JPH0325480A - Fusing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a fixing device that applies thermal energy to an image carrier (recording material) via a film. 'This addition #IIItil1 is suitable for electrophotography, electrostatic recording, magnetic recording, etc. in image forming devices such as copying machines, laser beam printers, facsimile machines, microfilm reader printers, image display devices, and recording devices. Recording materials (electrofax sheets, electrostatic recording sheets, transfer material sheets, printing paper, etc.) are produced using toner made of heat-melting resin, etc. using image forming process means.
An unfixed toner image corresponding to the target image information is carried on the surface of the recording material using a direct method or an indirect method (copying), and the unfixed toner image is permanently attached to the surface of the recording material carrying the image. It can be used as an image fixing device that heats and fixes a fixed image. Furthermore, the present invention is not limited to the IIi image fixing R apparatus, but can be widely used as a means for heat-treating the t' carrier, for example, the apparatus '41 which heats a recording material carrying an image to improve its surface properties. (Prior Art) Conventionally, a heating device for a recording material, for example, for heat-fixing an image, includes a heating roller maintained at a predetermined temperature, and a pressure roller having an elastic layer and pressed against the heating roller. By,
A heated roller system that heats the recording material while supporting it is often used. A belt fixing system is also known as an image fixing means, as disclosed in US Pat. No. 3,578,797. This is done by: (1) Bringing the toner image into contact with a heating body web and heating it to its melting point to melt it; (2) After melting, the toner is cooled to a relatively high viscosity; and (2) The tendency of the toner to stick is weakened. This method allows the adhesive to be fixed without causing offset by peeling it off from the heating web. There are also flash fixing methods and oven fixing methods. Recently, a heating device II (film heating method) has been devised that consists of a fixedly supported heating body, a film that is pressed against the heating body, and a pressure member that heats the recording material through the film. There is. The system device disclosed in Japanese Patent Application Laid-Open No. 83-3131.82, which was previously proposed by the present applicant, belongs to this category, and it is not fixed through a thin heat-resistant film (sheet) that slides in pressure contact with a fixed heating element. This is a heating device that basically applies heat energy to the toner image to soften and melt it, separating the film and recording material, or separating the film and recording material after the toner has cooled and solidified. (Problems to be Solved by the Invention) However, the conventional heat roller method as described above, the belt fixing method described in U.S. Pat. No. 3,578,797, and other methods have the following problems. was there. Heat roller method ■It takes a considerable amount of time to reach the specified temperature, and during this time the image forming function is prohibited.

There is a so-called wait time. ■Because it requires heat capacity, a large amount of electricity is required. ■A heat-resistant erect bearing is required because the roller temperature is high for rotating rollers. ■The roller is in direct contact with the hands, which may be dangerous. l material is required. ■Due to the fixing temperature and curvature of the roller, the recording material wraps around the roller and the recording material jams} It is easy to see the trouble. ■Because the temperature at the fixing point where the toner is fixed on the recording material is equal to the temperature at the separation point between the recording material and the heat roller, high-temperature offset that depends on the separation temperature is likely to occur, and image gloss depends on the separation temperature. The degree is uncontrollable.

Flash, oven fixing method ■The device becomes larger. ■There is a risk of fire if the T II of the image decreases or the recording paper stays in the fixing device. Belt fixing method In this method, the wait time is the same as in the above-mentioned heat roller method in sections ■ and ■. 1) There is a problem with large power consumption, etc. Film heating method: - Low heat capacity, so low power - Shorter wait time - Fixing point and separation point can be set separately, so offset I. is also prevented. However, in the case of a belt fixing method or a film heating method, meandering of the belt or film becomes a problem.

Therefore, in the past, the belt drive roller was made into a crown shape, and the bell 1 tended to be located at the center of the drive roller.
■Belt lol! ! ! l Put a rib on the circular end of the roller so that the belt does not move past the rib position.
