JPH0546550B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a fixing device installed in a recording device such as an electrophotographic device or an electrostatic recording device. Specifically, the present invention relates to a fixing device installed in a recording device such as an electrophotographic device or an electrostatic recording device. The present invention also relates to a fixing device that extremely effectively prevents offset of an object to be fixed that occurs on a rotating body for heating and pressurizing. 2. Description of the Related Art Conventionally, in a fixing device for an image forming apparatus that fixes an unfixed image onto a surface of plain paper, a fixing device in which a recording material such as plain paper is held and conveyed between a fixing roller and a pressure roller is often used. This type of roller has a problem in that frictional charging occurs due to contact between the plain paper and the roller, and the plain paper wraps around the roller surface. As a means to solve this problem, Japanese Utility Model Publication No. 57-41793 and Japanese Unexamined Patent Application Publication No. 56-143474 propose a method in which a static elimination brush is simply brought into contact with the roller surface, or an alternating current bias is applied via this static elimination brush. Things are listed. However, in either case, the tip of the static elimination brush becomes contaminated with toner and paper powder, resulting in a sharp drop in static elimination efficiency. That is, the static elimination ability deteriorated over time to a large extent and the durability was poor. Furthermore, although the static elimination effect achieved by the static elimination method described above is effective to some extent in terms of preventing the recording material from wrapping around the roller, the static elimination brush does not contain toner particles, paper dust, oil, etc.
Due to contamination with other foreign substances, the static elimination ability changes greatly over time and the static elimination efficiency decreases rapidly, so the effect of preventing toner offset to the fixing roller is incomplete, and the fixing roller cleaning method In some cases, offset toner was generated that could not be cleaned due to the blade (blade, felt, etc.). The present invention has been made to solve the above-mentioned problems, and includes a pair of fixing rotors that nip and convey a recording material that supports an object to be fixed and fixes it, and a static eliminator that eliminates static electricity from the surface of the fixing rotors. In the fixing device, the static eliminator has a grounded conductive member and an insulating layer provided on the conductive member except for at least the leading edge of the conductive member on the side of the fixing rotor. By making a small gap between the leading edge of the conductive member and the surface of the fixing rotor by bringing it into contact with the fixing rotor, the static eliminating member's tip will not be contaminated with toner or paper dust, and the static eliminating effect will last for a long time. It is an object of the present invention to provide a fixing device that can maintain high performance and largely prevent the occurrence of offset phenomena. Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic explanatory diagram of an embodiment of the present invention. This shows a device in which a toner image T formed by electrophotography is fixed onto a recording material 17 by a heat fixing device. There, reference numeral 1 denotes a heating roller having a heating heater 3 such as a halogen heater therein, which rotates in the direction of the arrow in response to a driving force from a driving motor (not shown). Reference numeral 2 denotes a pressure roller having a built-in heater 3' for low heating, which is brought into pressure contact with the heating roller 1 and rotates by sliding. This heating roller 1 has a heat-resistant mold release resin layer such as tetrafluoroethylene resin provided on the outer peripheral surface of a metallic hollow roller core made of aluminum, stainless steel, copper, etc. to a thickness of 20 to 80 μm. The pressure roller 2 is rotatably supported by a bearing (not shown). This pressure roller 2 is pressed against the heating roller 1 by a known pressure means at least during fixing, and the outer peripheral surface of the metal roller core is made of silicone rubber,
It has a relatively thick layer of elastic material such as fluorosilicone rubber or fluorosilicone rubber. This configuration has a pressure contact area with the heating roller 1 (hereinafter referred to as a nip portion).
