JPH09171313A - Fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the generation of wrinkles in envelope, while satisfying self-stripping performance and further, to prevent the wearing of the elastic layer of a fixing roll for prolonging the life. SOLUTION: When a strain in the circumferential direction of the elastic body 3 of the fixing roll 1 on a side coming into contact with the unfixed toner image of a recording material 6 is defined as εh, a strain in the circumferential direction of the elastic body 4 of the other fixing roll 2 is defined as εp and εh-εp is defined as Δε, the relations of εh>=0.0583(Δε)<4> -0.6(Δε)<3> +2.1917(Δε)<2> -3.65(Δε)+6, εh<6%, Δε<=3% are satisfied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat and pressure type fixing device of an image information recording device such as a copying machine, a printer, a facsimile, etc., in which an unfixed toner image on a recording material is fixed by contact heating.

[0002]

2. Description of the Related Art As a conventional fixing device, as shown in FIG. 5, recording in which an unfixed toner image is formed in a pressure contact region of a pair of fixing rolls (heating roll and pressure roll) which rotate while being in pressure contact with each other. A heating and pressurizing type fixing device is widely used in which a paper is inserted to fix an unfixed toner image by contact heating.

In the figure, reference numeral 30 is a heating roll, 4
0 is a pressure roll. The heating roll 30 is formed by forming a relatively thick elastic layer 32 such as silicone rubber on the surface of a hollow roll 31 made of a metal having a high thermal conductivity such as aluminum. Inside the hollow roll 31, a halogen is used as a heating source. The halogen lamp 33 is arranged on the surface of the heating roll 30 by a signal of a temperature sensor (not shown) provided on the surface of the heating roll 30, and the halogen lamp 33 is turned on / off by a temperature control circuit (not shown) to adjust the heating roll 30 to a certain temperature. . Further, in order to prevent a phenomenon (hereinafter referred to as offset) in which a part of the unfixed toner 51 on the recording paper 50 is transferred to the heating roll 30 during fixing, a fixed amount of silicone oil is applied to the heating roll 30. An oil supply device (not shown) for supplying the oil is provided.

On the other hand, the pressure roll 40 is a core metal roll 41.
The surface is coated with a coating layer 42 of Teflon (trademark of DuPont). In this roll configuration, the elastic layer 32 of the heating roll 30 is elastically deformed to cause the roll 3 to roll.
A pressure contact portion (hereinafter referred to as a nip portion) 35 of 0, 40 is formed. The unfixed toner image is passed through the nip portion 35,
It is fixed by pressure and heat energy.

In this way, the roll (heating roll) 30 on the side which comes into contact with the unfixed toner image is elastically deformed and the nip portion 3 is formed.
The roll configuration of No. 5 does not require a peeling claw even at the time of color-fixing the recording paper 50 on which a large amount of toner is thin and the paper 50 having a weak elasticity is fixed, and at the exit of the nip portion 35, Peeling can be performed without using a peeling device (hereinafter, this is referred to as self-stripping), so that the recording paper 50 on which a large amount of three-color (cyan, magenta, and yellow) toners are placed is sufficiently colored to be a target color. It is used to fix a color image that is fused and mixed in color and fixed.

This is because the adhesive force at the interface between the molten toner and the surface of the heating roll 30 is not simply determined by the interfacial chemical properties of the materials, but the heating roll 30 due to elastic deformation.
Due to the fact that it is greatly affected by surface distortion. That is, the heating roll 30 having surface distortion in advance.
This is a phenomenon in which the adhesion of the toner and the surface of the heating roll 30 decreases when the surface of the molten toner is released from the state where the molten toner is in contact with the surface.

More specifically, the surface of the heating roll 30 is covered with a material that can be relatively easily elastically deformed by an external load to generate distortion, for example, a heat resistant elastic body such as silicone rubber or fluororubber. Nip 35
Is fixed while being distorted in the nip part 3
At the moment when the distortion is released at the 5th exit, the adhesive force between the toner and the surface of the heating roll 30 is rapidly reduced, and in addition, the discharge direction of the recording paper 50 at the exit of the nip portion 35 is directed toward the pressure roll 40 side. It is that it is easily stripped. Therefore, the larger the strain amount (ε) of the heating roll 30 is, and the more the discharge direction of the recording paper 50 at the exit of the nip portion 35 is toward the pressure roll 40 side, the higher the self-stripping capability is.

