JPH0422982A - Fixing device for image forming device - Google Patents

Abstract

PURPOSE:To improve the cleaning action of a fixing roller and to prevent the deterioration of image quality by disposing a means for attracting toner stuck to the surface of the roller to a cleaning web which rubs the surface of the roller on the back surface side of the cleaning web. CONSTITUTION:The web 6 stretched and extended between a supply roller 7 and a take-up roller 8 is allowed to abut on the fixing roller 1 by two pressing rollers 9a and 9b, and it rubs the surface of the roller 1 to perform the cleaning of the roller 1. In such a case, a corona discharger 10 is disposed on the back surface side of the web 6 between the rollers 9a and 9b, so that electric field which is generated by discharging acts to transfer the toner on the fixing roller 1 side to the web 6 by electrostatic attracting force. Thus, the cleaning performance is improved and the occurrence of an offset phenomenon is prevented, then a good-quality image is obtained.

Description

Detailed Description of the Invention (1) Purpose of the Invention (Field of Industrial Application) This invention relates to an image forming apparatus that uses an electrostatic transfer process, such as an electrostatic copying machine and a printer, and a fixing device thereof. It is related to.

(Prior Art and Issues to be Solved) In a well-known image forming apparatus that includes a step of further electrostatically transferring a toner image electrostatically formed on the surface of an image carrier to a transfer material such as paper, the transfer material It is necessary to firmly fix the toner image formed on the transfer material, and for this purpose, the transfer material carrying the toner image is passed through the contact nip of a pair of rollers that are in pressure contact with each other, and usually A device in which the toner image is fixed and fixed on the transfer material by heating a pair of rollers and applying heat and pressure to the transfer material carrying the toner image is widely used.

By the way, in the fixed @ device having such a configuration, a part of the toner adhering to the transfer material passing through the nip adheres to the roller side, which further contaminates the subsequent transfer material. Since the offset phenomenon occurs, it is necessary to constantly clean the rollers with a cleaner. Various cleaning methods have been proposed for this purpose, and among them, the web cleaning method is superior in terms of durability, cost, cleaning function, etc. It is known that there are

FIG. 3 shows a typical example of such a web cleaning device, and its structure and operation will be briefly described.

A pressure roller 2, which has an elastic layer such as silicone rubber formed on its surface, is in pressure contact with a heating fixing roller 1, which has a resin film with good female moldability formed on its surface and has a built-in suitable heat source such as a halogen heater. It is assumed that a transfer material P on which a toner image T is placed is supplied to a pressure nip between the two, and heat and pressure are applied thereto to fix and fix the toner image T on the transfer material P.

In the figure, reference numeral 3 is a temperature sensing element used to control the surface temperature of the roller l, and reference numeral 4 is a separation claw for separating the transfer material that has passed through the nip portion from the roller 1.

As mentioned above, in order to prevent some of the toner on the transfer material from adhering to the surface of the roller 1 when passing through the nip section, which would cause deterioration in the image quality of subsequent copies, the toner is removed as shown in the figure. , a web cleaning device 5 is provided.

The cleaning device 5 includes a supply roller 7 wound with a cleaning web, a take-up roller 8 that sequentially winds up the web, and a cleaning web 6 wound and stretched between both rollers. A portion existing between the rollers is in contact with the surface of the fixing roller 1 by a pressing roller 9 that is pressed against the fixing roller 1.

The web 6 is configured to clean the surface of the fixing roller 1 by driving the take-up roller 8 at low speed by an appropriate drive source (not shown) and rubbing the web 6 against the surface of the fixing roller 1.

As the web, it is preferable to use aromatic polyamide resin, polyester nonwoven fabric, etc., and it is common to impregnate this with a female molding agent such as silicone oil to improve the mold releasability of the surface of the fixing roller.

With this configuration, a certain roller cleaning effect can be expected under normal conditions, but when there is a large amount of toner on the transfer material, or when such a material is continuously copied, the toner that adheres to the web may also be affected. The amount of toner increases and cannot be cleaned completely, and after copying is completed, toner accumulation remains as shown schematically by the symbol T° in Fig. 4, and this toner is fused to the original several sheets of transfer material during the next copy. It is unavoidable that this may cause contamination.

In order to prevent such a situation from occurring, it is possible to increase the speed of the web, but this is not practical as it increases the amount of web consumption.