The purpose is to ensure that A temperature sensing element 4 such as a thermistor or thermocouple is disposed in contact with the outer peripheral surface of the heating roller 1, and its detection signal is guided to a known control means (not shown) to control the temperature of the outer peripheral surface of the heating roller 1 (heater The toner image melting temperature is maintained by controlling the output of No. 3 or the applied voltage, etc.). Reference numerals 51 and 52 are separation claws for reliably separating the recording material 17 from the rollers 1 and 2 after fixing, and 51 and 52 are provided on the surface of the heating roller 1 and 52 on the surface of the pressure roller 2, respectively. It is placed so that it touches. Reference numeral 6 denotes a cleaning member for removing foreign matter such as offset toner and paper powder adhering to the surface of the heating roller 1 from the roller surface, and the cleaning member is made of a heat-resistant nonwoven fabric such as Nomex (registered trademark) or Himeron (registered trademark). web 61
A material impregnated with an offset prevention liquid such as dimethyl silicone oil is used. The cleaning web 61 is brought into contact with the heating roller 1 by a pressing roller 63 having elasticity such as silicone rubber, soft rubber, fluorosilicone rubber, silicone rubber sponge, or the like. In addition, this cleaning web 61
is driven by the winding roller 65,
The cleaning web 61 is moved from the supply roller 62 so as to change its contact position little by little, so that a new surface of the cleaning web 61 is always brought into contact with the heating roller 1 . Reference numeral 7 denotes a guide plate that guides the recording material 17 carrying the toner image T toward the heating roller 1 side. Reference numeral 8 denotes a static eliminator that is a feature of the present invention, in which a large number of flexible needle-shaped static eliminators 82 for neutralizing the surface of the pressure roller 2 are embedded in a grounded conductive base 81. . They are arranged in a plurality of rows in the longitudinal direction of the pressure roller 2, and the distal end of the static eliminating member 82 contacts the surface of the pressure roller 2 in the rotational direction of the pressure roller 2. It is set in. In addition, the static eliminating member 8
2 includes a conductive part 82a made of conductive fibers such as metal fibers or carbon fibers, and an insulating part made of insulating resin, etc., as described later in FIGS. 3 to 8 as examples. 82b, and the insulating part 8
The tip of the conductive portion 82a is in contact with the surface of the pressure roller 2, and the tip of the conductive portion 82a is close to or in contact with the surface of the pressure roller 2. Next, an example of an electrophotographic apparatus to which the fixing device according to the present invention having the above configuration can be applied will be briefly described with reference to FIG. The photosensitive drum 9 is uniformly charged by a primary charger 10, and then re-charged by a secondary charger 11 that charges the polarity opposite to that of the primary charger 10. At the same time, a lamp 12
The original image is irradiated with light, and this light image is applied to the photosensitive layer on the surface of the photosensitive drum 9 via the optical system 13. Then,
An electrostatic latent image is formed on the surface of the photosensitive drum 9 according to the pattern of the optical image, and then the entire surface exposure lamp 14
As a result, an electrostatic latent image with even higher contrast is formed. Next, the latent image is developed by the developing device 15 and made visible. Next, the visible image on the photosensitive drum 9 is transferred onto a recording material 17 such as paper supplied from the cassette 16 by the action of the transfer charger 11, and the transferred toner image is transferred to the heating roller 1 and the pressure roller 2. It is heat-fixed by The drum 9 is cleaned by the blade cleaning means 19 and reused. When the recording material 17 is thermally fixed between the heating roller 1 and the pressure roller 2, the pressure roller 2 is charged to a positive polarity due to frictional charging with the pressure roller 2, and the pressure roller 2 is charged to a negative polarity. The charge on the pressure roller 2 is removed by the charge remover 8. Next, specific examples of the static eliminating member 82, which is a feature of the present invention, will be described in detail below. FIG. 3 is an enlarged sectional view of a main part of the first embodiment of the static eliminating member 82. Each of the multiple flexible static eliminating members 82 has an insulating layer (this is formed by coating one side of a conductive portion 82a made of conductive fibers such as metal fibers or carbon fibers with an insulating material such as epoxy resin). 82b (referred to as an insulating part) is formed. These static eliminating members 82 are arranged in multiple rows, and
The pressure roller 2 is disposed in the longitudinal direction of the pressure roller 2, and its tip portion faces the rotation direction of the pressure roller 2 and comes into contact with the surface of the pressure roller 2. At this time,
The tip of the insulating portion 82b is in contact with the surface of the pressure roller 2, and the tip of the conductive portion 82a is in contact with the surface of the pressure roller 2.
