JPH06202506A - Fixing device - Google Patents

Abstract

(57) [Summary] [Objective] Fixing for fixing and fixing an unfixed image on a recording material by introducing and passing the recording material through a fixing nip portion 14 which is a mutual pressure contact portion between the fixing heating means 22 and the fixing pressurizing means 24. To prevent the occurrence of deformation reverse curl of the discharged recording material in the apparatus and eliminate the problem caused by the deformation reverse curl. A recording material guide member 15 disposed on the recording material exit side of the fixing nip portion 14 and guiding the recording material exiting the fixing nip portion has a height with respect to the recording material conveyance direction with respect to a central portion in the width direction. Both end portions 15a are configured to be elevated by a predetermined amount.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus such as a laser beam printer, a copying machine and a facsimile.
The recording material (transfer paper, electrostatic recording paper, electro-fax paper, printing paper, etc.) can be recorded by an indirect (transfer) method or a direct method at an appropriate image forming process means such as electrophotography, electrostatic recording, magnetic recording, etc. The present invention relates to a fixing device that heats and fixes an unfixed image (toner image) corresponding to intended image information formed and carried on a surface as a permanently fixed image on a recording material surface.

[0002]

2. Description of the Related Art Conventionally, as an image heating and fixing device, a heat roller (heat roller) system, that is, a rotary fixing roller as a fixing and heating means consisting of a hollow metal pipe having a halogen heater as a heating source disposed in the center of an inner space is used. (Heat roller)
And a pressure roller serving as a fixing pressure unit having an outer peripheral portion made of an elastic member pressed against the fixing roller, and the recording material is introduced into the fixing nip portion, which is a mutual pressure contact portion between the two roller pairs, and is nipped. A general apparatus is one in which the unfixed image on the recording material surface is fixed by the heat and pressure of the pair of rollers by conveying.

Recently, a film heating type fixing device has been put into practical use. A film heating type fixing device is disclosed in JP-A-63-313182 and JP-A-1-26367.
No. 9, JP-A-2-157878, JP-A-4-
Known from JP-A-44075 to 44083, a heat-resistant film is pressed against a heating body as a fixing heating means by a pressing member as a fixing pressurizing means, and the heating body is sandwiched with the heat-resistant film. A recording material is introduced between the heat-resistant film of the fixing nip portion formed between the pressure member and the pressure member, and the recording material is brought into close contact with the heating body through the heat-resistant film. Is a device for fixing the unfixed image on the surface of the recording material by passing the heat of the heating body to the recording material through the heat resistant film in the fixing nip portion by running the material together with the heat resistant film.

Since such a film heating type fixing device can use a low-heat-capacity heating body or a thin film which can quickly rise in temperature, it consumes less power than other heat fixing devices such as a heat roller type fixing device. It is effective and has the advantages of being able to reduce the wait time (quick start), downsizing, and suppressing the temperature rise inside the main body of the image forming apparatus such as a printer. is there.

As a heating element, a heat-resistant and insulating ceramic substrate made of alumina or the like, and a flat ceramic having a low heat capacity as a whole, which is basically composed of a conductive heating resistor layer made of silver-palladium or the like patterned on the substrate surface. A heater is used.

[0006] FIG. 6 shows the method disclosed in JP-A-4-44075 to 44083.
A schematic configuration of an example of a laser beam printer using a transfer type electrophotographic process, which uses a film heating type fixing device disclosed in Japanese Patent Laid-Open Publication No. 2003-242, is shown.

Reference numeral 50 denotes a printer main body, 1 denotes a process cartridge which can be detachably attached to the printer main body, and which is replaceable in the printer main body. In addition to the rotary drum type electrophotographic photosensitive member 2, although not shown in the drawing, a primary charging device, a developing device, and a cleaning device. Equipment and the like are provided. Based on the print start signal, the rotation driving of the photoconductor 2 is started, and the laser scanner 3 outputs the laser light 4 modulated corresponding to the time-series electric digital pixel signal of the target image information. The photoconductor 2 is scanned and exposed by the light 4 to form an electrostatic latent image corresponding to target image information on the surface of the photoconductor 2, and the latent image is developed as a toner image by a developing device.

