JP2003107947A - Fixing device and image forming device having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a fixing device where a toner image is fixed by the action of heat and pressure by making recording paper carrying a toner image pass through a nip between a fixing roller and a pressure roller press-contacting with the fixing roller in a state where it is set in a direction where the toner image comes into contact with the fixing roller, and in which the recording material outgoing from the nip is prevented from being wound round the fixing roller. SOLUTION: The surface hardness of the pressure roller 16 is set to be higher than that of the fixing roller 15, and a fixing member side separation means 19 for separating the recording material P outgoing from the nip N from the roller 15 is arranged away from the surface of the roller 15, and a gap G between the end NE on the downstream side of the nip N in a recording material carrying direction and the separation means 19 is set to be smaller than the width W of the margin part M1 on the leading edge side of the recording material P in the carrying direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a recording material having a fixing member to be heated and a pressure member in pressure contact with the fixing member and carrying a toner image to be fixed. A fixing device for fixing the toner image on a recording material by the action of heat and pressure by passing through a nip formed by pressure contact between the fixing member and a pressure member in the direction of contacting the member, and the fixing device. The present invention relates to an image forming apparatus having the same.

[0002]

2. Description of the Related Art It is well known in the prior art to employ a fixing device of the above type in an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunctional machine having at least two functions of these. 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, so that the toner acts as an adhesive and the nip is prevented. The ejected recording material may be wound around the surface of the fixing member without being separated from the surface. In particular, in an image forming apparatus that forms a full-color image, a plurality of toner images of different colors are superposed on a recording material, and the superposed toner images are fixed by a fixing device. The toner is melted, which increases the adhesive force of the toner and makes it easier for the recording material to wind around the fixing member.

Therefore, conventionally, a separating means composed of 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 surface of the fixing member by the separating claw, and the recording material is the surface of the fixing member. It is configured so that it can be prevented from winding around. However, since the tip of the separation claw is in contact with the surface of the fixing member, the separation claw may damage the surface of the fixing member. When the surface of the fixing member is scratched, a mark corresponding to the scratch is formed on the toner image passing through the nip, and the image quality of the toner image after fixing is deteriorated.

In order to eliminate such a defect, there has been proposed a fixing device in which a separating claw is arranged apart from the surface of the fixing member. However, if the separation claw is placed in a non-contact state with the surface of the fixing member, the recording material that has left the nip enters the space 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 being wrapped around the member. When the separating claws separated from the fixing member are used as described above, the separating function of the recording material is deteriorated, and the possibility that the recording material is wound around the fixing member is increased.

Further, a toner image already fixed may be formed on the opposite surface of the recording material carrying the toner image to be fixed. When the recording material passes through the nip, the opposite side is formed. Since the toner image on the surface is melted by heat, the recording material may be wound around the surface of the pressure member. In order to prevent such a problem, the separation claw may be brought into contact with the surface of the pressing member, but this causes the same problem as described above.

[0006]

SUMMARY OF THE INVENTION The first object of the present invention is to effectively prevent the recording material from winding around and to effectively suppress the problem that the image quality of the toner image after fixing is deteriorated. The object is to provide a fixing device of the type described at the beginning.

A second object of the present invention is to provide an image forming apparatus having the above fixing device.

[0008]

SUMMARY OF THE INVENTION In order to achieve the first object of the present invention, in the fixing device of the type described at the beginning, only the margin portion on the leading end side of the recording material to be conveyed in the conveying direction is the nip. When exiting, the margin on the leading end side faces the pressure member side with respect to the straight line extending between the downstream end of the nip in the recording material transport direction and the upstream end of the nip in the recording material transport direction. And a fixing member side separating means for separating the recording material exiting the nip from the surface of the fixing member is arranged in a non-contact state with respect to the surface of the fixing member,
The gap between the downstream end of the nip in the recording material conveyance direction and the tip of the fixing member side separating means is set to be smaller than the width of the margin portion on the leading end side of the recording material in the conveyance direction in the conveyance direction. A fixing device is proposed (claim 1).

Further, in the fixing device according to the first aspect, the Asker C hardness of the surface of the pressing member at the downstream end of the nip in the recording material conveyance direction is fixed at the downstream end of the nip in the recording material conveyance direction. It is advantageous to set the hardness higher than the Asker C hardness of the surface of the member (claim 2).

Further, in the fixing device according to claim 1 or 2, there is provided a pressure member side separating means for separating the recording material exiting the nip from the surface of the pressure member.
It is advantageous to bring the tip of the pressing member side separating means into contact with the surface of the pressing member (claim 3).

In order to achieve the first object of the present invention, in the fixing device of the type described at the beginning, when only the margin portion on the leading end side of the recording material to be conveyed in the conveying direction exits the nip. The margin on the leading end side is configured to be substantially oriented in the direction of an extension line of a straight 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. Fixing member-side separating means for separating the ejected recording material from the surface of the fixing member is arranged in a non-contact state with respect to the surface of the fixing member, and the downstream end of the nip in the recording material conveying direction and the fixing A fixing device is proposed in which a gap between the leading end of the member-side separating means and the leading end side of the recording material is set to be smaller than a width of the margin portion in the carrying direction in the carrying direction (claim 4). ).

Further, in order to achieve the first object of the present invention, in the fixing device of the type described at the beginning, when only the margin on the leading end side of the recording material to be conveyed exits the nip. The margin on the leading end side is configured to be substantially oriented in the direction of an extension line of a straight 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. A pressure member side separating means for separating the ejected recording material from the surface of the pressure member is arranged in a non-contact state with respect to the surface of the pressure member, and the downstream end of the nip in the recording material conveying direction. The fixing device is characterized in that the gap between the pressure member-side separating means and the tip of the pressure member-side separating means is set to be smaller than the width of the margin portion of the recording material in the conveying direction at the leading end side in the conveying direction. (Claim 5).

Further, in order to achieve the first object of the present invention, in the fixing device of the type described at the beginning, when only the margin on the leading end side of the recording material to be conveyed in the conveying direction exits the nip. The margin on the leading end side is configured to be substantially oriented in the direction of an extension line of a straight 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. Fixing member-side separating means for separating the ejected recording material from the surface of the fixing member is arranged in a non-contact state with respect to the surface of the fixing member, and the downstream end of the nip in the recording material conveying direction and the fixing The gap between the leading end of the member-side separating means is set to be smaller than the width of the margin portion on the leading end side in the transport direction of the recording material in the transport direction, and the recording material exiting the nip is applied to the pressing member. Pressurization part for separating from the surface of The side separating means is arranged in a non-contact state with respect to the surface of the pressing member, and the gap between the downstream end of the nip in the recording material conveying direction and the tip of the pressing member side separating means is set to the recording position. In the margin of the front side of the material in the conveying direction,
A fixing device is proposed in which the width is set smaller than the width in the carrying direction (claim 6).

Further, in the fixing device according to any one of claims 4 to 6, the Asker C hardness of the surface of the fixing member at the downstream end of the nip in the recording material conveying direction,
It is advantageous to set the Asker C hardness of the surface of the pressing member at the downstream end of the nip in the recording material conveying direction to be substantially equal (claim 7).

Further, in order to achieve the first object of the present invention, in the fixing device of the type described at the beginning, when only the margin portion on the leading end side in the transport direction of the transported recording material exits the nip. The margin portion on the leading end side is configured to face the fixing member side with respect to a straight line extending between a downstream end of the nip in the recording material conveyance direction and an upstream end of the nip in the recording material conveyance direction. A pressure member side separating means for separating the recording material exiting the nip from the surface of the pressure member is arranged in a non-contact state with respect to the surface of the pressure member, and is located downstream of the nip in the recording material conveyance direction. A fixing device is characterized in that a gap between a side end and a tip of the pressure member side separating means is set to be smaller than a width of a margin portion of the recording material on the leading end side in the carrying direction in the carrying direction. Propose (Claim 8).

Further, in the fixing device according to the above-mentioned claim 8, the Asker C hardness of the surface of the fixing member at the downstream end of the nip in the recording material conveying direction is applied to the press at the downstream end of the nip in the recording material conveying direction. It is advantageous to set the hardness higher than the Asker C hardness of the surface of the member (claim 9).