[0008]

However, in the structure shown in FIG. 5, since the pressure roll 40 is not elastically deformed at all, as the load increases, only the amount of surface strain of the heating roll 30 increases, and the pressure roll 40 increases. There is a technical problem that the difference in speed between the elastic layer 32 and the elastic layer 40 becomes large and wear of the elastic layer 32 is promoted. Therefore, in order to solve such technical problems,
As shown in FIG. 6, it is proposed that the pressure roll 40 is provided with an elastic layer 43 which is relatively thinner than the elastic layer 32 of the heating roll 30, and the pressure roll 40 also has a surface strain amount smaller than that of the heating roll 30. (For example, JP-A-63-259)
582). With this configuration, when the load is increased, the amount of surface strain corresponding to both the heating / pressurizing rolls 30 and 40 increases, so that the speed difference between the rolls 30 and 40 remains at a certain amount and wear of the heating roll 30 is reduced. It has the advantage that it can be suppressed and a wider nip area can be obtained.

However, the roll-type fixing device shown in FIG. 6 has a technical problem that when an envelope is used as the recording paper 50, so-called "wrinkles" which are not generated in the normal recording paper 50 are likely to occur. . The configuration of the envelope is considered to be almost the same as that of two sheets of recording paper glued at the three corners, and is conveyed at different speeds due to the distortion of the rolls on the side where the upper and lower sheets are in contact with each other in the nip region. This gap between the upper and lower sheets of paper cannot be escaped by the gluing section, resulting in wrinkles. If the three corners are not glued, wrinkles are unlikely to occur even on two recording sheets.

In order to solve such a technical problem,
As shown in FIG. 7, the elastic layers 32 of both rolls 30, 40,
It has been proposed that the wrinkles of the envelope be prevented by making the thicknesses of 42 equal and forming the nip portion 35 substantially flat so that the rolls 30 and 40 have the same distortion amount (for example, a special feature). Hei 7-7233). However, in the roll configuration of FIG. 7, the action of ejecting the recording paper 50 at the exit of the nip portion 35 does not face the pressure roll 40 side, so the ejection behavior of the recording paper 50 becomes unstable,
When the recording paper 50 on which a large amount of toner is thin and the paper thickness is thin and the color of the recording paper 50 is weak, self-stripping becomes difficult, and a technical problem that an auxiliary peeling claw is required is newly generated. .

Further, regarding the amount of the silicone oil used as the release agent supplied to the heating roll 30, the following technical problems occur. That is, in the past, in a fixing device for fixing and self-stripping a sufficiently melted color image, an oil layer is required between the molten toner and the interface of the heating roll 30 in the nip region, so that a large amount of silicone oil is applied to the heating roll 30. A large amount of silicone oil was transferred to the recording paper 50 after being supplied to the recording paper 50 after fixing. In this case, the transferred oil is the recording paper 5 after the operator has fixed it.
It was very uncomfortable when handling 0. Therefore,
No discomfort with the silicone oil on the recording paper 50 after fixing (5 mg or less per A4 size recording paper)
When the supply amount of the oil supply device is reduced up to this point, a considerable amount of distortion of both rolls 30 and 40 is required, and the technical problem of abrasion of the elastic layers 32 and 42 occurs as in the configuration of FIG.

As described above, the "self-stripping performance", the "wrinkle of the envelope" and the "wear of the elastic layer" are caused by the strain amount of the heating roll 30 (εh), the strain amount of the pressure roll 40 (εp) and It has been difficult to provide a fixing device that is entangled in a complicated manner due to the difference in strain amount (εh−εp) of both rolls and that satisfies any allowable range.

The present invention has been made in order to solve the above technical problems, and is small even when color-fixing a recording material on which a large amount of toner is placed and the thickness of the paper is thin and the paper is weak. With respect to the amount of release agent supplied, while satisfying the self-strip performance that the recording material can be peeled off without using any peeling device on the exit side of the nip portion, the occurrence of wrinkles in the envelope is suppressed and the elastic layer of the fixing roll is also provided. It is an object of the present invention to provide a fixing device capable of preventing abrasion of the sheet and extending its life.