■Measures were taken such as creating a hole at one end of the belt and installing a sprocket wheel at the end of the drive roller to drive it. However, JP-A-62-31. 3 1 8
As described in Publication No. 2, when using a thin endless belt with a width of about 30 gm, if you take the above measure (■), the belt will move toward the center and wrinkle.If you take the measure (■), When we took measures against buckling at the end of the belt or drive roller, the problem occurred that the belt would break at the hole. The present invention relates to a heating device that places a heating body on one side of a film (sheet), brings an image carrier in close contact with the other side, and applies thermal energy to the image carrier through the film. The purpose is to solve the meandering problem of the film when using a belt type film. (Means for Solving the Problems) The present invention provides a heating element on one side of the film, an image supporter in close contact with the other side, and heat energy applied to the image supporter through the film. The fixing device is characterized in that the film is an endless film, and the inner circumferential length of the film on the v4 end side in the film width direction (film axis direction) is different from each other. In addition, in the present invention, when the circumference of the film with the shorter inner circumference is L (as) and the difference in circumference with the longer one is D (1), the difference between the two L-D There is a fixing device characterized in that the relationship is set to IX1 (M'≦D/L≦3×10−”, preferably 6×10−′≦D/L≦3×10).

(Function) The meandering prevention effect of the entresive belt-like film with the above structure will be explained using the image fixing device all according to Book 9lIJI shown in FIG. 2 as an example. <1) Image fixation w
Overall configuration of IT First, the configuration of the example device shown in Figure 1 will be explained. Reference numeral 24 denotes an endless belt-shaped fixing film, which includes a driving roller 25 on the left side, a driven roller 26 on the right side, and a low heat capacity linear heating element 2o as a heating element disposed below both rollers 25 and 26. It is suspended between three members 25, 26, and 20. The driven roller 26 also serves as a tension roller for an endless belt-shaped fixing film 24, and the fixing film 24 is rotated clockwise at a predetermined circumferential speed as the drive roller 25 rotates clockwise, that is, the image form I
tThe circumferential speed is the same as the conveyance speed of the transfer material sheet P, which is an image carrier (recording material) carrying the unfixed toner image Ta conveyed from the L section 8 side on its upper surface, to avoid wrinkles, meandering, and speed delays. It is dynamically driven. Reference numeral 28 denotes a pressure roller having a rubber elastic layer with good release properties such as silicone rubber, which serves as a pressure member and presses the heating body 20 by sandwiching the downward film portion of the endless belt-shaped fixing film 24. They are brought into opposing pressure contact with the lower surface with a total pressure of, for example, 4 to 7 kg by force means (not shown), and are rotated counterclockwise in the forward direction in the conveying direction of the transfer material sheet P. The low heat capacity linear heating element 20 as a heating element in this example includes a horizontally elongated heater support 27 having rigidity, high heat resistance, and heat insulation properties and having a longitudinal direction in the transverse direction of the fixing film (film width direction); It has a heater substrate 2l equipped with a heating element 22 and a temperature measuring element 23'J, which is integrally attached and held along the longitudinal direction on the lower surface side of the support. The heater support 27 supports the heating body 20 insulatingly with respect to the constant R device 11 and the entire image forming apparatus.
(polyphenylene sulfite), PAI (polyamideimide), PI (polyimide), PEEK (polyetheretherketone), liquid crystal polymer, and other highly heat-resistant resins, as well as composite materials of these resins and ceramics, metals, glass, etc. It can be composed of As an example, the thickness of the heater board 2l is 1.0-t+1.
