JP4353678B2 - Image forming apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention includes a fixing member to be heated and a pressure member that is in pressure contact with the fixing member, and a recording material carrying a toner image to be fixed is oriented so that the toner image is in contact with the fixing member. The present invention relates to an image forming apparatus having a fixing device that passes through a nip formed by pressure contact between the fixing member and a pressure member and fixes the toner image onto a recording material by the action of heat and pressure.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, it is well known to employ a fixing device of the above type in an image forming apparatus configured as a copying machine, a printer, a facsimile, or a multifunction machine having at least two of these functions. In this type of fixing device, when the toner carried on the recording material passes through the nip formed by the fixing member and the pressure member, the toner melts in the nip. There is a possibility that the recording material that has come out is wound around the surface of the fixing member without being separated. In particular, in an image forming apparatus that forms a full-color image, a plurality of toner images of different colors are formed on a recording material by superimposition, and the superimposed toner images are fixed by a fixing device. This melts the toner, which increases the adhesive strength of the toner and makes it easier to wind the recording material around the fixing member.
[0003]
Therefore, conventionally, a separating means comprising a plurality of separating claws is brought into contact with the surface of the fixing member, and the recording material exiting the nip is separated from the fixing member surface by the separating claws, and the recording material is wound around the surface of the fixing member. This is configured to prevent this. However, since the tip of the separation claw is in contact with the surface of the fixing member, the surface of the fixing member may be damaged by the separation claw. When the surface of the fixing member is damaged, a mark corresponding to the damage is formed on the toner image passing through the nip, and the image quality of the toner image after fixing is deteriorated.
[0004]
In order to eliminate such drawbacks, a fixing device has been proposed in which the separation claw is arranged apart from the surface of the fixing member. However, if the separation claw is arranged in a non-contact state with respect to the surface of the fixing member, the recording material exiting the nip enters between the fixing member and the separation claw while adhering to the surface of the fixing member, and the recording material is fixed. There is a risk of wrapping around the member. If the separation claw separated from the fixing member is used in this way, the recording material separating function is lowered, and the possibility that the recording material is wound around the fixing member is increased.
[0005]
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to effectively fix a recording material around a fixing member and to effectively suppress a problem that the image quality of a toner image after fixing is deteriorated. Is to provide an image forming apparatus.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, according to the present invention, in the image forming apparatus of the type described at the beginning, when only the margin portion on the leading end side in the conveyance direction of the recording material to be conveyed exits the nip, the margin portion on the leading end side Is configured to face the pressure member side with respect to a linear extension line connecting the downstream end of the nip in the recording material conveyance direction and the upstream end of the nip in the recording material conveyance direction, and the recording material exiting the nip A sheet-like separation member for separating the sheet from the surface of the fixing member in a non-contact state with respect to the surface of the fixing member, and a downstream end of the nip in the recording material conveyance direction and a tip of the separation member Is set to be smaller than the width in the conveyance direction of the blank portion on the leading end side in the conveyance direction of the recording material, and the separation member has an opening penetrating in the thickness direction. An image forming apparatus characterized by To draft (claim 1).
[0007]
In order to achieve the above object, according to the present invention, in the image forming apparatus of the type described at the beginning, a sheet-like separating member for separating the recording material that has exited the nip from the surface of the fixing member is provided. The fixing member is disposed in a non-contact state with respect to the surface of the fixing member, and the Asker C hardness of the surface of the pressure member in the nip is set higher than the Asker C hardness of the surface of the fixing member in the nip. The gap between the downstream end in the transport direction and the leading end of the separation member is set to be smaller than the width in the transport direction of the blank portion on the leading end side of the recording material in the transport direction. An image forming apparatus is proposed in which an opening penetrating in a direction is formed (claim 2).
[0008]
The image forming apparatus according to claim 1 or 2, wherein the fixing member is an endless fixing belt wound around a guide member, and the pressure member is interposed between the fixing belt and the fixing member. It is advantageous that the Asker C hardness of the surface of the pressure member pressed against the guide member is set higher than the Asker C hardness of the surface of the fixing belt wound around the guide member. .
[0009]
In order to achieve the above object, according to the present invention, in the image forming apparatus of the type described at the beginning, a sheet-like separating member for separating the recording material that has exited the nip from the surface of the fixing member is provided. A pressure member that is arranged in a non-contact state with respect to the surface of the fixing member and has a convex shape in the nip elastically deforms the fixing member into a concave shape, and has a downstream end in the recording material conveyance direction of the nip. The gap between the leading end of the separating member is set to be smaller than the width in the conveying direction of the blank portion on the leading end side in the conveying direction of the recording material, and the separating member penetrates in the thickness direction. An image forming apparatus having an opening is proposed.
[0010]
5. The image forming apparatus according to claim 4, further comprising: a pressure member side separating unit for separating the recording material that has exited the nip from the surface of the pressure member. It is advantageous if the tip is brought into contact with the surface of the pressure member (claim 5).
[0011]
6. The image forming apparatus according to claim 1, wherein a gap holding member is provided at each end of the separating member in a direction orthogonal to the recording material conveyance direction, and the gap holding member is It is advantageous that the space between the front end of the separating member and the surface of the fixing member is maintained in contact with the recording material non-passing area of the fixing member.
[0012]
Furthermore, in the image forming apparatus according to any one of claims 1 to 6, it is advantageous to provide a tension applying means for pulling the separating member in a direction orthogonal to the recording material conveyance direction (claim 7). .
[0013]
Furthermore, in the image forming apparatus according to any one of claims 1 to 7, it is advantageous that the toner image is formed by a toner containing at least a resin, a colorant, and a wax (claim 8).
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below in detail with reference to the drawings.
[0015]
FIG. 1 is a vertical sectional view showing an outline of an image forming apparatus. In the image forming apparatus main body 1, an image forming means 2 for forming a toner image on a recording material and a recording material are fed to the image forming means. And a fixing device 4 for fixing the toner image formed on the recording material. In FIG. 1, the fixing device 4 is shown as a simple block, and a specific configuration example will be described later. Here, first, the outline of the image forming means 2 will be clarified.
[0016]
The image forming means 2 exemplified here has a drum-shaped photoconductor 5 which is an example of an image carrier, and when the photoconductor 5 rotates in the clockwise direction, the surface of the photoconductor has a predetermined polarity by the charging device 6. Is charged. The charged surface is irradiated with a light-modulated laser beam L emitted from a laser writing unit 7 which is an example of an exposure apparatus, whereby an electrostatic latent image is formed on the surface of the photoreceptor. The electrostatic latent image is visualized as a toner image by the developing device 8, and the toner image is transferred onto the recording material fed from the feeding unit 3 by the action of the transfer device 9. The residual transfer toner adhering to the surface of the photoconductor after the toner image is transferred is removed by the cleaning device 10.
[0017]
The feeding unit 3 includes a cassette 11 that stores a recording material P made of, for example, transfer paper or a resin sheet, and the uppermost recording material P is fed out of the cassette 11 by the rotation of the feeding roller 12. The fed recording material is fed to the transfer portion between the photoconductor 5 and the transfer device 9 by the rotation of the registration roller pair 13, and the toner image on the photoconductor 5 is transferred to the recording material as described above. Transcribed above. The recording material carrying the toner image in this way is sent to the fixing device 4 as shown by an arrow A and passes through the fixing device 4, and at this time, the toner image on the recording material is fixed as will be described later. . The recording material that has passed through the fixing device 4 is discharged onto a tray 14 outside the apparatus.
