JPH08254913A - Fixing device and image forming device - Google Patents

Abstract

PURPOSE: To provide a fixing device where the wrinkles of paper and the leaping of the trailing edge of the paper are not caused even when the hardness and the outside diameter of a pressure roller are changed. CONSTITUTION: An entrance guide 7 disposed ahead of a nip N and guiding a recording material is disposed turnably around a fulcrum S, and the strength and the accuracy of the entrance guide 7 are secured by a stainless stay 701. Then, the stay 701 is positioned by the working point M interlocked with the position of the core metal 301 of the pressure roller 3 by an iron coupling bar 9 which can be turned around the fulcrum S. Thus, when the position of the core metal 301 is changed in directions P1 and P2 because of the change of durability of the hardness of the pressure roller 3, the coupling bar 9 moves the stay 701 in accordance with the change, and the position of the leading edge of the guide 7 is adjusted in directions G1 and G2 in figure according to the position of the entrance part of the nip N estimated from the position of the core metal 301.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device of a type in which heat energy from a heating element is applied to a recording material by radiation or conduction, and an image forming apparatus equipped with this fixing device.

[0002]

2. Description of the Related Art Conventionally, in an image forming apparatus such as an electrophotographic copying machine, a printer and a fax machine, an appropriate image forming process means such as electrophotography, electrostatic recording and magnetic recording is used.
An unfixed toner image is directly or indirectly formed on the surface of the recording material by using a toner made of a heat-meltable resin, and the unfixed toner image is heated and pressed together with the recording material to form a recording material surface. An image is formed by fixing the image as a permanently fixed image.

For example, in an electrophotographic laser beam printer as shown in FIG. 9, first, the intensity of laser light is modulated by a scanner 21 which is an exposing means based on an image information signal sent from a host computer, and a charging means. The surface of the photosensitive drum 23, which is an image carrier uniformly charged, is irradiated by the barrel charger 22 to form an electrostatic latent image. Next, by rotating the photosensitive drum 23 in the direction of the arrow, the electrostatic latent image is conveyed to the opposing portion between the developing device 24 and the photosensitive drum 23, and is sequentially developed by the developing device 24. Then, the developed toner image is sequentially transferred by the transfer device 26 to the copy paper P which is a recording material sent from the paper feeding device 25, and the paper P on which the toner image is transferred is separated as the photosensitive drum 23 rotates. Then, it is sent to the fixing device 28 via the conveyance guide 27. As the transfer device 26, in addition to the corona charger shown in the figure, there is a transfer roller system in which a current is supplied from a power source to the conductive elastic rotating member to convey the paper while applying transfer charge.

Further, the fixing device 28 has a structure as shown in FIG. 10, and is configured to satisfactorily fix and discharge the toner image transferred onto the paper P as described above. Hereinafter, the configuration of the fixing device 28 will be described in detail.

A fixing roller 1 on the upper side in the figure is a hollow cored bar 101 made of aluminum, iron or the like, in which a heater 2 such as a halogen lamp is placed as a heating element in the inner space. Is heated. 102
Is an anti-offset layer for improving the surface properties of the fixing roller 1, and a coating of fluororesin or a tube is preferably used. The pressure roller 3 on the lower side of the drawing covers the outer periphery of a core metal 301 made of iron, stainless steel or the like with an elastic body 302 having releasability such as silicone rubber, and further the elastic body 30
2 is provided with a release layer 303 such as a PFA tube. The fixing roller 1 and the pressure roller 3 have a bearing 401.
The springs 4 are urged through them to bring them into contact with each other with a predetermined pressing force, and they are rotationally driven in the direction of the arrow. The urging means such as the spring 4 functions to adjust the axes of both rollers, especially the eccentricity and deformation of the pressure roller 3 which is an elastic body, to secure the pressing force and the nip width. There is.

Reference numeral 5 is an NTC which is in contact with the surface of the fixing roller 1.
It is a temperature-sensitive element such as, and detects the surface temperature of the fixing roller 1. The temperature control circuit controls the energization of the heater 2 according to the temperature detected by the temperature sensitive element 5, and the surface temperature of the fixing roller 1 is automatically controlled to a predetermined thermal fixing temperature, and the energization is shut off at an abnormal temperature. Work as a device. Denoted at 6 is a separation claw for separating the sheet P from the surface of the fixing roller 1, and is arranged such that the leading edge portion is in contact with the surface of the fixing roller 1 with an appropriate pressure. Reference numerals 7 and 8 denote an entrance guide and an exit guide for guiding the sheet of the fixing device, which are attached to and supported by the bottom plate 10 and the top plate 11, respectively. The paper P guided by the entrance guide 7 and entering the fixing device passes through the nip portion between the fixing roller 1 and the pressure roller 3 which are in pressure contact with each other and are rotationally driven. In the course of this passage, the unfixed toner image Ta on the paper P is fixed as a permanently fixed image Tb by heat and pressure.