[0014]

The inventors of the present invention have speculated that the difference in strain amount (εh-εp) between the two rolls is the dominant factor in the occurrence of wrinkles in the envelope, and the self-stripping performance is also considered. Is presumed to be due to the circumferential distortion amount (εh) of the fixing roll on the side in contact with the unfixed toner image and the discharging direction of the recording material at the exit of the nip portion.
Regarding the wear of the fixing roll, the amount of distortion in the circumferential direction of the fixing roll on the side in contact with the unfixed toner image (εh), or the amount of distortion in the circumferential direction of the fixing roll (εh) approximately at the center and the end in the axial direction. We speculate that the difference with the department is the dominant factor,
The present invention has been devised by reaching the specification of the permissible region through experiments.

That is, according to the present invention, as shown in FIG.
A pair of fixing rolls 1 and 2 that rotate while being pressed against each other are provided, and the surfaces of the pair of fixing rolls 1 and 2 are covered with elastic bodies 3 and 4, respectively, and at least one fixing roll 1 is provided with a heating source 5. In a fixing device that is provided to fix the unfixed toner image by inserting the recording material 6 on which the unfixed toner image is formed between the fixing rollers 1 and 2, the fixing roll on the side in contact with the unfixed toner image of the recording material 6. When the amount of strain in the circumferential direction of the elastic body 3 of 1 is εh, the amount of strain in the circumferential direction of the elastic body 4 of the other fixing roll 2 is εp, and εh−εp is Δε, εh ≧ 0.0583 (Δ ε) ⁴ −0.6 (△ ε) ³ +2.1917 (△
It is characterized by satisfying the relational expression of ε) ² −3.65 (Δε) +6 εh <6% Δε ≦ 3%. Here, the first formula shows a requirement for maintaining serif stripping performance, the second formula shows a requirement for preventing abrasion of the fixing roll, and the third formula shows a requirement for preventing wrinkling of the envelope.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below in detail based on the embodiments shown in the accompanying drawings. FIG. 2 is an explanatory view showing an embodiment of a fixing device to which the invention is applied. In the figure, the fixing device includes a heating roll 10 and a pressure roll 20 that rotate while being in pressure contact with each other, and a recording in which an unfixed toner image is formed in a pressure contact portion (nip portion) 15 between the both rolls 10 and 20. The unfixed toner image is fixed by inserting the paper 50.

In the present embodiment, the heating roll 10 is a hollow roll 11 made of an iron cylinder having an outer diameter of 32 mm and an inner diameter of 28 mm, and an elastic layer 12 is coated with HTV silicone rubber (rubber hardness 40 °) for 2 mm. Fluorine rubber (rubber hardness 60 °) is dip-coated on the surface to a thickness of 30 μm, and the surface is finished to have a mirror-like state.
A halogen lamp 13 of 500 W is provided inside as a heating source, and the surface of the heating roll 10 is adjusted to 145 ° C. to 155 ° C. by a temperature controller (not shown) via a temperature sensor (not shown).

Further, as the releasing agent, as a functional group,
Amino-modified silicone oil containing (CH2) 3NH2 (oil viscosity 300CS) manufactured by Shin-Etsu Chemical Co., Ltd., b = 0.
1, c = 130 (X-21-7763G), and is uniformly supplied by an oil supply system (not shown) so that an amount of 3 mg per A4 size is transferred to the recording paper 50. Further, a so-called cleaning web (not shown) using a nonwoven fabric as a cleaning member is provided on the surface of the heating roll 10.

On the other hand, the pressure roll 20 comprises a hollow roll 21 made of an iron cylinder having a diameter of 32 mm and an inner diameter of 28 mm, and an elastic layer 22.
HTV silicone rubber (rubber hardness 40
A) is coated with Amm, and the surface thereof is dip-coated with a fluororubber (rubber hardness 60 °) to a thickness of 30 μm, so that the surface is close to a mirror surface. Here, in order to test the distortion characteristics in the present embodiment, the pressure roll 2
The thickness A of the elastic layer 22 of 0 is 0.25 mm, 0.5 mm,
0.75mm, 1.0mm, 1.25mm, 1.5m
m, 2.0 mm, which are set to seven levels, and the pressure roll 20 is a hollow roll 21 made of an iron cylinder having a diameter of 32 mm and an inner diameter of 28 mm, which is coated with a coating layer of Teflon (trademark of DuPont). Was added to one of the levels.

