JP3282258B2 - Fixing device for image forming device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a rotary fixing roller having a heating means and a pressure means for urging a recording material to the fixing roller at a predetermined pressure, and presses the fixing roller with the pressure means. The present invention relates to a fixing device of an image forming apparatus for fixing an unfixed image formed and carried on a recording material by nipping and conveying a recording material introduced into a fixing unit with a fixing roller and a pressing unit.

[0002]

[0003]

2. Description of the Related Art Image forming apparatuses such as laser beam printers, LED printers, and copiers use electrophotographic, electrostatic recording,
An unfixed developer image (toner) corresponding to the target image information on the recording material (transfer material, electrofax sheet, electrostatic recording paper, etc.) by the image forming process means of an appropriate image forming principle and method such as magnetic recording Image) is formed and carried by an indirect method (transfer method) or a direct method, the recording material is introduced into a fixing unit, and an unfixed image is fixed as a permanent image on the recording material surface to form an image formed product (print, copy). Output.

Various types and configurations of fixing means are known. A rotating fixing roller heated and controlled at a predetermined surface temperature, and a fixing means abutting the fixing roller at a predetermined pressure. A non-fixed image is formed by introducing a recording material on which an unfixed image is formed and carried in a pressure contact portion (fixing nip portion) of the two rollers, and nipping and conveying the recording material. The mainstream type is a heat roller type in which fixing is performed on a recording material surface by heat and pressure of a roller pair.

FIG. 11 shows a schematic configuration of an example of the above-mentioned heat roller type fixing device. Reference numeral 1 denotes an image carrier of an image forming process unit, for example, an electrophotographic photosensitive drum. The photosensitive drum 1 is rotationally driven in a counterclockwise direction indicated by an arrow at a predetermined peripheral speed (process speed), and the peripheral surface of the photosensitive drum 1 is driven by an electrophotographic process device (not shown) arranged around the photosensitive drum 1. A toner image corresponding to the image information is formed.

Reference numeral 2 denotes a transfer roller as transfer means,
The photosensitive drum 1 is brought into contact with a predetermined pressure. Further, a predetermined transfer bias is applied. Then, a recording material (transfer material, paper) P is fed from a paper supply unit (not shown) at a predetermined timing to a pressure contact portion (transfer nip portion) between the photosensitive drum 1 and the transfer roller 2, whereby the recording material is transferred. The toner image on the photosensitive drum 1 side is transferred to the surface of P.

The recording material P to which the toner image has been transferred through the pressure contact portion between the photosensitive drum 1 and the transfer roller 2 is separated from the surface of the photosensitive drum 1 and is fixed at a fixing inlet as a recording material guide member of the fixing device 6. The sheet is guided by the guide 3 and is conveyed and introduced to a pressure contact portion N between the fixing roller 4 and the pressure roller 5 of the fixing device 6.

The fixing roller 4 is generally an aluminum cylindrical roller 4a having a toner offset preventing layer 4b formed on the outer peripheral surface, and has a heater 4c built therein. The fixing roller 4 is rotated at a predetermined peripheral speed in a counterclockwise direction indicated by an arrow by a driving unit (not shown), is heated by the heater 4c, and is supplied to the heater 4c by a temperature control system including a temperature sensor (not shown). Is controlled to maintain the temperature of the roller surface at a predetermined fixing temperature.

The pressure roller 5 is a heat-resistant rubber roller brought into contact with the fixing roller 4 at a predetermined pressure by a biasing spring (not shown), and rotates following the rotation of the fixing roller 4.

The recording material P introduced into the pressure contact portion between the fixing roller 4 and the pressure roller 5 is nipped and conveyed by the two rollers 4.5 to form a toner image by the heat and pressure of the roller pair 4.5. The image is fixed on the recording material P surface.