The sheet P, which has passed through the nip portion of the rollers 1 and 3 and has undergone image fixing, is separated from the surface of the fixing roller 1 by the separating claw 6 and is discharged to the outside of the fixing device through the exit guide 8.

[0008]

However, in the conventional fixing device, the nip width may change not only due to individual differences but also due to use time due to durability change or dispersion of the hardness of the elastic pressure roller 3. However, since the position of the nip entrance portion changes, the relative positional relationship between the entrance guide 7 and the nip entrance portion may change, and paper wrinkles, trailing edge splashes, and the like may occur.

In particular, in a high-speed machine which requires high precision in the relative positional relationship, paper wrinkles, trailing edge bounces and the like are likely to occur due to changes in the position of the nip entrance.

In addition, the proper relative position between the entrance guide 7 and the nip entrance portion in the above-mentioned ordinary paper is not always preferable for a thick and special recording material such as an envelope, and especially the clearance at the nip entrance portion. However, when the envelope is not ensured, the envelope may come into contact with the fixing roller 1 to cause image misregistration or a jam before the envelope enters the nip.

As a result, there are cases where the speeding up of the image forming apparatus is hindered, and thick paper such as envelopes cannot be used in the image forming apparatus.

An object of the first invention of the present application is to prevent paper wrinkles and wrinkles even when the hardness or outer diameter of the pressure roller changes for both ordinary recording materials and special recording materials such as envelopes. It is an object of the present invention to provide a fixing device that exhibits good conveyance properties without trailing edge bounce and image shift.

The second invention of the present application is, in addition to the above object, an object of the present invention to provide a fixing device capable of more reliably preventing the occurrence of paper wrinkles.

Further, in addition to the above object, a third invention of the present application aims at providing a fixing device capable of preventing image shift when thick paper such as an envelope is used.

The fourth object of the present invention is to:
Performs good image formation on both ordinary recording materials and special recording materials such as envelopes, without wrinkles, trailing edge jumps, and image shifts, even when the hardness or outer diameter of the pressure roller changes. It is to provide an image forming apparatus capable of performing the above.

Further, in addition to the above-mentioned object, a fifth invention of the present application aims to provide an image forming apparatus capable of more reliably preventing the occurrence of paper wrinkles.

In addition to the above object, a sixth invention of the present application aims to provide an image forming apparatus capable of preventing image shift when thick paper such as an envelope is used.

[0018]

According to the first invention of the present application, the above object is to provide a fixing roller containing a heating element or a fixing film slidingly in contact with the heating element, and directly or on the fixing roller. A pressure roller having an elastic layer biased so as to be indirectly pressure-contacted to the heating element via the fixing film; and an inlet guide for guiding a recording material to the pressure-contact portion,
In the fixing device for fixing the unfixed image on the recording material by nipping and conveying the recording material on which the unfixed image is formed at the pressure contact portion, the entrance guide has a guide surface. The pressure roller is rotatably arranged around a central axis substantially parallel to the rotation center of the pressure roller, and rotates in accordance with the position change of the rotation center of the pressure roller in the urging direction and the anti-urging direction. This is achieved by being connected to a movable member that is rotatable about a central axis that is substantially parallel to the center.

According to the second invention of the present application,
The above object can be achieved in the first aspect of the present invention, in which the outer diameter of the axial center portion of the pressure roller is smaller than the outer diameter of the axial end portion.

