JP2640756B2 - Voltage applying device and image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Industrial Application Field) The present invention relates to an image forming apparatus using an electrostatic recording process such as an electrostatic copying machine and a printer, and in particular, using an electroconductive roller. The present invention relates to a voltage application device that applies a voltage to an image carrier.

(Prior Art and Problems to be Solved) In the image forming apparatus as described above, a transfer roller is pressed against a photoreceptor usually formed in a rotating cylindrical shape to form a transferable toner image on the photoreceptor surface, and a photoreceptor is formed. And a sheet-like transfer material such as paper is passed through the pressure contact nip portion of the transfer roller, and at this time, a transfer bias is
An image forming apparatus having a configuration for transferring a toner image on a photosensitive member surface to a transfer material has already been proposed.

Such an image forming apparatus is less likely to cause transfer deviation, requires a lower bias voltage, has a simpler configuration, and is more cost-effective than a known image forming apparatus that uses a transfer charger for transfer. Although it has various advantages, such as contributing to down, it has the following disadvantages, for example.

This will be briefly described with reference to FIGS. 3 and 4.
Each of these shows the outline of the configuration near the transfer site of the image forming apparatus as described above, and the corresponding portions are denoted by the same reference numerals.

A conductive transfer roller 11 having a metal core 12 is pressed against a cylindrical photoreceptor 10 extending in a direction perpendicular to the paper surface and rotating in a direction indicated by an arrow in FIG. , A transfer bias is applied from a power supply 16.

It is assumed that a toner image is electrostatically formed on the surface of the photoreceptor 10 by an image forming member (not shown), and the toner image arrives at a nip portion in press contact with the transfer roller 11 as the photoreceptor rotates.

From the right side of the drawing, a transfer material (not shown) supplied to the press-contact nip portion between the photoconductor 10 and the transfer roller 11 at the same timing as the toner image is applied to the photoconductor by the action of a transfer bias in the nip portion. After receiving the toner image, the toner image is further transported to reach a fixing portion (not shown).

In such an image forming apparatus, in the apparatus shown in FIG. 3, the transfer roller 11 has its core 12 guided by a frame 13 and directly supported by a spring 14 disposed in the frame. Have been.

In addition, in the device shown in FIGS.
Transfer roller 11 on sintered metal bearing 15 guided by 14
Core metal 12 is pivotally supported.

With such a configuration, for example, in the former case, both the metal core and the spring come into direct contact with each other to generate noise, or the pressing force of the transfer roller against the photosensitive member due to poor durability is reduced. , And application of a transfer bias becomes difficult. In the case of the latter, since the sintered metal contains oil, the metal is impregnated with the toner for a long time and impairs the function as a bearing. Inevitable. In addition, in each case, since there is no large resistance other than the photoconductor and the transfer roller, the resistance must be reduced to prevent the photoconductor surface from being damaged and a large current from flowing and destroying the current. It is necessary to intervene.

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and in an image forming apparatus including a transfer roller, to stably apply an appropriate pressing action and transfer bias application to the transfer roller for a long time. It is an object of the present invention to provide a device capable of performing the following.

(2) Configuration of the Invention (Technical Means for Solving the Problems, Action of the Invention) In order to achieve the above object, the present invention relates to a conductive roller that is in pressure contact with an image carrier that carries an image, and a metal rotating shaft. A voltage applying device for applying a voltage to a conductive roller having a coating layer formed around the rotation axis, and supporting the rotation axis at a position not overlapping with the coating layer in the axial direction of the rotation axis. And a biasing member for biasing the bearing toward the image carrier to press the conductive roller against the image carrier. The biasing member and the bearing A voltage application device (1), which comprises means for applying a voltage to the conductive roller through the device, or the device (1), wherein the device applies the bearing to the image carrier. Guides you in or out A voltage applying device (2), or an image forming means for forming an image on a recording material, comprising: an image carrier for carrying an image; and a conductive member for pressing against the image carrier. An image forming unit, comprising: a conductive roller having a metal rotating shaft and a conductive layer having a coating layer formed around the rotating shaft, wherein the coating is performed in the axial direction of the rotating shaft. A conductive resin bearing that is provided at a position that does not overlap the layer and supports the rotating shaft; and urges the bearing toward the image carrier to press the conductive roller against the image carrier. An image forming apparatus comprising: an urging member; and means for applying a voltage to the conductive roller via the urging member and the bearing.
Alternatively, in the above (3), the image forming apparatus (4), wherein the apparatus includes a guide unit that guides the bearing in a direction toward or away from the image carrier.
Alternatively, in the above (3) or (4), the conductive roller charges the image carrier, or the image forming apparatus (5), or (3) or (4). Wherein the conductive roller transfers an image from the image carrier to a transfer material conveyed between the conductive roller and the image carrier. It is.

With this configuration, a quiet, highly durable, low-cost apparatus can be obtained in a voltage applying apparatus and an image forming apparatus having a conductive roller.

(Explanation of Embodiment) FIG. 1 is a side view of a main part of an embodiment of the image forming apparatus according to the present invention, particularly showing a configuration near a transfer portion.

