JPH04174879A - Image forming device - Google Patents

Abstract

PURPOSE:To make it unnecessary to provide a mechanism to drive a copying roller and to prevent an unclearness of the image resulting from a slippage of cycle by forming larger diameter parts which consist of a low hardness and soft material, at both ends of a copying roller, and abutting them to the peripheral surface of an image holding body. CONSTITUTION:To both ends of the cylindrical main body 40 which consists of a conductive rubber, of a copying roller 4, low hardness and soft belt members are wound, and the belt members are formed in a larger diameter parts 41 larger than the diameter of the main body 40. And the roller 4 is pressure-welded and arranged to contact the peripheral surface of the main body 40 to the peripheral surface of an image holding body 1 by contracting the larger diameter parts 41. As a result, the friction force between the roller 4 and the holding body 1 is increased, and since the roller 4 is synchronized with and driven by the holding body 1, the rotating speeds of the holding body 1 and the roller 4 can be made coincident, and the generation of an unclear image resulting from a slippage of the synchronization can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an image forming apparatus such as an electrostatic copying machine or a laser beam printer.

<Prior Art> Recently, a drum-shaped image bearing member and a transfer roller to which a bias voltage is applied are equipped, and with the bias voltage applied to the transfer roller, the transfer roller transfers a transfer paper.
Image forming apparatuses have come into use in which a toner image formed on the surface of an image carrier is transferred to a transfer paper by pressure contact with the surface of the image carrier.

In the above configuration, there is a transfer charger that electrostatically attaches the transfer paper to the surface of the image carrier and transfers the toner image onto the surface of the transfer paper, and a separation charger that separates the transfer paper from the surface of the image carrier after transfer. Since it is unnecessary, there is no risk of generating harmful ozone, and since it is a close-contact transfer, there is an advantage that no blurring occurs in the image.

The above-mentioned transfer roller has large-diameter parts that are larger in diameter than the center part at both ends, and the large-diameter parts are brought into contact with the surface of the image carrier, and a gap for conveying the transfer paper is created between the two parts. There is something that has been formed. The large diameter portion is usually made of metal, such as JI
It is made of a relatively hard rubber material with a SA hardness of 30° or more.

<Problems to be Solved by the Invention> However, as described above, when the transfer roller is provided with a large diameter portion, the circumferential speed is different between the large diameter portion and the central portion.
There is a problem in that a slight deviation in the rotation period occurs and the formed image becomes unclear. For example, if the transfer roller is rotated so that the circumferential speed of the large diameter portion matches the circumferential speed of the image carrier, the circumferential speed of the center portion will be slightly slower, so that the transfer roller will not be transported between the transfer roller and the image carrier. The transport speed of the transfer paper or the circumferential speed of the image carrier may not match, resulting in transfer blurring and the image becoming unclear. On the other hand, if the transfer roller is rotated so that the circumferential speed of the center portion matches the circumferential speed of the image carrier, the circumferential speed of the large diameter portion will become slightly faster, causing slippage between the large diameter portion and the image carrier. As a result, there is a risk that the transfer paper conveyed between the transfer roller and the image carrier may be blurred, and the image may become unclear.

Furthermore, in conventional image forming apparatuses, as described above,
Since a mechanism for rotating the transfer roller in synchronization with the image carrier is required, there is also the problem that the structure of the apparatus becomes complicated.

The present invention has been made in view of the above circumstances, and
To provide an image forming device that can rotate a transfer roller in synchronization with an image carrier without requiring a complicated mechanism for driving the transfer roller and without causing slight deviations in the rotation period that make the formed image unclear. It is intended to.

Means for Solving the Problems> In order to solve the above problems, an image forming apparatus of the present invention has the following features:
At both ends of at least one of the image carrier and the transfer roller, a large diameter portion made of a flexible material having a larger diameter and lower hardness than the center portion is formed, and this large diameter portion is connected to the other periphery. It is characterized by being pressed against the surface.

Effect> In the image forming apparatus of the present invention having the above configuration,
Large diameter parts made of a flexible material with low hardness formed at both ends of at least one of the image carrier and the transfer roller are brought into pressure contact with the circumferential surface of the other, thereby increasing the frictional force between the two. Since the transfer roller is driven in synchronization with the image carrier, a mechanism for driving the transfer roller is not required. Further, the large diameter portion is compressed at the pressure welding portion, and
Since it is almost flush with the center part, the circumferential speeds of the large diameter part and the center part are the same in this part, and therefore the circumferential speed of the image carrier and the transfer roller, which rotate synchronously through the large diameter part, is the same. can almost be matched.

<Embodiment> An image forming apparatus of the present invention will be described below with reference to drawings showing an electrostatic copying machine as an embodiment.

As shown in FIG. 3, the electrostatic copying machine of this embodiment includes a charging roller 2 around a drum-shaped image carrier 1 for charging the image carrier 1, and a charging roller 2 indicated by a white arrow in the figure. As shown, an optical system (not shown) that exposes the surface of the image carrier 1, a developing device 3 that develops the electrostatic latent image formed on the surface of the image carrier 1 by exposure, and a developing device 3 that develops the electrostatic latent image formed on the surface of the image carrier 1 by the exposure. The image carrier 1 includes a transfer roller 4 that transfers the toner image formed on the image carrier 1 onto a transfer material P such as copy paper, and a cleaning device 5 that removes toner remaining on the image carrier 1.

