JPH0229677A - Image forming device - Google Patents

Abstract

PURPOSE:To perform transfer stably for a long time with silent workability by supporting a conductive roller pressing on an image carrier by a bearing made of conductive resin. CONSTITUTION:A conductive transfer roller 3 is brought into press-contact with a cylindrical photosensitive body 1 which has an axial line in the direction perpendicular to the sheet surface and rotates in the direction of an arrow A. The bearing 7 is composed of conductive resin of 10 to 10<4>OMEGAcm volume resistance, carbon fiber filling resin of 2X10<2> volume resistance, for instance. A transfer bias caused by a power source 6 is impressed on a transfer roller 3 through a spring 5 and the bearing 7. Consequently, the transfer roller 2 is stably pressed for a long time, and a transfer bias is stably impressed thereto for a long time. Thus, the inexpensive device with less noisy and high durability can be obtained.

Description

Detailed Description of the Invention (1) Purpose of the Invention (Field of Industrial Application) This invention relates to image forming apparatuses that utilize an electrostatic recording process, such as electrostatic copying machines and printers, and in particular to image forming apparatuses that utilize electrostatic recording processes, such as electrostatic copying machines and printers. The present invention relates to an image forming apparatus that applies voltage to an image carrier.

(Prior art and problem to be solved B) In the image forming apparatus as described above, a transfer roller is usually pressed against a rotating cylindrical photoreceptor to form a transferable toner image on the surface of the photoreceptor. A sheet-like transfer material such as paper is passed through a pressure nip between the photoreceptor and the transfer roller, and at this time a transfer bias is applied to the transfer roller to transfer the toner image on the surface of the photoreceptor to the transfer material. Image forming devices have already been proposed.

Compared to well-known image forming apparatuses that use a transfer charger during transfer, such image forming apparatuses are less likely to cause transfer misalignment, require lower bias voltage, and have a simpler configuration and lower costs. Although it has various advantages such as contributing to down reduction, it also has disadvantages such as those described below.

This will be briefly explained with reference to FIGS. 3 and 4. Both of these diagrams schematically show the configuration near the transfer site of the image forming apparatus as described above, and corresponding parts have the same reference numerals. It is shown with .

A conductive transfer roller 11 equipped with a metal core 12 usually made of metal is in pressure contact with a cylindrical photoreceptor 10 extending perpendicular to the plane of the paper and rotating in the direction of the arrow shown in the figure. A transfer bias is applied from the power supply 16 via R.

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 as the photoreceptor rotates, the toner image arrives at the pressure nip with the transfer roller 11.

As shown on the right side of the figure, a transfer material (not shown) is supplied to the pressure nip between the photoreceptor 10 and the transfer roller 11 in synchronization with the toner image. After receiving the toner image, it is further conveyed to a fixing site (not shown).

In such an image forming apparatus, in the apparatus shown in FIG.
The spring 1 is guided by the spring 3 and is disposed within the frame.
4 is directly supported.

In the apparatus shown in FIG. 4, the core 12 of the transfer roller 11 is supported by a bearing 15 made of sintered metal and guided by a spring 14 in the frame 13.

Because of this structure, for example, in the former case, the core metal and the spring, both of which are metal, may come into direct contact and generate noise, or the durability may be poor and the transfer roller may not be able to properly press the photoconductor. It becomes difficult to maintain the transfer bias and apply the transfer bias.

In the latter case, the sintered metal contains oil, which over time becomes covered with toner and loses its function as a bearing, resulting in high costs and limited freedom of shape. In addition, in both cases, there is no large resistance other than the photoreceptor and transfer roller, so it prevents scratches on the photoreceptor surface from flowing large currents and destroying the power supply. Therefore, it is necessary to insert a resistor.

The present invention has been made in view of the above-mentioned current situation, and is intended to stably apply an appropriate pressing action and transfer bias to the transfer roller over a long period of time in an image forming apparatus equipped with a transfer roller. The purpose is to provide a device that can perform the following tasks.

(2) Structure of the invention (technical means for solving the problem and its operation) In order to achieve the above object, the present invention provides an image forming apparatus that includes an image bearing member and a conductive roller that is in pressure contact with the image bearing member. It is characterized in that the roller is supported by a bearing made of conductive resin.

With this configuration, it is possible to obtain a quiet, highly durable, and low-cost image forming apparatus equipped with a conductive roller.

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

A conductive transfer roller 2 is in pressure contact with a cylindrical photoreceptor l having an axis perpendicular to the plane of the paper and rotating in the direction of arrow A.

As shown in the figure, a bearing 7 is supported on a frame 4 attached to a proper position within the device so as to be able to move toward and away from the photoreceptor, as shown in the figure. This bearing 7
The core metal 3 of the transfer roller 2 is mounted on the transfer roller 2, and
The bearing 7 is biased toward the photoreceptor by the action of the spring 5, so that the transfer roller 2 is pressed against the photoreceptor 1 with an appropriate pressing force.

The bearing 7 is made of an appropriate conductive resin having a volume resistivity in the range of 10 to 106 Ωcm, such as carbon fiber-filled resin 2.
It is assumed that the transfer bias from the power source 6 is applied to the transfer roller 2 via the spring 5 and the bearing 7.

In addition, around the photoreceptor l, there is a primary charger that charges the surface uniformly, an image signal applying means such as a laser beam image-modulated to form an electrostatic latent image, and a device that visualizes the latent image. It goes without saying that members necessary for image formation, such as a developing device and a cleaner, are provided, but they are omitted.

When the toner image formed on the surface of the photoreceptor arrives at the nip between the photoreceptor and the transfer roller as it rotates, a transfer material (not shown) is supplied to the nip at the same timing. At the same time, the toner image on the photoreceptor side is transferred to the transfer material by the action of the transfer bias described above.

FIG. 2 shows another embodiment of the spring part,
This figure shows that the part that supports the bearing 7 when installed and the part that connects to the power source are integrally formed. By configuring in this way, it is possible to reduce costs without causing connection failures.

Although the present invention has been described above with respect to a case where it is applied to a transfer roller, the present invention is not limited thereto. It is easy to understand that the present invention can also be used in the developing sleeve and the like.

In addition to the coil spring shown in FIG. 1, a leaf spring as shown in FIG. 5 by reference numeral 17 can of course be used as a spring for supporting the bearing.

(3) As described in detail, the present invention allows an image forming apparatus using a conductive roller to perform stable transfer over a long period of time with quiet operation, contributing to cost reduction. It's also big.

[Brief explanation of the drawing]

FIG. 1 is a side view of the main parts 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 above-mentioned apparatus, and FIGS. 3 and 4 are side views showing the vicinity of a transfer site of a known image forming apparatus. 1... Photoreceptor, 2... Transfer roller, 4... Pot frame,
5. Spring, 7. Bearing. Figure 1 Figure 2 Figure 2 Funeral map Figure

Claims (2)

[Claims] (1) An image forming apparatus comprising an image bearing member and a conductive roller that is pressed against the image bearing member, in which the roller is supported by a bearing made of conductive resin. (2) Volume resistivity of conductive resin is 10~10^6Ωcm
An image forming apparatus according to claim 1.