JP2000286034A - Heating device, heat fixing device and image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the charging-up of a pressure roller in paper passing and the like, and the leakage of electric charge between a film and a pressing member by comprising a bias applying means for earthing the film and the pressing member or applying the predetermined bias thereto to obtain the predetermined bias, and determining a longitudinal length of the pressing member to be longer than a longitudinal length of the film. SOLUTION: As a pressure roller elastic layer is electrically conductive, the charging-up of the pressure roller 20 in paper passing is reduced, and the electric field for preventing the electrostatic offset is easily formed. By determining a longitudinal length L2 of the pressure roller 20 to be longer than a longitudinal length L1 of a film 13, the leakage of electric charge between a conductive rubber exposed part of an end surface of the pressure roller and a conductive primer layer 13b can be prevented, and the potential difference can be kept between the film 13 and the pressure roller 20. As the toner of an unfixed image formed on a member to be heated is negatively charged, the bias to be impressed is preferably -200 to -5 kV.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heater fixedly supported by a support member, a heat-resistant thin film (hereinafter abbreviated as "film") disposed so as to contact and move with the heater, and a film. A heating member for applying heat energy from the heater to a material to be heated, which moves a pressure contact portion between the film and the pressing member together with the film, and the heating device is applied. The present invention relates to a heat fixing device that heats and fixes an unfixed image on a material to be heated, and an image forming apparatus such as an electrophotographic method or an electrostatic recording method to which the heat fixing device is applied.

[0002]

2. Description of the Related Art As a conventional heating device of this type, a heating roller system or a film heating system is widely used. In particular, do not supply power to the heating device during standby,
The method of keeping the power consumption as low as possible, specifically, the heated material passed between the heater and the pressure roller as the pressure member,
A film heating device for heating through a film is disclosed in
JP-A-3-313182 / JP-A-2-15778 / JP-A-4-44075 / JP-A-4-2049
No. 80 has been proposed.

FIG. 6 is a schematic diagram showing a main part of a film heating device applied as a heat fixing device. In FIG. 6, a heating member (heating body, heating member, fixedly supported by a stay holder (supporting member) 12 is shown. Hereinafter, a nip portion (fixing nip portion) having a predetermined nip width is caused by pressing a heat-resistant thin film (hereinafter, referred to as a film) 13 disposed outside the heater 11 and a heat-resistant thin film 13 (hereinafter, referred to as a film). And a pressure roller 20 as a pressure member for forming N.

The pressure roller 20 is driven in a direction indicated by an arrow by means not shown. The nip portion N is fixed to the unfixed image t.
The unfixed image t is heated and fixed to the paper P by passing the heated material P such as paper having A thermistor 14 is provided on the back of the heater 11 to detect the temperature of the heater. An energizing circuit (not shown) for the heater 11 is provided based on the temperature information so that the heater 11 has a constant temperature.
Control.

The pressure roller 20 comprises an elastic layer 21 formed by foaming heat-resistant rubber such as silicon rubber or fluorine rubber or silicon rubber on the outside of a cored bar. PFA, PTFE is formed on the elastic layer 21. , Or a release layer such as FEP.

The film 13 has a small heat capacity, heat resistance,
Polyimide, polyamideite, PEE with thermoplasticity
K, PES, PPS, PFA, PTFE, FEP and other fixing films. Further, in order to prevent offset and ensure the separation of the recording material, PFA, PTFE, F
A heat-resistant resin having good release properties such as EP is mixed or coated alone.

The stay holder 12 holds the heater 11,
A heat-insulating support member for preventing heat radiation in the direction opposite to the nip portion N, such as a liquid crystal polymer, phenol resin, PPS,
It is formed by EEK or the like. And film 1
3 has such a shape and size as to be able to rotate with a margin in the direction of the arrow, so that it is necessary to reduce the frictional resistance between the film 11 and the heater 11 and the stay holder 12.
Therefore, a small amount of a lubricant such as heat-resistant grease is interposed between the surfaces of the heater 11 and the stay holder 12. This allows the film 13 to rotate smoothly.

