JPH112987A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a trouble to wind a record medium after a toner image is fixed on a fixing roll by improving the property of peeling the recording medium from the fixing roll, at the time of heating/pressing the record medium after the toner image is transferred, so as to obtain a fixed image. SOLUTION: A revolvably supported endless belt 2 is brought into contact with the fixing roll 1 provided with a heat source inside and rotatably supported and then, pressed on the fixing roll 1 with a pressure pad 3 from the back of the endless belt 2. This belt 2 is guided by a belt guide 4, at the rear of the pressure pad 3, to be revolved and the belt guide 4 has such a shape that it bulges to the upstream side of a presscontact position with the fixing roll 1, so that the belt 2 has such a shape that it is separated/opened from the fixing roll 1 with a large curvature, on the downstream side of the press-contact part. Thus, the peeling from the fixing roll 1 of the record medium 5 is facilitated because force for moving the recording medium 5 along the side of the fixing roll 1 is not exerted. Or it is all right to abut a pressing member on the outer periphery of the endless belt 2, to form it to such a shape that it has the large curvature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for fixing an unfixed toner image formed and carried on a recording medium to a recording medium in an image recording apparatus such as a printer, a copying machine, and a facsimile.

[0002]

2. Description of the Related Art In an electrophotographic image recording apparatus, a toner image is formed by transferring a toner to an electrostatic latent image formed on an image carrier, and the toner image is transferred onto a recording medium. A recording image is obtained by pressing and heating by a fixing device. In the fixing device, a pressing member is pressed against a fixing roll having a heat source, and in a state where the fixing roll is heated to a high temperature, a recording medium carrying a toner image is sent to the pressing portion, and the toner image is transferred. Is established.

In such a fixing device for fixing a full-color toner image, a fixing roll having an elastic layer on the surface is often used. On the other hand, as the pressing member, a pressing roll covered with an elastic layer has been generally used. This pressure roll is pressed against the fixing roll to apply the pressure required for fixing the toner image, and at the same time, by increasing the length of the pressed portion, the time for sufficiently heating the toner on the recording medium is reduced. Secure. Then, after the toner image is fixed, the toner which has been heated and has an increased adhesive force with the fixing roll is peeled off by a minute slip generated when the elastic layer of the fixing roll is compressed.

In such a fixing device, since the fixing roller has an elastic layer on the outer peripheral portion, the heat capacity of the fixing roll becomes large, and the temperature of the surface of the fixing roll can be fixed by a heat source installed inside the fixing roll. It takes a lot of power and time to do so. Further, since heat is taken by the pressure roll through the pressure contact portion, in order to maintain the temperature required for fixing, it is necessary to heat the fixing roll even in a standby state until the next recording operation, The energy loss is enormous. In particular, in recent years, environmental issues have been actively taken up, and such a problem of energy loss in an image recording apparatus has become an issue in apparatus development.

In order to solve the above-mentioned problem, there has been proposed a fixing device in which the start-up time is greatly reduced and which does not require heating in a standby state until the next recording operation. An apparatus disclosed in Japanese Patent Publication No. 262903 is known. FIG. 7 shows a schematic configuration of the fixing device. In this fixing device, a pressure pad 103 is supported so as to be parallel to the rotation axis of the fixing roll 101, and the endless belt 102 is pressed against the surface of the fixing roll 101 by the pressure pad 103. The endless belt 102 is supported so as to be able to move around, and a belt guide 104 is provided inside the endless belt 102.

The fixing roll 101 is formed by covering the surface of a steel roll having an outer diameter of 30 mm and a thickness of 0.4 mm with an elastic layer having a thickness of 0.5 mm and further layering a release layer on the surface. A heating lamp 107 is provided inside. Further, as the endless belt 102, a belt in which the outside of a 75-μm-thick polyimide belt is covered with Teflon is used. Flanges (not shown) are provided on both ends of the belt guide 104, that is, on both sides in the width direction of the belt, thereby preventing the endless belt 102 from being biased or dropped.