close to or in contact with the surface of Note that the surface of the pressure roller 2 is generally rough, with a surface roughness of 5 μm to 20 μm, and therefore is schematically illustrated as uneven. On the other hand, in the conventional technology in which the static eliminating member 82 is made of only a conductive member, when using an electrophotographic apparatus having this technology, the static neutralizing effect is good at the initial stage of use and the offset is small, but the number of copies is reduced. As the amount of offset toner increases, the tip of the static eliminating member 82 becomes contaminated with toner fine powder, paper dust, oil, and other foreign matter, and the static eliminating ability tends to decrease, resulting in a sharp increase in the amount of offset toner. In this regard, in this embodiment, as described above, the static eliminating member 82 is formed with not only the conductive part 82a but also the insulating part 82b, and the tip of the insulating part 82b is in contact with the surface of the pressure roller 2. , the tip of the conductive portion 82a is close to or in contact with the surface of the pressure roller 2. Further, as the insulating material forming the insulating portion 82b, an insulating material such as epoxy resin can be used as a material that easily attracts toner, paper dust, oil, and other dirt, that is, a material that has poor mold release properties. Therefore, even if fine dirt such as fine toner powder, a small amount of oil, or other foreign matter that cannot be cleaned by the cleaning web 61 adheres to the pressure roller 2, the insulating portion 82b completely removes the dirt. The conductive portion 82a
The tip is always clean. Therefore, the static elimination ability does not deteriorate over a long period of time. In addition, as another effect, as shown in FIG. 3, an unequal electric field E is formed between the tip of the conductive portion 82a and the pressure roller 2, which is charged to a high potential due to frictional charging with the recording material. . As a result, the electric field strength increases in the conductive portion 8.
An ionization phenomenon of the gas occurs near the tip of the roller 2a, and positive and negative ion pairs are generated there. Among these ion pairs, ions with opposite polarity to the pressure roller 2 are attracted to the pressure roller 2, and their electric charge and Static electricity is removed by combining and neutralizing. Due to the above-described effects, the present invention has been able to maintain the static elimination effect for a long period of time, which was impossible with the prior art. Next, specific experimental results using the static eliminating member 82 shown in FIG. 3 as a first example will be shown, and its effects will be confirmed. The content of the experiment was to determine the amount of offset toner after 99 sheets were continuously fed and after 100,000 sheets were continuously fed. The experimental conditions are described above. The fixing device is made of a 30 μm thick aluminum core metal with a wall thickness of 7 mm.
Heating roller 1 with outer diameter of 60 mm coated with PFA resin
and a pressure roller 2 with an outer diameter of 60 mm, which has a heat-vulcanized silicone rubber coating with a wall thickness of 5 mm on a stainless steel hollow core metal, and press both rollers together with a total pressure of 60 kg, and further as shown in Fig. 1. It is incorporated into. The cleaning web 61 was fed at a slow speed of 0.5 mm/min. Further, as shown in FIGS. 1 and 3, the static eliminator 8 uses carbon fiber with a wire diameter of 5 μm as a conductive portion 82a, and coats one side of the carbon fiber with a 7 μm thick epoxy resin to form an insulating portion 82b. Multiple static eliminators 8
2 was embedded in a grounded conductive substrate 81. Then, the tips of these insulating parts 82b are placed on the surface of the pressure roller 2.
It was brought into contact 55° downstream from the nip with the rotation axis of the nip as the center of rotation. A3 size plain paper was used as the recording material 17, and the toner image portion to be recorded occupied 28% of the paper area. The amount of toner recorded on the paper was 300 mg/A3 sheet, which was relatively large. The heating roller 1 and the pressure roller 2 performed fixing at a circumferential speed of 270 mm/sec.
The copy speed was 23 sheets/min for A3 paper.
Each experiment was conducted under the above conditions, and as a comparative example, a conventionally known "electrification member 82" was used.
is made of only a conductive needle-like member, and its tip is brought into contact with the pressure roller 2 (hereinafter referred to as conventional example 1).
(hereinafter referred to as Conventional Example 2); We also conducted an experiment in which nothing was used. Table 1 shows the amount of offset toner after 99 sheets were continuously fed. Note that the amount of offset toner was calculated using the following formula. Offset toner amount (%) = cleaning web 61
Amount of toner attached to (mg) / Amount of unfixed toner on plain paper 17 (mg) x 100 Also, since the surface potential () of the pressure roller 2 is closely related to the amount of offset toner, Added to Table 1. Then, from Table 1, 99 sheets are passed continuously.