[0018]
FIG. 2 is an enlarged cross-sectional view showing an example of the fixing device 4. The fixing device 4 shown here is configured as a fixing member configured as a fixing roller 15 and a pressure roller 16 pressed against the fixing roller 15. The nip N is formed when the rollers 15 and 16 are pressed against each other. The fixing roller 15 and the pressure roller 16 are formed in a columnar shape having a circular outer cross section. In the illustrated example, these rollers 15 and 16 are formed in a hollow cylindrical shape, the fixing roller 15 rotates in the clockwise direction, and the pressure roller 16 rotates in the counterclockwise direction.
[0019]
The nip N formed by the pressure contact between the rollers 15 and 16 is controlled to an appropriate temperature suitable for fixing the toner image by the heating means. In this example, halogen heaters 17 and 18 as heat sources are provided inside the fixing roller 15 and the pressure roller 16, respectively, and ON / OFF of energization to the heaters 17 and 18 is controlled by a temperature control means (not shown). Thus, the temperature of the nip N is maintained at an appropriate temperature.
[0020]
The recording material P carrying the unfixed toner image T is fed into the fixing device 4 as indicated by an arrow A, and the recording material P is placed in the nip N so that the toner image T is in contact with the surface of the fixing roller 15. The toner image T is fixed on the recording material P by heat and pressure.
[0021]
As described above, the fixing device includes a fixing member that rotates while being heated, and a pressure member that rotates while being pressed against the fixing member. The toner image is fixed to the recording material by the action of heat and pressure through a nip formed by pressure contact between the fixing member and the pressure member in a direction in contact with the fixing member. Such a basic configuration does not change in the fixing devices of the examples described later. As described above, in the example shown in FIG. 2, the fixing member is constituted by the fixing roller 15 that rotates, and the pressure member is constituted by the pressure roller 16 that rotates while being pressed against the fixing roller 15. As will be described later, the fixing member is composed of an endless fixing belt that is wound around a guide member and rotates, and the pressure member is composed of an endless pressure belt that is wound around the guide member and rotates. You can also. Thus, the fixing member and the pressure member can be configured in various forms.
[0022]
Here, in the fixing device 4 shown in FIG. 2, when the toner image T carried on the recording material P passes through the nip N between the fixing roller 15 and the pressure roller 16, the toner melts in the nip N. To do. In order to prevent the recording material P coming out of the nip N from being wound around the surface of the fixing roller 15 by the adhesive force of the toner at this time, the following configuration is adopted.
[0023]
FIG. 3 is an enlarged explanatory view of the nip N formed by the fixing roller 15 and the pressure roller 16 and the recording material P passing through the nip N. As shown in FIGS. 2 and 3, in the vicinity of the exit of the nip N, the fixing member side separating means 19 for separating the recording material P that has exited the nip N from the surface of the fixing member (the fixing roller 15 in this example). Is disposed in a non-contact state with respect to the surface of the fixing member. The fixing member side separation means can be configured in an appropriate form, but the fixing member side separation means 19 shown here is constituted by a sheet-like separation member 20.
[0024]
On the other hand, on the recording material P, a toner image is formed in the image area indicated by hatching in FIG. 4 and indicated by reference numeral IA, and no toner image is formed in the outer edge area of the image area IA. It is a margin part M. The recording material P is transported in the direction indicated by the arrow A and enters the fixing device 4, and the width of the blank portion M <b> 1 on the leading end side in the transport direction in the transport direction A is W. This width W is, for example, about 2 to 5 mm. 2 and 3 show a state where only the margin M1 on the tip end side has just come out of the nip N. FIG. The same applies to FIGS. 5 to 10.
[0025]
Here, as shown in FIG. 3, if the gap between the outlet end of the nip N, that is, the downstream end NE of the nip N in the recording material conveyance direction, and the leading end of the separating member 20 facing the fixing member is G. The gap G is set to be smaller than the aforementioned width W in the conveyance direction A of the margin M1 on the leading end side in the conveyance direction of the recording material P (G <W). Accordingly, as shown in FIGS. 2 and 3, when only the entire margin M1 on the leading end side of the recording material P comes out of the nip N, the leading end of the fixing member side separating means 19 is fixed to the margin M1. It is located in a state of entering a space area between the rollers 15.
[0026]
On the other hand, the Asker C hardness of the surface of the pressure roller 16 is set to be higher than the Asker C hardness of the surface of the fixing roller 15. Preferably, the Asker C hardness of the surface of the pressure roller 16 is It is configured to be 20 to 40 Hs larger than the Asker C hardness of the surface. Thus, the Asker C hardness of the surface of the pressure member (in this example, the pressure roller 16) in the nip N is set higher than the Asker C hardness of the surface of the fixing member (in this example, the fixing roller 15) in the nip N. As a result, as shown in FIGS. 2 and 3, the pressure roller 16 compresses and deforms the surface of the fixing roller 15 so as to bite into the fixing roller 15 side. In the nip N, the pressing member having a convex shape elastically deforms the fixing member into a concave shape.
[0027]
Therefore, as shown in FIGS. 2 and 3, when only the margin M1 on the leading end side of the recording material P comes out of the nip N, the margin M1 is in a posture along the peripheral surface of the pressure roller 16, that is, The posture of the fixing roller 15 is greatly separated from the peripheral surface. Since no toner image is formed on the leading edge margin M1, the margin M1 does not attempt to adhere to the surface of the fixing roller 15 due to the adhesive force of the toner. The ink is discharged from the nip N so as to be along the peripheral surface of the pressure roller 16 biting into the side. At this time, the margin M1 and the surface of the fixing roller 15 are separated from each other by a large distance, and the margin M1 of the recording material P does not wrap around the surface of the fixing roller 15 in this state. If a straight line connecting the downstream end NE of the nip N in the recording material conveyance direction and the upstream end NS of the nip N in the recording material conveyance direction is LA, only the margin M1 on the leading end side in the conveyance direction of the recording material P to be conveyed is present. When leaving the nip N, the margin M1 on the leading end side is directed toward the pressing member (in this example, the pressing roller 16) with respect to the extension line LAA drawn on the recording material conveyance direction side of the straight line LA. It is composed.
[0028]
When the recording material P is further conveyed in the direction of arrow A than in the state shown in FIGS. 2 and 3, the image area IA shown in FIG. Then, the recording material P adheres to or tends to adhere to the surface of the fixing roller 15 due to the adhesive force of the toner on the image area IA, so that the recording material P is pulled toward the fixing roller 15. This tendency is remarkable in the case of a recording material that is weak, such as thin paper.
[0029]
However, since the fixing member side separating means 19 is provided in the vicinity of the fixing roller 15, the recording material P hits the fixing member side separating means 19 and is guided by the separating means 19 as indicated by a chain line in FIG. The recording material P is prevented from being wound around the surface of the fixing roller 15. Although the fixing member side separating means 19 is disposed away from the surface of the fixing roller 15, the gap G is set to be smaller than the width W of the margin portion M1, so that the fixing roller 15 is separated by the adhesive force of the toner. The recording material P pulled to the side is prevented from being wound around the surface of the fixing roller 15 through the gap G while adhering to the surface of the fixing roller 15. The recording material P that has exited the nip N is conveyed while being guided by the fixing member side separating means 19 positioned on the upper side and the guide member 21 positioned on the lower side.
