JPH08272245A - Fixing device and image forming device - Google Patents

Abstract

PURPOSE: To obtain an inexpensive fixing device which is free of toner image disturbance despite high fixing-speed by prodding en electrode which touches a recording material partly but not its entire area in its longitudinal direction, and applying a bias by a bias application means. CONSTITUTION: An electrode 26 is provided in part of the front end of an entrance guide plate 8, and a bias is applied to it by the bias application means E. Also, an aluminum material is provided at the front end of the entrance guide plate 8, and a conductive brush is provided on it. In this device, paper insertion in the middle is standard, therefore the electrode 26 is disposed almost in the middle of the entrance guide plate 8. The electrode disposed partly but not entirely in the longitudinal direction in all the sizes of the recording materials prevents image disturbance. Further, at this time, the device prevents an applied current from flowing into a pressure roller 10 due to the insertion of a high voltage resistant diode 19, thereby causing the applied bias current to securely flow into an GND (grounding part) via a fixing roller 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a printer or a facsimile using an electrophotographic system,
In particular, the present invention relates to an apparatus provided with a means for applying a bias voltage to a transport system around the fixing device.

[0002]

2. Description of the Related Art A conventional image forming apparatus will be described with reference to the drawings. FIG. 10 is a side view of a conventional image forming apparatus. In the figure, the photosensitive drum 1 as an image carrier uniformly charged by the charging means such as the charger 2 forms a latent image by the exposure means 3, and the latent image is developed by the rotation in the arrow direction in the figure. It is conveyed to a portion facing the device 4. Then, after being visualized as a toner image by the developing device 4, it is transferred by a transfer means such as a transfer roller 6 onto the recording material P nipped and conveyed by a registration roller 5 which is a recording material supply means.
After that, the photosensitive drum 1 is cleaned by a cleaning unit such as the blade 7 to prepare for the next image forming step.

On the other hand, the recording material P carrying the toner image is conveyed through the entrance guide plate 8 while being heated and pressed by a fixing roller 9 and a pressure roller 10 having a heating source (not shown) inside. Finish fixing.

[0004]

However, in the above-mentioned structure, image disturbance may occur at the fixing stage. The most prominent form of this image disturbance is the one in which a part of the horizontal line image that is nearly parallel to the axial direction of the fixing roller is scattered to the rear end side and is chipped. If there is such a disorder, ruled lines and the like in the front document may be missing, resulting in an unsightly image. Further, the higher the process speed of the apparatus, the more noticeable this image disturbance becomes, which is an obstacle to speeding up. It is estimated that the main cause of this image distortion is the pressure of steam generated from inside the paper. That is, as shown in FIG. 11, the vapor ejected between the fixing roller 9 and the paper P flows in the direction of the arrow and is compressed between the fixing roller 9, the paper P and the toner image 13 to disturb the toner image 13. Becomes

It has been known to provide a means for applying a bias voltage to the transport system around the fixing device as one of the countermeasures. FIG. 12 shows an example in which a bias applying means, which is a conventional measure against image disturbance, is provided. As shown in the figure, the recording material P on which the toner image on the photosensitive drum 1 is transferred by the transfer roller 6 is applied with a bias of about 2 kV to 5 kV by the electrodes 11 provided in the entire length of the transport system 25, and the recording material P is transferred. It is electrostatically firmly held on P, and is nipped and conveyed by the fixing roller 9 and the pressure roller 10 in this state. Therefore, even if the vapor flow as described above occurs, the disturbance of the toner image on the recording material P can be prevented.

However, in this prior art, the electrodes of the applied bias are arranged over the entire length of the recording material P to be supplied,
Moreover, since the applied bias is large, it may be difficult to secure the creeping distance and the spatial distance, which are also stipulated by the electrical safety standards such as IEC950 for securing the safety of the device.
Further, since the electrodes are provided in the image area as well, the toner adheres to the electrodes, especially on a double-sided machine, which may stain the back of the recording material.

Further, the above phenomenon may similarly occur in a film type fixing device.

Therefore, the present invention is a low-priced fixing device which does not cause the above-mentioned disturbance of the toner image even when the fixing speed of the heat roller type or film type fixing device is increased along with the increase of the process speed. The purpose of the present invention is to provide a fixing device.