The film 13 is conveyed and moved in the direction of arrow a while being in close contact with and sliding on the surface of the heater 11 at the nip portion N by the driving means (not shown) or the rotational force of the pressure roller 20. Or a rolled ended web-shaped member. When the heater 11 is heated and controlled to a predetermined temperature, and the film 13 is conveyed and moved in the direction of the arrow, when the heated material P is introduced between the film 13 of the nip portion N and the pressure roller 20, The material P to be heated is brought into close contact with the surface of the film 13 and is conveyed by nipping the nip N with the film 13.

In the nip portion N, the material to be heated P is heated by the heater 11 via the film 13. The material P to be heated having passed through the nip N is peeled off from the surface of the film 13 and transported.

Generally, a ceramic heater is used for the heater 11. For example, the surface of the ceramic substrate 11a (the surface facing the film 13) having electrical insulation, good thermal conductivity, and low heat capacity such as alumina is coated with silver particles along the length of the substrate (perpendicular to the drawing). Ag / Pd) ・ Ta2N
Is formed by screen printing or the like, and the surface on which the heating resistor layer is formed is covered with a thin glass protective layer 11c.

In the ceramic heater 11, when a current is applied to the current-carrying resistance layer 11b, the current-carrying resistance layer generates heat and the ceramic substrate 11a and the glass protective layer 1b are heated.
The temperature of the entire heater 1c rapidly rises. The temperature rise of the heater 11 is detected by the temperature detecting means 14 disposed on the back surface of the heater 11, and is fed back to a power supply control unit (not shown). The energization control unit controls energization of the energization heating resistance layer 11b so that the heater temperature detected by the temperature detection means 14 is maintained at a predetermined substantially constant temperature (fixing temperature). That is, the heater 11 is heated and adjusted to a predetermined fixing temperature. The film 13 has a thickness of 20 to 7 in order to efficiently apply the heat of the heater 11 to the material to be heated P in the nip portion N.
It is as thin as 0 μm.

FIGS. 7A and 7B are diagrams showing a method of grounding the film 13, wherein FIG. 7A is a front view showing the relationship between the film 13 and the pressure roller 20, and FIG. 7B is an enlarged perspective view of a part of the film 13. . The film 13 has a three-layer structure of a film base layer 13a, a primer layer 13b, and a release layer 13c. The film base layer 13a side is the heater side, and the release layer 13c side is the pressure roller side. The film base layer 13a is made of polyimide, polyamideimide, PEEK, or the like having higher insulation than the glass protective layer 11c of the heater 11, and has heat resistance and high elasticity. The film base layer 13
By a, the mechanical strength such as the tear strength of the entire film 13 is maintained.

The primer layer 13b is a low-resistance layer in which carbon is dispersed, and has a thickness of about 2 to 6 μm. The primer layer 13b is provided to prevent electrostatic offset due to frictional charging (due to sliding rotation) of the film base layer 13a.
As shown in FIG. 7A, at the end of the non-sheet passing area, the pressure roller core metal 21 is connected to the ground E via a conductive rubber ring 24 at the end of the pressure roller 20.

The releasable layer 13c is a layer for preventing toner offset from the film 13, and includes PFA, PTFE, and FE.
It is formed by covering with a thickness of about 10 μm using a fluorine resin such as P. Further, in order to prevent charge-up due to paper passing and offset due to leakage of the transfer current of the material to be heated, a conductive material such as carbon is dispersed in a predetermined amount to control the resistance value.

[0015]

However, in recent years, a film heating and fixing device to which a heating device is applied has been adopted for a medium-to-high-speed machine, and the electrostatic offset and tailing have deteriorated. Tail measures have become necessary. For this purpose, a predetermined bias is individually applied to the film and the pressure roller, and the toner as an unfixed image is applied to the vicinity of the nip, as in the case of the heat roller method which has been conventionally used in a medium-speed machine. An effective method is to form an electric field in the direction of pressing on paper.

