JP2002236425A - Fixing device and image forming apparatus equipped therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fixing device capable of realizing the shortening of a start-up time and realizing the reduction of standby power at the time of standing by while maintaining high fixing speed in an image forming apparatus, especially, a rotary developing type color image forming apparatus. SOLUTION: This fixing device is equipped with a 1st fixing part N1 formed by bringing a 1st heating means 10 having no elastic layer on its surface into press-contact with a roller 5 having an elastic layer 7 on its surface and driven to be normally and reversely rotated, a 2nd fixing part N2 formed by bringing a 2nd heating means 20 having no elastic layer on its surface into press-contact with the roller 5 at a position nearly opposed to the heating means 10, and a feeding path switching means for selectively switching the feeding path of material to be heated so as to guide the material to be heated to the 1st or the 2nd fixing parts. By heating the material to be heated on either surface of which can unfixed toner image is carried while holding and feeding it at the 1st fixing part or the 2nd fixing part, the unfixed toner image is fixed on the material to be heated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for heating and fixing an unfixed toner image formed and carried on a material to be heated.

[0002] The present invention also relates to an image forming apparatus provided with the fixing device. More specifically, the material to be heated (recording material: transfer material (plain paper, cardboard, etc.)) by a transfer method or a direct method by any image forming process means such as an electrophotographic method, an electrostatic recording method, and a magnetic recording method. , Photosensitive paper, electrostatic recording paper,
An unfixed monochrome toner image (single color toner image) or color toner image corresponding to the image information is formed and supported on an OHP sheet, and the material to be heated is introduced into a fixing device to heat and fix the unfixed toner image. The present invention relates to an image forming apparatus such as a copying machine and a laser beam printer.

[0003]

2. Description of the Related Art A color image forming apparatus can execute a color (full color) image printing and a monochrome image (single color image) printing by selecting a mode. Even if the transport speed of the material is constant, the time required for printing per sheet is longer in color image printing than in monochrome image printing.

More specifically, in a color image forming apparatus of a rotary developing system using four developing devices each containing a yellow toner, a magenta toner, a cyan toner, and a black toner, the number of prints of a monochrome image per minute is, for example, 16
The number of color image prints is about one-fourth, ie, about four.

Therefore, a fixing device mounted on such a color image forming apparatus needs to be able to obtain sufficient fixability at a printing speed of 4 sheets per minute or 16 sheets per minute. ing.

As an example of such a fixing device, there is a heat roller type fixing device 106 as shown in FIG.

The fixing device 106 includes a nip portion N between a fixing roller 120 and a pressure roller 130 which rotate while being pressed against each other.
The sheet S carrying the unfixed toner image T is introduced and nipped and conveyed, so that the unfixed toner image T is fixed on the surface of the sheet S by heat and pressure.

The fixing roller 120 has an elastic layer 123 made of silicon rubber or the like on the outer periphery of a core metal 122 made of aluminum or the like, and further has a release layer 124 made of a fluororesin such as PFA / PTFE on the surface of the elastic layer 123. It is configured by providing a heater 121 as a heat source inside the cored bar 122.

Similarly, the pressure roller 130 has a heater 131 inside, and is composed of a metal core 132, an elastic layer 133, and a release layer 134, and is pressed against the fixing roller 120 by pressure means (not shown). It rotates while forming a nip N between itself and the fixing roller 120.

The fixing roller 120 and the pressure roller 1
A thermistor 12 as a temperature detector is provided on each surface of 30.
5 and 135 are brought into contact with each other, and based on the detected roller surface temperature, the fixing roller 1 is controlled by a heater driving circuit (not shown) so that each roller surface temperature becomes the temperature control target temperature.
The temperature control of each of the pressure roller 20 and the pressure roller 130 is controlled.