It is an alumina substrate with a length of 0-240 mm. heating element 2
2, an electrically resistive material such as Ag/Pd (1N palladium) is coated approximately at the center of the lower surface of the substrate 2l along the length by screen printing or the like to a thickness of 10 μm and a width of 1 to 3 mm. In addition, the surface is protected! Heat-resistant glass 2 as lPfI
1a coated with approximately the top coat. For example, the temperature sensing element 23 is mounted on the upper surface of the substrate 21 (the heating element 22
This is a low heat capacity resistance temperature detector made of a Pt film or the like, which is coated approximately in the center of the opposite surface (the opposite surface) by coating by screen printing or the like. As the temperature measuring element, a thermistor or the like having a low heat capacity may be arranged on the substrate 21. In the case of the heating element 20 of this example, electricity is applied to the linear or band-shaped heating element 22 from both ends in the longitudinal direction to cause the heating element 22 to generate heat over substantially its entire length. Power is ACIO
The energizing power is controlled by controlling the phase angle of energization by an energization control circuit (not shown) including a triac according to the temperature detected by the temperature measuring element 23. (2) Fixing execution operation The image forming apparatus performs an image forming operation according to the image forming start signal, and the image is transferred from the transfer section (8) to the fixing device ll11.
The transfer material sheet P carrying the unfixed toner image Ta on its upper surface is guided by a guide 29 and placed between the heating body 20 and the pressure roller 2.
Fixing film 24 and pressure roller 28 at pressure contact portion N with
The fixing film 2 is inserted between
The fixing film 24 passes through the mutual pressure contact area N between the heating body 20 and the pressure roller 28 while being subjected to a clamping force while being in close contact with the lower surface of the fixing film 24 without causing any surface deviation or wrinkles. go. Since the heating body 20 is electrically heated at a predetermined timing in response to an image forming start signal, the toner image Ta is heated at the pressure contact portion N and becomes a softened and melted image Tb. The fixing film 24 is fixed at the edge fflls of the support 27 with a large lll1 ratio (curvature radius of about 2 mm).
The running direction changes at a sharp angle (bending angle θ is 45°). Therefore, the pressing part N is overlapped with the fixing film 24.
The sheet P conveyed through the curvature separates from the fixing film 24 at the edge portion S, and is transferred to the paper output tray (12).
Paper is ejected to

By the time the paper is ejected, the 1.toner has been sufficiently cooled and solidified, and has become completely fixed on the sheet P (toner image Tc). The toner used in this example has a sufficiently high viscosity when heated and melted, so even if the toner temperature at the time of separation from the fixing film 24 is higher than the melting point of the toner, the adhesion force of the toner to the fixing film 24 is This is extremely greater than the adhesive force, so when the fixing film 24 and the sheet P are separated, toner offset to the fixing film 24 does not substantially occur. In addition, in this example, the heating element 22 and the substrate 2l of the heating element 20 have a small heat capacity and are supported by the support 27 insulatingly, so that the heating element 22 and the substrate 2l at the pressure welding part N have a small heat capacity.
Since the surface temperature of 0 rises in a short period of time to a high enough temperature for the melting point of the toner (or the temperature at which it can be fixed on the sheet P),
There is no need to raise the temperature of the heating element 20 in advance (so-called standby temperature 31), and energy saving can be achieved.
Moreover, it also prevents the temperature inside the machine from rising. (3) Film meandering prevention t1: Effect (Part 1) Regarding the endless fixing film 24 in the apparatus shown in FIG. Takiho), and set the film inner circumference length of the film edge on the opposite back side (referred to as R side) to 0.
2 (mm). It is assumed that the positions of the rollers 25 and 26 at both ends of the film are approximately fixed, and the tensions at both ends of the film are approximately equal. Figure 2 shows the ¥300 film 2 when the device in Figure 1 is viewed from above.
4. It is a model diagram showing the morphological relationship of the three drive rollers 25 and 26. D=1 for fixing film 24
57, D2-D+=0.3, that is, there is a taper. The outer diameter of the drive roller 25 is dl (am) on the F side and d2 on the R side.
(-1), and the outer diameter of the driven roller 26 is dz on the F side.
(am). On the R side, let d et al. (Entertainment 1). Also, the distance between the axes of the drive roller 25 and the slave roller 26 is set to g on the F side.
