JPH0376459B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device for an image forming apparatus such as an apparatus using an image forming method such as electrophotography or electrostatic recording.

A conventional fixing device includes a fixing roller that is heated by heat from a heat source, and a pressure roller that is in pressure contact with the heating roller. However, a large amount of heat from the fixing roller is lost through air conduction, which increases the temperature of the image forming apparatus and requires extra heating source output.

In contrast, Japanese Patent Application Laid-open No. 50-160039,
There is a conventional fixing device as shown in FIG. 1, as disclosed in USP 3998584. A configuration is disclosed in which a reflection plate A made of aluminum with good heat reflection and heat conduction is fixedly provided around the fixing roller, and radiant heat from a heat source D is supplied to the surface of the fixing roller. This device is provided with a heat insulating material B that is separate from the reflective plate A and is outside the reflective plate, and a reflective plate C is provided in a fixed state in close contact with the heat insulating material B.

This device is simply a modification of conventional radiant heating in which a heating source D is provided between a reflector and a fixing roller. Furthermore, the heat insulating material B in the conventional device prevents heat radiation of the reflector A itself heated by the heat source D. However, since the reflector A is provided alone, its thickness is usually several mm or more. Therefore, a large amount of heat from the heat source D is consumed in order to heat the reflective plate A, which has a large heat capacity, and to maintain it above a certain temperature.

In addition, since the insulation material B of the above device is made of sponge or Nomex (product name: Dupont), the volume occupied by the insulation material itself (more than 1/3 of the fixing device) is extremely large, and the fixation is difficult. The device becomes very large.

Furthermore, since the heat insulator B retains and radiates heat, it is necessary to provide a reflective plate C on the outside of the insulator B. Further, the heat dissipation at the end of the heat insulating material B is so remarkable that the heating source D is provided at this member in the above device.

Therefore, the effect of preventing heat radiation is low, and the number of parts increases, resulting in an increase in cost. Further, in order to lock each component, a large number of screws E, screws, etc. that are in contact with the reflective member A are required, and heat loss transmitted through these locking members increases.

SUMMARY OF THE INVENTION An object of the present invention is to improve the above-mentioned conventional drawbacks, and to provide a fixing device that can prevent wasteful heat loss and has good thermal efficiency. Another object of the present invention is to provide a fixing device having a heat radiation prevention material that is inexpensive and compact.

The present invention will be explained below with reference to the drawings.

FIG. 2 is an explanatory diagram of one embodiment of the present invention. This figure shows a device in which a toner image T formed by electrophotography is fixed onto plain paper P by a heat fixing device.

1 is a heating roller having a heating heater 3 such as a halogen heater inside, and a driving motor (not shown).
It rotates in the direction of the arrow in response to the driving force from. 2 is a pressure roller with a built-in heater 3' for low heating;
It comes into pressure contact with the heating roller 1 and rotates slidingly.

This heating roller 1 has a heat-resistant mold release resin layer such as tetrafluoroethylene resin provided on the outer peripheral surface of a hollow roller core made of metal such as aluminum, stainless steel, or copper to a thickness of 20 to 80 μm.

The pressure roller 2 is rotatably supported by bearings 15, 15'. This roller 2 is pressed against the heating roller 1 by a known pressure means at least during fixing, and has a relatively thick elastic volume of silicone, fuso rubber, fluorosilicone rubber, etc. on the outer peripheral surface of a metal roller core. One purpose of this configuration is to secure a pressure contact area d with the heating roller.

A temperature sensing element 4 such as a thermistor or thermocouple is disposed in contact with the outer peripheral surface of the heating roller 1, and its detection signal is guided to a known control means (not shown) to control the temperature of the outer peripheral surface of the heating roller 1 ( Output of heater 3, or
By controlling the applied voltage, etc.), the toner image melting temperature is maintained.

Reference numeral 6 denotes a cleaning member for removing foreign matter such as offset toner and paper powder adhering to the surface of the heating roller from the roller surface.
A cleaning web ₆₁ made of heat-resistant nonwoven fabric such as Nippon Felt Kogyo Co., Ltd.) is used. The cleaning web 6 ₁ is brought into contact with the heating roller by an elastic pressing roller 6 ₃ . or,
This web 6 ₁ is moved by a driven take-up roller 6 ₅ (not shown) from the supply roller 6 ₂ so as to change its contact position little by little, so that a new surface of the cleaning web 6 ₁ always comes into contact with the heating roller. come into contact with This web 6 ₁ moves on the roller 6 ₄ interposed after the pressing roller 6 ₃ , is reversed toward the supply roller 6 ₂ , and is wound around the winding roller 6 ₅ with the front and back sides reversed. Also, during cleaning web 6 ₁ ,
If it is impregnated with an offset prevention liquid such as dimethyl silicone oil, the cleaning effect can be further enhanced.

