JPH06202508A - Fixing device for image forming device and image forming device - Google Patents

Abstract

PURPOSE:To prevent the nonuniformity of the fixation of an outputted image caused by the occurrence of wave corrugation, to make a device endurable and simple by constituting a recording material guide member so that a recording material is brought into contact with the surface of a fixing roller before it arrives at a press-contact part and it arrives at the press-contact part along the circumferential direction of the fixing roller by a certain circumferential length or more while it is brought into contact with the surface of the fixing roller. CONSTITUTION:A fixation entrance guide 3 is formed so that the recording material P passed through the press-contact part between a photosensitive drum 1 and a transfer roller 2 is brought into contact with the surface position A on the upstream side of the rotating direction of the fixing roller from the press-contact part N between the fixing roller 4 and the pressure roller 5 of a fixing device 6. Then, a gap G between the tip part of the guide 3 and the surface of the roller 4 is set to be <=1mm. Therefore, the material P guided to the device 6 from the press-contact part is brought into contact with the position A first and it enters the gap part G next. Then, it arrives at the press-contact part N of the rollers 4 and 5 along the circumferential direction of the roller 4 by the fixed circumferential length B or more while it is brought into contact with the surface of the roller 4.

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 with a predetermined pressure, and the pressure contact between the fixing roller and the pressure means. The present invention relates to a fixing device of an image forming apparatus which fixes a non-fixed image formed and carried on a recording material by nipping and conveying the recording material introduced into a section by the fixing roller and a pressing means.

The present invention also relates to an image forming apparatus having an image forming process means section for forming and carrying an unfixed image on a recording material, and a fixing means for heating and fixing the unfixed image of the recording material from the image forming process means section.

[0003]

2. Description of the Related Art Image forming apparatuses such as laser beam printers, LED printers and copiers are used for electrophotography, 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.) in the image forming process means section 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, and the recording material is introduced into a fixing means to fix an unfixed image on the surface of the recording material as a permanent image to form an image-formed product (print, copy). It is to output.

Although various types and structures of fixing means are known, a fixing roller which is heated and temperature-controlled to a predetermined surface temperature and a fixing roller which is brought into contact with the fixing roller with a predetermined pressure are known. A recording medium having an unfixed image formed thereon is introduced into a pressure contact portion (fixing nip portion) of both rollers as a pressure unit, and is nipped and conveyed, whereby the unfixed image is transferred. The heat roller type in which heat is applied to the surface of the recording material by the heat and pressure of the roller pair is the mainstream.

FIG. 11 shows a schematic structure of an example of the heat roller type fixing device. Reference numeral 1 is an image carrier of the image forming process means, 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 a peripheral surface of the photosensitive drum 1 is driven by an unillustrated electrophotographic process device. A toner image corresponding to the image information is formed.

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

The recording material P which has received the toner image 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 a fixing inlet as a recording material guide member of the fixing device 6. Guided by the guide 3, it is conveyed and introduced into the 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 prevention layer 4b formed on the outer peripheral surface thereof, and a heater 4c is incorporated therein. The fixing roller 4 is rotationally driven in the counterclockwise direction indicated by an arrow at a predetermined peripheral speed by a driving unit (not shown), is heated by a heater 4c, and is energized 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 that is brought into contact with the fixing roller 4 by a biasing spring (not shown) at a predetermined pressure, and is rotated by 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 rollers 4 and 5, and a toner image is formed by the heat and pressure of the roller pair 4.5. The recording material P is fixed on the surface.

[0011]

[Problems to be Solved by the Invention] Fixing entrance guide 3 as the above recording material guide member
In general, when the recording material P is set to an angle such that the recording material P contacts 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, recording after fixing is performed. It is known that paper wrinkles easily occur on the material P. For this reason, the fixing entrance guide 3 is often set such that the recording material P first comes into contact with the surface of the fixing roller 4 and is guided to the pressure 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, heat is received from the surface of the fixing roller 4 and the image surface is preheated. The Rukoto. In reality, 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 inlet guide 3 and the surface of the fixing roller 4 is several meters.
A gap G of m is provided, and the recording material P has a pressure contact portion N.
In the contact portion S with the fixing roller 4 in front of, the sheet is conveyed without being subjected to a particularly strong binding force.