Then, the charging roller 2 charges the surface of the image carrier 10 rotating at a constant speed.
After uniformly charging the electrostatic latent image and exposing it to light using an optical system to form an electrostatic latent image, the developing device 3 visualizes the electrostatic latent image as a toner image.
is transferred onto the conveyed transfer material P by the transfer roller 4, and the cleaning device 5 removes and cleans the toner remaining on the surface of the image carrier 1 after the transfer, thereby completing one cycle of image formation. finish. Further, the transfer material P peeled off from the image carrier 1 is guided to a fixing device (not shown) via a conveyance path 7, and after the toner image is fixed thereon, it is discharged from the device.

The charging roller 2 and transfer roller 4 are connected to a single power source 8.

As shown in FIG. 1, the transfer roller 4 has a cylindrical main body 40 made entirely of a conductive material such as conductive rubber, and a band made of a flexible rubber material with lower hardness is wound around both ends of the main body 40. By doing so, the large diameter portion 41. which is larger in diameter than the main body 40 is formed.
41 was formed. The hardness of the main body 40 and the large diameter portions 41 and 41 is not particularly limited, but for example, the hardness of the main body 40 and the large diameter portions 41 and 41 may be
If it is made of a rubber material with a hardness of 30", the large diameter part 4
1.41 may be made of a flexible rubber material with a JIS A hardness of about 10°.

The transfer roller 4 has a large diameter portion 41 as shown in FIG.
．． 41 is compressed and placed in pressure contact with the image carrier 1 so as to substantially contact the circumferential surface of the main body 40 or the circumferential surface of the image carrier 1 .

In the image forming apparatus of this embodiment, which is composed of the above-mentioned parts, the large diameter parts 41° 41 made of a flexible rubber material with low hardness formed at both ends of the transfer roller 4 are connected to the image carrier 1.
By bringing the transfer roller 4 into pressure contact with the peripheral surface of the image bearing member 1, the frictional force between the two is increased and the transfer roller 4 is driven in synchronization with the image carrier 1, thereby eliminating the need for a mechanism for driving the transfer roller.

Further, the large diameter portion 41 is compressed at the pressure welding portion and becomes almost flush with the circumferential surface of the main body 40, so the circumferential speeds of the large diameter portion 41.41 and the main body 40 do not match in this portion. , the image carrier 1 rotates synchronously via the large diameter portion 41.41.
The circumferential speeds of the transfer roller 4 and the transfer roller 4 can be made to almost match. Therefore, since there is no slight shift in the period between the two, there is no possibility that the formed image will become unclear.

Note that the configuration of the image forming apparatus of the present invention is not limited to that of the embodiment shown in the above figures.

For example, in the illustrated embodiment, the large diameter portions 41, 41 are formed by winding a band made of a flexible rubber material with low hardness around both ends of the main body 40 of the transfer roller 4. The entire portion of the roller corresponding to the large diameter portion may be formed of a flexible rubber material.

As the flexible material constituting the large diameter portion, in addition to the rubber material of the embodiment, synthetic resin or the like may also be used.

In the illustrated embodiment, the large diameter portions are formed at both ends of the transfer roller 4, but the large diameter portions may be provided on the image carrier.

The image carrier 1 may be of various shapes, such as a drum shape or a belt shape.

The configuration of the present invention can be applied not only to the electrostatic copying machine described above but also to other image forming apparatuses such as laser printers.

In addition, various design changes can be made without changing the gist of the present invention.

<Effects of the Invention> The image forming apparatus of the present invention is configured as described above, and has a large size made of a flexible material with low hardness formed at both ends of at least one of the image carrier and the transfer roller. By pressing the diameter part against the other circumferential surface, the frictional force between them is increased, and the transfer roller is synchronized with and follows the image carrier, eliminating the need for a mechanism to drive the transfer roller. . Further, the large diameter portion is compressed at the pressure contact portion and becomes substantially flush with the center portion, so that the circumferential speeds of the large diameter portion and the center portion match in this portion. Therefore, the circumferential speeds of the image carrier and the transfer roller, which rotate synchronously through the large diameter portion, can be made to closely match, and there is no possibility that the image will become unclear due to a slight shift in the period.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a transfer roller which is a main part of an electrostatic copying machine as an embodiment of the image forming apparatus of the present invention, and FIG. 2 shows a state in which the transfer roller is placed in pressure contact with an image carrier. The front view shown in FIG. 3 is a schematic diagram showing the internal structure of the electrostatic copying machine. 1... Image carrier, 4... Transfer roller, 41.41.
...Large diameter part.

Claims (1)

[Claims] 1. An image carrier on which a toner image is formed, and a conductive transfer roller to which a bias voltage is applied to transfer the toner image on the image carrier to transfer paper, and at least one of the above two. A large diameter part made of a flexible material having a larger diameter than the center part and lower in hardness than the center part is formed at both ends of one, and the large diameter part is pressed against the circumferential surface of the other. Image forming device.