A conductive transfer roller having a core 3 and a coating layer formed so as to cover the periphery of a photosensitive body 1 as a cylindrical image carrier that has an axis perpendicular to the paper surface and rotates in the direction of arrow A. 2 is pressed.

As shown in the figure, the transfer roller is pressed against the photosensitive drum by a bearing 7 guided by a frame 4 attached to a proper position in the apparatus. The core metal 3 of the transfer roller 2 is mounted on the bearing 7, and the bearing 7 is urged in the direction of the photoreceptor by the action of the spring 5 acting as an urging member. The photosensitive member 1 is pressed against the photosensitive member 1 with an appropriate pressing force. As shown in FIG. 1, the bearing 7 is arranged at a position where it does not overlap with the coating layer in the axial direction of the cored bar 3.

The bearing 7 is suitable conductive resin having a volume resistivity in the range of 10 to 10 ⁶ [Omega] cm - e.g., carbon fiber filled resin 2 × 10
^The transfer bias from the power source 6 is applied to the transfer roller 2 via the spring 5 and the bearing 7.

Further, even if the bearing is shaved by sliding between the bearing made of a conductive resin and the core, contact between the bearing and the core is maintained by pressing the bearing with the spring, and sufficient conduction is obtained.

Around the photosensitive member 1, a primary charger for uniformly charging the surface, an image signal applying means such as a laser beam image-modulated to form an electrostatic latent image, and a method for visualizing the latent image. Needless to say, members required for image formation, such as a developing unit and a cleaner, are provided, but they are omitted.

When the toner image formed on the surface of the photoconductor arrives at the nip portion where the photoconductor is rotated and pressed against the transfer roller, a transfer material (not shown) is supplied to the nip portion at the same timing. At the same time, the toner image on the photosensitive member is transferred to the transfer material by the action of the transfer bias.

FIG. 2 shows another embodiment of a spring portion, in which a portion for supporting the bearing 7 and a portion for connecting to a power source are integrally formed at the time of mounting. With this configuration, it is possible to reduce the cost without a poor connection.

The case where the present invention is applied to the transfer roller has been described above. However, the present invention is not limited to this, and the present invention is applied to a charging roller or a developing device used as a means for uniformly charging a photosensitive member. It can be easily understood that the developing sleeve and the like that are provided can be similarly used.

Further, as a spring for supporting the bearing, it is a matter of course that a leaf spring can be used as shown by reference numeral 17 in FIG.

(3) Effect of the Invention As described above, according to the present invention, in the image forming apparatus using the conductive roller, the covering layer portion, which is the roller body of the roller, does not overlap with the bearing portion supporting the shaft. , The outer diameter of the coating layer can be reduced by the thickness of the bearing.
It is also effective for cost reduction.

Furthermore, the cost is reduced, and even if the bearing made of a conductive resin slides with the core, the bearing is pressed by the pressing member, so that the contact between the bearing and the core is maintained at all times. And sufficient continuity can be obtained.

[Brief description of the drawings]

FIG. 1 is a side view of a main part of a copying machine showing an embodiment of the present invention, FIG. 2 is a side view showing another embodiment of a spring used in the apparatus, and FIGS. 3 and 4 are all publicly known. FIG. 5 is a side view showing the vicinity of a transfer portion of the image forming apparatus of FIG. 5. FIG. 5 is a side view showing still another embodiment. 1 photoconductor, 2 transfer roller, 4 frame, 5
Spring, 7 ... Bearing.

Claims (6)

(57) [Claims] A voltage for applying a voltage to a conductive roller which is in pressure contact with an image bearing member for carrying an image, the conductive roller having a metal rotating shaft and a coating layer formed around the rotating shaft. In the application device, a bearing of a conductive resin that is provided at a position that does not overlap with the coating layer when viewed in the axial direction of the rotation shaft and supports the rotation shaft,
An urging member for urging the bearing toward the image carrier in order to press the conductive roller against the image carrier, and to the conductive roller via the urging member and the bearing. A voltage application device comprising: means for applying a voltage. 2. The voltage applying device according to claim 1, wherein said device has a guide means for guiding said bearing in a direction toward or away from said image carrier. 3. An image forming means for forming an image on a recording material, comprising: an image carrier for carrying an image; and a conductive roller for pressing against the image carrier, wherein the rotating shaft comprises a metal and An image forming apparatus having an image forming means, comprising: a conductive roller having a coating layer formed around an axis; wherein the rotation axis is provided at a position not overlapping with the coating layer in an axial direction of the rotation axis. A bearing of a conductive resin supporting the bearing, a biasing member for biasing the bearing toward the image carrier to press the conductive roller against the image carrier, and the biasing member and the bearing. Means for applying a voltage to the conductive roller through the image forming apparatus. 4. The image forming apparatus according to claim 3, wherein said apparatus has guide means for guiding said bearing in a direction toward or away from said image carrier. 5. The image forming apparatus according to claim 3, wherein the conductive roller charges the image carrier.
The image forming apparatus according to any one of the above. 6. The image forming apparatus according to claim 1, wherein said conductive roller is
The image forming apparatus according to claim 3, wherein an image is transferred to a transfer material conveyed between the conductive roller and the image carrier.