JPH0548204Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to a release agent coating device for preventing toner offset used in fixing units of electrostatic recording devices, electrophotographic devices, etc. It is.

(Prior Art) First, a heat roller fixing system showing the general structure of a fixing device will be explained using FIG. 6. As is well known, a toner image formed on a recording material (plain paper, etc.) by the so-called electrostatic recording method or electrophotographic method is transferred between the pair of fixing rollers 1 and 6 to the recording material in the final process. The thermoplastic toner is melted by the heat from the heating source 7 and fixed on the recording material as the thermoplastic toner passes through the recording material while being conveyed under a narrow pressure. Note that 8 is a thermistor that detects the roller surface temperature. In such a fixing device, even if sufficient toner melting is achieved, a small portion of the toner image is transferred onto the roller due to thermal or electrostatic action. This is generally called an offset phenomenon, and causes defects such as the offset toner being carried by the roller and staining the surface of the thermistor or being transferred as an unnecessary image onto the next recording material. Therefore,
Generally, in order to reduce toner offset to the roller, a release agent applicator 9 is used to apply silicone.
It is common practice to apply a release agent such as oil to the roller. Many methods have been proposed and put into practice for this coating method, but
One coating technique that is smaller and easier to maintain is one that uses a heat-resistant porous resin member. A conventional example of this method is shown in FIG. This is made by stretching a heat-resistant resin such as a fluororesin to substantially form fibers, and impregnating the pores created between the fibers with a mold release agent such as silicone oil. This porous member 2 is held by a heat-resistant resin holder 3 as shown in FIG. 5, and brought into contact with a fixing roller or a pressure roller with appropriate pressure by a spring member 5. The mold release agent impregnated into the porous resin usually has a lifespan of 1000cs at room temperature.
Due to its high viscosity, it is retained in the pores, but when the fixing roller etc. are heated, the release agent is also heated through the porous resin, reducing the viscosity (approximately 1/ (down to nearly 10), the release agent migrates to the roller surface due to capillary action and is applied to the roller.

Therefore, the entire amount of the mold release agent impregnated in the porous resin should be constantly applied to the roller, but in actual use, it is found that at the initial stage of application, the release agent is not completely applied. The discharge amount is excessively high, but then it decreases dramatically. For example, when A4 size recording material is used continuously, the amount of release agent applied to the roller becomes insufficient after several hundred sheets, and as a result, the image becomes smudged. The disadvantage was that it caused a problem. At the same time, an excessive amount of release agent is discharged in the early stage of coating, causing excess release agent to flow along the roller surface and stain the fixing device and the recording material.

(Purpose of the invention) The purpose of the invention is to eliminate the drawbacks of the conventional method, to reduce the amount of release agent discharged to an appropriate amount, to reduce offset toner over a long period of time, and to prevent excessive bleeding at the initial stage of application of the release agent. It is an object of the present invention to provide a release agent coating device capable of preventing staining of a recording material or the like due to release.

(Summary of the invention) The present invention, which achieves the above object, uses a release agent applicator that applies a release agent to a fixing rotating body. The porous member is characterized by having a resin holder that integrally holds the plurality of porous members.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

As mentioned above, in the conventional configuration (Fig. 5), the discharge amount of the mold release agent oozes out excessively at the beginning, but then it rapidly decreases. However, we conducted a study on how to maintain the appropriate amount of release agent discharged from the porous member over the long term. When observing how the mold release agent is discharged from the porous member, it was found that the release agent is discharged from the porous member not only from the surface that is in contact with the heated roller, but also by heat conduction from the roller. It was found that this was also done from the side that was not in contact with the roller.