The present invention has been made in order to cope with such a situation, and is a web cleaning device of a fixing device that constantly reliably removes toner adhering to the fixing row without increasing the amount of web consumption. It is an object of the present invention to provide a linting device that can perform a good fixing action.

(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 a transfer material that carries an unfixed toner image in the pressure nip of a pair of rollers that are in pressure contact with each other. In the cleaning device of the fixing device, the toner image is fixed by passing through the fixing device, and a cleaning web is disposed on one of the rollers to rub the surface of the cleaning web. This cleaning web is characterized by being provided with means for adsorbing the attached toner to the cleaning web.

With this configuration, it is possible to improve the cleaning action of the fixing roller and effectively prevent deterioration of image quality.

(Description of Embodiment) FIG. 1 is a schematic side view of a fixing device showing an embodiment of the present invention, in which parts corresponding to the known device shown in the third section are given the same reference numerals. The explanation of these items will be omitted unless it is particularly necessary.

The part of the web stretched between the supply roller 7 and the take-up roller 8 is brought into contact with the fixing roller 1 by two pressure rollers 9a and 9b, and this part of the web is brought into contact with the fixing roller 1. Cleaning shall be performed by rubbing the surface.

In the illustrated apparatus, a corona discharger 10 is disposed on the back side of the web 6 between the rollers 9a and 9b, and a corona discharger 10 is connected to the toner by an unillustrated power supply. It is designed to generate a polar direct current corona discharge.

Due to the action of the electric field formed by such discharge, the toner of one example of the fixing roller can be transferred to the web 6 by electrostatic adsorption force, and as a result, even after continuous copying as described above, when the work is stopped, the toner can be transferred to the web 6. This effectively prevents a large amount of toner from accumulating near the contact end of the web and the fixing roller and deteriorating the quality of subsequent copies, thereby improving the cleaning effect.

In the above case, a direct current bias is applied to the corona discharger, but an alternating current corona discharge or a corona discharge in which an alternating current is superimposed on a direct current so as to have a polarity opposite to that of the toner may also be performed.

FIG. 2 is a side view showing another embodiment, and the basic configuration is the same as that shown in the first embodiment. In this device, between the rollers 9a and 9b, An electrode plate 11 is disposed on the fixing roller 1, and a voltage is applied to the electrode plate 11 so as to have a potential opposite to that of the toner, thereby attracting the toner on the fixing roller l.

With this configuration, both rollers 9a, 9b
Since the electrode plate is disposed in all the gaps between the fixing rollers and the electrode plate can be curved in accordance with the curvature of the fixing roller, the cleaning effect can be further improved.

(3) As described in detail, the present invention provides a fixing device that uses a pair of fixing rollers and is configured to supply a transfer material to a pressure nip between both rollers. In a cleaning device configured to rub a cleaning web against a fixing roller, the toner is electrostatically attracted to the web, which increases the efficiency of toner transfer to the web and improves the cleaning function. This has a remarkable effect on preventing the offset phenomenon and obtaining high-quality images.

[Brief explanation of the drawing]

FIG. 1 is a side view of a cleaning device for a fixing device showing an embodiment of the present invention, FIG. 2 is a side view of a cleaning device showing another embodiment, and FIG. 3 is a side view of a known cleaning device. FIG. 4 is an enlarged side view schematically showing the state of toner accumulation in the cleaning area same as above. DESCRIPTION OF SYMBOLS 1... Fixing roller, 2... Pressure roller, 3... Temperature sensing element, 4... Separation claw, 6... Web, 9.9a,
9b---Press roller, 10...Corona discharger, 11
...electrode plate.

Claims (3)

[Claims] (1) At the pressure nip of a pair of rollers that are in pressure contact with each other,
A cleaning device for a fixing device configured to allow a transfer material carrying an unfixed toner image to pass therethrough to fix the toner image, and wherein a cleaning web is disposed on one of the rollers to rub the surface thereof, the cleaning device comprising: A cleaning device comprising a means for adsorbing toner adhering to the roller surface to the cleaning web on the back side of the web. (2) The cleaning device according to claim 1, wherein the means for adsorbing the toner to the cleaning web is a corona discharger. (3) Claim 1, wherein the means for adsorbing the toner to the cleaning web is an electrode to which a bias voltage is applied.
Cleaning device as described in section.