JPH04174483A - Fusing device - Google Patents

Abstract

PURPOSE:To obtain a high quality image having a high gloss for a full-color image, and a glossless quality image having a deepness for a monochromatic image by setting the surface roughness of a second fixing roller to be smaller than the surface roughness of a first fixing roller. CONSTITUTION:A first fixing roller 6 including a heater 4 and covered with a resilient body layer 5 of silicone rubber for the surface, and a second fixing roller 9 including a heater 7 and covered with a resilient body layer 8 of silicone rubber are disposed vertically to get in contact with each other. A surface roughness R2 of the resilient body layer 8 of the second fixing roller 9 is set at less than 3mum to be smaller than the surface roughness of the resilient body layer 5 of the first fixing roller 6. In a monochromatic mode, monochromatic toner TB/W on a sheet P is fixed by heat of the first fixing roller 6. In a full- color mode, a multi-color toner TF/C on the sheet P is fixed by heat of the second fixing roller 9.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a single-heat roller type fixing device used in a copying machine having a black-and-white (single color) mode and a full color (multicolor) mode.

[Prior Art] In a copying machine equipped with a black-and-white mode and a full-color mode, what is important in terms of image quality is improvement in full-color glossiness. Therefore, in the past, efforts have been made to reduce the surface roughness of the fixing roller to make the surface of the fixed image smooth.

Generally, the amount of toner adhering in full color is larger than in black and white, so in the case of a heat fixing method, offset to the fixing roller is likely to occur, and a material such as silicone rubber with good release properties must be used as the fixing roller.

[Problems to be Solved by the Invention] However, in black-and-white mode, release properties are better than in full-color mode, and on the other hand, low gloss is preferred, so in black-and-white mode and full-color mode, the fixing roller However, there is a problem in which contradictory characteristics are required.

SUMMARY OF THE INVENTION Accordingly, the present invention provides a copying machine in which image fixation is performed on the front and back sides during black-and-white copying and full-color copying, so that fixed images suitable for black-and-white images and full-color images can be obtained respectively. By improving paper separation, we can solve the problem of full-color image quality (
The purpose of this invention is to provide a fixing device that can be used for a variety of purposes.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a method in which a first fixing roller and a second fixing roller whose roller surfaces are each covered with an elastic layer are arranged in pressure contact with each other, and The second fixing roller has a surface roughness of 3 μm or less, which is smaller than that of the first fixing roller.

Further, a first fixing roller and a second fixing roller each having a roller surface covered with an elastic layer are disposed in pressure contact with each other, and the thickness of the elastic layer of the second fixing roller is set to be equal to the thickness of the elastic layer of the first fixing roller. It is preferable that the thickness be larger than the thickness of the layer.

Furthermore, the thickness of the elastic body of the second fixing roller is set to
When the distance is larger than that of the roller, the paper separating means provided at least on the second fixing roller side can be of a non-contact type.

[Function] When the surface roughness of the second fixing roller is set to 3 μm or less, which is smaller than that of the first fixing roller, a full-color image is fixed by the heat of the second fixing roller, and a black-and-white image is fixed by the heat of the first fixing roller.
When the image is fixed by the heat of the fixing roller, a full-color image can be obtained with high gloss, and a black-and-white image can be obtained with a deep, matte image.

In addition, if the thickness of the elastic layer of the second fixing roller is made larger than the thickness of the elastic layer of the first fixing roller, the nip will be shaped along the first fixing roller, which will prevent paper separation during full color fixation. It can improve the properties and prevent the occurrence of uneven gloss.

Further, in this case, by using a non-contact type paper separating means on the second fixing roller side, occurrence of roller scratches can be prevented.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention. In the black and white mode, black and white toner T B7w is transferred from the photoreceptor 1 to the surface (upper surface) of the sheet P and is conveyed downstream by the intermediate conveyance belt 2. , in full color mode, multicolor toners such as Y, M, and C are transferred from the photoreceptor 1 onto the intermediate conveyor belt 2.
After the F/C is transferred and superimposed one on top of the other in sequence, the fixing device 3 used in a copying machine is configured such that it is transferred onto the back surface (lower surface) of the sheet P and conveyed downstream by the intermediate conveyance belt 2. composition.