FIG. 1 shows an embodiment of the present invention, in which a porous member 2 is divided into two parts 2a and 2b, and the divided porous members 2a and 2b have a gap d of 1 mm or less between them. It is fitted into a heat-resistant resin holder 3 and integrated. Incidentally, such a configuration in which two or more porous members are arranged on a roller is also described in, for example, Japanese Patent Publication No. 58-37541. However, in this case, the porous members divided as described above were separated by 1 mm.
Below (there may be slight differences depending on the viscosity of the mold release agent, but
According to our experiments, by placing the mold release agent close to each other with a gap d (approximately this value), the mold release agent discharged from inside the porous member is temporarily retained in the gap by a kind of capillary phenomenon. Ru. As the mold release agent is gradually discharged from the porous member, the amount of mold release agent held in the gap increases, and as a result, due to the relationship between the mold release agent's own weight and surface tension, it gradually hits the roller surface. Appropriate amounts will be applied. This integrated application member is placed in pressure contact with the fixing roller by a spring member 5. Incidentally, the application member is removable along the guide rail 4 of the frame of the fixing device main body.

With this configuration, the surface area of the porous member can be increased without changing its volume, and as a result, the release agent is also discharged from the sides of the porous member, resulting in a larger amount of release agent than the conventional example. The mold agent will be discharged. In addition, porous members may be
By placing them close to each other with a gap of less than mm, as mentioned above, excessive seepage can be prevented, and as a result, the release agent can be applied for a longer period of time than in conventional methods, so the long-term offset It has also become possible to prevent this from happening. According to the experimental results of the inventors, with the conventional type, the recording material is smeared due to excessive discharge of release agent up to around 100 sheets in the initial stage of application, and offset toner is observed after around 1000 sheets due to insufficient amount of release agent discharged. However, in this example, there was no staining of the recording material due to excessive release agent, and the rapid increase in toner amount due to offset due to insufficient amount of release agent discharge was reduced to about several thousand sheets. Note that the porous member 2 includes:
For example, a heat-resistant polytetrafluoroethylene resin porous body is used.

In addition, in Fig. 1, the porous member is divided into two parts, but this division may be divided into two or more parts, and on the contrary, the surface area increases, The amount of release agent discharged increases.

Furthermore, in addition to dividing the roller in the circumferential direction along the length of the roller, it may also be divided along the axial direction of the roller, or it may be divided at a certain appropriate angle with respect to the roller. do not have.

The above dividing method will be shown below as another embodiment.

FIGS. 2 and 3 show the porous member 2 divided into three pieces (FIG. 2) or more in the circumferential direction of the roller along the longitudinal direction of the roller. Further, FIG. 4 shows the porous member 2 divided into a plurality of pieces in the axial direction of the roller. In any case, by increasing the number of divisions of the porous member, the surface area will increase even if the volume is the same, and as a result, the discharge of mold release agent will also increase.

The release agent coating device described in this embodiment is not limited to a heated fixing roller, but can be applied to a fixing rotating body including an overpressure roller and other belt-shaped members.

(Effects of the invention) As explained above, according to the invention, the volume of the porous member can be reduced by dividing the heat-resistant porous member impregnated with a mold release agent into a plurality of parts and arranging them close to each other. It is possible to increase the surface area and discharge more mold release agent without changing the material. Preferably, by placing the divided porous members close to each other with a gap of 1 mm or less, excessive discharge of the mold release agent can be suppressed, and an appropriate amount of mold release agent can be supplied to the roller. The mold release agent can be applied over a long period of time, resulting in the effect of reducing offset.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an embodiment of the present invention;
3 are sectional views showing other embodiments of the present invention,
FIG. 4 is a perspective view showing still another embodiment of the present invention, FIG. 5 is a sectional view showing a conventional release agent coating device, and FIG. 6 is a schematic diagram showing a general example of a roller type fixing device. . 1, 6...Fixing roller, 2...Porous member,
3...Heat-resistant resin holder, 5...Spring material, d...
…gap.

Claims (1)

[Claims for Utility Model Registration] A porous member that comes into contact with the fixing rotor and is impregnated with a release agent, a resin holder that holds this porous member, and a pressing means that presses the resin holder against the fixer rotor. A release agent application device that applies a release agent impregnated in a porous member to a fixing rotating body, the porous member being divided into a plurality of parts arranged close to each other with a gap of 1 mm or less. A mold release agent coating device characterized by having a configuration in which the surface area is increased.