JP3326701B2 - Image forming device - Google Patents

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 an electrophotographic printer.

[0002]

2. Description of the Related Art In a conventional developing apparatus, particularly in a developing device in which a uniform thin layer of developer is formed on a developer carrier and supplied to the latent image carrier, the developer close to the latent image carrier is used. A carrier, a developer replenishing member for replenishing developer to the developer carrier, and a layer thickness regulating means for contacting the developer carrier and thinning the developer on the developer carrier. Developing devices are known.

[0003] Many of such developing devices are known which use a one-component toner, that is, a developer which is composed of only toner and does not contain carrier particles. In order to obtain good printing in this developing device, it is important that the layer of the developer formed on the developer carrying member is a uniform thin layer and is uniformly charged.

For this purpose, conventionally, as shown in FIG.
A roller-shaped developer replenishing member (reset roller) 2 that comes into contact with the developer carrier 1 with a predetermined nip is opposed to form a uniform thin layer of toner. Reference numeral 3 denotes a layer thickness regulating member which is in pressure contact with the developer carrier 1 and frictionally charges the developer and charges and injects a charge by receiving a voltage.

[0005]

The developer replenishing member 2 comprises:
A rotating body formed by forming a conductive elastic body into a roll shape, and is in contact with the developer carrier 1 with a certain nip width. The developer carrier 1 and the developer replenishing member 2 are both rotating bodies and rotate at a peripheral speed ratio in the same direction indicated by an arrow in FIG. 5, so that a drive motor having a large torque is required. I was

SUMMARY OF THE INVENTION It is an object of the present invention to provide an image forming apparatus having a developing device capable of reducing a rotational torque without deteriorating image quality.

[0007]

In order to achieve the above object, according to the present invention, a developer carrier is pressed against a latent image carrier, and the developer conveyed by the developer carrier carries the latent image carrier. In an image forming apparatus using a developing device that develops and visualizes a latent image formed on a body, a lower surface of the developer carrier of the developing device is in contact with a device bottom plate, and the developer is Along the part of the outer circumference of the carrier
And a developer holding layer for collecting the developer remaining on the developer carrier after development and supplying the developer to the developer carrier (first configuration). And

[0008]

Further, a developer supply amount regulating member for preventing the supplied developer from directly going to the developer holding layer is added to the developing device of the image forming apparatus of the first configuration. ( Second configuration).

[0010]

Since the load applied to the conventional roller-shaped developer supply member is eliminated, the load of the rotational torque is reduced, and the drive motor can be reduced in size. Therefore, the size and cost of the device can be reduced.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

FIG. 4 is a side view schematically showing the structure of an electrophotographic apparatus (image forming apparatus) to which the present invention is applied.
1 is a latent image carrier such as a photosensitive drum, 12 is a charging means such as a scorotron, 13 is a latent image writing means such as a laser optical unit, 14 is a one-component developing device, 15 is a transfer means such as a corotron, and 16 is heat fixing. Fixing means 17 such as a container, and cleaning means 17 such as a blade cleaner. Recording by this electrophotographic apparatus is performed in the following procedure.

At the time of recording, the surface of the latent image carrier 11 rotating in the counterclockwise direction indicated by the arrow is uniformly charged by the charging means 12, and then the surface is charged in accordance with image information by the latent image writing means 13. Exposure is performed to form an electrostatic latent image. This electrostatic latent image is developed by the one-component developing device 14 to become a toner image.

On the other hand, the recording paper 100 stored in the paper storage portion is fed out at the above-described process and sent to the space between the latent image carrier 11 and the transfer means 15, where the recording paper 15 The transfer of the toner image to the sheet 100 is performed. After that, the recording paper 100 is
After fixing the toner image, the sheet is discharged to a stacker (not shown).

The residual toner remaining on the latent image carrier 11 after the transfer is removed by a cleaning unit 17, and the residual potential on the latent image carrier 11 is removed by a not-shown discharging unit. Details of the configuration and operation of the one-component developing device used in the electrophotographic apparatus having such a configuration and operation will be described below with reference to FIGS.

FIG. 1 is a side view of the one-component developing device 14. The one-component developing device 14 includes a developer carrier 21 which is a conductive member.
, A layer thickness regulating member 22, a developer holding layer 23, a developer hopper 24, and a developer supply amount regulating member 25.

The developer carrier 21 conveys and supplies the developer to the developing section by rotating about a rotation shaft 21a.
The rotating shaft 21a is connected to a power supply (not shown), and the developer carrier 21 is arranged between the developer carrier 21 and the latent image carrier 11 such that electric fields are generated in opposite directions in the image portion and the background portion of the latent image. Voltage. For example, when an organic photoreceptor is used for the latent image carrier 11, the image portion potential is about -100V and the background portion potential is about -600V.
1 is applied with a voltage of -300V.

As the material of the developer carrying member 21, urethane rubber, silicon rubber, NBR, porous urethane sponge or the like having conductivity can be used.

The layer thickness regulating member 22 is in pressure contact with the latent image carrier 11 to frictionally charge the developer. Further, the layer thickness regulating member 2
2, a voltage of -400 V is applied to increase the amount of charge by charge injection charging. The layer thickness regulating member 22 is formed of a leaf spring in which the tip of stainless steel (SUS304) is round-etched, and
It is attached so that the pressing pressure to 1 is 35 gf / cm.