That is, a first fixing roller 6 has a built-in heater 4 and whose surface is covered with an elastic layer 5 made of silicone rubber, and a heater 7.
A second fixing roller 9 having a built-in body and a surface covered with an elastic layer 8 made of silicone rubber is arranged in pressure contact with each other in the vertical direction, and the surface roughness of the elastic layer 8 of the second fixing roller 9 is R2 is set to 3 μm or less, which is smaller than the surface roughness of the elastic layer 5 of the first fixing roller 6, and the thickness of the elastic layer 8 of the second fixing roller 9 is set to be 3 μm or less. 5, so that the nip N formed between the first fixing roller 6 and the second fixing roller 9 is shaped upward along the first fixing roller 6, and in the black and white mode, the black and white toner T on the sheet P is B/if is fixed by the heat of the first fixing roller 6, and multicolor toner T F/C on the sheet P is fixed by the heat of the second fixing roller 9 in the full color mode. Note that 10 is a separation claw provided in contact with the first fixing roller 6, 11 is a lower chamber loading/unloading log guide plate provided in a non-contact manner so as to double as a separation claw on the second fixing roller 9 side, j2 is a paper ejection roller, 13 is an oil coating roller for the first fixing roller 6, 14 is an oil coating felt for the second fixing roller 9, and 15 and 16 are both thermistors.

In the above configuration, during black and white copying, as shown in FIG.
During full color copying, as shown in FIG. Although fixing is performed using energy, in the present invention, the surface roughness R2 of the elastic layer 8 of the second fixing roller 9 is set to 3 μm or less, and the first fixing roller 6
Since the surface roughness is smaller than the surface roughness of the elastic layer 5 of It will be done.

More specifically, as shown in FIG. 4, full-color toner TF/C generally has poor mold release, and compared to black-and-white toner TB/W, the roughness of the roller surface contributes more to glossiness. In FIG. 4, curve 17F/C represents the case where full color toner is fixed with a Teflon roller, curve 18F/C represents the case where full color toner is fixed with a silicone roller, and curve 17B/W represents the case where black and white toner is fixed with a Teflon roller. The curve IH/1 shows the case where black and white toner is fixed with a silicone roller, and the X mark shows the toner offset. Furthermore, even when comparing a Teflon roller and a silicone roller, the silicone roller, which has excellent oil wettability, has superior mold release properties. Furthermore, when looking at the image quality of Teflon rollers and silicone rollers,
The surface of the image formed by the full color toner T F/C before image fixation is in the state shown in FIG. 5, and when this is fixed with the Teflon roller 17, which has a rigid surface, as shown in FIGS. 6(A) and 6(B). The image surface becomes clearly uneven, with only the convex parts becoming smooth, resulting in uneven gloss (blank).
However, when fixing is performed using an elastic roller 18 such as silicone rubber, the elastic body blends into the surface and produces a uniform gloss, as shown in FIG. 7(A) FB). Therefore, in order to obtain high image quality, an elastic roller such as silicone rubber with excellent mold release properties is suitable for full color fixing, and as in the present invention, the second fixing roller 9 has an elastic layer 8 made of silicone rubber. In addition, by setting the surface roughness of the elastic layer 8 to 3 μm or less, it is possible to obtain a high-gloss, high-quality color image. On the other hand, black and white toners T, W have better releasability than full color toner Tr/C, so as in the present invention, the elastic layer 5 of the first fixing roller 6 is coated with the second fixing roller 9. Elastic layer 8
By using silicone rubber with a surface roughness greater than that of the conventional silicone rubber, it is possible to obtain a black and white image that is matte and has depth.

Further, in the present invention, the elastic layer 8 of the second fixing roller 9
Since the thickness of the elastic layer 5 of the first fixing roller 6 is made larger than that of the elastic layer 5 of the first fixing roller 6, the direction of the nip N can be directed upward, and uneven gloss can be prevented by improving the paper separation property when full color is fixed. can. That is, the second fixing roller 9
If the thickness of the elastic layer 8 is smaller than the thickness of the elastic layer 5 of the first fixing roller 6, the nip N will have a downward shape along the second fixing roller 9, as shown in FIG. becomes disadvantageous. As mentioned above, full color toner T r/C
The releasability of the toner was poor, and as shown in FIG. 9, the contribution of the amount of heat received to the gloss was much higher than that of the black and white toner TB/W.

