JP2003195660A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve the feeding property of recording paper from a transfer part to a paper ejection part in a fixing device using a sheet type pressure member. <P>SOLUTION: The fixing device is provided with the sheet type pressure member 35 in a cantilever supporting state on an upstream side in the feeding direction of the recording paper to a fixing roller 30 and fixes a toner image on the recording paper by making the recording paper pass through a fixing nip part formed. The sheet-type pressure member 35 abuts on the fixing roller 30, and a rib is erected at the center part of the guide surface of the recording paper from a transfer nip part to the fixing nip part. Ribs are erected at both ends in the feeding direction of the recording paper, and the rib at the center part is set higher than the ribs at both ends so that the recording paper is fed to the fixing nip part in a curved state in a width direction. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device and an image forming apparatus applied to an electrophotographic apparatus such as a facsimile machine, a printer, a copying machine, or a multifunction machine having these functions.

[0002]

2. Description of the Related Art FIG. 9 is a side view showing an internal structure of a facsimile apparatus having a conventional fixing device and image forming apparatus. Reference numeral 1 is a main body of the facsimile apparatus, and 2 is removable from the main body 1. , A process cartridge accommodating various process devices for forming an image by an electrophotographic process, 3 a photoconductor provided in the process cartridge 2, and 4 scanning the photoconductor 3 with laser light modulated based on image data. An optical writing device, 5 is a paper feed cassette that stores recording paper, 6 is a paper feed roller that feeds recording paper from the paper feed cassette 5, and 7 is abutting against the photoconductor 3 so that the recording paper is placed on the photoconductor 3. A transfer roller 8 for transferring the toner image formed on the sheet has a fixing roller 9 and a pressure roller 10, and a fixing device 11 for fixing the toner image on the recording paper.
Is a discharge roller, 12 is a contact sensor, and 13 is a document placing table formed on the upper surface of the main body 1.

The original set on the original placing table 13 is discharged to the outside through the contact sensor 12 by the conveying system. When the document passes through the contact sensor 12, the image of the document is optically read by the contact sensor 12. The image data read by the contact sensor 12 or the image data input from the outside is sent to the optical writing device 4, and the photoconductor 3 is uniformly charged with the laser light modulated by the optical writing device 4 based on the image data. By irradiating the surface of the photosensitive member 3, an electrostatic latent image is formed on the surface of the photoconductor 3. Toner is attached to this electrostatic latent image to form a toner image, and this toner image is transferred to the recording paper by the transfer roller 7. And
The toner image is fixed on the recording paper by passing through the nip portion of the fixing roller 9 and the pressure roller 10 in the fixing device 8 to apply pressure / heat, and is discharged to the outside by the paper discharge roller 11.

FIG. 10 is a side view showing the internal structure of a conventional fixing device. Reference numeral 14 is a fixing heater arranged inside the fixing roller 9 to heat the fixing roller 9, and 15 is to detect the temperature of the fixing roller 9. Temperature detecting means, 16 is a fixing roller 9
Separation claws for separating the recording paper stuck to the fixing roller 9 from the fixing roller 9, 17 a cleaning pad for contacting the fixing roller 9 to clean the fixing roller 9, and 18 a downstream side of the cleaning pad 17 in the rotation direction of the fixing roller 9. A cleaning pad invasion restricting member provided in the reference numeral 19 denotes an entrance guide plate attached to the entrance of the recording paper of the fixing device main body.

The recording paper on which the toner image is transferred enters the nip portion between the fixing roller 9 and the pressure roller 10 via the entrance guide plate 19. Then, after the toner image is fixed on the recording paper by being pressed / heated in the nip portion, the toner image is discharged to the outside through the paper discharge roller 11. Toner attached to the fixing roller 9 when the recording paper passes through the nip portion is removed by the cleaning pad 17.

The surface temperature of the fixing roller 9 is the temperature detecting means 1
5, the heating control by the fixing heater 14 is performed by a control unit (not shown) based on the detection result of the temperature detection unit 15.

By the way, conventionally, in the fixing device, an infrared heater or a halogen heater is adopted as a fixing heater, and it is most common to use a pair of a fixing roller and a pressure roller. However, since the pressure roller has a structure in which a silicone rubber layer is formed on a core metal and a release layer such as Teflon (registered trademark) tube is formed on the core rubber, the heat capacity is large, and even if heating is started, the pressure roller is not heated. The pressure roller does not warm up easily, which is a cause of poor fixing. Furthermore, there was the disadvantage that the cost of parts was high. Further, in order to secure an appropriate nip width in the nip portion between the fixing roller and the pressure roller, a large pressure is required, and the pressure causes a stress on the recording paper, which causes fixing wrinkles.