[0030]
As described above, the recording material P that has exited the nip N can be prevented from being wound around the surface of the fixing roller 15, and the fixing member side separation means 19 is not in contact with the surface of the fixing roller 15. Therefore, it is possible to prevent a problem that the surface of the fixing roller 15 that is easily damaged is damaged by the fixing member side separating means 19.
[0031]
The image forming apparatus shown in FIG. 1 is configured to form a monochromatic, usually black, toner image on the recording material P. However, in an image forming apparatus that forms a color image, For example, since a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are formed in an overlapping manner and the overlapping toner image is fixed by a fixing device, the recording material has been particularly easy to wrap around a fixing member. Also in the case of an image forming apparatus that forms an image, by employing the above-described configuration, it is possible to prevent the recording material from being wound around the fixing member while preventing the fixing member from being damaged.
[0032]
Here, a more specific configuration example of the fixing device 4 shown in FIG. 2 will be described.
[0033]
The fixing roller 15 includes a cored bar 23 and an elastic layer 24 laminated on the outer peripheral surface thereof. A release layer 25 is laminated on the outer peripheral surface of the elastic layer 24. The outer diameter of the fixing roller 15 is, for example, 40 mm. It is. The core metal 23 is constituted by an iron hollow roller having an outer diameter of 34 mm and a wall thickness of 1 mm, for example, the elastic layer 24 is formed by silicone rubber having a thickness of 3 mm, for example, and the release layer 25 has a thickness of 10 μm to 30 μm, for example. The PFA tube. By providing the release layer 25, it is possible to suppress the recording material P from adhering to the surface of the fixing roller due to the adhesive force of the toner.
[0034]
The pressure roller 16 includes, for example, a cored bar 26 made of an iron hollow roller having an outer diameter of 38 mm and a wall thickness of 1 mm, an elastic layer 27 stacked on the outer peripheral surface, and a release layer 28 stacked on the outer peripheral surface. The elastic layer 27 is made of, for example, silicone rubber having a layer thickness of 1 mm, and the release layer 28 is formed of, for example, a PFA tube having a layer thickness of 10 μm to 30 μm.
[0035]
The surface hardness of the fixing roller 15 is set to, for example, 45 Hs in terms of Asker C hardness, and the surface hardness of the pressure roller 16 is also set to, for example, 80 Hs in terms of Asker C hardness. Since the pressure roller 16 is harder in this way, the fixing roller 15 is elastically deformed in a state where the pressure roller 16 bites into the surface of the fixing roller 15, and the nip N is formed along the outer shape of the pressure roller 16. Formed.
[0036]
In the fixing device 4 shown in FIG. 5, the fixing member is composed of an endless fixing belt 15A. The fixing belt 15A is wound around a guide member composed of two guide rollers 15B and 15C. The number of guide members may be 3 or more. On the other hand, the pressure member is constituted by a cylindrical pressure roller 16 as in the fixing device shown in FIG. 2, and the pressure roller 16 and the guide rollers 15B and 15C are crossed with a circular outer periphery. It is formed in a cylindrical shape having a surface shape. In the example shown in FIG. 5, all the rollers 15B, 15C, and 16 are formed in a hollow cylindrical shape.
[0037]
The pressure roller 16 is in pressure contact with one guide roller 15B via the fixing belt 15A, whereby the outer peripheral surface of the pressure roller 16 is in pressure contact with the outer peripheral surface of the fixing belt 15A, and a nip N is formed by the pressure contact. Is done. The guide rollers 15B and 15C and the pressure roller 16 rotate in the direction of the arrow, respectively, whereby the fixing belt 15A is rotationally driven in the direction of the arrow B. When the endless fixing belt 15A rotates in this way, the guide rollers 15B and 15C serve to guide the fixing belt 15A, and the one guide roller 15B facing the pressure roller 16 is a pressure roller. The other guide roller 15C serves as a tension roller that applies tension to the fixing belt 15A. As will be described later, a guide member other than the guide roller may be used, the fixing belt 15A may be wound around the guide member, and the pressure roller 16 may be pressed against a plurality of guide members via the fixing belt 15A. . The fixing member is constituted by an endless fixing belt that is wound around a plurality of guide members and rotates, and the pressure member is pressed by at least one guide member via the fixing belt and rotated by a pressure roller that rotates. Make up.
[0038]
Focusing on the above-described functions of both guide rollers 15B and 15C, in the following description, one guide roller 15B will be referred to as a counter roller and the other guide roller 15C will be referred to as a tension roller as necessary.
[0039]
In the fixing device shown in FIG. 5, heaters 17A and 18 are provided inside the tension roller 15C and the pressure roller 16, and the fixing belt 15A and the pressure roller 16 are heated by the heaters 17A and 18, The energization of the heaters 17A and 18 is controlled ON and OFF, and the temperature of the nip N is maintained at an appropriate temperature suitable for fixing the toner image.
[0040]
Also in this example, as shown by the arrow A, the recording material P carrying the toner image T to be fixed passes through the nip N in the direction in which the toner image T contacts the surface of the fixing belt 15A, and heat and The toner image T is fixed on the recording material P by the action of pressure.
[0041]
Also in the fixing device 4 shown in FIG. 5, the Asker C hardness of the surface of the pressure member formed of the pressure roller 16 is the surface of the fixing belt portion wound around the guide member (opposing roller 15B in the illustrated example). It is set higher than the measured Asker C hardness. Thus, the fixing device 4 shown in FIG. 5 also sets the Asker C hardness of the surface of the pressure roller 16 at the nip N higher than the Asker C hardness of the surface of the fixing belt 15A at the nip N. As in the case of the fixing device shown in FIG. 5, when only the margin M1 on the leading end side in the conveyance direction of the recording material to be conveyed exits the nip N, the margin M1 on the leading end side is downstream of the nip N in the recording material conveyance direction. The straight line LA connecting the side end NE and the upstream end NS of the nip N in the recording material conveyance direction faces the side of the pressure member (the pressure roller 16 in the illustrated example) toward the recording material conveyance direction side. . Moreover, a fixing member side separating means 19 for separating the recording material P that has exited the nip N from the surface of the fixing member made of the fixing belt 15A is disposed in a non-contact state with respect to the surface of the fixing member. A gap G between the recording material conveyance direction downstream end NE and the leading end of the fixing member side separating unit 19 facing the fixing member is a margin portion M1 on the leading end side of the recording material P in the conveyance direction in the conveyance direction. It is set smaller than the width W.
[0042]
With the above-described configuration, the recording material P is prevented from being wound around the fixing member made of the fixing belt 15A, just like the fixing device shown in FIGS. Can be prevented from being damaged, the image quality of the toner image after fixing can be improved, and the life of the fixing belt 15A can be extended. The recording material P that has exited the nip N is guided and conveyed by the fixing member-side separating means 19 and the guide member 21, and is discharged to the tray 14 (FIG. 1) as well as the fixing device shown in FIGS. There is no change.
[0043]
A more specific configuration example of the fixing device 4 shown in FIG. 5 will be described. The opposing roller 15B and the pressure roller 16 can be configured in the same manner as the fixing roller 15 and the pressure roller 16 of the fixing device shown in FIG. . For example, the fixing belt 15A is formed by laminating a silicone rubber having an Asker C hardness of 30Hs with a thickness of 0.2mm on a polyimide resin substrate having a thickness of 50μm, and coating PFA with a thickness of 5μm as a release layer thereon. Things can be used. Further, the nip N shown in FIG. 5 is opposed to the first nip portion where only the fixing belt 15A comes into contact with the pressure roller 16 at a portion where the pressure roller 16 does not face the opposite roller 15B, and the pressure roller 16 faces through the fixing belt 15A. The second nip portion is in contact with the roller 15B. Thereby, a wide nip N can be formed in the circumferential direction of the fixing belt 15A, the pressure contact force between the pressure roller 16 and the fixing belt 15A can be made relatively small, and the proper temperature of the nip N can be lowered.