Further, according to the present invention, in an image forming apparatus provided with a fixing device of a heat roller type or a film type, an inexpensive image which does not cause the above-mentioned disturbance of the toner image even when the process speed is increased. An object is to provide a forming device.

[0010]

According to the first invention of the present application, the above object is to provide a recording material on which an electrostatic latent toner image is formed, at least one of which includes a heating body and is pressed against each other. In the fixing device, which is nipped and conveyed by a fixing roller and a pressure roller that are rotatably disposed, and heats and presses the recording material and the toner image to fix the toner image on the recording material, The bias voltage applied to the electrode is provided with an electrode arranged so as to come into contact with a part of the recording material upstream of the pressure contact portion of the roller in the recording material conveyance direction, and a means for applying a bias voltage to the electrode. This is achieved by grounding the fixing roller so that the electric current due to the recording material flows through the recording material and the fixing roller.

According to the second invention of the present application,
The above-mentioned purpose is to provide a recording material on which an electrostatic toner image is formed,
The recording material and the toner image are nipped and conveyed by a heat-resistant film and a pressure roller arranged so as to be in pressure contact with a heating body through the heat-resistant film, and the toner image is recorded on the recording material by heating and pressing. In the fixing device for fixing, it is arranged so as to come into contact with a part of the recording material on the upstream side in the recording material conveying direction with respect to the pressure contact portion between the heating body and the pressure roller formed via the heat resistant film. An electrode and a means for applying a bias voltage to the electrode are provided, and the heat resistant film is grounded so that a current due to the bias voltage applied to the electrode flows through the recording material and the heat resistant film. It is achieved by

Further, according to the third invention of the present application, in the above-mentioned object, the electrode for applying the bias voltage is brought into contact with the non-image area of the recording material in the first invention or the second invention. It is achieved by arranging so that

According to the fourth invention of the present application,
The above-mentioned object is achieved by making the surface layer of the fixing roller or the heat resistant film have a lower resistance than the surface layer of the pressure roller in any of the first to third inventions.

Further, according to the fifth invention of the present application, the above object is to provide an image bearing member having a photosensitive layer, a charging unit for charging the image bearing member, and an exposing unit for exposing the image bearing member. A developing device for developing an electrostatic latent image formed on the image carrier with toner, recording material supplying means for supplying a recording material, and a toner image formed on the image carrier for the recording material. A transfer device that can electrostatically transfer to the top,
At least one of which includes a fixing roller that includes a heating element and is rotatably disposed so as to be in pressure contact with each other, and a fixing device that has a pressure roller, and the recording material on which the toner image is electrostatically transferred is fixed to the fixing device. In the image forming apparatus for forming an image by fixing the toner image on the recording material by heating and pressing while sandwiching and conveying the recording material in the pressure contact portion, the recording material conveying direction is more than the pressure contact portion of the fixing roller and the pressure roller. An electrode disposed so as to come into contact with a part of the recording material on the upstream side, and a means for applying a bias voltage to the electrode are provided, and a current caused by the bias voltage applied to the electrode causes the recording material and the fixing roller to move. This is accomplished by having the fuser roller grounded so that it can flow through.

According to the sixth invention of the present application,
The above-mentioned objects are: an image bearing member having a photosensitive layer; a charging unit for charging the image bearing member; an exposing unit for exposing the image bearing member; and an electrostatic latent image formed on the image bearing member as a toner. A developing device for developing by means of, a recording material supplying means for supplying a recording material, a transfer device for electrostatically transferring the toner image formed on the image carrier onto the recording material, a heat resistant film, and A fixing device having a pressure roller that is in pressure contact with a heating body via a heat-resistant film, and the recording material on which the toner image is electrostatically transferred is heated and applied while being nipped and conveyed by the pressure contact portion of the fixing device. In an image forming apparatus that presses and fixes the toner image on a recording material to form an image,
An electrode arranged so as to come into contact with a part of the recording material on the upstream side in the recording material conveying direction from the pressure contact portion between the heating body and the pressure roller formed via the heat resistant film, and the electrode. And a means for applying a bias voltage, wherein the heat resistant film is grounded so that a current due to the bias voltage applied to the electrode flows through the recording material and the heat resistant film. .