[Table] shows that there is no difference between the first embodiment and conventional example 1, and in both cases, the amount of offset toner is reduced to 1/4 compared to the case without the static eliminating member. . In addition, in Conventional Example 2, although some effect is seen, it cannot be said to be sufficient, and the cleaning web 61
Offset toner began to accumulate on the cleaning web 61 in an amount that could not be cleaned at the feed speed of 0.5 mm/min, and it became necessary to increase the speed by two to three times. Next, in the case of continuous paper feeding of 100,000 sheets, in the case of the first embodiment, even after 100,000 sheets of paper have been passed, there is only enough offset to allow sufficient cleaning at the feed speed of the cleaning web 61 of 0.5 mm/min. The copy paper was not stained by offset toner at all, and very good images were obtained. On the other hand, in conventional example 1,
Heating roller 1 and pressure roller 2 after passing approximately 6000 sheets.
The toner offset increases rapidly, and the amount of toner that cannot be cleaned with the cleaning web 61 feeding speed of 0.5 mm/min is offset.
Not only a large amount of toner accumulates on the cleaning web 61, but also toner that has fallen from the cleaning web 61 or that has passed through the cleaning web 61 adheres to the copy paper, significantly degrading copy quality. In FIG. 11, the horizontal axis shows the number of sheets to be passed, and the vertical axis shows the amount of offset toner, where curve a-1 is for the first embodiment, curve b is for conventional example 1, and curve c is for conventional example 2. , and curve d is the case where there is no static eliminating member. Further, the broken line e indicates the cleaning limit when the cleaning web feed speed is 0.5 mm/min. That is, in this case, if the amount of offset toner exceeds 0.2%,
This indicates that the cleaning web cannot completely clean stains such as offset toner. As is clear from FIG. 4, in the case of conventional example 2 (curve c) and the case without the static eliminating member (curve d), so much offset toner is generated that the cleaning web 61 cannot clean it from the beginning of paper feeding, and there is almost no effect. It can be said that it has died down. Also, conventional example 1
In the case of (curve b) as well, the amount of offset toner increased rapidly after about 5,000 sheets had been passed, and after 20,000 sheets had been passed, the function of the static eliminating member had completely disappeared. However, in this example, even after 100,000 sheets have been passed, the amount of offset toner is stably small, and the effect is so excellent that there is still plenty of room for the cleaning web's cleaning limit of 0.2%. especially,
The fact that there is no deterioration of the static eliminating ability over time caused by the staining of the static eliminating member 82 with toner, paper dust, etc., and that it is possible to prevent offset over a long period of time, can be said to be a very significant effect. . Next, in the above experiment of the first embodiment, the contact position of the distal end of the static eliminating member 82 to the pressure roller 2 was set at 55° downstream from the nip portion with the rotation axis of the pressure roller 2 as the center of rotation. Table 2 shows the amount of offset toner (%) and the pressure roller surface potential ( ) when 99 sheets were continuously fed by changing the contact position. Note that the experimental equipment and conditions were the same as in the previous experiment. In addition, the static eliminating member 82
The position of the tip portion is shown as an angle from the nip portion downstream to the abutting position with the rotation axis of the pressure roller 2 as the rotation center. Then, as is clear from Table 2,

It can be seen from the table that the closer the tip of the charge eliminating member 82 is to the vicinity of the paper discharge side nip, the more the amount of offset toner and the surface potential of the pressure roller decrease, indicating that the effect of eliminating charges, that is, the effect of preventing offset, is excellent. this is,
This means that the faster the frictional charge between the copy paper and the pressure roller 2 that occurs at the nip portion and the nip outlet is removed, the more effective the charge removal effect will be. Therefore, by bringing the tip of the static eliminating member 82 as close to the nip as possible, a higher static eliminating effect, that is, an offset prevention effect can be obtained. FIG. 4 is an enlarged sectional view of a main part of a second embodiment of a static eliminating member 82, which is a feature of the present invention. In the first embodiment, as shown in FIG. 3, the insulating portion 82b was formed only on the side surface of the static eliminating member 82 that comes into contact with the pressure roller 2, but in the second embodiment, the insulating portion 82b' is also formed on the other side surfaces. The conductive portion 82a is exposed only at the tip of the static eliminating member 82. By doing this, even if one side of the static eliminator 82 becomes dirty with toner, paper dust, etc. and the distance between the tip conductive part 82a and the pressure roller 2 increases and the static eliminator ability decreases, it is possible to turn it over and open the other side. By using this, the service life of the static eliminating member 82 can be doubled. Therefore, it is possible to obtain an excellent static elimination effect for a long period twice as long as that of the first embodiment at a low cost. FIG. 5 is an enlarged sectional view of a main part of a third embodiment of a static eliminating member 82, which is a feature of the present invention. This corresponds to the portion 82 near the tip of the static eliminating member 82 shown in the first embodiment.