When the toner image is actually fixed by the fixing device, the fixing roller 101 and the endless belt 102 are used.
Then, the recording medium 105 on which the toner image has been transferred is sent to the pressure contact portion formed between the recording medium 105 and the recording medium 105. As a result, the unfixed toner image 106 is heated and melted, and is pressed on the recording medium. In the vicinity of the exit of the pressure contact portion, a change in distortion when the elastic layer of the fixing roll 101 is released from the pressure of the pressure pad 103 reduces the adhesive force of the toner to the fixing roll, and the toner image is easily peeled from the fixing roll. State. In addition, since the rigidity of the recording medium acts to separate the toner fixed on the recording medium from the fixing roll, the recording medium can be separated from the fixing roll without requiring a forcible peeling force. Become.

In this fixing device, an endless belt 102 is used instead of the pressure roll.
Since the pressure contact portion is provided by pressing the elastic body from the inner peripheral surface of the fixing roll to the fixing roll side, the thickness of the elastic layer of the fixing roll 101 can be made extremely thin, and a fixing roll having a small diameter can be used. As a result, the heat capacity of the fixing roll 101 is reduced, and the rise time can be shortened. Further, by using the endless belt, the heat taken from the fixing roll 101 through the pressure contact portion can be reduced, so that it is not necessary to energize the heating lamp during the standby time until the next image recording. Therefore, when such a fixing device is employed in an image recording device or the like, significant energy saving can be realized.

[0009]

However, such a fixing device has the following problems. In the above-mentioned conventional fixing device, as shown in FIG. 8, since the elastic body 114 of the pressure pad 103 is pressed against the small-diameter fixing roll 101 via the endless belt 102,
The shape of the endless belt 102 in the region A of the press contact portion is concave along the curved surface of the fixing roll 101. The endless belt 102 is made of a material having strength and thickness that does not buckle even when pressed against flanges provided at both ends of the guide member. In area B after passing area A, it also moves along the fixing roll. This is because the endless belt 102 has a marginal length with respect to the peripheral surface of the belt guide 104 and no circumferential tension acts on the endless belt 102. It is intended to move in the extension direction of the shape.

For this reason, a force is exerted at the exit of the pressure contact portion so as to make the recording medium follow the curvature of the fixing roll, thereby preventing the recording medium from being separated from the fixing roll, or the toner once separated adheres to the fixing roll again. And the recording medium is wound around the fixing roll.

In order to solve such a problem, Japanese Patent Application Laid-Open No. Hei 8-262903 discloses a pressure applying member having a curved surface with a large curvature provided on the downstream side of a pressure contact portion of a pressure pad. A method of increasing the slip at the interface between the toner and the fixing roll on the recording medium by locally deforming the recording medium is described. However, even with this method, when fixing is performed on a thin recording medium having low rigidity, a sufficient effect cannot be obtained, and a problem that the recording medium is wound around a fixing roll is likely to occur. As a method for preventing winding of the recording medium, a method of mechanically separating the recording medium from the fixing roll by providing a member such as a peeling claw on the fixing roll is also known. When there is a toner image in a portion, it is difficult to peel the toner in a stable state. Further, such a fixing device has a complicated structure or is easily damaged on the fixing roll by a peeling claw,
Deterioration of image quality, toner offset, and the like occur at the scratched portion, resulting in a problem that the reliability of the fixing device is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to improve the releasability of a recording medium from a fixing roll with a simple configuration, and to perform recording after fixing a toner image. It is an object of the present invention to provide a fixing device capable of preventing a trouble in which a medium is wound around a fixing roll, shortening a start-up time, and greatly reducing heat energy required for fixing.

[0013]

Means for Solving the Problems In order to solve the above-mentioned problems, the invention according to claim 1 of the present application comprises a fixing roll having a heat source therein and rotatably supported, and a part thereof. An endless belt that is in contact with the peripheral surface of the fixing roll and is supported so as to be able to move around; a pressure pad that is installed in parallel with the rotation axis of the fixing roll and presses the endless belt against the fixing roll; A belt guide that is supported behind the pad and guides the endless belt to move around, and pressurizes and heats the toner image on the recording medium fed between the fixing roll and the endless belt. In the fixing device that forms a fixed image, the belt guide has a shape that protrudes upstream of the pressure contact portion so that the curvature of the endless belt increases downstream of the pressure contact portion in the moving direction of the endless belt. It shall be.

