JPS5944631B2 - Contact heating roll type fixing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a contact heating roll type fixing device, and more specifically, the present invention relates to a contact heating roll type fixing device.
The present invention relates to a fixing device that permanently attaches an unfixed image formed using toner (hereinafter referred to as toner).

Conventionally, a fixing device is known that performs fixing by applying a constant pressure between two heated rolls and passing a recording medium carrying an unfixed toner image. It has advantages such as low power consumption and less risk of fire due to paper jams in the fixing section.

However, on the other hand, there is a drawback that the time required for the temperature of the heating roll to rise from room temperature to the fixing temperature after electricity is applied (hereinafter referred to as warm-up time) is long.

Generally, the warm-up time for this type of fixing device in a copying machine is 5 to 10 minutes. Conventionally, as an attempt to shorten this warm-up time, a device as shown in FIG. 1 has been known.

In other words, the surface of the heating roll 1 is coated with a heat-resistant release material 2 (for example, silicone rubber) that is a poor thermal conductor, and only the surface layer thereof is externally heated using, for example, an infrared lamp 5.
However, in this method, since a heating element is disposed outside, there is a risk that the paper will catch fire in the event of a paper jam, and the thermal efficiency is not good, which is not practical. There is also a method of supplying a large amount of electric power to the heating roll, but since there is a limit to the power consumption of the machine, this method is not practical because the maximum electric power is automatically determined for copying machines that use a household power source. Furthermore, in order to reduce power consumption, a method was considered to reduce the heat capacity by reducing the thickness of the heating roll. It has been impossible to actually reduce the thickness of the heating roll due to the action of external mechanical forces.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fixing device with shortened warm-up time. Accordingly, the present invention provides a fixing device that fixes a toner image on a recording medium by passing the recording medium having a toner image through a nip formed by a heating roll and a roll that is in pressure contact with the heating roll. The present invention provides a fixing device characterized by being made of a heat-resistant sponge-like elastic body with a sponge rubber hardness of 300 or less, and as an embodiment of the fixing device, the heating roll has a wall thickness of 0.1 to 2.0 m71L. It provides equipment.

According to the present invention, the above-mentioned objects are achieved by reducing the thickness of the heating roll so that the heat capacity of the roll itself is extremely reduced. This is achieved by combining a pressure roll 4 using heat-resistant sponge-like rubber as the heat-resistant elastic body 9 (see FIG. 3).

Generally, the warm-up time of a heating roll is mainly determined by the thickness of the roll and the electric power.

Generally, it is said that the time that people can wait without feeling uncomfortable when making a copy is 100 seconds or less (preferably 30 seconds or less). Therefore, it is desirable to keep the warm-up time within this time as much as possible. The thickness of the conventional heating roll is 5m77! ~10m77! It was hot, but
Generally, in a copying machine, the power to the fixing device is 800W ~ 1
A heating roll of 200 W is often used, and in order to keep the warm-up time within the above range with this power, it is desirable that the thickness of the heating roll be 2.0 mm or less (preferably 0.6 mm or less). However, when the thickness of the heating roll becomes extremely thin, the heat capacity becomes small and the merits of contact heat fixing are reduced. Further, the minimum thickness C field is determined mainly by structural problems that can withstand external forces and the need to store heat in order to fix unfixed images. The inventors have determined that the thickness of the heating roll depends on factors such as the contact pressure of the pressure roll, roll material, and roll shape. We found that the pressure roll is made of a spongy elastic material with a hardness of about 5 to 100 when measured with an Asuka I-C type hardness tester (manufactured by Kobunshi Keiki Seisakusho). It has been found that if the heating roll is used, a minimum thickness of 0.1 mm is sufficient for the heating roll.

Therefore, the thickness of the heating roll is preferably 0.1 to 2.0 mm. Examples of the heat-resistant spongy elastic body used in the present invention include silicone sponges and fluorosponges.
4 The elastic body constituting the conventional pressure roll is not spongy, but has a shore A hardness of 20 to 90, for example.
Viton (trade name of fluoroelastomer manufactured by DuPont), fluorosilicone, silicone rubber, etc. In contrast, in the present invention, the heating roll can be made thinner by using a pressure roll made of a sponge-like elastic body, and the sponge hardness of the sponge-like elastic body is preferably 300 or less as described later. The sponge rubber hardness referred to in this application is measured according to the Japan Rubber Association standard SRIS-0101. Furthermore, the load pressure of conventional pressure rolls is 3k9/Cfl to 10kg/Cril, but in the case of the pressure roll of the present invention, it is 1.5kg/Cd to 0.1kg.
/d, and the load pressure can be reduced to about 1/10 compared to the conventional one. In addition, the pressure roll of the present invention has a large nip width, which improves the contact effect between the heating roll and the toner image and ensures fixation. By the way, the width of the conventional fixing roll nip is 1077 mm! l, but in the case of the invention of the present application, it is 10
mm~20m7! It is L. The actual pressure roll has an outer diameter of 55 m, 1 L, a length of 370 mm, and a sponge-like elastic body with a wall thickness of 15 mm, each with a sponge rubber hardness of 100 and 20.
Figure 2 shows the relationship between the load and nip width for Nos. 1 and 30.