I (am). Set it to gz (1 m) on the R side. In this example, d2−d+ =0.2, d2fud et al., and g2−g
l Emperor is 0.2. When the fixing operation is performed with such a configuration, the fixing film 24 initially meanders toward the F side or the R side, but the meandering stops at a certain point, and at that point the fixing film 24 moves toward the rollers 25 and 26. The position is stable. Figures 2 and 3 show the mechanism by which the meandering stops as described above.
Explain based on the diagram. FIG. 3 is a diagram in which the force for conveying the fixing film 24 in the axial direction of the rollers 25 and 26 is plotted on the vertical axis, and the position of the F side end surface of the fixing film is plotted on the horizontal axis. Horizontal axis position x = O
When x=H, the film 24 is at the F side end of the effective length of the rollers 25 and 26, and when x<0, the film comes off the roller and is damaged.When x=H, the film is at the end of the effective length of the rollers. R [At the edge, when x > H, the film will be removed from the roller and the film will be damaged. In this example, the factors that generate the force that conveys the fixing film 24 in the roller axial direction include: ■Fs of the roller 25●2B●Difference in distance between Rga. ■The tapered shape of rollers 25 and 26 is dominant. In other words, the distance g between the axes of rollers 25 and 26 in ■ is on the F side●
If it is different on the R side, the conveyance force F1 is applied to the fixing film so that the fixing film moves toward the side where g is smaller.
F+ depends on the tension of the fixing film 24, and the greater the holding force, the greater the absolute value of F1. In the example shown in Figure 2, it is g2-gt)O. Since the positions of the rollers 25 and 26 are almost constant, the more the fixing film 24 moves toward the R side, the more the tension of the film increases, and therefore the absolute value of Fl also increases. Next, regarding the tapered shape of the rollers 25 and 26 in (■), if the diameter d of the rollers is different between the F side and the R side, the conveying force F2 acts on the fixing film so that the fixing film 24 moves toward the side with larger d. ．． For the same reason as mentioned above, the more the fixing film moves toward the R side, the more the absolute value of F2 increases. Regarding F+ and Fz, the contribution rate of the fixing film tension is generally different, and according to experiments by the present inventors, the contribution rate was higher for F2 than for F+. If the force is -, the resultant force of F1 and F2 becomes the force that drives the film 24 in the axial direction. In this example, Fl + F2 becomes O at position C between axial positions IIO and E. Therefore, in this example, the fixing film is stably driven at a point where the end face on the F side is at position tc. Roller diameter difference d2-d+. Even if I change d and d3 by ±0.05, again! 2 -Even if gl is changed by ±0.05ms. Location C existed between locations O and E. Comparative example ■: In the above example, the inner circumference of the fixing film +01
-02 If 1 is approximately 0, dz-d+=0.2
．． If dr-d3=0, if you try to equalize the tension on the F side and R side of the fixing film 24, g
2-g+ <o. Then, F+ always points in the R direction. Since F2 is a force in the R direction, the fixing film moves in the R direction regardless of its position, and eventually deviates from the roller and is damaged. On the other hand, if the tension is different between the F side and the R side, the fixing film tends to wrinkle, which causes durability problems. Comparative example ■; Inner circumference length difference +01 -D2 1=0, dz-d
+ to O. d*-ds=O. When gz −g+ =O, F+=0 and F2=0, and when Ft+F2=0, meandering of the fixing film 24 does not occur. However, roller 2
Due to the machining accuracy of the rollers 5*26 and the assembly accuracy of the fixing device, there will be slight tolerances in the diameters and interaxial distances of the rollers 25*26, so such a configuration is practically impossible.