Reference numeral 8 denotes a heat radiation prevention member made of a heat insulating material, which has a curvature such that it approaches the circumferential surface of the heating roller 1 at a predetermined distance _l1 , and is fixed within the apparatus by screws 31. The heat radiation prevention member 8 integrally has a heat-reflective metal thin surface layer 7 on the entire side surface on the circumferential side of the heating roller. This thin metal surface layer 7 has a substantially uniform thickness (about several hundred microns) with respect to the heat radiation prevention member 8;
It is in a non-contact state with the screw 31.

In the figure, the heat radiation prevention member 8 and the thin metal surface layer 7 each have a length that covers the entire axial direction of the heating roller, and a width that covers the space between the cleaning position where the pressing roller ₆₃ is located and the entrance portion of the paper P. have. It is preferable that this width covers the heating roller 1 as much as possible.

On the other hand, on the pressure roller 2 side, a heat radiation prevention material 10 having the same structure as the heat radiation prevention member 8 is provided at a predetermined distance _l2 from the circumferential surface of the pressure roller 2, so as to cover most of the surface. .

This heat radiation prevention material 10 also has a heat-reflective metal thin surface layer 9 with a substantially uniform thickness (approximately several hundred microns) on the entire side surface on the pressure roller circumferential side. This member 10 is also fixed by screws 31 that are not in contact with this layer 9.

22 is a guide plate that guides the paper P toward the heating roller 1 side;
located between one end of each of the heat radiation prevention members 8 and 10,
It is provided close to the heating roller 1. The paper P having the unfixed toner image T passes through the guide plate 22 and is conveyed while being held between the heating and pressing rollers 1 and 2, and the toner image is formed by heating applied by the surface temperature of the rollers 1 and 2. T is fixed, and then the paper is ejected from the apparatus while being held between paper ejection rollers 20 and 21. On the discharge port side of the heating roller, a plurality of separation claws 5 are provided in contact with the roller surface along the roller axis direction in order to reliably separate the paper P from the heating roller. Further, a separation claw ₅₁ is provided on the discharge port side of the pressure roller 2 so as to be in contact with the surface of the roller 2. The separation claw 5 is held by a support plate 18 that is spaced apart from the casing member 16, and the separation claw 5 ₁
The support plate ₁₈₁ , which is spaced apart from the casing member 17 on the lower side of the fixing device, is also held. The casing member 17 is spaced apart from the thin metal surface layer 9 of the pressure roller 2 and the heat radiation prevention member 10, and is provided so as to cover these. The casing member 16 surrounds the cleaning member 6, the heat radiation prevention member 10, and the temperature sensing element 4, and the casing member 17 also serves as the bottom plate of the entire fixing device.

The heat radiation prevention members 8 and 10 are made by blending inorganic fibers such as glass wool or rock wool with about 3 to 30% of a heat-resistant resin such as phenol resin, and press-molding the mixture while applying heat. The thermal conductivity of this material varies depending on the fiber diameter, fiber density, etc.
Fiber diameter 7-8μ, density 80Kg/ ^m3 , 0.038Kcal/m.
h.℃, which is about 1/5 smaller than that of general resin materials, and has excellent heat removal performance. Incidentally, the entire end portion of this member was pressurized with a pressure greater than that during the above-mentioned press molding, so that the density was 300 Kg/m ³ or more.

Further, the metal thin surface layers 7 and 9 of the heat radiation prevention member are formed by press-molding metal foil such as aluminum foil or stainless steel foil through a thermoplastic resin sheet such as polyethylene or polysulfone at the same time as the heat radiation prevention member. In this way, the thermoplastic resin sheet is melted by heat, the metal foil is adhered to the surface of the heat radiation prevention member, and a reflective surface can be obtained on the surface of the heat radiation prevention member without increasing the number of blinking steps.

Thereby, the function of reflecting radiant heat from heated members such as the roller 1 can be sufficiently performed, and at the same time, the thickness of the metal thin surface layers 7 and 9 can be reduced. In other words, whereas the conventional single reflector requires increased strength and heat capacity, this example has sufficient strength as a heat radiation prevention material, and its heat capacity can be extremely reduced. The thickness of these metal thin surface layers 7 and 9 is in the range of 5 to 500 ml, which is called a foil.
It is preferable to set it to 300μ.