Further, in the fixing device according to claim 8 or 9, there is provided a fixing member side separating means for separating the recording material from the nip from the fixing member, and the tip of the fixing member side separating means. It is advantageous to bring the part into contact with the surface of the fixing member (claim 10).

Further, in the fixing device described in any one of 1 to 4, 6 and 7, a gap holding member is provided at each end of the fixing member side separating means in a direction orthogonal to the recording material conveying direction. It is advantageous to bring the gap holding member into contact with the recording material non-passing area of the fixing member to maintain the distance between the tip of the fixing member side separating means and the surface of the fixing member (claim 11). .

Further, in the fixing device according to any one of claims 5 to 10, a gap holding member is provided at each end of the pressing member side separating means in a direction orthogonal to the recording material conveying direction, It is advantageous to bring the gap holding member into contact with the recording material non-passing region of the pressure member to maintain a gap between the tip of the pressure member side separating means and the surface of the pressure member (claim 3). 12).

Further, the above-mentioned claims 1 to 4, 6, 7 and 1
In the fixing device according to any one of 1 to 3, it is advantageous that the fixing member side separating means is constituted by one separating member (claim 13).

Further, the above claims 5 to 10 and 12
In the fixing device described in any one of (1) to (4), it is advantageous that the pressure member side separating means is composed of one separating member (claim 14).

Further, in the fixing device of the thirteenth aspect, it is advantageous that an opening for ventilation is formed in the separating member which constitutes the fixing member side separating means (the fifteenth aspect).

Further, in the fixing device according to claim 14, it is advantageous that an opening for ventilation is formed in the separating member which constitutes the pressing member side separating means (claim 16).

The above-mentioned claims 1 to 4, 6, 7, 1
16. The fixing device according to any one of 1, 13, and 15 wherein the fixing member-side separating means is composed of a sheet-shaped separating member, and a tension for pulling the separating member in a direction orthogonal to a recording material conveyance direction. It is advantageous to provide the application means (claim 17).

Further, the above claims 5 to 10, 12, 1
In the fixing device according to any one of 4 and 16, the pressing member side separating means is constituted by a sheet-like separating member, and tension is applied to pull the separating member in a direction orthogonal to the recording material conveyance direction. It is advantageous to provide means (claim 18).

Further, in the fixing device according to any one of claims 1 to 18, it is advantageous that the toner image is formed by a toner containing at least a resin, a colorant and a wax (claim 19). .

Further, in order to achieve the second object, the present invention proposes an image forming apparatus including the fixing device according to any one of claims 1 to 19 (claim 20). .

[0028]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a vertical sectional view showing an outline of an image forming apparatus. In the main body 1 of the image forming apparatus, an image forming means 2 for forming a toner image on a recording material, and a recording material for the image forming means. A feeding unit 3 that feeds the toner and a fixing device 4 that fixes the toner image formed on the recording material are provided. In FIG. 1, the fixing device 4 is shown as a simple block, but a specific configuration example thereof will be described later. Here, first, the image forming unit 2
Clarify the outline of.

The image forming means 2 exemplified here has a drum-shaped photoconductor 5 which is an example of an image carrier. When the photoconductor 5 rotates clockwise, the surface of the photoconductor is changed by the charging device 6. It is charged to a predetermined polarity. 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 device, whereby an electrostatic latent image is formed on the surface of the photoconductor. This electrostatic latent image is visualized as a toner image by the developing device 8, and the toner image is transferred onto the recording material sent from the feeding means 3 by the action of the transfer device 9. The transfer residual toner adhering to the surface of the photoreceptor after the toner image transfer is removed by the cleaning device 10.

The feeding means 3 has a cassette 11 containing a recording material P made of, for example, a transfer paper or a resin sheet, and the uppermost recording material P is rotated by the rotation of the feeding roller 12.
Are sent out from the cassette 11. The recording material sent out is rotated by the pair of registration rollers 13 to cause the photosensitive member 5 to move.
The toner image on the photoconductor 5 is transferred onto the recording material as described above. The recording material carrying the toner image in this manner 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 described later. . The recording material that has passed through the fixing device 4 is discharged onto a tray 14 outside the machine.

FIG. 2 is an enlarged sectional view showing an example of the fixing device 4. In the fixing device 4 shown here, a fixing member configured as a fixing roller 15 and a pressure roller 16 in pressure contact with the fixing roller 15. And a pressing member configured as described above, and the nip N is formed by pressing these rollers 15 and 16 against each other. The fixing roller 15 and the pressure roller 16 are formed in a columnar shape having outer circumferences of a circular cross section. In the illustrated example, the rollers 15 and 16 are formed in a hollow cylindrical shape, the fixing roller 15 rotates clockwise, and the pressure roller 16 rotates counterclockwise.

The nip N formed by the pressure contact between the rollers 15 and 16 is controlled by the heating means to an appropriate temperature suitable for fixing the toner image. In this example, the fixing roller 15
Halogen heaters 17 and 18 as heat sources are provided inside the pressure roller 16 and the pressure roller 16, respectively, and the temperature control means (not shown) turns on and off electricity to the heaters 17 and 18.
The FF is controlled and the temperature of the nip N is maintained at an appropriate temperature.

The recording material P carrying the unfixed toner image T is
The recording material P is fed into the fixing device 4 as indicated by an arrow A, the recording material P passes through the nip N in a direction in which the toner image T contacts the surface of the fixing roller 15, and the toner image T is recorded by heat and pressure. It is fixed on the material P.

As described above, the fixing device has a fixing member that rotates while being heated, and a pressure member that rotates while being in pressure contact with the fixing member, and a recording material carrying a toner image to be fixed, The toner image is passed through the nip formed by the pressure contact between the fixing member and the pressure member in the direction in which the toner image contacts the fixing member, and the toner image is fixed on the recording material by the action of heat and pressure. ing. The basic configuration is the same in the fixing device of each example described later. As described above, in the example shown in FIG. 2, the fixing member is constituted by the rotating fixing roller 15, and the pressing member rotates while pressingly contacting the fixing roller 15.
However, as will be described later, the fixing member is
The endless fixing belt may be wound around the guide member to rotate, and the pressure member may be formed of an endless pressure belt wound to rotate around the guide member. As described above, the fixing member and the pressure member can be configured in various forms.

Here, in the fixing device 4 shown in FIG. 2, the toner image T carried on the recording material P is fixed to the fixing roller 15.
The toner melts in the nip N when passing through the nip N between the pressure roller 16 and the pressure roller 16. The recording material P ejected from the nip N due to the adhesive force of the toner at this time causes the fixing roller 15
The following configuration is adopted to prevent the surface of the wrapping from being wound.

FIG. 3 shows the fixing roller 15 and the pressure roller 16.
9 is an enlarged explanatory view of a nip N formed by and a recording material P passing through the nip N. FIG. As shown in FIGS. 2 and 3, the recording material P exiting the nip N near the exit of the nip N.
Is separated from the surface of the fixing member (the fixing roller 15 in this example) by a fixing member side separating means 19 arranged in a non-contact state with the surface of the fixing member. The fixing member side separating means can be configured in an appropriate form, but the fixing member side separating means 19 shown here is constituted by a sheet-like separating member 20.

On the other hand, the recording material P is shaded in FIG.
In addition, a toner image is formed in the image area indicated by reference numeral IA, and the outer edge area of the image area IA is a blank portion M where no toner image is formed. Recording material P is arrow A
The sheet is conveyed in the direction indicated by and enters the fixing device 4, and the width of the margin portion M1 on the leading end side in the conveying direction is W in the conveying direction A. This width W is, for example, about 2 to 5 mm. 2 and 3 show a state where only the margin portion M1 on the front end side just comes out of the nip N. this is,
The same applies to FIGS. 5 to 10.