The pressure roll 20 is heated by a compression coil spring (not shown) as a pressure means so that the surface strain of the heat roll 10 becomes 4%.
The pressure and the nip width are different depending on each level of the pressure roll 20. Approximate load is 30-40kgf, nip width 3.5-5.5m
m. On the other hand, the heating roll 10 is rotationally driven at a speed of 70 mm / sec by a belt driving unit (not shown), and the pressure roll 20 is driven to rotate. The surface temperature of the heating roll 10 differs depending on each level of the pressure roll 20 in order to match the same fixing / coloring level.

This fixing device has various envelopes (Monroe
Brand size10, also size mona
rch, River Series size 110 ×
Table 1 shows the results of examining the occurrence of wrinkles by passing through 220 mm, also size 162 × 229 mm).

[0022]

[Table 1]

In Table 1, the roll configuration of the flat nip (pressurizing roll: Teflon coating layer) corresponds to the conventional example of FIG. 7, and the heating roll indentation n is the thickness of the elastic layer of the pressing roll 20 (rubber thickness). ) Is divided by. Further, in Table 1, lateral feed means the conveying direction of the envelope 52 as shown in FIG. 3 (c) or (d), and vertical feed means the envelope 52 as shown in FIG. 3 (a) or (b). Represents the transport direction of. 3B and 3D show the envelope 52 with the flap 52a left open. Furthermore, the wrinkle evaluation result ⊚ did not occur at all, and ∘ was 5 mm on some envelopes.
The following wrinkle occurrences, Δ are wrinkle occurrences of 10 mm or less on almost all envelopes, × are wrinkle occurrences of 30 mm or less on almost all envelopes, and XX are wrinkle occurrences of 30 mm or more on all envelopes. It represents. When the address / address is copied on the envelope by the electrophotographic copying machine, 10
Wrinkles of less than mm have little effect on the copied image.

From the wrinkle evaluation data, the wrinkle of the envelope shows the circumferential surface strain εh of the heating roll 10 and the pressure roll 2.
It was proved to have a correlation with the difference Δε with the surface strain εp in the circumferential direction of 0. It was also found that wrinkles were extremely less in horizontal feed than in vertical feed. It is considered that this is because the shorter the length passing through the nip portion 15 is, the smaller the amount of misalignment of the front and back papers on which the plurality of envelopes overlap. This can also be understood from the fact that the longest envelope of the Monroe Brand size 10 has the most wrinkles in the vertical feed. From the above, it is understood that Δε ≦ 3% (where Δε = εh−εp) is a preferable range when the allowable level of wrinkling of the envelope is ◯ in the lateral feed. Further, if the permissible level of wrinkling of the envelope is ◯ or more in the longitudinal feed, Δε ≦ 2% (where Δε = ε
It is understood that h-εp) is a preferable range.

Next, 2.0 m of color toner was applied to the above fixing device, which was relatively thin and had a weak stiffness of 55 g / m ^2.
Through the unfixed toner image transferred at a density of g / cm ² ,
The self-stripping property was investigated. At this time, the feeding direction of the recording paper is such that the fibers of the paper are parallel to the heating / pressurizing rolls 10 and 20. In the case of this feeding direction, due to the structure of the paper, the stiffness of the paper is weak, and self-stripping tends to be difficult even with the same paper thickness. The results are shown in FIG. 4 and Table 2. In FIG. 4, ◯ indicates good and bad self-stripping properties, and ● indicates a limit value of the good range of self-stripping properties. Further, in Table 2, as in Table 1, a roll configuration of a flat nip (pressurizing roll: Teflon coating layer)
Corresponds to the conventional example of FIG.
Is divided by the thickness (rubber thickness) of the elastic layer of the pressure roll 20, and εh represents the amount of strain (corresponding to the black circle in FIG. 4) necessary for peeling between the molten toner image and the fixing roll interface. ing.

[0026]

[Table 2]

From the above data, it can be seen that it is necessary to increase εh for a roll structure having a smaller Δε. This is because the roll configuration having a smaller Δε, in other words, as the flat nip is approached, the discharge direction of the recording paper at the exit of the nip portion does not face the pressure roll 20 side, and the self-direction depending on the discharge direction of the recording paper at the exit of the nip portion. Since the effect of stripping disappears, it is considered that the surface strain of the heating roll 10 must be removed. If the amount of oil supplied from an oil supply device (not shown) is increased and the amount of oil transferred to the recording paper is set to 6 to 10 mg per A4 size, the discomfort caused by the oil when handling the recording paper cannot be eliminated as in the conventional case. It has been found through experiments that self-stripping becomes easier and the minimum required εh is relaxed, but if εh in Table 2 is taken, self-stripping can be surely performed.

The data in Table 2 (the limit value of the experimental result in FIG. 4 ( in FIG. 4)) is represented by an approximate expression. The roll configuration replaced by Δε and ε capable of self-stripping are shown.
The following relationship was obtained with h. That is, εh ≧ 0.0583 (△ ε) ⁴ −0.6 (△ ε) ³ +2.1917 (△
ε) ² −3.65 (Δε) +6 However, Δε = εh−εp.

Further, each ε of Table 2 is obtained by using the above fixing device.
When a wear evaluation experiment was carried out at h, the wear of the elastic layer surface layer (decrease in gloss of the surface layer) at about 30,000 sheets when εh = 6%
Occurs at the end of the roll in the axial direction, and εh = 4%, 5%, 5.
At 5%, abrasion of the elastic layer surface layer did not occur even after 100,000 sheets or more. In this experiment, 65 g / m ² A4 size paper having an unfixed color toner image with an image density of 95% was used, and the amount of oil transferred to the paper was changed to A4 at a speed of 4 sheets per minute. The condition was 3 mg per size.

It is considered that two factors are involved in the poor result of εh = 6%. One is heating roll 10
Εh is 6% at the central portion in the axial direction, but is 7% at the end portion in the axial direction.
The larger εh at the central portion in the axial direction of the heating roll 10
The difference with the axial end tends to be large). In order to prevent wrinkles when paper that contains water under high humidity passes through the fixing device, it is necessary to make the nip width at the axial end part slightly thicker than at the central part. It will be 7%. Therefore, abrasion of the surface layer of the elastic layer (decrease in gloss of the surface layer), which is considered to be caused by slippage caused by release of strain on the surfaces of the rolls 10 and 20 at the exit of the nip portion 15, is likely to occur at the axial end portion. Another factor is that since the oil supply device is on the heating roll 10 side, most of the supplied oil is transferred to the recording paper while the recording paper 50 is passing through the nip portion 15, and the oil is not transferred to the pressure roll 20. Is not transferred and is smaller than that on the heating roll 10 side. Due to this influence, abrasion of the surface layer of the elastic layer (decrease in gloss of the surface layer) occurs remarkably in the pressure roll 20.

From this data, the following relationship was obtained with respect to εh in order to prevent wear of the elastic layer surface. That is, ε
h <6%, preferably εh ≦ 5.5%.

An area satisfying the relational expression obtained from the above experimental data is shown in FIG. The shaded area in the figure is that. As described above, the strain ε has a tolerance of about 1% at the central portion and the end portion in the roll axial direction, and has a tolerance of about 1% due to variations in the thickness of the compression coil spring and the elastic layer. When commercializing, it is safer to consider a tolerance of about 2%. Further, considering the allowable level of wrinkles of the envelope in consideration of the preferable level of ◯ or more in the vertical feed (see Table 1), 1 ≦ Δε ≦ of the shaded portion in FIG.
Region 2 is particularly preferred.

The surface strain in this embodiment is measured by the following measuring method. That is, in general, when a pair of elastic rolls (rolls having elasticity under a certain load) are pressed against each other under a certain load, the elastic roll surface is elastically deformed in the nip region, and the circumferential direction of the surface has a certain strain ε. Cause When the roll pair is rotated in this state and the recording paper passes through the nip area, the recording paper is conveyed in the distorted nip area.
For this reason, the length of the recording paper that is sent out by one rotation of the elastic roll that has been distorted becomes larger than the actual length of the roll by the amount of conveyance in the circumferential direction ε. That is, ε
(%) = [{(The length of the recording paper fed by one rotation of the elastic roll) / (perimeter of the elastic roll when ε = 0)} − 1] × 100. With this method, the actual strain ε can be measured.