[0044]
In the fixing device shown in FIG. 2, since the fixing roller 15 is heated by the heater 17 from the inside of the rubber-like elastic layer 24 having poor thermal conductivity, the fixing roller 15 is in contact with the toner when the fixing device is started up. Although a long time is required until the temperature rises to a temperature suitable for image fixing, the fixing device shown in FIG. 5 uses the fixing belt 15A having a small thickness and a small heat capacity as a fixing member. The belt 15A is not heated from the inside of the counter roller 15B, but is heated by the heater 17A in the thin tension roller 15C, so that the fixing belt 15A rises to a temperature suitable for fixing the toner image. Can be shortened.
[0045]
In the fixing device shown in FIGS. 2 and 5, when only the front end side margin M1 of the recording material P exits the nip N, the margin M1 is directed to the pressure member side with respect to the extension line LAA. Therefore, the surface hardness of the fixing member constituted by the fixing roller 15 or the fixing belt 15A and the surface hardness of the pressure member made of the pressure roller 16 are set as described above. In the case of 15A, as described above, the hardness of the surface of the fixing member is the hardness measured on the surface of the fixing belt portion wound around the opposing roller 15B. In short, regardless of the form of the fixing member, the Asker C hardness of the surface of the pressure member at the downstream end NE in the recording material conveyance direction of the nip N is fixed at the downstream end NE of the nip N in the recording material conveyance direction. By setting higher than the Asker C hardness of the surface of the member, when only the front end side margin portion M1 exits the nip N, the margin portion M1 is configured to face the pressing member side with respect to the extension line LAA. be able to.
[0046]
6 and 7 show other examples of the fixing device 4. The basic configuration of the fixing device 4 shown here is substantially the same as that of the fixing device shown in FIG. 6 corresponding to the parts of the fixing device 4 shown in FIG. 2 are denoted by the same reference numerals as those in FIG. 2, and the description of the basic configuration and operation thereof is omitted.
[0047]
The fixing device 4 shown in FIGS. 6 and 7 differs from the fixing device shown in FIG. 2 in that the Asker C hardness of the surface of the fixing member made of the fixing roller 15 and the surface of the pressure member made of the pressure roller 16. The Asker C hardness is set to be approximately equal. By setting the surface hardness of the fixing roller 15 and the pressure roller 16 in this way, both the rollers 15 and 16 are compressed and deformed into a substantially flat shape at the nip N formed by the fixing roller 15 and the pressure roller 16. A linear nip N is formed. Accordingly, as shown in FIG. 7, when only the margin M1 on the leading end side in the conveyance direction of the recording material P to be conveyed exits the nip N, the margin M1 on the leading end is downstream of the nip N in the recording material conveyance direction. The straight line LB connecting the side end NE and the upstream end NS of the nip N in the recording material conveyance direction is almost directed to the direction of the extended line LBB toward the recording material conveyance direction. The fixing device 4 shown in FIGS. 6 and 7 also includes a fixing member side separating means 19 for separating the recording material P that has exited the nip N from the surface of the fixing member made of the fixing roller 15. A gap G between the downstream end NE of the nip N in the recording material conveyance direction and the front end of the fixing member side separating means 19 facing the fixing member is arranged in a non-contact state with respect to the surface of the recording material. The margin M1 on the front end side in the transport direction of P is set smaller than the width W in the transport direction.
[0048]
As shown in FIGS. 6 and 7, when only the leading edge side margin portion M1 of the recording material P exits the nip N, no toner image is formed in the margin portion M1, so that the margin portion M1 is the toner. The margin M1 is discharged from the nip N along the extension line LBB of the nip N without adhering to the surface of the fixing roller 15 due to the adhesive force, and in this state, the margin M1 of the recording material P is removed from the fixing roller 15. There is no wrapping around the surface. When the recording material P is further conveyed in the direction of the arrow A than the state shown in FIGS. 6 and 7, the image area IA shown in FIG. 4 starts to be discharged from the nip N, and the sticking of the toner on the image area IA Since the recording material P adheres to or tends to adhere to the surface of the fixing roller 15 due to the force, the recording material P is pulled toward the fixing roller 15, but in the vicinity of the fixing roller 15, the fixing member side separating means 19. Therefore, the recording material P hits the fixing member side separating means 19 and is guided by the separating means 19, and the recording material P is prevented from being wound around the surface of the fixing roller 15. Also in this case, the fixing member side separating means 19 is the fixing roller 15.
However, since the gap G is set to be smaller than the width W of the margin M1, the recording material P pulled toward the fixing roller 15 by the adhesive force of the toner is Wrapping around the surface of the fixing roller 15 through the gap G while being attached to the surface of the fixing roller 15 is prevented. The recording material P that has passed through the fixing device 4 is discharged onto the tray 14 shown in FIG.
[0049]
As described above, in the fixing device 4 shown in FIGS. 6 and 7 as well, the recording material P that has exited the nip N can be prevented from being wound around the surface of the fixing roller 15, and the fixing member side separation means 19 can be fixed. Since it is not in contact with the surface of the roller 15, it is possible to prevent the fixing member 15 from being damaged by the fixing member side separating means 19 on the surface of the fixing roller 15 which has a low hardness and is easily damaged. In addition, since the nip N has a flat shape, the recording material that has exited the nip is less likely to curl than when the nip N is curved as in the example shown in FIGS. can get.
[0050]
The fixing roller 15 and the pressure roller 16 of the fixing device 4 illustrated in FIG. 6 can be configured similarly to the fixing roller 16 of the fixing device 4 illustrated in FIG. 2, for example. Further, the surface hardness of the fixing roller 15 and the pressure roller 16 shown in FIG. As described above, since the surfaces of the rollers 15 and 16 have substantially the same hardness, the nip N is formed in a substantially flat shape.
[0051]
FIG. 8 shows still another example of the fixing device 4. The basic configuration of the fixing device 4 shown here is substantially the same as that of the fixing device shown in FIG. While the tension roller 15C shown in FIG. 5 is located on the right side of the opposing roller 15B, the tension roller 15C shown in FIG. 8 is located above the opposing roller 15B. It ’s not a difference. Therefore, each part of the fixing device shown in FIG. 8 corresponding to each part of the fixing device shown in FIG. 5 is denoted by the same reference numeral as that in FIG.
[0052]
The fixing device shown in FIG. 8 is different from the fixing device shown in FIG. 5 in that the Asker C hardness measured on the surface of the portion of the fixing belt 15A wound around the opposing roller 15B is an example of the pressure member. This is the point that the surface of the pressure roller 16 is almost the same as the Asker C hardness. Therefore, also in the fixing device 4 shown in FIG. 8, only the margin M1 on the leading end side in the transport direction of the recording material P to be transported exits the nip N as in the case of the fixing device shown in FIGS. At that time, the margin M1 on the leading end side is an extension line LBB of the straight line LB connecting the downstream end NE of the nip N in the recording material conveyance direction and the upstream end NS of the nip N to the recording material conveyance direction. The direction is almost facing. In addition, a fixing member side separating means 19 for separating the recording material P that has exited the nip N from the surface of the fixing member made of the fixing belt 15A is disposed in a non-contact state with respect to the surface of the fixing member. The gap G between the recording material conveyance direction downstream end NE and the leading end of the fixing member side separating unit 19 facing the fixing member is a conveyance direction of the margin M1 on the leading side of the recording material P in the conveyance direction. Is set to be smaller than the width W. Accordingly, like the fixing device shown in FIGS. 6 and 7, the recording material P can be prevented from being wound around the surface of the fixing belt 15A, and the surface of the fixing belt 15A is scratched by the fixing member side separating means 19. Can be prevented, and further, the problem that the recording material P that has exited the nip N tends to curl can be prevented.