Generally, as the sponge rubber hardness of the pressure roll increases, it is necessary to increase the load to obtain the same nip width, and accordingly, a correspondingly greater load is applied to the heating roll.

Naturally, the heating roll has a limit load for structural reasons, and this is 100%, taking into account the thickness of the heating roll.
kg or less, preferably 50 kg or less is considered appropriate. Furthermore, the rubber hardness of the sponge-like elastic body is determined by considering the nip width necessary for fixing. According to experiments conducted by the present inventors, in order to obtain fixing performance equivalent to that of conventional pressure rolls, the nip width must be approximately 15 mm to 20 m1L.
The sponge hardness of the press roll at this time is suitably 300 or less, preferably 20 or less. If the heating wall thickness is thinner, a spongy elastic body with lower rubber hardness should of course be used as the pressure roll.

Although phosphor bronze is preferable for the heating roll cylinder of the present invention, conventionally used aluminum and its alloys, steel, stainless steel, nickel and nickel alloys, nickel-plated copper, chrome-plated copper, and alloys thereof can be used.

The present invention will be explained in more detail below based on Examples.

As a heating roll, it has a diameter of 50 lines and a length of 380m1! , a phosphor bronze roll with a wall thickness of 0.2 mI was used, and 120 mI was used as the heat source.
A 0W infrared lamp was used.

This heating roll has an outer diameter of 50 mm, a length of 380 mm, and a wall thickness of 0.2 mm.
It is obtained by inserting flanges at both ends of a fake phosphor bronze cylinder and welding them. This roll is heated with the above-mentioned lamp, and the heating roll temperature increases from room temperature (22°C) to 160°C.
The warm-up time until reaching C was measured and was 8 to 10 seconds. Further, when the warm-up time of a heating roll having a wall thickness of 2.0 mm was measured using the same infrared lamp, it was 90 to 100 seconds. These warm-up times are fully satisfactory. The pressure roll has a diameter of 55 mm and a length of 370 mm.
1 Silicon sponge-like elastic body Thickness: 15 m 1 L 1 Sponge rubber hardness: 10 ton (measured with Asuka type C hardness tester manufactured by Kobunshi Keiki Seisakusho) was used.

This silicone sponge is made by heating and foaming, and its hardness can be adjusted by changing the foaming ratio.

Nip width 18?1711, load 30kg,
When rotated in contact at a surface speed of 150 degrees/Sec,
Both rolls had sufficient structural strength and did not cause any problems as a fixing device. In addition, 4000/4500 toner was used as the toner, and L-1 paper (both manufactured by Fuji Xerox Co., Ltd.) was used as the support.
It was found that when continuous paper was fed at a rate of 1 sheet, the toner was completely melted and fixed in all copies when the surface temperature of the heating roll was set at 160°C. Further, as an offset prevention liquid at this time, a mercapto-modified polyalkylsiloxane liquid was applied to the heating roll to form an extremely thin mold release film on the surface, but it is also possible to use other mold release agents. It goes without saying that the heating roll of the present invention may be one in which the surface of the heating roll is coated with a heat-resistant release material such as tetrafluoroethylene (trade name: Teflon) for the purpose of preventing offset.

In this case, dimethyl silicone oil (for example, Shin-Etsu Chemical Co., Ltd. KF-96 oil) is generally used as the offset prevention liquid. As described above, the present invention provides a contact heating roller type fixing device comprising a heating roll with a thinner wall and a pressure roll made of a metal core coated with or molded with a sponge-like heat-resistant elastic material. The present invention has the advantage that the long warm-up time, which is a drawback of conventional contact heating roller type fixing devices, can be significantly shortened.

In addition, since the contact pressure between both rolls is small, toner particles are not crushed, resulting in image quality with excellent resolution, and since the pressure roll is soft, it can always follow the surface speed of the heating roll even if the shape changes to some extent. This has the advantage that paper wrinkles are less likely to occur. Furthermore, since the contact pressure is small, the device itself can be simplified and manufacturing costs can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing a conventional contact heating roll type fixing device, FIG. 2 is a chart showing the relationship between the load of a pressure roll using a sponge-like elastic body and the nip width, and FIG. FIG. 2 is an explanatory diagram of one embodiment of the invention.

Claims (1)

[Scope of Claims] 1. A fixing device that fixes a toner image on a recording medium by passing the recording medium carrying the toner image through a nip formed by a heating roll and a roll that is in pressure contact with the heating roll. Pressure roll is sponge rubber hardness 30°
A fixing device comprising the following heat-resistant spongy elastic material. 2. The fixing device according to claim 1, wherein the heating roll has a wall thickness of 0.1 to 2.0 mm.