Further, according to a third invention of the present application, in the first or second invention described above, the object is to have a pressing force adjusting mechanism for the fixing roller of the pressure roller or the heating element. Achieved by

According to the fourth invention of the present application,
The above-mentioned objects are: an image carrier having a photosensitive layer, a charging unit for charging the image carrier, an exposing unit for exposing the charged image carrier, and an electrostatic latent image formed on the image carrier. A developing device for developing the image with a developer, a recording material supply means for supplying the recording material, a transfer device for transferring the unfixed image formed on the image carrier onto the recording material,
A pressure roller having an elastic layer urged to directly contact the fixing roller containing the heating element or indirectly through the fixing film, and a recording material is guided to the pressing portion. A fixing device provided with an entrance guide to
An image forming apparatus for forming an image by fixing the unfixed image on the recording material by heating and pressurizing the recording material, to which the unfixed image is transferred, while sandwiching and transporting the recording material at a pressure contact portion of the fixing device. The entrance guide of the fixing device is arranged so that the guide surface is rotatable about a central axis substantially parallel to the rotation center of the pressure roller, and the biasing direction and the counter bias of the rotation center of the pressure roller are provided. This is achieved by being connected to a movable member that is rotatable around a central axis that is substantially parallel to the rotation center, following a change in position in the direction.

Further, according to the fifth invention of the present application, in the above-mentioned fourth invention, the outer diameter of the axial center portion of the pressure roller is smaller than the outer diameter of the axial end portion. It is achieved by being.

According to the sixth invention of the present application,
The above-mentioned object can be achieved by having a pressing force adjusting mechanism for the fixing roller of the pressure roller or the heating element in the fourth invention or the fifth invention.

[0024]

According to the first aspect of the present invention, when the position of the center of rotation of the pressure roller changes in the urging direction and the anti-urging direction due to the deformation of the elastic layer or the eccentricity of the pressure roller. First, the movable member rotates following the change, and the inlet guide connected to the movable member is rotated about a central axis substantially parallel to the rotation center of the pressure roller. Therefore, even if the position of the pressure contact portion formed directly with the fixing roller or indirectly with the heating element via the fixing film changes due to the position change of the rotation center of the pressure roller,
The position of the inlet guide with respect to the press contact is maintained in a proper position.

According to the second invention of the present application,
In the first aspect of the invention, since the outer diameter of the central portion of the pressure roller in the axial direction is smaller than the outer diameter of the end portion in the axial direction, a difference occurs in the conveying speed of the recording material between the central portion and the end portion, and recording is performed. The material is pulled to both ends. Therefore, in combination with the operation of the first aspect of the invention, the occurrence of wrinkles in the recording material can be suppressed well.

Further, according to the third invention of the present application, in the first invention or the second invention, since there is a pressurizing force adjusting mechanism for the fixing roller of the pressure roller or the heating element, an envelope or the like is provided. In the case of using thick paper, when the pressure of the pressure contact portion is released by the pressing force adjusting mechanism, the center of rotation of the pressure roller moves downward and the movable member lowers the leading end position of the inlet guide, thereby making it possible to use thick paper such as envelopes. Ensure the clearance at the inlet of the pressure contact part. As a result, the occurrence of image shift is suppressed.

According to the fourth invention of the present application,
When the position of the rotation center of the pressure roller in the fixing device changes in the urging direction or the anti-urging direction due to the deformation of the elastic layer or the eccentricity of the pressure roller, the movable member follows the change. It rotates and rotates the inlet guide connected to the movable member around a central axis substantially parallel to the rotation center of the pressure roller. Therefore, in the fixing device, the position of the pressure contact portion formed directly with the fixing roller or indirectly with the heat generating body via the fixing film is changed by the position variation of the rotation center of the pressure roller. Even if it does, the position of the inlet guide with respect to the press contact portion is maintained in an appropriate position,
Good image formation without paper wrinkles is performed.

Further, according to the fifth invention of the present application, in the fourth invention, the outer diameter of the axial center portion of the pressure roller in the fixing device is smaller than the outer diameter of the axial end portion. Therefore, a difference occurs in the conveyance speed of the recording material between the central portion and the end portion, and the recording material is pulled toward both ends. Therefore,
In combination with the action of the fourth aspect of the invention, wrinkling of the recording material is suppressed well, and good image formation is performed.

According to the sixth invention of the present application,
In the fourth invention or the fifth invention, since the pressurizing roller of the fixing device has a pressing force adjusting mechanism for the fixing roller or the heating element, when thick paper such as an envelope is used, the pressing force adjusting mechanism is used to When the pressure at the pressure contact portion is released, the center of rotation of the pressure roller moves downward, and the movable member lowers the tip position of the inlet guide to secure a clearance at the pressure contact portion inlet for thick paper such as an envelope. As a result, the occurrence of image shift is suppressed, and good image formation is performed.