Further, in order to prevent charge-up of the pressure roller due to paper passing, it is effective to disperse carbon or the like in the elastic layer 22 of the pressure roller and to make the elastic layer conductive, so that electrostatic offset and tailing are effective.

However, it is difficult to make the pressure roller release layer conductive because the toner release property is lowered. In this case, there is a problem that electric charge leaks between the exposed portion of the conductive rubber on the end surface of the pressure roller and the end portion of the film or the surface layer, and a potential difference for preventing electrostatic offset and tailing cannot be maintained.

[0018]

According to the present invention, there is provided a heating device, a heat fixing device, and an image forming apparatus having the following structures.

(1) A heater fixedly supported by a support member, a heat-resistant film disposed so as to be in contact with the heater, and a pressurizing member for pressing the film against the heater. In a heating device for applying heat energy from the heater to a material to be heated, which moves a pressure contact portion between a film and a pressing member together with the film, the film and the pressing member may be grounded or grounded so that each has a predetermined bias. A heating device, comprising: bias applying means for applying a predetermined bias, wherein a longitudinal length of the pressing member is longer than a longitudinal length of the film.

(2) The heating apparatus according to claim 1, wherein a cleaning member is provided at a bias applying contact of the film.

(3) The heating device according to claim 1, wherein a cleaning member is provided at a position on the pressure roller side corresponding to the bias application contact point of the film.

(4) In a heat fixing device for heating a material to be heated having an unfixed image and heating and fixing the unfixed image to the material to be heated, the heating device for heating the material to be heated is preferably used. A heating fixing device comprising the heating device according to claim 3.

(5) An image forming means for forming and carrying an unfixed image on the material to be heated, and a heat fixing means for heating and fixing the unfixed image formed and carried on the material to be heated to the material to be heated. An image forming apparatus, wherein the heat fixing unit is the heat fixing device according to claim 4.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below.

Embodiment 1 FIG. 1 shows a configuration diagram of a heat fixing device 6 according to the present invention.
FIG. 7B shows a fixing film having a small heat capacity.
As shown in the figure, the substrate comprises a base layer 13a, a conductive primer layer 13b, and a release layer 13c. The base layer 13a is made of a heat-resistant, thermoplastic polyimide, polyamideimide, PEE having a thickness of 100 μm or less to enable quick start.
K, PES, PPS, PFA, PTFE, FEP and the like.

Further, a film having sufficient strength to constitute a long-life heat fixing device and having excellent durability must have a thickness of 20 μm or more. Therefore, the thickness of the film 13 is optimally 20 μm or more and 100 μm or less. The release layer 13c is made of a heat-resistant resin having good releasability such as PFA, PTT, FEP, or the like, and is coated on the surface layer 13a alone or in order to prevent offset and ensure the separation of the material to be heated. The conductive primer layer 13b is used to bond the base layer 13a and the release layer 13c and apply a predetermined bias to the film 13, so that the exposed portion of the end 13b of the conductive primer layer in the non-sheet passing area is contacted as shown in FIG. 13b-1 as SUS as a bias applying means to the contact portion 13b-1.
And the like, and a predetermined bias is applied by a diode 45 or a high voltage power supply or the like.

In the first embodiment, since the toner as an unfixed image formed on the material to be heated is negatively charged, an appropriate bias to be applied is about 200 V to 15 kV.

Reference numeral 11 denotes a heater (heating heater) provided inside the film 13, and the thermal energy from the heater 11 melts and fixes the toner image on the material to be heated passing through the nip. Reference numeral 12 denotes a heat insulating stay holder for holding the heater 11 and preventing heat radiation in a direction opposite to the nip portion, and includes a liquid crystal polymer, a phenol resin, PPS, and PEE.
The film 13 is loosely fitted outside with a margin, and is arranged rotatably in the direction of the arrow.

Further, since the film 13 rotates while rubbing against the internal heater 11 and the heat insulating stay holder 12, it is necessary to reduce the frictional resistance between the film 11 and the heater 11 and the heat insulating stay holder 12. Therefore, a small amount of a lubricant such as heat-resistant grease is interposed between the surfaces of the heater 11 and the heat insulating stay holder 12. This allows the film 13 to rotate smoothly. Then, the heater 11, the heat insulating stay holder 12,
The film 13 constitutes the fixing member 10.

