JPH03241378A - Fixing device - Google Patents

Abstract

PURPOSE:To stably drive a fixing film by maximizing the coefficient of friction between a driving roller which is a driving means and the fixing film. CONSTITUTION:A heating body having a low-heat capacity 1 and a thin heat- resistant endless film 5 are used, and tension is imparted to the film 5 to carry it by the driving roller imparting the drive to the film 5 and at least by another roller 7. At this time, the coefficient of friction between the contact face with the fixing film on the driving roller 6 and the fixing film 5 is set larger than that between a contact face of the fixing film of the other roller 7 and the fixing film 5. In other words, the coefficient of friction between the driving roller 6 which is the driving means and the fixing film 5 is maximized. Thus, the fixing film can be stably driven.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a fixing device such as a device that heat-processes an image bearing member, such as an image forming device that heat-fixes a toner image on a recording material, and further relates to a fixing device such as an image forming device that heat-fixes a toner image on a recording material. The present invention relates to a fixing device that obtains a fixed image with improved image quality by modifying the surface properties of the image.

[Prior Art 1] Conventionally, a fixing device used in this type of image forming apparatus uses a heating roller maintained at a predetermined temperature and a pressure roller having an elastic layer and in pressure contact with the heating roller. A heating roller fixing method is often used in which a recording material on which an unfixed toner image is formed is heated while being nipped and conveyed. However, in this heating roller fixing method, in order to prevent the so-called offset phenomenon in which toner is transferred to the heating roller, it is necessary to maintain the heating roller at an optimal temperature, and the heat capacity of the heating roller and heating element must be increased. As a result, it takes a long time to heat the heating roller to a predetermined temperature, resulting in a long standby time and high power consumption when using the device.

A film fixing system as described in US Pat. No. 3,578,797 is known as a method for solving these drawbacks.

[Problems to be Solved by the Invention] Incidentally, in such a fixing device, a heating element with a low heat capacity and a thin heat-resistant endless film with a thickness of about 40 μm or less are used in order to shorten the startup time to a predetermined temperature. ing. It also has a shift control mechanism for transporting endless film. Further, a drive roller providing drive to the film, and at least one other roller,
A common method is to convey the film by applying tension to the film. At this time, the coefficient of friction between the drive roller and the film needs to be at least a certain value to prevent slippage (the minimum condition being that it can be driven against the pressing force from the fixed heating element and the pressure member). However, if the friction coefficient of the other roller is the same or higher, depending on the cylindricity of each roller, biasing forces will be generated in different directions against the film, and the film will stop as it repels the drive. Therefore, there is a problem that damage to the film occurs, and when electricity is being applied, thermal damage occurs to the heating body and the film. Also, since it is a thin film, the direction of the biasing force,
Depending on the difference, there is a problem that a difference occurs in the amount of film movement between the rollers, resulting in folding and overlapping of the film.

The present invention attempts to solve these problems. That is, in the present invention, while driving the fixing film,
The fixing device is designed to prevent damage to the film due to biasing forces in different directions caused by low accuracy of the rollers, and to prevent thermal damage to the heating element and the fixing film even while electricity is being applied. The purpose is to provide

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a pressure member that brings a recording material into close contact with a heating body through a thin fixing film that is driven while being in pressure contact with the heating body. A fixing device for heating and fixing an unfixed toner image on a recording material, the fixing device having a drive roller and a roller for a purpose other than driving as a drive means for the fixing film, and wherein the drive roller is in contact with the fixing film. The coefficient of friction between the surface and the fixing film was greater than the coefficient of friction between the fixing film contact surface of the other rollers and the fixing film.

[Function] According to the present invention, since the friction coefficient between the drive roller, which is the driving means, and the fixing film is maximized, stable fixing film drive can be realized, and furthermore, even when performing deviation control, Since the driving roller is stable and the gripping force on the flat surface is stable, it is possible to recover from the deviation without damaging the driving state, and it is also possible to prevent the film from folding.

[Example] FIG. 1 is a side sectional view showing one embodiment of the present invention.

