JP2004109583A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device which achieves higher peelability. <P>SOLUTION: Near the outlet of a nip part formed by a fixing roller 210 and an endless belt 220, a rigid body pressing member 238 presses a recording medium passing through the nip part in such a way that pressing force to both ends of the recording medium is made higher than that to the central part in the rotating shaft direction (X-axis direction) of the fixing roller 210 to enhance peeling performance and a peeling assistant member 262 suppresses curl of printing paper 42 in (-Z) direction caused by the enhanced peeling performance. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a fixing device used in an image forming apparatus using a toner, such as a copying machine, a printer, and a facsimile.
[0002]
[Prior art]
A fixing device that forms a nip portion by winding an endless belt around a heat fixing roller at a predetermined angle has been realized. In this fixing device, since a wide nip portion can be formed by winding an endless belt, the diameter of the heat fixing roller can be reduced.
However, the recording paper pressed by the heat fixing roller with such an endless belt hardly peels off from the heat fixing roller.
In view of this, there has been proposed a fixing device in which the heat fixing roller is locally strongly pressed in the vicinity of the exit of the nip portion to cause the heat fixing roller to be distorted, thereby facilitating the separation of the recording paper (for example, Patent Document 1 and Patent Document 1). Reference 2).
In some cases, paper wrinkles are prevented by increasing the pressure at the center of the heat-fixing roller in the direction of the rotation axis than at both ends (for example, see Patent Document 3).
[0003]
[Patent Document 1]
JP-A-11-133776 [Patent Document 2]
JP 2001-356625 A [Patent Document 3]
JP-A-2002-148981
[Problems to be solved by the invention]
The present invention has been made in view of the above background, and has as its object to provide a fixing device having higher releasability.
For example, when color printing is performed, a large amount of toner of a plurality of colors adheres to the recording paper, and it is particularly difficult to remove the toner. Further, in the case of a thin coated paper or the like, the stiffness of the recording paper itself is weak and the recording paper is not easily peeled.
Accordingly, it is an object of the present invention to provide a fixing device having a sufficient releasability even in a printing mode in which the printing is difficult to be performed.
[0005]
[Means for Solving the Problems]
[Fixing device]
In order to achieve the above object, a fixing device according to the present invention is a fixing device that fixes toner adhered to a recording medium, and includes a fixing roller having an elastic layer formed at least on a surface thereof; A belt that sandwiches the recording medium to form a nip portion, and a pressing member that is provided to face the fixing roller with the belt therebetween and presses the belt in the direction of the fixing roller. The pressing member presses the recording medium passing through the nip more strongly at the end than at the center in the fixing roller rotation axis direction.
[0006]
Preferably, the pressing member presses the belt near the outlet of the nip portion, and a first pressing portion that presses the belt near the entrance of the nip portion more than the first pressing portion. And a second pressing portion, wherein the first pressing portion presses the end portion of the recording medium passing through the nip portion more strongly than the center portion in the fixing roller rotation axis direction.
[0007]
Preferably, the first pressing portion has higher rigidity than the second pressing portion.
[0008]
Preferably, the second pressing portion presses the center portion of the recording medium passing through the nip portion more strongly than the both end portions in the fixing roller rotation axis direction.
[0009]
Further, the fixing device according to the present invention is a fixing device for fixing toner adhered to a recording medium, wherein the recording medium is fixed between at least a fixing roller having an elastic layer formed on a surface thereof and the fixing roller. A belt that sandwiches the belt to form a nip portion, a pressing member that is provided to face the fixing roller with the belt interposed therebetween, and presses the belt in the direction of the fixing roller; On the belt side, a separation assisting member having a length substantially equal to the length of the belt in the rotation axis direction is provided, and an end of the separation assisting member is located near the surface of the belt.
[0010]
Preferably, an end of the peeling assisting member located near the surface of the belt has a shape protruding in the direction of the surface of the belt at an end from a center in the rotation axis direction of the fixing roller.
[0011]
Preferably, the fixing roller side near the outlet of the nip portion further includes a main peeling member having a length substantially equal to a length of the fixing roller in a rotation axis direction, and an end of the main peeling member is fixed to the fixing portion. It is located near the surface of the roller.
