JP4878464B2 - Fixing device - Google Patents

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a copying machine, a facsimile, or a printer that forms an image on a recording material by using an electrophotographic method, and a fixing device thereof, and more particularly from a toner having a release agent. The present invention relates to a belt nip type fixing device for fixing an unfixed image.

  2. Description of the Related Art Conventionally, a roller fixing device is known as a device that heats and melts and fixes an unfixed toner image carried on a recording sheet. A fixing roller that is rotatably supported and a pressure roller that is also rotatably supported are pressed against each other, and a recording sheet is fed between them and heated and pressed to fix.

  Also, a belt nip type fixing device in which an endless belt is used to widen the fixing nip has been proposed. A method in which a heat fixing roller rotatably supported and a pressure belt capable of endless movement are pressed against each other, and a recording sheet is fed and fixed between them is called a belt nip method.

  Patent Document 1 proposes a method in which an endless belt is wound around a fixing roller to widen a fixing nip, and a pressure roller is provided inside the endless belt to apply pressure.

In Patent Document 2, not only a pressure roller (or “separation roller” in the present invention) but also a pressure applying member is provided inside the endless belt and attempts to prevent image defects by being pressed against the fixing roller. There is also a configuration to do.
A belt-nip type fixing device as in Patent Document 2 will be described in detail with reference to FIG.

  A fixing roller 51 that is rotatably arranged, an endless belt 52 that is stretched between a plurality of rollers 55, 56, and 57 and presses against the fixing roller 51, and a pressure applying member 100 that pressurizes the endless belt to the fixing roller 51. (Or referred to as “pressure pad”).

  The fixing roller 51 has a configuration in which an elastic body layer such as silicone rubber or fluororubber is coated on a metal core made of Al, Fe or the like. The endless belt 52 has a configuration in which an elastic body layer such as silicone rubber or fluorine rubber is coated on the surface of a base material made of a resin such as polyimide or a metal such as nickel.

  Further, a cleaning device (not shown) is attached to the fixing roller 51, and the toner or the like offset on the fixing roller 51 may be cleaned by the cleaning device.

  In some cases, silicone oil or the like as a release agent is applied to the fixing roller 51 by the release agent applying device, so that the recording material P can be easily separated from the fixing roller 51 and toner offset can be prevented. is there. However, since uneven application of silicone oil results in uneven gloss on an image, recently, a so-called oilless fixing device in which toner contains a release agent and does not include a release agent application device is becoming mainstream. In such a case, a release layer made of a fluororesin or the like may be provided outside the fixing roller elastic layer.

  The endless belt 52 is provided with an elastic layer such as silicone rubber or fluorine rubber on the outer periphery of a heat resistant resin such as polyimide or a cylindrical base material such as SUS. Similar to the fixing roller, when the toner contains a release agent, a release layer may be provided outside the endless belt elastic layer, or there may be only the base material and the release layer without the elastic layer.

The pressure applying member 100 has an elastic layer 101 such as silicone rubber on a metal base plate 102 and a low wear layer 103 such as PTFE on the surface layer.
A roller 56 is a separation roller made of a metal such as SUS and presses the endless belt 52 so as to bite into the fixing roller 51, thereby deforming the elastic body of the fixing roller 51 and separating the recording material P from the surface of the fixing roller 51. Yes.

  The roller 57 is provided with a high friction coefficient layer on the surface layer of a metal core such as SUS, and swings to control the shift of the endless belt. In some cases, it also serves as a tension roller that applies tension to the endless belt.

  A heater 58 such as a halogen lamp is disposed inside the fixing roller 51. Further, a thermistor (not shown) is disposed in contact with or not in contact with the fixing roller 51, and the temperature of the surface of the fixing roller 51 is adjusted by controlling the voltage to the heater 58 through a temperature adjusting circuit. Yes.

