JPH08194403A - Fixing device of image forming device - Google Patents

Abstract

PURPOSE: To eliminate a condition in which releasing agent is collected at a tip of a separated claw and stains are created on a transfer material by the agent by providing a means which blows air on the tip of the separated claw. CONSTITUTION: A nozzle 7 which jets air is arranged at a proper position where the running of a transfer material to be conveyed is not interrupted above a separated claw 4. Consequently, it blows off releasing agent which is collected at a part where the separated claw 4 comes into contact with a pressurizing roller 3 so that the transfer material is not stained by the collected releasing agent. Since the blown off releasing agent flows downwardly along a surface of the pressurizing roller 3 from a side of the separated claw 4, a cleaner such as sponge, felt, etc., may be provided at a proper place as required to remove the agent. The blowing off of air on a tip of the separated claw 4 may be performed at all times, but it is preferable to blow air intermittently by setting a timing. Preferably, the quantity of air is set to approximately 0.005 to 0.03m<2> /sec per cm<2> .

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as an electrostatic copying machine and a printer, and more particularly to a fixing apparatus therefor. In the above-mentioned known image forming apparatus, it is necessary to fix and fix a toner image electrostatically formed on a transfer material such as paper to the transfer material. Various fixing means for this purpose have been proposed in the past. Recently, however, a fixing roller controlled to have a predetermined surface temperature and a pressure roller in pressure contact with the fixing roller are provided. It is well known that the one in which a toner image is melted and fixed on the transfer material by passing through the transfer material carrying the unfixed toner image is widely known. FIG. 5 is a schematic side view showing a typical example of such a fixing device. To briefly describe this, the fixing roller 2 whose surface is maintained at a predetermined temperature by a heat source (not shown). The pressure roller 3 is pressed against the nip portion N.
Is formed. When a transfer material (not shown) carrying a toner image electrostatically formed at an image forming portion (not shown) passes through the nip portion N via the conveying path 6, the toner image on the transfer material is formed. After being melted and firmly adhered to the transfer material, the transfer material is discharged to the outside of the machine through the paper discharge roller 5. A release agent applying device 1 for applying a release agent such as silicone oil to the surface of the fixing roller is provided in the vicinity of the fixing roller 2, whereby the release agent is applied to the surface of the fixing roller. A thin layer is formed to prevent the offset phenomenon. Further, as shown by reference numeral 4, a separating claw is brought into contact with the pressure roller 3 to prevent the transfer material from being wound around the roller after the fixing is completed. FIG. 6 is an enlarged side view showing that the separation claw 4 is in contact with the surface of the pressure roller 3, and the vicinity of the upper edge of the surface of the separation claw 4 facing the pressure roller 3 is shown. The transfer material that comes into contact with the pressure roller 3 and is discharged from the nip portion N is peeled off from the pressure roller 3. Such a separating claw is usually 2 to 5 in the axial direction of the pressure roller.
It is provided individually. The release agent is 20 for A4 size transfer material.
About 80 mg is applied to the fixing roller, and even if it is normally absorbed by the transfer material, if the separation claw 4 is constantly in contact with the pressure roller 3, the release agent applied to the fixing roller 2 is added. It is unavoidable to transfer to the pressure roller 3. The mold release agent transferred to the pressure roller 3 gradually accumulates at the tip of the separation claw 4 where it abuts the pressure roller 3, as shown in FIG. When the transfer material which has been fixed is separated in such a state, there is a problem that the release agent in the pool of the release agent is absorbed to cause stains on the transfer material and impair the image quality. In order to avoid such a problem, for example,
The timing of applying the release agent is limited to only when the transfer material is conveyed, or the shape of the separation claw 4 is set such that the surface 4a facing the pressure roller 3 is contacted with the roller as shown in FIG. It has been proposed to form the release agent so that it is formed so as to have a narrower width in an upper portion in contact with the tip portion so that the release agent is less likely to be accumulated in the tip portion. On the other hand, in the former means,
When forming a large number of images, it is impossible to prevent the release agent pool from being gradually formed by increasing the supply amount of the release agent. In the latter means, the surface tension of the release agent tends to collect at the tip of the separating claw, so that it is unavoidable to store a fixed amount of the release agent. is there. The present invention has been made in view of the above circumstances, and in the fixing device having the above-mentioned structure,
To provide a fixing device capable of suitably preventing deterioration of image quality due to a release agent by positively removing the release agent accumulated at the tip portion of a separation claw disposed in contact with a pressure roller. The purpose is. SUMMARY OF THE INVENTION To achieve the above object, the present invention comprises a heat fixing roller and a pressure roller which is in pressure contact with the heat fixing roller. A transfer material carrying an unfixed toner image is passed through the pressure nip portion to fix the toner image, and a means for applying a release agent to the roller to protect the surface layer of the roller and prevent the offset phenomenon, and the transfer In a fixing device of an image forming apparatus having a separating claw having a tip that abuts against the roller to prevent the material from being wound around the roller, a fixing device (1) having means for blowing air to the tip of the separating claw, or In the above (1), the fixing device (2) in which the air blowing means is outside the transfer material conveying path, or in the above (1) or (2), the air blowing is carried. The fixing device according to the transfer material to be is performed before reaches the separation pawl (3), or the above (1) to the one of any of the (3), 1 cm ² per 0.00 weight blowing air
A fixing device (4) of 5 to 0.03 m ³ / sec, or