[0011]

On setting of the fixing inlet guide 3 as a recording material guide member above Symbol INVENTION SUMMARY is], generally,
If the recording material P is set at such an angle that the recording material P comes into contact with the surface of the pressure roller 5 of the fixing device 6 and then reaches the pressure contact portion N between the fixing roller 4 and the pressure roller 5, the paper wrinkles on the fixed recording material P. It is known that it is easy to occur. For this reason, the fixing angle of the fixing entrance guide 3 is often set so that the recording material P first comes into contact with the surface of the fixing roller 4 and is guided to the press contact portion N.

However, when the recording material P comes into contact with the surface of the fixing roller 4 before reaching the pressure contact portion N between the fixing roller 4 and the pressure roller 5, it receives heat from the surface of the fixing roller 4 and the image surface is preheated. The Rukoto. In practice, this preheating causes the toner on the image surface to start melting and start fixing.

At this time, generally, as shown in FIG. 11, the distance between the tip of the fixing entrance guide 3 and the surface of the fixing roller 4 is several meters.
m, and the recording material P is pressed against the pressing portion N
Is conveyed without receiving a particularly strong binding force at the contact portion S with the fixing roller 4 in front of.

When the recording material P containing a large amount of water is conveyed in such a state, the recording material P preheated in the S section shrinks due to the evaporation of the water from the recording material, and FIG.
As shown in FIG. 2, fine undulations Pa may be generated on the recording material P immediately before the press contact portion N. When the waving Pa occurs, the amount of preheating received from the surface of the fixing roller 4 differs between the upper and lower portions of the wave in the S portion, and the recording material P is not uniformly preheated.

[0015] For this reason, non-uniformity occurs in the fixability of the output image that has passed through the press contact portion N thereafter. This phenomenon, for example,
When a solid black image is output on the entire surface of the recording material, as shown in FIG. 13, the non-uniformity of the fixing property corresponding to the fine undulation Pa of the S portion appears in a vertical stripe shape.

This is because the upper part of the wave of the waving Pa receives a larger amount of preheating from the surface of the fixing roller than the lower part of the wave, so that the fixing property is different.

In addition to the drawbacks described above, the conventional fixing device 6 having such a configuration generally fixes an unfixed image on the recording material P only by the pressure contact portion N between the fixing roller 4 and the pressure roller 5. Therefore, there is a problem that the pressing force between the roller pair 4 and 5 at the press contact portion N is high and the driving load becomes large.

This is, of course, the deterioration of the durability of the apparatus 6. In general, the image forming apparatus often drives the developing device, the transfer device, the fixing device, and the transport rollers by a single motor. Developing and developing by the load of the fixing device
As a bad influence on the transfer process, there has been a problem of causing pitch unevenness on a halftone image.

Therefore, the present invention solves the above-mentioned problems with this type of fixing device 6 and fixes the output image caused by preheating of the recording material immediately before the pressure contact portion N between the fixing roller 4 and the pressing means 5. thereby preventing the non-uniformity of sex, playing an active improvement of fixing property by utilizing the preheating, such as to reduce the pressure of the pressure contact portion N, purpose to significantly improve the performance of the entire system And

[0020]

[0021]

[0022]

[0023]

[0024]

[0025]

[0026]

The present invention SUMMARY OF THE INVENTION are fixing equipment of images forming device you characterized the following configuration.

(1) A rotary fixing roller having a heating means, and a pressurizing means for urging the fixing roller with a recording material at a predetermined pressure, are provided at a pressure contact portion between the fixing roller and the pressing means. The fixing device for fixing the unfixed image formed and carried on the recording material by nipping and conveying the recording material between the fixing roller and the pressurizing means, a recording material guide member for guiding the recording material to the pressure contact portion, An arc shape along the fixing roller so that the material contacts the fixing roller surface before reaching the pressure contact portion and reaches the pressure contact portion along the fixing roller circumferential direction over a certain circumferential length while being in contact with the fixing roller surface. the fixing device of the image forming apparatus characterized by being configured to.

(2) The peripheral length of the surface of the fixing roller, which causes the recording material to reach the press-contact portion while keeping the recording material in contact with the surface of the fixing roller, is set to a winding angle of the recording material with respect to the fixing roller of 10 ° or more. The fixing device of the image forming apparatus according to 1).

