JP4893098B2 - Fixing apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a fixing device, and more particularly to a fixing device for heating and fixing a toner image formed on a recording medium by electrophotography, and an image forming apparatus such as a copying machine and a printer including the fixing device.

  Conventionally, in an image forming apparatus such as an electrophotographic copying machine or a printer, a toner image transferred onto a recording medium is heated and fixed by passing it through a fixing device. The fixing device includes a heating rotator and a pressure rotator that presses the recording medium against the heating rotator, and a thermistor for temperature control is provided in proximity to or in contact with the outer peripheral surface of the heating rotator. Yes.

  By the way, when a paper jam occurs in which the recording medium becomes bellows on the outer peripheral surface of the heating rotator in the fixing device, the jammed recording medium damages or deforms the thermistor, changes its position, and causes an accurate temperature. There was a problem that it could not be detected. Further, when the recording medium is wound around the heating rotator, the recording medium comes into contact with the thermistor when releasing the winding, and the same problem occurs.

Patent Document 1 discloses a fixing device in which a support member is provided on a back portion of a contact portion (detection body) of a thermistor that contacts a heating rotator. However, in this fixing device, the accordion-like paper jam itself in the vicinity of the thermistor cannot be prevented, and when the pressure of the support member is high, the contact portion (detecting body) causes the outer peripheral surface of the heating rotator to move. There is also a risk that image noise may occur due to damage.
JP-A-10-301440

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a fixing device and an image forming apparatus that can prevent the occurrence of a bellows-like paper jam in the vicinity of the temperature detecting means and prevent the temperature detecting means from being damaged, deformed, or misaligned. It is in.

In order to achieve the above object, the first invention
In a fixing device for heat fixing a toner image formed on a recording medium by electrophotography,
A heating rotator, a pressure rotator that presses the recording medium against the heating rotator, a contact member that contacts the heating rotator, and a heating rotator from a first nip portion of the heating rotator and the pressure rotator. The temperature detecting means between the contact member and the second nip portion and close to or in contact with the outer peripheral surface of the heating rotator, and the temperature detecting means on both sides of the temperature detecting means in the axial direction of the heating rotator A guide member provided along the outer peripheral surface of the heating rotator over the arrangement position of the contact member;
It is provided with.

  In the fixing device according to the first aspect of the present invention, since the guide member is provided along the outer peripheral surface of the heating rotator from the arrangement position of the temperature detection means to the arrangement position of the contact member, even if a paper jam occurs. The recording medium is regulated by the guide member and does not become bellows in the vicinity of the position where the temperature detecting means is disposed, and the temperature detecting means is not damaged or deformed by a paper jam, and the position does not change. In addition, when the recording medium is wound around the heating rotator, the temperature detecting means is protected by the guide member when the recording medium is removed, so that the recording medium to be removed is damaged, deformed, or moved. It is not.

  In the fixing device according to the first aspect of the invention, the contact member is a roller that cleans, for example, toner adhered to the heating rotator. The temperature detection means is, for example, a thermistor. Further, the temperature detecting means may be integrally attached to the guide member.

  An image forming apparatus according to a second aspect includes the fixing device.

  Hereinafter, embodiments of a fixing device and an image forming apparatus according to the present invention will be described with reference to the accompanying drawings.

(Schematic configuration of image forming apparatus, see FIG. 1)
FIG. 1 shows a monochrome type printer 10 which is an embodiment of an image forming apparatus. The printer 10 includes a charging charge 12, an image exposure unit 13, a developing device 14, a transfer roller 15, a separation claw 16, a residual toner cleaner blade 17, along a rotational direction indicated by an arrow a around the photosensitive drum 11. A residual charge eraser lamp 18 is provided. The configuration and operation of this type of electrophotographic imaging element are well known, and details of the imaging process are omitted. A sheet feeding cassette 20 is installed below the photosensitive drum 11 and a fixing device 30 is installed above.