The conductive part 82a is formed without forming the insulating part 82b in c.
is exposed and brought into contact with the surface of the pressure roller 2. By doing this, in addition to the static elimination effect due to the ion pairs generated by the ionization phenomenon described above, the electrical charge of the pressure roller 2 is removed from the near-tip portion 82c.
Since the leakage current flows through the conductive portion 82a and the conductive substrate 81, the static elimination effect is further promoted and even better results are obtained. Therefore, the portion near the tip 8
2c was brought into contact with the surface of the pressure roller 2 at a position 55 degrees downstream from the nip portion, and an experiment was conducted in which 99 sheets were continuously passed in the same manner as described above. As a result, the amount of offset toner was
0.13% (pressure roller surface potential -950V),
It was demonstrated that a greater effect can be obtained compared to 0.15% in the first example. In this embodiment as well, by forming the insulating portion 82b' as shown in FIG. 4, the service life of the static eliminating member 82 can be doubled. FIG. 6 is an enlarged sectional view of a main part of a fourth embodiment of a static eliminating member 82, which is a feature of the present invention. In this case, a large number of holes are formed on the surface of the insulating portion 82b that comes into contact with the pressure roller 2 to form conductive holes 82d. In this way, an unequal electric field is formed between the pressure roller 2, which is charged to a high potential due to frictional charging with the copy paper, and the conductive hole 82d. As a result, gas ionization occurs near the conductive hole 82d where the electric field strength increases. There, positive and negative ion pairs are generated, and among these ion pairs, ions of opposite polarity to the pressure roller 2 are attracted to the pressure roller 2, combine with the electrostatic charge thereon, neutralize it, and eliminate the charge. this is,
In combination with the static eliminating action at the tip of the static eliminating member 82, a double static eliminating effect can be obtained. In addition, the insulation part 8
In the experiment of the first embodiment, epoxy resin was used as the material of 2b because it easily collects dirt such as toner and paper dust on the pressure roller 2, but in this embodiment, on the contrary, tetrafluoroethylene resin was used. By using an insulating material with excellent mold releasability, such as, fine dirt is allowed to pass through, and the conductive holes 82d can be kept clean at all times. Therefore, the static elimination ability does not deteriorate over a long period of time. Therefore, the effect will be confirmed by showing specific experimental results using the static eliminating member 82 of the fourth embodiment shown in FIG. The content of the experiment was to determine the amount of offset toner after continuously passing 99 sheets and after continuously passing 100,000 sheets, as in the case of the first embodiment. In the static eliminating member 82 used in this experiment, an insulating part 82b is formed by coating one side of a conductive part 82a made of metal fiber with a wire diameter of 5 μm with a 7 μm thick polytetrafluoroethylene resin. A large number of conductive holes 82d each having a diameter of 1 to 3 μm are formed. Others are 1st
The experiment was conducted under the same conditions as the experiment conducted in the example. The results are shown below. Table 1 shows the amount of offset toner after 99 sheets were continuously fed. Incidentally, the amount of offset toner was calculated using the following formula as in the case of the first embodiment. Offset toner amount (%) = cleaning web 61
Amount of toner attached to (mg) / Amount of unfixed toner on plain paper 17 (mg) x 100 Furthermore, since the surface potential () of the pressure roller 2 is closely related to the amount of offset toner, Added to Table 1. Then, from Table 1, it can be seen that when 99 sheets are continuously fed, the amount of offset toner in the fourth embodiment is reduced to 1/4 or less compared to the case without the static eliminating member. Moreover, even better results are obtained when compared with the first example. Next, the change in the amount of offset toner during continuous feeding of 100,000 sheets in the fourth embodiment is shown in FIG. 11 as a curve a-2. As is clear, it can be seen that the first embodiment exhibits an even more excellent effect than the first example, which exhibited far superior performance to the conventional examples (curves b and c). That is, this is because the conductive holes 82d formed in the static eliminating member 82 of this embodiment further promote the static eliminating action and can prevent offset over a long period of time. In the above experiment of the fourth embodiment, the static eliminating member 82
The contact position of the tip part against the pressure roller 2 was determined to be 55° downstream from the nip part with the rotation axis of the pressure roller 2 as the rotation center, but next, this contact position was changed variously. Table 3 shows the offset toner amount (%) and pressure roller surface potential () when 99 sheets were continuously fed. Note that the experimental equipment and conditions were the same as in the previous experiment. In addition, the static eliminating member 82
The position of the tip is determined by the angle from the nip toward the downstream to the contact position with the rotation axis of the pressure roller 2 as the center of rotation.

