JP2010286798A - Fixing device and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fixing device, fixing toner to a sheet material such as paper and an envelope, and preventing the occurrence of creases in fixing to the envelope; and to provide an image forming apparatus. <P>SOLUTION: This fixing device includes: a heat roller having a heat source; a press roller for pressing an endless fixing belt to the heat roller; and a tension roller for adjusting the tension of a fixing belt, and the fixing device fixes a toner image transferred to a record medium such as paper to the record medium. The fixing device includes a switching means capable of switching the pressing force of the press roller and switching the tension of the fixing belt according to the kind of the record medium, and when the pressing force is lowered, the tension is decreased. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a fixing device that can fix toner on an envelope in addition to paper such as plain paper, a film, and the like, and an image forming apparatus including the fixing device.

  In general, in an image forming apparatus such as an electrophotographic copying machine, printer, or facsimile, a toner image formed on a photosensitive drum as an image carrier or an intermediate transfer belt as an intermediate transfer member in an image forming unit. A fixing device is used which is transferred to a recording medium such as paper and fixed on the recording medium by applying heat and pressure thereto.

The fixing device includes a heat roller having a heat source such as a heater inside and heated to a predetermined temperature, a press roller disposed opposite to the heat roller, and a tension roller. The press roller and the tension roller include Some have an endless fixing belt wound around.
In such a fixing device, the fixing belt is pressed against the heat roller by the press roller, is tensioned by the tension roller, and is pressed against the heat roller by its own tension.
When the recording medium is nipped between the heat roller and the fixing belt and pressed by the press roller, the pressure is the same as when nipping only with the heat roller and the press roller, and the contact area becomes large. And the toner image is easily fixed on the recording medium.

Here, the recording medium on which the toner image is fixed by the fixing device includes an envelope in addition to a sheet material such as paper or film.
However, unlike a sheet material, an envelope has a folded portion and an overlapping portion for bonding, the thickness is not uniform, and wrinkles occur when high pressure is applied at the nip portion for fixing. There is a problem.

  In order to prevent this, in Patent Document 1, when the envelope is fixed, the press roller and the tension roller are moved together with respect to the heat roller so that the press roller does not directly press the fixing belt against the heat roller. A fixing device that fixes a toner image by applying pressure with a belt tension is disclosed. Patent Document 2 discloses a fixing device that moves the heat roller relative to the press roller and the tension roller to provide the same action.

  However, in the fixing devices disclosed in Patent Documents 1 and 2, the press roller does not directly press the fixing belt against the heat roller, and is pressed by the tension of the fixing belt tensioned by the tension roller. The generation of wrinkles in the envelope cannot be suppressed.

JP 2006-337439 A JP 2006-337440 A

  SUMMARY OF THE INVENTION In view of the above problems, the problem to be solved by the present invention is a fixing device capable of fixing toner to a sheet material such as paper and an envelope, and a fixing device and an image forming apparatus capable of preventing the generation of wrinkles during envelope fixing Is to provide.

  The invention according to claim 1 includes a heat roller having a heat source, a press roller that presses the endless fixing belt against the heat roller, and a tension roller that adjusts the tension of the fixing belt. A fixing device for fixing a transferred toner image to the recording medium, wherein the pressing force of the press roller can be switched and the tension of the fixing belt can be switched according to the type of the recording medium. The present invention relates to a fixing device that includes a switching unit and reduces the tension when the pressing force is reduced.

  According to a second aspect of the present invention, there is provided a pressure spring that applies a pressing force of the press roller, and an adjustment spring that biases the tension roller and applies tension to the fixing belt, and the switching means includes the pressure spring. The fixing device according to claim 1, wherein the fixing mechanism is a cam mechanism that switches between tension and relaxation of the biasing force of the adjustment spring.

  According to a third aspect of the present invention, when the pressing force is decreased by the switching means, the temperature of the heat source is increased, or the feed speed of the heat roller and the press roller is decreased, or the temperature increase and the The fixing device according to claim 1, wherein both the feeding speed reduction is performed.

  A fourth aspect of the present invention relates to an image forming apparatus including the fixing device according to any one of the first to third aspects.

  The invention according to claim 5 relates to the image forming apparatus according to claim 4, wherein the switching means can be operated on an operation panel.

  The invention according to claim 6 relates to the image forming apparatus according to claim 4, wherein the operation of the switching means can be performed on a terminal connected to the image forming apparatus.