According to a second aspect of the present invention, in the fixing device according to the first aspect, the belt guide forms a guide surface having a large curvature downstream of a pressure contact portion between the fixing roll and the endless belt. And a pressing member that is pressed against the outer peripheral surface of the endless belt so that the endless belt moves along the concave portion. It is assumed that

According to a third aspect of the present invention, in the fixing device according to the second aspect, the pressing member has a guide surface along a conveying direction of the recording medium.

According to a fourth aspect of the present invention, in the fixing device according to the first, second or third aspect, the bending rigidity in the circumferential direction of the endless belt is larger than that in the width direction. It is assumed that it has become smaller.

(Operation) According to the invention of the present application, the shape of the belt guide that guides the running of the endless belt has a shape that protrudes largely toward the upstream side of the press-contact portion between the endless belt and the fixing roll. Therefore, the endless belt that has passed through the pressure contact portion is deflected from the vicinity of the pressure contact portion outlet in a direction to separate from the fixing roll, and a force acts to make the recording medium that has passed the pressure contact portion approach the fixing roll near the pressure contact portion outlet. do not do. Therefore, the force for separating from the fixing roll can be effectively exerted by the rigidity of the recording medium, and even a thin recording medium can be easily separated from the fixing roll.

When a pressing member is provided downstream of the pressure contact portion to be in contact with the outer peripheral surface of the endless belt, the endless belt travels in a direction regulated by the pressing member, and is separated from the fixing roll at the exit of the pressure contact portion. To be deflected with a larger curvature. Therefore, the recording medium is easily separated from the fixing roll.

Further, when the pressing member has a structure which also has a function of guiding the conveyance of the recording medium, the recording medium which has passed through the pressure contact portion and curled in the direction of being separated from the fixing roll is directly transferred along the conveyance guide surface of the pressing member. Can be guided in a predetermined direction. Then, the sheet is conveyed so as to be curved in the opposite direction in a state of being heated and still at a high temperature, and the curl generated in the press contact portion can be corrected.

Further, in a configuration in which the bending stiffness in the circumferential direction of the endless belt is smaller than the bending stiffness in the axial direction,
The endless belt runs along the shape of the pressure pad and belt guide with large curvature while maintaining strength against buckling in the width direction. Therefore, the recording medium can be moved in the direction of separating from the fixing roll immediately after passing through the pressure contact portion, and the recording medium after toner fixing can be easily peeled off from the fixing roll.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. (First Embodiment) FIG. 1 is a schematic configuration diagram showing a fixing device according to an embodiment of the present invention. FIG. 2 is an enlarged sectional view of a main part of the fixing device. In this fixing device, a fixing roll 1 is rotatably supported around a central axis, and a pressure pad 3 and a belt guide 4 are integrally supported so as to be parallel to this axis.
An endless belt 2 that moves around the pressure pad 3 and the belt guide 4 is placed in a circumferentially tensionless state.
Are pressed against the fixing roll 1.

The fixing roll 1 has a coating layer 12 formed on the surface of a steel cylindrical base material 11 having an outer diameter of 25 mm, an inner diameter of 24.5 mm, and a length of 340 mm. The coating layer 12 includes an inner base layer 12a and an outer release layer 12b, and the base layer (elastic layer) 12a
And a release layer 12b formed by dip coating viton rubber into a layer having a thickness of 30 μm.

In the base of the fixing roll 1, a halogen lamp 7 having an output of 600 W is disposed as a heat source.
A temperature sensor 8 is provided at a position in contact with the surface of the fixing roll 1. When the temperature of the fixing roll surface rises or falls, the temperature sensor 8 is not shown according to a signal from the temperature sensor 13. The feedback mechanism by the temperature controller is operated, and the blinking of the halogen lamp 7 is controlled to adjust the temperature of the surface of the fixing roll 1 within a predetermined range.