  The recording medium is fed one sheet at a time from the sheet feeding cassette 20 by the sheet feeding roller 21, and the fed recording medium is synchronized with the toner image formed on the photosensitive drum 11 from the timing roller 22. The toner image is transferred to the transfer unit. Thereafter, the recording medium is heated and fixed on the toner image by the fixing device 30 and is discharged onto a tray (not shown). The conveyance path of the recording medium is as shown by a one-dot chain line in FIG.

(Fixing device, see FIGS. 2 to 7)
As shown in FIG. 2, the fixing device 30 is roughly composed of a heating roller 31 and a pressure roller 35, and the recording medium pressurizes the first nip portion N <b> 1 between the rollers 31 and 35 by the pressure roller 35. Received and transported. The heating roller 31 incorporates a heater 32 such as a heat lamp, an induction heating element, or a resistance heating element, and a recording medium separation claw 33, a toner cleaning roller 36, and a thermistor 37 are in contact with the outer peripheral surface. The thermistor 37 is disposed between the first nip portion N1 and the second nip portion N2 between the heating roller 31 and the cleaning roller 36, and detects the outer peripheral surface temperature of the heating roller 31 for temperature control.

  Further, a guide member 40 </ b> A is provided along the outer peripheral surface of the heating roller 31 from the position where the thermistor 37 is disposed to the position where the cleaning roller 36 is disposed. The guide member 40A is formed by bending a metal plate such as stainless steel or aluminum, or is formed of a heat resistant resin material such as PI, PA, or PPS. As shown in FIG. The guide portions 41, 41 along the outer peripheral surface of the fixing device 30, a mounting portion 42 for screwing the fixing device 30 to the housing, and a notch portion 43 for disposing the thermistor 37.

  The guide member 40 </ b> A can adopt various shapes other than those shown in FIG. 3, and the shape can be arbitrarily changed according to the attachment position and the shape of the heating roller 31. For example, the guide members 40B, 40C, 40D, and 40E shown in FIGS. 4, 5, 6, and 7 may be used.

  A guide member 40B shown in FIG. 4 has support portions 44, 44 on both sides. The guide member 40 </ b> C shown in FIG. 5 includes a tongue piece 45, and the thermistor 37 is integrally attached to the tongue piece 45. In the guide member 40 </ b> D shown in FIG. 6, the guide portions 41 and 41 are connected so that the notch portion 43 surrounds the thermistor 37 so as to further protect the thermistor 37. The guide member 40E shown in FIG. 7 achieves improvement in attachment strength and prevention of deformation of the guide portions 41 and 41 by screwing the tip portions 41a of the guide portions 41 and 41 together with the attachment portion 42 to the housing. I have to.

  By the way, the heating roller 31 is composed of a surface layer, an intermediate layer, and a metal core, and has an outer diameter of 20 to 50 mm, a straight shape, or a crown shape in which the outer diameter of the central portion is larger than both end portions, and the outer diameter of both end portions. An inverted crown shape that is larger than the central portion. In the case of different diameters, the difference in outer diameter is about 0.001 to 3 mm. The surface layer is desirably provided with releasability such as a fluorine tube or a fluorine coating, and has a thickness of 5 to 100 μm. The intermediate layer is made of a heat-resistant elastic material such as silicone rubber or fluorine rubber, and has a thickness of 0.05 to 5 mm. The core metal is made of a metal material such as aluminum or iron and has a thickness of 0.1 to 5 mm.

  The pressure roller 35 is composed of a surface layer, an intermediate layer, and a metal core, and has an outer diameter of 20 to 50 mm, a straight shape, or a crown shape in which the outer diameter of the central portion is larger than both end portions, and the outer diameter of both end portions is the center. An inverted crown shape larger than the portion. In the case of different diameters, the difference in outer diameter is about 0.001 to 3 mm. The surface layer is desirably provided with releasability such as a fluorine tube or a fluorine coating, may be conductive, and has a thickness of 5 to 100 μm. The intermediate layer is made of a heat-resistant elastic material such as silicone rubber, fluorine rubber, or sponge, and an appropriate additive is added thereto, and the thickness is 1 to 20 mm. The core metal is made of a pipe-like metal material such as aluminum or iron, and has a thickness of 0.1 to 5 mm. The core metal may be solid, or the cross-sectional shape may be an irregular shape such as a three-headed shape. Further, the core bar may be omitted and the intermediate layer may be a solid body.