After the surface temperatures of the fixing roller 120 and the pressure roller 130 reach the target temperature, the sheet S on which the unfixed toner image T has been transferred is conveyed to the nip N of the fixing device 106 and In the process of nipping and transporting the nip N, the unfixed toner image T
Is fixed on the surface by heat and pressure.

According to this fixing device, the fixing roller 12
0, since both the pressure roller 130 and the pressure roller 130 have the heat sources 121 and 131, the temperature can be controlled independently of each other. Even if it is performed, it is possible to supply a suitable amount of heat.

One of the necessary conditions for the fixing device of the color image forming apparatus is that an elastic layer 123 is provided on the fixing roller 120 as in the above fixing device example. This is because, in the case of a fixing roller having no elastic layer 123, that is, a fixing roller having a hard surface, the fixing roller surface comes into contact with irregularities on the surface of the toner image at points, resulting in uneven gloss due to a partial difference in fixing property. In particular, the gloss unevenness is conspicuous in a color image. As a measure for preventing the gloss unevenness, the elasticity of the surface of the fixing roller 120 is reduced by providing an elastic layer 123 on the fixing roller 120, so that the surface of the fixing roller wraps around the unevenness of the toner image.

[0014]

By configuring the fixing device as described above, a fixing speed corresponding to a color image forming apparatus which has been increasing in speed recently has been achieved.

However, in the fixing device 106 shown in the conventional example, the fixing roller 120 and the pressure roller 130
However, the heat transfer from the inside by the heater inside the roller and the low thermal conductivity of the elastic layer cause the core metal temperature to be several tens degrees Celsius higher than the roller surface temperature.
Generally, this temperature difference depends on the thickness of the elastic layer, and the thicker the elastic layer, the larger the temperature difference. Therefore, if the temperature of the roller surface is increased with an increase in the fixing speed, the core metal temperature will also increase, and the rubber at the interface between the elastic layer and the core metal will be thermally degraded and the rubber will be peeled off. The durability is significantly reduced. Therefore, in order to lower the temperature of the interface between the elastic layer and the core metal to a temperature at which thermal deterioration of the rubber does not occur,
It is necessary to reduce the thickness of the elastic layer.

However, when the thickness of the elastic layer is reduced, the nip width is reduced, and in order to secure a predetermined nip width, the diameter of the fixing roller must be increased. As a result, the heat capacity of the roller itself increases. The time required to raise the surface of the roller to the temperature required for fixing has increased. Also, after the power of the apparatus main body is turned on, the roller temperature must always be maintained at a high temperature so that the next printing can be performed quickly, and the power consumption during standby is increasing.

According to the present invention, there is provided a fixing device capable of realizing a shortened start-up time and a reduced standby power during standby while maintaining a high fixing speed in an image forming apparatus, especially a color image forming apparatus of a rotary developing system. The purpose is to provide.

[0018]

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

(1) A first heating means having an elastic layer on its surface and being pressed by a first heating means having no elastic layer on its surface is pressed against a rotating body driven to rotate forward and reverse. A fixing unit, a second fixing unit formed by pressing a second heating unit having no elastic layer on the surface against the rotating body, and the first fixing unit or the second fixing unit. Transport path switching means for selectively switching the transport path of the material to be heated so as to guide the material to be heated to the fixing section of the first fixing section or the second fixing section. A fixing device for fixing an unfixed toner image to a material to be heated by heating the material to be heated carrying the image while nipping and transporting the material.

(2) The fixing device according to (1), wherein the first heating means and the second heating means are arranged at positions substantially facing each other with respect to the rotating body.

(3) At least one of the first heating means and the second heating means is composed of at least a fixed heating element and a film whose inner surface is pressed against the heating element and is slidable. The fixing device according to (1) or (2), wherein:

(4) The fixing device according to (3), wherein the heating element is a ceramic heater or an electromagnetic induction heating member.

(5) At least one of the first heating means and the second heating means has at least a fixed support, and an electromagnetically induced heat slidably movable with its inner surface opposed to and pressed against the support. (1) The fixing device according to (1) or (2), wherein the film has heat, and the film entirely or at least partially generates heat by the action of the magnetic field of the magnetic field generating means.