Further, according to the seventh invention of the present application, in the above-mentioned fifth invention or sixth invention, the object is to contact an electrode for applying a bias voltage with a non-image area of a recording material. It is achieved by arranging so that

According to the eighth invention of the present application,
The above-mentioned object is achieved by making the surface layer of the fixing roller or the heat resistant film have a lower resistance than the surface layer of the pressure roller in any one of the fifth to seventh inventions.

[0018]

According to the first invention of the present application, the electrode for contacting a part of the recording material is provided on the upstream side of the pressure contact portion of the fixing roller and the pressure roller in the recording material conveying direction, and the bias applying means is provided. The electric current due to flows through the recording material and the fixing roller on the toner image supporting surface side of the recording material, so that the toner image on the recording material is supported on the recording material by the electric field. Therefore, the fixing is performed without disturbing the toner image even if the vapor flow occurs at the pressure contact portion.

According to the second invention of the present application,
An electrode that comes into contact with a part of the recording material is provided on the upstream side in the recording material conveyance direction with respect to the pressure contact portion between the heating body and the pressure roller formed via the heat resistant film, and the current applied by the bias applying means is Since the toner image flows on the recording material through the heat resistant film on the toner image supporting surface side, the toner image on the recording material is supported on the recording material by the electric field. Therefore, the fixing is performed without disturbing the toner image even if the vapor flow occurs in the pressure contact portion.

Further, according to the third invention of the present application, in the first or second invention, the electrode for applying the bias voltage is in contact with the non-image area of the recording material. The toner does not adhere to the recording material and the backside of the recording material does not stain.

According to the fourth invention of the present application,
In any one of the above-mentioned first to third inventions,
Since the surface layer of the fixing roller or the heat-resistant film has a lower resistance than the surface layer of the pressure roller, the toner image is supported on the recording material by the electric field described above without using an element such as a diode, and Reduce the disturbance.

Further, according to the fifth invention of the present application, an electrode that contacts a part of the recording material is provided on the upstream side in the recording material conveying direction with respect to the pressure contact portion between the fixing roller and the pressure roller in the fixing device. Since the current provided by the bias applying means flows through the recording material and the fixing roller on the toner image supporting surface side of the recording material, the toner image on the recording material is supported on the recording material by the electric field. Therefore, even if a vapor flow occurs in the pressure contact portion, fixing is performed without disturbing the toner image, and a good image is formed.

According to the sixth invention of the present application,
An electrode that comes into contact with a part of the recording material is provided on the upstream side in the recording material conveyance direction with respect to the pressure contact portion between the heating body and the pressure roller formed via the heat resistant film, and the current by the bias applying means is applied to the recording material and the recording material. Since the toner image flows on the recording material through the heat resistant film on the toner image supporting surface side, the toner image on the recording material is supported on the recording material by the electric field. Therefore, even if a vapor flow occurs at the pressure contact portion, fixing is performed without disturbing the toner image, and a good image is formed.

Further, according to the seventh invention of the present application, in the fifth invention or the sixth invention, the electrode for applying the bias voltage contacts the non-image area of the recording material. The toner does not adhere to the recording material and the backside of the recording material does not stain.

According to the eighth invention of the present application,
In any of the above fifth to seventh inventions,
Since the surface layer of the fixing roller or the heat-resistant film has a lower resistance than the surface layer of the pressure roller, the toner image is supported on the recording material by the electric field described above without using an element such as a diode, and Reduce the disturbance.

[0026]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic view of the image forming apparatus of this embodiment. In the figure, a photosensitive drum 1 as an image carrier uniformly charged by a charging means such as a charger 2 forms a latent image by an exposing means 3, and the latent image is rotated by a rotation in the direction of the arrow to develop the latent image in a developing device. 4 is conveyed to a portion facing the same. Then, after being visualized as a toner image by the developing device 4, it is transferred by a transfer means such as a transfer roller 6 onto the recording material P nipped and conveyed by a registration roller 5 which is a recording material supply means. After this,
The photosensitive drum 1 is cleaned by cleaning means such as the blade 7 and prepared for the next image forming step.