Therefore, instead of the pressure roller, a sheet-shaped pressure member is pressed against the fixing roller to form a nip, and the recording paper is passed through the nip portion to fix the unfixed image on the recording paper. Fixing devices are being studied. With such a configuration, since it is a sheet-shaped pressing member, it is easy to warm, it is possible to secure the nip width, and it is possible to improve the thermal efficiency as compared with the conventional machine.

[0009]

However, since the surface of the fixing roller is formed smoothly so that the toner does not adhere to the surface of the fixing roller, in the fixing device using the sheet-like pressure member, the fixing roller conveys the toner from the fixing roller. It is difficult to obtain power. Therefore, the carrying force for passing through the nip portion between the fixing roller and the sheet-like pressure member is largely due to the carrying force from the transfer roller. Here, if the recording paper has a strong stiffness, the transport force from the transfer roller is easily transmitted to the nip portion, but in the case of thin paper, the transport force of the transfer roller reaches the fixing nip portion because the stiffness of the recording paper is weak. It is difficult to reach and easy to become JAM. Further, in recent years, an increasing number of users are once using an image recording apparatus to form an image on the front surface and reusing a blank recording paper (hereinafter referred to as backing paper) on the back surface. In many cases, the curl paper is difficult to enter the nip portion, so it easily becomes JAM.
There was a problem.

Further, recently, the downsizing and space saving of the apparatus main body have been advanced, and many apparatuses eject the inside of the body without using a sheet ejection tray outside the apparatus main body as a conveyance path for bending the recording sheet immediately after fixing. Has become.

FIG. 11 is a side view showing the internal structure of a facsimile apparatus of the type that discharges recording paper from the inside of the body. Reference numeral 20 is a recording paper discharging unit, and 21 is a recording paper for external feeding. The manual document feed tray, 22 is provided above the recording paper discharge unit 20, and the document placement tray on which the document is placed 23 is provided between the recording paper discharge unit 20 and the document placement tray 22. A document discharge tray 24 is provided for placing a document after image reading, and 24 is a document placement tray 2 in the main body 1.
2 shows a manual document feeding tray provided on the opposite side of the installation site of 2 and the document discharging tray 23. The same members as those of the facsimile apparatus shown in FIG. 9 or members having the same functions are designated by the same reference numerals, and detailed description thereof will be omitted.

The recording paper discharging unit 20 is formed on the upper surface of the main body 1, and the discharging roller 1 is provided above the side of the recording paper discharging unit 20.
1 is arranged.

The recording paper fed from the paper feeding cassette 5 set in the horizontal direction is conveyed in the vertical direction, passes through the transfer roller 7 and the fixing device 8, and is conveyed in the paper feeding cassette 5.
To the opposite direction to the paper feeding direction from the paper ejection roller 11
The recording paper is ejected onto the recording paper ejection unit 20.

A document is set on the document placing tray 22 with the image surface facing upward, and the set document is inverted, passed through the contact sensor 12, and passed through the discharge roller 11 to the document discharge tray 23. It is ejected on top. Originals are set on the manual feed tray 24 with the image side facing down.
The set document passes through the contact sensor 12 and is discharged onto the document discharge tray 23 via the discharge roller 11.

As shown in FIG. 11, in the case of an image forming apparatus of the type in which the recording paper is inverted and ejected, the conveyance direction of the recording paper is switched from the vertical direction to the horizontal direction from the fixing device 8 to the paper ejection roller 11. When the carrying direction changes, the recording paper and the guide plate come into contact with each other, and the carrying load is applied to the recording paper. Here, in the case of the fixing device using the pressure roller, since the conveying force is applied to the recording paper in the fixing device, the recording paper is pushed out and conveyed to the paper discharge roller 11.