When the recording material P containing a large amount of water is conveyed in such a state, the recording material P that has been preheated in the portion S contracts because the water evaporates from the recording material, and FIG.
As shown in FIG. 2, fine waviness Pa may occur on the recording material P immediately before the press contact portion N. When this waving Pa occurs, the amount of preheat received from the surface of the fixing roller 4 differs at the upper and lower portions of the wave at the S portion, and the recording material P is not uniformly preheated.

For this reason, the fixability of the output image that has passed through the pressure contact portion N thereafter becomes nonuniform. This phenomenon is, for example,
When a solid black image on the entire surface of the recording material is output, non-uniformity in fixability corresponding to the fine waviness Pa in the S portion appears in the form of vertical stripes as shown in FIG.

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

In addition to the above drawbacks, the conventional fixing device 6 having such a structure generally fixes the 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 pressure applied between the roller pairs 4 and 5 at the pressure contact portion N is high and the driving load becomes large.

This is, of course, not only the durability of the apparatus 6 is deteriorated, but generally an image forming apparatus often drives a developing device, a transfer device, a fixing device, and conveying rollers by a single motor. Depending on the load of the fixing device,
As a bad influence on the transfer process, it has led to a problem of causing uneven pitch in a halftone image.

Therefore, the present invention solves the above problems in the fixing device 6 of this type, and fixes the output image due to the preheating of the recording material immediately before the pressure contact portion N between the fixing roller 4 and the pressing means 5. The non-uniformity of the properties is prevented, and the fixing performance is improved by positively utilizing the preheating, and the pressure of the pressure contact portion N is reduced. The purpose of.

[0020]. In recent image forming apparatuses, the distance between the image forming process unit 1 and the fixing unit 6 is made as small as possible due to the compact design. In this case, when the heat fixing device (not limited to the heat roller type) as the above-mentioned example is adopted as the fixing means 6, there are the following problems.

That is, when the recording material P is heated by the fixing device 6, the moisture contained in the recording material P becomes water vapor,
The water vapor is generated mainly toward the upstream side of the fixing device 6 in the recording material conveyance direction. The generated water vapor and the hot air (radiant heat) of the fixing device 6 cause rusting of metal parts in the image forming apparatus and increase in temperature in the apparatus.

When the distance between the image forming process means 1 and the fixing device 6 becomes small due to the downsizing of the image forming device, water vapor or hot air generated in the fixing device 6 easily affects the image forming process means. Become.

For example, if it adheres to the surface of the image carrier (photosensitive drum) of the image forming process means, it may adversely affect the formed image or cause deterioration of the image carrier itself.

Further, the developer in the image forming process means is likely to be adversely affected by heat and water vapor.

Therefore, the present invention solves the above problems,
Provided is an image forming apparatus capable of preventing corrosion of device parts, temperature rise in the device, and adverse effects on an image carrier such as a drum and a developer by effectively removing heat and water vapor generated by a fixing unit. This is the second purpose.

[0026]

The present invention provides a fixing device for an image forming apparatus and an image forming apparatus characterized by the following configurations.

(1) A rotary fixing roller having a heating means and a pressure means for urging the recording material to the fixing roller with a predetermined pressure are provided, and the pressure roller is introduced into a pressure contact portion between the fixing roller and the pressure means. A recording material guide member for guiding the recording material to the pressure contact portion in a fixing device for fixing the unfixed image formed and carried on the recording material by nipping and transporting the recording material with the fixing roller and pressure means. The material is configured to contact the surface of the fixing roller before reaching the pressure contact portion, and to reach the pressure contact portion along a circumference of a fixing roller in a circumferential direction while being in contact with the surface of the fixing roller. A fixing device for an image forming apparatus.

(2) It is characterized in that the peripheral length of the surface of the fixing roller that makes the recording material reach the pressure contact portion while being in contact with the surface of the fixing roller is set to 10 ° or more as the wrapping angle of the recording material with respect to the fixing roller ( A fixing device for an 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 surface of the fixing roller with an interval of 1 mm or less. Fixing device.

(4) The fixing device for an image forming apparatus according to any one of (1) to (3), wherein the recording material guide member has a heat-resistant sheet at the tip end on the fixing roller side.

(5) The fixing device for an image forming apparatus according to (4), wherein the heat resistant sheet is in contact with the surface of the fixing roller.