(4) Film meandering prevention effect (Part 2) The conveying force F1
It is necessary to set 11F2 in the opposite direction with respect to the axial direction of the rollers 25 and 26 in the meandering control using the above method. To do this, 1) make the inner circumference of the fixing film 24 different at both ends, and 2) make the roller 25 or 26 have a larger diameter at the end on the same side as the end with the longer inner circumference of the fixing film. It is necessary that the rollers 25 and 26 have a tapered shape, and that the distance between the axes of the rollers 25 and 26 is longer at the end where the inner circumference of the fixing film is longer. In particular, in order to simultaneously achieve ``■'' and ``■'', it is necessary to make the difference in inner circumferential length of the fixing film more than a predetermined value. According to the experiments of original IJJ people,
Regarding the circumferential length D [D2], however, if this ratio is increased unnecessarily, a difference in circumferential speed will occur between the R side and the F side of the fixing film 24, and there is a risk that wrinkles will occur in the fixing film 24. According to the study of books i + yi a, etc., invitation use was not possible. Although there is no damage to the film, it is preferable that the temperature of the image bearing sheet P is -3 or less, more preferably 3xlO or less. In this example, the roller 25 has a Taber shape, but the roller 24 may have a Taber shape, or both rollers 25●
26 may have a tapered shape. The taber shape can also be made into various forms, such as a part being a straight part or a raised part.

Furthermore, although the Taber shape of the fixing film 24 is straight in this example, various shapes such as a curved surface such as a hyperbola or a partially straight shape are also practicable. The method of making the fixing film 24 into a Taber shape is as follows.
■Prepare the heat-resistant layer of the fixing film using a tapered mold, and then coat the release layer.■Use a straight-shaped heat-resistant layer and heat-form it using a tapered mold when forming the release layer. Various methods are practical, such as pasting sheets of film together into a tapered cylindrical shape. (Example) (1) Example of an image forming apparatus (Fig. 4) Fig. 4 shows an image obtained by incorporating the device opening shown in the first figure as an image fixing device according to the present invention as exemplified in the @description (function) section. An example of the shape or device is shown. In this example, l! The i-image type or device is an electrophotographic copying device with a reciprocating document tray, rotating tram type, and transfer type, and l00 is a device with a width of 1 m. l is the M of the tt fudosei consisting of a transparent plate member such as a glass plate placed on the upper surface plate 100m-hi of the machine housing.
It is a manuscript storage stand, and the upper surface plate 100a of the box is placed on the right side a in the drawing.
, and are driven back and forth at predetermined speeds to the left a'. G is the original, and it is placed on the original 8I storage stand l with the image side to be copied facing down, according to the predetermined installation standards.
The document is set by placing the document pressure bonding plate 1a on top of the document and pressing it down.

Reference numeral 100b denotes a slit opening, which serves as a part of the manuscript light, and is opened on the surface of the al cabinet physical plate 100a with its eldest opening in a direction perpendicular to the direction of reciprocating movement of the manuscript tray l (direction perpendicular to the plane of the paper). Manuscript aI! The downward facing image of F (MG) set on the table 1 is shown in the n-th slit opening 100b on the right side or the left side in the process of forward movement of the document table 1 to the right side a. In the process of passing, the light L from the lamp 7 is received through the slit opening ioob and the transparent document a placing table L, and the illumination scanning light is reflected from the document surface into a short focal point. An image is formed and exposed on the surface of the photosensitive drum 3 by the small-diameter Ayu image element A1/A2.The photosensitive drum 3 is coated with a photosensitive layer such as a zinc oxide photosensitive layer or an organic semiconductor photosensitive layer. The center is rotated sgJ in the clockwise direction of arrow b at a predetermined circumferential speed, and in the rotation process the band 'i
The surface of the photosensitive drum 3 is subjected to image-forming exposure by being uniformly charged with positive or negative polarity by the T-unit 4, and subjected to condensation fR exposure (slit exposure) of the original image on the uniformly charged surface. Electrostatic latent images corresponding to the original image are formed one after another. This electrostatic latent image is sequentially developed by a developing device 5 using toner made of resin or the like that softens and melts when heated, and the developed toner image is transferred to a location where a transfer discharger 8 is provided as a transfer section. I will do it. S is a cassette loaded with transfer material sheets P as recording materials, and the sheets in the cassette are fed one by one by the rotation of the feed roller 6, and are then fed onto the drum 3 by the registration roller 9. When the leading edge of the toner image form R & reaches the transfer discharger 8, the leading edge of the transfer material sheet P also reaches the position between the transfer discharger 8 and the photosensitive drum 3 so that they are aligned. The timing is adjusted and the data is fed synchronously. -Then, the toner image on the photosensitive drum 3 side is sequentially transferred onto the surface of the fed sheet by the transfer discharger 8. The sheet to which the toner image has been transferred in the transfer section 8 is sequentially separated from the three surfaces of the photosensitive drums by a separating means (not shown), and is conveyed!