  In addition, this belt nip type fixing device reduces the peak pressure by forming a wide fixing nip, thereby reducing the rubber deformation of the fixing roller and extending the service life. Also, by lowering the fixing temperature, energy can be saved. There are many advantages such as

  Since the fixing roller and the separation roller (or pressure roller) are pressed against each other at a predetermined pressure, depending on the pressure, the diameter of the member, the thickness of the member, the physical property (Young's modulus), etc. It bends so that the pressure of the part is released. Therefore, when the fixing roller and the separation roller have a so-called straight shape in which the diameter in the axial direction is the same at any position, the nip shape formed by the separation roller that applies pressure to the fixing roller via the endless belt is: It becomes as follows. That is, the nip shape in this case is such that the nip width is narrowed by the amount of deflection at the center of the pressing portion, and the nip width gradually increases toward both ends of the pressing portion.

Thus, it has been found that when the nip shape is narrow at the center and wide at both ends, problems such as a decrease in peelability of the recording material occur depending on the narrow portion of the nip. For this reason, the fixing device described in Patent Document 3 uses a so-called regular crown-shaped roller in which the diameter of the central portion of the pressure roller 56 is thicker than the end as a method of aligning the nip width in the axial direction. .
Japanese Unexamined Patent Publication No. 5-150679 JP 11-045025 A Japanese Patent Laid-Open No. 10-228199 JP 2001-201979

  However, when the present inventor fixes with the same configuration as described in Patent Document 3, the recording material does not peel off and the paper wrinkle does not occur, but the endless belt wavy. When the recording material is conveyed to the entrance of the fixing nip due to the undulation of the endless belt, the recording material is lifted by the endless belt, and an unfixed toner image is rubbed against the fixing roller, resulting in an image defect. Oops.

The wavyness of the endless belt is described in Patent Document 4 as follows. In FIG. 2, it is described that the waviness of the belt can be eliminated when the support roller groups 55, 56, and 57 that stretch the endless belt 52 satisfy the following relationship. That is, when the crown amount α of the separation roller 56, the reverse crown amount of the roller 55 is β, and the crown amount of the roller 57 is γ, three values are obtained:
[Α- (β + γ)] = 0
This is the case.

  However, the waviness of the endless belt in this phenomenon is caused by the fact that the pressure roller 56 having a large central diameter with respect to both ends in the axial direction is in pressure contact with the fixing roller 51 via the endless belt 52. In other words, since the rollers 55 and 57 are not in pressure contact with the fixing roller 51, it is considered that the longitudinal speed difference of the endless belt cannot be corrected even when the crown is inverted.

  The inventor considers this cause as follows.

  As shown in FIG. 3, as shown in Patent Document 4, when the pressure roller is provided with a positive crown, the end portions of the endless belt are loosely tensioned and easily waved.

As shown in FIG. 4 (a), the rotational speed of the pressure roller is ω, the moving distance of the endless belt on the circumference of the pressure roller is Lc at the longitudinal center of the pressure roller, and Le at the end. Since the pressure roller has a positive crown, Lc> Le. However, since the belt is actually a rigid endless belt, the moving distance of the end portion of the pressure roller is Les (= Lc). That is, the pressure roller and the endless belt slide at the end so that Le → Les, or the fixing roller and the endless belt slide at the end.

  Or, conversely, as shown in FIG. 4 (b), the pressure roller and the endless belt may slip in the center so that Lc → Lcs, or the fixing roller and the endless belt may slip in the center. Conceivable.

  However, this phenomenon occurs because the pressure roller 56 having a large central diameter with respect to both ends in the axial direction is in pressure contact with the fixing roller 51 via the endless belt 52. Will occur regardless. Thus, even if the tension is increased by using the roller 57 as a tension roller, or correction is performed by attaching a reverse crown to the rollers 55 and 57, the wave of the endless belt cannot be eliminated.

  If the endless belt and the pressure roller are slid in an attempt to eliminate the undulation of the belt, it can be easily estimated that the endless belt itself slips.

  Accordingly, an object of the present invention is to solve the undulation of the endless belt and to prevent the endless belt from slipping at the same time.