The endless belt 2 is made of thermosetting polyimide in the form of a belt having a circumference of 94 mm, a thickness of 75 μm, and a width of 320 mm, and a PFA (tetrafluoroethylene-benfluoroethylene) as a release layer on the outer peripheral surface thereof. (Copolymer) to a thickness of 30 μm. The endless belt 2 is in contact with the fixing roll 1 at a winding angle of 45 °, and the pressing portion has a length of about 10 mm in the circumferential direction. The inner peripheral length of the endless belt 2 is set slightly longer than the peripheral length integrally surrounding the pressure pad 3 and the belt guide 4. In addition, a silicone oil is interposed between the pressure pad 3 and the inner peripheral surface of the endless belt 2 as a lubricant, so that friction during conveyance of the endless belt is reduced, and the endless belt 2 is smoothly conveyed. It has become.

The pressure pad 3 includes a support 13, an elastic body 14 disposed on the support, and an elastic body 14.
And a low friction film 15 stretched on a contact surface between the endless belt 2 and the endless belt 2. The elastic body 14 is made of silicone rubber and has a length of 320 mm, a width of 10 mm, and a thickness of 5 m.
m. The above low friction film 15
Is a sheet of glass fiber impregnated with a Teflon resin, and the low friction film 15 is provided so as to project in the circumferential direction from the contact surface between the elastic body 14 and the endless belt 2 and is projected. The upstream end of the low friction film 15 is fixed to the support 13. The support 13 has a width wider than the elastic body 14. At both ends in the longitudinal direction (width direction), pressing devices (not shown) are provided, and the elastic body 14 is fixed via the endless belt 2. The surface of the roll 1 is pressed with a force of 200N.

The belt guide 4 is directly attached to the support 13 and forms a curved surface behind the portion where the endless belt 2 is pressed against the fixing roll 1 to guide the endless belt 2 to move around. ing. In addition, ribs are provided on the curved surface in the circumferential direction of the endless belt 2 in order to reduce the contact area with the inner peripheral surface of the endless belt 2.
As shown in FIG. 1, the belt guide 4 has a shape that greatly protrudes upstream from the downstream side in the transport direction with respect to the center of the pressure contact portion between the fixing roll 1 and the pressure pad 3. For this reason, the cross-sectional shape of the endless belt 2 also corresponds to the cross-sectional shape of the belt guide 4, and the curvature of the endless belt 2 downstream of the pressure contact portion is larger than the curvature of the endless belt 2 in the unconstrained state. Immediately after passing the fixing roller 1, the fixing roller 1 is separated from the fixing roller 1.

On the other hand, flange members (not shown) are provided at both ends in the longitudinal direction of the belt guide 4, that is, in the width direction of the endless belt. When the endless belt 2 is biased to one side in the longitudinal direction, the endless belt 2 The end portion slides in contact with the flange-shaped member, and the rigidity in the longitudinal direction of the endless belt acts to further restrict the deviation.

Next, a fixing process by the fixing device will be described. The recording medium 5 onto which the toner images 6 of the four color toners of yellow, magenta, cyan, and black are transferred by a transfer device (not shown) is conveyed toward the pressure contact portion. These toners are low melting point, sharp melt color toners in which a color pigment is dispersed in a polyester base material. The fixing roller 1 is rotated at a speed of 160 mm / s by a driving motor (not shown) in a direction of an arrow a shown in the figure, and the endless belt 2 moves around the fixing roller 1. The fixing roll 1 is a small-diameter roll having an outer diameter of 25 mm, and the winding angle of the endless belt 2 at the press contact portion is about 45 °. In such a press contact portion, the endless belt 2
Is curved with a curvature opposite to the curvature in the unconstrained state, that is, in a substantially cylindrical state. Then, the recording medium 5 conveyed to the pressure contact portion is heated by the fixing roll 1 heated by the halogen lamp 7 and is also pressed by the pressure pad 3 via the endless belt 2 so that the toner image 6 is formed. 5 is fixed.