110 to the fixing device 51ii and the above-mentioned (action)
As explained in the section above, the carried unfixed toner image is heated and fixed, and is discharged onto the paper output tray 12 outside the machine as an image-formed product (copy). On the other hand, after the toner image has been transferred, the surface of the photosensitive drum 3 is subjected to removal of adhered contaminants such as residual toner by a cleaning device 1i13, and is used repeatedly for image formation. (2) Regarding the fixing film 24 The configuration, fixing operation, etc. of the fixed R unit W11 are as explained in the section (Function) above with reference to FIGS. 1 to 3. Here, we will briefly explain the material of the fixing film 24. The fixing film 24 has heat resistance, releasability, durability, etc.
Composite layer films generally less than 100 gm, preferably less than 40 gm can be used. FIG. 5 is a schematic cross-sectional view of the layer structure of an example of a composite layer film, in which 24a is a heat-resistant layer as a base layer (pace film) of the fixing film, and 24b is the outer surface of the heat-resistant layer 24a (the side facing the toner image). (face) M
This is a layered release layer. The heat-resistant layer 24a is made of, for example, polyimide, polyetherothietherketone (PEEK). Polyether sulfone (PE
S). Highly heat-resistant resin films such as polyetherimide (PEX), polyparabanic acid (PPA), and PFA, and N
Materials with excellent strength and heat resistance, such as metals such as i●SUS●Ai, can be used. The release layer 24b is preferably made of, for example, a fluororesin such as PTFE (polytetrafluoroethylene), PFA-FEPI, or silicone resin. Release layer 24b for heat-resistant layer 24a
The lamination process includes adhesive lamination of the release layer film, electrostatic coating (coating) of the release layer material, vapor deposition, CVD, etc.
& Lamination using film technology, heat-resistant layer material and separation 5! This can be done by coextruding layer materials to form a two-layer film.
In addition, the release layer 24b is made of carbon black, graphite,
By methods such as mixing conductive agents such as conductive whiskers,
The resistance on the surface of the fixing film 24 may be lowered. This can prevent the toner contacting surface of the fixing film 24 from being charged. When the toner contact surface of the fixing film 24 is insulating, the surface of the fixing film becomes electrically charged, which may disturb the toner image on the recording material sheet P or transfer the toner image to the fixing film 24 (so-called Teiden offset). ), but these problems can be avoided by taking the above measures. (3) Example 1 of another fixing device structure (FIG. 6) FIG. 6 shows another example of the structure of the fixing device W1ll. Reference numeral 32 denotes a heating roller as a heating body, which has a built-in heater 33, and by causing the heater 33 to generate heat appropriately according to the heating roller surface overflow detected by the temperature measuring element 4l, the surface of the heating roller 32 is kept at a predetermined temperature. I can do miscellaneous things. Reference numeral 34 denotes a small-diameter separation upper roller disposed downstream of the heating roller 32 in the transport direction of the sheet P. 25 is a drive roller that rotates and runs the fixing film 24, and 26 is a drive roller that always keeps the fixing film 24 at an appropriate tension. This is a driven roller that energizes the engine. In addition, the driving roller 25 and the heating roller 32
Both are rotated clockwise at the same speed as the conveyance speed of the sheet P. The fixing film 34 has a structure according to the present invention, and has the above-mentioned 4.