Further, in the present embodiment, the fixing rolls (heating rolls and pressure rolls) 10 and 20 having the surface layer coated with fluororubber are not limited to the fixing rolls 10 and 20.
The elastic layer may be a single layer structure of HTV silicone rubber or RTV silicone rubber. However, wear is quick with an oil supply amount of 3 mg per A4 size, so 10
It is preferable to supply oil in an amount of mg or more, or to provide the surface layer with a fluororesin or a mixed layer of fluororesin and fluororubber. Also, dimethyl silicone oil can be used as a release agent. Furthermore, other cleaning members, oil supply systems, and cleaning members may be appropriately selected. Further, the pressure roll 20 may be provided with a heating source.

[0035]

【Example】

Example 1 In the embodiment of FIG. 2, the heating roll 10 has an outer diameter of 32.
mm, the inner diameter 28 mm, the hollow roll 11 made of an iron cylinder,
As the elastic layer 12, HTV silicone rubber (rubber hardness 40 °) is coated to a thickness of 2 mm as an underlayer, and fluororubber (rubber hardness 60 °) is dip-coated to a thickness of 30 μm on the surface to obtain a surface close to a mirror surface state. ing. As a heating source, a 500 W halogen lamp 13 is provided inside,
The surface of the heating roll 10 is adjusted to 146 ° C. by a temperature controller (not shown) via a temperature sensor (not shown).

Further, as a release agent, as a functional group,-(C
H2) Amino-modified silicone oil containing 3NH2 (oil viscosity 300CS) manufactured by Shin-Etsu Chemical, b = 0.1, c = 13
0 (X-21-7763G) on the recording paper 50
It is uniformly supplied by an oil supply system (not shown) using felt and a rubber blade so that an amount of 3 mg per size is transferred. A so-called cleaning web (not shown) using a nonwoven fabric as a cleaning member is provided on the surface of the heating roll 10.

On the other hand, the pressure roll 20 comprises a hollow roll 21 made of an iron cylinder having a diameter of 32 mm and an inner diameter of 28 mm, and an elastic layer 22.
HTV silicone rubber (rubber hardness 40
°) is coated with 1.5 mm, and the surface is dip-coated with fluororubber (rubber hardness 60 °) to a thickness of 30 μm.
The surface is finished close to a mirror surface.

The pressure roll 20 is heated by a compression coil spring (not shown) as a pressure means so that the surface strain of the heat roll 10 becomes 4%.
Is urged toward the center of, and the load is 36 kgf,
The nip width is 4.6 mm. The heating roll 10 is rotatably driven at a speed of 70 mm / sec by a belt driving unit (not shown), and the pressure roll 20 is driven to rotate.

Next, when the performance of the fixing device according to this embodiment was examined, the following results were obtained. First, Table 3 shows the results of the wrinkle generation experiment of the envelope according to the present embodiment.
Shown in

[0040]

[Table 3]

Table 3 shows the presence or absence of wrinkles in the conveying directions (a), (d) (corresponding to FIGS. 3 (a), (d)) of various envelopes (○ does not occur, Δ is 5 mm or less). Wrinkle formation, x indicates wrinkle formation exceeding 5 mm). Incidentally, Mon
Regarding the roe Brand size 10, it is Δ even in the transport direction (b) (corresponding to FIG. 3B), and the
Regarding e Brand size Monarch, it was ◯ in the transport direction (b) (corresponding to FIG. 3B).

Further, when the above-mentioned abrasion evaluation experiment was conducted, abrasion and offset of the surface of the roll elastic layer and adhesion of toner to the surface of the heating roll 10 did not occur up to 100,000 sheets.

Example 2 Although the structure is substantially the same as that of Example 1, unlike Example 1,
The hardness of the roll elastic layers 12 and 22 is 60 ° or 70
The same results as in Example 1 were obtained by using the one of the above type. In addition, the rotation speed (fixing speed) of the roll is
Under the condition different from that, the same result as in Example 1 was obtained. However, when the hardness of the roll elastic layer is changed, the nip width obtained even when the strain ε is adjusted becomes narrower, so it is necessary to review the fixing conditions such as setting the surface temperature of the heating roll 10 corresponding to it. Therefore, according to this example, it is confirmed that the present invention is established regardless of the hardness of the elastic layer of the roll and the rotation speed (fixing speed) of the roll. This indicates that the circumferential strain ε of the surface is determined by the geometric mixing of the two rolls and is not affected by other conditions.