On the other hand, the recording material P carrying the toner image is guided through the conveying system 25 and the entrance guide plate 8 to the fixing roller 9 and the pressure roller 10 which have a heating source (not shown) inside, The toner image is fixed by being heated and pressed while being nipped and conveyed in the nip portion of both rollers. In the apparatus of this embodiment, however, the image is disturbed at the time of fixing by configuring the fixing device as follows. Is being prevented.

FIG. 2 is a schematic view of the roller heating and fixing device in this embodiment. The fixing roller 9 has an outer diameter of 30 mm,
About 30 μm on an aluminum cylinder 9a with a wall thickness of 3 mm
It has a thick surface layer 14 of fluororesin such as PFA.
Further, a halogen heater 15 as a heating body is provided inside, and the fixing roller 9 is heated by a predetermined control so that the temperature of the fixing roller 9 becomes an appropriate temperature. The pressure roller 10 has an outer diameter of 27
An elastic layer 10b of conductive silicone sponge is provided on a core metal 10a having an outer diameter of 14 mm, and a nip for giving a sufficient amount of heat for fixing is pressed against the fixing roller 9. The uppermost layer of the pressure roller 10 is 30 μm.
It is formed of a thick PFA tube 16 to improve releasability. Further, the entrance guide plate 8 determines the position where the recording material P enters the nip, and prevents paper wrinkles and the like. In this embodiment, the electrode 26 is attached to a part of the tip of the inlet guide plate 8.
And a bias was applied by the bias applying means E.

FIG. 3 is an enlarged view of the electrode 26. An aluminum material 17 (1.5 mm × 1.
5 mm × 10 mm), and the conductive brush 18 was provided thereon. The conductive brush 18 is made of a soft material that has a small contact resistance while reliably contacting when the recording material P is conveyed.

FIG. 4 is a view of the entrance guide plate 8 as viewed from above. Since the apparatus of the present embodiment is based on the central sheet feeding standard, the electrode 26 is provided substantially in the center of the entrance guide plate 8. This allows
For all recording material sizes, the image distortion was improved with some electrodes instead of being arranged over the entire length.

Further, at this time, as shown in FIG. 2, the high withstand voltage diode 19 is inserted so that the applied current does not flow to the pressure roller 10, and the applied bias current is surely passed through the fixing roller 9 to GND (ground portion). The same applies to the following.
Image disturbance did not occur at all with an applied voltage.

As a result, a good image could be formed even when the process speed of the image forming apparatus was increased.

Further, according to this embodiment, the electrode is brought into contact with a part of the recording material, so that the apparatus can be simplified. Further, by facilitating the current due to the applied bias to flow to the GND through the roller or film on the toner image supporting surface side, the efficiency of the bias application effect against the image disturbance is increased, the applied bias voltage value is reduced, and the apparatus is inexpensive. can do.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. The first
The same parts as those of the above embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 5 is a schematic view of a roller heating fixing type fixing device according to the second embodiment of the present invention. The fixing device of this embodiment is also arranged in the image forming apparatus as shown in FIG. It is a thing.

This embodiment is different from the first embodiment in that the surface layer 14 of the fixing roller 9 has a low resistance (10 ⁹ to 10 ¹² Ω · m) by dispersing carbon or the like in a fluororesin such as PFA. In this respect, the applied current has a high resistance (10 ¹³
It is difficult for the pressure roller 10 having a pressure of 10 ¹⁴ Ω · m) to flow,
It flows to GND via the fixing roller 9. With the above configuration, a sufficient effect can be obtained against image distortion even without an element such as a diode.

The electrodes may be arranged in the vicinity of the nip, and may be arranged as shown in FIG. 6, for example. The electrode 27 can be provided by plating, coating, pasting, or the like with a low electric resistance material such as metal or conductive plastic. In this experiment, the electrode 27 is 5 mm × 5 m with a thickness of 0.1 mm.
A copper plate of m was attached to the tip of the inlet guide plate 8 with a very slight step so that the tip of the recording material P would not be caught. At this time, the leading end of the entrance guide plate 8 is disposed at a position (above the tangent line of the nip) from the fixing roller 9 with respect to the nip portion between the fixing roller 9 and the pressure roller 10 so that the recording material P is always electroded. It came into contact with 27.