The pressing member 20 comprises an elastic layer 22 formed by foaming heat-resistant rubber such as silicon rubber or fluorine rubber or silicone rubber on the outside of a cored bar 21.
A release layer 23 made of FA, PTFE, FEP or the like is formed. Further, a bias of about 200 V to 5 kV is applied to the pressure roller core 21 via a diode 45 or a high voltage power supply.

The pressing member 20 is sufficiently pressed in the direction of the fixing member 10 from both ends in the longitudinal direction by a pressing means (not shown) to form a nip portion necessary for heat fixing. The portion is driven to rotate in the direction of the arrow by a drive source (not shown) via a metal core 21. As a result, the film 13 is driven to rotate outside the heat insulating stay holder 12 in the direction indicated by the arrow in FIG.

The process speed of the first embodiment is 94 mm / s, the throughput is 16 ppm (A4), the carbon is dispersed in the elastic layer 22 of the pressure roller to make it conductive, and as shown in FIG. The longitudinal length L2 of the pressure roller 20 is longer than the longitudinal length L1.

In this configuration, since the pressure roller elastic layer 22 is conductive, there is little charge-up of the pressure roller 20 due to paper passing, and an electric field for preventing electrostatic offset is easily formed. Further, by making the longitudinal length L2 of the pressure roller 20 longer than the longitudinal length L1 of the film 13, the conductive rubber exposed portion on the end surface of the pressure roller and the conductive primer layer 13b are formed.
(From the end face and the surface of the film 13), and the potential difference between the film 13 and the pressure roller 20 can be maintained.

Table 1 compares the electrostatic offset of the configuration shown in the conventional example (see FIG. 7) with the configuration of the first embodiment in three environments (L / L, N / N, H / H). The result.

Since the electrostatic offset tends to be deteriorated by paper passing (due to a decrease in the releasability due to scratches on the film release layer 11c), the evaluation of the electrostatic offset after 100,000 sheets are passed. I also went.

[0036]

[Table 1]

As can be seen from Table 1, in the conventional configuration, the film 13 and the pressure roller 20 tend to be charged up in an L / L environment, and the releasability of the film release layer 11c is reduced. However, it can be seen that in the configuration of the first embodiment, the electrostatic offset is stably improved irrespective of the use environment and the number of durable sheets.

Even if the elastic layer 22 of the pressure roller 20 is made conductive, the longitudinal length L1 of the film 13> the pressure roller 20
In the case of the longitudinal length L2, since a charge leak occurs between the exposed portion of the conductive rubber on the end surface of the pressing roller and the film end or the surface layer, the potential difference between the film 13 and the pressing roller 20 may be maintained. It is not possible to prevent electrostatic offset.

Next, a tailing comparison of the H / H environment was performed with the above two configurations. Table 2 shows the results.

[0040]

[Table 2]

As can be seen from Table 2, the configuration of the first embodiment makes it possible to suppress the occurrence of tailing to a slight level even in a high-temperature, high-humidity environment where tailing is likely to occur.

As described above, the elastic layer 2 of the pressure roller 20
2 is made conductive and the longitudinal length is made longer than the longitudinal length of the film 13, so that electrostatic offset and tailing deterioration due to charge-up of the pressure roller 20 due to paper passing can be prevented. And a good image can be stably obtained.

Embodiment 2 In the configuration of the first embodiment, the contact 13-b between the conductive brush 41 and the film 13 for applying a bias (the contact portion that is an exposed portion of the conductive primer layer 13 b) is in contact with the pressure roller 20. Therefore, it was found that dirt (paper powder, toner powder, sliding grease, etc.) adhered to the contact portion 13b-1 due to a large amount of paper passing, and was not suitable for extending the life.

