JPH0252849A - Transfer material carrier for image forming device - Google Patents

Abstract

PURPOSE:To simplify a device and to lower a coat by making a distance between a pressing part and the pressing part of a pair of rolls in a fixing part smaller than a minimum length in the direction of travelling a transferring material which is used in an image forming device and effectively preventing the turbulence of an image and the contamination of respective parts in the device. CONSTITUTION:A distance L between a pressing part of an image carrier 1 and a transferring roller 2 for mechanically holding a transferring material and the pressing part of a pair of fixing rollers in a fixing device is made smaller than the length to a travel direction in a carrying path, of the minimum transferring material which is set in a picture forming device. In such a way, since no carrying operation is not applied to the transferring material of all the sizes used in this device throughout all the length to an advancing direction, an image is not disturbed but the image of good quality can be constantly obtained. Further, since the transferring material is advanced while any part thereof is constantly effectively held, a guide part which forms an intermediate carrying part simply exhibits an auxiliary function. This part, therefore, is integrated with the bottom cover part of the picture forming device, thereby, a constitution being simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Object of the Invention (Field of Industrial Application) The present invention relates to an image forming apparatus using an electrostatic recording process, such as an electrostatic copying machine and a printer thereof.

(Prior art and problems to be solved) A sheet-like transfer material such as a piece of paper is supplied and brought into contact with a transferable toner image formed on the surface of a moving image carrier, and at this location, the toner image is charged by the action of a transfer charger or the like. Image forming apparatuses configured to electrostatically transfer a toner image onto a transfer material, and then convey this transfer material to a fixing site to fix and fix the toner image on the transfer material are conventionally well known.

In an image forming apparatus having such a configuration, it is easy to understand that in order to obtain a good image, it is essential that the photoreceptor and the transfer material in contact with the photoreceptor travel in sufficient synchronization at the transfer site. This would be understandable.

However, in an image forming apparatus that uses a well-known transfer charger, when looking along the conveyance path of the transfer material, the means for firmly gripping and conveying the transfer material at a position near the transfer site is located on the upstream side. This is a pair of registration rollers, and the fixing device is usually equipped with a pair of rollers in pressure contact with each other on the downstream side, and is configured to allow the transfer material to pass through the pressure nip portion of both rollers. be. therefore,
When using a very small transfer material, even though the trailing edge of the transfer material passes through the registration rollers, its leading edge does not reach the fixing site and remains at the transfer site until reaching this. Since the transfer material is transported only by the electrostatic adsorption force that acts between the image carrier and the transfer material, there is a risk that the synchronized movement of the image carrier and the transfer material may be disrupted, resulting in deterioration of image quality. .

In addition, in this case, even if it passes through the transcription site in good condition,
Thereafter, since the leading edge of the transfer material is not gripped by the fixing roller, there is a problem in that the conveying action on the transfer material is lost and the transfer material stops, further causing a jam.

In order to avoid such defects, measures have been proposed and used, for example, as schematically illustrated in FIGS. 2 to 4.

All of these devices are equipped with a cylindrical image carrier 10 that rotates in the direction of arrow A, a transfer region is formed by a transfer charger 12 disposed opposite to the image carrier 10, and a transport path 1
1, the toner image is transferred to a transfer material (not shown) supplied to the transfer site in synchronization with the toner image on the surface of the image carrier by a pair of registration rollers 11a, and after transfer,
This transfer material is separated from the image carrier and transported to a fixing site.

In such an image forming apparatus, in the installation shown in FIG. 2, the conveying means on the downstream side of the transfer site is formed on the conveying belt 13, and the above-mentioned small-sized transfer material is transferred to the fixing device by the conveying action of this belt. It is configured to be transported up to

In the image forming apparatus shown in FIG. 3, the conveyance roller 16 is disposed on a fixed transfer material conveyance path, and by appropriately determining the position of the conveyance roller 16, even the smallest transfer material planned to be used can be used. Both ends of Regis) O-la,
It is constructed so that it does not come loose from the fixing roller and the roller 16.

Furthermore, in the case of the fixing device of the so-called pressure fixing method, the axes of the pair of fixing rollers intersect in order to keep the pressure constant over the entire length of the pair of fixing rollers. In this structure, a pair of suppression rollers 17 are provided at appropriate positions on the conveyor belt in order to prevent the transfer material being held between the transfer material and the transfer material from moving in an irregular direction.

As outlined above, various methods have been used to prevent the transfer material being fed to the fixing site after transfer from stopping halfway, resulting in the inability to obtain copies or occurrence of jams. proposals have been made.