It is shown in [Table]. Then, as is clear from Table 3,
It can be seen that the closer the tip of the charge eliminating member 82 is to the vicinity of the paper discharge side nip, the more the amount of offset toner and the surface potential of the pressure roller decrease, and the better the charge eliminate effect, that is, the offset prevention effect. This is the first
As in the case of the embodiment (shown in Table 2), the more quickly the static electricity is removed from the frictional peeling charge between the copy paper and the pressure roller 2 that occurs at the nip portion and the nip exit, the more the static electricity removal effect increases. It means. Therefore, by bringing the tip of the static eliminating member 82 as close to the nip as possible, a higher static eliminating effect, that is, an offset prevention effect can be obtained. FIG. 7 is an enlarged sectional view of a main part of a fifth embodiment of a static eliminating member 82, which is a feature of the present invention. In the fourth embodiment, as shown in FIG. 6, the insulating portion 82b and the conductive hole 82d were formed only on the side surface of the static eliminating member 82 that comes into contact with the pressure roller 2, but in this embodiment, the other surfaces are also insulated. A portion 82b' and a conductive hole 82d' are formed, and the conductive portion 82a is exposed only at the tip of the static eliminating member 82. By doing this, even if one side of the static eliminating member 82 is contaminated with toner, paper powder, etc. and the static eliminating ability is reduced, the usage life of the static eliminating member 82 can be doubled by turning it over and using the other side. becomes possible. Therefore, an excellent static elimination effect can be obtained for a long period twice as long as that of the fourth embodiment at a low cost. FIG. 8 is an enlarged sectional view of a main part of a sixth embodiment of a static eliminating member 82, which is a feature of the present invention. This is similar to the portion 82 near the tip of the static eliminating member 82 shown in the fourth embodiment.
The conductive part 82a is formed without forming the insulating part 82b in c.
is exposed and brought into contact with the surface of the pressure roller 2. By doing this, in addition to the static elimination effect due to the ion pairs generated by the ionization phenomenon described above,
Since the electrical charge of the pressure roller 2 flows as a leakage current from the near-tip portion 82c through the conductive portion 82a and the conductive base 81, the static elimination effect is further promoted and even better results are obtained. Therefore, the portion near the tip 8
2c was brought into contact with the surface of the pressure roller 2 at a position 55 degrees downstream from the nip portion, and an experiment was conducted in which 99 sheets were continuously passed in the same manner as described above. As a result, the amount of offset toner was
It was 0.12%, which proved that a greater effect could be obtained compared to 0.13% in the fourth example. In addition,
In this embodiment as well, as shown in FIG.
2b' and the conductive hole 82d', the service life of the static eliminating member 82 can be doubled. FIG. 9 is a front view showing the main parts of a seventh embodiment of the static eliminating member 82, which is a feature of the present invention. In addition to a large number of flexible needle-like charge eliminating members 82, other needle-like charge eliminating members 8 are provided on the conductive base 81 to eliminate charges in the area near the nip where the copy paper is peeled off.
3 were buried in large numbers. Static elimination member 83
Like the other static eliminating member 82, is made of flexible conductive fibers such as metal fibers or carbon fibers,
Or it is made of one or both sides coated with an insulating material. Then, the static eliminating member 83
The leading end of the copy paper is disposed near the nip portion where the copy paper is to be peeled off. Note that it is desirable that the static eliminators 82 and 83 have a wire diameter of 100 μm or less. Since the present embodiment has the above-described configuration, in addition to the static eliminating action by the static eliminating member 82 as shown in the previous embodiments, another static eliminating member 83 close to the copy paper peeling area near the nip portion performs the static eliminating action. An ionization phenomenon occurs, and the ion pairs generated in the vicinity provide a static elimination effect. Therefore, first, the charge eliminating member 83 quickly eliminates the charge that is separated from the copy paper and the pressure roller 2, and then the other charge eliminating member 82 removes the charge from the pressure roller 2 that has not been completely eliminated by the charge eliminating member 83. Further removes residual charges on the surface. Therefore, a very high static elimination effect can be obtained. Therefore, the effects thereof will be confirmed by showing specific experimental results using the static eliminating member 82 of the seventh embodiment shown in FIG. 9 and other static eliminating members 83.