The developer holding layer 23 collects the developer remaining on the developer carrier 21 after the development, and supplies the developer to the developer carrier 21 to supply the developer to the developer carrier 21. It has the function of making the layer thickness of the developer uniform. The developer holding layer 23 is a sheet formed of a conductive urethane sponge having a thickness of 10 mm, and a voltage is applied to the developer holding layer 23. The developer holding layer 23 has such a simple structure, and a roller-shaped developer replenishing member, which is conventionally required, can be eliminated, and the cost can be reduced.

Various conductive urethane sponges are conceivable. In this example, a cell having about 40 cells / inch and a volume resistivity of 10 ⁴ Ω · cm was used. The developer holding layer 23 having such a configuration is partially arranged on the apparatus bottom plate 26 below the developer carrier 21 so as to be along the outer diameter of the developer carrier 21, and the contact depth of the portion along the outer diameter is small. The length (compression amount) is 2 mm. The portion of the developer holding layer 23 not along the developer carrier 21 has an angle of about 30 ° with respect to the horizontal line.

The developer supply amount regulating member 25 is for preventing the developer dropped from the developer hopper 24 from directly falling on the developer holding layer 23. After stopping before the amount regulating member 25, the developer goes to the developer holding layer 23. The shape of the developer supply amount regulating member 25 is as shown in FIG.

The developer supply amount regulating member 25A shown in FIG.
Is a goodwill shape formed of a 20 μm mylar film, and the developer supply amount regulating member 25B in FIG. 2B is a brush shape formed of rayon fiber having a thickness of 6 denier / filament. Mylar films and rayon fibers of these materials are suitable for preventing excess developer from going to the developer holding layer 23 due to its elasticity.

Further, since these materials can control the resistance value, by controlling the resistance value, it is possible to prevent the developer from being improperly charged. Suitable resistance values are both about 10 ⁴ Ω · cm (when a voltage of 100 V is applied) (such that the charging series charges the toner negatively with respect to the toner).

The developer has a volume resistivity of 4 × 10 ¹⁴ Ω · c.
m, an average particle diameter of 10 μm, and a polyester toner having a silica external additive of 0.5%.

FIG. 3 shows the result of comparing the image obtained by using the one-component developing device 14 having the above-described structure with that of the conventional one. As shown in FIG. Further, the rotation torque could be reduced to 50% of the conventional value. Specifically, when a 5-phase stepping motor is used as a drive motor and the above-described polyester toner having a particle diameter of 10 μm and silica external addition of 0.5% is used as a developer, a static torque of 2 kgf · cm is reduced to 1 kgf · cm.
cm.

Note that, in addition to the above-described conductive elastic body, a brush fiber having conductivity may be used for the developer carrying member 21. As the brush fiber, for example, a fiber in which carbon is uniformly dispersed in rayon fiber and made into a band shape with a thickness of 15 mm, the resistance value is 10% per fiber.
Set to ³ Ω · cm. Even when this brush fiber was used, the same effects as described above were obtained as a result of image formation.

[0028]

As described above, according to the present invention, the rotational torque can be reduced, and the same image quality as that of the related art can be realized at low cost. In the present embodiment, an image forming apparatus using a one-component toner has been described.However, the present invention is an alternative to a reset roller, and may be applied to an image forming apparatus using a toner other than a one-component toner. The same effect can be obtained by using this means.

[Brief description of the drawings]

FIG. 1 is a side view of a one-component developing device according to an embodiment of the present invention.

2A and 2B are explanatory diagrams of a shape of a developer supply amount regulating member according to an embodiment of the present invention. FIG. 2A shows a developer using a Mylar film, and FIG. 2B shows a brush. .

FIG. 3 is an explanatory diagram of an effect of the present invention.

FIG. 4 is a side view showing a schematic structure of an electrophotographic apparatus to which the present invention is applied.

FIG. 5 is a side view showing an outline of a conventional one-component developing device.

[Explanation of symbols]

 REFERENCE SIGNS LIST 11 latent image carrier 14 one-component developing device 21 developer carrier 22 layer thickness regulating member 23 developer holding layer 24 developer hopper 25, 25A, 25B developer supply amount regulating member

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-56-123554 (JP, A) JP-A-4-324878 (JP, A) JP-A-3-145670 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) G03G 15/08

Claims (2)

(57) [Claims] A developer carrier (2) is provided on a latent image carrier (11).
1) The image forming apparatus using a developing device that presses the developer and conveys the latent image formed on the latent image carrier (11) with the developer conveyed by the developer carrier (21) to visualize the latent image. The developing device so that the back surface thereof is in contact with the device bottom plate (26) at a position below the developer carrier (21) of the developing device, and
The developer remaining on the developer carrier (21) after development is recovered along the part of the outer periphery of the developer carrier (21), and the developer is supplied to the developer carrier (21). An image forming apparatus comprising a developer holding layer (23). 2. The image forming apparatus according to claim 1, wherein
Make sure that the supplied developer goes directly to the developer holding layer (23).
A developer supply amount regulating member (25) for preventing
An image forming apparatus characterized in that: