JPH05188813A - Image fixing device - Google Patents

Abstract

PURPOSE:To decrease the difference in the glossiness between the rear and front of toner images by setting the coated amt. of oil at the time of fixing the images to both surfaces of a recording material on a pressurizing roller side larger the coated amt. on a fixing roller side. CONSTITUTION:Oil applying means 3A, 3B are so constituted as to scoop up the methyl penyl silicone oil at the silicone oil 14 housed in a container 13 by upper and lower supply rollers 151, 152 rotating in arrow (d), (e) directions and to apply the oil onto the surfaces of silicone rubber layers 6, 9 of the fixing roller 1 and the pressurizing roller 2. While the coated amt. of the silicone coil 14 is adjusted by a coated amt. adjusting blade 10 pressed to the upper supply roller 151, the oil is applied on the pressurizing roller 2 in the coated amt. larger than the coated amt. of the oil on the fixing roller 1. The difference in the coated amt. of the oil on the fixing roller 1 and the pressurizing roller 2 is intended to decrease the difference in the glossiness between the rear and the front at the time of fixing on both sides.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image fixing apparatus for fixing a toner image transferred on a recording material in an image forming apparatus, and more particularly to an apparatus for fixing the toner image on both sides of the recording material. It is about.

[0002]

2. Description of the Related Art In a conventional fixing device of an image forming apparatus, when a recording material P carrying an unfixed toner image T is conveyed in a direction of an arrow a as shown in FIG. 5, a heater is provided therein. Then, the fixing roller 1 and the pressure roller 2 which rotate in the direction of the arrow b pass the recording material P while sandwiching the recording material P at the pressure contact portion. At this time, the toner image T on the recording material P is melted by receiving heat and pressure from the fixing roller 1 and the pressure roller 2, and is fixed on the recording material P.

In such an image fixing device, in order to prevent molten toner from adhering to the surface of the fixing roller 1,
An oil application means 3 for applying silicone oil 14 acting as a release agent to the surface and a cleaning means 4 for cleaning the surface are provided.

The oil applying means 3 is constantly in contact with the fixing roller 1 or is in contact with the fixing roller 1 by an amount substantially corresponding to the size of the recording material P when passing through the recording material P. Apply. The amount of silicone oil applied at this time is 0.01-0.
It is about 20 [g / A4 recording material]. As a method for measuring the amount of oil applied per sheet of recording material, first, 50 sheets of the recording material are passed through the fixing device without applying oil to measure the total weight W1, and then the amount of oil When the same recording material is applied to the above fixing device in the coated state,
The total weight W2 when the sheets are passed is measured. Then, the total weight W1 of the recording material to which the oil is applied is subtracted from the total weight W2 of the recording material to which the oil is applied, and this is divided by 50 of the number of recording materials.

As described above, in the fixing device of the image forming apparatus, it is necessary to prevent the offset of the molten toner to the fixing roller by applying the release agent. Since the toner T in which various types of magenta, cyan, and black are laminated is fixed on the recording material P, it is necessary to reliably prevent the offset. In other words, in order to reproduce a color close to that of the original document, it is necessary to heat and melt the toners T in multiple layers to mix the colors. For that purpose, a toner having a low softening point (that is, a low melting point) and a sharp melt toner is used. Therefore, the offset is likely to occur.

As described above, the sharp-melt toner is melted to an extremely low viscosity state, and the toner layer is thickened by laminating a plurality of colors to form a full-color image. However, the fixing temperature range (the temperature range in which proper fixing can be performed) differs due to the difference in the meltability caused by the difference in the pigments contained in each color toner. Therefore, the common fixing temperature range becomes narrower than that of single-color fixing, and offset tends to occur easily.