That is, the thickness of the metal thin surface layers 7 and 9 is 5 to 300μ.
If so, its own heat capacity will be small and its heat reflection efficiency will be very good. In addition, the metal thin surface layers 7 and 9 are in close contact with the heat radiation prevention members 8 and 10, respectively, and are located on the heated member side, so that heat conduction and heat radiation from the metal thin surface layers as reflective members are significantly reduced. The reflection efficiency can be improved. In other words, the metal thin surface layer 7,
The heat radiation prevention member 9 and the heat radiation prevention member improve their respective functions and exhibit an excellent heat radiation prevention effect. Therefore,
Heat from a heating roller, which is an example of a heated member, can be effectively used for fixing. Furthermore, since heat emission is significantly reduced, the time required for the heating roller to heat up to a predetermined temperature can be shortened.

Since the mixture of the inorganic fiber and resin is compressed, it has a high heat radiation prevention effect and can be made thinner and smaller.

A further feature of the above embodiment is that the radiant heat from the heating roller is molded and compressed into a curvature that is substantially the same as the curvature of the rotating body (roller, etc.) as described above, so that it can be most efficiently reflected and returned to the roller surface.

Next, as another example, a glass fiber mixed with a resin (or a glass fiber itself containing resin), which can obtain strength relatively easily, is heated and a metal foil is heated through a thermoplastic resin. The heat radiating member is formed by pressure molding. When using fibers with a fiber diameter of 7 to 8μ, if the density is set to 50Kg/m3 ^or more, sufficient rigidity can be obtained to hold the shape by itself, and the means to support it is this heat radiation prevention member. It will be better if you just support one end of it.

When glass fiber is used as described above, it is possible to improve the reflection efficiency and the heat radiation prevention effect, respectively, in the same manner as described above.

To explain yet another embodiment, the second
As shown in the explanation of the figures, the fiber density at the end portions of the heat radiation prevention member made of inorganic fibers, particularly fine fibers, is made higher than the other portions. That is, in a member made of such fibers, the fibers may scatter from the ends thereof. In order to prevent such defects, the fiber density at the end (or near the end) is set to 300Kg/m ³
If the material is compressed during molding so as to achieve the above, a more favorable effect will be produced. In this way, it is possible to prevent the adhesive from scattering without adding an additional step such as applying adhesive to the end portion.

As described above, by providing a heat radiation prevention member with improved reflection efficiency at least on the roller side surface, a fixing device that is inexpensive, lightweight, and capable of efficient heat radiation prevention has been obtained.

In the above embodiment, an example was shown in which rollers such as a fixing roller, a heating roller, and a pressure roller were provided.
The present invention is particularly effective for heated conveyor belts, heated rotating bodies (glass-like cylinders), and can also be applied to reflective shades for flash lamps that are heated without rotating.

Although examples using a mixture of inorganic fiber and heat-resistant resin, examples using glass fiber mixed with heat-resistant resin, or examples using glass fiber alone have been shown for the above-mentioned heat radiation prevention member, the present invention is limited to these. Any material may be used as long as it is made of inorganic fibers containing a resin component.

Note that the distances l ₁ and l ₂ in the above embodiment are both 0.2 mm to 20 mm.
The value is preferably 5 mm, more preferably 5 mm or less.

Further, as the heat-resistant resin material to be mixed or contained in the inorganic fibers in the above embodiments, resins such as PPS, polyimide, PBT, tetrafluoroethylene, or polyamide can be used in addition to the above-mentioned phenol resin.

As is clear from the above, the present invention has a member that has a higher heat radiation prevention effect than the conventional one, reduces heat radiation from the heated member, and can effectively apply heat from the heating means to the heating member.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a conventional fixing device, and FIG. 2 is an explanatory diagram of an embodiment of the present invention. A is a reflector, B is a heat insulator, D is a heat source, 1 is a heating roller, 2 is a pressure roller, 3, 3' is a heater, 7,
9 is a metal thin surface layer, and 8 and 10 are heat radiation prevention members.

Claims (1)

[Scope of Claims] 1. A rotating body heated by a heating means, and a heat radiation prevention device that covers at least a portion of the circumferential surface of the rotating body, is provided close to the rotating body, and has a metal surface on the rotating body side surface. 1. A fixing device comprising a member, wherein the heat radiation prevention member is formed by adhering a metal film on a mixture of inorganic fibers and a heat-resistant resin with a thermoplastic resin sheet.