[0030]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

(First Embodiment) First, a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 2 is a view showing the arrangement of an electrophotographic laser beam printer according to this embodiment. In the figure, 21 is a scanner as an exposing means, which modulates the intensity of laser light by the scanner 21 based on an image information signal sent from a host computer, and uniformly charges the surface by a charger 22 as a charging means. The photosensitive drum 23, which is the image carrier thus formed, is irradiated to form an electrostatic latent image. This electrostatic latent image is conveyed to the opposing portion between the developing device 24 and the photosensitive drum 23 by the rotation of the photosensitive drum 23 in the direction of the arrow, and the developing device 2
4 sequentially develops. Then, the developed toner image is sequentially transferred by a transfer device 26 to a copy paper P which is a recording material sent from a paper feeding device 25 which is a recording material supply means, and the paper on which the toner image is transferred is the photosensitive drum 23.
The sheet is separated as it rotates and is sent to the fixing device 29 through the conveyance guide 27. As the transfer device 26, in addition to the corona charger shown in the figure, there is a transfer roller system in which a current is supplied from a power source to the conductive elastic rotating member to convey the paper while applying transfer charge.

The fixing device 29 in this embodiment as described above is constituted as follows, and paper wrinkles,
It is designed not to cause the trailing edge bounce and the image shift. The configuration of the fixing device 29 in this embodiment will be described below.

FIG. 1 is a diagram showing the construction of a fixing device 29 in the first embodiment of the present invention. In FIG. 1, 1 is a cylindrical core metal 10 made of aluminum having a thickness of 2 mm and an outer diameter of 30 mm.
1 is a fixing roller which is a heat conductive member in which a release layer 102 is coated with a PFA tube having a thickness of 30 μm. Inside the fixing roller 1, a halogen heater 2 as a heating element having a heat generating capacity of 600 W (when inputting 100 V) is arranged, and heat is supplied to the fixing roller 1.

Below the fixing roller 1, a solid silicone rubber layer 302 is provided around an iron cored bar 301.
As the release layer 303, a pressure roller 3 having an outer diameter of 30 mm, which is covered with a PFA tube of 50 μm, is provided.
The pressure roller 3 is biased by a coil spring 4 having a spring constant of 6.0 × 10 ⁴ N / m to form a nip N with the fixing roller 1. Further, the core metal 301 of the pressure roller 3
Are supported by bearings 401. The bearings 401 smooth the rotation of the pressure roller 3, and the pressure of the coil spring 4 is appropriately transmitted to the pressure roller core metal 301.

Further, above the fixing roller 1, an NTC element 5 whose electric resistance value changes with temperature is in contact with the surface of the fixing roller 1 with a light pressure, and is heated by the halogen heater 2. It is possible to detect the temperature of.

A separating claw 6 for separating the leading end of the recording material from the fixing roller 1 is arranged near the nip between the fixing roller 1 and the pressure roller 3, and the separating claw 6 is provided. Is formed by coating PFA resin on polyimide resin.

In front of the nip N, an entrance guide 7 for guiding the recording material to the nip N is disposed so as to be rotatable around a fulcrum S. The accuracy is ensured by the stainless stay 701. Further, the stay 701 is positioned at the action point M by interlocking with the position of the core metal 301 of the pressure roller 3 by the iron connecting rod 9 which is a movable member rotatable about the fulcrum S. There is.

Behind the nip N, an exit guide 8 for guiding the recording material discharged from the nip N to the outside of the fixing device.
Is attached to an iron bottom plate 10 that supports the pressure of the winding spring 4, and the upper portion of the fixing roller 1 is protected by a top plate 11 to prevent the fixing roller 1 from releasing heat.

When the power source is turned on in the apparatus of this embodiment as described above, a controller (not shown) detects the electric resistance value of the NTC element 5, and feedback-controls the current flowing to the halogen heater 2 to fix the fixing roller 1. The surface temperature of is automatically controlled to 190 ° C. which is the proper fixing temperature. At this time, the pressure roller 3 is rotated by the coil spring 4 with respect to the fixing roller 1.
The pressure roller 3 is pressed with a force of 0 N and has a hardness of As.
The ker-C (weighted with 500 g) is 45 degrees, and the nip N is formed to be about 5 mm. The width of the nip N is set to be necessary and sufficient for fixing the toner image on the recording material as a permanently fixed image.