FIG. 7 is a view of the entrance guide plate 8 as seen from above. The apparatus of the present embodiment is a one-sided sheet passing standard, and the electrode 27 is arranged on the entrance guide 8 plate in the sheet passing area (non-image area) outside the image area outside the hatched portion of the recording material P in the drawing. As a result, it is possible to drastically reduce the toner adhesion to the electrodes 27 by the double-sided mechanism or the like, and to suppress the back stain of the recording material P.

As described above, according to the present embodiment, even when the process speed of the image forming apparatus is increased, it is possible to perform good image formation without image disturbance and without stain on the back side of the recording material.

Further, according to this embodiment, the electrode is brought into contact with a part of the recording material, so that the apparatus can be simplified. Further, by facilitating the current due to the applied bias to flow to the GND through the roller or film on the toner image supporting surface side, the efficiency of the bias application effect against the image disturbance is increased, the applied bias voltage value is reduced, and the apparatus is inexpensive. can do.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIGS. 8 and 9. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 8 is a schematic side view of film heat fixing showing a third embodiment of the present invention, and the apparatus of this embodiment is also shown in FIG.
The image forming apparatus as shown in FIG.

Since the endless fixing film 20 which is rotationally driven as shown in FIG. 8 is repeatedly subjected to heat fixing of the toner image, it is excellent in heat resistance, releasability and durability.
Further, generally, a thin film having a thickness of 100 μm or less, preferably less than 40 μm is used. For example, a single layer film of a heat-resistant resin such as polyimide, polyetherimide, PES, PFA, or a composite layer film, for example, a 20 μm thick film, a release coating layer in which a conductive agent is added to a PTFE resin on at least the image contact surface side. Is applied to have a thickness of 10 μm.

Reference numeral 21 denotes a pressure roller having a rubber elastic layer having a good releasing property such as silicone rubber as a pressure member,
The lower film portion of the endless belt-shaped fixing film 20 is sandwiched and is pressed against the lower surface of the heating body 23 by a biasing means (not shown) at a total pressure of, for example, 4 to 7 kg. The material P rotates in the counterclockwise direction in the forward direction.

The heating body 23 is horizontally long with the crosswise direction of the fixing film (direction perpendicular to the running direction) as the longitudinal direction, and is integrally formed along the longitudinal direction of the lower surface of the support body 24 having rigidity, high heat resistance, and high heat conductivity. It is attached and held.

Also in this embodiment, the electrode 28 is provided at the tip of the inlet guide plate 8, but the electrode 28 may be arranged as shown in FIG. But in both cases,
It is in contact with the non-image area portion of the recording material P on the image surface side. The applied current is in contact with the side surface of the recording material P and the fixing film 20. The image disturbance is prevented by flowing from the fixing film contact 22 made of a conductive brush to the GND.

Further, according to this embodiment, the electrode is brought into contact with a part of the recording material, so that the apparatus can be simplified. Further, by facilitating the current due to the applied bias to flow to the GND through the roller or film on the toner image supporting surface side, the efficiency of the bias application effect against the image disturbance is increased, the applied bias voltage value is reduced, and the apparatus is inexpensive. can do.

Although the same applies to the first and second embodiments, it has been found by experiments whether the polarity of the applied bias is positive or negative and is effective for image distortion.

Further, in each of the above embodiments, the case where the inlet guide provided with the electrode is provided integrally with the fixing device has been described, but the present invention is not limited to this, and the fixing device is provided between the transfer portion and the fixing portion. An electrode may be provided at the tip of a conveyance guide provided separately from the above.

[0051]

As described above, the first aspect of the present application
According to the invention, an electrode is provided on the upstream side of the pressure contact portion of the fixing roller and the pressure roller in the recording material conveying direction, and the electrode is in contact with a part of the recording material instead of the entire length, and the bias is applied by the bias applying means. Therefore, it is possible to fix the toner image without disturbing the toner image even if the vapor flow occurs at the pressure contact portion. Further, since the electrode may be brought into contact with a part of the recording material, the electrode can be made smaller than the conventional one and can be arranged at any position. Further, since the required effect can be obtained with a low applied bias, the fixing device can be made compact and the cost can be reduced.