In order to solve the above problems, the present invention provides a fixing rotator for fixing an image on a recording material, an endless belt for forming a fixing nip between the fixing rotator, and the endless belt in the fixing nip. A pressure pad for pressing toward the fixing rotator, and a separation part for suspending the endless belt and separating the recording material from the fixing rotator are formed. A fixing roller having a thicker pressure roller, the static friction coefficient between the fixing rotating body and the outer peripheral surface of the endless belt is μ1, and between the pressure roller and the inner peripheral surface of the endless belt. The dynamic friction coefficient is μ2, the dynamic friction coefficient between the pressure pad and the inner peripheral surface of the endless belt is μ3, the pressing force of the pressure roller to the fixing rotator is N1, and the pressure pad The pressure applied to the fixing rotator N2, the peripheral speed of the fixing rotator V1, when the peripheral speed of the pressure roller and V2, F1 = μ1 · (N1 + N2), F2 = μ2 · N1, F3 = μ3 N2, F1-F3> | F2 |, and V1 <V2 are satisfied.

  Moreover, you may make it have an application means which apply | coats a lubricant to the said belt inner surface.

  The surface roughness Rz of the pressure roller is preferably 5 μm or less.

As described above, in the fixing device according to the present invention, the static friction coefficient between the fixing rotator and the belt outer peripheral surface is μ1, the dynamic friction coefficient between the pressure roller and the belt inner peripheral surface is μ2, and the addition The dynamic friction coefficient between the pressure pad and the inner peripheral surface of the belt is μ3, the pressing force of the pressure roller to the fixing rotator is N1, the pressing force of the pressure pad to the fixing rotator is N2, and the fixing rotation When the peripheral speed of the body is V1 and the peripheral speed of the pressure roller is V2, F1 = μ1 · N1, F2 = μ2 · N1, F3 = μ3 · N2, F1-F3> | F2 |, V1 <V2. Therefore, the longitudinal speed of the endless belt sandwiched between the fixing roller and the pressure roller is closely conveyed with the fixing roller without any difference in peripheral speed, and the speed of the fixing roller is followed. It is designed so that it is not affected by the circumferential speed difference of the pressure roller while sliding with the roller. And it is intended to prevent the undulation by eliminating the peripheral speed difference between the length of the endless belt. Furthermore, the slip of the endless belt is prevented by further reducing the coefficient of friction between the pressure pad and the end belt.

  Further, if a toner having a release agent is used in order to realize the relationship of the friction coefficient, a release agent coating device on the fixing roller becomes unnecessary. If there is a release agent application device for applying silicone oil or the like, the friction coefficient between the fixing roller and the endless belt is lowered. Furthermore, if a lubricant such as silicone oil is applied to the inside of the endless belt, both the force received from the fixing roller and the force received from the separation roller are unstable during the rotational driving of the endless belt, and slipping tends to occur. By using a toner having a release agent, a release agent coating device is not required for the fixing roller, so that the driving of the endless belt can be stably received from the fixing roller. For this reason, it may be better to provide a resin layer such as fluorine on the surface layer of the fixing roller and the endless belt.

  Further, in order to make the friction coefficient between the inner surface of the endless belt and the pressure roller smaller than the friction coefficient between the fixing roller and the outer surface of the endless belt, the surface roughness of the surface of the pressure roller is set to 5 μm or less. This is because if the surface roughness of the pressure roller surface is increased, the coefficient of friction with the endless belt increases, and the waviness deteriorates. By applying a lubricant to the inner surface of the endless belt, waviness can be more easily eliminated.

  In addition, if the fixing belt is used as a fixing rotating body having a heat source instead of a fixing roller, a wider fixing nip width can be obtained, which may be advantageous for downsizing the fixing device.

  Hereinafter, the present invention will be described more specifically with reference to examples. Although these examples are examples of the best mode of the present invention, the present invention is not limited to these examples.

<First fixing device>
The fixing device 1 according to the present invention will be described with reference to FIG. In the following description, the same members as those described above are denoted by the same reference numerals.