In the figure, reference numeral 1 denotes a low heat capacity heating element in which a surface layer of an alumina substrate (thickness: 1 mm, width: 7 mm) is overcoated with a resistance layer and a glass layer. The heating body 1 is fixed to a holding member 2 made of a heat-resistant resin (liquid crystal polymer, PPS, etc.) fixed to a fixing stay using a maleimide-based heat-resistant adhesive.

Further, a temperature sensing element 3 is fixed to the back surface of the heating element 1 with a silicone adhesive. The temperature sensing element 3 is set in the longitudinal direction of the heating body 1 within a passage area for the smallest size paper (in this embodiment, the width of a business card) that can be passed through the apparatus. Further, on both sides of the heating body 1, electrode layers (A
As shown in FIG. 2, the contact 4 has a protrusion 4a to prevent removal and an elastic contact part 4b, and the end of the holding member 2 has a guide part for inserting the contact. 2a and a contact fixing portion 2b that engages with the protrusion 4a, and the contact pressure of the contact 4 is set such that the holding member 2 and the heating body 1 are sandwiched therebetween. This also serves to prevent the ends of the heating element 1 from peeling off. Furthermore, in the heated state, the contact pressure is not affected by thrust displacement due to thermal expansion of the holding member 2 and the heating body 1, and the contact pressure is prevented from being removed, so that stable energization is performed. A rib 2c for stopping the thrust of the heating element 1 is provided at the end of the holding member 2, and the height of the rib 2c protrudes from the lower surface of the heating element 1 by about 0.3 to 1 mm. This is because since the heating element substrate is made of alumina, the end face inevitably becomes an edge state during processing, which may damage the contact portion 4b when inserting and removing the contact.As a preventive measure, the rib 2C is protruded to serve as a guide.

5 is a fixing film with a total thickness of less than 35μ, which is made by coating a base layer (polyimide: less than 25μ) with a fluororesin as a release layer, and has an endless belt shape with a diameter of 45mm, and is nipped at a circumferential speed of 47mm/s. It is driven in the direction of arrow a by the drive roller 6 on the downstream side. This drive roller 6 has a diameter of 18.4 mm and a surface layer with a thickness of 75 mm.
Coated with a conductive silicone rubber layer of μ.

On the upstream side of the nip, a metal tension roller 7 that applies tension to the fixing film 5 with a total tension of 3 kg by a spring member (not shown) is supported so as to be able to follow the rotation of the fixing film 5. Fixing film 5 of drive roller 6
The friction coefficient μ for the tension roller 7 is set larger than that of the tension roller 7, and the outer diameter is similarly set to
By increasing the angle of the fixing film 5 and arranging the center of the drive roller 6 higher than the center of the tension roller 7, the winding angle of the fixing film 5 around the drive roller 6 is increased, and stable film drive is realized. In this embodiment, the tension roller 7 is a metal roller having an outer diameter of 14+n+++, and the winding angle α of the fixing film 5 with respect to the drive roller 6 is set at 141.6°. In addition, a small amount of fluorine grease (160±25 mg in this example) is applied to the contact surface between the fixing film 5 and the heating element 1 for the purpose of lubrication, so that it comes into pressure contact with the surface of the fixed heating element 1. between the fixing film 5 which is driven by sliding while
Prevents torque increase due to chatter, vibration, and sticking. Furthermore, it is appropriate that the friction coefficient μ of the drive roller 6 against the fixing film 5 is in the range of 0.3〈μ〉3. This is an appropriate value to prevent the occurrence of a sagging condition, and this value is also a necessary design value in the case without grease.

Furthermore, in the fixing device of this embodiment, the shift of the fixing film 5 is controlled.

As shown in FIG. 3, a detection lever 8 for detecting the film position is installed at the end of the fixing film 5 so as to be able to follow the film, and a non-contact sensor 9 detects the position of the fixing film 5. read. Further, the end of the fixing film 5 is cut diagonally, so that the detection lever 8 intermittently turns the sensor 9 on and off. Then, the shift direction and shift control area are determined based on the change in time of this 0N10FF.