(6) The fixing device for an image forming apparatus according to any one of (1) to (5), wherein the pressing means is a pressing roller.

(7) The pressurizing means is an endless belt-shaped heat-resistant sheet which is suspended by a pair of rollers, rotates, and is in pressure contact with a fixing roller. The fixing device of the image forming apparatus according to any one of claims.

(8) An image forming apparatus having an image forming process means for forming and carrying an unfixed image on a recording material and a fixing means for heating and fixing the unfixed image of the recording material from the image forming process means. An image is formed by removing water vapor generated when the recording material is heated by the fixing unit and hot air of the fixing unit between the casing housing the image forming process unit and the casing housing the fixing unit. An image forming apparatus, comprising: an air passage for preventing the air from wrapping around to the forming unit.

(9) The housing for housing the image forming process means and the housing for housing the fixing means are shielded by a shielding member except for the holes serving as the air passages. The image forming apparatus according to (8), which is characterized.

(10) The image forming apparatus according to (9), wherein the shielding member is made of an elastic material such as sponge.

[0037]

[Operation] By configuring the recording material guide member as described in (1) above and introducing the recording material into the pressure contact portion of the fixing roller pressurizing means, recording is performed at the portion where the recording material contacts the fixing roller before reaching the pressure contact portion. When the material is sufficiently urged to the surface of the fixing roller or has a sufficient wrap angle, the preheating of the recording material at the contact portion is made uniform in the longitudinal direction of the fixing roller and the wavy recording material is generated. And the unevenness of the fixability of the output image due to the occurrence of waviness is prevented. Further, since the fixing property is improved by sufficient preheating of the recording material, it is possible to reduce the pressure applied to the pressure contact portion, which makes it possible to make the fixing device structure durable and simple. Is often reached.

.. Further, by providing the air passage as in the above (8), even when the image forming apparatus is designed to be compact, it is possible to prevent or reduce the wraparound of water vapor or hot air from the fixing unit side to the image forming process unit, and It is possible to prevent the adverse effects of water vapor and heat of the image bearing member and the developer of the forming process means, and to prevent the corrosion of the parts of the apparatus and the temperature rise in the apparatus, so that the second object can be achieved well.

[0039]

【Example】

I. Examples 1 to 4 below are examples of the fixing device of the image forming apparatus having the configuration described in (1) to (7) above.

<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 example is a laser beam printer using a transfer type electrophotographic process.

Reference numeral 10 is a printer main body, and 11 is a front panel portion of the apparatus called a front opening / closing unit, which is not shown by being closed with respect to the printer main body 10 around the lower hinge shaft 12 as shown in FIG. With the state that it is prevented from opening with locking means,
As shown in FIG. 3, the opening and closing / rotating operation can be freely performed in a state in which the lock is released and the printer body is opened by opening the printer body.

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

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 rotationally driven counterclockwise based on the print start signal, and this rotation is performed. The photosensitive drum 1 is subjected to primary charging processing by the charging device 14, and then scanning exposure is performed with a laser beam that is output from the laser scanner 15 and that is modulated corresponding to the time-series electric digital pixel signal of the target image information. By sequentially performing L, the electrostatic latent image corresponding to the target image information is formed on the surface of the rotary photosensitive drum 1. Then, the electrostatic latent image is developed as a toner image by the developing device 16.

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 by the paper feed roller 18 and the separation claw 19 and conveyed from the bottom to the top in the printer body. And reaches the timing roller pair (register roller pair) 20.

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

The recording material P having undergone the toner image transfer is separated from the surface of the photosensitive drum 1 and guided by the fixing entrance guide 3 as a recording material guide member of the fixing device 6 to fix the fixing roller 4 and the pressure roller of the fixing device 6. 5 pressure contact part (fixing nip part)
Then, the toner image is fixed on the sheet, and the sheet is discharged onto the sheet discharge tray 24 on the upper surface of the printer body 10 through the route of the fixing sheet discharge roller pair 7 → sheet path 22 → sheet 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 transfer residual toner, and is repeatedly used for image formation.

The printer of this example is a process in which 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
Is configured as. The fixing device 6 including the transfer roller 2, the fixing entrance guide 3, the fixing roller 4, the pressure roller 5, and the fixing paper discharge roller pair 7 is arranged on the front opening / closing unit 11 side.