However, since the fixing device using the sheet-like pressure member does not use the pressure roller, as described above, when the recording paper conveyance force is small and the conveyance path after fixing has a curvature, The conveyance load is applied to the recording sheet at the curved portion before reaching the sheet ejection roller, and the leading edge of the recording sheet does not reach the sheet ejection roller 11, which may cause conveyance failure due to the waist of the sheet.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and to provide a fixing device and an image forming apparatus using a sheet-like pressure member, which realizes an improvement in the transportability of recording paper. And

[0018]

In order to achieve the above object, the fixing device of the invention according to claim 1 is a heat transfer member having a heat source inside, and a sheet pressurizing member that abuts and presses against the heat transfer member. A sheet pressing member, one end of the sheet pressing member is fixed to a mounting portion provided on the upstream side of the heat transfer member in the recording paper conveyance direction, and the other end of the sheet pressing member is attached to the heat transfer member. The recording paper on which the toner image has been transferred is pressed / heated when passing through the nip portion between the heat transfer member and the sheet pressing member, so that the toner image is transferred onto the recording paper. A fixing device for fixing is characterized in that means for raising the central portion of the recording paper to make it higher than both end portions is provided at the central portion of the conveyance guide from the transfer portion to the fixing portion. With this configuration, by lifting the central portion of the recording paper, the rigidity of the recording paper is strengthened, and it becomes possible to transfer the conveyance force of the transfer portion to the fixing portion without loss, thereby preventing the occurrence of jam. You can

A fixing device according to a second aspect of the present invention is the fixing device according to the first aspect, characterized in that a guide member for guiding the recording sheet to the nip portion is provided on the image surface side of the entrance of the fixing nip. . With this configuration, when the recording paper is curled, the position of the uppermost portion of the recording paper is regulated, and the uppermost portion of the recording paper comes into contact with the heat transfer member and becomes a conveyance load. It is possible to prevent the recording paper from being lifted up from the conveyance path and escape, and to convey the conveyance force of the transfer section to the fixing section without loss.

A fixing device according to a third aspect of the present invention includes a heat transfer member having a heat source inside and a sheet pressing member that abuts and presses against the heat transfer member, and one end of the sheet pressing member. Part is fixed to a mounting part provided on the upstream side in the recording paper conveyance direction with respect to the heat transfer member, and the other end of the sheet pressing member is brought into contact with the heat transfer member in a pressed state, and a toner image is formed. A fixing device for fixing a toner image on a recording sheet by pressurizing / heating the transferred recording sheet when passing through the nip portion between the heat transfer member and the sheet pressing member, A conveyance roller is arranged at a portion of the conveyance path in which a conveyance load applied to the recording sheet in the conveyance path to the sheet ejection unit for ejecting the recording sheet is smaller than a conveyance force for conveying the recording sheet after passing through the nip portion. It is characterized by doing. With such a configuration, even in a device in which the recording paper after fixing is subjected to a conveying load, for example, in a device having a curvature in the conveying path immediately after fixing, the conveying roller compensates for the conveying force to ensure good conveying quality. Can be secured.

A fixing device according to a fourth aspect of the present invention is characterized in that, in the third aspect of the invention, the linear velocities of the conveying roller and the fixing roller are substantially constant. With this configuration, by making the linear velocity almost constant,
Image distortion due to being pulled by the transport roller and image distortion due to loop stiffness do not occur.

An image forming apparatus according to a fifth aspect of the present invention includes the fixing device according to any one of the first to fourth aspects. With this configuration,
Stable transportability can be obtained, and the fixability is improved.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a side view showing the structure of a fixing device according to an embodiment of the present invention, and FIG. 2 is a front view of FIG.
Reference numeral 0 is a fixing roller, 31 is a heat source provided inside the fixing roller 30, 32 is a bearing provided at both ends of the fixing roller 30, 33 is a fixing member for supporting the bearing 32, 34 is a base, and 35 is a sheet. A pressure member, 36 is a mounting portion of the sheet pressure member 35, and 37 is a screw for fixing the fixing member 33 to the base 34. The same members as those in the conventional technique shown in FIGS. 9 and 10 are designated by the same reference numerals and detailed description thereof is omitted.

The sheet-shaped pressure member 35 is a heat-resistant member having resistance at the fixing temperature, for example, fluororesin (PF).
A, PTFE, cross-linked PTFE, FEP, etc.), and a heat resistant resin such as polyimide.

A concave portion 34a is formed in a portion of the base 34 facing the fixing roller 30, and the concave portion 34a is formed.
A stepped mounting portion 36 is formed at an edge portion on the upstream side in the recording paper conveyance direction in a. Transfer roller 7 to fixing roller 3
Lower guide portion and concave portion 34 for guiding the lower surface of the recording paper to 0
The a and the attachment portion 36 are formed when the base 34 is molded.