Next, the conversion of the above-mentioned shift direction is as shown in Fig. 4.
A bearing 10 of the tension roller 7 is movable in the vertical direction, and is moved up and down by a swingable control arm 11. A latching solenoid 12 is provided as a vertical movement drive means to interlock with the control arm 11,
When the above-mentioned sensor 9 outputs a reversal signal, the latching solenoid 12 is operated to move the control arm 11 up and down, and the tension roller 7 is interlocked. Also bearing 10
has a first spring 13 that biases upward and a second spring 14 that biases downward. When the bearing 10 is positioned upward, the biasing force of the first spring 13 is zero and the second spring 14 is biased downward. When the downward biasing force of the first spring 14 is maximum and the bearing 10 is positioned downward, the upward biasing force of the first spring 13 is maximum and the second spring 14
is set so that the urging force of is zero. This is due to the suction force of the latching solenoid 12 when pulling up.
Only when dropped, the biasing force by the ° spring is applied effectively to increase the stroke of the latching solenoid 12, making it possible to move up and down with a more compact solenoid and less current. Next, regarding the direction of approach,
When the tension roller 7 is on the top, it moves toward the upward side, and when it is on the bottom, it moves toward the opposite side. In this way, by moving the fixing film 5 within a certain range, the fixing film 5 is stably driven. This type of deviation control is provided because the fixing film 5 is a thin film, and if a conventional belt-like flange receiver or perforation is used, the fixing film itself will be damaged. Furthermore, since the film base layer is a heat-resistant film such as polyimide, it has almost no elasticity, and it is impossible to stabilize the position using a tapered roller, drum roller, or the like. Also, the shift control is performed by the tension roller 7 on the upstream side of the nip, whereas it is performed on the downstream side of the nip.
Since this may affect the separating portion of the recording material, it is better to use a roller on the upstream side of the nip or a separate member.

Also, the aforementioned low heat capacity heating element 1, holding member 2, temperature detection element 3, fixing film 5, drive roller 6, tension roller 7, shift control configuration (bearing 10, control arm 11, latching solenoid 12), film position detection The means (detection lever 8) are all integrated as an upper unit.

These are attached to a head stay 15 as shown in FIG.
a, and is integrally constituted as an upper unit by a sub-side plate 16 to which rollers and the like are fastened after film is loaded. In addition, the unit can perform shift control and stabilization adjustment on its own, so if the fixing film is damaged in the market, it is possible to replace or clean the pressure member etc. by itself.
It is possible to replace only the upper unit instead of the entire fixing device.
This has resulted in improved serviceability.

The above-mentioned deviation stabilization adjustment is performed using the eccentric bearing 17 of the drive roller 6.
This is done by rotating the drive roller 6 to vary the relative position of the drive roller 6 in response to variations in the cylindricity of the fixing film 5, the position of the heating body 1, etc. Note that the amount of eccentricity in this embodiment is set to ±0.6 mm in the height direction. Further, the eccentric direction may be a horizontal direction, but since the horizontal direction is canceled by the tension on the fixing film 5, the vertical direction is more effective because it has a greater influence on shift and allows the amount of eccentricity to be set smaller. Furthermore, although the vertical movement stroke of the tension roller 7 mentioned above is 3 mm, depending on the vertical movement means, it is possible to set it larger to absorb variations in other parts, and furthermore, the vertical stroke itself can be set larger. It is also possible to stabilize the deviation by adjustment. However, if the tension roller 7 is at the same position as or lower than the point at which the recording material enters, there is a risk that the recording material may come into contact with the recording material due to its flapping or curled state, which may disturb the unfixed toner image. Therefore, it is desirable that the position of the tension roller 7, that is, the nip incident angle (β in FIG. 1) of the fixing film 5, be approximately 10 to 30 degrees with respect to the horizontal direction, and in this embodiment, it is 20 degrees. It is.