Here, as shown in FIG. 3, the exit end of the nip N, that is, the downstream end NE of the nip N in the recording material conveying direction NE.
And G is the gap between the fixing member side separating means 19 and the tip facing the fixing member, the gap G is
The width M of the margin portion M1 on the leading end side of the recording material P in the transport direction is set smaller than the width W in the transport direction A (G).
<W). Therefore, as shown in FIGS. 2 and 3, when only the entire margin portion M1 on the leading end side of the recording material P exits from the nip N, the leading end of the fixing member side separating means 19 is fixed to the margin portion M1. It is positioned so as to enter the space area between the roller 15.

On the other hand, the Asker C hardness of the surface of the pressure roller 16 is set higher than the Asker C hardness of the surface of the fixing roller 15, and preferably the Asker C hardness of the surface of the pressure roller 16 is fixed. It is configured to be 20 to 40 Hs larger than the Asker C hardness of the surface of the roller 15. By setting the surface hardness of the fixing roller 15 and the pressure roller 16 in this way, as shown in FIGS. 2 and 3, the pressure roller 16 is set so as to bite into the fixing roller 15 side. Compress and deform the surface. Fixing roller 15 pressed against pressure roller 16
The part is elastically deformed into a compressed state.

Therefore, as shown in FIGS. 2 and 3, when only the margin M1 on the front end side of the recording material P comes out of the nip N, the margin M1 is along the peripheral surface of the pressure roller 16. The posture, that is, the posture in which the fixing roller 15 is largely separated from the circumferential surface of the fixing roller 15 is taken. Since the toner image is not formed on the margin portion M1 on the front end side, the margin portion M1 does not try to adhere to the surface of the fixing roller 15 due to the adhesive force of the toner,
The margin M1 is discharged from the nip N along the peripheral surface of the pressure roller 16 that has bitten into the fixing roller 15 at the nip N. At this time, a large distance is provided between the margin M1 and the surface of the fixing roller 15, and in this state, the margin M1 of the recording material P does not wind around the surface of the fixing roller 15. Let LA be a straight line connecting the downstream end NE of the nip N in the recording material conveying direction and the upstream end NS of the nip N in the recording material conveying direction, and only the margin M1 on the leading end side of the recording material P to be conveyed in the conveying direction. When exiting the nip N, the margin M1 on the tip side faces the pressure member (pressure roller 16 in this example) side with respect to the extension line LAA drawn in the recording material conveyance direction side of the straight line LA. It is configured.

When the recording material P is conveyed further in the direction of arrow A than in the state shown in FIGS. 2 and 3, the image area IA shown in FIG. 4 begins to be discharged from the nip N. Then, the recording material P adheres to the surface of the fixing roller 15 or tries to adhere 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 having a weak stiffness such as thin paper.

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 as shown by the chain line in FIG. The recording material P is prevented from being wound around the surface of the fixing roller 15 by being guided by. Although the fixing member-side separating means 19 is arranged apart from the surface of the fixing roller 15, the gap G has a width W of the margin M1.
The recording material P pulled toward the fixing roller 15 by the adhesive force of the toner is wound around the surface of the fixing roller 15 through the gap G while being attached to the surface of the fixing roller 15. It will prevent you from continuing. The recording material P exiting from the nip N is continuously conveyed while being guided by the fixing member side separating means 19 located on the upper side and the guide member 21 located on the lower side thereof.

As described above, the recording material P exiting the nip N can be prevented from winding around the surface of the fixing roller 15, and the fixing member side separating means 19 is not in contact with the surface of the fixing roller 15. Therefore, it is possible to prevent the problem that the surface of the fixing roller 15 which has low hardness and is easily scratched is scratched by the fixing member side separating means 19.

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 the image forming apparatus for forming a color image, the recording material is used. For example, since a yellow toner image, a magenta toner image, a cyan toner image, and a black toner image are formed on top of each other, and the superposed toner image is fixed by a fixing device, conventionally, the recording material was particularly easy to wind around the fixing member. However, in the case of an image forming apparatus that forms a color image,
By adopting the above configuration, it is possible to prevent the recording material from winding around the fixing member while preventing the fixing member from being damaged.

Here, a more specific structural example of the fixing device 4 shown in FIG. 2 will be described.

The fixing roller 15 has 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, and the outer diameter of the fixing roller 15 is , 40 mm, for example. The cored bar 23 is composed of, for example, an iron hollow roller having an outer diameter of 34 mm and a wall thickness of 1 mm, the elastic layer 24 is formed of silicone rubber having a thickness of 3 mm, and the release layer 25 is, for example, 10 μm to 30 μm.
It is composed of a PFA tube with a thickness of μm. By providing the release layer 25, it is possible to prevent the recording material P from adhering to the surface of the fixing roller due to the adhesive force of the toner.

The pressure roller 16 has an outer diameter of 38 mm, for example.
A core metal 26 made of an iron hollow roller having a wall thickness of 1 mm, an elastic layer 27 laminated on the outer peripheral surface thereof, and a release layer 28 laminated on the outer peripheral surface thereof. The elastic layer 27 has, for example, a layer thickness of 1
The release layer 28 is made of silicone rubber having a thickness of 10 mm and is made of, for example, a PFA tube having a layer thickness of 10 μm to 30 μm.

The surface hardness of the fixing roller 15 is 45 Hs as Asker C hardness, and the surface hardness of the pressure roller 16 is 80 Hs as Asker C hardness.
Since the pressure roller 16 is harder in this way, the pressure roller 16 elastically deforms with the pressure roller 16 biting into the surface of the fixing roller 15, and the nip N is set at the nip N.
6 is formed along the outer shape.

In the fixing device 4 shown in FIG. 5, the fixing member is composed of an endless fixing belt 15A. The fixing belt 15A includes two guide rollers 15A.
It is wound around a guide member made of B and 15C.
The number of guide members may be three or more. On the other hand, the pressure member is composed of 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 have a circular outer circumference. It is formed in a columnar shape having a surface shape. In the example shown in FIG. 5, each of the rollers 15B, 15C and 16 is formed in a hollow cylindrical shape.

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 the pressure contact causes a nip. N is formed. The guide rollers 15B and 15C and the pressure roller 16 respectively rotate in the arrow direction, and thereby the fixing belt 15A is rotationally driven in the arrow B direction. Thus, when the endless fixing belt 15A rotates, the guide rollers 15B, 15
C is for guiding the fixing belt 15A, and one guide roller 15B facing the pressure roller 16 is provided.
Forms a nip N in cooperation with the pressure roller 16, and 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, and the fixing belt 15A may be wound around the guide member, or the pressure roller 16 may be pressed against the plurality of guide members via the fixing belt 15A. . The fixing member is composed of an endless fixing belt that is wound around a plurality of guide members to rotate, and the pressure member is at least 1 via the fixing belt.
It is composed of a pressure roller which is pressed against one of the guide members to rotate.

Focusing on the above-mentioned functions of both guide rollers 15B and 15C, in the following description, one guide roller 15B will be referred to as an opposing roller, and the other guide roller 15C will be referred to as a tension roller, if necessary. To do.

Further, in the fixing device shown in FIG.
Heaters 17A and 18 are provided inside the tension roller 15C and the pressure roller 16, respectively.
The fixing belt 15A and the pressure roller 16 are heated by 8, and the energization of the heaters 17A and 18 is controlled to be ON or OFF, so that the temperature of the nip N is maintained at an appropriate temperature suitable for fixing the toner image.

Also in this example, 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 is in contact with the surface of the fixing belt 15A as shown by an arrow A. The toner image T is fixed on the recording material P by the action of heat and pressure.

Also in the fixing device 4 shown in FIG. 5, the Asker C hardness of the surface of the pressure roller 16 was measured on the surface of the fixing belt portion wound around the guide member (opposing roller 15B in the example in the figure). It is set higher than Asker C hardness. Therefore, the fixing device 4 shown in FIG.
As in the case of the fixing device shown in FIG. 3, when only the margin M1 on the leading end side in the transport direction of the transported recording material exits the nip N,
The margin M1 on the leading end side includes a downstream end NE of the nip N in the recording material conveyance direction and an upstream end N of the nip N in the recording material conveyance direction.
An extension line LAA of the straight line LA connecting S to the recording material conveyance direction side
Than the pressing member (the pressing roller 16 in the illustrated example). Moreover, the recording material P exiting the nip N is fixed to the fixing belt 15A.
A fixing member side separating means 19 for separating the fixing member from the surface of the fixing member is arranged in a non-contact state with respect to the surface of the fixing member, and the downstream side end NE of the nip N in the recording material conveying direction.
The gap G between the end of the fixing member side separating means 19 facing the fixing member is set to be smaller than the width W of the margin portion M1 on the leading end side of the recording material P in the carrying direction in the carrying direction. There is.