Example 3 Although the configuration is substantially the same as that of Example 1, unlike Example 1,
When the outer diameters of the rolls 10 and 20 and the thicknesses of the elastic layers 12 and 22 were multiplied by x, a nip width of x times and a load of 1 / x times were obtained without changing both εh and εp. In this case, the load per unit area in the nip region does not change. However, as the nip width changes, it is necessary to review the fixing conditions corresponding to it. Therefore, according to this example, it is confirmed that the present invention can be realized even if the outer diameter of the roll and the thickness of the elastic layer are changed.

Example 4 The configuration is substantially the same as that of Example 1, but unlike Example 1,
Only the thickness of the elastic layers 12, 22 of each roll 10, 20 is x
When doubled, εh and εp, the load, and the load per unit area are all 1 / x times. The nip width in this case does not change. Therefore, according to the present embodiment, the present invention provides the elastic layers 12, 22 without changing the outer diameters of the rolls 10, 20.
It is confirmed that it is established even if only the thickness of is changed.

[0046]

As is apparent from the above description, the present invention realizes an optimum roll structure based on the circumferential strain ε of the roll surface, and thus the conventional heating and pressure fixing device having an elastic layer. It can achieve "self-stripping performance", "envelope wrinkle prevention", and "elastic layer wear prevention" which were not possible in the above. As a result, self-stripping can be performed without using a peeling device, wrinkles in the envelope can be prevented, and the life of the fixing roll can be extended. These can be achieved even under the condition that the amount of the release agent supplied is small. Further, it is possible to easily provide an appropriate roll configuration that obtains the above-mentioned effects for various roll configurations.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a configuration of a fixing device according to the present invention.

FIG. 2 is an explanatory diagram showing an embodiment of a fixing device to which the present invention is applied.

FIG. 3 is an explanatory diagram showing a feeding mode of the envelope viewed from the pressure roll side in a paper wrinkle experiment.

FIG. 4 is a distortion characteristic of the fixing device according to the present embodiment (Δ
It is a graph figure which shows (relationship of (epsilon) h- (epsilon) p and (epsilon) h).

FIG. 5 is an explanatory diagram showing an example of a conventional fixing device.

FIG. 6 is an explanatory diagram showing another example of a conventional fixing device.

FIG. 7 is an explanatory diagram showing still another example of a conventional fixing device.

[Explanation of symbols]

1, 2 ... Fixing roll, 3, 4 ... Elastic body, 5 ... Heating source, 6
.. recording material, .epsilon.h ... amount of circumferential strain of elastic body of fixing roll on side contacting unfixed toner image, .epsilon.p ... amount of circumferential strain of elastic body of other fixing roll, .DELTA..epsilon..epsilon.h-.epsilon.p

Front page continued (72) Inventor Keitaro Sonoguchi 2274 Hongo, Ebina City, Kanagawa Prefecture Fuji Xerox Co., Ltd.

Claims (1)

[Claims] 1. A pair of fixing rolls (1) and (2) that rotate while being pressed against each other, and the surfaces of the pair of fixing rolls (1) and (2) are elastic bodies (3) and (4), respectively. ), A heating source (5) is provided on at least one fixing roll (1), and a recording material (6) on which an unfixed toner image is formed is inserted between both fixing rolls (1) and (2). In the fixing device for fixing the unfixed toner image by doing so, the amount of distortion in the circumferential direction of the elastic body (3) of the fixing roll (1) on the side of the recording material (6) contacting the unfixed toner image is εh, and the other is When the amount of strain in the circumferential direction of the elastic body (4) of the fixing roll (2) is εp and εh-εp is Δε, εh ≧ 0.0583 (Δε) ⁴ −0.6 (Δε) ³ +2.1917 (△
A fixing device characterized by satisfying a relational expression of ε) ² −3.65 (Δε) +6 εh <6% Δε ≦ 3%.