[0053]
In the fixing device shown in FIG. 6 to FIG. 8, when only the leading edge side margin M1 of the recording material P exits the nip N, the margin M1 is directed substantially in the direction of the extension line LBB. The surface hardness of the fixing member constituted by the fixing roller 15 or the fixing belt 15A and the surface hardness of the pressure member composed of the pressure roller 16 are set to be substantially equal as described above. In this case, the fixing member is also the fixing belt. In the case of 15A, the hardness of the surface of the fixing member is a hardness measured on the surface of the fixing belt portion wound around the opposing roller 15B. In short, regardless of the form of the fixing member, the Asker C hardness of the surface of the fixing member at the downstream end NE in the recording material conveyance direction of the nip N and the pressurization at the downstream end NE of the nip N in the recording material conveyance direction. By setting the Asker C hardness of the surface of the member to be substantially equal, when only the front end side margin portion M1 exits the nip N, the margin portion M1 may be configured to substantially face the direction of the extension line LBB. it can.
[0054]
Incidentally, the image forming apparatus shown in FIG. 1 is configured to form a toner image only on one surface of the recording material P, but the toner image on the photosensitive member is transferred to one surface of the recording material. Then, after fixing the toner image by the fixing device, the recording material is reversed and fed back to the photosensitive member, and the toner image on the photosensitive member is transferred to the other surface of the recording material. An image forming apparatus for fixing an image by a fixing device is also well known. When it is necessary to distinguish between the toner image formed on one surface of the recording material and the toner image formed on the other surface of the recording material, the former is the first toner image and the latter is the second toner image. I will call it.
[0055]
When fixing the second toner image by passing the recording material through the nip of the fixing device, the first toner image already fixed on one surface of the recording material also passes through the nip, and the first toner image is pressurized. Contact the member. At this time, since the pressure member is also heated, the first toner image is melted by the heat, and there is a possibility that the recording material exiting the nip is wound around the surface of the pressure member.
[0056]
Therefore, in the fixing device 4 shown in FIGS. 2 and 5, the pressure member side separation for separating the recording material P that has exited the nip N from the surface of the pressure member (the pressure roller 16 in the illustrated example). Means 22 is provided, and the tip of the separating means 22 facing the pressure member is in contact with the surface of the pressure member. The pressure member side separating means 22 is constituted by, for example, a plurality of separation claws arranged in the axial direction of the pressure roller 16, or one sheet-like separation member.
[0057]
As shown in FIGS. 2 and 5, the first toner image TA already fixed on one surface of the recording material P entering the nip N is carried and fixed on the other surface of the recording material P by the fixing device 4. When the second toner image T to be carried is carried, when the recording material P passes through the nip N, the first toner image TA is also heated and melted. May wrap around the surface of the pressure roller 16. In this case, the recording material P is separated from the surface of the pressure roller 16 by the pressure member-side separating means 22 in contact with the surface of the pressure roller 16. To be separated.
[0058]
Since the pressure member side separating means 22 is in contact with the surface of the pressure member made up of the pressure roller 16 at its tip, the recording material to be wound around the surface of the pressure roller 16 is surely placed on the surface. Can be separated from At that time, as described above, the surface hardness of the pressure roller 16 is higher than the surface hardness of the fixing roller 15, and the surface of the pressure roller 16 is not easily scratched. The problem that the surface of the pressure roller 16 is damaged by the separating means 22 can be prevented.
[0059]
In the fixing device shown in FIGS. 6 to 8, as described above, when only the front end side margin M1 of the recording material P being conveyed exits the nip N, the front end side margin M1 is extended. In addition, the pressure member side separation means 19A for separating the recording material P that has exited the nip N from the surface of the pressure member made of the pressure roller 16 is configured so as to be substantially directed in the direction of the line LBB. Is arranged in a non-contact state with respect to the surface of the pressure member, and is formed between the downstream end NE of the nip N in the recording material conveyance direction and the tip of the pressure member side separating means 19A facing the pressure member. The gap GA is set smaller than the width W in the transport direction of the margin M1 on the leading end side of the recording material P in the transport direction. The pressure member side separation means 19A can also be configured in an appropriate form, but the pressure member side separation means 19A shown here is constituted by a sheet-like separation member 20A.
[0060]
When the first toner image TA already fixed is carried on one surface of the recording material P entering the nip N, and the second toner image T to be fixed by the fixing device 4 is carried on the other surface. When the first toner image TA passes through the nip N, the toner melts, and when the recording material P adheres to the surface of the pressure roller 16, the pressure member side separation means 19A separates the fixing member side separation. The recording material is prevented from being wound around the surface of the pressure roller 16 in the same manner as the means 19. Further, since the pressure member side separating means 19A is also separated from the surface of the pressure roller 16, it is possible to prevent a problem that the surface is damaged.
[0061]
Further, in the fixing apparatus shown in FIGS. 6 to 8, since the fixing member side separating means 19 and the pressing member side separating means 19A are provided together, the recording material P is added to the fixing member. It is possible to prevent the pressure member from being wound around any surface, and to prevent the surface of these members from being damaged by the contact of the separating means.
[0062]
The fixing device 4 shown in FIG. 9 is also configured to prevent the recording material from being wound around the surface of the pressure member. The basic configuration and the basic operation of the fixing device shown in FIG. 9 are the same as those of the fixing device shown in FIG. The difference is that the Asker C hardness of the surface of the pressure roller 16 is set lower than the Asker C hardness of the surface of the fixing roller 15, and the fixing roller 15 elastically compresses and deforms the pressure roller 16 at the nip N. It is a point. Further, in the fixing device shown in FIG. 9, no heater is provided in the pressure roller 16, a heater 17 is provided in the fixing roller 15, and the fixing roller 15 is heated by the heater 17, and the nip N Is maintained at an appropriate temperature suitable for fixing the toner image. In this case, the difference between the surface hardness of the fixing roller 15 and the pressure roller 16 is set to, for example, about 20 to 40 Hs in terms of Asker C hardness.
[0063]
A first toner image TA that has already been fixed is carried on one surface of the recording material P, and an unfixed second toner image T to be fixed by the fixing device 4 is held on the other surface of the recording material P. The recording material P, which is carried, is sent to the nip N between the fixing roller 15 and the pressure roller 16 that rotate in the direction of the arrow, as indicated by the arrow A, and passes therethrough, whereby the second toner image T is recorded. It is fixed on the material P.