According to the second invention of the present application,
An electrode is provided which is in contact with a part of the recording material in the longitudinal direction of the recording material, rather than the entire area of the recording material, in the upstream side of the pressure contact portion between the heating member and the pressure roller formed through the heat-resistant film. Is applied, it is possible to perform fixing without disturbing the toner image even if the flow of vapor occurs at the pressure contact portion. Further, since the electrode may be brought into contact with a part of the recording material, the electrode can be made smaller than the conventional one and can be arranged at any position. Further, since the required effect can be obtained with a low applied bias, the fixing device can be made compact and the cost can be reduced.

Further, according to the third invention of the present application, in the first or second invention, the electrode for applying the bias voltage is arranged so as to be in contact with the non-image area of the recording material. Since it is provided, it is possible to drastically reduce the toner adhesion to the electrodes, and it is possible to suppress the back stain of the recording material.

According to the fourth invention of the present application,
In any one of the above-mentioned first to third inventions,
Since the surface layer of the fixing roller or the heat-resistant film has a lower resistance than the surface layer of the pressure roller, image distortion can be suppressed and a good fixing operation can be performed even without an element such as a diode.

Further, according to the fifth invention of the present application, an electrode contacting a part of the recording material is provided on the upstream side in the recording material conveying direction with respect to the pressure contact portion between the fixing roller and the pressure roller in the fixing device. Since a bias is applied by the provision and bias applying means, it is possible to perform fixing without disturbing the toner image even if a vapor flow occurs at the pressure contact portion, and it is possible to form a good image. Further, since the electrode may be brought into contact with a part of the recording material, the electrode can be made smaller than before,
Can be placed in any position. Furthermore, since the required effect can be obtained with a low applied bias, the image forming apparatus as a whole can be made compact and the cost can be reduced.

According to the sixth invention of the present application,
On the upstream side in the recording material conveyance direction from the pressure contact portion between the heating body and the pressure roller formed via the heat resistant film of the fixing device,
Since an electrode is provided in contact with a part of the recording material and a bias is applied by the bias applying means, it is possible to perform fixing without disturbing the toner image even if a flow of vapor occurs at the pressure contact portion, and a good image can be obtained. Can be formed. Also,
Since it suffices that the electrode be brought into contact with a part of the recording material, the electrode can be made smaller than before and can be arranged at any position. Furthermore, since the required effect can be obtained with a low applied bias, the image forming apparatus as a whole can be made compact and the cost can be reduced.

Further, according to the seventh invention of the present application, in the fifth invention or the sixth invention, the electrode for applying the bias voltage is arranged so as to contact with the non-image area of the recording material. Since it is provided, it is possible to drastically reduce the toner adhesion to the electrodes, and it is possible to suppress the back stain of the recording material.

According to the eighth invention of the present application,
In any of the above fifth to seventh inventions,
Since the surface layer of the fixing roller or the heat-resistant film has a lower resistance than the surface layer of the pressure roller, image disturbance can be suppressed and a good image forming operation can be performed even without an element such as a diode.

[Brief description of drawings]

FIG. 1 is a schematic view of an image forming apparatus including a roller heating type fixing device according to a first embodiment of the present invention.

FIG. 2 is a schematic view of a roller heating type fixing device according to the first embodiment of the present invention.

FIG. 3 is an enlarged view of the vicinity of electrodes in the first embodiment of the present invention.

FIG. 4 is a view of the periphery of an electrode according to the first embodiment of the present invention as viewed from above.

FIG. 5 is a schematic view of a roller heating type fixing device according to a second embodiment of the present invention.

FIG. 6 is an enlarged view of the periphery of an electrode in the second embodiment of the present invention.

FIG. 7 is a diagram of the vicinity of electrodes in a second embodiment of the present invention as seen from above.

FIG. 8 is a schematic view of a film heating type fixing device according to a third embodiment of the present invention.

FIG. 9 is a diagram showing an arrangement state of electrodes in a third embodiment of the present invention.

FIG. 10 is a schematic side view of a conventional image forming apparatus.

FIG. 11 is a schematic diagram for explaining conventional image distortion.