In FIG. 2, the fixing roller 51 is formed by forming 0.5 mm of silicone rubber on a core metal made of 0.3 mm thick Fe having an inner diameter of φ37.8 and an outer diameter of φ38.4, and a 30 μm thick PFA tube on the surface thereof. A fixing roller having a straight shape in the longitudinal direction of the coated outer diameter φ40 was used.

The fixing belt (or “endless belt”) 52 used was a seamless belt having an outer diameter of φ90, in which a silicone rubber layer was coated with a thickness of 0.5 mm on a polyimide base layer having a thickness of 100 μm. The fixing belt 52 is stretched around three rollers: an entrance roller 55, a separation roller 56, and a tension roller 57. The entrance roller 55 is a roller at the entrance of the fixing device and is a place where the recording material enters, and is fixed so as not to change the conveyance path of the recording material. The tension roller 57 is biased by a spring so as to apply tension to the fixing belt 52.

The separation roller 56 is a solid roller of SUS and presses the endless belt 52 so as to bite into the fixing roller 51 to deform the elastic body of the fixing roller 51 to separate the transfer paper P from the surface of the fixing roller 51. In this example, an outer diameter of 15.5 mm at the center in the longitudinal direction and a positive crown of 500 μm with 15.0 mm at both ends, and a total pressure of 50 kg was applied. The separation roller is rotationally driven from a driving source (not shown) so that the peripheral speed is substantially equal to that of the fixing roller and the endless belt.

The pressure applying member 100 is formed by laminating an elastic layer 101 made of silicone rubber having a rubber hardness Hs of 30 ° and a low friction layer 103 made of glass cloth sheet coated with PTFE on the surface of a stainless steel base plate 102 having a thickness of 5 mm. Formed. The pressure applying member 100 is pressed toward the fixing roller 51 by a spring (not shown) arranged on the base plate 102 side.

  In this example, the pressure application member was pressurized to a total pressure N2 = 50 kg. For this reason, when the pressure applying member 60 kg and the separation roller N1 = 50 kg, the total pressure is 100 kg.

  As the lubricant application device 104, a heat-resistant nonwoven fabric is used, and silicone oil is applied as a lubricant.

  The process speed (circumferential speed) of the fixing roller was 300 mm / sec, and the peripheral speed of the separation roller was 310 mm / sec.

<Second fixing device>
The fixing device 21 according to the present invention will be described with reference to FIG. In the following description, the same members as those described above are denoted by the same reference numerals, and the same members are used, so that the description thereof is omitted.

  The second endless belt 105 was the same as the endless belt 52. Only the fixing roller 51 of the second fixing device was an elastic layer and a core metal having no surface layer.

<Friction coefficient>
As a comparative example for examination by the present inventors, the first and second fixing devices were removed from the lubricant application device, the separation roller surface roughness Rz was 1 μm, 5 μm, 10 μm, and the low A pressure applying member having no wear layer 104 was used.

As shown in FIG. 7, the friction coefficient is measured by placing an endless belt cut open on the hot plate 107 adjusted to 170 ° C. with the front or back side, and the fixing roller 51 or the separation roller 56 or This is performed with the pressure applying member 100 placed. In this state, the force gauge 108 was connected and pulled in the direction of the arrow in the figure, and the static friction coefficient was calculated by reading the force when it started to move, and the dynamic friction coefficient was calculated by reading the force after starting to move. Measurement was also performed with and without application of lubricant between the endless belt 52 and the separation roller 56 or the pressure applying member 100. As shown in Fig. 1, the friction coefficient is μ1 for the static friction between the surface of the fixing roller and the outer peripheral surface of the endless belt, μ2 for the dynamic friction coefficient between the separation roller and the inner peripheral surface of the endless belt, and between the pressure applying member and the inner peripheral surface of the endless belt. The dynamic friction coefficient was set to μ3.