Therefore, conventionally, it is difficult to use a fluororesin-based material such as Teflon (trade name) used in a black-and-white image fixing device as the surface layer material of the fixing roller in the fixing device of the color image forming apparatus. Silicone rubber or silicone resin is used. This is because a release agent such as silicone oil is indispensable for preventing the offset of the color toner fixing described above, and it is necessary to apply this silicone oil to the surface layer of the fixing roller. This is because the wettability of is extremely poor and application is difficult.

On the other hand, as the surface material of the pressure roller, the same material as that of the black-and-white image fixing device can be used in an apparatus for forming a color toner image on only one surface of the recording material P as described above. It cannot be used in an apparatus that forms the color toner image on both sides of P. this is,
For the following reason, first, the recording material P
An apparatus for forming images on both sides of will be described.

In such an apparatus, the recording material P, which has been subjected to the fixing process as described above on one surface of the recording material P, is
The recording material P is conveyed to a toner image forming step position through a conveyance path (not shown), and the back surface (the surface on which the toner image is not formed) of the surface of the recording material P on which the toner image has already been formed (hereinafter referred to as surface A). In some cases, a toner image is formed again on the surface B), and the fixing process described above is passed again to complete the image formation on both sides of the recording material P. Hereinafter, such a process is referred to as double-sided fixing.

A characteristic of such double-sided fixing is that, at the time of double-sided fixing, the toner image on the A side contacts with the pressure roller 2 which is in a heated state sufficient to melt the toner, so that the liquid phase is again transferred from the solid phase. Phase is converted into a phase, and an offset easily occurs on the surface of the pressure roller. Therefore, as with the fixing roller, the surface material of the pressure roller needs to be made of a material such as silicone rubber or silicone resin, which has good wettability to the release agent (here, silicone oil).

[0011]

However, the above-mentioned conventional example has the following problems. First, when such double-sided fixing is performed with a conventional image fixing device,
If the oil application means 3 is always in contact with the fixing roller 1, the silicone oil 14 is indirectly applied to the pressure roller side, but when the recording material P passes, the silicone oil 14 is applied to the recording material P side. Therefore, the application of the silicone oil 14 to the pressure roller 2 side is cut off, and the peripheral portion of the fixing roller from the tip of the A side of the recording material P (for example, the pressure roller has a diameter of 40 mm). If you do 40π
mm) and thereafter, the silicone oil is no longer supplied, and A
The toner T on the surface easily becomes offset with respect to the pressure roller 2.

Further, when the recording material P is passed, the oil applying means 3 is brought into contact with the surface of the fixing roller 1 by an amount corresponding to the size of the recording material P so that the silicone oil 1 is applied to the surface of the fixing roller 1.
When the method of applying No. 4 is used, the oil is hardly supplied to the pressure roller 2 side, and it becomes extremely weak against the offset on the pressure roller side during double-sided fixing.

Next, as another problem at the time of double-sided fixing, there is a problem that the glossiness of the toner image is different between front and back. This is because the surface B passes through the fixing process only once in both sides, but the heat energy supplied is almost doubled because the side A passes twice (substantially before the second passage). (Because it is cooled in the transfer process, it does not double.)
it is conceivable that.

As a countermeasure for this, a method of lowering the surface temperature of the pressure roller side on both sides than that of the fixing roller side can be considered, but it is quite necessary to detect the surface temperature of each roller and then control the temperature. It takes time and is not practical.

The present invention solves the above-mentioned problems, and by applying silicone oil as a release agent to a fixing roller and a pressure roller whose surface layer is made of a silicone rubber material, a double-sided fixing is performed. Double-sided image that can prevent toner offset to the pressure roller of the device (extend the durable life of the device) and reduce the difference in the glossiness of the toner image (image uniformity) with a simple device configuration. It is intended to provide a fixing device.

[0016]

SUMMARY OF THE INVENTION According to the present invention, the above object is to provide a fixing roller and a pressure roller whose surface layer is made of silicone rubber and which has a heating element therein so as to be in pressure contact with each other. In an image fixing device that performs fixing by heating and pressing while sandwiching and transporting a recording material carrying a deposited image between the pressure contact portions of the fixing roller and the pressure roller, the recording material is brought into contact with the respective surfaces of the fixing roller and the pressure roller. A silicone oil applying means for applying silicone oil is provided, and the amount of oil applied by the silicone oil applying means when fixing an image on both sides of the recording material is the amount applied to the pressure roller side to the fixing roller side. This is achieved by setting the amount to be larger than the coating amount.

[0017]

According to the present invention, since the silicone oil is applied to not only the fixing roller but also the pressure roller by the silicone oil applying means, the offset in the pressure roller is surely prevented. Further, when the image is fixed on both sides of the recording material, the amount of oil applied on the pressure roller side is set to be larger than that on the fixing roller side. When the image on the front surface of the recording material comes into contact with the pressure roller during fixing of the rear surface of the recording material and receives heat energy again, the heat energy is absorbed by the oil applied more than the fixing roller and receives excessive heat energy. Never. As a result, the difference in glossiness between the front surface and the back surface of the recording material is eliminated.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment and a second embodiment of the present invention will be described with reference to the drawings.

<First Embodiment> First, a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic configuration diagram of an image fixing device according to a first embodiment of the present invention. As shown in FIG. 1, the image fixing device includes an oil applying unit 3A for applying silicone oil as a release agent to the fixing roller 1.
And a cleaning means 4 for cleaning the roller surface. Further, an oil applying means 3B for applying silicone oil to the pressure roller 2 is also provided on the pressure roller 2 side.
And a roller cleaning means 4 for cleaning the surface of the pressure roller 2.

The fixing roller 1 and the pressure roller 2 each have an outer diameter of 40 mm in which the core layers 5 and 8 made of aluminum are coated with the silicone layers 6 and 9, and the material of the rubber layers 6 and 9 is dimethyl silicone rubber (Toray). (Manufactured by Co., Ltd.) and cured as single-layer rollers having a thickness of 3 mm and 1 mm, respectively, and then immersed in a 200 ° C. oil bath of methylphenyl silicone oil (KF54-450cs, manufactured by Shin-Etsu Chemical Co., Ltd.). The rubber is pre-impregnated with oil. Further, halogen heaters 7 and 11 as heating sources are provided in the core metal 5 of the fixing roller 1 and the core metal 8 of the pressure roller 2, respectively, and the temperature of the pressure roller 2 is brought into contact with the thermistor 12a. Detected by the heater 7,
11 is intermittently controlled to fix the fixing roller 1 and the pressure roller 2.
The surface temperature of the is constantly maintained at about 170 ° C.

The roller cleaning means 4 adheres to the surface of the silicone rubber layers 6 and 9 of the fixing roller 1 and the pressure roller 2 (toner resin, coloring material, toner external additive such as silica and alumina, and various components of paper). ) And the roller surface are polished and cleaned. Here, the cleaning member is a fibrous cleaning web that is a conventional cleaning member that is pressed into contact with the fixing roller 1 and the pressure roller 2, and at least the cleaning surface side is nickel-plated.

The oil applying means 3A and 3B are composed of a methylphenyl silicone oil (KF-54 manufactured by Shin-Etsu Chemical Co., Ltd., viscosity 450 cs) as the silicone oil 14 contained in the container 13 which is rotated in the directions of arrows d and e. It is adapted to be drawn up by the supply rollers 151 and 152 and applied to the surfaces of the silicone rubber layers 6 and 9 of the fixing roller 1 and the pressure roller 2. The application amount of the silicone oil 14 is adjusted by the application amount adjusting blade 10 which is brought into contact with the upper supply roller 151, and is 0.03 g per A4 recording sheet for the fixing roller 1. Is applied (actually 0.01 to 0.20 g, preferably about 0.02 to 0.10 g).

The amount of oil applied to the pressure roller 2 is larger than the amount of oil applied to the fixing roller 1 and is 0.
08 g is applied (actually 0.03 to 0.30 g, preferably about 0.03 to 0.20 g).