  According to the first aspect of the present invention, a recording medium such as paper is provided, which includes a heat roller having a heat source, a press roller that presses an endless fixing belt against the heat roller, and a tension roller that adjusts the tension of the fixing belt. A fixing device for fixing the toner image transferred to the recording medium to the recording medium, wherein the pressing force of the press roller can be switched and the tension of the fixing belt can be switched according to the type of the recording medium By reducing the tension when the pressing force is reduced, the tension of the fixing belt can be reduced together with the pressing force of the press roller at the time of fixing the envelope, so that excessive pressure is applied to the envelope. No wrinkle is generated.

  According to the second aspect of the present invention, the pressure spring for applying the pressing force of the press roller and the adjustment spring for biasing the tension roller and applying tension to the fixing belt are provided, and the switching means includes the pressure spring and the adjustment spring. By using the cam mechanism that switches between tension and relaxation of the urging force, it is possible to easily switch between the case of fixing an envelope and the case of fixing a sheet material such as paper.

  According to the invention of claim 3, when the pressing force is reduced by the switching means, the temperature of the heat source is raised, or the feed speed of the heat roller and the press roller is lowered, or both the temperature rise and the feed speed are lowered. By performing the above, the lack of pressure necessary for fixing can be compensated for at a high temperature, a long time, or both a high temperature and a long time, and a fixing failure can be prevented.

  According to the invention according to claim 4, by providing the fixing device according to any one of claims 1 to 3, an image can be formed on a sheet material such as paper and an envelope, and wrinkles are generated during envelope printing. The image forming apparatus can be prevented.

  According to the fifth aspect of the invention, since the switching unit can be operated on the operation panel, it is possible to perform the switching safely without the operator placing a hand inside the image forming apparatus.

  According to the sixth aspect of the invention, since the operation of the switching unit can be performed on the terminal connected to the image forming apparatus, even when the operator's terminal is located away from the image forming apparatus, the switching is performed. In addition, it is not necessary to move to the installation position of the image forming apparatus.

1 is a schematic cross-sectional view of a general fixing device. FIG. 3 is a partial perspective view of a fixing device according to the present invention. FIG. 7 is a partial perspective view for explaining the operation of the switching unit of the fixing device according to the present invention. 1 is a schematic sectional view of an image forming apparatus according to the present invention.

Preferred embodiments of a fixing device and an image forming apparatus according to the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic cross-sectional view of a general fixing device, and the present invention includes an additional structure in the fixing device (1).
2 is a partial perspective view of the fixing device according to the present invention. FIG. 2A is a view from the outside of the device, and FIG. 2B is a view from the inside of the device.

  As shown in FIG. 1, a fixing device (1) according to the present invention includes a heat roller (11) having a heater (111) inside as a heat source, a press roller (12) pressed against the heat roller (11), A fixing belt (13) wound around a press roller (12) and pressed against a heat roller (11), a tension roller (14) for adjusting the tension of the fixing belt (13), and a delivery roller pair (15) are provided. Yes.

  The fixing device (1) nips a recording medium such as paper or an envelope onto which a toner image is transferred at a nip (N) formed by a heat roller (11) and a fixing belt (13), and a heater (111). The toner is fixed on the sheet by heating with the heat roller (11) heated by the pressure and pressing the pressurizing belt (13) with the press roller (12) and applying pressure. The recording medium on which the toner has been fixed is sent to the next process by the sending roller pair (15).

The fixing device (1) includes an adjustment spring (141) as shown in FIG. 2A, and adjusts the tension of the fixing belt (13) by applying the biasing force to the tension roller (14).
Moreover, as shown in FIG.2 (b), a pressurization spring (121) is provided. The pressure spring (121) applies a pressing force to the press roller (12) by its urging force.
In this embodiment, the pressure spring (121) and the adjustment spring (141) are both compression springs, but are not limited thereto.

As shown in FIG. 2, the fixing device (1) switches the urging force of the pressure spring (121) and the adjustment spring (141) to switch the pressing force of the press roller (12) and the tension of the fixing belt (13). The switching means (16) which can do is provided.
The switching means (16) is connected to a drive source (not shown) such as a motor and rotated, a cam (162) rotated by the drive shaft (161), and moved up and down by the cam (162). A bracket (163), a bracket (164) linked to the bracket (163), and the like are included.
Although omitted in the figure, the press roller (12) is supported by a bracket (164).
These operations will be described with reference to FIG.