F1, F2, and F3 are defined as follows from the friction coefficients μ1, μ2, and μ3 and the applied pressures N1 and N2 of the separation roller and the pressure applying member. That is, as shown in FIG. 8A, the force by which the fixing roller drives the endless belt is defined as F1 = μ1 · (N1 + N2). The force with which the separation roller drives the endless belt is defined as F2 = μ2 · N1. Further, F3 = μ3 · N2 is defined as a force for the pressure applying member to rub against the endless belt to stop the endless belt.

  The following comparative experiments were conducted with the first and second fixing devices described above.

The fixing conditions were such that the surface temperature of the fixing roller was adjusted to 170 ° C. The conditions for the recording material to be passed and the unfixed toner were fixed by placing an unfixed solid image on plain paper 64 g / m ² .

  Tables 1 and 2 show friction coefficients μ1, μ2, and μ3, endless belt undulations, solid image rubbing traces, and belt slip in the first and second fixing devices.

ベルト波打ち／画像擦れ、ベルトスリップ欄
〇：ベルトの波打ち、画像の擦れ跡が無い。
または、ベルトスリップによる画像ずれが無い。
△：ベルトの波打ち、画像の擦れ跡が軽微に有る。
×：ベルトの波打ち、画像の擦れ跡が有る。
または、ベルトスリップによる画像ずれが有る
-：ベルトスリップによる画像ずれがあり、
ベルトの波打ち、画像の擦れ跡が有るかどうか分からない。
判定欄
OK：F1-F3＞｜F2｜
N：F1-F3＜F2
S：F1-F3＜-F2 （ F1+F2＜F3 ）

Belt waving / image rubbing, belt slip column ◯: No belt waving, image rubbing trace.
Or, there is no image shift due to belt slip.
Δ: There are slight undulations of the belt and rubbing traces of the image.
X: There is a wave of the belt and a rubbing trace of the image.
Or there is image shift due to belt slip
-: There is image shift due to belt slip,
I don't know if there are wavy belts or rubbing marks on the image.
Judgment column
OK: F1-F3> | F2 |
N: F1-F3 <F2
S: F1-F3 <-F2 (F1 + F2 <F3)

From the results of Comparative Examples 5 and 6 in Table 1, it can be seen that the belt slip occurs when F1-F3 <-F2 (determination S). This is a case where F1 + F2 <F3 in FIG. 8A, and the driving force of the endless belt has lost the braking force.

  From the results of Examples 1 and 2 and Comparative Examples 1 to 4 in Table 1, it can be seen that it is better to reduce the surface roughness of the separation roller. Moreover, from the results of Example 1 and Comparative Examples 2, 5, and 6, it can be seen that it is better to apply the lubricant than not to apply the lubricant, and it is better to not apply the fluorine coating to the surface of the pressure applying member. In this case, it can be seen that the waviness of the belt and image blurring occur when F1-F3 <F2 (determination N). That is, in the case of F1 <F2 + F3 in FIG. 8A, the endless belt is rotated by the driving force of the separation roller, and the fixing roller and the endless belt are slipping.

Examples 1, 2 and 3 in Table 1 are F1-F3> | F2 | (determination OK), that is, in the case of F1-F3> F2 and F1-F3> -F2, the slip of the belt is also In this state, no undulation occurs. That is, the endless belt does not slip because the drive from the fixing roller and the separation roller is superior to the brake force from the pressure applying member because of the relationship of F1 + F2> F3 (F1-F3> −F2). In addition, from the relationship of F1> F2 + F3 (F1-F3> F2), the driving force from the fixing roller of the endless belt is superior to the driving force of the inner surface of the belt. Therefore, it is considered that the wavyness of the belt is generated due to a speed difference in the length of the endless belt as described above in a state where the speed of the endless belt is equal to the speed of the fixing roller.

In addition, when the separation roller stopped rotating and was driven to rotate by the endless belt, slip occurred even if it did not slip in Table 1. Further, when the separation roller was driven to rotate and the peripheral speed was reduced to less than 300 mm / sec, slipping occurred again. In this case, as shown in FIG. 8B, the force F2 at which the separation roller drives the endless belt is applied in the direction opposite to the rotation direction of the endless belt, and the braking force is generated instead of the driving force. it is conceivable that.