However, the nip N moves in the P1 direction or the P2 direction shown in FIG. 1 due to changes in the hardness of the pressure roller 3 and the like, and the relative positional relationship with the inlet guide 7 tends to change. There is a pressure roller 3 like this
When the position of the core bar 301 of the pressure roller 3 changes in the P1 and P2 directions in the figure, the connecting rod 9 drives the stay 701 according to this change, and the nip N inlet portion estimated from the position of the core bar 301 of the pressure roller 3 is introduced. The tip position of the inlet guide 7 is adjusted in the directions G1 and G2 in the figure according to the position of.

Therefore, the front end position of the entrance guide 7 is adjusted to a height which exactly intersects the tangent line 1 of the nip N entrance portion of the fixing roller 1, and causes various problems in conveying the recording material, for example, after wrinkles of thin paper or thick paper. Prevents edge bounce.

According to the experiment, the accuracy of the tip position of the entrance guide 7 with respect to the entrance portion of the nip N in order to prevent such various problems in conveying the recording material is ± even if it is loose.
About 1 mm, ± 0.2 m in high-speed image forming apparatus
It turned out that it is a strict thing called m. On the other hand, the elastic layer 302 of the pressure roller 3 has a characteristic that the hardness is relatively large depending on the temperature and the endurance time, and the hardness varies by about ± 3 degrees in the manufacturing process. Therefore, it may fluctuate within a maximum width of 3 mm. However, the configuration of the present embodiment can secure the relative position between the tip end position of the inlet guide 7 and the inlet portion of the nip N even in such a case.

The frequency of occurrence of wrinkles of thin paper and bouncing of the rear end of thick paper when the hardness of the pressure roller 3 varies will be described below.
The results of comparison between the conventional fixing device and the fixing device of the present embodiment for an image forming apparatus having a printing speed of 16 sheets of A4 size paper per minute are shown.

[0044]

[Table 1]

As can be seen from Table 1, in this embodiment, even when the hardness of the pressure roller 3 fluctuates, the inlet guide 7 can be moved along with the movement of the core 301 which reflects the change in the inlet position of the nip N. By making the leading end position of the entrance guide 7 follow by the connecting rod 9, the frequency of occurrence of paper wrinkles and trailing edge bounce is suppressed compared to the conventional fixing device, and the fixing device having good recording material conveyance property is realized. did it.

As a development of this embodiment, there can be mentioned a pressure roller 3 having a shape in which the outer diameter of the central portion in the axial direction is smaller than the outer diameter of the end portion in the axial direction. In such a case, a high effect of preventing paper wrinkles can be obtained by creating a difference in the conveyance speed between the end portion and the central portion, and further, the rear end bounce caused by the stress applied to the recording material by the conveyance speed difference can be obtained. On the other hand, with the above configuration, the relative position between the inlet guide and the nip inlet can be prevented by maintaining an appropriate position, and a fixing device having better recording material transportability can be realized.

Further, by providing the fixing device in the image forming apparatus, excellent image formation can be performed even when the speed of the image forming apparatus is increased.

(Second Embodiment) Next, a second embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 3 is a diagram showing a fixing device according to a second embodiment of the present invention, and this embodiment device is also used in the image forming apparatus as shown in FIG. 90 in FIG.
Numeral 1 is a roller made of PFA resin, which is a movable member disposed in the center of the sheet passing width of the inlet guide 7, and is in contact with the surface of the pressure roller 3.

The width of the nip N fluctuates due to variations and changes in the hardness of the pressure roller 3, and the position of the entrance of the nip N also changes accordingly, but the position of the roller 901 is pressed in addition to such changes. It also follows subtle changes in the nip N when the roller 3 thermally expands or when the outer diameter changes.
Further, since the leading end position of the entrance guide 7 in the central portion of the sheet passing width, which requires the most accuracy, is directly interlocked, the entrance guide 7 is provided to obtain good conveyance of the recording material with respect to variations in the nip width. It was possible to obtain the effect of easily obtaining the position.

Further, by providing the above-mentioned fixing device in the image forming apparatus, it is possible to perform more excellent image formation even when the image forming apparatus is speeded up.

(Third Embodiment) Next, a third embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 4 is a drawing showing the fixing device in this embodiment, and the device of this embodiment is also used in the image forming apparatus as shown in FIG. In FIG. 4, reference numeral 902 indicates the stay 7 at the action point M in association with the position of the pressure roller core metal 301.
A connecting rod made of iron, which is a movable member rotatable about a fulcrum T for positioning 01, 903 is an iron support plate providing the fulcrum T of the connecting rod 902.