(3) The image forming apparatus according to (1) or (2), wherein the leading end of the recording material guide member on the fixing roller side is close to the fixing roller surface with an interval of 1 mm or less. Fixing device.

[0030]

[0031]

(4) The fixing device of the image forming apparatus according to any one of (1) to (3) , wherein the pressing unit is a pressing roller.

(5) The method according to any one of (1) to (4) , wherein the pressurizing means is an endless belt-shaped heat-resistant sheet that is hung around a pair of rollers and rotates and presses against the fixing roller. A fixing device for the image forming apparatus according to any one of the above.

[0034]

[0035]

[0036]

[0037]

[Action] By be introduced into pressure contact portion between the fixing roller pressing means recording material guide member constitute the recording material as before Symbol (1), contact with the fixing roller before the recording material reaches the contact portion The recording material is sufficiently urged to the surface of the fixing roller in the area where
Thus, the preheating of the recording material at the contact portion is made uniform in the longitudinal direction of the fixing roller, so that the recording material is prevented from waving, and the unevenness of fixing of the output image due to the waving is prevented. Also it is possible to reduce the pressure of the pressure contact portion by fixability improvement in the preheating of sufficient recording medium, the durability of the fixing device configuration, in which simplification like becomes possible, before Symbol <br /> The purpose is well achieved.

[0038]

[0039]

【Example】

Embodiment 1 (FIGS. 1 to 3) FIG. 2 is a schematic configuration diagram of an example of an image forming apparatus to which the fixing device 6 of the present embodiment is applied. The image forming apparatus of this embodiment is a laser beam printer using a transfer type electrophotographic process.

Reference numeral 10 denotes a printer main body, and reference numeral 11 denotes an apparatus front panel portion called a front opening / closing unit, which is closed around the lower hinge shaft 12 with respect to the printer main body 10 as shown in FIG. The state where it is stopped by the lock means,
As shown in FIG. 3, the printer can be freely opened and closed and turned to a state where the lock is released, turned down, and opened to open the inside of the printer body.

Reference numeral 13 denotes a paper cassette which can be inserted into and removed from the lower part of the printer main body from the front side of the printer main body, in which a plurality of transfer materials P as recording materials are stacked and stored.

In the state shown in FIG. 2 in which the front opening / closing unit 11 is closed with respect to the printer body 10, the photosensitive drum 1 as an image carrier is rotated counterclockwise based on a print start signal. The photosensitive drum 1 is subjected to a primary charging process by a charging device 14, and then a scanning exposure by a laser beam output from a laser scanner 15 and modulated according to a time-series electric digital pixel signal of target image information. L is sequentially performed, and an electrostatic latent image corresponding to target image information is formed on the surface of the rotating photosensitive drum 1. Then, the electrostatic latent image is developed by the developing device 16 as a toner image.

On the other hand, the paper feed roller 18 is driven, and the recording material P in the paper cassette 13 is separated and fed one by one by the paper feed roller 18 and the separation claw 19 and is conveyed from the bottom to the top in the printer main body. Then, a timing roller pair (register roller pair) 20 is reached.

The recording material P is fed to the pressure contact portion (transfer nip portion) between the photosensitive drum 1 and the transfer roller 2 at a predetermined timing by the timing roller pair 20 to transfer the toner image on the photosensitive drum 1 surface side. receive.

The recording material P to which the toner image has been transferred is separated from the surface of the photosensitive drum 1 and guided by a fixing entrance guide 3 as a recording material guide member of the fixing device 6 so that the fixing roller 4 and the pressure roller of the fixing device 6 are fixed. 5 (Pressing nip)
Then, the toner image is fixed, and is discharged onto a paper discharge tray 24 on the upper surface of the printer main body 10 through a path of the fixing paper discharge roller pair 7 → the sheet path 22 → the paper discharge roller 23.

The surface of the photosensitive drum 1 after the transfer of the toner image to the recording material P is cleaned by the cleaning device 17 to remove the untransferred toner, and is repeatedly subjected to image formation.

