JPH03241376A - Fixing device - Google Patents

Abstract

PURPOSE:To prevent inadvertent stop while a fixing film is driven and damage to the film and a heating body by setting the coefficient of friction between a contact surface of a driving roller and the fixing film to a specific range. CONSTITUTION:The fixing film 5 coated with fluorine resin, etc., is used as a releasing layer for a base layer, and driven by the driving roller 6, and the surface layer of the driving roller 6 is coated with a conductive silicone rubber layer 6a, etc. At this time, the coefficient of friction between the face where the driving roller 6 is in contact with the fixing film and the fixing film 5 is set at 0.3 - 3 range. Thus, while the fixing film is driven, optimum frictional driving power is obtained, the useless stopping is prevented, and moreover, the damage to the film 5 and the heating body 1 is prevented.

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] Conventionally, a fixing device used in this type of image forming apparatus has 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] However, in such a fixing device, in order to shorten the startup time to a predetermined temperature, a heating element with a low heat capacity and a thin heat-resistant film of less than 40 μm (for example, (polyimide, polyetherimide, etc.), and the recording material is brought into close contact with a pressure member and fixed by heating.

Further, the heating body is fixed, is pressed against the film pressing member, and must be driven while rubbing the surface of the fixed heating body. Therefore, conditions must be set to ensure that the drive roller grips the film. Also, lubricating grease may be added to prevent chatter on the surface of the heating element. Furthermore, under elevated temperature conditions,
Naturally, the friction coefficients of both the drive roller and the film decrease. As described above, it is necessary to reliably drive the film in response to all the various conditions.

Here, there is a problem that both the film and the heating element are damaged, such as the film stopping when energized, and if a drive roller with an abnormally large gripping force is used, the film itself is thin and the film itself is damaged. There is a problem in that the film folds back due to the generated shifting force.

The present invention attempts to solve these problems. That is, the present invention can prevent damage to the film and heating element due to film stoppage, and
It is an object of the present invention to provide a fixing device that can prevent film wrinkles and tears caused by folding the film.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides a method for applying pressure to bring 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 that heats and fixes an unfixed toner image on a recording material, the fixing device having a drive roller as a drive means for the fixing film, and a contact surface of the moving roller with the inner surface of the fixing film. A drive roller having a contact surface with a friction coefficient of 0.3 to 3 between the fixing film and the fixing film was provided.

[Function] According to the present invention, the coefficient of friction between the fixing film contact surface of the drive roller and the fixing film is in the range of 0.3 to 3, so that the friction coefficient is high while driving the fixing film. Driving force is obtained, there is no need to stop inadvertently, and the phenomenon of folding of the fixing film is prevented.

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

In the figure, 1 is the surface layer of the alumina substrate (thickness 1 mm,
It is a low heat capacity heating element with a width of 7 mm) overcoated with a resistive 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 body 1 with a silicon 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 the heating element substrate is made of alumina, so the end face inevitably becomes an edge 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 18.4vn and a surface layer with a thickness of 75mm.
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 making the tension roller thicker and arranging the center of the drive roller 6 higher than the center of the tension roller rough, 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 mm, and the winding angle α of the fixing film 5 with respect to the drive roller 6 is set at 141.8°. 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, thereby creating pressure contact with the surface of the fixed heating element 1. This is to prevent torque increase due to chatter, vibration, and sticking between the fixing film 5 and the fixing film 5 which is driven by sliding. Further, 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 and 3.
Since it is a thin film, it is an appropriate value to prevent folding and flaring, and this value is a necessary design value even when no grease is used.

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 turns on the sensor 9 intermittently. Then, the shift direction and shift control area are determined based on the change in time of this 0N10FF.

Next, as shown in FIG. 344, the shift direction is changed by making the bearing 10 of the tension roller 7 movable in the vertical direction and moving it up and down by the swingable control arm 11. A latching solenoid 12 is provided as a vertical movement drive means to operate in conjunction with the control arm 11. When the above-mentioned sensor 9 outputs a reversal signal, the latching solenoid 12 is actuated to move the control arm 11 up and down, thereby causing the tension roller 7 to move up and down. It is linked. Also bearing 1
0 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 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 1
The biasing force of 4 is set to be zero. this is,
This is a means to effectively apply the biasing force of the spring against the attraction force of the latching solenoid 12 only when pulling up or dropping it, increasing the stroke of the latching solenoid 12, and making it possible to move up and down with a more compact solenoid and less electric current. be. 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■ in the height direction.

Also, the eccentric direction may be horizontal, 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 deviation 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. The outer diameter is 2011 and the hardness is approximately 40°.
The composition is as follows. The recording material is guided to the nip by an entrance guide 25, and is guided to the outside by a separation guide 26 to prevent the recording material from being caught in the pressure member 24. In this fixing method, as mentioned above, since the heating body 1 has a low heat capacity, it quickly rises and has the advantage of being able to fix the material. There is a drawback that the temperature difference increases and the amount of curl increases. In particular, in the apparatus of this embodiment, since the downward curl is large, the pair of discharge rollers 27 is set higher than the recording material separation point to correct the curl. 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.
Fixing film 5 may be damaged or some foreign object may fall onto it.
This is to prevent damage to the Calorie pressure 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 each front stem. Next, the release lever 31 is rotatably configured to engage with the hook pin 32 of the upper pressure lever 29, and is biased by a spring 33 in the direction of engagement with the hook pin 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, 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 with the lower pressure lever 30, the pressure member 24 is separated from the heating body 1.