  In the fixing device 30 configured as described above, since the guide member 40A is provided along the outer peripheral surface of the heating roller 31 from the position where the thermistor 37 is disposed to the position where the cleaning roller 36 is disposed, even if a paper jam occurs. The recording medium is not regulated by the guide member 40 </ b> A and does not become bellows near the position where the thermistor 37 is disposed. Therefore, the thermistor 37 is not damaged or deformed by a paper jam, and the position does not change.

  In addition, when the recording medium is wound around the heating roller 31, the thermistor 37 is protected by the guide member 40A when the recording medium is removed, so that the recording medium to be removed is damaged, deformed, or moved. It is not. The fixing device 30 can maintain accurate temperature detection by preventing the thermistor 37 from being damaged, deformed, or misaligned due to a paper jam.

(Other examples)
The fixing device and the image forming apparatus according to the present invention are not limited to the above-described embodiments, and can be variously modified within the scope of the gist.

  For example, the image forming apparatus may be a color printer, a copying machine, a facsimile, or a complex machine of these in addition to a monochrome printer. The guide member may have a configuration and shape other than those shown in FIGS. Further, the temperature detecting means may be a non-contact type thermistor, and the structure for attaching the guide member and the fixing device to the housing is arbitrary.

  Further, the heating rotator and the pressure rotator may be in the form of a belt other than the roller shape shown in the above embodiment, and the pressure rotator may be provided with heating means. In addition to the toner cleaning roller, the contact member may be a cleaning web, a cleaning pad, or a heating auxiliary roller.

1 is a schematic configuration diagram illustrating a monochrome printer which is an example of an image forming apparatus according to the present invention. FIG. 2 is a cross-sectional view showing a fixing device mounted on the printer. 2A and 2B show a first example of a guide member provided in the fixing device, where FIG. 1A is a perspective view and FIG. 1B is a cross-sectional view. It is a perspective view which shows the 2nd example of the said guide member. It is a perspective view which shows the 3rd example of the said guide member. It is a perspective view which shows the 4th example of the said guide member. The 5th example of the said guide member is shown, (A) is a perspective view, (B) is sectional drawing.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Printer 30 ... Fixing device 31 ... Heating roller 35 ... Pressure roller 36 ... Cleaning roller 37 ... Thermistor 40A-40E ... Guide member N1, N2 ... Nip part

Claims (7)

In a fixing device for heat fixing a toner image formed on a recording medium by electrophotography,
A heating rotor,
A pressure rotator that presses the recording medium against the heating rotator; and
A contact member that contacts the heating rotator;
Temperature detection between the first nip portion of the heating rotator and the pressure rotator and the second nip portion of the heating rotator and the contact member and in proximity to or in contact with the outer peripheral surface of the heating rotator Means,
Guide members provided along the outer circumferential surface of the heating rotator over both sides of the temperature detecting means in the axial direction of the heating rotator from the arrangement position of the temperature detection means to the arrangement position of the contact member;
A fixing device comprising:   The fixing device according to claim 1, wherein the contact member is a cleaning roller.   The fixing device according to claim 1, wherein the temperature detection unit is integrally attached to the guide member. The fixing device according to claim 1, wherein the guide member includes a notch portion that is connected in an axial direction of the heating rotator and surrounds the temperature detection unit. The said guide member has an attaching part for attaching to an apparatus main body part in the upstream and downstream of the said temperature detection means in the rotation direction of the said heating rotary body, The Claim 1 or Claim 2 characterized by the above-mentioned. The fixing device according to 1. Said temperature detecting means fixing device according to any one of claims 1 to 5, characterized in that a thermistor. An image forming apparatus comprising the fixing device according to claim 1 .

Images