JPH043321Y2 - - Google Patents

Description

[Detailed explanation of the invention] This invention is an electrophotographic copying machine, a computer
This relates to rollers used in electrostatic recording devices such as OCR and facsimile.

In conventional fixing pressure rollers of electrostatic recording devices, a shaft whose outer periphery is coated with a silicone rubber layer and whose outer periphery is coated with a surface layer of fluororesin is used. By the way, this pressure roller is pressed at a predetermined pressure (hereinafter referred to as nip pressure) to a heating roller whose outer periphery is coated with fluoroplastic on the outer periphery of a metal cylinder with a heating heater inside.
Due to the elastic deformation of silicone rubber, it is necessary to secure a contact width of about 4 to 7 mm (hereinafter referred to as nip width) between the heating roller and the heat-resistant silicone rubber, which is an elastic material that has been used conventionally.
Its hardness is limited to approximately 20° (JIS hardness), and in order to secure the specified nip width, it is necessary to apply considerable nip pressure (for example, a total load of 120 kgf).
As a result, the torque of the heating roller and pressure roller increases, and a more elastic motor and reinforced bearing are required, leading to higher costs.
Further, even if the rubber hardness was excessively lowered, there were problems such as insufficient nip pressure, especially the nip pressure applied to the toner surface, and a decrease in the durability of the pressure roller.

Therefore, the applicants have recently been developing a pressure roller that uses sponge rubber instead of silicone rubber. However, if a closed-cell sponge is used as the sponge rubber, the outer diameter will increase due to thermal expansion of the internal air during heating. increases, and when not in use at night or on holidays, the temperature returns to room temperature and the outer diameter decreases due to the contraction of the internal air.As this process is repeated, the surface layer of the fluorine resin undergoes plastic deformation and the outer diameter of the roller decreases. It was found that the cylindricity required for function could no longer be guaranteed due to deformation.

In order to solve the above problems, this invention makes it possible to secure a predetermined nip width with a small nip pressure by using an open-cell sponge as the sponge rubber material, and also guarantees a predetermined cylindricity at all times. This paper proposes a roller such as a pressure roller that is designed to The following describes an embodiment of this invention shown in the drawings. The figure shows an embodiment in which this invention is applied to a pressure roller for fixing. Open cell foam such as EPDM (foam with less than 50% closed cells)
A heat-resistant sponge rubber layer 3 with flexible elasticity formed thickly is coated, and the outer periphery of this sponge rubber layer 3 is further coated with tetrafluoroethylene resin (PTFE),
A flexible surface layer formed into a thin cylindrical shape using fluorine resins such as 4-fluoroethylene/6-fluoropropylene copolymer resin (FEP) and 4-fluoroethylene/perfluoroalkoxyethylene copolymer resin (PFA). 4 is covered with the sponge rubber layer 2 in an appropriately compressed state.

When the pressure roller 1 configured in this way is pressed against a heating roller 6 having a heating heater 5 inside at a predetermined nip pressure, the pressure roller 1 is made of an open-cell sponge rubber layer 3 with a flexible elastic body inside. Because of this, it is easily compressed and deformed to deform the surface layer 4 of the thin flexible fluorocarbon resin to follow the surface of the heating roller 1, creating a large nip width W with a small nip pressure.
In addition, since the surface layer 4 of the fluororesin has a relatively high hardness, the toner can be transferred reliably. Good fixing properties can be ensured by applying pressure.

Since the sponge rubber layer 3 is a foam with open cells and internal air can freely flow in and out, the outer diameter of the sponge rubber layer 3 will not change even if the internal air expands and contracts due to temperature changes. ,
The pressure roller 1 can always maintain stable cylindricity.

The roller configured as described above can be used not only as a pressure roller for fixing but also as a cleaning roller for a photoconductor or the like or a paper feeding roller.

As described above, according to this invention, the outer periphery of the shaft is covered with a thick sponge layer made of open-cell foam, and the outer periphery is covered with a thin surface layer made of fluorine resin, so that small nip pressure can be achieved. It is possible to secure a large nip width and maintain good fusing performance as a fusing roller, for example, and to reduce the power of the roller, which reduces the wear of the roller that presses against it and the burden on the bearing part. In a pressure roller, even if the air inside the sponge rubber layer expands and contracts due to temperature changes when the heating roller is heated and cooled, deformation is prevented by the free movement of air in and out, and the pressure roller can be used as a pressure roller. Stable cylindricity can always be maintained.

[Brief explanation of the drawing]

The figure is a longitudinal sectional view showing an embodiment of this invention. 1... Pressure roller, 2... Shaft, 3...
Sponge rubber layer, 4...Fluorine resin surface layer.

Claims (1)

[Scope of utility model registration request] A roller characterized in that the outer periphery of the shaft is covered with a thick sponge layer made of open-cell foam, and the outer periphery is covered with a thin surface layer made of fluororesin.