JP2006293224A - Fixing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To shorten a time up to a fixing operation (rise time), regarding a fixing apparatus for fixing a toner image to a paper. <P>SOLUTION: The fixing apparatus 4 includes a pressure roller 5, an endless heating belt 6, a plurality of guide rollers 7 and a halogen heater 8 for heating the heating belt 6. The guide rollers 7 rotate in contact with the outer circumferential surface of the heating belt 6 and pressurize the heating belt 6 against the pressure roller 5. The outer circumferential surface of the heating belt 6 partly forms a nip N together with the pressure roller 5. The halogen heater 8 is installed at the inner peripheral side of the heating belt 6, and the halogen heater 8 directly radiates the heat to the part forming the nip N of the heating belt 6. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fixing device provided in an image forming apparatus.

Some image forming apparatuses such as printers, copiers, and facsimile machines can transfer a toner image onto a sheet. Such an image forming apparatus includes a fixing device that pressurizes and heats a sheet on which a toner image is transferred to fix the toner image on the sheet (see, for example, Patent Documents 1 and 2). .
Specifically, the fixing device includes a thin annular heating film, a pressure roller parallel to the heating film, and a metal holding member disposed inside the heating film. A heating film is sandwiched between the holding member and the pressure roller. Thereby, the heating film and the pressure roller are pressed against each other to form a nip.

In addition, a halogen lamp is disposed inside the heating film, and the radiant heat of the halogen lamp is transmitted to the heating film in the portion forming the nip via the holding member.
With the above configuration, the paper passing through the nip is pressurized and heated to fix the toner to the paper.
JP 2004-94146 A JP 2004-62053 A

  By the way, in order to cope with the on-demand of the image forming operation, the warm-up time (the time from when the power is turned off or the power saving mode to when the image forming operation can be performed) is shortened. Is required. Therefore, for the fixing device, it is necessary to shorten the time (rise time) until the toner can be fixed on the paper. Specifically, it is necessary to quickly raise the temperature of the heated film in the part where the nip is formed to a temperature at which toner can be fixed.

  However, in the case of Patent Documents 1 and 2, the holding member is disposed between the portion of the heating film forming the nip and the halogen lamp. The holding member extends over substantially the entire axial direction of the heating film, and has a large heat capacity. For this reason, it takes time to transmit the heat of the halogen lamp to the heating film in the part where the nip is formed via the holding member, and the rise time becomes long.

The present invention has been made under such a background, and an object thereof is to provide a fixing device capable of shortening the rise time.
Another object of the present invention is to provide a fixing device capable of achieving energy saving.

  In order to achieve the above-mentioned object, the invention according to claim 1 is directed to a fixing device (4) for pressurizing and heating the paper (P) on which the toner image is transferred to fix the toner image on the paper. The roller (5), the endless heating belt (6), and the outer peripheral surface of the heating belt are in rotational contact to press the heating belt toward the pressure roller, and a part of the outer peripheral surface of the heating belt is And at least two guide rollers (7) for guiding so as to form a nip (N) between them, and a heat source (8) provided on the inner peripheral surface side of the heating belt for heating the heating belt This is a fixing device.

The alphanumeric characters in parentheses indicate corresponding components in the embodiments described later. The same applies hereinafter.
According to this configuration, the member for forming the nip by pressing the heating belt toward the pressure roller is not arranged on the inner peripheral surface side of the heating belt. For this reason, heat can be transferred from the heat source to the portion of the heating belt where the nip is formed without using the member for forming the nip. Therefore, the portion of the heating belt where the nip is formed can be quickly raised to a temperature necessary for fixing the toner. As a result, the rise time of the fixing device can be shortened.

Further, since it is not necessary to heat the member for forming the nip, energy required for starting up the fixing device can be reduced, and energy saving can be achieved.
According to a second aspect of the present invention, in the fixing device according to the first aspect, the heat source can directly radiate heat to a heating belt portion forming a nip with the pressure roller.
According to this configuration, the temperature of the portion of the heating belt where the nip is formed can be increased more quickly, and the rise time of the fixing device can be further shortened.

According to a third aspect of the present invention, in the fixing device according to the first or second aspect, the heat source is a halogen heater.
According to this configuration, since the heating belt is heated using the filament having a small heat capacity, the heating belt can be rapidly heated.
According to a fourth aspect of the present invention, the heating belt is formed of a thin metal material base, the inner peripheral surface is painted black, and the outer peripheral surface is coated with fluorine. The fixing device according to any one of the above.

  According to this configuration, since the base material of the heating belt is formed of a thin metal material, the heating belt can have sufficient flexibility. Thereby, the heating belt can be elastically deformed into a shape along the pressure roller, and the heating belt can be reliably brought into contact with the pressure roller in the axial direction. Moreover, by coating the inner peripheral surface of the heating belt in black, the heat from the heat source can be efficiently received, and the temperature of the heating belt can be raised more quickly. Furthermore, since the outer peripheral surface of the heating belt is smoothed by fluorine coating, it is possible to satisfactorily prevent the toner from adhering to the heating belt.

Embodiments of the present invention will be specifically described below with reference to the drawings.
FIG. 1 is a schematic longitudinal sectional view showing a schematic configuration of a printer as an image forming apparatus including a fixing device according to an embodiment of the present invention. The present invention is not limited to a fixing device provided in a printer, but can be applied to a fixing device provided in another image forming apparatus such as a copying machine or a facsimile.

Referring to FIG. 1, a printer 1 is for forming an image based on image data on a sheet, and includes a housing 2, a photosensitive drum 3 housed in the housing 2, and a housing 2. And a fixing device 4.
The image forming operation in the printer 1 is performed as follows. That is, first, a sheet of paper P accommodated in the housing 2 is transported along the transport direction D and reaches the transfer position T where it contacts the photosensitive drum 3.

A toner image based on the image data is formed on the photosensitive drum 3 by electrophotography, and the toner image on the photosensitive drum 3 is transferred to the paper P at the transfer position T. The paper P on which the toner image is transferred at the transfer position T is conveyed to the fixing device 4 and is pressed and heated by the fixing device 4 to fix the toner image. The paper P on which the toner image is fixed is discharged out of the apparatus.
2 is a side view of the fixing device 4 of FIG. 1 as viewed from the upstream side in the transport direction D, and FIG. 3 is a cross-sectional view of a main part taken along line AA of FIG.

2 and 3, fixing device 4 includes a pressure roller 5, a heating belt 6, a guide roller 7, and a halogen heater 8 (heat source).
The pressure roller 5 includes a support shaft 51 and a roll body 52.
The support shaft 51 is a rod-like member that is elongated in the width direction W orthogonal to the transport direction D of the paper P. Both end portions of the support shaft 51 are inserted through guide insertion holes 10 and 11 formed of elongated holes formed in the frame 9 of the fixing device 4, and by urging mechanisms 12 provided at respective end portions. The heating belt 6 is biased.

  Each biasing mechanism 12 includes a lever 121, a pin 122 that rotatably supports the lever 121, and a spring 123 that applies a biasing force to the lever 121. The lever 121 is formed by a small piece that is long in the transport direction D. A pin 122 supported by the frame 9 is connected to one end of the lever 121. One end of a spring 123 is attached to the other end of the lever 121. The other end of the spring 123 is attached to the frame 9.

One lever 121 a receives one end portion of the support shaft 51, and biases one end portion of the support shaft 51 toward the heating belt 6 by the biasing force of the corresponding spring 123. Similarly, the other lever 121 b receives the other end of the support shaft 51. The other end of the support shaft 51 is urged toward the heating belt 6 by the urging force of the corresponding spring 123.
Further, the driving force of the motor 13 is applied to the support shaft 51, whereby the pressure roller 5 is rotationally driven as a driving roller in a predetermined rotational direction R1. Specifically, gears 14 and 15 are attached to the output shaft of the motor 13 and one end of the support shaft 51, and the driving force of the output shaft of the motor 13 is connected to one end of the support shaft 51 via the gears 14 and 15. It comes to be transmitted to the club.

The roll body 52 is formed in a cylindrical shape by a member having elasticity such as a sponge, and is externally fitted to an intermediate portion of the support shaft 51 so as to be integrally rotatable. The width of the roll body 52 is made wider than the width of the paper P sent to the fixing device 4.
The heating belt 6 is an endless annular member having flexibility (elasticity), and extends longer in the width direction W than the paper P sent to the fixing device 4. The heating belt 6 is formed using a thin metal material base material having a thickness of about several tens to 100 μm. Examples of the metal material include a stainless material (SUS material) and an aluminum material. A resin material such as polyimide may be used as the base material of the heating belt 6.

A black paint is applied as a heat absorbing paint on the entire inner peripheral surface of the heating belt 6. Further, at least a portion of the outer peripheral surface of the heating belt 6 that can face the paper P (in this embodiment, the entire outer peripheral surface of the heating belt 6) is coated with fluorine.
In addition, although it is preferable to use a black paint as said heat absorption paint, you may use a white or red paint.

The heating belt 6 and the pressure roller 5 are arranged in parallel and face each other vertically.
The guide roller 7 is for rotating and contacting the outer peripheral surface of the heating belt 6 to guide the rotation (driven rotation) of the heating belt 6, and is formed longer in the width direction W than the heating belt 6. The diameter is smaller than that of the belt 6.
At least two guide rollers 7 (three in this embodiment) are provided outside the heating belt 6 in the radial direction, and are arranged in parallel with the heating belt 6.

  The heating belt 6 has a predetermined distance in the circumferential direction of the heating belt 6 (in this embodiment, from a nip N formed by pressure contact between the outer circumferential surface of the heating belt 6 and the outer circumferential surface of the roll body 52 of the pressure roller 5. Every time it advances (approximately ¼ round), it contacts the corresponding guide roller 7. In this way, the heating belt 6 and each guide roller 7 are in contact with each other while avoiding the vicinity of the nip N, and the heat transferred from the halogen heater 8 to the portion of the heating belt 6 where the nip N is formed. The guide roller 7 is prevented from being taken away.

The two guide rollers 7 that are separated from the nip N by one-fourth in the circumferential direction of the heating belt 6 sandwich the heating belt 6 in the circumferential direction of the pressure roller 5. The movement around the axis of the pressure roller 5 (support shaft 51) is restricted.
Further, the heating belt 6 is sandwiched between the guide roller 7 and the pressure roller 5 that are separated from the nip N by about a half circumference in the circumferential direction of the heating belt 6. The guide roller 7 receives the heating belt 6 urged by the pressure roller 5 and presses the heating belt 6 toward the pressure roller 5 side. Accordingly, a part of the outer peripheral surface of the heating belt 6 forms the nip N with the pressure roller 5.

Each guide roller 7 is disposed along the circumferential direction of the outer peripheral surface of the heating belt 6 in a free state (a state in which no external force is received) so that the heating belt 6 has a substantially circular shape in a free state. The heating belt 6 is received.
Each guide roller 7 has a support shaft 71 and a roll body 72.
The support shaft 71 is formed longer in the width direction W than the heating belt 6, and both ends thereof are rotatably supported by the frame 9.

  A plurality of roll bodies 72 are provided at intervals in the axial direction of the support shaft 71 and are externally fitted to the corresponding support shaft 71 so as to be integrally rotatable. Of the guide roller 7, the outer peripheral surface of the roll body 72 is in contact with the outer peripheral surface of the heating belt 6. As described above, the roller 72 that is short in the axial direction in the guide roller 7 is brought into contact with the heating belt 6, thereby reducing the contact area between the guide roller 7 and the heating belt 6, and guiding from the heating belt 6. The heat transmitted to the roller 7 is reduced.

The support shaft 71 may be fixed to the frame 9 and the roll body 72 may be rotatably fitted to the support shaft 71. Further, one roll body 72 may be provided on each support shaft 71, and the length of each roll body 72 in the axial direction may be substantially equal to the length of the heating belt 6 in the axial direction.
With the above configuration, the guide roller 7 is not disposed on the inner peripheral surface side (inward in the radial direction) of the heating belt 6, and the inner peripheral surface of the heating belt 6 is not in contact with the guide roller 7. As the pressure roller 5 is driven to rotate, the heating belt 6 rotates in conjunction with a rotation direction R2 opposite to the rotation direction R1.

The halogen heater 8 is for heating the heating belt 6 by directly radiating heat to at least a portion where the nip N is formed between the heating belt 6 and the pressure roller 5. In this embodiment, the halogen heater 8 directly radiates heat over the entire circumferential direction of the heating belt 6.
Specifically, the halogen heater 8 is formed in an elongated cylindrical shape having a smaller diameter than the heating belt 6 and is disposed on the inner peripheral surface side (inward in the radial direction) of the heating belt 6. Both ends of the halogen heater 8 are fixed to the frame 9 of the fixing device 4. The filament (light emitting body) of the halogen heater 8 is disposed inside the heating belt 6 in the width direction W, and faces the portion of the heating belt 6 where the nip N is formed.

There is no member between the heating belt 6 and the halogen heater 8 that hinders the transfer of heat from the halogen heater 8 to the heating belt 6. It is directly opposed across the entire circumferential direction.
Further, a thermistor (not shown) is disposed in the vicinity of the heating belt 6, and the temperature of the heating belt 6 during image formation is maintained at a predetermined temperature (for example, about 180 ° C.). ing.

With respect to the conveyance direction D, a guide plate 16 for guiding the sheet P conveyed from the photosensitive drum to the nip N is disposed on the upstream side of the fixing device 4.
In the printer having the above schematic configuration, the fixing device 4 is driven as follows at the time of image formation. That is, when the image forming operation is started, the pressure roller 5 is rotationally driven by the driving of the motor 13 of the fixing device 4, and the heating belt 6 is driven to rotate accordingly. At this time, the heating belt 6 is heated by the halogen heater 8.

Then, the sheet P on which the toner image is transferred through the photosensitive drum passes through the guide plate 16 and is passed through the nip N, and is pressed and heated in the nip N, so that the toner image is fixed on the sheet P. Is done.
As described above, according to this embodiment, the guide roller 7 for pressing the heating belt 6 toward the pressure roller 5 to form the nip N is not arranged on the inner peripheral surface side of the heating belt 6. It has become.

  For this reason, heat can be transferred from the halogen heater 8 to the portion of the heating belt 6 where the nip N is formed without passing through the guide roller 7. Therefore, it is possible to quickly raise the temperature of the portion of the heating belt 6 where the nip N is formed to a temperature necessary for fixing the toner. As a result, the time until the toner can be fixed on the paper P (the rise time of the fixing device 4) can be shortened.

Further, since it is not necessary to heat the guide roller 7 when the heating belt 6 is heated, the energy required for starting up the fixing device 4 can be reduced and energy saving can be achieved.
Further, since the halogen heater 8 directly radiates heat to the portion of the heating belt 6 where the nip N is formed, the temperature of the portion of the heating belt 6 where the nip N is formed is further increased. Thus, the rise time of the fixing device 4 can be further shortened.

Moreover, since the heating belt 6 is heated using the halogen heater 8, that is, the heating belt 6 is heated using a filament having a small heat capacity, the heating belt 6 can be heated quickly.
Furthermore, since the base material of the heating belt 6 is formed of a thin metal material, the heating belt 6 can have sufficient flexibility. Thereby, the heating belt 6 can be elastically deformed into a shape along the pressure roller 5, and the heating belt 6 can be reliably brought into contact with the pressure roller 5 in the axial direction.

Moreover, by coating the inner peripheral surface of the heating belt 6 in black, the heat from the halogen heater 8 can be received efficiently, and the heating belt 6 can be heated more quickly. Furthermore, since the outer peripheral surface of the heating belt 6 is smoothed by fluorine coating, it is possible to satisfactorily prevent toner from adhering to the heating belt 6.
The present invention is not limited to the contents of the above embodiments, and various modifications can be made within the scope of the claims.

  For example, as shown in FIG. 4, two guide rollers 7 may be provided. In this case, one guide roller 7 is disposed at a position farther from the nip N than ¼ circumference and closer to ½ circumference with respect to one of the circumferential directions of the heating belt 6. Similarly, the other guide roller 7 is disposed at a position farther from the nip N than ¼ circumference and closer to ½ circumference with respect to the other circumferential direction of the heating belt 6.

These two guide rollers 7 sandwich the heating belt 6 in the circumferential direction of the pressure roller 5 and receive the heating belt 6 biased by the pressure roller 5.
Further, four or more guide rollers 7 may be provided.
Furthermore, instead of the halogen heater 8, a heater including xenon light or a resistance heating element heater such as a ceramic heater may be used. Further, the heating belt 6 is rotated by a motor so that the heating belt 6 becomes a driving belt, and the pressure roller 5 is driven and rotated by the rotation driving of the heating belt 6 (the pressure roller 5 is changed to a driven roller). As well).

1 is a schematic longitudinal sectional view showing a schematic configuration of a printer as an image forming apparatus including a fixing device according to an embodiment of the present invention. FIG. 2 is a side view of the fixing device of FIG. 1 as viewed from the upstream side in the conveyance direction. It is sectional drawing of the principal part in alignment with the AA of FIG. It is sectional drawing of the principal part of another embodiment of this invention.

Explanation of symbols

4 Fixing device 5 Pressure roller 6 Heating belt 7 Guide roller 8 Halogen heater (heat source)
N nip P paper

Claims (4)

In a fixing device for fixing a toner image on a paper by pressurizing and heating the paper on which the toner image is transferred,
A pressure roller;
An endless heating belt,
At least two guide rollers that rotate and come into contact with the outer peripheral surface of the heating belt to press the heating belt toward the pressure roller and guide a part of the outer peripheral surface of the heating belt to form a nip with the pressure roller When,
A heat source provided on the inner peripheral surface side of the heating belt, for heating the heating belt;
A fixing device.   The fixing device according to claim 1, wherein the heat source can directly radiate heat to a heating belt portion forming a nip with the pressure roller.   The fixing device according to claim 1, wherein the heat source is a halogen heater. The fixing device according to claim 1, wherein the heating belt is formed of a thin metal material base, the inner peripheral surface is painted black, and the outer peripheral surface is coated with fluorine. .

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