A heat fixing roller and a pressure roller in pressure contact with this roller are provided, and a transfer material carrying an unfixed toner image is passed through the pressure contact nip portion of these rollers to fix the toner image and protect the surface layer of the roller. The roller includes means for applying a release agent to the roller to prevent the offset phenomenon, a separation claw having a tip end that abuts the roller to prevent the transfer material from winding around the roller, and means for cooling the fixing roller. In the fixing device of the image forming apparatus, the fixing device is provided with a unit that guides at least a part of the cooling airflow that cools the fixing roller to the tip of the separation claw. With this configuration, it is possible to preferably eliminate the situation where the release agent is stored at the tip of the separation claw and this causes stains on the transfer material. DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a side view of a fixing device showing an embodiment of the present invention. The basic structure of the fixing device is the same as that shown in FIG. The corresponding parts are designated by the same reference numerals. In such an apparatus, in the illustrated case, a nozzle 7 for ejecting air is provided above the separation claw 4 at an appropriate portion which does not hinder the traveling of the transfer material being conveyed. As a result, as described above, the release agent accumulated in the portion of the separation claw 4 that abuts the pressure roller is blown off so that the transfer agent is not contaminated by the retained release agent. The blown-off release agent flows downward from the side of the separating claw 4 along the surface of the roller 3, so that a cleaner such as sponge or felt may be placed in an appropriate place to remove it. In the above apparatus, the air may be blown to the tip of the separation claw 4 at all times, but this causes a loss of driving force, and therefore intermittently as shown in the timing chart of FIG. It is suitable to carry out. As shown in the figures, the timing is set so that air is blown for a time t ₁ seconds from the time t ₂ seconds before the transfer material reaches the position of the separating claw 4. Appropriate values for blowing air are that the release agent can be sufficiently removed by blowing, that the surface temperature of the fixing roller is not cooled too much, and that the surface temperature can be recovered rapidly and sufficiently even when cooled. It is necessary to set to. Specifically, the spraying time is set by t ₁
= 0.2 to 0.5 seconds, t ₂ = 0.7 to ₂ seconds, and it is preferable to set the air volume to about 0.005 to 0.03 m ³ / sec per 1 cm ^2. Confirmed by. FIG. 3 shows a fixing device according to another embodiment of the present invention.
FIG. 6 is a plan view showing a state where a separation claw 4 is in contact with a pressure roller 3. In this device, an air blowing nozzle 7 is arranged laterally to the tip of the separating claw 4. Of course, the nozzle 7 is arranged below the transport path so as not to interfere with the transport of the transfer material. With this structure, the nozzle can be arranged closer to the tip of the separating claw than in the case of the apparatus of the above-mentioned embodiment, so that the amount of blown air can be reduced and the air flow generation source can be made smaller. It becomes possible. Further, since the nozzle does not blow air directly to the fixing roller 2, the degree of temperature decrease of the roller is small,
The complicated sequence shown in FIG. 2 eliminates the need to avoid the change in the surface temperature of the fixing roller. FIG. 4 is a schematic side view of a fixing device showing still another embodiment. This device also has basically the same configuration as each of the above-mentioned embodiments, and the description thereof will be given. Omit it. In this apparatus, an exhaust fan 11 is provided in the vicinity of the fixing roller 2, and the heated air near the fixing roller 2 is discharged to the outside of the machine through the fan 11, the duct 13 and the air filter 12. It is supposed to be done. A pipe 7a extends from the proper place of the duct 13 where the exhaust flow exists to the outside of the duct, and its tip nozzle 7 is arranged near the tip of the separation claw 4. Therefore, it is possible to prevent a part of the air flow generated by the fan 11 from being sprayed from the nozzle 7 to the tip portion of the separation claw 4 through the duct 13 and the pipe 7a and the release agent being accumulated in the portion. . With such a structure, a special drive source is not required for injecting air from the tip of the separation claw, which contributes to downsizing of the apparatus. As described above, according to the present invention,
It has a heat fixing roller and a pressure roller that presses against it.
In a fixing device for fixing a toner image by allowing a transfer material carrying an unfixed toner image to pass through the pressure contact nip portion of both rollers, the transfer material is conveyed to a separation claw tip portion arranged in contact with the pressure roller. Since air is blown in a state where the release agent is not affected to prevent the release agent from accumulating at the tip portion, it is possible that the accumulation of the release agent adheres to the transfer material and impairs the image quality. This is effective in obtaining a good quality image that can be preferably avoided. By limiting the timing of blowing air to the separation claws immediately before the transfer material reaches the separation claws, the temperature drop of the fixing roller is prevented as much as possible, and the fixing work is stabilized. I can carry it out. Further, the air blowing amount is set to 0 per 1 cm ² .
By setting the rate to 005 to 0.03 m ³ / sec, the release agent at the tip of the separating claw can be efficiently and reliably blown off. Furthermore, a part of the air flow of the heat exhausting means for cooling the fixing roller is guided to the tip of the separation claw to blow off the release agent, so that a drive source for air flow generation is separately provided. This contributes to downsizing of the device and space saving. With the above-mentioned structure, good fixing can be always carried out, so that it is possible to obtain a high quality image with a simple and compact structure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic side view of a fixing device showing an embodiment of the present invention. FIG. 2 is a view showing an air blowing tie-conk of the same. FIG. 3 is a fixing device showing another embodiment. FIG. 4 is a schematic side view of a fixing device showing still another embodiment. FIG. 5 is a side view showing the configuration and operation of a known fixing device. FIG. 6 A release agent is stored at the tip of the separation claw. FIG. 7 is a perspective view showing a tip shape of an example of a known separation claw [Explanation of reference numerals] 1 Release agent applying device 2 Fixing roller 3 Pressure roller 4 Separation claw 7 Nozzle 11 Exhaust fan 13 duct