The connecting rod 902 follows the stay 701 according to the change of the position of the pressure roller core metal 301, and the inlet guide 7 according to the position of the nip N inlet portion estimated from the position of the pressure roller core metal 301. The leading end position of the inlet guide 7 is adjusted to prevent various problems in recording material conveyance, such as thin paper wrinkles and thick paper trailing end bounce. Since the distance between T and the point of action M is long, it is possible to change the position of the pressure roller core metal 301 due to the change of the tip position of the inlet guide 7 and obtain a weight for adjusting the pressing force. Become.

Due to this action, when the envelope is passed, the inlet guide 7 is pushed down by the strong waist of the envelope to reduce the pressure,
The effect of preventing the occurrence of envelope wrinkles can be obtained.

The frequency of occurrence of paper wrinkles, trailing edge bounces, and envelope wrinkles in the case where the hardness of the pressure roller 3 varies in the following will be described in a conventional image forming apparatus at a printing speed of 10 sheets of A4 size paper per minute. The results of comparison between the case where the fixing device is used and the case where the fixing device of this embodiment is used are shown.

[0057]

[Table 2]

As can be seen from Table 2, in this embodiment, even when the hardness of the pressure roller 3 is varied, the inlet guide 7 can be moved along with the movement of the core metal 301 which reflects the change in the inlet position of the nip N. Then, the entrance guide 7 is formed by the connecting rod 902.
By following the leading edge position of the paper, in addition to the effect of suppressing the occurrence frequency of paper wrinkles and trailing edge splash compared with the conventional fixing device, the frequency of wrinkle occurrence is drastically reduced during the passage of envelopes. I was able to get the effect.

Further, by providing the above-mentioned fixing device in the image forming apparatus, not only good image formation can be performed even when the image forming apparatus is sped up, but also thick paper such as an envelope is used in the image forming apparatus. Even in this case, good image formation without wrinkles can be performed.

(Fourth Embodiment) Next, a fourth embodiment of the present invention will be described with reference to FIG. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

FIG. 5 is a drawing showing a fixing device in a fourth embodiment of the present invention, and this embodiment device is also used in the image forming apparatus as shown in FIG. In FIG. 5, reference numeral 402 is a pressure release lever, and 403 is a pressure release lever 40.
It is an insertion rod connected to 2, and these constitute a pressing force adjusting mechanism.

The coil spring 4 has a spring constant of 2.0.
The nip N is formed with a pressing force of 210 N by using a material of × 10 ⁵ N / m, which corresponds to a high-speed image forming apparatus.

The connecting rod 9 is provided with a stay 701 according to the change of the position of the pressure roller core metal 301, as in the above-mentioned embodiment.
To adjust the tip position of the inlet guide 7 according to the position of the nip N inlet portion estimated from the position of the pressure roller core metal 301.

In this embodiment, since the coil spring 4 having a high spring constant is used, the pressure release lever is manually moved in the direction from R1 to R2 in the figure to enable the pressure release when the envelope is passed. There is. Along with this operation, the pressure roller core metal 3
The position of 01 moves from P3 to P4, and the tip position of the entrance guide 7 is lowered by the action of the connecting rod 9 to secure the clearance of the entrance portion to the nip N when the envelope is passed and prevent the occurrence of image shift. The effect can be obtained.

Further, the mechanism shown in this embodiment can be applied to the film fixing device shown in FIG. 1 in the figure
Reference numeral 03 denotes a fixing film which is a heat conducting member in which the surface of a cylindrical polyimide resin is coated with PFA resin,
Reference numeral 104 is a film guide that supports the fixing film 103, 201 is a ceramic plate heater, 202 is a heating element formed by printing on the plate heater, and 501 is a temperature-sensing NTC characteristic disposed on the back surface of the plate heater 201. It is an element.

Since the fixing device shown in FIG. 6 uses a film having a small heat capacity as the heat conducting member, it has a feature that the time and energy for raising the temperature to the proper fixing temperature can be greatly saved. Further, regarding the recording material transportability, since the plate-shaped heater 201 is used, the nip N is formed in a substantially flat state and has high performance.

According to this structure, the pressure releasing mechanism ensures a good envelope transportability without wrinkling even when the envelope is passed, and the clearance of the nip entrance portion is obtained to prevent the occurrence of image shift. Can be prevented.

As described above, by providing the above-mentioned fixing device in the image forming apparatus, not only good image formation can be performed even when the speed of the image forming apparatus is increased, but also
Even when a thick paper such as an envelope is used in the image forming apparatus, good image formation can be performed without wrinkles and image shift.