With the above-described structure, the recording material P is prevented from being wound around the fixing member consisting of the fixing belt 15A, and the fixing member-side separating means 19 is used by the fixing member-side separating means 19 just like the fixing device shown in FIGS. It is possible to prevent scratches on the surface of 15A, improve the image quality of the toner image after fixing,
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. 2 and 3. There is no change.

A more specific structural example of the fixing device 4 shown in FIG. 5 will be described. The facing roller 15B and the pressure roller 1
6 can be configured in the same manner as the fixing roller 15 and the pressure roller 16 of the fixing device shown in FIG. Fixing belt 1
For example, 5A is obtained by laminating a 0.2 mm thick silicone rubber having an Asker C hardness of 30 Hs on a polyimide resin substrate having a thickness of 50 μm and coating PFA with a thickness of 5 μm as a release layer thereon. Can be used. Further, in the nip N shown in FIG. 5, the fixing belt 15A is provided at a portion where the pressure roller 16 does not face the facing roller 15B.
The first nip portion is in contact with only the first nip portion and the second nip portion is in which the pressure roller 16 is in contact with the counter roller 15B via the fixing belt 15A. This allows
A wide range of the 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.

Further, in the fixing device shown in FIG.
The fixing roller 15 includes a rubber elastic layer 24 having a poor thermal conductivity.
Since it is heated by the heater 17 from the inside of the fixing device, it takes a long time for the fixing roller 15 to rise to a temperature suitable for fixing the toner image when the fixing device is started up. However, in the fixing device shown in FIG. The fixing belt 15A having a small thickness and a small heat capacity is used as a fixing member, and the fixing belt 15A is not heated from the inside of the facing roller 15B but by the heater 17A in the thin tension roller 15C. Since it is heated, the fixing belt 15A
It is possible to shorten the time until the temperature rises to a temperature suitable for fixing the toner image.

In the fixing device shown in FIGS. 2 and 5, when only the leading end side margin M1 of the recording material P exits the nip N, the margin M1 faces the pressing member side from the extension line LAA. In order to do so, 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 as described above. Is composed of the fixing belt 15A, the hardness of the surface of the fixing member is, as described above,
It is the hardness when measured on the surface of the fixing belt portion wound around the facing roller 15B. In short, regardless of the form of the fixing member, the Asker C hardness of the surface of the pressing member at the downstream end NE of the nip N in the recording material conveying direction is fixed at the downstream end NE of the nip N in the recording material conveying direction. By setting the hardness higher than the Asker C hardness of the surface of the member, when only the tip side margin M1 exits the nip N,
The margin M1 can be configured to face the pressing member side with respect to the extension line LAA.

6 and 7 show another example of the fixing device 4. The basic structure of the fixing device 4 shown here is substantially the same as that of the fixing device shown in FIG. Therefore, each part of the fixing device shown in FIG. 6 corresponding to each part of the fixing device 4 shown in FIG. 2 is denoted by the same reference numeral as in FIG. 2, and the description of the basic configuration and its operation is omitted.

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 consisting of the fixing roller 15 and the pressure roller 1
The Asker C hardness of the surface of the pressure member made of No. 6 is set to be substantially equal. In this way, the fixing roller 1
By setting the surface hardness of 5 and the pressure roller 16,
A nip N formed by the fixing roller 15 and the pressure roller 16
In, the rollers 15 and 16 are compressed and deformed into a substantially flat form, and a linear nip N is formed. Therefore, FIG.
As shown in FIG. 5, when only the margin M1 on the leading end side of the conveyed recording material P exits the nip N, the margin M1 on the leading end side is the downstream end NE of the nip N in the recording material conveying direction. A straight line LB connecting the upstream end NS of the nip N in the recording material conveyance direction
The direction of the extension line LBB toward the recording material conveyance direction is substantially oriented. Further, in the fixing device 4 shown in FIGS. 6 and 7, the fixing member-side separating means 19 for separating the recording material P exiting the nip N from the surface of the fixing member including the fixing roller 15 is also included in the fixing member. Is arranged in a non-contact state with respect to the surface of the recording material, and the gap G between the downstream end NE of the nip N in the recording material conveyance direction and the tip of the fixing member side separating means 19 facing the fixing member is a recording material. Margin M on the front end side of P in the transport direction
1 is set to be smaller than the width W in the transport direction.

As shown in FIGS. 6 and 7, when only the leading end side margin portion M1 of the recording material P exits the nip N, a toner image is not formed in the margin portion M1. M1 does not try to adhere to the surface of the fixing roller 15 due to the adhesive force of the toner, and the margin M1 is discharged from the nip N along the extension line LBB of the nip N. In this state, the margin M1 of the recording material P is fixed. It does not wind around the surface of the roller 15. When the recording material P is conveyed further in the direction of arrow A than in the state shown in FIGS. 6 and 7, the image area IA shown in FIG. 4 begins to be discharged from the nip N, and the toner adheres on the image area IA. Since the recording material P adheres to the surface of the fixing roller 15 or tries to adhere to it by the force, the recording material P is pulled toward the fixing roller 15 side, but the fixing member side separating means 19 is provided in the vicinity of the fixing roller 15. Is provided, the recording material P is fixed to the fixing member side separating means 1
When the recording material P hits the recording medium P, the recording material P 1 is guided by the separating means 19 and is prevented from winding around the surface of the fixing roller 15. In this case as well, the fixing member side separating means 19 is arranged apart from the surface of the fixing roller 15, but the gap G is set to be smaller than the width W of the margin M1. It is possible to prevent the recording material P pulled toward the fixing roller 15 from being wound around the surface of the fixing roller 15 through the gap G while being attached to the surface of the fixing roller 15. The recording material P that has passed through the fixing device 4 is discharged onto the tray 14 shown in FIG.

As described above, also in the fixing device 4 shown in FIGS. 6 and 7, it is possible to prevent the recording material P exiting the nip N from winding around the surface of the fixing roller 15, and the fixing member side separating means. Since 19 is not in contact with the surface of the fixing roller 15, the hardness is low, and therefore the surface of the fixing roller 15 which is easily scratched can be prevented from being damaged by the fixing member side separating means 19. Moreover, since the nip N has a flat shape, the recording material exiting the nip is less likely to curl than the case where the nip N is curved as in the example shown in FIGS. 2 and 5. can get.

The fixing roller 15 of the fixing device 4 shown in FIG.
And the pressure roller 16 are, for example, the fixing device 4 shown in FIG.
The fixing roller 16 can be configured in the same manner. The surface hardness of the fixing roller 15 and the pressure roller 16 shown in FIG. 6 can be set to, for example, 45 Hs in Asker C hardness. Since the surfaces of the rollers 15 and 16 have substantially the same hardness as described above, the nip N is formed in a substantially flat shape.

FIG. 8 shows 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. The tension roller 15C shown in FIG. 5 is located to the right of the facing roller 15B, whereas the tension roller 15C shown in FIG. 8 is located above the facing roller 15B. 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 in FIG. 5, and the description of the basic configuration and its operation is omitted.