[0012]
Further, the fixing device according to the present invention is a fixing device for fixing toner adhered to a recording medium, wherein the recording medium is fixed between at least a fixing roller having an elastic layer formed on a surface thereof and the fixing roller. A belt that sandwiches the belt to form a nip portion, and a first pressing portion that is provided to face the fixing roller across the belt and presses the belt in the direction of the fixing roller near an outlet of the nip portion. A second pressing portion provided to face the fixing roller with the belt therebetween, and pressing the belt closer to the entrance of the nip portion than the first pressing portion in the direction of the fixing roller. The surface of the first pressing portion that presses the belt is a curved surface protruding in the direction of the fixing roller, and the recording medium conveyance direction at a point where the pressure that presses the belt on the curved surface is maximum. The tangent line is parallel to a nip straight line connecting the contact point where the fixing roller and the belt contact near the nip portion entrance and the contact contact near the nip portion exit, or the nip straight line at the nip portion exit side. In comparison, it is inclined in a direction away from the fixing roller.
[0013]
[Image forming apparatus]
Further, an image forming apparatus according to the present invention includes the fixing device according to any one of claims 1 to 8.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
[Copy device]
FIG. 1 is a diagram illustrating a configuration of a copying apparatus 10 (image forming apparatus) having a fixing device 20 according to the present invention.
As shown in FIG. 1, a copying apparatus 10 includes a control device 11 for controlling the entire apparatus, a paper tray unit 12, a document feeding device 14 for feeding a document sheet 40, a scanner 16 for reading an image on the document sheet 40, a xerography, and the like. The print engine 18 forms a toner image on the printing paper 42, and the fixing device 20 fixes the toner image on the printing paper 42.
The toner used by the copying apparatus 10 is, for example, a polyester polymerized toner with WAX internally added, and has four colors of yellow, magenta, cyan, and black.
The arrows in the figure indicate the directions of the X axis, the Y axis, and the Z axis, for example, (-X) indicates the minus direction of the X axis. The X, Y, and Z axes in this figure correspond to those in the following figures.
[0015]
[Fixing device]
FIG. 2 is a diagram illustrating the configuration of the fixing device 20 in more detail.
As shown in FIG. 2, the fixing device 20 includes a fixing roller 210, an endless belt 220, a pressing member 230, a belt traveling guide 240, a peeling unit 250, and a peeling auxiliary unit 260.
The fixing roller 210 has a heat-resistant elastic layer 214 and a heat-resistant resin layer 216 formed around a metal core (cylindrical core) 212, and a heat source 218 such as a halogen lamp is provided inside the core 212. Having.
The core 212 is formed of a metal having high thermal conductivity such as iron, aluminum, or stainless steel, and the heat-resistant elastic layer 214 and the heat-resistant resin layer 216 are formed of, for example, PFA.
The endless belt 220 is, for example, a cylindrical belt, and the outer peripheral surface of the belt is brought into contact with the fixing roller 210 so as to be wound around the fixing roller 210 at a predetermined angle to form a nip portion through which the printing paper 42 passes.
The endless belt 220 is formed by coating a base layer made of, for example, polyimide with PFA.
[0016]
The pressing member 230 includes an elastic pressing member 232 (second pressing portion), a low friction layer 234, a support member 236, and a rigid pressing member 238 (first pressing portion).
The elastic body pressing member 232 has a concave curved surface substantially attached to the outer peripheral surface of the fixing roller 210, is disposed inside the endless belt 220, and presses the endless belt 220 in the direction of the fixing roller 210 with the concave curved surface, and A nip is formed.
In addition, the elastic body pressing member 232 forms a low friction layer 234 having a high surface smoothness on a portion in contact with the inner peripheral surface of the endless belt 220, and realizes smooth rotation of the endless belt 220.
The elastic pressing member 232 is formed of an elastic material such as silicone rubber, fluorine rubber or a leaf spring, and the low friction layer 234 is formed of glass fiber impregnated with Teflon (registered trademark), for example.
The rigid-body pressing member 238 is disposed behind the elastic-body pressing member 232 in the sheet conveyance direction, and presses the fixing roller 210 via the endless belt 220 to generate distortion on the outer periphery of the fixing roller 210.
The rigid body pressing member 238 is formed of a rigid body member such as aluminum.
The elastic body pressing member 232 and the rigid body pressing member 238 are held by a metal support member 236.
[0017]
The belt running guide 240 is provided on the surface of the support member 236 on the side opposite to the elastic body pressing member 232, and makes the sliding rotation of the endless belt 220 smooth.
Therefore, it is desirable that the surface of the belt running guide 240 that contacts the endless belt 220 be made of a material having a low friction coefficient and low thermal conductivity.