(6) At least one of the first heating means and the second heating means is a rotating body made of a pipe-shaped metal and having a heating lamp as a heating means therein. The fixing device according to (1) or (2).

(7) In the single-color fixing mode, the material to be heated is guided to the first fixing section for fixing, and in the full-color fixing mode, the material to be heated is guided to the second fixing section for fixing. The fixing device according to any one of (1) to (6).

(8) In a fixing device capable of setting a plurality of stages of fixing and conveying speeds, a heating target material is guided to the first fixing section for fixing at a high speed side, and the second fixing section is fixed at a low speed side. The fixing device according to any one of (1) to (7), wherein the material to be heated is guided to fix the material.

(9) An image forming apparatus comprising: an image forming means for forming a toner image of a single color or a plurality of colors on a material to be heated; and a fixing device for fixing the toner image on the material to be heated. The image forming apparatus is the fixing device according to any one of (1) to (8).

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [First Embodiment] An embodiment of the present invention will be described below with reference to the accompanying drawings.

(A) Color Image Forming Apparatus FIG. 1 shows a color image forming apparatus 100 provided with a fixing device 1 of the present invention. The color image forming apparatus 100 is of a rotary developing system, and is set at a printing speed of up to 16 sheets per minute for monochrome image printing and up to 4 sheets per minute for color image printing.

Reference numeral 101 denotes a photosensitive drum as an image carrier. The photosensitive drum 101 is driven in a direction indicated by an arrow by a driving unit (not shown), and is uniformly charged by a primary charger 102. Reference numeral 103 denotes an exposure device (laser scanner). The laser scanning exposure L according to the yellow component color image pattern of the full-color image is performed by the exposure device 103 on the photosensitive drum 10.
1 and a latent image is formed on the photosensitive drum 101. Further, when the photosensitive drum 101 moves in the direction of the arrow, the developing devices 104a, 1
04b, 104c, and 104d, the developing rotary 111 rotates so that the developing device 104a containing the yellow toner faces the photosensitive drum 101.
The latent image on the photosensitive drum 101 is visualized by a.
The developing devices 104b, 104c, and 104d are developing devices containing magenta toner, cyan toner, and black toner, respectively.

Reference numeral 105 denotes an intermediate transfer belt. The intermediate transfer belt 105 rotates in the direction of the arrow at substantially the same speed as the photosensitive drum 101, and the toner image formed and carried on the photosensitive drum 101 is rotated by a primary transfer bias applied to a primary transfer roller 108a. The primary transfer is performed on the outer peripheral surface of the reference numeral 105. On the other hand, the transfer residual toner on the photosensitive drum 101 is cleaned by the cleaning device 107 of the blade unit.

The toner image forming process for the photosensitive drum 101 and the primary transfer process for the intermediate transfer belt 105 are performed on the magenta component color image pattern, the cyan component color image pattern, and the black component color image pattern of the full-color image in the same manner as described above. Accordingly, a composite color toner image is formed on the intermediate transfer belt 105 by superimposing toner images of a plurality of colors (yellow, magenta, cyan, and black).

Next, the sheet S is fed from the sheet cassette 112 by the pickup roller 113 at a predetermined timing, and is introduced into a secondary transfer nip portion which is a press contact portion between the secondary transfer roller 108b and the intermediate transfer belt 105. At the same time, a secondary transfer bias is applied to the secondary transfer roller 108b, and the composite color toner image is collectively transferred from the intermediate transfer belt 105 to the sheet S.

Further, the sheet S is conveyed to the fixing device 1 by the conveyance belt 114, receives the fusion and fixation of the toner image, and is discharged as a color print (color copy) to a discharge section outside the apparatus.