[0064]
At this time, the toner of the first toner image TA is also heated and melted, but the recording material P that has exited the nip N is prevented from being wound around the surface of the pressure roller 16 due to melting of the toner of the first toner image. Therefore, the pressure member side separating means 19A for separating the recording material P that has exited the nip N from the surface of the pressure member made of the pressure roller 16 is disposed in a non-contact state with respect to the surface of the pressure member. Has been. FIG. 9 also shows a state where the entire margin M1 on the leading end side in the conveyance direction of the recording material P has just exited from the nip N. As can be seen from this drawing, the recording material P downstream in the recording material conveyance direction. The gap GA between the side end NE and the leading end of the pressure member side separating means 19A facing the pressure member is determined by the width W of the margin M1 on the leading end side in the transport direction of the recording material P in the transport direction. Is set too small. The pressure member side separating means 19A is also constituted by, for example, a sheet-like separating member 20A.
[0065]
In the fixing device shown in FIG. 9, since the surface hardness of the fixing roller 15 is set higher than the surface hardness of the pressure roller 16, only the margin M1 on the front end side of the recording material P to be conveyed is nipped. When coming out of N, the margin M1 takes a posture along the surface of the fixing roller 15 and is largely separated from the surface of the pressure roller 16. When only the margin M1 on the leading end side in the conveyance direction of the recording material P to be conveyed exits the nip N, the margin M1 on the leading end side is recorded on the downstream end NE of the nip N in the recording material conveyance direction and the recording on the nip N. The straight line LC connecting the upstream end NS in the material conveyance direction is configured to face the fixing member side with respect to the extended line LCC on the recording material conveyance direction side.
[0066]
When the image area IA (see FIG. 4) of the recording material P exits the nip N, the toner of the second toner image T carried on the other surface is melted at the nip N. Although the toner of the first toner image TA formed on one surface of the recording material P is also melted at the nip N, the recording material P may be pulled toward the pressure roller 16 side. . When the gap GA is smaller than the width W of the blank portion M1, the surface hardness of the pressure roller 16 is lower than the surface hardness of the fixing roller 15, and only the blank portion M1 comes out of the nip N, the blank portion M1 is added. Since the toner does not adhere to the surface of the pressure roller 16 due to the adhesive force of the toner, the recording material P does not wrap around the surface of the pressure roller 16 when the recording material P is pulled toward the pressure roller 16. . In addition, since the pressure member side separating means 19A has a low surface hardness and is therefore located away from the surface of the pressure roller 16 which is easily damaged, the surface is not damaged.
[0067]
Further, the front end portion of the fixing member side separation means 22A made of a sheet-like separation member or the like is in contact with the surface of the fixing roller 15, and therefore the recording material P that has exited the nip N adheres to the surface of the fixing roller 15. Even so, the recording material P is immediately separated from the surface of the fixing roller 15 by the fixing member side separating means 22 </ b> A, and the recording material P does not wrap around the surface of the fixing roller 15. The fixing member side separating means 22A is in contact with the surface of the fixing roller 15, but since the surface hardness of the fixing roller 15 is high, the surface can be prevented from being damaged. In this way, by causing the fixing member side separation means 22A to contact the surface of the fixing roller 15, the recording material P can be reliably prevented from being wound around the fixing roller 15. The recording material P that has exited the nip N is conveyed while being guided by the pressure member side separating means 19A and a guide member 21A disposed above the pressure member side separating means 19A.
[0068]
As described above, it is possible to prevent the recording material P from being wound around the fixing roller 15 and the pressure roller 16 and to prevent the surfaces of the rollers 15 and 16 from being scratched. It is possible to prevent the quality of the first and second toner images formed on each surface of the material P from being deteriorated.
[0069]
A more specific configuration of the fixing device 4 shown in FIG. 9 will be described as an example. As the fixing roller 15, for example, fluorine is formed on the outer peripheral surface of an iron hollow roller having an outer diameter of 40 mm and a wall thickness of 0.6 mm. What coated the release layer which consists of resin can be used. As the pressure roller 16, for example, a foamed silicone rubber layer having a thickness of 5 mm is formed on an aluminum core having an outer diameter of 40 mm and a PFA tube having a thickness of 30 μm is covered on the outer peripheral surface thereof. be able to. In this configuration, since the fixing roller 15 is not provided with an elastic layer, the heat capacity of the fixing roller 15 is reduced, and the rise time from when the power is turned on until the fixing roller 15 reaches a temperature at which the fixing roller 15 can be fixed can be shortened.
[0070]
Further, the configuration in which the hardness on the surface side of the fixing member is larger than the hardness on the surface side of the pressure member can be applied even when the fixing member is formed of a fixing belt, and an example is shown in FIG. Since the basic idea of the fixing device 4 shown in FIG. 10 is the same as that of the fixing device shown in FIG. 9, the fixing member heated by the heaters 17A and 17B is a plurality of guide members. In this case, the endless fixing belt 15A is wound around the opposing roller 15B and the tension roller 15C and rotates in the direction of the arrow B, and the pressure member pressed against the fixing member is at least one guide via the fixing belt 15A. In the example shown in FIG. 10, the pressure roller 16 rotates in the direction of the arrow while being pressed against the opposing roller 15B. The Asker C hardness of the surface of the pressure roller 16 is set lower than the Asker C hardness measured on the surface of the fixing belt portion wound around the opposing roller 15B.
[0071]
The recording material P carrying the second toner image T to be fixed has a nip N formed by the pressure contact between the fixing belt 15A and the pressure roller 16 in the direction in which the second toner image T is in contact with the fixing belt 15A. The second toner image T is fixed to the recording material P by the action of heat and pressure.
[0072]
At that time, when only the margin M1 on the leading end side in the conveyance direction of the recording material P to be conveyed exits the nip N, the margin M1 on the leading end is downstream of the nip N in the recording material conveyance direction. The straight line LC connecting the end NE and the upstream end NS of the nip N in the recording material conveyance direction is directed toward the fixing member made of the fixing belt 15A rather than the extended line LCC on the recording material conveyance direction side.
[0073]
As indicated by an arrow A, a first toner image TA that has already been fixed is formed on one surface of the recording material P that enters the nip N. A pressure member side separating means 19A for separating the recording material P that has exited the nip N from the surface of the pressure member made of the pressure roller 16 is disposed in a non-contact state with respect to the surface of the pressure member. A gap GA between the downstream end NE of the nip N in the recording material conveyance direction and the tip of the pressure member side separating means 19A facing the pressure member is a blank portion on the front side of the recording material P in the conveyance direction. The width M1 is set to be smaller than the width W in the transport direction. With this configuration, the recording material P can be prevented from being wound around the pressure roller 16 as in the case of the fixing device shown in FIG. It is also possible to prevent the pressure roller having a low surface hardness from being damaged by the pressure member side separating means 19A. Further, it is possible to prevent the recording material P from being wrapped around the fixing belt 15A by the fixing member side separating means 22A in contact with the surface of the fixing belt 15A. The recording material P exiting the nip N is guided and conveyed by the pressure member side separating means 19A and the guide member 21A.
[0074]
Also in the fixing device 4 shown in FIGS. 9 and 10, when only the front end side margin M1 of the recording material P exits the nip N, the margin M1 faces the fixing member side from the extension line LCC. The Asker C hardness of the surface of the fixing member at the downstream end NE of the nip N in the recording material conveyance direction is set to be higher than the Asker C hardness of the surface of the pressure member at the downstream end NE of the nip N in the recording material conveyance direction. ing. In addition, as described above, the fixing member side separating means 22A for separating the recording material P that has exited the nip N from the fixing member is provided, and the leading end of the fixing member side separating means 22A contacts the surface of the fixing member. Therefore, the recording material can be effectively prevented from being wound around the fixing member. At that time, since the hardness of the surface of the fixing member is high, it is possible to prevent the surface of the fixing member from being damaged by the fixing member side separating means 22A that comes into contact.