Therefore, the front opening / closing unit 11 is tilted and opened from the printer main body 10 as shown in FIG. 3, so that the recording material conveying path in the printer main body is largely opened, and the jammed paper is removed, maintenance / inspection in the printer is performed. The process cartridge 50 can be easily attached / detached and replaced.

The structures of the transfer roller 2, the fixing roller 4, and the pressure roller 5 are the same as those of 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 paper discharge roller pair 7.
Is rotatably supported by the fixing device frame 8.

FIG. 1 is an enlarged view of the 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, which 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 rotation direction of the fixing roller. A guide surface is formed so as to guide the recording material P so as to come into contact with the roller surface position A first, and a gap G between the tip of the guide 3 on the fixing roller side and the surface of the fixing roller 4 is set to 1 mm or less. I am doing it.

As a result, the recording material P guided from the transfer section to the fixing device 6 by the fixing entrance guide 3 first contacts the surface of the fixing roller 4 at the position A, and then the fixing roller 4 and the tip of the guide 3 are narrow. Enter the gap G to enter the recording material P
Of the fixing roller 4 and reaches the pressure contact portion N between the fixing roller 4 and the pressure roller 5 along the circumferential direction of the fixing roller 4 for a certain circumferential length B or more while being in contact with the surface of the fixing roller 4 with the strength of It is nipped and conveyed by this pressure contact portion to receive the fixing of the toner image.

In this embodiment, the peripheral length B of the fixing roller surface is such that the recording material P reaches the pressure contact portion N while being in contact with the surface of the fixing roller.
Is a wrapping angle of the recording material P with respect to the fixing roller 4 (an angle formed by a line connecting the position A and the center O of the fixing roller 4 and a line connecting the recording material inlet position C of the pressure 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 to the pressure contact portion N between the fixing roller 4 and the pressure roller 5 along the surface of the fixing roller, the feeding speed of the recording material P is also influenced. However, in general, if the gap G is expanded by about 1 mm or more, the possibility of occurrence of waviness of the recording material due to preheating of the recording material P due to contact with the fixing roller 4 before reaching the pressure contact portion N becomes 1 mm or less. If this is the case, it has been obtained experimental results that the occurrence can be prevented and the preheating that the recording material P receives before the press contact portion N can be made uniform.

That is, according to this setting, the recording material P is pressed against the press contact portion N.
When the recording material P is sufficiently urged to the surface of the fixing roller 4 at the portion B which comes into contact with the fixing roller 4 before reaching the position B or has a sufficient winding angle θ, the recording material P at the contact portion B is reached. Preheating of P is evenly distributed in the longitudinal direction of the fixing roller 4 to prevent waviness of the recording material P, and to prevent nonuniformity of the fixability of the output image due to waviness. Further, since the fixing property is improved by sufficient preheating of the recording material, the pressing force of the pressure contact portion N can be reduced, and the fixing device configuration can be made durable and simplified, thereby greatly improving the device performance.

<Embodiment 2> (FIG. 4) In this embodiment, with respect to the emplacement apparatus 6 shown in FIG. 1 of Embodiment 1, the fixing roller side tip of the fixing entrance guide 3 is opposed to the fixing roller 4. In addition, it is possible to further increase the effect of the first embodiment by forming the wide circular arc plate portion 3a substantially concentric with the fixing roller 4 to further increase the wrapping angle θ of the recording material P on the fixing roller surface. It is the one.

<Embodiment 3> (FIG. 5) Usually, the fixing inlet guide 3 is often a plastic part, and it was difficult to control the size near the fixing roller at the tip end due to the influence of thermal expansion.

This embodiment solves these problems. The fixing inlet guide 3 shown in FIG. 5 has a thin heat-resistant sheet 3b made of polyimide or the like stuck on the paper-passing surface, and at the tip end thereof, the guide is used. Only the sheet material 3b is in contact with the surface of the fixing roller 4 by protruding 3b '. According to this structure, the tip of the mold portion of the fixing inlet guide 3 has a gap of 1 mm or more with the gap with the fixing roller 4 as in the prior art, and the recording material P is retained by the elasticity of the protruding portion 3b 'of the sheet material 3b. Pressing portion N while urging the surface of the fixing roller 4
It is possible to lead to.