The transfer residual toner on the intermediate transfer belt 105 is charged by an intermediate transfer cleaning roller 115, is reversely transferred onto the photosensitive drum 101 at the next primary transfer, and is cleaned by the cleaning device 107.
It is cleaned and removed from above.

In the case of monochrome image printing, a latent image is formed on the photosensitive drum 101, and a toner image is carried on the photosensitive drum 101 by a developing unit 104d containing black toner, as in the case of forming a color image. Belt 1
The primary transfer is performed on the area 05. Then, only the single-color toner image formed here is secondarily transferred to the sheet S, and similarly fixed by the fixing device 1, whereby a black single-color image is obtained. That is, the time required until all the images are formed on the intermediate transfer belt 105 is reduced to about one-fourth that of the color image.

(B) Fixing Device FIGS. 2 and 3 show the fixing device 1. Reference numeral 5 denotes a roller having an elastic layer on the surface. Both ends of the roller 5 are rotatably supported, and a heater unit 10 as a first heating unit and a heater unit 20 as a second heating unit are arranged above and below the roller 5 at positions facing each other. I have. The roller 5 has an elastic layer 7 of silicon rubber provided on a metal core 6 of aluminum, and a release layer 8 of a thin film made of PFA or the like provided on the elastic layer 7 to have a small outer diameter of about 20 mm. And is rotatably supported in both forward and reverse directions by a drive motor (not shown).

The heater unit 10 has an outer diameter of about 24 mm.
, A ceramic heater 12 attached to a film guide 11, a film 13 and a thermistor 14. The ceramic heater 12 has a conductive heating layer provided on the roller 5 side surface of a ceramic substrate made of alumina or the like, and an insulating layer of heat-resistant glass provided thereon. A thermistor 14 for detecting the heater temperature is provided on the side of the ceramic heater 12 opposite to the heat generating layer, and the heater temperature is adjusted based on the detection signal. The film 13 slidably provided around the film guide 11 forms a release layer such as a fluororesin on the surface of an endless heat-resistant film made of a thin polyimide resin or the like to prevent adhesion of toner and the like. are doing.

The heater unit 20 is obtained by turning the heater unit 10 upside down.
0, film guide 21, ceramic heater 2
2 and a film 23 and a thermistor 24.

The heater unit 10 and the heater unit 20 are vertically pressed by a biasing means (not shown) with a predetermined pressing force with the roller 5 interposed therebetween. A nip Nl and a nip N2 serving as a second fixing unit are formed.

On the upstream side of the roller 5 in the sheet passing direction, an entrance guide 70 serving as a conveyance path switching means is supported so as to be able to swing by a predetermined amount about a rotation shaft 71 as a fulcrum. By displacing the front end of the entrance guide 70, the sheet S on which an image has been formed can be selectively guided to the nip Nl as the first fixing unit or the nip N2 as the second fixing unit. The switching of the entrance guide 70 and the rotational driving of the roller 5 are controlled in conjunction with each other. When the entrance guide 70 guides the sheet S to the nip Nl as shown in FIG. 2, the roller 5 is driven in the direction of the arrow R1. Following this, the films 13 and 23 of the heater units 10 and 20 are also configured to slide and rotate around the film guides 11 and 21 in the directions of the arrows, respectively.

Similarly, when the entrance guide 70 guides the sheet S to the nip N2 as shown in FIG. 3, the roller 5 rotates in the reverse direction and is driven in the direction of the arrow R2. Sliding rotation in the direction.

On the downstream side of the roller 5, the sheet S fixed at the nip Nl or the nip N2 is discharged.
Guides 72 and 7 are provided so as to smoothly guide in five directions.
3, 74 are provided. When the color image forming apparatus receives a print signal of a monochrome image, the roller 5
At the same time, the entrance guide 70 is switched to guide the sheet S in the nip Nl direction. Also,
The energization of the ceramic heaters 12 and 22 is started,
The roller 5 is quickly heated through the films 13 and 23 to a temperature required for monochrome printing.