On the other hand, a recording material (transfer material) 6 stacked and housed in a paper feed cassette 5 which can be attached to and detached from the front side of the printer at the bottom of the printer forms one sheet by cooperation of a paper feed roller 7 and a separating claw. The sheet is separated and fed, passes through the U-turn sheet path 8 and is conveyed to the transfer nip portion 10 between the photoconductor 2 and the transfer roller 9 at a predetermined timing, and the above-mentioned formation of the surface of the photoconductor 2 on the conveyed recording material. Toner images are sequentially transferred. The photoconductor 2 after transfer is cleaned by a cleaning device and is repeatedly used for image formation.

The recording material exiting the fixing nip portion 10 passes through a conveyance guide 11 and a film heating type fixing device 1 described later.
2 is introduced into the fixing guide nip portion 14 from the entrance guide member 13 to be subjected to heat fixing processing of the toner image, and is guided to the recording material guide member (exit guide member) 15 on the recording material exit side of the fixing nip portion 14. The discharge tray 20 on the upper surface of the printer passes through the path of the first discharge roller pair 16 → reversal guide 17 → second discharge roller pair 18 → sheet discharge outlet 19.
Printed on top (image side) Face-down paper output facing down (F
The paper is ejected in the / D ejection mode.

FIG. 7 is an enlarged view of the fixing device 12. 21
Is a guide stay member (film inner surface guide member) made of heat resistant / heat insulating material, 22 is a flat plate-shaped ceramic heater provided as a fixing heating means on the lower surface of the guide stay member,
Reference numeral 23 denotes a cylindrical heat-resistant thin film (fixing film) loosely fitted on the guide stay member 23 with the heater 22. This fixing film 23 is, for example, several tens.
It is a polyimide / polyamideimide having a thickness of μm.

Reference numeral 24 denotes a pressure roller as a fixing pressure means, which is formed by concentrically forming a heat-resistant rubber layer 24b of silicon rubber or the like having good releasability on a core metal 24a. Two
6 is a fixing device main body frame (shiyashi), 27 is a pressure roller 2
4 bearing member.

The film 23 is sandwiched between the pressure roller 24 and the heater 22, and the pressure roller 24 is pressed against the heater 24 by the pressure spring 25 (for example, by A4). The total pressure is 3 to 6 kg).

A gear (not shown) fixed to one shaft end of the pressure roller 24 meshes with a gear (not shown) of a drive system of the printer body, and is rotated at a predetermined peripheral speed. Due to the surface friction of the pressure roller 24, the cylindrical fixing film 23 is brought into close contact with the lower surface of the heater 22 and slidably driven around the guide stay member 21. That is, when the pressure roller 24 is rotationally driven, the frictional force between the pressure roller 24 (or paper as a recording material) and the outer peripheral surface of the film 23 is larger than that of the inner peripheral surface of the film 23 and the ceramic heater 22. Since it is set to be larger than the frictional force with the surface, the film 23 is driven to rotate.

When the heater 22 is energized by the energization heating resistor, the entire temperature of the heater 22 rises rapidly. And the heater 2
The temperature rise of 2 is detected by the temperature detector, the energization to the energization heating resistor is controlled by the detection information, and the temperature of the heater 22 is controlled to a predetermined fixing temperature.

As described above, the recording material 6 which has received the transfer of the toner image at the transfer nip portion 10 and is conveyed to the fixing device 12 by the conveying guide 11 has the fixing film rotated by the rotation of the pressure roller 24 and the heater. In the heated state of 22, the inlet guide member 13 is introduced between the fixing film 23 and the pressure roller 24 of the fixing nip portion 14, and is brought into close contact with the rotating fixing film 23 and the fixing nip portion together with the fixing film 23. By passing through 14, the heat energy of the heater 22 is given to the recording material 6 via the fixing film 23, and the toner image is heated and fixed.

The recording material 6 exiting the fixing nip portion 14 is guided to the first discharge roller pair 16 by the exit guide member 15.

In the printer as in the above-described example, the fixing nip portion 14 of the fixing device 12 is formed by pressing the elastic pressure roller 24 against the flat heater 22, so that the fixing nip portion 14 is straight or downward slightly along the pressure roller 24. Because of the arc shape, the recording material 6 coming out of the fixing nip portion 14 has a paper curl in the opposite direction of the printing surface (the upper surface side of the recording material 6 in FIG. 7) (hereinafter referred to as reverse curl). Fixing nip 1
Curing is likely to occur on the hot recording material immediately after heating, which comes out of 4, even if it is slightly deformed.