An amino-modified silicone oil having a viscosity of 300 cs is uniformly supplied as a release agent to the fixing roll 1 from a release agent supply device (not shown), and serves to prevent toner offset. In addition, since the protrusion of the belt guide 4 on the downstream side of the press contact portion is smaller than the protrusion on the upstream side,
The endless belt changes direction with a large curvature after passing through the pressure contact part,
The sheet is transported in a direction away from the fixing roll. for that reason,
The recording medium on which the fixing process has been performed is stably peeled off without being wound around the fixing roll at the exit of the pressure contact portion, and is conveyed to a discharge tray (not shown) to complete the fixing operation.

Although the fixing device shown in FIG. 1 has been described above, it is also possible to use a pressure pad as shown in FIG. In this pressure pad, a pressure applying member 20 and an elastic body 24 are integrally supported on a support 23, and a low friction film 2
5 are provided. The pressure applying member 20 has a radius of curvature of 3 m.
The elastic body 24 is a silicone rubber formed to have a width of 10 mm and a thickness of 5 mm, and is disposed so as to be in close contact with the pressure applying member 20. The pressure pad formed in this manner is such that the pressure applying member 20 is
It is disposed so as to be located on the downstream side of the pressure contact portion between the endless belt 2 and the endless belt 2.

When fixing is performed by a fixing device using the pressure pad, local distortion occurs in the elastic layer 12a of the fixing roll 1 at a portion corresponding to the pressure applying member 20, and the toner on the recording medium and the fixing roll are distorted. A slight slip occurs between the surface and the surface. As a result, the effect of reducing the adhesive force of the toner is obtained, and the releasability of the recording medium can be improved. Therefore, in the conventional fixing device, even if the endless belt is pressed by the pressure applying member, the curvature of the endless belt surface cannot be increased due to the rigidity of the endless belt,
Although the releasability could not be sufficiently improved, according to the fixing device of the present invention, the endless belt was bent at a large curvature along the surface of the pressure applying member 20 in the downstream area of the press-contact portion, and the fixing roll was further fixed. And can be sent in the direction to separate. As a result, the recording medium is also conveyed in a direction in which the recording medium is separated from the fixing roll in the vicinity of the exit of the pressing portion, and even a thin recording medium can be easily separated from the fixing roll.

In the fixing device shown in FIG. 1, in addition to the above, a fixing roll having a release layer directly formed on the surface of a substrate is used as the fixing roll. As the heat source, a method of providing a heating lamp inside the fixing roll, a method of providing a resistance heating layer between the back surface of the base material or the base material and the release layer, or a magnetic field generator in which a coil is wound inside the fixing roll is used. By providing the fixing roll, a method of causing the fixing roll to generate heat can be used. As long as the material of the endless belt has heat resistance, it can be selected from heat-resistant resin such as polyamide imide and metal material such as nickel and stainless steel in addition to polyimide resin.

(Second Embodiment) FIG. 4 is a schematic structural view showing a fixing device according to an embodiment of the present invention. In this fixing device, a pressing member 46 is in contact with the downstream side of the pressing portion of the endless belt 32 from outside, and a portion of the belt guide 34 facing the pressing member 46 is formed in a concave shape, and along the concave curved surface. The endless belt 32 moves. The pressing member 46 includes a pressing roll 46b and a stainless steel supporting member 46a that rotatably supports the pressing roll.
b are provided at both ends and a center portion of the endless belt 32 in the width direction. Since the press roll 46b is formed of a heat-resistant heat insulating member, even if it comes into contact with the endless belt, heat is not taken away by the press roll 46b.

When fixing is performed using this fixing device, the recording medium 35 carrying the toner image 36 is fixed to the fixing roll 31.
Is conveyed to the pressure contact portion between the endless belt 32 and the toner image. On the downstream side of the pressing portion, the endless belt 32 is pressed toward the concave portion of the belt guide 34 by the presser roll 46a, so that the endless belt 32 runs along the shape of the concave portion at this pressing portion. The pressing force acts to bend the direction of the endless belt 32 in the direction of separating from the fixing roll near the outlet of the press contact portion. For this reason, the recording medium 35 that has passed through the pressure contact portion is effectively separated by the rigidity of the recording medium from the fixing roll. Therefore, according to the fixing device 31, the recording medium after the completion of the fixing is stably peeled off from the fixing roll in the vicinity of the exit of the pressing portion, so that the toner offset and the winding of the recording medium are prevented, and the highly reliable fixing is performed. It can be performed.

(Third Embodiment) FIG. 5 is a schematic structural view showing a fixing device according to a third embodiment of the present invention. In this fixing device, the pressure pad 53 that presses the endless belt 52 against the fixing roll 51 has the configuration shown in FIG. On the downstream side of the press-contact portion between the fixing roll 51 and the endless belt 52, the endless belt 52 is in contact with the outer peripheral surface by a belt pressing pad 66. On the other hand, the belt guide has a concave portion similarly to the fixing device shown in FIG.
The endless belt 52 is convexly curved toward the endless belt with the leading end upward, and is pressed so that the endless belt 52 moves along the concave portion. The rear portion of the belt pressing pad 66 guides the conveyance of the recording medium, and is provided so that the conveying roller 67 sandwiches and conveys the recording medium conveyed along the belt pressing pad 66. ing.

When fixing is performed using this fixing device, the recording medium 55 carrying the toner image 56 is
Is conveyed to the pressure contact portion between the endless belt 52 and the toner, and the toner is fixed. On the downstream side of the pressing portion, the recording medium 55 is strongly pressed together with the endless belt 52 against the fixing roll 51 by the pressure applying member 65, and near the exit of the pressing portion curved along the curvature of the pressure applying member 65, the endless belt 52 is fixed to the fixing roll 51. The recording medium 55 that has passed through the pressure contact portion is easily peeled off from the fixing roll due to the traveling so as to separate from the recording medium and the curl generated in the recording medium by the action of the pressure applying member 65, and the belt pressing pad 66 Reach the position along. The belt pressing pad 66 also serves as a recording medium conveying guide. The recording medium is conveyed along the belt pressing pad 66 in a high temperature state, and a pair of conveying rolls 67 are bent in a direction opposite to the curl. Is discharged to a paper discharge tray (not shown).

Therefore, when this fixing device is used, even when a toner image is fixed on a thin recording medium having a small rigidity, the toner image can be peeled off from the fixing roll without applying a forcing force, and the recording medium after the fixing is fixed. The problem that the recording medium cannot be accommodated in the paper discharge tray due to the curl generated at the time of dropping and falls down can be solved. In addition, since the belt pressing pad 66 is configured to also serve as a conveyance guide of the recording medium, the apparatus does not become large.

(Fourth Embodiment) FIG. 6 is a schematic perspective view showing an endless belt used in a fixing device according to a fourth embodiment of the present invention. This endless belt 72
Is made of a polyimide resin mixed with carbon fibers and is formed in an endless belt shape having a thickness of 50 μm and a circumference of 94 mm. The carbon fibers 72 a are formed in a direction perpendicular to the circumferential direction of the endless belt 72 (in the width direction of the belt). ) Are mixed so as to increase the ratio of orientation.

The endless belt 72 can increase the bending rigidity in the width direction without increasing the rigidity in the circumferential direction. For this reason, it is possible to reduce the thickness of the endless belt while maintaining the strength in the width direction. Since the rigidity of the endless belt in the circumferential direction decreases as the layer of the endless belt becomes thinner, the endless belt can be easily moved in the direction in which the endless belt is separated from the fixing roll in the vicinity of the outlet of the pressing portion. For this reason,
According to the fixing device using the endless belt 72, the recording medium after fixing the toner is reliably peeled off from the fixing roll, and an image with high recording quality can be formed.

By employing the fiber-reinforced resin as described above, the bending stiffness in the circumferential direction of the endless belt can be made smaller than the bending stiffness in the axial direction, and the releasability of the recording medium from the fixing roll can be improved. As possible, glass fibers or various heat-resistant inorganic fibers can be used as the reinforcing fibers constituting such a fiber-reinforced resin in addition to carbon fibers. Further, as the resin for the base material, a polyamide imide resin or the like other than the polyimide resin can be selected as long as the resin has heat resistance.