(Fifth Embodiment) Next, a fifth embodiment of the present invention will be described with reference to FIG. The same parts as those of the first and fourth embodiments are designated by the same reference numerals and the description thereof will be omitted.

FIG. 7 is a drawing showing a fixing device in the fifth embodiment of the present invention, and this embodiment is also used in the image forming apparatus as shown in FIG. In FIG. 7, 7
Reference numeral 02 denotes an entrance guide having an anticorrosive coating on the surface of an iron bent sheet metal, which is a nip entrance guide, a nip entrance tip and a fulcrum S portion, and a pressure roller core metal 301.
The abutting part to the is integrated. Reference numeral 703 is a pressure spring for ensuring the contact of the inlet guide 702 with the pressure roller core 301, and 704 is an abutting member for restricting the movement of the inlet guide 702. That is, in this embodiment, the inlet guide and the movable member are integrally formed.

In this embodiment, the elastic layer 302 of the pressure roller 3 is used.
Asker-C hardness of 40 degrees is used, and it is characterized in that the width of the nip N greatly changes due to the hardness change. Further, the front end portion of the entrance guide 702 is set close to the fixing roller 1 in order to secure the transportability.

The feature of this embodiment is that, when the hardness of the pressure roller 3 is low, good recording material transportability can be obtained, and therefore, the abutting member 704 prevents the leading end portion of the inlet guide 702 from transporting. This is because the upper limit position is ensured to prevent problems such as damage when the fixing roller 1 is approached more than necessary. With this configuration, it is possible to prevent the occurrence of image misalignment by ensuring the good envelope transportability without wrinkling by the pressure release mechanism during the passage of the envelope and obtaining the clearance at the nip entrance. it can. As described above, by providing the above-mentioned fixing device in the image forming apparatus, not only good image formation can be performed even when the image forming apparatus is sped up, but the image forming apparatus uses thick paper such as an envelope. Even in this case, good image formation without wrinkles and image shifts can be performed.

(Sixth Embodiment) Next, a sixth embodiment of the present invention will be described with reference to FIG. The same parts as those of the first, fourth, and fifth embodiments are designated by the same reference numerals, and the description thereof will be omitted.

FIG. 8 is a drawing showing a fixing device in a sixth embodiment of the present invention, and this embodiment device is also used in the image forming apparatus as shown in FIG. In FIG. 8, reference numeral 705 denotes an integral type entrance guide, which is connected to the conveyance guide 1701 at a connection point V, as in the case described above.

The feature of the present embodiment is that a change in hardness of the pressure roller 3 and a change in transportability due to release of pressure when the envelope is passed through the sheet are reflected from the fixing device to the transport guide to make a large device layout change. .

With this configuration, it is possible to provide good recording material transportability even in an image forming apparatus compatible with large-sized paper.

[0077]

As described above, the first aspect of the present application
According to the invention, since the position of the inlet guide is changed depending on the position of the pressure roller so that the relative position between the inlet guide and the nip inlet portion is an appropriate position, a special recording material such as an ordinary recording material and an envelope is used. For both of them, it is possible to provide a fixing device that exhibits good transportability without paper wrinkles or trailing edge fluctuations even when the hardness or outer diameter of the pressure roller changes.

According to the second invention of the present application,
In addition to the effect of the first aspect of the present invention, it is possible to provide a fixing device having a high effect of preventing paper wrinkles by creating a difference in transport speed between the end portion and the central portion of the pressure roller.

Further, according to the third invention of the present application, in addition to the effect of the first or second invention, wrinkles are further prevented from being generated on a recording material such as an envelope, and the entrance guide is properly positioned. Thus, it is possible to provide a fixing device that does not cause image misalignment or jamming.

According to the fourth invention of the present application,
Since the position of the inlet guide is changed according to the position of the pressure roller in the fixing device to set the relative position between the inlet guide and the nip inlet to an appropriate position, it can be applied to both ordinary recording materials and special recording materials such as envelopes. On the other hand, even when the hardness and outer diameter of the pressure roller are changed, it is possible to provide an image forming apparatus capable of performing good image formation by exhibiting good transportability without paper wrinkles and trailing edge bounce. Will be possible.

Further, according to the fifth invention of the present application, in addition to the effect of the fourth invention, a paper wrinkle is caused by further producing a difference in transport speed between the end portion and the central portion of the pressure roller in the fixing device. It is possible to provide an image forming apparatus capable of enhancing the prevention effect against the above and performing more favorable image formation.