On the other hand, in the laser beam printer or the like, the recording material that has passed through the fixing device 12 is reversed by the reversing guide 17 as in the printer of the above-described example, and the recording surface is turned down from the paper discharge outlet 19 onto the paper discharge tray 20. Since the paper is generally discharged in the face-down mode, the recording material discharged from the fixing device 12 is affected by heat and steam generated by the fixing device 12 (steam generated by heating the water contained in the recording material 6). By passing through the reversing guide 17, paper curl in the same direction as the printing surface (hereinafter referred to as plus curl) is attached.

Accordingly, even if the recording material 6 passes through the fixing nip portion 14 of the fixing device 12 and thus has the reverse curl as described above, the recording material 6 passes through the reversing guide 17 and is thus positively curled, so that the total is obtained. The paper curl is canceled and the paper is ejected onto the paper ejection tray 20 with a good paper curl performance (the curl is corrected). FIG. 8 is a schematic diagram of this.

[0020]

However, even in a printer having such a good paper curl performance, if the temperature of the fixing system is low and is not stable just after starting from cold, the paper curl is not stable. The performance is distorted.

That is, immediately after the cold start up, the temperature of the guide stay member 21 that holds the ceramic heater 22 that immediately becomes high in temperature does not follow the temperature well, and the central portion is different from the longitudinal end portions. The temperature rises first. Further, the temperature distribution of the heater 22 lowers the temperature at both end portions with respect to the central portion, so that the guide stay member 21 does not undergo uniform thermal expansion, and a slight warp occurs in a transient state until reaching a stable temperature.

As a result, in the paper width direction of the fixing nip portion 14, the temperature / pressure balance is lost between the central portion and both end portions, so that the recording material 6 ₁ discharged onto the discharge tray 20 in the face-down mode. Deformed reverse curl occurs as shown in FIG.

Further, as shown in FIGS. 10 and 11, the fixing device 1
In the vicinity of the exit guide member 15 of No. 2, the recording material discharge roller pair 1
In the case of having 6 rollers, the central portion of the recording material 6 is this roller pair 16
The recording material 6 is pulled toward the D direction, and both widthwise end portions of the recording material 6 hang down to the rear end portion B of the exit guide member 15 (the end portion of the exit guide member on the downstream side in the recording material conveyance direction) and the C direction. For this reason, the reverse curl easily occurs at both ends of the recording material in the width direction. The first discharge roller pair 16 is substantially symmetrical in the left-right direction in correspondence with various paper sizes, and is close to the central portion in the recording material width direction.

When the discharged recording material 6 ₁ is deformed and reverse curled as shown in FIG. 9, the discharged recording material 6 ₁ is not aligned on the discharge tray 20 and the alignment is bad, and the recording material 6 1
Conversely curled tip a · a in the width direction end portions of the side after ₁ ledge to position the sheet discharge outlet 19, then nearing the tip of the discharged come recording material 6 ₂ hooked the recording material 6 ₁ The paper may be pushed from above the discharge tray 20 and fall out of the tray.

Therefore, an object of the present invention is to prevent the occurrence of the above-described deformation reverse curl of the recording material and eliminate the above-mentioned problems due to the deformation reverse curl.

[0026]

The present invention is a fixing device having the following configuration.

(1) In a fixing device for introducing and passing a recording material into a fixing nip portion, which is a mutual pressure contact portion between the fixing heating means and the fixing pressure means, to thermally fix an unfixed image on the recording material, the fixing nip The recording material guide member, which is disposed on the recording material outlet side of the recording medium and which guides the recording material that has exited the fixing nip portion, has a height in the recording material conveying direction with respect to the width direction at both ends with respect to the center portion by a predetermined amount. A fixing device characterized by being configured to be high.

(2) In a fixing device for introducing and passing a recording material into a fixing nip portion, which is a mutual pressure contact portion between the fixing heating means and the fixing pressure means, to thermally fix an unfixed image on the recording material, the fixing nip The recording material guide member disposed on the recording material outlet side of the main portion for guiding the recording material exiting the fixing nip portion is a main guide member and a sub guide member movable to both widthwise end portions of the main guide member. The sub guide member has a first position retracted from the recording material guide surface of the main guide member, and a recording material guide member that protrudes from the recording material guide surface of the main guide member and is composed of a main guide member and a sub guide member. The fixing device is movable to a second position where both ends of the recording material in the recording material conveyance direction are higher than the width direction by a predetermined amount.

(3) The fixing device according to (2), wherein the sub-guide member is moved to the first and second positions by the driving means.