The content of the experiment was to determine the amount of offset toner after continuously passing 99 sheets and after continuously passing 100,000 sheets, as in the case of the first embodiment. Static elimination member 82 used in this experiment
No. 83 and 83 have an insulating portion formed by coating one side of a conductive portion made of carbon fiber with a wire diameter of 5 μm with an epoxy resin having a thickness of 7 μm. Other conditions were the same as those of the experiments conducted in the first and fourth examples. The results are shown below. Table 1 shows the amount of offset toner after 99 sheets were continuously fed. The amount of offset toner was calculated using the following formula in the same way as in the first and fourth embodiments. Offset toner amount (%) = cleaning web 61
Amount of toner attached to (mg) / Amount of unfixed toner on plain paper 17 (mg) x 100 Furthermore, since the surface potential () of the pressure roller 2 is closely related to the amount of offset toner, Added to Table 1. Then, from Table 1, it can be seen that when 99 sheets are continuously fed, the amount of offset toner in the seventh embodiment is actually reduced to 1/8 or less compared to the case without the static eliminating member. Moreover, it is reduced to less than 1/2 compared to the first embodiment, and about 1/2 compared to the fourth embodiment, which shows that this embodiment has a remarkable static elimination ability. Next, the change in the amount of offset toner during continuous feeding of 100,000 sheets in the seventh embodiment is shown in FIG. 11 as a curve a-3. As is clear, this example maintains the amount of offset toner at 0.1% or less even after 100,000 sheets have been passed, and exhibits a much better performance than the conventional examples (curves b and c). Furthermore, even when compared with the first and fourth embodiments (curve a-1, curve a-2), it can be seen that the amount of offset toner is maintained at less than half, and an even more excellent effect is exhibited.
In other words, the reason why this embodiment exhibits the above-mentioned remarkable offset prevention effect is that, in addition to the charge eliminating member 82 used in the previous embodiments, it eliminates the charge in the copy paper peeling area near the nip. This is because another static eliminator 83 was used, and by performing double static elimination in this way, the static elimination action was further promoted and it became possible to prevent offset over a long period of time. In the above experiment of this embodiment, the contact position of the distal end of the static eliminating member 82 to the pressure roller was set from the nip portion to the rotation axis of the pressure roller 2 as the center of rotation.
Although it was decided to be 55 degrees downstream, as in the first and fourth embodiments, by bringing the tip of the static eliminating member 82 as close to the nip as possible, a higher static eliminating effect, that is, an offset prevention effect can be obtained. Of course you can. Further, as shown in FIG. 6 or 7, in the seventh embodiment, a large number of conductive holes 8 are provided in the static eliminating member 82.
By forming 2d and 82d', the offset prevention effect can be further enhanced. Further, as shown in FIG. 5 or FIG. 8, an even better effect can be obtained by exposing the conductive portion 82a without forming the insulating portion 82b in the vicinity of the tip 82c of the static eliminating member 82. be able to. FIG. 10 shows a static eliminating member 82 that is a feature of the present invention.
It is a front view which shows the principal part of 8th Example. In this embodiment, instead of the static eliminating member 83 in the seventh embodiment, a large number of fine conductive holes 82e are formed in the insulating part 82b of the static eliminating member 2 at the bent part or the part closest to the nip part. This effectively eliminates static electricity in the copy paper peeling area near the area where the copy paper has peeled off. By doing this, first, the conductive hole 82e quickly eliminates the electrical charge that separates the copy paper from the pressure roller 2, and then the tip of the charge eliminating member 82 removes the charge from the conductive hole 82e from which the pressure roller 2 has not been completely eliminated. Since the residual charge on the surface of 2 is further removed, a very high charge removal effect can be obtained.