FIG. 12 is a schematic view showing an image forming apparatus provided with a bias applying unit which is a conventional image disturbance countermeasure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum (image carrier) 2 Charging device (charging means) 3 Exposure means 4 Developing device 5 Registration roller (recording material supply means) 6 Transfer roller (transfer means) 9 Fixing roller 10 Pressure roller 14 Surface layer of fixing roller 15 Halogen Heater (Heating Body) 16 PFA Tube (Surface Layer of Pressure Roller) 20 Fixing Film (Heat Resistant Film) 21 Pressure Roller 23 Heating Body 26, 27, 28 Electrode E Bias Applying Means

Claims (8)

[Claims] 1. A recording material on which an electrostatic toner image is formed is nipped and conveyed by a fixing roller and a pressure roller which are rotatably arranged in pressure contact with each other and have a heating body at least on one side. In a fixing device that heats and presses a recording material and a toner image to fix the toner image on the recording material, a part of the recording material comes into contact with the recording material in the conveying direction upstream of a pressure contact portion of the fixing roller and the pressure roller. And a means for applying a bias voltage to the electrode, and the fixing roller is configured so that the current due to the bias voltage applied to the electrode flows through the recording material and the fixing roller. A fixing device characterized by being grounded. 2. A recording material on which an electrostatic toner image is formed is nipped and conveyed by a heat resistant film and a pressure roller arranged so as to be in pressure contact with a heating body through the heat resistant film, In a fixing device for fixing the toner image on the recording material by heating and pressing the recording material and the toner image, the recording material is more than the pressure contact portion between the heating body and the pressure roller formed via the heat resistant film. An electrode arranged so as to come into contact with a part of the recording material on the upstream side in the transport direction and a means for applying a bias voltage to the electrode are provided, and a current due to the bias voltage applied to the electrode is applied to the recording material and the above. The fixing device is characterized in that the heat resistant film is grounded so as to flow through the heat resistant film. 3. The fixing device according to claim 1, wherein an electrode for applying a bias voltage is arranged so as to be in contact with a non-image area of the recording material. 4. The fixing device according to claim 1, wherein the surface layer of the fixing roller or the heat resistant film has a resistance lower than that of the surface layer of the pressure roller. 5. An image carrier having a photosensitive layer, a charging means for charging the image carrier, an exposing means for exposing the image carrier, and an electrostatic latent image formed on the image carrier. A developing device for developing with toner, a recording material supplying means for supplying a recording material, a transfer device for electrostatically transferring a toner image formed on the image carrier onto the recording material, and heating for at least one of them. A fixing device having a fixing roller and a pressure roller that rotatably encloses the body and is in pressure contact with each other is provided, and the recording material on which the toner image is electrostatically transferred is attached to a pressure contact portion of the fixing device. In an image forming apparatus that forms an image by fixing a toner image on the recording material by heating and pressing while sandwiching and conveying the recording material, the recording material is upstream of a pressing contact portion of the fixing roller and the pressure roller. Arranged to contact part of And a means for applying a bias voltage to the electrode, and the fixing roller is grounded so that a current due to the bias voltage applied to the electrode flows through the recording material and the fixing roller. An image forming apparatus characterized by the above. 6. An image carrier having a photosensitive layer, a charging unit for charging the image carrier, an exposing unit for exposing the image carrier, and an electrostatic latent image formed on the image carrier. A developing device for developing with a toner, a recording material supply means for supplying a recording material, a transfer device for electrostatically transferring a toner image formed on the image carrier onto the recording material, a heat resistant film, and A fixing device having a pressure roller that is in pressure contact with a heating body through the heat resistant film, and heating and heating the recording material on which the toner image is electrostatically transferred while being nipped and conveyed by a pressure contact portion of the fixing device. In an image forming apparatus that pressurizes and fixes the toner image on a recording material to form an image, in the recording material conveyance direction upstream of a pressure contact portion between the heating body and the pressure roller formed via the heat resistant film. Side contact with part of recording material An electrode arranged so that a bias voltage is applied to the electrode, and the current by the bias voltage applied to the electrode flows through the recording material and the heat-resistant film. The image forming apparatus is characterized in that the heat resistant film is grounded. 7. The image forming apparatus according to claim 5, wherein an electrode for applying a bias voltage is arranged so as to contact a non-image area of the recording material. 8. The image forming apparatus according to claim 5, wherein the surface layer of the fixing roller or the heat resistant film has a lower resistance than the surface layer of the pressure roller.