f! & Materials 32●34●25●26 are suspended. 36 is a pressure roller disposed opposite to the lower side of the heating roller 32; 35 is a lower separation roller disposed opposite to the lower side of the upper separation roller 34; 37 is the pressure roller 36 and the lower separation roller. This is an endless belt-like transport belt (huck-up belt) suspended between 35 and 35. The pressure roller 36 is a roller whose surface layer is made of an elastic material such as silicone rubber. This pressure roller 36 and heating roller 3
2, the endless belt-like fixing film 24
A contact pressure of, for example, 4 to 7 kg in total is obtained by sandwiching the descending side film portion of the film by a force means (not shown). The correction roller 36 rotates as a result of the rotation of the heating roller 32, and the conveyor belt 37 also transfers the sheet to the fixing film 3.
4, it rotates counterclockwise at the same speed as the conveyance speed of the sheet P.

The copying device operates to form an image in response to the image formation start signal and transfers f! The transfer material sheet P carrying the unfixed toner image Ta on its upper surface is conveyed from 88 to the fixing device dll.
The heating roller 32 is rotationally driven, so that the fixing film 2
4 and the conveyor belt 37 are rotating, the heating roller 32 and the pressure roller 36 are guided by the guide 29.
The unfixed toner image enters between the fixing film 24 and the conveyor belts I and 37 in the pressure contact part N and rotates in the same direction at the same speed as the conveyance speed of the sheet 1-P. Mutual pressure between the heating roller 32 and the pressure roller 36 *? It passes between B and s while being subjected to a pinching force. In the process of passing through the mutual pressure contact fiN, the toner image Ta on the sheet P is heated and becomes a softened and melted image Tb. The sheet portion that has passed through the mutual pressure contact portion N between the heating roller 32 and the pressure roller 36 is spread between the heating roller 32 and the upper separating roller 34 until it reaches the position of the upper separating roller 34. The fixing film continues to be conveyed in close contact with the moving fixing film portion. The conveyor belt 37 is
supports the back side of the sheet P and maintains close contact between the sheet P and the fixing film 24. In this conveyance process C, the heat of the softened ◆melted toner @Tb is radiated and becomes a cooled ◆solidified toner image Tc. The toner heat dissipation in this heat dissipation process is natural heat dissipation cooling in this example, but it may also be forcibly dissipated and cooled by providing heat dissipation heat fins, air blowing means, or the like.

Then, when it is conveyed to the upper separation roller 34 for 2ts,
The running direction of the fixing film 24 is turned in a direction away from the surface of the sheet P along the separation roller 34 having a large curvature, and the fixing film 24 and the sheet P are separated from each other.
Sheets 1-P are ejected to trays 1 and 12. By this time, the toner has been sufficiently cooled and solidified TcL, and the adhesion force of the toner to the sheet P is sufficiently large.
Since the distance to the fixing film 24 is extremely small, the fixing film 24 and the sheet P can be easily and sequentially separated without substantially causing toner offset to the fixing film 24. In this embodiment, it is possible to set the temperature of the heating roller 32, which is a heating element, higher than the temperature at which high-temperature offset occurs in the conventional heating roller fixing method, thereby improving fixing performance. In addition, the allowable temperature range of the heating element is wide on the high temperature side, making it possible to simplify &1 degree control. Furthermore, when performing fixation 9IS processing of multi-color toner images, especially those of three or more colors, it is easy to mix colors because they can be sufficiently melted at high temperatures. In addition, since the toner is once melted, cooled and solidified while in close contact with the fixing film 24, and then peeled off from the fixing film 24, it is possible to make the surface properties of the toner image similar to the surface properties of the fixing film. ．． Therefore, for example, by smoothing the surface of the fixing film 24, it is possible to give the surface of the toner image Tc a gloss similar to that of a silver halide photograph. Also,
By making the fixing film 24 thin as described above, heat accumulation in the fixing film is prevented and the cooling process of the toner image is made more efficient. Furthermore, when a thin resin film was used as the fixing film, the adhesion to the toner image was improved and the heat transfer efficiency was improved. (4) Other fixing device configuration example 2 (FIG. 7) In the device shown in FIG. 6, the heating body 32 is not limited to the heating roller, but as shown in FIG. The body 20 may also be used. In this case, in addition to the above effects, the heating element 22 and the substrate 2l have a small heat capacity and are insulated, so
It has the advantage of a fast temperature rise rate and no need for standby temperature control. Also, in place of the upper separation roller 34 of the device shown in FIG.