The above-described upper unit is combined with the lower unit consisting of a pressure member, a pressure means, a recording material conveyance guide, etc. to form one fixing device. As shown in FIG. 6, the upper unit 1
8. The lower unit 19 has engagement holes and pins that engage with each other, and after engagement, they are integrated by fastening means such as screws. At this time, at least one of the four engagement pins 20 of the lower unit 19 is attached to the eccentric pin 21.
By correcting the height and twist angle at the front and back, it is possible to reduce the twist on the upper unit 18 when combined, and to minimize the adverse effects of shifting.

Next, as a measure to prevent static electricity on the fixing film 5, a static eliminating means 22 such as a brush is provided in contact with the surface layer of the film and the tension roller 7, and is grounded via a varistor 23. Furthermore, since the silicon rubber 6a on the surface of the drive roller 6 is conductive, the core metal of the drive roller 6 also becomes a varistor ground via the fixing film 5, which prevents charge-up and prevents toner from reaching the fixing film 5. Problems such as offset are resolved. Further, the rubber 6a on the surface layer of the drive roller 6 has a heat insulating effect, and also serves to prevent a sudden temperature drop in the fixing film 5 and dew condensation on the drive roller 6 or the fixing film 5 on the roller portion. but,
If the silicone rubber 6a is made too thick, the engraving of the rubber 6a becomes large when the roller temperature rises, causing a change in the diameter of the drive roller 6, that is, a change in the circumferential speed of the fixing film 5. Therefore, considering the balance between the above-mentioned heat insulation effect and diameter change, the thickness of the silicone rubber 6a, that is,
It has been found that the appropriate thickness of the rubber layer is approximately 20 μm to 1.5 mm.

Furthermore, regarding the lower unit 19, as shown in FIG. 24, and heat and fix the image.

The pressure member 24 is a roller having an elastic layer, and the surface layer is coated with fluorine to prevent staining with toner and improve mold releasability. Outer diameter is 20mm, hardness is approximately 40
The recording material is guided to the nip by the artificial guide 25, and the separation guide 26 prevents the recording material from being caught in the pressure member 24 and guides it to the outside.In this fixing method, the above-mentioned As described above, since the heating body 1 has a low heat capacity, it has the advantage of being able to rise quickly and fixing, but on the other hand, the temperature of the pressure member 24 is low, and the temperature difference between the front and back sides of the discharged recording material becomes large. There is a drawback that the amount of curl is large.Especially in the device of this embodiment, since the bottom curl is large, the pair of discharge rollers 27 is used to remove curls.
is set higher than the recording material separation point to correct curls. Next, the paper ejection cover 28 is fixed to the fixing device and is configured not to open or close. The reason for this is that if a conventional paper ejection section is used that can be opened, the film parts will be exposed to a large extent, so the fixing film 5 may be damaged by the user, or some foreign matter may fall and pressurize the fixing film 5. This is to prevent damage to the member 24, and as a preventive measure, the paper ejection structure is fixed.

Next, the release of the pressure member 24 will be explained. JAM
In order to protect the film and pull down the JAM paper during processing, this embodiment has a pressure release mechanism.

FIG. 7(a) shows the pressurized state of the pressure member 24, and FIG. 7(b)
) indicates the pressurized state. That is, there is an upper pressure lever 29 and a lower pressure lever 30 that are rotatably supported on the same axis, and these pair of levers 29 and 30 are provided with pressure springs. Although not shown, one set is provided at the front and back. Next, the release lever 31 is configured to be rotatable so as to engage with the hook bins 32 of the two upper pressure levers, and the release lever 31 is biased by a spring 33 in the direction of engagement with the hook bins 32. As a result, the position of the upper pressure lever 29 is fixed, the lower pressure lever 30 is pressurized upward by the pressure spring, and the pressure member 24 is connected to the heating body 1 via the bearing 34 on the lower pressure lever 30. It is a pressure contact. Then, by pushing the pressure release button 35 that is slidably supported into the main body cover (not shown) in the direction of the arrow mark, the release lever 31 and the hook pin 32 of the upper pressure lever 29 are released, and the upper pressure lever 29 is released. When the lower pressure lever 30 rotates downward in conjunction, the pressure member 24 is separated from the heating body l.