Therefore, when the nip N is directed downward as shown in Fig. 8, the full color toner ~TF/C remains in the second position even after passing through the nip N.
The amount of heat is also received from the surface of the fixing roller 9, and the ejection roller 12
Until the leading end of the sheet P is sandwiched between the sheets, uneven heat reception occurs at the leading end as shown in FIG. 10, resulting in a problem in the image. Therefore, as in the present invention, by making the thickness of the elastic layer 8 of the second fixing roller 9 larger than that of the first fixing roller 6, the nip N
By oriented upward and improving the paper separation property when full color is fixed, the problem of the occurrence of uneven gloss I9 at the leading edge of the sheet P can be solved.

Furthermore, in the present invention, the first fixing roller 6 is provided with a separating claw 1.
0 is brought into contact with the second fixing roller 9 to perform non-contact separation, but as described above, since paper separation properties are obtained, it is possible to prevent the occurrence of separation jams, and
It is possible to prevent roller scratches on the second fixing port roller 9 from occurring. Incidentally, in the case of the present invention, although the nip N is directed upward, there is no problem with the image quality of black and white images.

It should be noted that the present invention is not limited to the above-mentioned embodiment, and instead of the contact-type separating claw 10, an upper fixing exit guide is provided on the first fixing roller 6 side, as shown in FIG. 11, for example. It goes without saying that the plate 11' may be used as a non-contact paper separating means, and that various other modifications can be made without departing from the gist of the invention.

[Effects of the Invention] As described above, according to the fixing device of the present invention, the first fixing roller and the second fixing roller are arranged in pressure contact with each other, and the first fixing roller and the second fixing roller are arranged in pressure contact with each other, and Since the surface roughness of the second fixing roller is made smaller than that of the first fixing roller, it is possible to obtain full-color images with high gloss and high image quality, and to obtain good black-and-white images with no gloss and depth. In addition, by making the thickness of the elastic layer provided on the surface of the second fixing roller larger than the thickness of the elastic layer provided on the surface of the first fixing roller, the paper separation property during full color constant fixing can be improved. By using a non-contact method for at least the paper separating means on the second fixing roller side, it is possible to prevent the occurrence of heat-receiving image gloss unevenness. It has excellent effects such as being able to prevent this and extend its life.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the fixing device of the present invention, FIG. 2 is a schematic diagram showing the fixing state in black-and-white copy mode, and FIG. 3 is a schematic diagram showing the fixing state in full-color copy mode. Figure 4 is a diagram showing the relationship between fixing roller surface roughness and glossiness, Figure 5 is a sectional view showing the state of the image surface before fixing with full-color toner, and Figure 6 is a diagram showing the state of a full-color image fixed with a Teflon roller. (5) is a cross-sectional view, (B) is a partial surface view, and Figure 7 shows a full-color image fixed with an elastic roller; (5) is a cross-sectional view, and (B) is a partial surface view. The surface view, Figure 8 is a schematic diagram assuming a state where the nip is facing downward, Figure 9 is a diagram showing the relationship between the amount of heat received and glossiness, and Figure 1O is a diagram showing the unevenness of the leading edge of a full-color image fixed on a sheet. The explanatory diagram, FIG. 11, is a schematic diagram of another embodiment of the present invention. 5... Elastic body layer, 6... First fixing roller, 8...
Elastic layer, 9... second fixing roller, 11... unloading fixing guide plate (non-contact type paper separation means).

Claims (3)

[Claims] (1) A first fixing roller and a second fixing roller whose roller surfaces are each covered with an elastic layer are arranged in pressure contact with each other, and the surface roughness of the second fixing roller is set to 3 μm or less, and the surface roughness of the first fixing roller is set to 3 μm or less. A fixing device characterized by having a configuration in which surface roughness is smaller than surface roughness. (2) A first fixing roller and a second fixing roller whose roller surfaces are each covered with an elastic layer are placed in pressure contact with each other, and the thickness of the elastic layer of the second fixing roller is determined by the elasticity of the first fixing roller. A fixing device characterized in that it has a structure that is larger than the thickness of a body layer. (3) The fixing device according to claim (2), wherein the paper separating means provided at least on the second fixing roller side is of a non-contact type.