Therefore, in the second embodiment, as shown in FIG. 3, the contact portion 1 of the film 13 with which the conductive brush 41 contacts.
The cleaning member 3b-1 is provided.
As the cleaning member 43, a heat-resistant felt was used. The other conditions are the same as those in the first embodiment, and therefore, the same portions are denoted by the same reference numerals and overlapping description will be omitted.

As in the second embodiment, the film 13
By providing the cleaning member 43 at the contact portion 13b-1, it is possible to prevent contact failure due to dirt such as paper dust, toner dust, and sliding grease, which increase as paper is passed. Table 3 shows whether or not the cleaning member 43 is provided.
It is a result of examining a change due to paper passing of the electrostatic offset level in the L environment.

[0046]

[Table 3]

As can be seen from Table 3, this configuration allows
It can be seen that the electrostatic offset can be prevented until the completion of passing of 100,000 sheets, and the durability performance is greatly improved. It was also confirmed that the effect of improving the tailing can be obtained up to the completion of 200,000 sheet feeding as in the case of the electrostatic offset. By providing the cleaning member 43 at the contact portion of the film 13 as described above, it is possible to prevent the electrostatic offset and the tailing from being deteriorated due to the contamination of the contact portion 13b-1, and the electrostatic offset can be prevented regardless of the number of sheets passed. And a good image without tailing can be obtained.

Embodiment 3 In the third embodiment, as shown in FIG. 4, a cleaning member 44 is provided at a position on the pressing roller side corresponding to the contact point 13-b of the film 13, and the cleaning member 44 includes a heat-resistant felt. It was used. The other conditions are the same as those in the first embodiment, and therefore, the same portions are denoted by the same reference numerals and overlapping description will be omitted.

As described above, the cleaning member 44
Is brought into contact with the pressure roller 20 so that the film 13
The contact portion 13b-1 can be cleaned without damaging the contact portion 13b-1. Table 4 shows the results of comparing the electrostatic offset levels with and without the cleaning member 44.

[0050]

[Table 4]

As can be seen from Table 4, as in the second embodiment, even after 200,000 sheets have passed, the deterioration of the electrostatic offset due to the defective contact is not observed, and a good image can be obtained.
Also, with respect to the tailing, an improvement effect was similarly obtained after passing 200,000 sheets.

Next, the cleaning member 4 is applied to the film 13.
3 and a durability test of the film 13 when the cleaning member 44 was in contact with the pressure roller 20. Table 5 shows the results.

[0053]

[Table 5]

As can be seen from Table 5, by bringing the cleaning member 44 into contact with the pressure roller, the film 1
3 can be greatly reduced.

As described above, the contact portion 13 of the film 13
By providing the cleaning member 44 at a position on the pressure roller 20 side corresponding to b-1, the reliability of the contact portion of the film 13 can be ensured without damaging the film 13, and the electrostatic offset and tail can be reduced. Good heating without pulling can be obtained.

Embodiment 4 FIG. 5 is a configuration diagram of the image forming apparatus according to the present invention. In FIG. 1, reference numeral 1 denotes a photosensitive drum on which a photosensitive material such as 0PC, amorphous Se, amorphous Si or the like is formed on a cylindrical substrate such as aluminum or nickel. The photosensitive drum 1 is driven to rotate in the direction of the arrow, and its surface is first uniformly charged by a charging roller 2 as a charging device.

Next, scanning exposure is performed with the laser beam 3 controlled to 0 N / OFF according to the image information, and an electrostatic latent image is formed. This electrostatic latent image is developed by the developing device 4,
Be visualized. As a developing method, a jumping developing method, a two-component developing method, an FEED developing method, or the like is used, and a combination of image exposure and reversal developing is often used.

The visualized toner image t is transferred from the photosensitive drum 1 onto the heated material P conveyed at a predetermined timing by the transfer roller 5 as a transfer device. At this time, the material to be heated P is nipped and conveyed by a constant pressing force between the photosensitive drum 1 and the transfer roller 5. The heated material P to which the toner image t has been transferred is conveyed to the heat fixing device 6 described in any of the first to third embodiments, and passes through the heat fixing device 6 to become permanent. The image is fixed by heating. On the other hand, the transfer residual toner remaining on the photosensitive drum 1 is removed from the surface of the photosensitive drum 1 by the cleaning device 7.