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 fixing belt 15A wound around the facing roller 15B is the same as that of the pressing member. This is that it is configured to have almost the same Asker C hardness on the surface of the pressure roller 16 as an example. Therefore, even in the fixing device 4 shown in FIG.
Also, as in the case of the fixing device shown in FIG. 7, only the margin M1 on the leading end side of the recording material P to be conveyed in the conveying direction is the nip N.
When the sheet exits, the margin portion M1 on the leading end side 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 in the recording material conveyance direction extends to the recording material conveyance direction side. It almost faces the direction of the extension line LBB. Moreover, the fixing member side separating means 19 for separating the recording material P exiting the nip N from the surface of the fixing member composed of the fixing belt 15A is arranged in a non-contact state with respect to the surface of the fixing member. Downstream side NE of the recording material conveying direction and the fixing member side separating means 19
The gap G between the front end of the recording material P facing the fixing member and the front end of the recording material P in the transport direction is set to be smaller than the width W of the blank portion M1 in the transport direction. This allows
Similar to the fixing device shown in FIGS. 6 and 7, it is possible to prevent the recording material P from wrapping around the surface of the fixing belt 15A, and moreover, the fixing member side separating means 19 is provided on the surface of the fixing belt 15A.
Therefore, it is possible to prevent the defect that the recording material P is scratched, and to prevent the recording material P that has exited the nip N from being easily curled.

In the fixing device shown in FIGS. 6 to 8, when only the leading end side margin M1 of the recording material P exits the nip N, the margin M1 is oriented substantially in the direction of the extension line LBB. For fixing roller 15 or fixing belt 15A
Surface hardness of the fixing member and the pressure roller 1
The surface hardness of the pressure member composed of 6 was set to be substantially equal as described above.
When it is composed of A, the hardness of the surface of the fixing member is the hardness measured on the surface of the fixing belt portion wound around the facing 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 of the nip N in the recording material conveying direction,
By setting the Asker C hardness of the surface of the pressing member at the downstream end NE of the nip N in the recording material conveyance direction to be substantially equal, when only the leading end side margin M1 exits the nip N, the margin M1 is It can be configured so as to face substantially the direction of the extension line LBB.

By the way, the image forming apparatus shown in FIG.
Although the toner image is formed only on one surface of the recording material P, the toner image on the photoconductor is transferred to one surface of the recording material, and the toner image is fixed by the fixing device. In the conventional image forming apparatus, the recording material is turned upside down and fed again to the photoconductor, the toner image on the photoconductor is transferred to the other surface of the recording material, and the transferred toner image is fixed by a fixing device. It is more 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 referred to as the first toner image and the latter is referred to as the second toner image. I will call it.

When the recording material is passed through the nip of the fixing device to fix the second toner image, the first toner image already fixed on one surface of the recording material also passes through the nip, and its first
The toner image contacts the pressure member. At this time, since the pressure member is also heated, the heat may melt the first toner image, and the recording material exiting the nip may wind around the surface of the pressure member.

Therefore, the fixing device 4 shown in FIGS. 2 and 5 is used.
In the above, there is provided a pressure member side separating means 22 for separating the recording material P exiting the nip N from the surface of the pressure member (the pressure roller 16 in the example of the figure), and further, the separating means 22. The tip end of the side facing the pressure member is in contact with the pressure member. The pressing member side separating means 22 is composed of, for example, a plurality of separating claws arranged in the axial direction of the pressing roller 16 or one sheet-like separating member.

As shown in FIGS. 2 and 5, the first material already fixed on one surface of the recording material P entering the nip N.
When the toner image TA is carried and the second toner image T to be fixed by the fixing device 4 is carried on the other surface of the recording material P, when the recording material P passes through the nip N, The toner image TA of is also heated and melted.
The recording material P that has exited from the recording medium P may wind around the surface of the pressure roller 16. In this case, the recording material P is applied by the pressure member side separating means 22 that is in contact with the surface of the pressure roller 16. It is separated from the surface of the pressure roller 16.

Since the tip of the pressing member side separating means 22 is in contact with the surface of the pressing member composed of the pressing roller 16, the recording material to be wound around the surface of the pressing roller 16 is surely secured. Can be separated from its surface. that time,
As described above, the surface hardness of the pressure roller 16 depends on the fixing roller 1.
Since the surface hardness of the pressure roller 16 is higher than that of No. 5, the surface of the pressure roller 16 is less likely to be scratched. It can be prevented.

Further, in the fixing device shown in FIGS. 6 to 8, as described above, when only the leading end side margin portion M1 of the conveyed recording material P exits the nip N, the leading end side margin portion M thereof.
1 is configured to be substantially oriented in the direction of the extension line LBB. In addition to this, a pressure member for separating the recording material P exiting the nip N from the surface of the pressure member composed of the pressure roller 16. The side separating means 19A is arranged in a non-contact state with respect to the surface of the pressing member, the downstream side end NE of the nip N in the recording material conveying direction, and the side facing the pressing member of the pressing member side separating means 19A. The gap GA between the leading end of the recording material P and the width W of the margin portion M1 on the leading end side in the carrying direction of the recording material P in the carrying direction.
Is set smaller than. The pressing member side separating means 19A can also be configured in an appropriate form, but the pressing member side separating means 19A shown here is composed of the separating member 20A on the sheet.

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. The first toner image TA is nip N
When the recording material P adheres to the surface of the pressure roller 16 due to melting of the toner when passing through the pressure roller 16, the pressure member side separating means 19A operates in exactly the same manner as the fixing member side separating means 19. The recording material is prevented from winding around the surface of the pressure roller 16. 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 the surface from being damaged.

Further, in the fixing device shown in FIGS. 6 to 8, both the fixing member side separating means 19 and the pressing member side separating means 19A are provided, so that the recording material P is fixed. It is possible to prevent the surfaces of the member and the pressing member from being wound around, and it is possible to prevent the surfaces of these members from being scratched by the contact of the separating means.

The fixing device 4 shown in FIG. 9 is also constructed so as to prevent the recording material from winding around the surface of the pressure member. The basic structure of the fixing device shown in FIG. 9 and its basic operation 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 to be lower than the Asker C hardness of the surface of the fixing roller 15, and the fixing roller 15 in the nip N has the Asker C hardness at the nip N.
The point is that elastically compressively deforms. Further, in the fixing device shown in FIG. 9, the heater is not provided in the pressure roller 16, but the heater 17 is provided in the fixing roller 15. The heater 17 heats the fixing roller 15 and the nip N Is maintained at an appropriate temperature suitable for fixing the toner image. Also in this case, the difference between the surface hardness of the fixing roller 15 and the surface hardness of the pressure roller 16 is, for example, 2 in Asker C hardness.
It is set to about 0 to 40 Hs.

The first toner image TA which has already been fixed is carried on one surface of the recording material P, and the unfixed second toner to be fixed by the fixing device 4 is carried on the other surface of the recording material P. The image T is carried, and the recording material P is fed into the nip N between the fixing roller 15 and the pressure roller 16 rotating in the arrow direction as shown by the arrow A, and passes through the nip N, whereby the second toner image is formed. T is fixed on the recording material P.

At this time, the toner of the first toner image TA is also heated and melted, but the recording material P exiting the nip N is
In order to prevent the toner of the toner image from being wound around the surface of the pressure roller 16 due to melting of the toner, the recording material P exiting from the nip N
A pressure member side separating means 19A for separating the pressure roller 16 from the surface of the pressure member is disposed in a non-contact state with the surface of the pressure member. FIG. 9 also shows a state in which the entire margin M1 on the front end side of the recording material P in the conveying direction has just come out of the nip N. As can be seen from this figure, the nip N is downstream in the recording material conveying direction. The gap GA between the side edge NE and the tip of the pressure member side separating means 19A on the side facing the pressure member is greater than the width W of the margin portion M1 on the front end side of the recording material P in the conveyance direction in the conveyance direction. Is also set small. The pressurizing member side separating means 19A is also composed of, for example, a sheet-like separating member 20A.

In the fixing device shown in FIG. 9, the fixing roller 1
Since the surface hardness of No. 5 is set higher than that of the pressure roller 16, when only the leading end side margin M1 of the recording material P being conveyed comes out of the nip 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. Recording material P being conveyed
When only the margin portion M1 on the leading end side of the nip N exits the nip N, the margin portion M1 on the leading end side of the nip N is located at the downstream end NE of the recording material transport direction and the upstream end of the nip N in the recording material transport direction. Extension line LCC of straight line LC connecting NS on the recording material conveyance direction side
That is, it is configured to face the fixing member side.