Further, in this case, the position of the tip of the static eliminating member 82 can be brought closer to the nip side, and a more excellent static eliminating effect can be obtained. In each of the embodiments described above, the insulating portion 82b
Although epoxy resin and tetrafluoroethylene resin (hereinafter referred to as PTFE resin) have been mentioned as materials for forming the insulator, good results can be obtained with other materials as long as they have excellent insulating properties. For example, phenol resin, polyimide resin, polyamide resin, polyamideimide resin, PPS resin, PFA resin, acrylic resin, ABS resin, polyester resin, polyethylene resin, polystyrene resin, etc. can be used, and fillers such as glass can be used. It may be added. Of the above substances, epoxy resin, PTFE resin, phenol resin, polyimide resin, polyamide resin, polyamideimide resin,
Since PPS resin and PFA resin are heat resistant, they are suitable for heat fixing type fixing devices, but other materials are suitable for pressure fixing type fixing devices. Furthermore, as in the first to third embodiments, when the conductive part 82a is exposed only at the tip or the vicinity of the tip of the static eliminating member 82 and the other side surfaces are covered with the insulating part 82b, toner, paper powder, etc. An epoxy resin that easily collects dirt, that is, has poor mold releasability, is suitable, but as in the fourth to sixth embodiments, the insulating portion 82b
If a large number of fine conductive holes 82d are drilled in the conductive hole, it is easy to allow minute dirt to pass through.
In other words, PTFE resin, PFA resin, etc., which have excellent mold releasability, are desirable. When covering the above insulating material,
The thickness is preferably within 500μm, especially 50μm
Very good results can be obtained within Further, in each of the above embodiments, the conductive part 82a is coated with an insulating material to form the insulating part 82b, which is used as the static eliminating member 82.
It is not necessary that the conductive part 82a be integrated with the conductive part 82a, and an insulating film separate from the conductive part 82a can be used as the insulating part 82b.
Alternatively, this may be used in close contact with the conductive portion 82a. By doing this, the insulation part 82b
Even if the static elimination ability deteriorates due to contamination with toner, paper dust, etc., the insulating portion 82b is an insulating film separate from the conductive portion 82a, so replacing only the insulating portion 82b with a new one will improve the static eliminating ability. It is very convenient and economical to be able to take back the information. Further, the static eliminating member 82 does not necessarily have to be needle-shaped and flexible, and various shapes and materials are possible, but it is most preferable that it be needle-shaped and flexible. As described above, the present invention provides the static eliminating member 82
The tip of the conductive member is hardly contaminated by toner, paper dust, oil, etc., and therefore there is almost no deterioration of static elimination ability over time due to long-term use. Therefore, since the pressure roller 2 approaches a state of zero potential, the electrostatic repulsion with the toner image T on the surface of the recording material 17 disappears, and the recording material 17 is frictionally charged with the pressure roller 2. Since the charge with the opposite polarity to the charge on the toner on the back side increases, the electrostatic attraction of the toner image T to the recording material 17 increases, and as a result, offset of the toner image T toward the heating roller 1 side is extremely well prevented. can. Therefore, it has become possible to solve problems such as stains on copy paper caused by offset toner and poor fixing, and to maintain good fixing properties over a long period of time. As described above, the present invention provides wonderful effects that could not be obtained with the prior art.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram of one embodiment of the present invention, and FIG.
The figures are a schematic explanatory diagram of an electrophotographic apparatus using the embodiment shown in FIG. 1 of the present invention, FIG. 3, FIG. 4, FIG.
FIG. 6, FIG. 7, and FIG. 8 are enlarged cross-sectional views of main parts of first, second, third, fourth, fifth, and sixth embodiments of the static eliminating member that is a feature of the present invention, respectively. 9
Figures 1 and 10 are explanatory diagrams of main parts of seventh and eighth embodiments of the static eliminating member, which is a feature of the present invention, respectively.
FIG. 11 is a diagram showing the relationship between the amount of offset toner and the number of sheets passed according to the present invention. 1... Heat roller, 2... Pressure roller, 8... Static eliminator, 81... Conductive substrate, 82, 83... Static eliminator,
82a...Conductive part, 82b, 82b'...Insulating part, 82
c... Near the tip, 82d, 82d', 82e... conductive holes.

Claims (1)

[Claims] 1. In a fixing device including a pair of fixing rotors that nip and convey a recording material that supports an object to be fixed and fix it, and a charge eliminating means that eliminates charge from the surface of the fixing rotors, the charge remover is a grounded conductive member. and an insulating layer provided on the conductive member except for at least the leading edge of the conductive member on the side of the fixing rotor, and by bringing this insulating layer into contact with the fixing rotor, the leading edge of the conductive member and the fixing rotor are separated. A fixing device characterized by having minute gaps on its body surface.