[0018]
The peeling means 250 is disposed on the side of the fixing roller 210 near the nip exit, and has a peeling member 252 (main peeling member) and a first holding member 254 that holds the peeling member 252.
The peeling member 252 is, for example, a thin plate member having heat resistance, and the length of the peeling member 252 in the X-axis direction is substantially the same as the length of the endless belt 220 in the X-axis direction.
The first holding member 254 holds the peeling member 252 such that the end of the peeling member 252 is located near the surface of the fixing roller 210 near the exit of the nip portion.
[0019]
The peeling assisting means 260 is disposed on the endless belt side near the nip outlet, and has a peeling assisting member 262 and a second holding member 264 for holding the peeling assisting member 262.
The peeling assisting member 262 is, for example, a thin plate member having heat resistance, and a maximum plane of the peeling assisting member 262 is substantially rectangular.
Further, the length of the peeling auxiliary member 252 in the X-axis direction is substantially the same as the length of the endless belt 220 in the X-axis direction.
The second holding member 264 holds the separation assisting member 262 such that the end of the separation assisting member 262 is located near the outer peripheral surface of the endless belt 220 near the exit of the nip portion.
Note that the peeling member 252 and the peeling auxiliary member 264 are formed of a metal such as aluminum or a heat-resistant resin.
[0020]
[Pressure distribution]
Next, the distribution of the pressure (nip pressure) at which the pressing member 230 presses the endless belt 220 will be described.
FIG. 3 is a diagram illustrating an example of a cross section (L cross section) of the fixing device 20 in FIG.
As shown in FIG. 3, the rigid body pressing member 238 has convex portions 238a and 238b at both ends in the rotation axis direction (X direction) of the fixing roller 210.
The convex portions (238a and 238b) and the concave portions (238c) of the rigid body pressing member 238 press the printing paper 42 in the direction of the fixing roller 210 via the endless belt 220, causing distortion on the surface of the fixing roller 210. Let it.
[0021]
FIG. 4 shows a graph of the nip pressure in the K section and the L section shown in FIG.
The solid line shown in FIG. 4 indicates the nip pressure in the L section, and the dashed line indicates the nip pressure in the K section.
In the L section, the nip pressure on the endless belt 220 and the fixing roller 210 is higher at both ends (Pe) than at the center (Pc) in the rotation axis direction (X-axis direction) of the endless belt 220.
Therefore, the distortion of the surface of the fixing roller 210 increases at both ends in the rotation axis direction (X-axis direction), the peeling performance at both ends of the printing paper 42 increases, and the endless belt 220 slides at both ends in the rotation direction (X-axis direction). Since the resistance is large, the transport speed at both ends of the printing paper 42 is reduced, so that the separation delay at the central portion of the printing paper 42 can be prevented, and good peeling performance can be realized in the entire rotation axis direction (X-axis direction).
Note that the rigid body pressing member 238 is not limited to the shape illustrated in FIG. 3 as long as the nip pressure at both ends in the rotation axis direction (X axis direction) of the endless belt 220 can be made higher than the center portion. You may comprise using the member from which both ends and a center part differ in rigidity.
On the other hand, in the K cross section, the nip pressure on the endless belt 220 and the fixing roller 210 is higher at the center than at both ends in the rotation axis direction (X-axis direction) of the endless belt 220.
Since the end of the printing paper 42 is likely to be wrinkled, the elastic pressing member 232 presses the endless belt 220 with a pressure distribution as shown in the K section (FIG. 4), and the rotation of the fixing roller 210 in the rotation axis direction (X (Axial direction) Distortion at both ends is reduced to reduce paper wrinkles.
[0022]
FIG. 5 is a diagram illustrating a curved surface of the rigid body pressing member 238.
As shown in FIG. 5, the surface of the rigid body pressing member 238 that contacts the endless belt 220 is a curved surface that is convex in the direction of the fixing roller 210.
The nip pressure on the convex curved surface of the rigid body pressing member 238 is maximized at the point P in the figure, and the tangent at the point P of the convex curved surface of the rigid body pressing member 238 (in the direction in which the printing paper 42 is conveyed) is M.
A nip line N in the figure is a straight line connecting a point Q at which the fixing roller 210 and the endless belt 220 come into contact at the nip entrance and a point R at which the fixing roller 210 comes into contact at the nip exit.
The tangent line M is preferably parallel to the nip line N or inclined in a direction away from the fixing roller 210 on the nip portion exit side with respect to the nip line N. In this example, the tangent line M is the fixing roller on the nip portion exit side. It is inclined by an angle α with respect to the nip line N in a direction away from the nip line N.
As described above, when the rigid body pressing member 238 has a convex curved surface such that the tangent at the maximum point of the nip pressure moves away from the fixing roller 210 on the nip portion exit side, the printing paper 42 is more easily peeled off from the fixing roller 210. Become.
[0023]
FIG. 6 shows a graph of the nip pressure in the paper transport direction.
As shown in FIG. 6, the nip pressure of the portion pressed by the elastic pressing member 232 is lower than the nip pressure of the portion pressed by the rigid pressing member 238.
The nip pressure of the portion pressed by the elastic pressing member 232 is substantially constant, and is suitable for fixing a toner image.
Further, the nip pressure of the portion pressed by the rigid body pressing member 238 is locally maximum (Pc) at the point P (FIG. 5) because the surface of the fixing roller 210 is distorted by an amount suitable for peeling.
As described above, the nip pressure is locally increased near the nip exit, and the surface of the fixing roller 210 near the nip exit is locally distorted, thereby improving the releasability of the printing paper 42.
[0024]
[Fixing operation]
Next, the operation of the fixing process will be described with reference to FIG.
When the fixing roller 210 rotates in the direction of arrow B, this rotation also causes the endless belt 220 to rotate.
The printing paper 42 on which the toner image 420 has been formed by the print engine 18 (FIG. 1) is conveyed in the direction of arrow A and inserted through the nip of the fixing device 20.
The printing paper 42 inserted into the nip portion is brought into close contact with the outer peripheral surface of the fixing roller 210 by pressing the elastic body pressing member 232 on the surface on which the toner image 420 is formed.
The toner image 420 on the printing paper 42 brought into close contact with the outer peripheral surface of the fixing roller 210 is melted by heat supplied from the fixing roller 210 and is fixed on the printing paper 42.
The printing paper 42 on which the toner image is fixed is separated from the fixing roller 210 by the distortion of the outer peripheral surface of the fixing roller 210 by the rigid body pressing member 238 and the releasing action of the heat resistant resin layer 216.
[0025]
The peeling unit 250 assists in peeling the printing paper 42 from the fixing roller 210, and the peeling assisting unit 260 assists in peeling the printing paper 42 from the endless belt 220.
Further, the peeling assisting unit 260 receives the corner of the printing paper 42 curled in the negative Z-axis direction (−Z direction), and corrects the curling of the printing paper 42.
[0026]
As described above, immediately before the exit of the nip portion, by pressing both ends in the rotation axis direction of the printing paper 42 more strongly than the center portion, the separation performance of the separation 42 for printing from the fixing roller 210 can be improved.
In addition, when the printing paper 42 adheres to the endless belt 220 with the improvement of the peeling performance, the peeling auxiliary member 262 peels the printing paper 42 from the endless belt 220, and when the printing paper 42 curls, The peeling assisting member 262 can correct the curl of the printing paper 42.
[0027]
[Confirmation of peeling performance]
Next, the peeling performance is confirmed by changing the ratio of the nip pressure Pe (FIG. 4) at both ends of the fixing roller 210 in the rotation axis direction and the nip pressure Pc (FIG. 4) at the center by the rigid body pressing member 238.
Hereinafter, Pc / Pe is defined as a coefficient k.
FIG. 7 is a table of the peeling performance and the paper wrinkle performance when the coefficient k is changed, and FIG. 8 is a table of the evaluation criteria for evaluating the peeling performance and the paper wrinkle performance shown in FIG.
FIG. 9 is a graph of the peeling performance and the paper wrinkle performance shown in FIG.
As shown in FIG. 7, the peeling performance and the paper wrinkling performance when the coefficient k was 0.50, 0.75, 0.83, 1.00 and 1.25 were evaluated.
The peeling performance and the paper wrinkling performance were evaluated for each surface temperature (160 ° C. to 185 ° C.) of the fixing roller 210, and were compared for each coefficient k.
[0028]
[conditions]
Hereinafter, test conditions of the peeling performance and the paper wrinkle performance are shown.
Toner: Polyester polymerized toner with WAX component added internally Toner image: TMA = solid image of about 13 g / m ² , tip margin 3 mm
Printing paper: basis weight 104 g / m ²
Environment: temperature 25 ° C, humidity 60%
[0029]
[Evaluation criteria]
Next, the criteria for evaluating the peeling performance and the paper wrinkling performance will be described.
As shown in FIG. 8A, the evaluation was made based on five criteria A to E.