Then, one end of the sheet-shaped pressure member 35 is brought into contact with the stepped portion of the mounting portion 36, and one end of the sheet-shaped pressure member 35 is tightly fixed to the mounting plane 36a by a double-sided adhesive tape. The sheet-like pressure member 35 is fixed to the mounting portion 36 in a cantilevered manner so that the other end of the pressure member 35 can be vertically moved as a free end.

Further, fixing members 33, 33 are fixed by screws 37, 37 on the base 34 on the downstream side of the mounting portion 36 in the recording paper conveying direction. As shown in FIG. 2, the fixing members 33, 33 are fixed. The fixing roller 30 is installed in the main body of the image forming apparatus by supporting the fixing roller 30 between the bearings 32, 32. Here, the mounting portion 36 is formed on the base 34 so that a plane including the mounting plane 36a crosses the lower portion of the fixing roller 30, and the sheet-shaped pressure member 35 is closely fixed to the mounting portion 36, As shown in FIG. 1, the sheet-like pressure member 35 is cantilevered along a plane A including the mounting plane 36a. In the first embodiment, the mounting plane 36a is formed so that the sheet-shaped pressure member 35 faces obliquely upward.

Therefore, when the fixing roller 30 is installed, the fixing roller 30 comes into contact with and presses the sheet pressure member 35, and the fixing roller 30 and the sheet pressure member 35 are in pressure contact with each other. become. At this time, the pressure applied from the sheet pressure member 35 to the fixing roller 30 becomes the nip pressure. Since the leaf spring property changes depending on the thickness or material of the sheet pressure member 35, the sheet pressure member 3
The fixing position of the fixing roller 30 is set so as to obtain a desired nip pressure according to the characteristics of No. 5. Further, when the fixing roller 30 is installed, the free end portion of the sheet-like pressure member 35 has a concave portion 34a on the recording paper conveyance direction side with respect to the nip portion.
Close to or abut the stepped part of.

Although the free end is inclined downward when the fixing roller 30 is installed according to FIG. 1, the position may be set so as to be horizontal.

The fixing device shown in FIGS. 1 and 2 is installed in place of the fixing device 8 of the image forming apparatus shown in FIG.

FIG. 3 is an explanatory diagram showing the structure of the path to the transfer, fixing, and discharge of the toner image and its surroundings in the image forming apparatus equipped with the fixing device of the first embodiment.
8 indicates a spur that rotates when it comes into contact with the recording paper,
The spur 38 is provided on the upstream side of the fixing roller 30 in the recording paper conveyance direction and near the central portion of the fixing roller 30 in the longitudinal direction.

FIG. 4 is a perspective view showing the surface of the surface for guiding the recording paper, which has passed through the nip between the photoconductor and the transfer roller in FIG. 3, to the nip between the fixing roller and the sheet-like pressure member. Is a rib that lifts the center of the recording paper, 3
Reference numeral 9 denotes a rib which is lower than the rib 40 and lifts both end portions of the recording paper. The ribs 39 and 40 are a nip portion between the photoconductor 3 and the transfer roller 7 and a nip between the fixing roller 30 and the sheet pressure member 35. It is provided on the guide plate up to the part,
It stands upright in parallel to the recording paper conveyance direction.

Then, the recording paper having passed through the nip portion between the photoconductor 3 and the transfer roller 7 comes into contact with the ribs 39 and 40 provided upright. Here, if the recording paper is elastic, the recording paper is conveyed while contacting the ribs 40, and the fixing roller 3
0 and the sheet-like pressure member 35 enter the nip portion. When the recording paper is not stiff, the central portion is lifted by the ribs 40 during conveyance, and both end portions abut on the ribs 39, 39 to curve in the width direction and project upward as shown in FIG. And the fixing roller 30 is conveyed.
And the sheet-like pressure member 35.

When a backing paper is used as the recording paper, the backing paper is often curled in the width direction.
During conveyance, the central portion of the recording paper becomes high, and when it comes into contact with the fixing roller 30, the conveyance load applied to the recording paper becomes large. Therefore, as shown in FIG. 6, the recording paper may separate from the guide surface in the path from the transfer roller 7 to the fixing roller 30, and the conveying force of the transfer roller may not be transmitted to the leading end of the recording paper. Therefore, a spur 38 is provided to regulate the uppermost position of the recording paper.