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 pin 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 twisting to the fixing device, and by having three points, it is advantageous for the accuracy of the seating surface on the main body side and against 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 one point side, the seat surface can have a large influence, so it is necessary to make it a spherical surface and fix it via an elastic member, or to install it on the main body side by installing a rotating part on the fixing device side. 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 mm 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 roll-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 recording material was pressed downward at 5°, it was not sufficient, so the holding member 2 on the recording material entrance side was made to have a downward convexity than the ejection side, that is, Δ, Δ, as shown in Figure 12. Then, the incident angle of the recording material is made larger than the above nip angle, and the recording material is further pressed downward, and the crown of the heating member 1 is 0.1 to 0.3 mm, and the inverted crown of the pressure member 24 is 0.05 to 0.3 mm. The range is set to 0.15 mm as a measure against wrinkles of the recording material and the rear edge of the recording material being raised.

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 amount of crown of the heating element, the amount of reverse crown of the pressure member, the nip angle, and the recording material incidence angle with respect to the nip angle (the amount of snow on the holding member) described above are each set depending on each device, the conveyance route, and the recording material used. Although these are numerical values, it is possible to solve the wrinkles and transportability of the recording material simply by setting these conditions, creating an inexpensive and compact fixing device without adding other parts or complicating the structure. This is an effective method.

Now, regarding the setting of separation conditions in this example, the first
Distance 11 from the center of the nip to the bent part of the fixing film 5 in the figure
1A is 6.5a+m, bending part curvature radius B is 1.5mm
, the bending angle θ is 50''.The distance from the nip center to the bending part is
Since the width dimension of is 7mm and the heating resistor layer is located in the center,
From the center of the heating element to the end surface of the heating element: 3.5mm (7/2
mm), and further considering the moldability and strength of the holding member 2, 3.5 + 3 = 6.5 (mm)
Therefore, this can be freely set depending on the width of the heating element and the material of the holding member, and the radius of curvature of the bent portion can also 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.

In order to increase the friction coefficient between the drive roller 6 and the fixing film 5 in the present invention, the roller core (metal) is used in this embodiment.
HTV silicone rubber 6a with carbon on the surface (surface layer)
(elastic/insulating layer) is spray coated with a thickness of 75 μm to prevent friction on the surface, thereby minimizing unevenness and increasing the contact area and adhesion with the fixing film 5. Obtaining the coefficient of friction. In addition, a rubber layer with a thickness of about 1 to 2 + n + n is baked on the surface of the core metal,
When using a rubber roller with a polished surface, it is approximately 0.8 to 1
．． It was possible to obtain a friction coefficient of about 2. Furthermore, by intentionally roughening the rubber surface to form a wedge-shaped surface, it is possible to increase the above value by about 10 to 15%, but care must be taken to prevent changes in the coefficient of friction due to durable wear. be. Alternatively, by blasting the surface of the drive roller 6 or adhering alumina powder to provide unevenness on the surface, the unevenness can be dug into the fixing film 5 by 0.3~ Although it is possible to obtain a friction coefficient of about 0.6, since the fixing film 5 is a thin film, it is necessary to consider damage to the film 5. Also, since it is a heat fixing device, the drive roller 6 is also
The temperature is raised to about 150°C. Since the above-mentioned friction coefficient decreases by about 20 to 50% due to this temperature increase, it is necessary to set the friction coefficient in consideration of the fixing temperature control temperature and the temperature increase level of the drive roller section. Furthermore, as described in the explanation of this embodiment, in a device that applies heat-resistant grease (such as fragrant fruit) as a countermeasure against chatter and vibration of the fixing film 5 on the surface of the heating element, the influence of the grease must be considered. Must be.

Additionally, as the grease gradually lubricates the surface of the drive roller 6 over time, in order to guarantee performance even after durability,
After durability, even the grease lubrication system must maintain a good friction coefficient. From this point of view, the above-mentioned uneven roller has the advantage that since grease accumulates in its concave portions, it does not affect the actual fixing film contact surface (convex portions). Incidentally, in the fixing device according to the embodiment of the present invention, silicone rubber spray coating ensures a temperature of about 2.8 at the initial stage and 2 or more even in the heated state (150°C), and further,
In terms of durability, fluorine thread grease ensures a friction coefficient of 0.9 or higher even on the lower ridge of lubrication, making it possible to transport the fixed film in a stable manner that prevents film slipping and folding. It is also necessary to keep the surface roughness of the inner surface of the fixing film constant by controlling the manufacturing method and precision of the mold.

[Effects of the Invention] As explained above, according to the present invention, the friction coefficient between the fixing film contact surface of the drive roller and the fixing film is 0.
．． Since it is in the range of 3 to 3, a fast frictional driving force can be obtained, the fixing film will not stop unexpectedly while the fixing film is being driven, and damage to the film and the heating element can be prevented. This has the effect of preventing the film from being wrinkled or torn due to folding back.

[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 configuration of the control means in FIG. 1, FIG. 5 is an enlarged perspective view of the fixing film unit of the fixing device in FIG. 1, and FIG. FIG. 7(a) is a perspective view showing a method of combining the 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 7) Figure 3 (d) Normal state Pressure release Time 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 roller is provided as a driving means for the film, and a friction coefficient between the contact surface of the driving roller with the inner surface of the fixing film and the fixing film is 0.3.
A fixing device comprising: a drive roller having a contact surface of .about.3.