. From FIGS. 3 and 4, 1.85 μA from the constant current power source 50 connected to the charging blade 45 regardless of environmental changes
Since a constant current of 1 is applied to the blade, the potential of the toner layer on the developing roller 42 is stable in all environments, and therefore the amount of charge is also stable. Therefore, regardless of environmental changes, a sufficient print density of 1.3 and fog on the drum of 0.2 or less can be achieved, and stable and good printing can be obtained.

The toner layer potential was measured by using a surface potentiometer in a state where the developing roller 42 was installed at a position in contact with the photosensitive drum 41. [Other Embodiments] In the above-described embodiments, the example in which the developing roller 42 is made of silicon-containing urethane rubber is shown. However, silicon rubber, silicon-based sponge, fluorine-based sponge, porous polyurethane sponge or the like is used. Of course, the effect of the present invention is not lost.

The reset roller 51 includes 40 cells.
Other conductive sponge rollers such as Bridgestone Everlight TS-E of 80 / inch and EP-T-51 of 80 cells / inch are used as the charging means for uniformly charging the photosensitive drum 41, in addition to the brush charger. A charger, a roller charger, a scorotron, etc., and an image exposure device 3 (FIG. 5) include a laser optical system, an LED optical system, a liquid crystal shutter optical system, an EL (electroluminescence) optical system, a dielectric and a discharge needle. In combination with the system, a belt transfer device, a corona transfer device or the like can be used as the transfer device 5 in addition to the roller transfer device.

Although the above-mentioned embodiment is applied to the cleanerless type, a cleaning means such as a blade cleaner, a fur brush cleaner, or one that electrostatically removes the developer can be used. Further, as the toner charging method, the present invention can be applied by using a rubber elastic blade, a resin bar, a metal bar, a charging roller or the like in addition to the charging blade 45 used in this embodiment. As for the toner 43, in addition to the styrene acrylic polymer toner, the polyester polymer toner,
Styrene acrylic crushed toner, polyester crushed toner, or the like may be used, and a smaller particle size, for example, 6 μm may be used.

[0037]

As described above, according to the present invention,
For the layer thickness regulating member that forms the toner layer on the developer carrier,
By connecting a constant current source, the amount of charge injection is always constant. Therefore, it is possible to provide an image forming apparatus capable of obtaining an image of good print quality even if the environment changes or the components deteriorate.

[Brief description of drawings]

FIG. 1 is a principle diagram of the present invention.

FIG. 2 is a configuration diagram of an embodiment.

FIG. 3 is a diagram showing an environment dependency of an improved toner layer potential.

FIG. 4 is a diagram showing improved print density and environmental dependence of fog.

FIG. 5 is a configuration diagram of a laser printer.

FIG. 6 is a configuration diagram of a conventional developing device.

FIG. 7 is a diagram showing the environmental dependence of the toner layer potential in the developing device of the conventional example.

FIG. 8 is a diagram showing environmental dependence of print density and fog in a developing device of a conventional example.

[Explanation of symbols]

1 photoconductor drum 2 uniform charger 3 image exposure device 4 developing device,
Developing device 5 Transfer device 6 Cleaner 7 Eliminating lamp 8 Recording paper 9 Fixing device 11 Developer carrier 12 Rotating shaft 13 Developer,
Toner 14 Power supply 15 Layer thickness control member 16 Toner layer 17 Holder 18 Rotation fulcrum 19 Spring 20 Power supply 21 Reset member 22 Developer, toner 23 Rotation shaft 24 Power supply 25, 26 Paddle roller 30 Constant current power supply 31 Layer thickness control member 32 Electrostatic Latent image carrier 33 Developer 34 Developer carrier 35 Power supply 41 Photosensitive drum 42 Development roller 43 Developer, toner 44 Variable power supply 45 Charging blade 46 Toner 47 Instruction block 48 Rotation fulcrum 49 Spring 50 Constant current power supply 51 Reset roller 52 Toner 53 Power supply 54,55 Paddle roller

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Kodama 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Hiroki Kitagawa 1015, Kamedotachu, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited

Claims (1)

[Claims] 1. An electrostatic latent image carrier (32), a developer carrier (34) which conveys a developer (33) to the electrostatic latent image carrier (32), and the developer carrier (34). 34) An image forming apparatus having a developing device (4) including a layer thickness regulating member (31) for regulating the developer (33) to a constant thickness, wherein the developing device (4) is a layer thickness regulating member. Constant current power supply (3
The image forming apparatus is characterized in that it is configured to be connected to (0).