JP2003330310A - Fixing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To peel a fixed recording medium from a fixing belt without using a separation claw, in a fixing device using a fixing belt. <P>SOLUTION: The fixing belt 14 is stretched between a heat roller 11 and a wrap roller 12, and the heat roller 13 is pressed to the wrap roller 12 via the fixing belt 14. In an area which is downstream from a fixing nip N between a pressure roller 13 and the fixing belt 14, an auxiliary roller 15 is pressed to the wrap roller 12 by a pressing mechanism, not shown. By pressing the auxiliary roller 15 to the wrap roller 12 and compressing the roller 15 into the wrap roller 12, the surface of the contact portion of the wrap roller 12 is dented. As a result, the fixing belt 14 is separated from the surface of the wrap roller 12 between the fixing nip N and the contact portion of the auxiliary roller 15 and also a curved part R with a large curvature (small curvature radius) is formed in the belt 14. The recording medium P passed through the fixing nip N is thus surely peeled from the fixing belt 14, on the curved part R. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fixing device for an image forming apparatus such as a copying machine or a printer, and more particularly to a device for separating a recording medium from the fixing belt in the fixing device using the fixing belt.

[0002]

2. Description of the Related Art A fixing device of an image forming apparatus includes one using a fixing roller and one using a fixing belt. As shown in FIG. 4, for example, the fixing roller is composed of a heating roller 101 having a heat source 103 inside and a pressure roller 102.
In the fixing nip portion N where 1 and the pressure roller 102 are in pressure contact with each other, the recording medium P having the toner image T formed on the surface thereof is oriented in the direction in which the toner image T faces the heating roller 101 (or in the opposite direction). ), The toner image T on the recording medium P is heated and melted, and at the same time, the melted toner image T is pressed and fixed to the recording medium P.

Further, in the case of using a fixing belt, as shown in FIG. 5, for example, the fixing belt 11 is provided between a heating roller 111 having a heat source 115 inside and a winding roller 112.
3 is installed, and the pressure roller 1 is attached to the winding roller 112.
The fixing belt 113 receives heat from the heating roller 111 and is heated to a temperature suitable for fixing. At the fixing nip portion N where the fixing belt 113 and the pressure roller 114 are in pressure contact with each other, the recording medium P having the toner image T formed on the surface thereof, the toner image T is pressed by the pressure roller 114.
The toner image T on the recording medium is heated and melted, and at the same time, the molten toner image T is pressed and fixed to the recording medium P.

In the case of using the above-mentioned fixing roller or the case of using the fixing belt, there is a possibility that the recording medium subjected to the fixing process may be stuck to the heating roller or the pressure roller (hereinafter referred to as the fixing roller) and jam. Therefore, some of them include a separating means for separating the recording medium from the fixing roller, and some of the separating means peel the recording medium by bringing the separating claw 120 into contact with the downstream side of the fixing roller in the recording medium conveying direction.

[0005]

However, in the case of using the above-mentioned separation claw, the surface of the fixing roller is worn and deteriorated because the separation claw is in constant contact with the surface of the fixing roller. There is a configuration in which the separation claw is brought into contact with the surface of the fixing roller only when it is moved, and in other cases the separation claw is moved to the retracted position away from the surface of the fixing roller. There is a disadvantage that the structure of the fixing device is complicated because a mechanism is provided and it is necessary to control the separation claw to be moved during the fixing process and at other times.

Further, a structure has been proposed in which the separation claw is arranged in a non-contact state with the surface of the fixing roller, but there is a disadvantage that the separation of the recording medium becomes uncertain. This invention
The object is to solve the above problems.

[0007]

This invention is to solve the above-mentioned problems, and the invention of claim 1 provides a first roller and a second roller.
A fixing device including a roller, a fixing belt that is provided between the first roller and the second roller, and a third roller that contacts the second roller via the fixing belt to form a fixing nip portion. In the fixing device, a fixing portion forming means for forming a bending portion having a curvature larger than the curvature of the outer peripheral surface of the second roller on the fixing belt is provided downstream of the fixing nip portion in the recording medium conveying direction. Is.

Then, the bending portion forming means separates the fixing belt from the outer peripheral surface of the second roller on the downstream side of the fixing nip portion in the recording medium conveying direction, so that the fixing belt is provided with the second portion.
A bending portion having a curvature larger than that of the outer peripheral surface of the roller is formed.

The bending portion forming means may be composed of a fourth roller having a diameter smaller than that of the second roller arranged on the downstream side of the fixing nip portion in the recording medium conveying direction.

The fourth roller of the bending portion forming means is movably supported between a contact position in contact with the second roller through the fixing belt and a separation position in which the second roller is separated from the fixing belt. At the time of execution, it is set to the contact position and is driven by the fixing belt to rotate, and the second
A bending portion having a curvature larger than that of the outer peripheral surface of the roller is formed.

Further, the fourth roller is configured to be connectable to and detachable from the rotation drive mechanism, and is connected to the rotation drive mechanism when set to a contact position where it contacts the second roller via the fixing belt. It is also possible to rotate at a peripheral speed lower than the moving speed of the fixing belt and form a bending portion having a curvature larger than the curvature of the outer peripheral surface of the second roller on the fixing belt.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a cross-sectional view showing a configuration of a main part of a fixing device using a fixing belt. In FIG. 1, 11 is a heating roller that is a first roller, 12 is a winding roller that is a second roller, 13 is a pressure roller that is a third roller, and 14 is a bridge between the heating roller 11 and the winding roller 12. The formed fixing belt 15 is an auxiliary roller which is a fourth roller.

The heating roller 11 is constructed by coating a surface layer of a cylindrical core metal 11a made of a metal material such as aluminum with a fluororesin coating 11c, for example.
A heater lamp 16 as a heat source is provided inside the heating roller 11 heated by the heater lamp 16.
Is transferred to the fixing belt 14 and heats the fixing belt 14. The surface temperature of the fixing belt 14 is detected by a temperature sensor (not shown), and the heater lamp 16 is blinked so as to be maintained in a predetermined temperature range suitable for fixing, and temperature control is executed.

The winding roller 12 has a heat-resistant synthetic rubber elastic body layer 12b thickly formed, for example, on the order of 2 mm on a cylindrical core metal 12a made of a metal material such as aluminum. Fluororesin coating 12c on the surface
The synthetic rubber elastic body layer 12b is easily elastically deformed by pressure from the outside. Synthetic rubber elastic layer 12
Fluorine rubber, silicone rubber or the like can be used for b.

In the pressure roller 13, a heat-resistant synthetic resin elastic body layer 13b is formed on a cylindrical core metal 13a made of a metal material such as aluminum, and the surface layer thereof is coated with, for example, a fluorine resin coating 13c. Is configured. The pressure roller 13 is biased toward the winding roller 12 with a fixing belt 14 interposed by a biasing mechanism (not shown), and a fixing nip portion N is formed between the pressure roller 13 and the fixing belt 14. Has been formed.

The heating roller 11 and the winding roller 1 described above.
2. The pressure roller 13 is rotatably supported, and here, the winding roller 12 is coupled to a drive mechanism (not shown) to rotate and drive the heating roller 11 and the pressure roller 13. However, the heating roller 11 may be rotationally driven, and the winding roller 12 and the pressure roller 13 may be driven. Alternatively, the pressure roller 13 may be rotationally driven and the heating roller 11 and the winding roller 12 may be driven.

The fixing belt 14 is made of a heat-resistant synthetic resin such as polyimide, and is installed between the heating roller 11 and the winding roller 12 with an appropriate tension, and the surfaces of the heating roller 11 and the winding roller 12 are covered. It is in frictional contact with and can move as the heating roller 11 and the winding roller 12 rotate.

Auxiliary roller 15 constituting the flexure forming means.
Is urged toward the wrapping roller 12 via the fixing belt 14 by a urging mechanism (not shown) at the downstream side of the fixing nip portion N between the pressure roller 13 and the fixing belt 14. The surface of the hanging roller 12 is in frictional contact with the fixing belt 14, and is configured to be rotatable following the movement of the fixing belt 14.

Since the diameter of the auxiliary roller 15 is sufficiently smaller than the diameter of the winding roller 12, by pressing the auxiliary roller 15 toward the winding roller 12,
The surface of the contact portion of the winding roller 12 is a synthetic rubber elastic layer 12b.
Is elastically deformed and dented, and the fixing belt 14 on the surface of the winding roller 12 is separated from the surface of the winding roller 12 between the fixing nip portion N and the contact portion of the auxiliary roller 15 and has a large curvature (having a radius of curvature). A (small) flexure, or bend R, is formed.

The auxiliary roller 15 is the fixing belt 14
In order to suppress the deterioration of the toner, the position is set to urge the winding roller 12 through the fixing belt 14 only when the fixing process is performed, and when the fixing process is not performed, the retracted position (non-energized position) is set. An urging mechanism (not shown) may be controlled so that the urging mechanism moves to a position where the urging mechanism moves to or slightly contacts.

The urging mechanism (not shown) may be constructed so that the urging force of the auxiliary roller 15 can be adjusted according to the situation. By adjusting the magnitude of the urging force, the size of the curved portion R of the fixing belt 14 can be adjusted, and the recording medium P can be reliably peeled from the fixing belt 14.

In the above structure, when the winding roller 12 is connected to a drive mechanism (not shown) and rotated in the direction of arrow a in FIG. 1, the heating roller 11 and the fixing belt 14 are also driven in the direction of arrow a. Further, the pressure roller 13 biased toward the winding roller 12 via the fixing belt 14 also rotates in the direction of the arrow a, and the winding roller 1 passes through the fixing belt 14.
The auxiliary roller 15 biased toward 2 also rotates in the direction of arrow a.

Recording medium P having a toner image T formed on its surface
When the toner image T is conveyed in the direction of the arrow b in the direction of facing the fixing belt 14 and passes through the fixing nip portion N, the toner image T on the recording medium P is melted by the heat of the fixing belt 14, The molten toner is pressed against the recording medium P by the pressure roller 13 and fixed.

The recording medium P having passed through the fixing nip portion N and subjected to the fixing process moves to the downstream side of the fixing nip portion N together with the fixing belt 14. On the downstream side of the fixing nip portion N, the surface of the winding roller 12 is elastically deformed by the urging force of the auxiliary roller 15, the fixing belt 14 is separated from the surface of the winding roller 12, and the fixing belt 14 has a large curvature (small curvature). Since the curved portion R having a radius of curvature is formed, even when the recording medium P is attached to the fixing belt 14, the recording medium P is naturally separated from the fixing belt 14 and is conveyed toward a sheet discharging unit (not shown). To be done.

In the above-described embodiment, the auxiliary roller 15 is biased to the winding roller 12 via the fixing belt 14, and the auxiliary roller 15 is rotated by the frictional coupling force with the fixing belt 14. Therefore, the surface speed of the fixing belt 14 and the surface speed of the auxiliary roller 15 are the same unless the slip between the contact surfaces is taken into consideration. Therefore, the size of the curved portion R of the fixing belt 14 is mainly based on the elastic deformation of the surface of the winding roller 12 due to the bias of the auxiliary roller 15.

However, in order to form the curved portion R on the fixing belt 14, if the auxiliary roller 15 is connected to an independent driving mechanism and the surface speed of the auxiliary roller 15 is made lower than the surface speed of the fixing belt 14, the fixing is performed. The belt 14 is loosened to form the curved portion R. The size of the curved portion R can be adjusted by setting the surface speed of the auxiliary roller 15, that is, the rotation speed.

In this method, slippage occurs between the fixing belt 14 and the auxiliary roller 15, and the fixing belt 14 deteriorates due to friction. Therefore, when it is not necessary to adjust the size of the curved portion R, the fixing belt 14 is not necessary. It is advisable to set the surface speed of 1 and the surface speed of the auxiliary roller 15 at substantially the same speed. In this case, the auxiliary roller 15 may be separated from the independent drive mechanism, and the auxiliary roller 15 described above may be rotated by the frictional coupling force with the fixing belt 14.

The auxiliary roller 15 is the fixing belt 1
Although it has been described that the curved portion R is formed on the No. 4,
Since the auxiliary roller 15 always contacts the fixing belt 14 during the fixing process, it should also be used as an application roller for applying a release agent to the surface of the fixing belt 14 or as a cleaning roller for cleaning the surface of the fixing belt 14. You can also

Next, the timing of forming the curved portion R on the fixing belt 14 by urging the auxiliary roller 15 to the winding roller 12 via the fixing belt 14 will be described. Curved part R
Is formed at the timing when the leading end of the recording medium P in the conveyance direction reaches the fixing nip portion N. Thereby, the deterioration of the fixing belt 14 can be suppressed to the minimum.

FIG. 2 is a diagram for explaining the position where the curved portion R is formed on the fixing belt 14 and the position where the sensor 18 for detecting the leading end of the recording medium in the conveying direction is arranged. FIG.
FIG. 6 is a diagram for explaining the timing of forming the curved portion R on the fixing belt 14 by the biasing of the auxiliary roller 15 after the detection of the leading end of the recording medium P in the conveyance direction by the method.

As shown in FIG. 2, the sensor 18 is composed of a contact member 18a and a photocoupler 18b for detecting the movement of the contact member 18a. The contact member 18a is located on the recording medium conveying path toward the fixing nip portion N. Is arranged as.

Since the position where the curved portion R is formed on the fixing belt 14 is not a position that can be strictly defined, here, the position M (fixing nip portion N) where the winding roller 12 and the pressure roller 13 contact each other. The same) as the formation start point of the curved portion R.

When the distance between the position M and the contact member 18a of the sensor 18 is L (m), the conveying speed of the recording medium is V (m / m).
s), the time L / V (s) from the time T1 when the sensor 18 detects the leading edge of the recording medium P in the transport direction and turns it ON.
After that, when the auxiliary roller 15 is urged toward the winding roller 12 via the fixing belt 14 to form the curved portion R on the fixing belt 14, the leading end of the recording medium P in the conveying direction passes through the fixing nip portion N. At this time, the curved portion R is formed on the fixing belt 14, and the recording medium P is separated from the fixing belt 14 by the curved portion R.

If the auxiliary roller 15 is rotationally driven by the drive source, when the auxiliary roller 15 is biased toward the winding roller 12 via the fixing belt 14,
At the same time, the auxiliary roller 15 is connected to the drive source.

In the embodiment described above, the curved portion R is formed on the fixing belt by using the auxiliary roller. However, in addition to this, a mechanism for moving the fixing belt in the direction of separating from the winding roller may be provided. The curved portion R can be formed on the fixing belt.

In such a mechanism, the fixing belt is made of a magnetic material, and a magnet is arranged at a position where the curved portion R is to be formed on the fixing belt, that is, at the downstream side of the fixing nip portion N. A mechanism for sucking the belt is proposed. In order to adjust the size of the curved portion R, when a permanent magnet is used as the magnet, the distance between the permanent magnet holding mechanism and the fixing belt may be adjustable. Further, when the electromagnet is used as the magnet, the magnitude of the current supplied to the electromagnet may be adjustable.

Further, the fixing belt is made of a synthetic resin material, and on the other hand, an air suction device is arranged at a position where the curved portion R is to be formed on the fixing belt, that is, at the downstream side of the fixing nip portion N, and the fixing belt is fixed. A suction mechanism or the like is proposed. The size of the curved portion R can be adjusted by adjusting the suction force.

Although the embodiment of the present invention has been described above, the fixing device of the embodiment of the present invention can easily separate the recording medium from the fixing belt as compared with the conventional fixing device. Therefore, the fixing process can be performed at a higher temperature than that of the conventional fixing device using the separating claw.

In the embodiment of the present invention described above,
The inventions described below are also included.

That is, the fixing device according to any one of claims 1 to 5, further comprising detection means for detecting the position of the recording medium conveyed toward the fixing nip portion, and the flexible portion formation based on the detection result of the detection means. A fixing device characterized by operating means.

In the fixing device according to any one of claims 1 to 5, the detecting means determines the time when the recording medium passes through the fixing nip portion based on the arrangement position of the detecting means, the distance between the fixing nip portion and the recording medium conveying speed. A fixing device characterized in that the bending portion forming means is operated in accordance with the predicted time.

[0042]

As described above, according to the present invention, the first
A roller, a second roller, a fixing belt installed between the first roller and the second roller, and a third nip portion that contacts the second roller via the fixing belt
In a fixing device including a roller, a bending portion forming unit that forms a bending portion having a curvature larger than a curvature of the outer peripheral surface of the second roller on the fixing belt is provided on the downstream side of the fixing nip portion in the recording medium conveyance direction. Therefore, the recording medium which has passed through the fixing nip portion and which has been subjected to the fixing processing is reliably separated from the fixing belt by the bending portion having a curvature larger than the curvature of the outer peripheral surface of the second roller formed on the fixing belt. No need for a separate claw placed in contact with the fixing belt.

With this structure, the surface of the fixing belt is not worn or deteriorated by the contact with the separating claw, and the contact position where the separating claw contacts the surface of the fixing roller and the retracted position apart from the surface of the fixing roller. It is possible to provide a fixing device that does not require a separating claw moving mechanism for moving the moving member to a position or a moving control device thereof, and has a simple structure and operates stably for a long period of time.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a main part of a fixing device using a fixing belt.

FIG. 2 is a diagram illustrating a position where a curved portion R is formed on a fixing belt and an arrangement position of a sensor that detects a leading end of a recording medium in a conveyance direction.

FIG. 3 is a diagram for explaining a timing of detecting a leading end of a recording medium in a conveyance direction by a sensor and a timing of forming a curved portion R on a fixing belt.

FIG. 4 is a diagram illustrating a schematic configuration of a fixing device using a conventional fixing roller.

FIG. 5 is a diagram illustrating a schematic configuration of a fixing device using a conventional fixing belt.

[Explanation of symbols]

11 Heating roller 11a core metal 11c Surface layer (fluorine resin coating) 12 Rolling roller 12a core metal 12b Heat-resistant synthetic rubber elastic layer 12c Surface layer (fluorine resin coating) 13 Pressure roller 13a core metal 13b Heat-resistant synthetic resin elastic layer 13c Surface layer (fluorine resin coating) 14 fixing belt 15 Auxiliary roller 16 heater lamp 18 sensors 18a contact member 18b Photo coupler

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shigeo Nakamura             2-3-3 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Osaka International Building Minolta Co., Ltd. (72) Inventor Toshiyuki Sahara             2-3-3 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Osaka International Building Minolta Co., Ltd. (72) Inventor Yoshinobu Hada             2-3-3 Azuchi-cho, Chuo-ku, Osaka-shi, Osaka Prefecture               Osaka International Building Minolta Co., Ltd. F-term (reference) 2H033 AA16 BA11 BA17 BA20 BA21                       BA22

Claims (5)

[Claims] 1. A first roller, a second roller, and the first roller.
A fixing belt installed between the roller and the second roller,
A fixing device including a third roller that contacts a second roller via the fixing belt to form a fixing nip portion, wherein a second roller is provided on the fixing belt downstream of the fixing nip portion in the recording medium conveyance direction. A fixing device, comprising: a bending portion forming means for forming a bending portion having a curvature larger than that of the outer peripheral surface of the fixing device. 2. The bending portion forming means separates the fixing belt from the outer peripheral surface of the second roller at the downstream side of the fixing nip portion in the recording medium conveyance direction, and the fixing belt has a curvature larger than that of the outer peripheral surface of the second roller. The fixing device according to claim 1, wherein the fixing device is a bending portion forming unit that forms a bending portion having a curvature. 3. The bending portion forming means is a fourth roller having a diameter smaller than the diameter of the second roller arranged downstream of the fixing nip portion in the recording medium conveying direction. 2. The fixing device described in 2. 4. The fourth roller is movably supported between a contact position that contacts the second roller via the fixing belt and a separation position that separates from the fixing belt. The fixing device according to claim 3, wherein the fixing device is set at a contact position and is rotated by being driven by the fixing belt, and a bending portion having a curvature larger than a curvature of an outer peripheral surface of the second roller is formed on the fixing belt. 5. The fourth roller is configured to be connectable to and disengageable from a rotation drive mechanism, and the second roller is connected to the second roller via the fixing belt.
When the contact position is set to contact the roller, it is coupled to the rotation driving mechanism, rotates at a peripheral speed lower than the moving speed of the fixing belt, and has a curvature larger than the curvature of the outer peripheral surface of the second roller on the fixing belt. The fixing device according to claim 3, wherein the fixing portion is formed.