  From this result, it is considered that the separation roller assists the rotational drive of the endless belt by dynamic friction while having a circumferential speed difference (sliding) with the endless belt.

As described above, by satisfying the relationship of F1-F3> | F2 |, it is possible to prevent the endless belt from slipping, wavy and image blurring.

In addition, by making the endless belt and the separation roller easy to slide, it is advantageous for endless belt shift control. In the case where the roller 57 is a shift control roller, the roller 57 moves so that the endless belt approaches the longitudinal center at an angle according to the position in the longitudinal direction of the endless belt. In that case, since the above-mentioned μ2 and μ3 serve as a braking force with respect to the shift force by the shift control roller 57, the shift force is more effective by making the endless belt and the separation roller easy to slide, and for the shift control of the endless belt. Is also advantageous.

  Further, in this example, the endless belt that is wound around three rollers has been described. However, if there are a separation roller and a pressure applying member, the belt can be wound around two rollers or only the separation roller and the pressure applying member. May be.

  The fixing device of the present invention is not limited to the use for fixing the unfixed toner image formed on the recording material as described above. In other words, the fixing device of the present invention is used for the purpose of assuming a toner image in order to improve the glossiness of an image formed on a recording material, or by reheating a toner image that has already been assumed. It can also be used as an application to improve the quality. In this example, these are collectively referred to as a fixing device.

<Image forming apparatus>
The overall configuration of the image forming apparatus including the fixing device according to the embodiment of the present invention will be described with reference to FIG.

  In the apparatus shown in FIG. 9, first, second, third, and fourth image forming portions Pa, Pb, Pc, and Pd constituting the image forming means are provided together, and toner images of different colors are latent in each. Formed through image, development and transfer processes.

  Each of the image forming portions Pa, Pb, Pc, and Pd includes a dedicated image carrier, in this example, electrophotographic photosensitive drums 303a, 303b, 303c, and 303d, and each color is provided on each photosensitive drum 303a, 303b, 303c, and 303d. The toner image is formed. An intermediate transfer member 1130 is installed adjacent to each of the photosensitive drums 303a, 303b, 303c, and 303d. The toner images of the respective colors formed on the photosensitive drums 303a, 303b, 303c, and 303d are primarily transferred onto the intermediate transfer member 330 and transferred onto the recording material p at the secondary transfer unit. Further, the recording material p onto which the toner image has been transferred is fixed to the toner image by heating and pressing in the fixing device 1 and then discharged out of the device as a recorded image.

  Drum chargers 302a to 302d, developing devices 301a to 301d, primary transfer chargers 324a to 324d and cleaners 304a to 304d are provided on the outer circumferences of the photosensitive drums 303a to 303d, respectively. A light source device and a polygon mirror (not shown) are further installed in the upper part of the device.

The laser light emitted from the light source device is scanned by rotating the polygon mirror, the light beam of the scanning light is deflected by the reflection mirror, and the photosensitive drums 303a, 303b,
The light is condensed and exposed on the buses 303c and 303d. As a result, latent images corresponding to the image signals are formed on the photosensitive drums 303a, 303b, 303c, and 303d.

  The developing devices 301a, 301b, 301c, and 301d are filled with predetermined amounts of yellow, magenta, cyan, and black toners as developers, respectively, by a supply device (not shown). The developing devices 301a, 301b, 301c, and 301d develop the latent images on the photosensitive drums 303a, 303b, 303c, and 303d, respectively, and visualize them as cyan toner images, magenta toner images, yellow toner images, and black toner images.

  The intermediate transfer member 330 is driven to rotate in the direction of the arrow at the same peripheral speed as the photosensitive drum 303.

The first color yellow toner image formed and supported on the photosensitive drum 303 a passes through the nip portion between the photosensitive drum 3 and the intermediate transfer member 330. In this process, intermediate transfer is performed on the outer peripheral surface of the intermediate transfer body 330 by the electric field and pressure formed by the primary transfer bias applied to the intermediate transfer body 330.