The unfixed toner image side of the sheet S on which the monochrome image guided to the nip Nl is formed
3. The rear surface is nipped and conveyed by the roller 5 to perform fixing.

When the color image forming apparatus receives a color image print signal, as shown in FIG. 3, the roller 5 rotates in the direction of the arrow R2, and the entrance guide 70 guides the sheet S in the direction of the nip N2. The sheet S on which the color image is formed is conveyed by the roller 5 on the unfixed toner image side and the film 23 on the back side to perform fixing.

As described above, when a monochrome image is fixed, since heating and pressure are applied directly to the film 13 from the toner image side of the sheet S, the elastic layer necessary to prevent the gloss unevenness described in the description of the conventional example has a toner image. Although not on the surface side, a black monochrome image has many character images and gloss unevenness is not conspicuous, so that a sufficient surface property can be obtained even with such a configuration.

The advantage of the case where the film 13 is pressed against the toner image surface side is that heat is directly supplied from the heater 12 to the toner image T of the sheet S through the film 13, so that the heat efficiency is very high, and That is, fixing can be performed even if the surface temperature of No. 5 is relatively low. In other words, the time required to raise the temperature of the roller 5 can be shortened, the first print time can be shortened, the interval between fixing in continuous printing can be shortened, and high-speed continuous printing of 16 sheets per minute can be performed. It becomes possible.

In fixing a color image, since the roller 5 having the elastic layer 7 is on the toner image side of the sheet S,
As with the conventional fixing device, the roller 5
Since the elastic layer 7 on the surface is in contact so as to wrap around, gloss unevenness can be prevented.

However, in this color image mode, the fact that toners of a plurality of colors must be sufficiently melted and mixed, and that the ceramic heater
Is located on the side opposite to the toner image surface, the heat loss from the heat supplied from the ceramic heater 22 to the toner image T to be melted after passing through the sheet S may be large. It has been found that the temperature of the ceramic heater 22 and the surface of the roller 5 immediately before the start of fixing must be set higher than the temperature of the surface of the ceramic heater 12 and the roller 5 in the monochrome mode in order to obtain a proper fixing property. I have. For this purpose, the time from standby to the start of fixing and the fixing interval during continuous printing need to be slightly longer, but in the case of the rotary developing type color image forming apparatus of the present embodiment, fixing from the standby in the monochrome mode is performed. Time to start and
Since the color image forming time is about four times longer than the fixing interval during continuous printing, it is possible to take a sufficient time.

Further, in the fixing device 1 of this embodiment, since the heater units 10 and 20 are independently urged with the roller 5 interposed therebetween, the nip Nl and the nip N2
Can be set individually, and at the same time, the fixing temperature of the heater units 10 and 20 can be set independently, so that the optimum fixing conditions are set in both monochrome and color print modes. It has become possible.

[Second Embodiment] Next, another embodiment in which the first embodiment is partially modified will be described. The same parts as those in the previous embodiment are denoted by the same reference numerals, and description thereof is omitted.

FIG. 4 shows a fixing device in which the configuration of each heater unit as the first and second heating means is changed.
The heater unit 30 includes a cylindrical sleeve 31 as an electromagnetic induction heating member, and a magnetic core 3 as a magnetic field generating means.
2. The nip Nl is formed by the excitation coil 33 and the sleeve guide 34, which are pressed against the roller 5 by pressing means (not shown). Similarly, the heater unit 40 includes a sleeve 41, a magnetic core 42, an exciting coil 43, and a sleeve guide 44, and forms a nip N2. When the roller 5 is driven, the sleeves 31 and 41 are also driven to slide and rotate around the sleeve guides 34 and 44, respectively.