Further, when pressurizing again, the pressurizing cam 36 is rotated in the direction of arrow C by a drive means (not shown), and as the protrusion 37 of the upper pressurizing lever 29 is pushed up, the release is biased by the spring 33. The lever 31 rotates, and the upper pressure lever 29
By engaging with the hook bin 32, the pressurized state is restored again.

In the above-mentioned manual pressure release and automatic repressurization, the repressurization means is provided on the same axis as the gear 38 with partially missing teeth and the pressure cam, as shown in FIG. Due to the lack of teeth in the gear, the drive to the pressure cam is cut off, and the pressure cam is in a stopped state. When the pressure is released, the toothless gear 38 is rotated by the pressure cam 36, and the gear portion meshes with another gear series 39 of the fixing device. Then, when the device is restarted, the gear 38 rotates and the pressurizing cam 36 is rotated to automatically perform the above-mentioned repressurizing operation. The pressure cam operation stops and a pressurized state is established. In other words, in this embodiment, by prohibiting the opening of the paper ejection section, the exposure of the fixing film 5 can be suppressed to the minimum, preventing film damage, etc., and by providing pressure release, it is possible to The pressure for pulling out the JAM paper can be reduced, and further damage to the fixing film 5 can be eliminated. Further, in this embodiment, no driving/disconnecting means such as a coupler arm is provided between the fixing device and the main body. This is because rotating the upper fixing roller during JAM processing as in the conventional heat roller method means rotating the thin fixing film 5 in this embodiment.
This is because the fixing film 5 may be torn depending on the direction in which the AM paper is pulled out, and furthermore, it may move in the thrust direction and deviate from the image conveyance area, or if it has shift control, it may jump out of the control area. Because there is also
As a countermeasure, we eliminated the drive cutting means from the main body side,
When the pressure is released, the fixing film 5 is not rotated even during JAM processing.

Further, in this embodiment, measures against condensation against water vapor generated from the recording material are implemented.

In this fixing method, the heating element 1 with a low heat capacity achieves a rapid rise to a predetermined temperature, but on the other hand, the pressure member 24
Since the recording material is transported while the drive roller 6 and the drive roller 6 are kept at a low temperature, especially if the recording material itself has absorbed moisture, a large amount of moisture is inevitably released, and dew condensation occurs in the low-temperature areas mentioned above. , this water droplet has the disadvantage that it disturbs the image. Therefore, in this embodiment, as shown in FIG. 1, air vent holes 26a are provided in the separation guide 26 and the like to form an air path for venting the air around the pressure member 24. The air passage prevents water vapor from being trapped around the pressurizing member 24, and at the same time, in this embodiment, a forced air venting means (fan) is provided on the main body side of the apparatus to discharge water vapor to the outside of the apparatus.

Further, a sheet 40 for collecting water droplets is provided at the bottom of the pressure member 24.
This design not only absorbs ambient steam but also prevents the equipment from tipping and spilling out of the equipment if a large amount of water comes out.This further improves the effectiveness against condensation. ing. Similarly, on the upper unit side, a vent hole 28a is provided in the paper ejection cover, etc., to provide the effect of venting the air around the fixing film 5. In this case, the fixing film 5
A similar effect can be obtained by discharging the surrounding air to the outside or suctioning it with a fan, or by blowing or circulating air that has been heated to a certain degree through the device.

Next, the attachment of the present fixing device to the main body of the image forming apparatus will be explained.