FIG. 3 is a partial perspective view of the fixing device (1) for explaining the operation of the switching means (16), in which the press roller (12) and the fixing belt (13) are omitted.
3A shows a state when the recording medium is a sheet material such as paper (hereinafter simply referred to as paper), and FIG. 3B shows a state when the recording medium is an envelope.

  When the recording medium is paper, as shown in FIG. 3A, the cam (162) is in a position not in contact with the bracket (163), and the bracket (163) is pushed downward by the pressure spring (121). ing. The bracket (164) is also pulled downward by linking to the bracket (163), and the press roller (12) (not shown in FIG. 3) supported by the bracket (164) is pressed against the heat roller (11).

  At this time, the adjustment spring (141) is also pushed downward by the bracket (163), and the adjustment spring (141) is compressed. Therefore, the tension of the fixing belt (13) (not shown in FIG. 3) is increased by the biasing force. .

  On the other hand, when the recording medium is an envelope, as shown in FIG. 3B, the cam (162) is rotated by the drive shaft (161), and the bracket (163) is pushed upward by the cam (162). Since the bracket (164) is also linked and pushed upward, the pressing force of the press roller (12) supported on the heat roller (11) is relaxed.

  At this time, the compression of the adjustment spring (141) is relaxed, the urging force is reduced, and the tension of the fixing belt (13) is reduced.

  As described above, by using the cam mechanism, when the recording medium is an envelope, the pressing force of the press roller (12) and the tension of the fixing belt (13) can be reduced, and excessive pressure is applied to the envelope. In addition, wrinkles are not generated in the overlapping portion of the envelope.

Further, when the pressing force of the press roller (12) and the tension of the fixing belt (13) are lowered as described above, the temperature of the heater (111) is increased, or the heat roller (11) and the press roller (12 It is preferable to reduce the feed speed of (3) or both.
Since the pressure decreases due to fixing, there is a risk that fixing failure may occur due to insufficient pressure, but fixing failure can be prevented by fixing at high temperature, a long time, or both high temperature and long time. It is.

The fixing device (1) according to the present invention can be applied to an image forming apparatus such as a copying machine, a printer, or a facsimile.
In the present embodiment, a printer is taken as an example of the image forming apparatus (100) as shown in FIG.

  By providing the fixing device (1), the image forming apparatus (100) can easily switch between printing on a sheet material such as paper and printing on an envelope, and can generate wrinkles during envelope printing. Can be prevented.

In the image forming apparatus (100), it is preferable that the switching described above can be performed from an operator's terminal connected to the image forming apparatus (100).
This is because the image forming apparatus (100) can be easily switched even when it is located away from the operator.

In addition, when the image forming apparatus (100) is a copying machine or a multifunction machine, switching may be performed on the operation panel.
This is because the operator can switch safely without putting a hand inside the apparatus.

  INDUSTRIAL APPLICABILITY The present invention is suitably used for a fixing device that fixes toner by heating and pressurization, an electrophotographic image forming apparatus such as a copying machine, a printer, and a fax machine including the fixing device, and other printing machines. It is what is done.

DESCRIPTION OF SYMBOLS 1 Fixing device 11 Heat roller 12 Fixing belt 121 Pressure spring 13 Press low roller 14 Tension roller 141 Adjustment spring 16 Switching means 162 Cam 100 Image forming apparatus N Nip part

Claims (6)

A heat roller having a heat source, a press roller for pressing an endless fixing belt against the heat roller, and a tension roller for adjusting the tension of the fixing belt,
A fixing device for fixing a toner image transferred to a recording medium such as paper to the recording medium,
According to the type of the recording medium, the pressing force of the press roller can be switched, and switching means capable of switching the tension of the fixing belt is provided.
A fixing device that reduces the tension when the pressing force is reduced. A pressure spring that applies a pressing force of the press roller, and an adjustment spring that urges the tension roller to apply tension to the fixing belt,
The fixing device according to claim 1, wherein the switching unit is a cam mechanism that switches between tension and relaxation of a biasing force of the pressure spring and the adjustment spring.   When the pressing force is reduced by the switching means, the temperature of the heat source is increased, the feed speed of the heat roller and the press roller is lowered, or both the temperature rise and the feed speed are reduced. The fixing device according to claim 1 or 2.   An image forming apparatus comprising the fixing device according to claim 1.   The image forming apparatus according to claim 4, wherein the switching unit can be operated on an operation panel.   The image forming apparatus according to claim 4, wherein the switching unit can be operated on a terminal connected to the image forming apparatus.

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