[0075]
By the way, in each of the above-described embodiments, the gap G between the tip of the fixing member side separating means 19 that is located away from the fixing member and the downstream end NE of the nip N in the recording material conveyance direction is a recording gap. Since the width is set smaller than the width W of the margin part M1 on the leading end side in the conveyance direction of the material P, the leading end of the fixing member side separating means 19 is positioned close to the surface of the fixing member. In order to correctly arrange the fixing member side separating means 19 at such a position, it is advantageous to employ the following configuration.
[0076]
FIG. 11 shows an example of a configuration for positioning the fixing member side separating means 19 made of the sheet-like separating member 20 with respect to the fixing roller 15 shown in FIGS. 2 and 6. As shown in FIG. 11, a gap holding member 29 is fixed to each end of the fixing member 20 in a direction orthogonal to the recording material conveyance direction, and each gap holding member 29 is connected via a screw 30. It is supported by the support member 31. The support member 31 is pressurized toward the surface of the fixing roller 15 by a pressure member 32 made of a compression spring or the like. As a result, both gap holding members 29 come into contact with the surface of the fixing roller 15. At that time, as shown in FIG. 12, both gap holding members 29 abut against the recording material non-passing area PA of the fixing roller 15, that is, the respective end areas in the longitudinal direction of the fixing roller through which the recording material P does not pass. As a result, the gap between the region through which the recording material passes, that is, the tip of the fixing member side separating means 19 facing the recording material passage region PB, and the surface of the fixing roller 15 and the gap G described above are correctly maintained.
[0077]
The position of the surface of the fixing roller 15 is not constant due to thermal expansion or eccentricity of the roller, but the gap G is separated from the fixing member side by positioning the fixing member side separating means 19 as described above. It can always be kept substantially constant over the entire longitudinal direction of the means 19. In addition, since the gap holding member 29 contacts the recording material non-passing area PA of the fixing roller 15, the gap holding member 29 does not damage the recording material passing area PB of the fixing roller 15, and the gap holding member 29 is fixed. The toner image is not affected by the contact with the surface of the roller 15.
[0078]
Even when the fixing member is formed of the fixing belt 15A shown in FIGS. 5 and 8, the gap holding member 29 is brought into contact with the recording material non-passing area of the fixing belt 15A in the same manner as described above, thereby fixing the fixing member side. The gap between the separation means 19 and the surface of the fixing belt 15A and the gap G can be regulated correctly.
[0079]
As described above, a gap holding member is provided at each end of the separating member in a direction orthogonal to the recording material conveyance direction, and both the gap holding members are brought into contact with the recording material non-passing area of the fixing member for separation. By maintaining the distance between the front end of the member and the surface of the fixing member, the front end of the separating member can be easily positioned close to the fixing member and correctly positioned.
[0080]
In order to arrange the pressure member side separating means 19A of the fixing device shown in FIGS. 6, 8, 9 and 10 close to the surface of the pressure roller 16, the structure shown in FIGS. Can be adopted. In this case, in place of the fixing roller 15 shown in FIGS. 11 and 12, the pressure roller 16 shown in FIG. 6, 8, 9 or 10 is arranged. In this way, a gap holding member is provided at each end of the pressure member separating means in a direction orthogonal to the recording material conveyance direction, and the gap holding member is brought into contact with the recording material non-passing area of the pressure member. The distance between the tip of the pressure member side separation means and the surface of the pressure member can be maintained, and thereby the pressure member side separation means can be positioned close to the surface of the pressure member and correctly positioned. it can. In addition, since the gap holding member is in contact with the recording material non-passing area of the pressing member, it is possible to prevent a problem that the recording material passing area of the pressing member is damaged.
[0081]
By the way, the fixing member side separation means 19 and the pressure member side separation means 19A separated from the fixing member or the pressure member are constituted by separation claws made of a single plate material in addition to the sheet-like separation members 20 and 20A. The separating means composed of a plurality of separating claws arranged along the surface of the fixing member or the pressure member can be used as appropriate. Since the means 19A is arranged in a non-contact manner with respect to the fixing member or the pressure member, each of the separating means 19 and 19A is a single separating member made of a sheet or plate as shown in the illustrated example. Can be used. When the separation means is in contact with the surface of the fixing member or the pressure member, the separation means composed of a plurality of separation claws is used, and the contact pressure against each of the separation claws and the fixing member or the pressure member is adjusted by a spring. In this example, the fixing member side separation means 19 and the pressure member side separation means 19A are not in contact with the fixing member or the pressure member. Therefore, it is not necessary to adjust the contact pressure, and the fixing member side separating means 19 and the pressure member side separating means 19A constituted by one separating member can be adopted. By configuring the separating means 19 and 19A in this way, it is possible to reduce the number of parts and the cost thereof. Further, since it is not necessary to provide a spring for adjusting the contact pressure with which the fixing member side separating means 19 and the pressure member side separating means 19A abut on the fixing member or the pressure member, each of the separating means 19 and 19A is used for a recording material. It can also be formed integrally with the guide member or the casing (not shown) of the fixing device.
[0082]
Further, as shown in FIG. 11, when one or a plurality of openings 36 for ventilation are formed in one separating member 20 constituting the fixing member side separating means 19, the recording material P heated from the nip N is used. The water vapor that exits can be released, for example, upward through the opening 36, thereby preventing the water vapor from condensing on the recording material P and deteriorating its quality. The opening 36 penetrates in the thickness direction of the sheet-like separation member 20. Similarly, when one or more openings for ventilation are formed in one separation member 20A constituting the pressure member side separation means 19A, water vapor emitted from the recording material can be released through the openings.
[0083]
In the case where the fixing member side separating means 19 and the pressure member side separating means 19A are constituted by sheet-like separating members 20 and 20A as in the illustrated example, particularly when the thickness is thin, the heat of these separating members themselves. The spacing between the separation member 20, 20A and the fixing member or the pressure member becomes non-uniform in the longitudinal direction of the separation member due to undulation due to expansion or deformation due to the recording material coming into contact with the separation member 20, 20A. There is a fear. Therefore, when the fixing member side separating means 19 and the pressure member side separating means 19A are constituted by sheet-like separating members 20, 20A, the separating members 20, 20A are oriented in a direction orthogonal to the recording material conveyance direction. It is desirable to provide tension applying means for pulling. Thereby, generation | occurrence | production of the said malfunction can be prevented.
[0084]
The separation member 20 shown in FIG. 11 is fixed to the gap holding member 29 at each end in the longitudinal direction, and both the gap holding members 29 are supported by the support member 31 via the screws 30. By rotating 30, the separating member 20 is pulled in the direction of the arrow, and tension is applied to the separating member 20 to keep the separating member 20 flat, and the distance between the separating member 20 and the fixing roller 15 is kept constant. be able to. Thus, the screw 30 constitutes an example of tension applying means for pulling the separating member. The tension applying means for pulling the separating member 20A of the pressure member-side separating means 19A can be similarly configured.
[0085]
As the sheet-like separation members 20 and 20A, a thin plate made of heat-resistant resin or metal can be used. For example, a polyimide sheet having a thickness of 0.1 mm coated with a fluororesin can be used. Further, when a metal sheet or metal plate having a thickness of 0.2 mm or more is used as the separation member 20 or 20A, the rigidity is increased. Therefore, the separation member and the fixing member can be fixed without providing the tension applying means. It becomes possible to keep the space | interval between a member or a pressurization member constant.