[0059]

As described above, according to the present invention, according to the present invention, a heater fixedly supported by a support member, a heat-resistant film disposed so as to be in contact with and moved to the heater, and the film attached to the heater A heating member having a pressure member for pressing, and applying a heat energy from the heater to a material to be heated which moves a pressure contact portion between the film and the pressure member together with the film; ,
A bias applying means for applying a predetermined bias to the ground or a predetermined bias is provided so as to have a predetermined bias, and the longitudinal length of the pressing member is configured to be longer than the longitudinal length of the film. It is possible to prevent charge-up between the film and the pressing member, and to stably prevent electrostatic offset and tailing regardless of the use environment.

Further, since the cleaning member is provided at the bias applying contact point of the film, it is possible to prevent the contact failure due to the contamination of the contact point due to the endurance of the paper passing, and to prolong the service life of the electrostatic offset and the tailing prevention effect. There is a peeling effect.

Further, since the cleaning member is provided at a position on the pressure roller side corresponding to the bias application contact of the film, the reliability of the contact portion with the film can be secured without damaging the film. Thus, there is an effect that the electrostatic offset and the tailing can be stably improved.

Further, by applying the heating device of the present invention, there is an effect that the heat fixing can be reliably performed with less trouble and the durability can be excellently obtained.

Further, by applying this heat fixing device, there is an effect that an image forming device capable of forming a high quality image by a smooth fixing operation can be obtained.

[Brief description of the drawings]

FIG. 1 is an end view showing a heat fixing device to which a heating device according to a first embodiment of the present invention is applied;

FIG. 2 is a front view of the device.

FIG. 3 is an end view showing a heat fixing device to which a heating device according to a second embodiment of the present invention is applied;

FIG. 4 is an end view showing a heat fixing device to which a heating device according to a third embodiment of the present invention is applied.

FIG. 5 is a configuration diagram of an image forming apparatus according to a fourth embodiment of the present invention.

FIG. 6 is a partial end view showing a conventional heat fixing device.

7A and 7B are diagrams showing a film grounding method in a conventional heat fixing device, wherein FIG. 7A is a front view and FIG. 7B is an enlarged view of a part thereof.

[Explanation of symbols]

11 heating member (heater), 12 heat insulating stay holder (support member), 13 film (thin film), 13b
-1 film contact point, 20 pressure roller (pressure member), 41 conductive brush (bias applying means), 4
3, 44 Cleaning member.

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masami Takeda 3-30-2 Shimomaruko, Ota-ku, Tokyo F-term (reference) in Canon Inc. 2H033 AA42 BA13 BB30 BE03 3K058 AA45 BA18 DA05

Claims (5)

[Claims] 1. A film fixedly supported by a support member, a heat-resistant film disposed so as to be in contact with the heater, and a pressing member for pressing the film against the heater. In a heating device for applying heat energy from the heater to a material to be heated, which moves a pressure contact portion between the film and the pressing member together with the film, the film and the pressing member are grounded or fixed so that each has a predetermined bias. And a bias applying means for applying the bias of (1), wherein the longitudinal length of the pressing member is longer than the longitudinal length of the film. 2. The heating apparatus according to claim 1, wherein a cleaning member is provided at a bias application contact of said film. 3. The heating device according to claim 1, wherein a cleaning member is provided at a position on the pressure roller side corresponding to the bias application contact point of the film. 4. A heating and fixing device for heating a material to be heated having an unfixed image and heating and fixing the unfixed image to the material to be heated, wherein the heating device heats the material to be heated. Item 4. A heating fixing device comprising the heating device according to any one of Items 3. 5. An image forming apparatus comprising: an image forming means for forming and supporting an unfixed image on a material to be heated; and a heat fixing means for heating and fixing the unfixed image formed and supported on the material to be heated to the material to be heated. 5. An image forming apparatus, wherein the heat fixing unit is the heat fixing device according to claim 4.