A to D are criteria for evaluating the peeling performance, and the test was performed under the conditions where the peeling is difficult (a solid image is formed on the printing paper and used). On the other hand, E is a criterion for evaluating the paper wrinkle performance, and the test was performed under conditions where paper wrinkles easily occur (using blank paper).
The criterion A is an evaluation criterion for the presence or absence of uneven gloss. The uneven gloss is caused by uneven heating at the time of poor peeling. When gloss unevenness occurred, it was evaluated as x.
The criterion B is an evaluation criterion for bubble generation. Bubbles are generated by excessive heating. That is, bubbles are generated according to excessive heating due to defective peeling. When air bubbles exceeding the standard were generated, it was evaluated as x.
The criterion C is an evaluation criterion for toner adhesion to the fixing roll 210. Adhesion of toner occurs due to excessive heating. When the toner adhered to the fixing roll 210, it was evaluated as x.
The criterion D is an evaluation criterion for scuffing by the peeling means 250. At the time of the peeling failure, the printing paper 42 comes into strong contact with the peeling means 250 and is scratched. When a scratch was generated on the printed surface, it was evaluated as x.
The criterion E is an evaluation criterion for paper wrinkles. Evaluate paper wrinkles that occur on normal blank paper. When paper wrinkles occurred in at least one of the three sheets, it was evaluated as x.
Further, as shown in FIG. 8 (B), the peeling evaluation was performed in accordance with the range of the temperature range evaluated as “に つ い て” for each evaluation criterion, and points were given to the peeling evaluation of each evaluation criterion.
When the temperature range evaluated as “○” is 30 ° C. or more, three points are obtained, and the points become lower as the temperature range becomes narrower.
[0030]
[result]
As shown in FIG. 7, at each temperature from 160 ° C. to 185 ° C., each of the above criteria A to D was evaluated, and the evaluation summarized for each of the evaluation criteria (A to D) was the peeling evaluation. The sum of the peeling evaluations for each evaluation criterion is the total peeling evaluation point.
Regarding the reference E, the evaluation of each temperature from 160 ° C. to 185 ° C. was collectively defined as a paper wrinkle performance point.
FIG. 9 is a graph in which the above-described total evaluation points of the peeling and the paper wrinkle performance points are plotted against the coefficient k.
As shown in FIG. 9, the peeling performance is good when the coefficient k is in the range of 0.7 to 0.9, and the paper wrinkle performance is good when the coefficient is 0.75 or more.
Therefore, the range of the value of the coefficient k is preferably from 0.7 to 0.9, and more preferably from 0.75 to 0.9.
[0031]
As described above, the fixing device 20 according to the present invention improves the peeling performance of the printing paper 42 by pressing both ends more strongly in the vicinity of the nip exit than at the center in the rotation axis direction of the printing paper 42. Can be done.
Further, the fixing device 20 can eliminate the curl of the printing paper 42 and the adhesion to the endless belt 220 that occur with the improvement of the peeling performance by using the peeling auxiliary member 262.
[0032]
[Modification]
Note that the peeling performance is particularly remarkable at the end of the printing paper 42, and considering the prevention of contact wear between the peeling assisting member 262 and the endless belt 220, the peeling assisting member 262 is positioned at both ends with respect to the endless belt 220. It is desirable to have a shape that is closer and separated at the center.
FIGS. 10A and 10B are diagrams illustrating a modification of the peeling assisting member 262. FIG.
As shown in FIGS. 10A and 10B, the peeling auxiliary member 262 has two protruding portions 266 protruding in the direction of the endless belt 220 at both ends at an end located near the outer peripheral surface of the endless belt 220. And a smooth recess 268 may be formed between the two protrusions 266.
The protrusion 266 may be a vertex as illustrated in FIG. 10A, or may be a portion parallel to the endless belt 262 as illustrated in FIG. 10B.
In particular, the shape illustrated in FIG. 10B is suitable when the size of the printing paper 42 is two or more.
As described above, the peeling assisting member 262 is provided with the protruding portions 266 at both ends in the rotation axis direction (X-axis direction) to receive and correct the curl at both ends of the printing paper 42. Wear and heat exchange due to contact can be reduced by minimizing the portion in the vicinity of.
[0033]
【The invention's effect】
As described above, according to the fixing device of the present invention, higher releasability can be realized.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a copying apparatus having a fixing device according to the present invention.
FIG. 2 is a diagram illustrating the configuration of a fixing device 20 in more detail.