(4) The sub guide member is controlled to the first position and the second position by the control means based on the output signal of the temperature detector in the apparatus or the information on the number of passed recording materials. The fixing device according to (2) or (3).

[0031]

As described above, the above-described deformation reverse curl is generated in the guide stay member that holds the ceramic heater as a fixing heating means that immediately becomes high temperature immediately after the apparatus is cold started up. The temperature followability is poor and uniform thermal expansion cannot be obtained.In the transient state until the temperature reaches a stable temperature, the pressure / temperature balance between the longitudinal center of the fixing nip and both ends is disturbed, and the temperature of the heater alone The recording material that has been promoted by the distribution and has exited the fixing nip is shown in FIGS.
As shown in FIG. 1, both end sides tend to hang down with respect to the width direction of the recording material, and further, both ends without the discharge roller hang down. As a result, the reverse curl of the recording material exiting the fixing nip portion of the fixing device is a recording material. Both ends are larger than the center in the width direction, and even if this recording material passes the reversal portion and receives a positive curl, the reverse curl is large as described above. This is because the output tray is reached without being offset.

Therefore, according to the present invention, the height of the recording material guide member (exit guide member) disposed on the recording material exit side of the fixing nip portion and guiding the recording material exiting the fixing nip portion in the recording material conveying direction is set. By constructing both end portions in the width direction with respect to the central portion by a predetermined amount, it is possible to prevent the reverse curl of both end portions in the recording material width direction of the recording material exiting the fixing nip portion of the fixing device from becoming larger than the central portion. This is to prevent the above-mentioned deformation reverse curl from occurring.

[0033]

【Example】

<Embodiment 1> (FIGS. 1 to 3) In this embodiment, the film heating type fixing device 12 in the printer shown in FIG. 6 is arranged on the recording material outlet side of the fixing nip portion 14 as shown in FIGS. The fixing nip portion 1 provided
The guide rib members 15a as sub guide members are provided at both ends of the exit guide member (separation guide) 15 that guides the recording material 6 exiting 4 to the first discharge roller pair 16.
15 a is provided so as to protrude from the recording material guide surface of the exit guide member 15.

The leading end portion A of the exit guide member 15 (the end portion on the upstream side in the recording material conveying direction) is located below the fixing nip portion 14, and the gap α with the outer circumference of the pressure roller 24 is set to 0.
The distance is 5 to 1 mm, and the recording material is peeled off due to the curvature of the outer circumference of the pressure roller 24.

The rear end portion B of the exit guide member 15 (the end portion on the downstream side in the recording material conveying direction) is perpendicular to the pressing direction E of the pressure roller 24 and the guide stay member 21, and the fixing nip portion 1 is formed.
It is the same as or slightly below the tangential direction D from 4. This is because the recording material has a positive curl as the rear end portion B of the exit guide member 15 goes above the line D, and a large positive direction paper curl appears when the recording material is reversed and discharged. The nip portion of the first discharge roller pair 16 is provided near the line D so that the recording material is not curled positively.

The exit guide member 15 has a uniform shape over the entire area except for the guide rib members 15a, 15a at both ends in the recording material width direction, and the guide rib members 15a, 15a are formed.
Is set high up to near the tangent line D.

Therefore, the recording material guided out of the fixing nip portion 14 to the first discharge roller pair 16 by the outlet guide member 15 has the guide rib members 15a on both sides in the width direction.
Since the reverse curl of the recording material, which is guided and supported by 15a above the central portion in the width direction of the recording material, is larger than the central portion in the recording material width direction, the curl of the recording material exiting the fixing nip portion 14 due to the sagging of both end sides The generation of reverse curl due to deformation of the discharged recording material is prevented.

The number of the guide rib members 15a, 15a is not limited to one on each side of the exit guide member 15 in the recording material width direction.

<Embodiment 2> (FIGS. 4 and 5) In this embodiment, a guide rib member 15 as a sub-guide member is used.
a. 15a is a movable member.

That is, as shown in FIGS. 4 (a) and 4 (b), the outlet guide member 15 as the main guide member can freely swing up and down around the fulcrums 15b at both ends in the recording material width direction as sub guide members. Guide rib members 15a ・ 15a
Is provided, and this is controlled by the drive means 15c such as a solenoid to move up and down.