In the printer of this embodiment, the four process devices of the photosensitive drum 1, the charging device 14, the developing device 16, and the cleaning device 17 are collectively attached to and detached from a predetermined storage position in the printer body 1. Cartridge 50
It is constituted as. Further, the transfer roller 2 and the fixing device 6 including the fixing entrance guide 3, the fixing roller 4, the pressure roller 5, and the fixing discharge roller pair 7 are disposed on the front opening / closing unit 11 side.

Therefore, when the front opening / closing unit 11 is tilted and opened from the printer main body 10 as shown in FIG. 3, the recording material conveyance path in the printer main body is largely opened, and the jammed paper removal processing, the maintenance / inspection inside the printer, The attachment / detachment / replacement of the process cartridge 50 can be easily performed.

The structures of the transfer roller 2, the fixing roller 4, and the pressure roller 5 are the same as those in the apparatus shown in FIG. The fixing entrance guide 3 is integrally attached to the fixing device frame 8, and includes a fixing roller 4, a pressure roller 5, and a fixing discharge roller pair 7.
Are rotatably supported by the fixing device frame 8.

FIG. 1 is an enlarged view of a fixing entrance guide 3 as a recording material guide member of the fixing device 6.

The fixing entrance guide 3 in this embodiment is
The recording material P that has passed through the pressure contact portion (transfer portion) between the photosensitive drum 1 and the transfer roller 2 is fixed upstream of the pressure contact portion N between the fixing roller 4 and the pressure roller 5 of the fixing device 6 in the fixing roller rotation direction. Yes forming a guide surface to guide the recording material P as first contact with the roller surface position a, the fixing inlet guide
The tip of the fixing roller 3 on the fixing roller side faces the fixing roller 4,
And the shape of the wide arc plate portion 3a substantially concentric with the fixing roller 4
It is. The gap G between the end of the guide 3 on the fixing roller side and the surface of the fixing roller 4 is set to 1 mm or less.

The recording material P guided from the transfer section to the fixing device 6 by the fixing entrance guide 3 first comes into contact with the surface of the fixing roller 4 at the position A, and then the fixing roller 4 and the end of the guide 3 on the fixing roller side. Arc along the fuser roller
The recording material P enters the narrow gap G with the plate portion 3a and contacts the surface of the fixing roller 4 with the strength of the stiffness of the recording material P, and is fixed along the fixing roller circumferential direction along the circumferential direction of the fixing roller B while being in contact with the fixing roller surface. The toner reaches a pressure contact portion N between the roller 4 and the pressure roller 5 and is nipped and conveyed by the pressure contact portion to receive a toner image fixed thereon.

In this embodiment, the peripheral length B of the fixing roller surface which causes the recording material P to reach the press contact portion N while being in contact with the fixing roller surface
Is the winding angle of the recording material P with respect to the fixing roller 4 (the angle formed by the line connecting the position A and the center O of the fixing roller 4 and the line connecting the recording material inlet position C of the press contact portion N and the center O of the fixing roller 4). ) Θ is set to 30 ° or more.

In such a system in which the recording material P is guided along the surface of the fixing roller to the press contact portion N between the fixing roller 4 and the pressure roller 5, the feeding speed of the recording material P also depends on the feeding speed. However, in general, when the gap G is widened by about 1 mm or more, the possibility that the recording material P is preheated by the contact with the fixing roller 4 before reaching the press contact portion N and that the recording material undulates is increased. Thus, an experimental result has been obtained that the occurrence can be prevented, and the preheating applied to the recording material P in front of the press contact portion N can be made uniform.