Here, the sleeve 31 is composed of an electromagnetic induction heating layer made of a ferromagnetic cylindrical thin film metal as a base layer, and a release layer using PFA or the like provided on the outer surface thereof. The magnetic core 32 is made of a material used for a transformer core such as ferrite or permalloy having a high magnetic permeability so as to have a substantially cross-sectional shape in cross section, and is disposed in the sleeve guide 34. The exciting coil 33 is formed by bundling a plurality of insulated copper thin wires into a magnetic core 32.
Formed by winding a plurality of times.

The excitation coil 33 has a frequency of 20 kHz to 500
An excitation circuit (not shown) capable of generating a high frequency of kHz with a switching power supply is connected, and the excitation coil 33 generates an alternating magnetic flux by an alternating current (high-frequency current) supplied from the excitation circuit. The generated alternating magnetic flux is guided to the magnetic core 32 and is concentrated and distributed around the nip portion N, and generates an eddy current mainly in the electromagnetic induction heating layer of the sleeve 31 before and after the nip portion N. Joule heat (eddy current loss) is generated in the heat generating layer due to the eddy current and the specific resistance of the heat generating layer, and the temperature of the sleeve 31 rises. The temperature of the sleeve 31 is controlled such that a predetermined temperature is maintained by controlling the current supply to the exciting coil 33 by a temperature control system including a temperature detection unit (not shown).

Sleeve 4 in heater unit 40
1, magnetic core 42, exciting coil 43, sleeve guide 4
4 is exactly the same.

In this configuration, similarly to the first embodiment, the sheet S in the monochrome mode is generated by the print signal.
Is guided to the nip Nl, the heater unit 10 is fixed on the toner image side, and in the color mode, the sheet S is guided to the nip N2, and the roller 5 is on the toner image side. In the monochrome mode, the sleeve 31 directly heats the toner image surface, so that the thermal efficiency is good and suitable for high-speed continuous printing. In the color mode, the roller 5 having the elastic layer is on the toner image surface side, so there is no gloss unevenness. Fixing suitable for a color image is performed.

Compared with the heater unit using the ceramic heater of the first embodiment, the heater units 30 and 40 using the electromagnetic induction heating of this configuration can apply a larger amount of heat to the roller 5 and the sheet S in a short time. Since it can be supplied to the printer, it is possible to cope with a further increase in print speed.

[Third Embodiment] A third embodiment, which is partially modified, will be described. The same parts as those in the above-described embodiment are denoted by the same reference numerals, and description thereof is omitted.

FIG. 5 shows an example in which a conventional heat roller is used for a heater unit as a heating means. The heater unit 50 has a heat-resistant release layer 5 such as PFA on the surface.
2 and a metal thin-walled heat roller 51, and a halogen heater 5 as a heat generating means provided inside the heat roller 51.
Consists of three. Similarly, the heater unit 60 has the release layer 62.
A heat roller 61 provided with a halogen heater 63,
The nip Nl and the nip N2 are formed by being independently pressed by the rollers 5, respectively.

Similarly, in this configuration, in the monochrome mode, the sheet S is guided to the nip Nl, the heater unit 50 is on the toner image side, and in the color mode, the sheet S is guided to the nip N2, and the roller 5 is Fixing is performed on the image side.

Here, since the halogen heaters 53 and 63 heat the inner surfaces of the rollers 51 and 61 in a non-contact manner, respectively, the heat transfer efficiency does not reach the above two embodiments, and the surface temperature of the roller 5 is reduced to a predetermined fixing temperature. Although a slight wait time is required for raising, the rising time can be sufficiently reduced as compared with the conventional fixing device because the rollers 51 and 61 have no elastic layer.

[Others] The fixing device of the embodiment according to the present invention has been described as the fixing device of the intermediate transfer type color image forming apparatus shown in FIG. 1, but other methods such as a multiple transfer method and an in-line method. Needless to say, it may be used as a fixing device of a color image forming apparatus such as a multiple developing system.