When the main body of the apparatus is cold and the discharged recording material is likely to be deformed and reverse curled as described above, the guide rib members 15a and 15a are attached to the surface of the outlet guide member 15 as shown in FIG. Fixing nip part 1 protruding from above
4 and is displaced to a second position where the height of the recording material guided by the first discharge roller pair 16 in the recording material conveying direction is increased, and the same effect as in the case of the first embodiment is obtained.

In a state where the temperature of the entire apparatus is stable and deformation reverse curl does not occur, the guide rib members 15a, 15a do not project from the upper surface of the outlet guide member 15 as shown in FIG. 4B. To prevent the curl from sticking to both ends of the recording material.

In this way, the curl that changes depending on the state of the fixing device 12 is input to the control circuit (CPU) of the printer in advance, and the output signal of the temperature detector (thermistor or the like) of the device and the number of sheets of recording material passed. Based on the above, the drive means 15c can be controlled to automatically switch the guide rib members 15a, 15a to the first position or the second position as described above.

Switching of the guide rib members 15a, 15a between the first position and the second position is shown in FIG.
As shown in (b), it is also possible to manually switch the time by operating the lever 15d.

[0045]

As described above, the shape of the guide member provided in the vicinity of the downstream side of the fixing nip portion of the fixing device in the recording material conveying direction is formed in a substantially horizontal direction so that the recording material does not have a positive curl. , Both ends are shaped so that they curl up slightly so that there is no reverse curl, and the curl of the recording material immediately after cold start is reversed without changing the overall curl performance and product cost. The curl is improved, and along with that, the effect is that the paper discharge alignment is improved and the number of stacked sheets is increased.

[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 cutaway perspective view of the device.

FIG. 3 is a cutaway perspective view of the apparatus in a recording material conveyance state.

4A and 4B are schematic configuration diagrams of a guide rib member of the fixing device according to the second exemplary embodiment in a second position state and a first position state, respectively.

5A and 5B are schematic configuration diagrams of a guide rib member of a device in which the position of the guide rib member is switched by a manual lever, respectively, in a second position state and a first position state.

FIG. 6 is a schematic configuration diagram of an example of an image forming apparatus (laser beam printer).

FIG. 7 is a schematic configuration diagram of an example of a film heating type fixing device.

FIG. 8 is a schematic diagram of reverse curl, plus curl, and curl correction by cancellation thereof.

FIG. 9 is a perspective view of the printer in which the recording material is ejected onto a paper ejection tray in a deformed reverse curl state.

FIG. 10 is an explanatory diagram of the cause of deformation reverse curl.

FIG. 11 is a cutaway perspective view of the fixing device.

[Explanation of symbols]

 50 General reference code of printer 1 Process cartridge 2 Photoconductor 3 Laser scanner 5 Paper feed cassette 6 Recording material (transfer material) 9 Transfer roller 12 Film heating type fixing device 14 Fixing nip portion 15 Exit guide member 15a Guide rib member 16 First Ejection roller pair 17 Reversing guide 18 Second ejection roller pair 20 Paper ejection tray

Claims (4)

[Claims] 1. A fixing device for thermally fixing an unfixed image on a recording material by introducing and passing the recording material through a fixing nip portion, which is a mutual pressure contact portion between the fixing heating means and the fixing pressure means. The recording material guide member, which is disposed on the recording material exit side and guides the recording material that has exited the fixing nip portion, has a height in the recording material conveying direction that is higher than the center portion in the width direction by a predetermined amount at both ends. A fixing device characterized by being configured. 2. A fixing device for thermally fixing an unfixed image on a recording material by introducing the recording material into a fixing nip portion, which is a mutual pressure contact portion of the fixing heating means and the fixing pressure means, to fix the unfixed image on the recording material. The recording material guide member disposed on the recording material outlet side for guiding the recording material exiting the fixing nip portion includes a main guide member and movable sub-guide members on both end sides in the width direction of the main guide member. The sub guide member has a first position retracted from the recording material guide surface of the main guide member, and a recording material guide member formed of a main guide member and a sub guide member, protruding from the recording material guide surface of the main guide member. A fixing device characterized in that the fixing device is movable to a second position in which the height in the recording material conveyance direction is higher than the width direction by a predetermined amount at both ends. 3. The sub-guide member is moved to first and second positions by a driving means.
The fixing device described in 1. 4. The sub-guide member is controlled to a first position and a second position by a control means based on a temperature detector output signal in the apparatus or information on the number of passed recording materials. The fixing device according to claim 2 or 3.