That is, a recording material guide for guiding the recording material P to the press contact portion N
The recording member 3 is fixed before the recording material P reaches the pressure contact portion N.
It is in contact with the surface of the roller and
Reaching the press contact portion N along the circumference of the forming roller over a certain circumference
To form an arc along the fixing roller 3
Before the recording material P reaches the press contact portion N, the fixing roller 4
The recording material P is wound around the surface of the fixing roller 4 at a portion B contacting the
As a result, the preheating of the recording material P at the contact portion B is made uniform in the longitudinal direction of the fixing roller 4 so that the recording material P is prevented from waving. Non-uniformity of the fixing property of the output image is prevented. In addition, since the fixing property is improved by sufficient preheating of the recording material, the pressing force of the press contact portion N can be reduced, and the durability and simplification of the configuration of the fixing device can be achieved, thereby greatly improving the performance of the device.

The pressing means is, as shown in FIG.
・ It is hung around 5c and rotates and is in pressure contact with the fixing roller 4.
An endless belt-shaped heat-resistant sheet 5a may be used.

The following is a reference example. <Reference Example 1> (FIG. 4 ) FIG. 4 shows the fixing roller guide 3 in FIG.
The arc plate portion 3a along the fixing roller at the end is omitted.
It is. In contrast to this, Example 1 has a fixing row.
Further increase the winding angle θ of the recording material P around the surface
The effect can be further improved. <Reference Example 2> (FIG. 5) Usually, the fixing entrance guide 3 is often a plastic part, and it is difficult to control the dimensions near the fixing roller at the front end due to thermal expansion and the like.

This embodiment solves those problems. The fixing entrance guide 3 in FIG. 5 has a thin heat-resistant sheet 3b made of polyimide or the like adhered to the paper passing surface. Only the sheet material 3 b projects 3 b ′ and contacts the surface of the fixing roller 4. According to such a configuration, the tip of the mold portion of the fixing entrance guide 3 is not smaller than the gap with the fixing roller 4 and 1 mm or more as in the related art, and the recording material P is moved by the elasticity of the projecting portion 3b 'of the sheet material 3b. Pressing portion N while urging against the surface of fixing roller 4
It is possible to lead to.

According to this configuration, the problem of the dimensional control of the first embodiment is improved, and the recording material P is securely fixed in front of the pressure contact portion by the elastic force of the protrusion 3b 'of the sheet material 3b.
As it is possible to urge the surface, the ripple prevention effect is improved, and the apparent nip amount increases,
A remarkable improvement in fixing performance is achieved. This has the effect of reducing the pressure contact force of the pressure roller 5 and lowering the fixing temperature to the advantage of Reference Example 1 and above.

Reference Example 3 (FIG. 6) The problem of fixing unevenness to be improved in the present invention is solved by increasing the winding angle (urging range) of the recording material P around the fixing roller 4. Reference Example 2 is a fixing roller 4 for a recording material P.
The purpose is achieved by changing the configuration of the urging / pressing means.

In the present embodiment , as shown in FIG. 6, the means for urging and pressing the recording material P to the fixing roller 4 is replaced by two roller pairs 5b instead of the rubber pressure roller 5. An endless belt-like heat-resistant sheet (polyimide sheet or the like) 5a suspended by 5c and rotated and conveyed while being in contact with the surface of the fixing roller 4;

According to this configuration, the range of urging of the recording material P to the fixing roller 4 can be greatly increased as compared with the rubber pressure roller 4, so that the problem of uneven fixing can be solved and the fixing performance can be improved. Can be significantly improved.

The image forming apparatus of recent years is designed by miniaturization design.
The distance between the image forming process unit 1 and the fixing unit 6 can be set
As small as possible. In this case, the fixing unit 6 is described above.
Example of heat fixing device (not limited to heat roller type)
However, the following problems were encountered in the case where (No) was adopted.
That is, the recording material P is heated by the fixing device 6 to record.
The moisture contained in the recording material P becomes steam, and the steam becomes
Mainly emitted toward the upstream side of the fixing device 6 in the recording material conveyance direction.
Live. The generated steam and the hot air (radiant heat) of the fixing device 6 are
Rust metal parts inside the image forming apparatus,
Leads to a rise in degree. And for the miniaturization setting of the image forming apparatus
The distance between the image forming process unit 1 and the fixing device 6
When the separation is small, the water vapor or hot air generated in the fixing device 6
Is likely to adversely affect the image forming process means. An example
For example, the image carrier (photosensitive drive) of the image forming process means section
Adhering to the surface of the
As a result, the image carrier itself is deteriorated.
The developer in the image forming process means is exposed to heat or steam.
Adverse effects. The following Reference Examples 4 to 7 are:
To solve the above problems, the heat generated by the fixing means and
Effective removal of water vapor can cause corrosion of equipment parts and
Elevated temperature, adverse effects on image carrier such as drum and developer
Intended to provide an image forming apparatus capable of this to prevent
is there. .