Claims (1)

Claim: What is claimed is: 1. A heating and fixing roller, and a pressure roller that is in pressure contact with the heating and fixing roller. A transfer material carrying an unfixed toner image is passed through a pressure contact nip portion of these rollers to form a toner image. A means for applying a release agent to the roller in order to fix and protect the surface layer of the roller to prevent the offset phenomenon.
What is claimed is: 1. A fixing device for an image forming apparatus, comprising: a separation claw having a tip that abuts against the roller to prevent the transfer material from being wound around the roller. The fixing device comprises a unit that blows air to the tip of the separation claw. 2. The fixing device according to claim 1, wherein the air blowing unit is provided outside the transfer material conveying path. 3. The fixing device according to claim 1, wherein the transfer material to which air is blown is carried out before the transfer material reaches the separation claw. 4. The amount of air blown is 0.00 per 1 cm ^2.
The fixing device according to any one of claims 1 to 3, which has a rate of ^{5 to} 0.03 m ³ / sec. 5. A heat-fixing roller and a pressure roller which is in pressure contact with the heat-fixing roller, wherein a transfer material carrying an unfixed toner image is passed through a pressure-contact nip portion of these rollers to fix the toner image, and A means for applying a release agent to the roller to protect the surface layer and prevent the offset phenomenon;
In a fixing device of an image forming apparatus, which comprises a separation claw having a tip for abutting against the roller to prevent the transfer material from winding around the roller, and a fixing device of an image forming apparatus, a cooling air flow for cooling the fixing roller is provided. A fixing device comprising means for guiding at least a part of the separation claw to the tip.