As shown in FIG. 9, the drive is fixed at three points: two on the back side (see the arrow on the left) and one on the front side (see the arrow on the right), which receive the drive from the main body. This is because in this embodiment, the shift of the fixing film 5 is controlled.
This is because it is necessary to minimize the bending of the fixing device, and by having three points, it is advantageous for the seating area on the main body side and twisting, and even when the device itself is placed on uneven ground. The influence on the fixing device can be minimized. Also, the reason why there are two points on the drive side is because when power is applied from the main body side, twisting force is inevitably applied to the fixing device in a certain direction, so that the above-mentioned twisting on the upper unit 18 is minimized. Therefore, it is desirable that the mounting unit be located directly below the side plate of the upper unit 18 in the vicinity where the driving force can be obtained, and that the rigidity of the mounting portion be increased. As for the other point, by locating it near the center of gravity of the device as done in this embodiment, it is possible to suppress the effects of drops or vibrations, and to reduce twisting of the upper unit 18. . In addition, when mounting on the 1-point side, the seat surface can have a large influence, so it is necessary to make it a spherical surface or the like and fix it via an elastic member. It is also desirable to have a shape that does not undergo twisting.

Regarding the stability of film transport performance, in addition to the above-mentioned shift control, since the fixing film 5 is a thin film and is made of a non-elastic material, it is necessary to take measures against wrinkles, small waves, folding, etc. of the fixing film 5. be. First, since wrinkles and small waves create non-uniform conditions on the fixed image, the shape of the fixing film entrance side and discharge side of the holding member 2 is adjusted so that the film itself has both sides in the longitudinal direction, as shown in FIG. The crown shape is inflated by about 0.2 mm to prevent concave so that force is applied to push it apart. In this case, if the crown amounts X, X are too large, the elasticity of the fixing film 5 is small, causing both ends to sag and causing the opposite effect, so it is desirable that the amount of crown snow is 0.8 rnm or less.

Also, as shown in Figure 11, the heating element can be mounted on the surface as well.
A downwardly convex crown is formed in a direction perpendicular to the conveying direction of the fixing film. In this example, 0.
A medium convex crown of 1 to 0.3 mm is formed by the holding member. This can prevent the fixing film from folding back. It is desirable that the heating element crown has the largest crown at the center of its longitudinal direction, and if it is uneven or has large roundness or irregularities in some areas, film folding will occur, so it is necessary to manage this.

Furthermore, since the heating element 1 is an alumina substrate as described above, alumina is generally difficult to process, and the ends of the substrate are in an edge state. Therefore, in order to protect the fixing film 5 from rubbing, as shown in FIG. It is necessary to prevent this, but in this case, the amount of snow, etc. must be set to prevent the pressure member from riding on the holding member 2.

Next, recording material conveyance performance will be explained.

Due to the crown of the heating element 1 described above, if the amount of convexity in the center is too large, a force will be generated that pulls the recording material toward the center, resulting in frequent wrinkles in the recording material. Therefore, in this embodiment, as shown in FIG. 11, an attempt was made to prevent the above-mentioned wrinkles by using an inverted crown-shaped pressure roller as the pressure section to squeeze the recording material to both sides.

FIG. 13 is a perspective view of the heating body 1 and the pressure member 24. However, if the inverted crown of the pressure member 24 is large, the pressure applied to the recording material will be too strong, and after the recording material enters the fixation zone, the trailing edge of the recording material will spring up, causing an unfixed toner image to be deposited inside the main body. This caused the defect of rubbing and disorder. Therefore, the plane of the heating body is tilted with respect to the pressure member 24, and the angle (nip angle γ in FIG. 1) between the plane of the heating body and the horizontal plane is set to 8.
．． Although the angle was set at 5° to force the recording material downward, it was not sufficient, so as shown in FIG. By making the recording material incident angle larger than the above nip angle,
Furthermore, while pressing the recording material downward, the heating element 1
A range of 0.1 to 0.3 mm for the crown of the pressure member 24 and 0.05 to 15 mm for the inverted crown of the pressure member 24 is set as a countermeasure against wrinkles of the recording material and rear end flip-up.

Furthermore, in consideration of the worst case, in this embodiment, a spur member for holding down the trailing edge of the recording material is attached to the fixing device. The spur member is normally biased by a spring to the recording material holding position, and during JAM processing, the spur member is pressed against the recording material to prevent damage to the recording material.
The structure is such that it rotates in an escape direction in the direction in which the M is pulled out, and returns to its normal position by the above-mentioned spring after processing.