According to the sixth invention of the present application,
In addition to the effects of the fourth or fifth aspect of the invention, it is possible to prevent generation of wrinkles on a recording material such as an envelope, and set an entrance guide at an appropriate position to form a good image without causing image shift or jam. It is possible to provide an image forming apparatus that can do this.

[Brief description of drawings]

FIG. 1 is a diagram illustrating a fixing device according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating an image forming apparatus according to a first embodiment of the present invention.

FIG. 3 is a diagram illustrating a fixing device according to a second exemplary embodiment of the present invention.

FIG. 4 illustrates a fixing device according to a third exemplary embodiment of the present invention.

FIG. 5 illustrates a fixing device according to a fourth exemplary embodiment of the present invention.

FIG. 6 is a diagram showing another fixing device according to the fourth exemplary embodiment of the present invention.

FIG. 7 illustrates a fixing device according to a fifth exemplary embodiment of the present invention.

FIG. 8 illustrates a fixing device according to a sixth exemplary embodiment of the present invention.

FIG. 9 is a diagram showing a conventional image forming apparatus.

FIG. 10 is a diagram showing a conventional fixing device.

[Explanation of symbols]

 1 Fixing Roller 2 Halogen Heater (Heating Body) 3 Pressure Roller 7,702 Entrance Guide 9,902 Connecting Rod (Movable Member) 21 Scanner (Exposure Means) 22 Charger (Charging Means) 23 Photosensitive Drum (Image Bearing Body) 24 Developing device 25 Paper feeding device (recording material supplying means) 26 Transfer device 29 Fixing device 103 Fixing film 202 Heating element 302 Rubber layer (elastic layer) 303 Release layer (elastic layer) 402 Pressure release lever (pressurizing force adjusting mechanism) 403 Insertion bar (pressurizing force adjustment mechanism) 901 Roller (movable member) N Nip (press contact part) P Paper (recording material)

Claims (6)

[Claims] 1. A fixing roller containing a heating element or a fixing film slidingly contacting the heating element, and biased so as to directly contact the fixing roller directly or indirectly via the fixing film. A pressure roller having an elastic layer and an inlet guide for guiding the recording material to the pressure contact portion, and by heating and pressing the recording material on which the unfixed image is formed while being nipped and conveyed. In the fixing device for fixing an unfixed image on the recording material, the entrance guide is arranged so that the guide surface is rotatable about a central axis substantially parallel to the rotation center of the pressure roller. It is characterized in that it is connected to a movable member rotatable around a central axis substantially parallel to the rotational center of the pressure roller, following changes in position of the rotational center of the pressure roller in the urging direction and the anti-urging direction. Fixing device. 2. The fixing device according to claim 1, wherein the outer diameter of the axial center portion of the pressure roller is smaller than the outer diameter of the axial end portion. 3. The fixing device according to claim 1, further comprising a pressing force adjusting mechanism for the fixing roller of the pressure roller or the heating element. 4. An image carrier having a photosensitive layer, charging means for charging the image carrier, exposing means for exposing the charged image carrier, and electrostatic formed on the image carrier. A developing device for developing a latent image with a developer, a recording material supplying means for supplying a recording material, a transfer device for transferring an unfixed image formed on the image carrier onto the recording material, and a heating element. A pressure roller having an elastic layer that is urged so as to be in direct pressure contact with the fixing roller included therein or indirectly through the fixing film, and an inlet guide for guiding a recording material to the pressure contact portion. And a fixing device in which the unfixed image is transferred, and the recording material on which the unfixed image is transferred is heated and pressed while being nipped and conveyed at the pressure contact portion of the fixing device to fix the unfixed image on the recording material. In an image forming apparatus that forms an image by The inlet guide of the apparatus is arranged so that the guide surface is rotatable about a central axis substantially parallel to the rotation center of the pressure roller, and the urging direction and the anti-urging direction of the rotation center of the pressure roller are arranged. The image forming apparatus is connected to a movable member that is rotatable around a central axis that is substantially parallel to the rotation center, following a change in position of the image forming apparatus. 5. The image forming apparatus according to claim 4, wherein the outer diameter of the central portion of the pressure roller in the axial direction is smaller than the outer diameter of the end portion in the axial direction. 6. The image forming apparatus according to claim 4, further comprising a pressing force adjusting mechanism for the fixing roller of the pressure roller or the heating element.