Reference Example 4 (FIG. 7) The printer shown in FIGS. 2 and 3 has a process cartridge 50 as an image forming process means for miniaturization design.
The distance between the fixing device 6 and the heat fixing device is short.
When the recording material P introduced into the fixing device 6 is heated, the water vapor of the recording material-containing water and the hot air of the fixing device 6 that are mainly generated toward the upstream side of the fixing device 6 in the recording material conveyance direction are heated by the image forming process unit. To the photosensitive drum 1 as an image carrier, a developer, and the like.

In this embodiment, the printer shown in FIGS. 2 and 3 is designed to prevent this. As shown in FIG. 7, a casing 51 of a process cartridge 50 serving as a housing of an image forming process unit is provided. Shielding member 6 for shielding between fixing device frame 8 which is a housing of fixing device 6
0 is fixedly provided on the fixing device frame 8, and a plurality of holes H serving as a plurality of air paths are provided in the surface of the shielding member 60 in the longitudinal direction (recording material width direction). The hole H may be in the form of a horizontally elongated slit hole.

Thus, an exhaust fan provided to prevent the temperature of the fixing device 6 from rising due to the water vapor generated at the upstream side of the fixing device 6 in the recording material conveyance direction and the hot air of the fixing device 6 when the image of the recording material P is fixed. As shown by the arrow in FIG. 7, the negative pressure of the fixing device 6 is passed from the upstream side of the fixing device 6 in the recording material conveyance direction by passing through the air passage hole H before going to the image forming process unit (process cartridge) by using the negative pressure of FIG. The exhaust fan 9 can discharge the gas to the outside of the apparatus, thereby preventing the attachment of water vapor to the photosensitive drum 1 and effectively preventing adverse effects on other components and an increase in temperature in the apparatus. .

<Reference Example 5> (FIG. 8) This reference example is the same as that of Reference Example 4 (FIG. 7) shown in FIG.
, The cartridge casing 51 of the shielding member 60
The sponge material 52 is attached to the pressure contact portion of the above. This is the process cartridge 50 as shown in FIG.
In the image forming apparatus in which the front opening / closing unit 11 including the fixing device 6 is openable and closable with respect to the printer main body 10 while leaving the printer main body side, a contact portion D (FIG. 7) of the shielding member 60 with the process cartridge housing 51 is provided. The purpose of the present invention is to cope with problems such as a gap in the same portion due to dimensional accuracy and inability to shield uniformly. By using an elastic body such as a sponge in the same part, the aforementioned reference example
Cartridge 5 by opening and closing of the front opening and closing unit 11 from 4
The shielding effect can be further improved while being hardly affected by the dimensional accuracy in the positional relationship between the fixing device 6 and the fixing device 6.

<Reference Example 6> (FIG. 9) This reference example is the same as that of the aforementioned reference example 5 (FIG. 8) except that FIG.
As shown in the figure, a blocking rib 60a is added inside the shielding member 60 in order to further prevent hot air and water vapor from flowing to the image forming process means side (process cartridge). Thereby, there is an effect that the effect of the sixth embodiment can be further improved.

< Reference Example 7 > (FIG. 10) In this reference example , as shown in FIG.
The rib 52 on the side and the shielding member 60 constitute a non-contact labyrinth. According to this embodiment, it is possible to solve the problem of the dimensional accuracy caused by the contact of the fourth embodiment.