[0041]

As described above, according to the fixing device of the present invention, it is possible to change the shape of the belt guide for guiding the running direction of the endless belt or to press the endless belt from the outer peripheral surface by the pressing member. With a simple configuration, the endless belt can be bent in the direction in which the endless belt is separated from the fixing roll near the exit of the press-contact portion between the fixing roll and the endless belt.
The recording medium after toner fixing can be easily peeled off from the fixing roll without applying a mechanical force. Therefore, even when a toner image is fixed on a recording medium having low rigidity, it is possible to prevent the recording medium from being wound around the fixing roll and clogging the recording medium, and to perform stable and reliable fixing.

Further, by making the bending rigidity in the circumferential direction of the endless belt smaller than that in the width direction, the recording medium can be easily peeled off from the fixing roll while maintaining the strength of the endless belt. Further, by configuring the pressing member that changes the running direction of the endless belt by pressing the endless belt from the outer peripheral surface to also serve as a conveyance and guide of the recording medium, the recording medium is easily peeled off from the fixing roll, and the toner is fixed. The curl generated on the subsequent recording medium can be corrected, and a fixing device having high quality image recording performance can be realized.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a fixing device according to an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a pressure contact portion between a fixing roll and an endless belt in the fixing device shown in FIG.

FIG. 3 is a schematic configuration diagram showing another example of a pressure pad that can be used in the fixing device according to the first aspect of the present invention.

FIG. 4 is a schematic configuration diagram showing a fixing device according to an embodiment of the present invention.

FIG. 5 is a schematic configuration diagram showing a fixing device according to an embodiment of the present invention.

FIG. 6 is a schematic perspective view showing an endless belt used in a fixing device according to an embodiment of the present invention.

FIG. 7 is a schematic configuration diagram showing a conventional fixing device.

FIG. 8 is an enlarged cross-sectional view of a pressing portion between a fixing roll and an endless belt in the conventional fixing device shown in FIG.

[Explanation of symbols]

 1, 31, 51, 101 ... Fixing roll 2, 32, 52, 102 ... Endless belt 3, 33, 53, 103 ... Pressure pad 4, 34, 54, 104 ··· Belt guides 5, 35, 55, 105 ··· Recording media 6, 36, 56, 106 ··· Toner images 7, 37, 57, 107 ··· Halogen lamp 8, 38, 58, 108 ... temperature sensors 11, 41, 61 ... base material 12, 42, 62 ... coating layer 12a, 42a, 62a ... ... Underlayer 12b, 42b, 62b ... Release layer 13, 23, 43, 63 ... Support 14, 24, 44, 64, 114 ... Elastic body 15, 25, 45・ ・ ・ ・ ・ ・ ・ ・ ・ Low friction film 46 ・ ・ ・ ・ ・ ・ Pressing part 46a ··· Presser roll 46b ··· Supporting member 65 ···· Pressing member 66 ······················ Transport roll

Claims (4)

[Claims] 1. A fixing roll having a heat source therein and rotatably supported; an endless belt partially contacting the peripheral surface of the fixing roll and supported so as to be able to move around; A pressure pad installed in parallel with the rotation axis of the endless belt to press the endless belt against the fixing roll; and a belt guide supported behind the pressure pad and guiding the endless belt to move around. In a fixing device in which a toner image on a recording medium fed between a roll and the endless belt is pressed and heated to form a fixed image, the belt guide is located downstream of a pressing portion in a moving direction of the endless belt. A fixing device characterized in that the fixing device has a shape protruding upstream of the pressure contact portion so that the curvature of the endless belt is increased. 2. The fixing device according to claim 1, wherein the belt guide forms a guide surface having a large curvature at a downstream side of a pressure contact portion between the fixing roll and the endless belt, and a downstream portion thereof. A concave portion having a curvature in the opposite direction on the side, so that the endless belt moves along the concave portion,
A fixing device, further comprising a pressing member pressed against an outer peripheral surface of the endless belt. 3. The fixing device according to claim 2, wherein the pressing member has a guide surface along a conveying direction of the recording medium. 4. The fixing device according to claim 1, wherein a bending rigidity in a circumferential direction of the endless belt is smaller than a bending rigidity in a width direction. Fixing device.