[0063]

According to the present invention, an elastic layer is provided on the surface,
A first fixing unit formed by pressing the first heating unit and the second heating unit at opposing positions with respect to a roller that is driven to rotate forward and reverse, to a second fixing unit,
By selectively guiding the material to be heated by the transport path switching means, it is always optimal in each of a monochrome print mode requiring high-speed continuous printing and a color print mode which is slow but emphasizes surface properties after fixing. Fixing property can be obtained. Further, since the first and second heating means do not have an elastic layer and have a small heat capacity, it is possible to reduce the start-up time and the standby power during standby.

[Brief description of the drawings]

FIG. 1 is a schematic diagram of a color image forming apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view of the fixing device according to the first embodiment of the present invention.

FIG. 3 is a sectional view of the fixing device according to the first embodiment of the present invention.

FIG. 4 is a sectional view of a fixing device according to a second embodiment of the present invention.

FIG. 5 is a sectional view of a fixing device according to a third embodiment of the present invention.

FIG. 6 is a sectional view of a fixing device of a conventional color image forming apparatus.

[Explanation of symbols]

 Reference Signs List 1 fixing device 5 roller 10 heater unit (first heating unit) 20 heater unit (second heating unit) 70 entrance guide 75 discharge roller S sheet T unfixed toner Nl nip (first fixing unit) N2 nip (first Second fixing section)

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H030 AD04 AD05 AD07 AD08 BB24 BB34 BB42 BB63 2H033 AA20 AA30 AA32 AA45 BA01 BA02 BA08 BB05 BB06 BB18 BB28 BB33 BE03 BE06 CA07 3K058 AA02 AA03 BA18 CE03 DA04 DA22 GA03

Claims (9)

[Claims] A first heating means having an elastic layer on its surface and being pressed by a first heating means having no elastic layer on its surface against a rotating body driven to rotate forward and reverse. A fixing unit, a second fixing unit formed by pressing a second heating unit having no elastic layer on the surface thereof against the rotating body, and the first fixing unit or the second fixing unit. Transport path switching means for selectively switching the transport path of the material to be heated so as to guide the material to be fixed to the fixing unit, wherein the unfixed toner image is formed on one surface of the first fixing unit or the second fixing unit. A fixing device for fixing an unfixed toner image to the material to be heated by heating the material to be heated while nipping and transporting the material to be heated. 2. The fixing device according to claim 1, wherein the first heating unit and the second heating unit are arranged at positions substantially facing each other with respect to the rotating body. 3. At least one of the first heating means and the second heating means comprises at least a fixed heating element, and a film slidably movable with its inner surface opposed to and pressed against the heating element. The fixing device according to claim 1, wherein: 4. The fixing device according to claim 3, wherein the heating element is a ceramic heater or an electromagnetic induction heating member. 5. At least one of the first heating means and the second heating means has at least a fixed support, and an electromagnetically induced heat generating member whose inner surface is slidably moved by opposing pressure contact with the support. The fixing device according to claim 1, further comprising a film, wherein the film generates heat entirely or at least partially by the action of a magnetic field of a magnetic field generating unit. 6. The apparatus according to claim 1, wherein at least one of said first heating means and said second heating means is a rotating body made of a pipe-shaped metal having a heating lamp therein as a heating means. 3. The fixing device according to 1 or 2. 7. In a single-color fixing mode, a material to be heated is guided to the first fixing unit for fixing, and in a full-color fixing mode, the material to be heated is guided to the second fixing unit for fixing. The fixing device according to claim 1. 8. A fixing device capable of setting a plurality of levels of fixing and conveying speeds, wherein a material to be heated is guided to the first fixing section during high-speed fixing and fixed to the second fixing section during low-speed fixing. The fixing device according to any one of claims 1 to 7, wherein the fixing device guides and fixes the material to be heated. 9. An image forming apparatus comprising: an image forming unit that forms a single-color or multi-color toner image on a material to be heated; and a fixing device that fixes the toner image on the material to be heated. Is any one of claims 1 to 8
An image forming apparatus, comprising: the fixing device according to any one of the preceding claims.