[0086]
By the way, in each of the fixing devices described above, a release agent such as silicone oil can be applied to the fixing member or the pressure member in order to more reliably prevent the recording material from being wrapped around. However, when this configuration is adopted, the oil adheres to the recording material and the recording material becomes dirty, the maintenance for applying the oil becomes complicated, and the application member for applying the oil is required, and the cost of the fixing device is increased. We cannot escape the rising drawbacks.
[0087]
Therefore, if a wax-containing toner is used as the toner and the toner image is formed by a toner containing at least a resin, a colorant and a wax, so-called oil-less operation without applying a release agent becomes possible. , The above-mentioned problems can be eliminated.
[0088]
Each configuration described above can be widely applied to fixing devices other than the types described above. For example, in the fixing device 4 shown in FIGS. 5, 8, and 10, guide rollers, that is, the opposing roller 15B and the tension roller 15C are used as guide members for winding the fixing belt 15A. In the fixing device 4, two guide rollers 33 and 34 and a guide member configured as a heater 35 are used, and a fixing belt 15 </ b> A is wound around these guide members. Although not shown in the drawing, the heater 35 has a pair of electrodes and a resistor disposed between the electrodes and in contact with the inner surface of the fixing belt 15A. By supplying a current to the resistor, the resistor 35 is provided. Is heated so that the fixing belt 15A is heated. The configuration described above with reference to FIGS. 5, 8, and 10 can also be adopted for such a fixing device.
[0089]
Furthermore, as described above, the pressure member can be constituted by a pressure belt that is wound around a plurality of guide members and rotated. Also in this case, when the pressure belt portion wound around the guide member is in contact with the fixing member so as to form a nip, the Asker C hardness of the surface of the pressure belt is determined by winding around the guide member. It is the hardness measured on the surface of the applied pressure belt portion. In addition, the value of Asker C hardness described in this specification is a numerical value obtained by directly measuring the surface hardness of a roller or a belt using an Asker C hardness meter.
[0090]
【The invention's effect】
According to the present invention, it is possible to prevent the recording material from being wound around the fixing member and to prevent a defect that the surface of the fixing member is damaged by the separation member.
[0091]
According to the inventions according to claims 5 to 8, the recording material can be prevented from being wound around the pressure member.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view illustrating an example of an image forming apparatus.
FIG. 2 is a cross-sectional view illustrating an example of a fixing device.
FIG. 3 is an enlarged explanatory view of the fixing device shown in FIG. 2;
FIG. 4 is a diagram illustrating a margin portion of a recording material.
FIG. 5 is a cross-sectional view illustrating another example of the fixing device.
FIG. 6 is a cross-sectional view illustrating still another example of the fixing device.
FIG. 7 is an enlarged explanatory view of the fixing device shown in FIG.
FIG. 8 is a cross-sectional view illustrating still another example of the fixing device.
FIG. 9 is a cross-sectional view illustrating still another example of the fixing device.
FIG. 10 is a cross-sectional view illustrating still another example of the fixing device.
FIG. 11 is a plan view showing an example of a separation member support device.
12 is a perspective view illustrating a state in which the gap holding member illustrated in FIG. 11 is in contact with the surface of the fixing roller.
FIG. 13 is an explanatory diagram illustrating still another example of the fixing device.
[Explanation of symbols]
4 Fixing device
20 Separation member
22 Pressure member side separating means
29 Gap holding member
36 opening
G gap
LA straight line
LAA extension line
M1 margin
N nip
NE Downstream end in the recording material conveyance direction
NS Upstream end in the recording material conveyance direction
P Recording material
PA recording material non-passing area
T Toner image
W width

Claims (8)

A fixing member that is heated and a pressure member that is in pressure contact with the fixing member, and a recording material that carries a toner image to be fixed is oriented so that the toner image is in contact with the fixing member. In an image forming apparatus having a fixing device that passes a nip formed by pressure contact with a pressure member and fixes the toner image on a recording material by the action of heat and pressure.
When only the margin portion on the leading end side in the conveyance direction of the recording material to be conveyed exits the nip, the margin portion on the leading end side becomes the downstream end in the recording material conveyance direction of the nip and the upstream side in the recording material conveyance direction of the nip. A sheet-like separating member for separating the recording material that has exited the nip from the surface of the fixing member is configured to face the pressure member side with respect to a linear extension line connecting the ends. It is arranged in a non-contact state with respect to the surface, and the gap between the downstream end in the recording material conveyance direction of the nip and the leading end of the separation member is set in the conveyance direction of the blank portion on the leading end side in the recording material conveyance direction. An image forming apparatus, wherein an opening penetrating in the thickness direction is formed in the separation member. A fixing member that is heated and a pressure member that is in pressure contact with the fixing member, and a recording material that carries a toner image to be fixed is oriented so that the toner image is in contact with the fixing member. In an image forming apparatus having a fixing device that passes a nip formed by pressure contact with a pressure member and fixes the toner image on a recording material by the action of heat and pressure.
A sheet-like separating member for separating the recording material that has exited the nip from the surface of the fixing member is disposed in a non-contact state with respect to the surface of the fixing member, and an Asker on the surface of the pressure member in the nip. The C hardness is set to be higher than the Asker C hardness of the surface of the fixing member in the nip, and a gap between the downstream end in the recording material conveyance direction of the nip and the leading end of the separation member is set in the conveyance direction of the recording material. An image forming apparatus, wherein an opening penetrating in a thickness direction is formed in the separation member, the margin being set to be smaller than a width in a conveyance direction of a margin part on a front end side. The fixing member is composed of an endless fixing belt wound around a guide member, and the pressure member is in pressure contact with the guide member via the fixing belt, and has an Asker C hardness on the surface of the pressure member. The image forming apparatus according to claim 1, wherein the image forming apparatus is set to be higher than an Asker C hardness of a surface of the fixing belt portion wound around the guide member. A fixing member that is heated and a pressure member that is in pressure contact with the fixing member, and a recording material that carries a toner image to be fixed is oriented so that the toner image is in contact with the fixing member. In an image forming apparatus having a fixing device that passes a nip formed by pressure contact with a pressure member and fixes the toner image on a recording material by the action of heat and pressure.
A sheet-like separation member for separating the recording material that has exited the nip from the surface of the fixing member is disposed in a non-contact state with respect to the surface of the fixing member, and a convex shape is added to the nip. The pressure member elastically deforms the fixing member into a concave shape, and a gap between the downstream end of the nip in the recording material conveyance direction and the leading end of the separation member is formed in a blank portion on the leading end side of the recording material in the conveyance direction. The image forming apparatus is characterized in that the width is set smaller than the width in the conveying direction, and the separation member has an opening penetrating in the thickness direction. A pressure member separating means for separating the recording material that has exited the nip from the surface of the pressure member is provided, and the tip of the pressure member separating means is brought into contact with the surface of the pressure member. Item 5. The image forming apparatus according to any one of Items 1 to 4. A gap holding member is provided at each end of the separating member in a direction orthogonal to the recording material conveyance direction, and the gap holding member is brought into contact with the recording material non-passing area of the fixing member, so that the separation member The image forming apparatus according to claim 1, wherein an interval between the front end and the surface of the fixing member is maintained. The image forming apparatus according to claim 1, further comprising a tension applying unit that pulls the separation member in a direction orthogonal to the recording material conveyance direction. The image forming apparatus according to claim 1, wherein the toner image is formed of a toner containing at least a resin, a colorant, and a wax.

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