Concavities and convexities are formed on the surface of the spur 38 to reduce the area of contact with the recording paper. Further, the height of the spur 38 is set so that the recording paper is stretched between the nip portion between the photoconductor 3 and the transfer roller 7 and the nip portion between the fixing roller and the sheet pressure member 35. It is located at a position close to. Therefore, when the recording paper is normally conveyed, the recording paper does not contact the spur 38, but when the curl of the recording paper is convex upward and the height of the central portion of the recording paper becomes equal to or higher than a predetermined height. The position of the spur 38 is set so as to abut.

With this configuration, when a recording paper having a weak stiffness such as thin paper is used, the rib 40 lifts the central portion of the recording paper and conveys it in a convex state, so that Since the conveyance force of the transfer roller 7 can be transmitted to the nip portion between the fixing roller 30 and the sheet-like pressure member 35 with a small loss, the fixing roller 30 and the sheet-like pressure member 35 can be stably supplied. It becomes possible to invade into the nip part with.

When a recording paper curled in the width direction like a backing paper is used, the uppermost position of the recording paper is restricted by the spur 38, so that the central portion of the recording paper is as shown in FIG. Since it can be prevented from escaping to the fixing roller 30, the conveying force of the transfer roller 7 can be transmitted to the nip portion between the fixing roller 30 and the sheet-shaped pressure member 35 with a small loss, and the fixing roller 30 and the sheet-shaped pressing member can be stably fed. The leading end of the recording paper can be made to enter the nip portion with the pressure member 35.

The spur 38 presses the central portion of the recording paper and is not limited to one, and a plurality of spurs 38 may be provided so as to regulate the positions of the central portion and both end portions of the recording paper.

FIG. 7 is an explanatory view showing the structure of the path to the transfer, fixing, and discharge of the toner image and its surroundings in the image forming apparatus equipped with the fixing device of the second embodiment of the present invention. Is a pedestal that cantilevers the sheet-like pressure member 35 by adhering or fixing one end of the sheet-like pressure member 35 with a double-sided tape or the like; A position restricting member 43, which is an opposite surface of the sheet and abuts against the other end of the sheet-like pressing member 35, restricts the lowest position of the sheet-like pressure member 35. A guide plate that guides the recording paper from the roller 7 to the pedestal 41, 44 is a guide plate that faces the opposite surface of the recording paper from the image forming surface, and guides the recording paper from the fixing roller 30 to the discharge roller 11. 45 is a record To face the image forming surface in,
Below the guide plate that guides the recording paper from the fixing roller 30 to the paper discharge roller 11, 46 is a conveyance roller provided in the conveyance path from the fixing roller 30 to the paper discharge roller 11. The same members or the same functions as those in the conventional technique shown in FIG. 11 or the first embodiment shown in FIGS. 1 to 3 are denoted by the same reference numerals and detailed description thereof is omitted.

The conveyance roller 46 is driven by the fixing roller 30.
Is transmitted by a gear or a belt, and the conveying roller 46 and the fixing roller 30 are set to rotate at substantially the same speed. Then, the recording paper on which the toner image is transferred at the nip portion between the photoconductor 3 and the transfer roller 7 is fixed by the guide of the guide plate 43 to the fixing roller 30.
The leading edge of the recording paper, which has been guided to the nip portion between the sheet-like pressure member 35 and the nip portion, is guided to the discharge roller 11 via the transport roller 46 and discharged.

FIG. 8 is an explanatory diagram showing the carrying load on the recording paper when there is no carrying roller between the fixing roller and the paper discharge roller in FIG.

After the leading edge of the recording paper has passed through the fixing nip portion as shown in FIG. 8A, the recording paper follows the shape of the upper and lower guide plates 44 and 45 as shown in FIG. 8B. However, due to the curvature R of the recording paper, the force Fa is applied in the direction in which the conveyance is hindered. Here, the force Fa is a value obtained by basic characteristics such as the thickness, material, size, orientation of fibers, water content of the recording paper and the radius of curvature R, and the value of Fa when the leading end of the recording paper is closer to the fixing nip portion. Becomes smaller.

If Fb is the recording paper conveyance force,
Since it becomes impossible to carry when Fa ≧ Fb, FIG.
It is desirable that the position of the conveyance roller 46 in the above is located closer to the fixing nip than the position where Fa <Fb.