  Similarly, a magenta toner image of the second color, a cyan toner image of the third color, and a black toner image of the fourth color are sequentially superimposed and transferred onto the intermediate transfer body 330 to form a composite color toner image corresponding to the target color image. Is done.

  Reference numeral 311 denotes a secondary transfer roller, which corresponds to the intermediate transfer member 330 and is arranged in parallel and in contact with the lower surface portion. A desired secondary transfer bias is applied to the secondary transfer roller 311 by a secondary transfer bias source. Transfer of the composite color toner image superimposed and transferred onto the intermediate transfer body 330 to the recording material P is performed as follows. That is, the recording material P is fed from the sheet feeding cassette 300 to the contact nip between the intermediate transfer member 330 and the secondary transfer roller 311 through a registration roller 312 and a pre-transfer guide at a predetermined timing. At the same time, the secondary transfer bias is applied from the bias power source. The composite color toner image is transferred from the intermediate transfer member 330 to the recording material P by the secondary transfer bias.

  The photosensitive drums 303a, 303b, 303c, and 303d that have undergone the primary transfer are cleaned and removed of the transfer residual toner by the respective cleaners 304a, 304b, 304c, and 304d, and are subsequently prepared for forming the next latent image or less. The toner and other foreign matters remaining on the intermediate transfer member 330 are wiped by contacting a cleaning web (nonwoven fabric) with the surface of the intermediate transfer member 330.

  The transfer material P that has received the transfer of the toner image is sequentially introduced into the fixing device 1 or 21, fixed by applying heat and pressure to the transfer material, and then output through the paper discharge unit 363.

It is explanatory drawing explaining the friction coefficients (micro | micron | mu) 1, (mu) 2, and (mu) 3 of this invention. It is explanatory drawing which shows the structure of the fixing device of a prior art example, an Example, and a comparative example. It is explanatory drawing explaining the wavy of an endless belt. It is explanatory drawing explaining the wavy of an endless belt. It is explanatory drawing explaining the wavy of an endless belt. FIG. 3 is an explanatory diagram illustrating a configuration of a fixing device according to an embodiment. It is explanatory drawing explaining the measuring method of a friction coefficient. It is explanatory drawing explaining F1, F2, and F3 which are the driving force or brake force of the endless belt of this invention. 1 is a diagram illustrating an overall configuration of an image forming apparatus according to the present invention.

Explanation of symbols

1, 21: Fixing device 51: Fixing roller 52: Fixing belt (endless belt)
56: Separation roller 58: Halogen heater 100: Pressure applying member P: Recording material

Claims (3)

A fixing rotator for fixing the image on the recording material;
An endless belt forming a fixing nip with the fixing rotating body;
A pressure pad for pressing the endless belt toward the fixing rotator at the fixing nip;
A pressure roller that hangs around the endless belt, forms a separation unit that separates the recording material from the fixing rotator, and has a central portion in the rotation axis direction thicker than both end portions in the rotation axis direction; In the fixing device,
The coefficient of static friction between the fixing rotator and the outer peripheral surface of the endless belt is μ1, the coefficient of dynamic friction between the pressure roller and the inner peripheral surface of the endless belt is μ2, and the pressure pad and the inner peripheral surface of the endless belt are The dynamic friction coefficient is μ3, the pressing force of the pressure roller to the fixing rotator is N1, the pressing force of the pressure pad to the fixing rotator is N2, the peripheral speed of the fixing rotator is V1, and the pressing force If the peripheral speed of the roller is V2,
F1 = μ1 · ( N1 + N2) ,
F2 = μ2 · N1,
F3 = μ3 · N2,
F1-F3> | F2 |,
V1 <V2
A fixing device satisfying the requirements.   The fixing device according to claim 1, further comprising an application unit that applies a lubricant to an inner surface of the endless belt.   The fixing device according to claim 1, wherein a surface roughness Rz of the pressure roller is 5 μm or less.

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