The difference in the amount of oil applied to the fixing roller 1 and the pressure roller 2 is to reduce the difference in glossiness (gloss) between the front and back surfaces during double-sided fixing. That is, FIG.
As can be seen from the relationship between the oil application amount and the glossiness as shown in (4), the glossiness can be decreased by increasing the oil application amount. For example, the fixing roller 1
The same amount of oil applied to the pressure roller 2 is 0.03.
The difference in glossiness (gloss) between the front and back surfaces was about 27 when each g was applied, but when the oil application amount was 0.03 g on the fixing roller 1 side and 0.08 g on the pressure roller 2 side, It was possible to reduce the difference in glossiness (gloss) to about 20.

The decrease in glossiness when the amount of oil applied increases
It is considered that the heat energy to be supplied to the toner layer is absorbed by the oil, so that the heat energy supplied to the toner is substantially reduced.

Here, for the measurement of glossiness, a gloss checker IG-320 manufactured by HORIBA, Ltd. was used, and a yellow solid image was used as a sample.

The oil applying means 3A, 3B as described above are
The silicone oil 14 is applied to the fixing roller 1 and the pressure roller 2 at different timings. For example, the means 3A for applying oil to the fixing roller 1 is the recording material P.
It is desirable to apply the silicone oil only to a position substantially corresponding to the contact portion with the recording material P when passing through the nip portion between the fixing roller 1 and the pressure roller 2. This coating operation is performed by moving only the oil coating unit 3A or the supply roller 151 by operating means (not shown) to bring the fixing roller 1 and the supply roller 151 into contact with each other. Further, as another application operation, even when the supply roller 151 and the fixing roller 1 are constantly in contact with each other, the supply roller 15
This is possible by intermittently controlling the rotational drive of No. 1.

The means 3B for applying oil to the pressure roller 2 is
The application timing is adjusted by the same method as the operation of the oil applying unit 3A for the fixing roller 1 described above. Here, in the case of fixing only one side of the recording material P (when there is no toner T on the side of the pressure roller 2 of the recording material P), silicone oil application is not performed, and only in the case of double-sided fixing, the surface of the pressure roller 2 is fixed. A silicone oil application operation for a length substantially corresponding to the contact position of the recording material P is performed.

Next, the operation of the above-mentioned double-sided fixing device will be described. The recording material P carrying the unfixed toner image T on the A side is conveyed by a conveying device (not shown) in the direction of arrow a in FIG. 1, and is driven by a driving device (not shown) as indicated by arrow b in FIG. Between the fixing roller 1 and the pressure roller 2 which are rotated in the same direction, and the heat and pressure supplied from the halogen heaters 7 and 11 via the fixing roller 1 and the pressure roller 2 respectively cause the recording material P to move. The unfixed toner image T is fixed on. At this time, the oil is applied to the surface of the fixing roller 1 at a timing substantially corresponding to the contact length with the recording material P, but the oil is not applied to the pressure roller 2 side. The recording material P, which has been fixed to the one side (A side) in this way, is turned upside down manually or by a conveying device (not shown), and this time, the unfixed toner image T is transferred to the remaining one side (B side).
Similarly to the A surface, it is conveyed by a conveying device (not shown) and is rotated by a driving device (not shown) in the direction of arrow b in FIG. 1 between the fixing roller 1 and the pressure roller 2. It is pinched again and the double-sided fixing is completed. At this time, the oil is applied to the fixing roller 1 in the same manner as the surface A, and the oil is applied to the pressure roller 2 so as to correspond to the recording material P.

As described above, according to this embodiment, since the silicone oil is applied not only to the fixing roller side but also to the pressure roller side, the offset on the pressure roller can be surely ensured even in double-sided image formation. Can be prevented. Further, since the amount of silicone oil applied to the pressure roller is set to be larger than that applied to the fixing roller, there is no difference in glossiness between the front surface and the back surface of the recording material.