With this configuration, even when the conveyance path from the fixing roller 30 to the paper discharge roller 11 is bent, the conveyance roller 46 is provided in the middle of the conveyance path, so that the recording paper is newly added. Since various transporting forces can be applied, it becomes possible to stabilize the transport of the recording paper.

[0046]

According to the present invention configured as described above, in a fixing device using a sheet-like pressure member and an image forming apparatus having the fixing device, recording after passing through a transfer nip portion. It is possible to prevent the transportability of the recording paper from being impaired by the transport load on the paper, reduce the occurrence of jams, and obtain a stable fixing operation.

[Brief description of drawings]

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

2 is a front view of FIG.

FIG. 3 is an explanatory diagram showing a configuration of a path from a toner image to a transfer, a fixing, and a sheet discharge, and a periphery thereof in the image forming apparatus including the fixing device of the first embodiment.

FIG. 4 is a perspective view showing a surface of a surface for guiding the recording paper, which has passed through a nip portion between the photoconductor and the transfer roller in FIG. 3, to a nip portion between the fixing roller and the sheet-like pressure member.

5 is a perspective view showing a state of the recording paper passing through the guide surface shown in FIG.

FIG. 6 is an explanatory diagram showing a state where the recording paper has escaped from the guide surface.

FIG. 7 is an explanatory diagram showing a configuration of a path to a transfer, fixing, and discharge of a toner image and its periphery in an image forming apparatus including a fixing device according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a conveyance load applied to the recording paper when there is no conveyance roller between the fixing roller and the paper discharge roller in FIG.

FIG. 9 is a side view showing the internal configuration of a facsimile apparatus having a conventional fixing device and image forming apparatus.

FIG. 10 is a side view showing the internal structure of a conventional fixing device.

FIG. 11 is a side view showing the internal configuration of a facsimile apparatus of the type that discharges recording paper into the body.

[Explanation of symbols]

3 photoconductor 7 Transfer roller 8 fixing device 30 fixing roller 35 Sheet-like pressure member 38 spurs 39, 40 ribs 44 On guide plate 45 under the guide plate 46 Conveyor roller

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kota Takenaka             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F term (reference) 2H033 AA14 AA47 BA08 BA10 BA12                       BB39 CA36 CA40                 2H072 CA01 CB08 JA02 JA04                 3F049 AA01 DA12 LA02 LA05 LA07                       LB03                 3F053 HA08 HB12 LA02 LB03                 3F101 FA01 FB07 FC05 LA02 LA05                       LA07 LB03

Claims (5)

[Claims] 1. A heat transfer member having a heat source inside, and a sheet pressure member contacting and pressing the heat transfer member, wherein one end of the sheet pressure member is recorded on the heat transfer member. The recording paper on which the toner image is transferred is fixed to a mounting portion provided on the upstream side in the paper transport direction, and the other end of the sheet pressing member is brought into contact with the heat transfer member in a pressed state, and the recording paper on which the toner image is transferred is transferred to the heat transfer member. A fixing device for fixing a toner image on a recording sheet by applying pressure / heating when passing through a nip portion between the sheet pressure member and the sheet pressure member, wherein a central portion of a transport guide from the transfer portion to the fixing portion A fixing device provided with means for lifting the central portion of the recording paper so as to raise it to be higher than both end portions. 2. The fixing device according to claim 1, wherein a guide member for guiding the recording paper to the nip portion is provided on the image surface side of the entrance of the fixing nip. 3. A heat transfer member having a heat source inside, and a sheet pressure member contacting and pressurizing the heat transfer member, wherein one end of the sheet pressure member is recorded on the heat transfer member. The recording paper on which the toner image is transferred is fixed to a mounting portion provided on the upstream side in the paper transport direction, and the other end of the sheet pressing member is brought into contact with the heat transfer member in a pressed state, and the recording paper on which the toner image is transferred is transferred to the heat transfer member. A fixing device for fixing a toner image on a recording sheet by applying pressure / heating when passing through a nip portion between the sheet pressing member and the sheet pressing member, up to a sheet discharging unit for discharging the recording sheet from the nip portion. The fixing device is characterized in that the conveying load applied to the recording paper in the conveying path is smaller than the conveying force for conveying the recording paper after passing through the nip portion, and the conveying roller is arranged at a portion of the conveying path. 4. The fixing device according to claim 3, wherein the linear velocities of the conveying roller and the fixing roller are substantially constant. 5. An image forming apparatus comprising the fixing device according to any one of claims 1 to 4.