[0071]

As described above, according to the fixing device of the present invention, the recording material is sufficiently urged to the surface of the fixing roller at a portion where the recording material comes into contact with the fixing roller before reaching the pressure contact portion. Secure winding around the fixing roller and large winding angle
Thus, the preheating of the recording material at the contact portion is made uniform in the longitudinal direction of the fixing roller, so that the recording material is prevented from waving, and the unevenness of fixing of the output image due to the waving is prevented. In addition, since the fixing property is improved by sufficient preheating of the recording material, the pressing force of the press contact portion can be reduced, and the durability and simplification of the fixing device configuration can be achieved.

[0072]

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a fixing device according to a first embodiment.

FIG. 2 is a schematic configuration diagram of an example of an image forming apparatus to which the fixing device is applied;

FIG. 3 is a diagram showing a state where a front opening / closing unit of the image forming apparatus is opened;

FIG. 4 is a schematic configuration diagram of a fixing device of Reference Example 1 .

FIG. 5 is a schematic configuration diagram of a fixing device according to a reference example 2 .

FIG. 6 is a schematic configuration diagram of a fixing device according to a third embodiment.

FIG. 7 is a schematic diagram of a main part of an image forming apparatus according to a fourth embodiment .

FIG. 8 is a schematic diagram of a main part of an image forming apparatus according to a fifth embodiment .

FIG. 9 is a schematic view of a main part of an image forming apparatus according to Reference Example 6 .

FIG. 10 is a schematic view of a main part of an image forming apparatus according to Reference Example 7 ;

FIG. 11 is a schematic configuration diagram of a conventional fixing device.

FIG. 12 is a perspective view showing a state in which a recording material introduced into a pressure contact portion between a fixing roller and a pressure roller has waving;

FIG. 13 is a view showing non-uniformity of fixing.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum as an image carrier 2 Transfer roller 3 Fixing entrance guide as a recording material guide member 4 Fixing roller 5.5a Pressure roller or pressure belt as pressure means 6 Entire code of fixing device 50 Process cartridge 60 Shielding Member H Air hole P Recording material (transfer material)

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-50-106642 (JP, A) JP-A-57-176077 (JP, A) JP-A-51-224072 (JP, A) 7947 (JP, U) Fully open sho 53-117246 (JP, U) Fully open sho 55-164648 (JP, U) Fully open sho 63-86656 (JP, U) (58) Fields investigated (Int. ⁷ , DB name) G03G 15/20

Claims (5)

(57) [Claims] 1. A fixing device comprising: a rotary fixing roller having a heating unit; and a pressing unit for urging a recording material at a predetermined pressure to the fixing roller, and is introduced into a pressure contact portion between the fixing roller and the pressing unit. In a fixing device for fixing an unfixed image formed and carried on a recording material by nipping and conveying the recording material with the fixing roller and a pressing unit, a recording material guide member for guiding the recording material to the pressing portion includes a recording material guide member. fixing so they said contact previously surface of the fixing roller to reach the contact portion, and along more than a predetermined peripheral length to leave the fixing roller circumferential direction in contact with the fixing roller surface reaches to the pressure contact portion
A fixing device for an image forming apparatus, wherein the fixing device is formed in an arc shape along a roller . 2. The fixing device according to claim 1, wherein the peripheral length of the surface of the fixing roller, which causes the recording material to reach the press-contact portion while keeping the recording material in contact with the surface of the fixing roller, is set to a winding angle of the recording material around the fixing roller of 10 ° or more. 2. A fixing device for an image forming apparatus according to claim 1. 3. The fixing device according to claim 1, wherein the recording material guide member has a tip on a fixing roller side close to a surface of the fixing roller with an interval of 1 mm or less. apparatus. 4. A fixing device for an image forming apparatus according to any one of claims 1 to same 3, wherein said pressurizing means is a pressure roller. Wherein said pressurizing means is any one of claims 1 to same 4, characterized in that is wound suspended in the roller pair which is an endless belt shaped heat resistant sheet being pressed against the rotating fixed roller 5. A fixing device for an image forming apparatus according to claim 1.