By arranging the separation stay 38 to the right of the end [rIi] with a larger curvature as in the illustrated apparatus, it becomes possible to separate the sheet P from the fixing film 24 more reliably. (5) Example 3 of another fixing device structure (FIG. 8) The device shown in FIG. 8 is the same as the device shown in FIG. The toner image is heated by a radiant heat source 40 such as a halogen lamp disposed inside the endless fixing film 24 via the toner image. In this embodiment, it is preferable that the fixing film 24 be transparent to the radiant heat wave public. Therefore, in the wooden embodiment, a film 24 is used in which a heat-resistant layer 24a (FIG. 5) made of transparent 1x1 polyimide containing fluororesin powder and a mold release PFf 24b made of transparent silicone resin are formed. This example? In the case of the t position, since heating is performed by radiation, the toner can be instantly heated and melted.
Therefore, it is necessary to heat only the part where the seam P is in the pressure welding part N, so it is possible to save power, and there is also less in-flight heating. (Effects of the Invention) According to the present invention, a heating body is placed on one side of the film, an image carrier is brought into close contact with the other side, and thermal energy is applied to the image carrier through the film at a constant R. Regarding the device, the problem of meandering of the fixing film when using an endless belt type film can be solved by making the inner circumferential length of the film on both ends (in the film width direction and film axis direction) different from each other. It can prevent this and provide stable fixing performance over a long period of time. Since the film has a tapered shape, when the fixing film is suspended and stretched between rollers, etc., the fixing film can be installed so as to surround the rollers and other members from the side with the larger inner circumference. Assembly efficiency is improved compared to the case of endless film with the same inner circumference length.

[Brief explanation of drawings]

FIG. 1 is a structural diagram of an example of a fixing device according to the present invention, and FIG. 2 is a model diagram showing the morphological relationship of the fixing film, a driving roller, and a driven roller when the device is viewed from above. Figure 3 shows the force that transports the fixing film in the axial direction on the vertical axis.
A graph in which the position of the lower end surface of the fixing film is plotted on the horizontal axis, FIG.
The structural model diagrams, Figures 6 to 8, are diagrams of other examples of the structure of the fixing device. 24 is an endless film, 20, 32, 39, and 40 are heating bodies, and P is a transfer material sheet as an image carrier (recording material). Special 1 Kinde Hajin Canon Co., Ltd. Yoko 1 Figure (3 (1- a++ko#k!Jf+1 younger brother 2 Figure younger brother 5

Claims (2)

[Claims] (1) A fixing device in which a heating body is placed on one side of a film, an image carrier is brought into close contact with the other side, and thermal energy is applied to the image carrier through the film, and the film is an endless film. A fixing device characterized in that the inner circumferential length of the film on both ends in the film width direction is different from each other. (2) When the circumference of the film with the shorter inner circumference is L (mm) and the difference in circumference with the longer one is D (mm), the relationship between both L and D is 1×10 ^-^4≦(D/L)≦3×10^-^2Preferably, it is set to 6×10^-^4≦(D/L)≦3×10^-^3. The fixing device according to claim 1.