When the image area IA of the recording material P (see FIG. 4) exits the nip N, the second toner image T carried on the other surface is formed.
Of the first toner image TA formed on one surface of the recording material P is also melted in the nip N because the recording material P may be pulled toward the fixing roller 15 side. Therefore, the recording material P may be pulled toward the pressure roller 16. The gap GA is the width W of the margin M1
And the surface hardness of the pressure roller 16 is lower than the surface hardness of the fixing roller 15 and only the margin portion M1 exits from the nip N, the margin portion M1 is not covered by the pressure roller 16.
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 wind around the surface of the pressure roller 16 when the recording material P is pulled toward the pressure roller 16. Moreover, since the pressing member side separating means 19A is located apart from the surface of the pressure roller 16 which has low surface hardness and is therefore easily scratched, the surface is not scratched.

Further, on the surface of the fixing roller 15 or a fixing member side separating means 22A composed of a sheet-like separating member or the like.
Even if the recording material P exiting the nip N adheres to the surface of the fixing roller 15, the recording material P is in contact with the recording material P.
Is immediately separated from the surface of the fixing roller 15 by the fixing member side separating means 22A, and the recording material P is not wound around the surface of the fixing roller 15. 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, it is possible to prevent the surface from being scratched. As described above, by bringing the fixing member side separating means 22A into contact with the surface of the fixing roller 15, it is possible to reliably prevent the recording material P from being wound around the fixing roller 15. The recording material P exiting from the nip N is conveyed while being guided by the pressing member side separating means 19A and the guide member 21A arranged above it.

As described above, the recording material P is the fixing roller 15
And the pressure roller 16 can be prevented from being wound around, and the surfaces of both rollers 15 and 16 can be prevented from being scratched. The first surface formed on each surface of the recording material P after passing through the nip N.
Also, it is possible to prevent the quality of the second toner image from being deteriorated.

A more specific structure of the fixing device 4 shown in FIG. 9 will be described as an example. As the fixing roller 15, for example, the outer circumference of an iron hollow roller having an outer diameter of 40 mm and a wall thickness of 0.6 mm. It is possible to use one whose surface is coated with a release layer made of a fluororesin. The pressure roller 16
For example, a foamed silicone rubber layer having a thickness of 5 mm formed on an aluminum cored bar having an outer diameter of 40 mm, and a PFA tube having a thickness of 30 μm covered on the outer peripheral surface thereof can be used. In this configuration, the fixing roller 1
Since the elastic layer is not provided on the fixing roller 5, the heat capacity of the fixing roller 15 is reduced, and the rising time from the power-on to the temperature at which the fixing roller 15 can be fixed can be shortened.

The constitution in which the hardness of the fixing member on the surface side is made larger than the hardness of the pressing member on the surface side can be applied even when the fixing member is a fixing belt, and an example thereof is shown in FIG. The basic idea of the fixing device 4 shown in FIG.
Since it is the same as the fixing device shown in,
The fixing member heated by the heaters 17A and 17B is composed of an endless fixing belt 15A that is wound around a plurality of guide members, in this example, the facing roller 15B and the tension roller 15C and rotates in the direction of arrow B. The pressure member that comes into pressure contact with is composed of at least one guide member via the fixing belt 15A, in the example of FIG. 10, a pressure roller 16 that comes into pressure contact with the opposing roller 15B and rotates in the direction of the arrow. 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 facing roller 15B.

The recording material P carrying the second toner image T to be fixed is formed by pressing the fixing belt 15A and the pressure roller 16 so that the second toner image T faces the fixing belt 15A. After passing through the nip N, the second toner image T is fixed on the recording material P by the action of heat and pressure.

At this time, when only the margin portion M1 on the front end side of the recording material P to be conveyed has exited the nip N by the above-mentioned structure, the margin portion M1 on the front end side conveys the recording material in the nip N. The straight line LC connecting the downstream end NE in the direction and the upstream end NS of the nip N in the recording material conveyance direction is directed toward the fixing member side including the fixing belt 15A with respect to the extension line LCC on the recording material conveyance direction side.

As shown by the arrow A, the first toner image TA which has already been fixed is formed on one surface of the recording material P entering the nip N. Then, the pressure member side separating means 19A for separating the recording material P coming out of the nip N from the surface of the pressure member composed of the pressure roller 16 is arranged in a non-contact state with respect to the surface of the pressure member. The gap GA between the downstream end NE of the nip N in the recording material conveying direction and the tip of the pressing member side separating means 19A facing the pressing member is a margin portion on the leading end side of the recording material P in the conveying direction. The width W of M1 in the transport direction is set to be smaller, and with this configuration, the recording material P is set in the same manner as in the fixing device shown in FIG.
Can be prevented from being wound around the pressure roller 16, and the pressure roller having a low surface hardness can be prevented from being damaged by the pressure member side separating means 19A. The fixing belt 15
The fixing member side separating means 22A that is in contact with the surface of A can prevent the recording material P from winding around the fixing belt 15A. The recording material P exiting the nip N is guided and conveyed by the pressing member side separating means 19A and the guide member 21A.

Also in the case of the fixing device 4 shown in FIGS. 9 and 10, when only the leading end side margin M1 of the recording material P exits the nip N, the margin M1 is located closer to the fixing member than the extension line LCC. As shown, the downstream end NE of the nip N in the recording material conveyance direction
The Asker C hardness of the surface of the fixing member is set higher than the Asker C hardness of the surface of the pressing member at the downstream end NE of the nip N in the recording material conveying direction. Moreover, as described above, the fixing member side separating means 22A for separating the recording material P exiting the nip N from the fixing member is provided, and the tip end of the fixing member side separating means 22A contacts the surface of the fixing member. Since they are in contact with each other, it is possible to effectively prevent the recording material from winding around the fixing member. At that time, since the hardness of the surface of the fixing member is high, the fixing member-side separating means 22A which comes into contact with the fixing member is separated.
This can prevent the surface of the fixing member from being scratched.

By the way, in each of the above-described embodiments, the gap G between the tip of the fixing member side separating means 19 which is located apart from the fixing member and the downstream end NE of the nip N in the recording material conveying direction. Is set to be smaller than the width W of the margin M1 on the leading end side of the recording material P in the transport direction.
The tip of the fixing member side separating means 19 is located close to the surface of the fixing member. In order to properly arrange the fixing member side separating means 19 in such a position, it is advantageous to adopt the following configuration.

FIG. 11 shows an example of the structure for positioning the fixing member side separating means 19 composed of the sheet-shaped separating member 20 with respect to the fixing roller 15 shown in FIGS. As shown in FIG. 11, a gap holding member 29 is fixed to each end portion of the separating member 20 in the longitudinal direction, that is, each end portion of the fixing member side separating means in the direction orthogonal to the conveying direction of the recording material. Each gap holding member 29
Are supported by a support member 31 via screws 30. The support member 31 is pressed toward the surface of the fixing roller 15 by a pressing member 32 including a compression spring. 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 are in contact with 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. This allows
The above-described gap G and the gap between the front surface of the fixing roller 15 and the front end of the fixing member-side separating means 19 facing the recording material passage area PB, that is, the recording material passage area PB, are properly maintained.

Although the position of the surface of the fixing roller 15 is not constant due to the thermal expansion of the roller and the effect of eccentricity, the gap G is fixed by positioning the fixing member side separating means 19 as described above. The member-side separating means 19 can always be kept substantially constant over the entire longitudinal direction. Moreover, 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 fixes. The toner image is not affected by the contact with the surface of the roller 15.

Even when the fixing member is 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. It is possible to properly regulate the gap G and the gap G between the fixing member side separating means 19 and the surface of the fixing belt 15A.

As described above, a gap holding member is provided at each end of the fixing member side separating means in the direction orthogonal to the recording material conveying direction, and both gap holding members are brought into contact with the recording material non-passing area of the fixing member. By bringing them into contact with each other and maintaining a gap between the tip of the fixing member side separating means and the surface of the fixing member,
It becomes possible to easily position the tip of the fixing member side separating means close to the fixing member and correctly position it.