According to this structure, the problem of the dimensional control of the first embodiment is improved, and the elastic force of the protruding portion 3b 'of the sheet material 3b surely fixes the recording material P to the fixing roller 4 before the pressure contact portion.
Since it is possible to bias the surface, the ripple prevention effect is improved and the apparent nip amount increases,
A remarkable improvement in fixing performance is achieved. As a result, it is possible to reduce the pressure contact force of the pressure roller 5 and lower the fixing temperature.

<Embodiment 4> (FIG. 6) The problem of uneven fixing to be solved in the present invention is solved by increasing the wrapping angle (biasing range) of the recording material P around the fixing roller 4. In the third embodiment, the fixing roller 4 for the recording material P is used.
The purpose is achieved by changing the configuration of the biasing / pressurizing means.

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

According to this structure, the biasing range 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.

II. The following Examples 5 to 8 are the same as the above (8).
It is an embodiment of an image forming apparatus having the configuration described in (10) to (10).

<Embodiment 5> (FIG. 7) The printers shown in FIGS. 2 and 3 have a process cartridge 50 as an image forming process means for the downsizing design.
And the distance between the heat fixing device and the fixing device 6 is short,
When the recording material P introduced into the fixing device 6 is heated, water vapor of the recording material-containing water mainly generated toward the upstream side in the recording material conveying direction of the fixing device 6 and hot air of the fixing device 6 are image forming process means. It easily goes around to a portion (process cartridge) and adversely affects the photosensitive drum 1 as an image carrier, the developer and the like.

Therefore, in the present embodiment, the printer shown in FIGS. 2 and 3 is configured to prevent this, and as shown in FIG. 7, the casing 51 of the process cartridge 50 as the casing of the image forming process means, Shielding member 6 for shielding between the fixing device frame 8 which is the casing of the fixing device 6
0 is fixedly provided on the fixing device frame 8, and holes H which serve as a plurality of air passages are provided on the surface of the shielding member 60 in the longitudinal direction (recording material width direction). The holes H can also be in the form of oblong slit holes.

As a result, when the image of the recording material P is fixed, water vapor generated on the upstream side of the fixing device 6 in the recording material conveying direction or hot air of the fixing device 6 is provided with an exhaust fan for preventing the temperature inside the device from rising. As shown by the arrow in FIG. 7 by utilizing the negative pressure of 9, the air passage hole H is passed through before passing around the image forming process means (process cartridge), and the fixing device 6 is fed from the upstream side in the recording material conveying direction. The exhaust fan 9 can be eliminated and discharged to the outside of the machine, and it is possible to prevent water vapor from adhering to the photosensitive drum 1, and to effectively prevent adverse effects on other parts and temperature rise in the apparatus. .

<Embodiment 6> (FIG. 8) This embodiment is the same as the embodiment 5 (FIG. 7) described above with reference to FIG.
Like the cartridge casing 51 of the shielding member 60.
The sponge material 52 is attached to the pressure contact portion with. 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 left open on the printer body side and is openable / closable from the printer body 10, at the contact portion D (FIG. 7) of the shielding member 60 with the process cartridge housing 51. This is done in order to deal with problems such as the fact that there is a gap in the same portion due to dimensional accuracy and it is not possible to uniformly shield. By using an elastic body such as a sponge in the same portion, the cartridge 5 by opening / closing the front opening / closing unit 11 is different from that of the fifth embodiment.
It is possible to further improve the shielding effect while being less affected by the dimensional accuracy in the positional relationship between 0 and the fixing device 6.

<Embodiment 7> (FIG. 9) This embodiment is the same as the embodiment 6 (FIG. 8) described above with reference to FIG.
As described above, the shielding rib 60a is added to the inside of the shielding member 60 in order to further block the flow of hot air and water vapor to the image forming process means side (process cartridge). This has the effect of further improving the effect of the sixth embodiment.

<Embodiment 8> (FIG. 10) In this embodiment, as shown in FIG.
The ribs 52 on the side and the shielding member 60 constitute a non-contact labyrinth. According to this embodiment, it becomes possible to solve the problem of dimensional accuracy due to the contact in the fifth 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 the portion in contact with the fixing roller before the recording material reaches the pressure contact portion, Alternatively, by providing a sufficient wrap angle, the preheating of the recording material at the contact portion is made uniform in the longitudinal direction of the fixing roller to prevent the waviness of the recording material from occurring, and the wrinkling causes the fixing property of the output image to be unsatisfactory. Uniformity is prevented.
Further, since the fixing property is improved by sufficient preheating of the recording material, the pressing force of the pressure contact portion can be reduced, and the fixing device structure can be made durable and simple.