In the present embodiment, the silicone oil application means may be kept in contact with the respective rollers by a small amount of silicone oil applied to perform double-sided fixing. However, the amount of oil applied to the pressure roller 2 at the time of double-sided fixing at this time is also set to be larger than the amount of oil applied to the fixing roller 1.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIGS. The same parts as those of the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the first embodiment, the oil applying means 3A, 3B
As an example, oil is supplied by bringing a rotationally driven member such as the supply roller 151 into contact with the fixing roller 1 or the pressure roller 2, but in the present embodiment, the oil is fixed to the metal plate 154 as shown in FIG. The oil absorber 153
It differs from the first embodiment in that the oil supply to the fixing roller 1 and the pressure roller 2 is controlled by contacting and separating at the same timing as the supply roller 151 as described above.

Also at this time, the contact area of the oil absorber 153 with the pressure roller 2 is made larger than that of the fixing roller 1 side, or the material itself of the oil absorber 153 is changed so that the pressure roller 2 side is contacted. The oil application amount is adjusted to be larger than that on the fixing roller 1 side.

The oil absorber 153 is a heat-resistant material such as fluoropore (trade name) and felt made of porous fluororesin, and the oil 14 in the container 13 is absorbed therein by the osmotic pressure, and also the roller. A suitable amount of oil exudes at the contact area with.

Such an oil applying means serves as both the oil applying means and the roller cleaning means by preliminarily impregnating the roller contact member or the cleaning web of the roller cleaning means 4 as shown in FIG. 4 with silicone oil. It is also possible to control the oil application by using the device having the configuration and contacting and separating at the same timing as described above. Even in this case, the amount of oil applied to the pressure roller 2 is made larger than the amount of oil applied to the fixing roller 1.

If the amount of oil supplied to the pressure roller during double-sided fixing is larger than that on the fixing roller side, the oil applying means is not limited to that described above, and other means may be used. Further, the configuration of the oil applying means may be performed by combining various methods described above.

The fixing device according to the present invention is particularly effective for double-sided fixing of a full-color image in which toner is mixed during fixing, but is also effective for double-sided fixing of a monochrome image fixing device.

[0039]

As described above, according to the present invention,
Silicone oil applying means is provided so as to apply silicone oil to both the fixing roller and the pressure roller, and the amount of oil applied to the pressure roller side is larger than the amount of oil applied to the fixing roller side during double-sided image fixing. Since the oil is applied in this way, it is possible to prevent the offset of the toner to the pressure roller during double-sided image fixing and extend the service life of the device, and reduce the difference in glossiness between the front and back of the toner image. Image uniformity can be achieved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a schematic configuration of a device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the amount of oil applied to the fixing roller and the glossiness at that time in the apparatus of FIG.

FIG. 3 is a cross-sectional view showing a schematic configuration of a second embodiment device of the present invention.

FIG. 4 is a cross-sectional view showing a schematic configuration of another embodiment of the apparatus of the present invention which also serves as an oil applying means and a cleaning means.

FIG. 5 is a sectional view showing a schematic configuration of a conventional device.

[Explanation of symbols]

 1 fixing roller 2 pressure roller 3A, 3B silicone oil applying means

Claims (1)

[Claims] 1. A fixing material and a pressure roller having a surface layer formed of silicone rubber and having a heating element therein are arranged in pressure contact with each other, and a recording material carrying an unfixed image is applied to the fixing roller and the pressure roller. In an image fixing device that performs fixing by heating and pressing while being nipped and conveyed at a pressure contact portion of a roller,
The fixing roller and the pressure roller are provided with a silicone oil application unit that comes into contact with the respective surfaces to apply silicone oil, and the amount of oil applied by the silicone oil application unit when fixing images on both sides of the recording material is An image fixing device characterized in that the application amount on the pressure roller side is set to be larger than the application amount on the fixing roller side.