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, FIGS. The configuration shown can be adopted. In this case, the pressure roller 16 shown in FIG. 6, FIG. 8, FIG. 9 or FIG. 10 is arranged instead of the fixing roller 15 shown in FIG. 11 and FIG. Thus, a gap holding member is provided at each end of the pressure member side separating means in the 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 pressing member side separating means and the surface of the pressing member can be maintained, and thereby the pressing member side separating means can be properly positioned close to the surface of the pressing member. it can. Moreover, since the gap holding member is in contact with the recording material non-passing area of the pressing member, it is possible to prevent the defect that the recording material passing area of the pressing member is damaged.

By the way, the fixing member side separating means 19 and the pressing member side separating means 19 separated from the fixing member or the pressure member.
As A, in addition to the sheet-shaped separating members 20 and 20A, 1
Separation means composed of a separation claw made of a single plate material, separation means composed of a plurality of separation claws arranged along the surface of the fixing member or the pressing member, and the like can be appropriately used. Since the separating means 19 and the pressure member side separating means 19A are arranged in non-contact with the fixing member or the pressure member, the respective separating means 19, 19 are provided.
As A, it is possible to use one separating member made of a sheet-like or plate material as in the illustrated example. When the separating means is in contact with the surface of the fixing member or the pressing member, the separating means composed of a plurality of separating claws is used, and the contact pressure between each separating claw and the fixing member or the pressing member is adjusted by the spring. Therefore, it is necessary to make all the contact pressures uniform. However, the fixing member side separating means 19 and the pressing member side separating means 19A of this example are not in contact with the fixing member or the pressing member. Therefore, it is not necessary to adjust the contact pressure, and the fixing member side separating means 19 and the pressurizing member side separating means 19A constituted by one separating member can be adopted. By configuring each separating means 19 and 19A in this way, it is possible to reduce the number of parts and the cost thereof. Also,
Since it is not necessary to provide a spring for adjusting the contact pressure at which the fixing member-side separating means 19 and the pressing member-side separating means 19A come into contact with the fixing member or the pressing member, the separating means 19 and 19A are used as guides for recording materials. It can also be formed integrally with a member or a casing (not shown) of the fixing device.

Further, as shown in FIG. 11, when one or more openings 36 for ventilation are formed in one separating member 20 which constitutes the fixing member side separating means 19, the recording heated at the nip N is performed. Water vapor emitted from the material P can be allowed to escape, for example, upward through the opening 36, whereby it is possible to prevent the problem that the water vapor is condensed on the recording material P and the quality thereof is deteriorated. Similarly, by forming one or a plurality of openings for ventilation in one separating member 20A that constitutes the pressing member side separating means 19A, it is possible to allow water vapor emitted from the recording material to escape through the openings.

When the fixing member side separating means 19 and the pressing member side separating means 19A are constituted by the sheet-like separating members 20 and 20A as in the illustrated example, especially when the thickness is thin, these separating members are separated. Due to the corrugation caused by thermal expansion of itself and the deformation caused by the recording material coming into contact with the separating members 20 and 20A, the distance between the separating members 20 and 20A and the fixing member or the pressing member is not uniform in the longitudinal direction of the separating member. It may become uniform. Therefore, the fixing member side separating means 1
9 and the pressurizing member side separating means 19A are constituted by sheet-like separating members 20 and 20A, the separating member 2
It is desirable to provide a tension applying means for pulling 0 and 20A in a direction orthogonal to the recording material conveyance direction. This can prevent the above-mentioned problems from occurring.

The separation member 20 shown in FIG. 11 has its longitudinal ends fixed to the gap holding member 29, and both gap holding members 29 are supported by the support member 31 via the screws 30. , By turning the screw 30, the separation member 20 can be pulled in the direction of the arrow and a tension can be applied to the separation member 20 to keep the separation member 20 flat,
The distance between the separating member 20 and the fixing roller 15 can be kept constant. Thus, the screw 30 constitutes an example of a tension applying means for pulling the separating member. The tension applying means for pulling the separating member 20A of the pressing member side separating means 19A can be configured in the same manner.

As the sheet-shaped separating 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, as the separating members 20 and 20A, the thickness is 0.2 m.
When a metal sheet or a metal plate having a length of m or more is used, its rigidity is increased. Therefore, the spacing between the separating member and the fixing member or the pressing member should be kept constant even without providing the above tension applying means. Is possible.

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 wrapping around. However, when this configuration is adopted, the oil adheres to the recording material and the recording material becomes dirty, and the maintenance for oil application becomes complicated, and the application member for oil application is required, and the cost of the fixing device is reduced. We cannot avoid the rising drawbacks.

Therefore, when a wax-containing toner is used as the toner and the toner image is formed by the toner containing at least the resin, the colorant, and the wax, the so-called oil-less structure without applying the release agent is omitted. It is possible to eliminate the above-mentioned problems.

The above-described structures can be widely applied to fixing devices other than the above-mentioned types. For example, in the fixing device 4 shown in FIGS. 5, 8 and 10, the fixing belt 1
Although guide rollers, that is, the opposing roller 15B and the tension roller 15C are used as the guide member around which 5A is wound, in the fixing device 4 shown in FIG. 13, two guide rollers 33 and 34 and a heater 35 are provided. Guide members are used, and the fixing belt 15A is wound around these guide members. Although not shown in the figure, the heater 35 is arranged between a pair of electrodes and the electrodes,
The fixing belt 15A has a resistor in contact with the inner surface thereof, and the resistor is heated by supplying a current to the resistor, thereby heating the fixing belt 15A. Even in such a fixing device, as shown in FIGS.
Also, the configuration described above with reference to FIG. 10 can be employed.

Further, as described above, the pressure member may be composed of a pressure belt wound around a plurality of guide members and driven to rotate. Also in this case, when the pressure belt portion wound around the guide member abuts the fixing member to form the nip,
The Asker C hardness of the surface of the pressure belt is the hardness measured on the surface of the pressure belt portion wound around the guide member. The Asker C hardness value described in this specification is a value obtained by directly measuring the surface hardness of a roller or a belt using an Asker C hardness meter.

[0104]

According to the inventions according to claims 1 and 4,
It is possible to prevent the recording material from winding around the fixing member,
The fixing member side separating means can prevent a defect that the surface of the fixing member is scratched.

According to each of the fifth and eighth aspects of the present invention, it is possible to prevent the recording material from being wound around the pressure member and to prevent the surface of the pressure member from being scratched by the pressure member side separating means. It can be prevented.

According to the invention of claim 6, the recording material can be prevented from being wound around the fixing member and the pressing member, and the fixing member and the pressing member can be separated by the fixing member side separating means and the pressing member side separating means. It is possible to prevent a defect that the surface of the member is scratched.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view showing an example of an image forming apparatus.

FIG. 2 is a cross-sectional view showing an example of a fixing device.

FIG. 3 is an enlarged explanatory diagram of the fixing device shown in FIG.

FIG. 4 is a diagram illustrating a margin portion of a recording material.

FIG. 5 is a cross-sectional view showing another example of a fixing device.

FIG. 6 is a sectional view showing 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 sectional view showing still another example of a fixing device.

FIG. 9 is a sectional view showing still another example of the fixing device.

FIG. 10 is a sectional view showing still another example of a fixing device.

FIG. 11 is a plan view showing an example of a separation member supporting device.

FIG. 12 is a perspective view showing a state where the gap holding member shown in FIG. 11 is in contact with the surface of the fixing roller.

FIG. 13 is an explanatory diagram showing still another example of the fixing device.