Further, according to the image forming apparatus of the present invention, even when the image forming apparatus is designed to be small in size, it is possible to prevent or reduce the invasion of water vapor or hot air from the fixing means side to the image forming process means portion. It is possible to prevent adverse effects of water vapor and heat of the image carrier and the developer of the image forming process means, and to prevent corrosion of device parts and temperature rise in the device.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a fixing device according to a first exemplary 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 in which a front opening / closing unit of the image forming apparatus is opened.

FIG. 4 is a schematic configuration diagram of a fixing device according to a second embodiment.

FIG. 5 is a schematic configuration diagram of a fixing device according to a third embodiment.

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

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

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

FIG. 9 is a schematic diagram of a main part of an image forming apparatus according to a seventh embodiment.

FIG. 10 is a schematic diagram of a main part of an image forming apparatus according to an eighth embodiment.

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

FIG. 12 is a perspective view showing a state in which the recording material introduced into the pressure contact portion of the fixing roller and the pressure roller is wavy.

FIG. 13 is a diagram showing fixing nonuniformity.

[Explanation of symbols]

 1 Photosensitive Drum as Image Carrier 2 Transfer Roller 3 Fixing Entrance Guide as Recording Material Guide Member 4 Fixing Roller 5 / 5a Pressure Roller or Pressure Belt as Pressure Means 6 Overall Code of Fixing Device 50 Process Cartridge 60 Shielding Material H Air passage hole P Recording material (transfer material)

Claims (10)

[Claims] 1. A rotary fixing roller having a heating means and a pressure means for urging a recording material to the fixing roller with a predetermined pressure, and the pressure roller is introduced into a pressure contact portion between the fixing roller and the pressure means. In a fixing device for fixing an unfixed image formed and carried on a recording material by sandwiching and conveying the recording material with the fixing roller and a pressure means, a recording material guide member for guiding the recording material to the pressure contact portion is used. Is contacted with the surface of the fixing roller before reaching the pressure contact portion, and is contacted with the surface of the fixing roller so as to reach the pressure contact portion along a circumference of the fixing roller over a certain circumferential length. Fixing device for forming device. 2. The peripheral length of the fixing roller surface which makes the recording material reach the pressure contact portion while being in contact with the fixing roller surface is set to be 10 ° or more as a wrapping angle of the recording material with respect to the fixing roller. 1. A fixing device for an image forming apparatus according to item 1. 3. The fixing device for an image forming apparatus according to claim 1, wherein the recording material guide member has a leading end portion on the fixing roller side that is close to the fixing roller surface with an interval of 1 mm or less. apparatus. 4. The recording material guide member has a heat-resistant sheet at the front end on the fixing roller side.
4. A fixing device for an image forming apparatus according to any one of 3 to 3. 5. The fixing device for an image forming apparatus according to claim 4, wherein the heat resistant sheet is in contact with the surface of the fixing roller. 6. The fixing device for an image forming apparatus according to claim 1, wherein the pressure unit is a pressure roller. 7. The endless belt-shaped heat-resistant sheet, wherein the pressing means is suspended and rotated by a roller pair and is in pressure contact with a fixing roller, according to any one of claims 1 to 5. A fixing device for an image forming apparatus according to item 1. 8. An image forming apparatus comprising: an image forming process means section for forming and carrying an unfixed image on a recording material; and a fixing means for heating and fixing the unfixed image of the recording material from the image forming process means section. An image is formed between the housing that houses the image forming process means and the housing that houses the fixing means by eliminating steam generated when the recording material is heated by the fixing means and hot air of the fixing means. An image forming apparatus, characterized in that an air passage is provided to prevent wraparound to the means section side. 9. A shielding member is provided between the housing for accommodating the image forming process means and the housing for accommodating the fixing means, except for a hole serving as the air passage. The image forming apparatus according to claim 8. 10. The image forming apparatus according to claim 9, wherein the shielding member is made of an elastic material such as sponge.