3 is a diagram illustrating an example of a cross section (L cross section) of the fixing device 20 in FIG.
FIG. 4 is a graph of nip pressure in a K section and an L section shown in FIG. 2;
FIG. 5 is a diagram illustrating a curved surface of a rigid body pressing member 238.
FIG. 6 is a graph of a nip pressure in a paper transport direction.
FIG. 7 is a view showing a table of evaluation of peeling performance when a coefficient k is changed.
8A is a diagram showing a table of evaluation criteria shown in FIG. 7, and FIG. 8B is a diagram showing a table of evaluation points corresponding to the evaluation.
FIG. 9 is a graph of the peeling performance and paper wrinkle performance shown in FIG.
FIGS. 10A and 10B are diagrams exemplifying modifications of the peeling assisting member 262, respectively.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Copy apparatus 20 ... Fixing apparatus 210 ... Fixing roller 212 ... Core 214 ... Heat resistant elastic layer 216 ... Heat resistant resin layer 218 ... Heat source 220 ... Endless Belt 230 ... pressing member 232 ... elastic body pressing member 234 ... low friction layer 236 ... support member 238 ... rigid body pressing member 240 ... belt travel guide 250 ... peeling means 252: peeling member 254: first holding member 260: peeling auxiliary means 262: peeling auxiliary member 264: second holding member 42: printing paper 420: toner image

Claims (9)

A fixing device for fixing toner adhered to a recording medium, comprising:
A fixing roller having at least a surface formed with an elastic layer,
A belt that sandwiches the recording medium between the fixing roller and forms a nip portion;
A pressure member provided to face the fixing roller with the belt therebetween, and pressing the belt in the direction of the fixing roller;
The fixing device, wherein the pressing member presses the edge of the recording medium passing through the nip portion more strongly than the center in the rotation axis direction of the fixing roller. A first pressing portion that presses the belt near the outlet of the nip portion; and a second pressing portion that presses the belt near the entrance of the nip portion more than the first pressing portion. And
2. The fixing device according to claim 1, wherein the first pressing unit presses the end portion of the recording medium passing through the nip portion more strongly than the center portion in the fixing roller rotation axis direction. 3. The fixing device according to claim 2, wherein the first pressing portion has higher rigidity than the second pressing portion. 4. The fixing device according to claim 2, wherein the second pressing portion presses the center portion of the recording medium passing through the nip portion more strongly than both ends in the fixing roller rotation axis direction. 5. A fixing device for fixing toner adhered to a recording medium, comprising:
A fixing roller having at least a surface formed with an elastic layer,
A belt that sandwiches the recording medium between the fixing roller and forms a nip portion;
A pressure member that is provided to face the fixing roller with the belt interposed therebetween, and presses the belt in the direction of the fixing roller;
On the belt side near the outlet of the nip portion, a peeling auxiliary member having a length substantially equal to the length of the belt in the rotation axis direction,
A fixing device in which an end of the separation assisting member is located near a surface of the belt. 4. The fixing device according to claim 3, wherein an end of the separation assisting member located near the surface of the belt has a shape protruding toward the surface of the belt at an end from a center in a direction of the fixing roller rotation axis. 5. . On the side of the fixing roller near the outlet of the nip portion, further includes a main peeling member having a length substantially the same as the length of the fixing roller in the rotation axis direction,
The fixing device according to claim 5, wherein an end of the main peeling member is located near a surface of the fixing roller. A fixing device for fixing toner adhered to a recording medium, comprising:
A fixing roller having at least a surface formed with an elastic layer,
A belt that sandwiches the recording medium between the fixing roller and forms a nip portion;
A first pressing portion provided to face the fixing roller with the belt interposed therebetween, and pressing the belt in the direction of the fixing roller near an outlet of the nip portion;
A second pressing portion provided to face the fixing roller with the belt interposed therebetween, the second pressing portion pressing the belt closer to the entrance of the nip portion than the first pressing portion in the direction of the fixing roller. ,
The surface of the first pressing portion that presses the belt is a curved surface protruding in the direction of the fixing roller,
A tangent in the recording medium conveyance direction at a point where the pressure pressing the belt on the curved surface is the maximum connects the contact point where the fixing roller and the belt come into contact near the entrance of the nip and the contact point where the contact comes near the exit of the nip part. A fixing device that is inclined in a direction parallel to the nip straight line or in a direction away from the fixing roller as compared with the nip straight line on the exit side of the nip portion; An image forming apparatus comprising the fixing device according to claim 1.

Images