However, in any case, in the above-described image forming and mounting, means for mechanically firmly holding the transfer material is provided at or near the transfer site where the most precise synchronized movement must be achieved. Therefore, with the above-mentioned means, for example, processing of the trailing edge of the transfer material that has passed through the registration rollers, and processing of the trailing edge of the transfer material that has passed through the registration rollers, and processing of the subsequent transfer due to the toner that adheres to the rollers in the conveyance path, cannot be performed. Problems such as contamination of the material and curled transfer material causing jams due to the presence of rollers cannot be sufficiently solved, and furthermore, if a cleaning mechanism is provided to solve these situations, it will result in a lot of waste. Furthermore, the equipment was complicated, and satisfactory results could not be obtained.

The present invention has been made in view of the above-mentioned current situation, and it is an object of the present invention to provide an image forming apparatus that does not cause the above-mentioned situation and can always obtain high-quality images with an extremely simple configuration. This is the purpose.

(2) Structure of the invention (technical means for solving the problem and their effects) In order to achieve the above object, the present invention includes a rotating cylindrical image bearing member and a transfer roller that comes into pressure contact with the image bearing member. In an image forming apparatus, the image forming apparatus has a fixing section that transports and supplies a transfer material to the pressure contact section and includes a pair of rollers that are in pressure contact with each other on the downstream side of the pressure contact section when viewed in the traveling direction of the transfer material. The distance between the fixing portion and the pressure contact portion of the pair of rollers is set to be smaller than the length of the smallest transfer material used in the image forming apparatus as viewed in the running direction.

With this configuration, it is possible to reliably hold the transfer material until it reaches the fixing site after transfer, so it is possible to reliably prevent image distortion and contamination of various parts within the device, and it is also possible to This makes it possible to simplify and reduce costs.

(Description of Embodiments) FIG. 1 is a side view of the main parts of an image forming apparatus showing an embodiment of the present invention, mainly showing the parts along the conveyance path of the transfer material. A transfer roller 2 is disposed in pressure contact with a cylindrical image carrier l rotating in the direction of arrow A.

A transfer material (not shown) that is timed with the toner image on the surface of the image carrier 1 is transferred to the conveyance path 3 by the registration rollers 3a.
The toner image on the image carrier side is transferred to the transfer material by being guided by the toner toner to reach the pressure nip between the image carrier 1 and the transfer roller 2, and then passing through this.

Next, the transfer material carrying this toner image passes through the conveyance path 4 and reaches the fixing device 5, where it is held between a pair of rollers and subjected to pressure, or heat and pressure, to fix and fix the toner image on the transfer material. After that, it shall be ejected from the aircraft.

In such an image forming apparatus, in the present invention,
The distance between the pressure contact portion of the image carrier 1 and the transfer roller 2, which mechanically sandwich the transfer material, and the pressure contact portion of the pair of fixing rollers in the fixing device is set in the image forming apparatus. The length of the smallest transfer material is smaller than the length of the smallest transfer material as seen in the running direction on the conveyance path.

With this configuration, for all the sizes of transfer materials used in this device, there is no possibility that the transfer material will not be subjected to any conveying action over its entire length in the direction of travel. Therefore, the image is not disturbed by the main image as described above, and a high-quality image can always be obtained.

Furthermore, since the transfer material advances while any part of it is held securely, the guide part designated by the reference numeral 4 in the above embodiment, which forms the intermediate conveyance part, merely serves an auxiliary function. By integrating this part with a part of the bottom cover of the exterior of the image forming apparatus, the configuration can be simplified.
Since additional mechanisms such as belts and rollers with drive mechanisms are not required, costs can be significantly reduced.

(3) As described in detail, according to the present invention, the image carrier is provided with a transfer roller that is in pressure contact with the image carrier, and the transfer material after transfer is conveyed to the fixing section δ that is provided with a pair of rollers that are in pressure contact with the image carrier. In an image forming apparatus configured to do this, it is possible to maintain the transfer material in a stable state at all times and reliably grip and transport it while the transfer material is being conveyed. Since a normal image can be reliably transported to a fixing site without being disturbed during transport, it greatly contributes to obtaining a good image.

[Brief explanation of the drawing]

FIG. 1 is a side view showing main parts of an image forming apparatus to which the present invention is applied, and FIGS. 2 to 4 are schematic side views showing a known image forming apparatus, particularly a portion of a transfer material conveying device. be.斯l...image bearing member, 2...transfer roller, 3...conveyance path, deception...fixing device.

Claims (1)

[Scope of Claims] A rotating cylindrical image bearing member and a transfer roller in pressure contact with the image carrier are provided, a transfer material is conveyed and supplied to the pressure contact portion, and a transfer roller is provided downstream of the pressure contact portion when viewed in the traveling direction of the transfer material. In an image forming apparatus having a fixing section including a pair of rollers that are in pressure contact with each other on the sides, the distance between the pressure contact section and the pressure contact section of the pair of rollers in the fixing section is set to the minimum transfer material used in the image forming apparatus. A transfer material conveying device of an image forming apparatus that is formed to be smaller in length as viewed in the running direction of the image forming apparatus.