[Explanation of symbols]

4 fixing device 19 Fixing member side separating means 19A Pressure member side separating means 20 Separation member 20A separation member 22 Pressure member side separating means 22A Fixing member side separating means 29 Gap holding member 36 openings G gap GA gap LA straight line LB straight line LC straight line LAA extension line LBB extension line LCC extension line M1 margin N Nip NE Recording material conveyance direction downstream end NS Recording material conveyance direction upstream end P recording material PA recording material non-passage area T toner image W width

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kiyoshi Oshima             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Jun Nakato             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Takashi Fujita             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Satoshi Baba             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Jun Yura             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh (72) Inventor Hirokazu Ikegami             1-3-3 Nakamagome, Ota-ku, Tokyo Stocks             Company Ricoh F-term (reference) 2H033 AA16 BA10 BA11 BA12 BA16                       BA20 BA21 BB13 BB14 BB30                       BB33 CA22                 3J103 AA02 AA24 AA41 BA03 BA41                       BA43 FA07 GA02 GA57 GA58                       GA60 HA03 HA12

Claims (20)

[Claims] 1. A recording material having a fixing member to be heated and a pressurizing member in pressure contact with the fixing member, the recording material carrying a toner image to be fixed is oriented with the toner image in contact with the fixing member. In a fixing device for fixing the toner image on the recording material by the action of heat and pressure by passing through a nip formed by the pressure contact between the fixing member and the pressure member, the front side of the conveying direction of the recording material to be conveyed. When only the margin part of the nip exits the nip, the margin part on the leading end side is more than a straight line extending from the downstream end of the nip in the recording material conveyance direction to the upstream end of the nip in the recording material conveyance direction. The fixing member side separating means for separating the recording material exiting the nip from the surface of the fixing member is arranged in a non-contact state with respect to the surface of the fixing member. , Under the nip recording material conveyance direction The gap between the side edge and the leading end of the fixing member side separating means, the margins of the conveying direction leading end side of the recording material, the fixing device being characterized in that set to be smaller than the width in the conveyance direction. 2. The Asker C hardness of the surface of the pressure member at the downstream end of the nip in the recording material conveying direction is set higher than the Asker C hardness of the surface of the fixing member at the downstream end in the recording material conveying direction of the nip. The fixing device according to claim 1. 3. A pressure member side separating means for separating the recording material exiting the nip from the surface of the pressure member,
3. The fixing device according to claim 1, wherein the tip of the pressure member side separating means is brought into contact with the surface of the pressure member. 4. A recording material having a fixing member to be heated and a pressurizing member in pressure contact with the fixing member, the recording material carrying a toner image to be fixed is oriented with the toner image in contact with the fixing member. In a fixing device for fixing the toner image on the recording material by the action of heat and pressure by passing through a nip formed by the pressure contact between the fixing member and the pressure member, the front side of the conveying direction of the recording material to be conveyed. When only the margin portion of the nip exits the nip, the margin portion on the leading end side extends in the direction of the extension line of the straight 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. The fixing member side separating means for separating the recording material exiting the nip from the surface of the fixing member is arranged so as to be substantially facing, and is arranged in a non-contact state with respect to the surface of the fixing member. End of recording material in the recording material transport direction Gap, said margin portion of the conveying direction leading end side of the recording material, the fixing device being characterized in that set to be smaller than the width in the conveying direction between the tip of the fixing member side separation means. 5. A recording material having a fixing member to be heated and a pressurizing member in pressure contact with the fixing member, the recording material carrying a toner image to be fixed is oriented with the toner image in contact with the fixing member. In a fixing device for fixing the toner image on the recording material by the action of heat and pressure by passing through a nip formed by the pressure contact between the fixing member and the pressure member, the front side of the conveying direction of the recording material to be conveyed. When only the margin portion of the nip exits the nip, the margin portion on the leading end side extends in the direction of the extension line of the straight 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. The pressure member side separating means for separating the recording material exiting the nip from the surface of the pressure member is arranged in a non-contact state with respect to the surface of the pressure member. , Downstream end of the nip in the recording material conveying direction The gap between the tip of the pressing member side separation means, the margins of the conveying direction leading end side of the recording material, the fixing device being characterized in that set to be smaller than the width in the conveyance direction. 6. A recording material having a fixing member to be heated and a pressurizing member in pressure contact with the fixing member, the recording material carrying a toner image to be fixed is oriented with the toner image in contact with the fixing member. In a fixing device for fixing the toner image on the recording material by the action of heat and pressure by passing through a nip formed by the pressure contact between the fixing member and the pressure member, the front side of the conveying direction of the recording material to be conveyed. When only the margin part of the nip exits the nip, the margin part on the leading end side extends in the direction of an extension line of a straight 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. The fixing member side separating means for separating the recording material exiting the nip from the surface of the fixing member is arranged in a substantially non-contact manner, and is arranged in a non-contact state with respect to the surface of the fixing member. End of recording material in the recording material transport direction The gap between the tip of the fixing member side separation means, the margin of the conveying direction leading end side of the recording material, is set smaller than the width in the conveyance direction,
Further, the pressure member side separating means for separating the recording material coming out of the nip from the surface of the pressure member is arranged in a non-contact state with respect to the surface of the pressure member, and the recording material of the nip is conveyed. Fixing, characterized in that the gap between the downstream end in the direction and the tip of the pressing member side separating means is set to be smaller than the width of the margin portion on the leading end side in the carrying direction of the recording material in the carrying direction. apparatus. 7. The Asker C hardness of the surface of the fixing member at the downstream end of the nip in the recording material conveying direction and the Asker C hardness of the surface of the pressing member at the downstream end of the nip in the recording material conveying direction are substantially equal. The fixing device according to claim 4, wherein the fixing device is set. 8. A recording material having a fixing member to be heated and a pressurizing member in pressure contact with the fixing member, the recording material carrying a toner image to be fixed is oriented with the toner image in contact with the fixing member. In a fixing device for fixing the toner image on the recording material by the action of heat and pressure by passing through a nip formed by the pressure contact between the fixing member and the pressure member, the front side of the conveying direction of the recording material to be conveyed. When only the margin of the nip exits the nip, the margin on the leading end side is fixed more than the straight line extending from the downstream end of the nip in the recording material conveyance direction to the upstream end of the nip in the recording material conveyance direction. A pressure member side separating means for separating the recording material exiting the nip from the surface of the pressure member in a non-contact state with the surface of the pressure member. Place it below the nip recording material conveyance direction The gap between the side edge and the leading end of the pressing member side separation means, the margins of the conveying direction leading end side of the recording material, the fixing device being characterized in that set to be smaller than the width in the conveyance direction. 9. The Asker C hardness of the surface of the fixing member at the downstream end of the nip in the recording material conveying direction is set higher than the Asker C hardness of the surface of the pressing member at the downstream end in the recording material conveying direction of the nip. The fixing device according to claim 8. 10. A fixing member side separating means for separating the recording material exiting the nip from the fixing member, wherein the tip of the fixing member side separating means is brought into contact with the surface of the fixing member. The fixing device according to 8 or 9. 11. A gap holding member is provided at each end of the fixing member side separating means in a direction orthogonal to the recording material conveyance direction, and the gap holding member is brought into contact with a recording material non-passing region of the fixing member. The fixing device according to any one of claims 1 to 4, 6 and 7, which maintains a gap between the tip of the fixing member side separating means and the surface of the fixing member. 12. A gap holding member is provided at each end of the pressing member side separating means in a direction orthogonal to the recording material conveyance direction, and the gap holding member is provided in a recording material non-passing area of the pressing member. 5. Abutment is performed to maintain a gap between the tip of the pressure member side separating means and the surface of the pressure member.
The fixing device according to any of 0. 13. The fixing device according to claim 1, wherein the fixing member side separating means is composed of one separating member. 14. The pressurizing member-side separating means is constituted by one separating member.
2. The fixing device according to any one of 2. 15. An opening for ventilation is formed in a separating member which constitutes the fixing member side separating means.
The fixing device described in 1. 16. An opening for ventilation is formed in a separating member which constitutes the pressing member side separating means.
The fixing device described in 1. 17. The fixing member side separating means is constituted by a sheet-like separating member, and a tension applying means for pulling the separating member in a direction orthogonal to a recording material conveying direction is provided. The fixing device according to any one of 6, 6, 7, 11, 13 and 15. 18. The pressure-apparatus-side separating means is constituted by a sheet-like separating member, and a tension applying means for pulling the separating member in a direction orthogonal to the recording material conveying direction is provided. The fixing device according to any one of 10, 12, 14 and 16. 19. The fixing device according to claim 1, wherein the toner image is formed of a toner containing at least a resin, a colorant and a wax. 20. An image forming apparatus comprising the fixing device according to any one of claims 1 to 19.