The crown amount of the heating element, the reverse crown amount of the pressure member, the nip angle, and the recording incidence angle (the amount of snow on the holding member) relative to the nip angle described above are set depending on each device, conveyance route, and recording material used. However, by simply setting these conditions, it is possible to solve the problem of wrinkles and conveyance of the recording material, and it is possible to create an inexpensive and compact fixing device without adding any other parts or complicating the structure. This is an effective method for achieving this.

Now, regarding the setting of separation conditions in this example, the first
Distance A from the center of the nip to the bent part of the fixing film 5 in the figure
is 6.5 mm, the radius of curvature B of the bent portion is 1.5 mm, and the bending angle θ is 50°. Note that the distance from the center of the nip to the bent portion is 3.5 mm (772 mm,
Furthermore, considering the moldability and strength of the holding member 2, it is set to 3 mm, so 3.5 + 3 = 6.5 (mm), so this can be set freely depending on the heating element width and the holding member material. Similarly, the radius of curvature of the bent portion can be set freely. Further, as described above, the bending angle is set depending on the curl removal performed by the paper ejection section, the size of the apparatus, and the ejection path, and is not limited. However, if the bending angle is less than 35°, the recording material may not separate properly and become entangled, or it may be difficult to position the paper ejection section above the nip during mounting, resulting in an increase in the size of the device or the decurling mechanism. An addition is necessary.

[Effects of the Invention] As described above, according to the present invention, since the coefficient of friction between the drive roller, which is the drive means, and the fixing film is maximized, stable driving of the fixing film is realized. Furthermore, even when performing deviation control, the film deviation force on the drive roller becomes dominant, and therefore stable driving on the drive roller and grip force in the longitudinal direction are stabilized, so that there is no possibility of harming the driving condition. This makes it possible to restore the misaligned film, and has the effect of preventing the film from folding over itself.

[Brief explanation of drawings]

FIG. 1 is a side sectional view showing an embodiment of the present invention, FIG. 2 is an enlarged detailed side view of the heating body, holding member, and contact points of the fixing device shown in FIG. 1, and FIG. 3 is also a fixing film shift control 4 is a side view of the structure of the control means shown in FIG. 3; FIG. 5 is an enlarged perspective view of the fixing film unit of the fixing device shown in FIG. 1; FIG. 6 is the unit shown in FIG. 5. FIG. 7(a) is a perspective view showing a method of combining the lower unit and the lower unit. (b) is an enlarged side view of the pressure release mechanism of the fixing device shown in FIG. 1, FIG. 8 is an explanatory diagram of the repressurization drive mechanism, and FIG. 9 is a fixation form of the fixing device shown in FIG. 1 to the main body. , FIG. 10 is an enlarged illustration of the shape of the holding member of the fixing device in FIG. 1, FIG. 11 is an enlarged illustration of the crown shape of the heating body and the pressure section, and FIG. FIG. 13 is an enlarged perspective view showing a state in which the heating body and the pressure member are in pressure contact with each other. 1... Heating body 2... Holding member 4...
Contact 5... Fixing film 6... Drive roller 6a... Elastic/insulating layer 7... Tension roller 8... Detection lever (Figure 1) 0 Figure 2 and 4 others Figure 3 Figure 7 Figure Figure 9 d Normal state when pressurization is released Figure 0 Figure 2

Claims (1)

[Claims] 1. A fixing device that heats and fixes an unfixed toner image on a recording material by having a pressure member that brings the recording material into close contact with the heating body through a thin fixing film that is driven while being in pressure contact with the heating body. , a driving means for the fixing film includes a drive roller and a roller for a purpose other than driving, and the friction coefficient between the fixing film contact surface of the drive roller and the fixing film is such that the friction coefficient between the fixing film contact surface of the other roller A fixing device characterized in that the coefficient of friction is greater than that between the fixing film and the fixing film.