Rubber fixing roller

FIELD OF THE INVENTION

The present invention relates to a rubber fixing-roller for use in a fixing apparatus which is applied for fusing and pressing unfixed toner on a sheet so as to fix the toner onto the sheet in copier, printer, facsimile, and the like.

BACKGROUND OF THE INVENTION

Heretofore, in a fixing apparatus of electrophotographic equipment, a so-called two rollers arrangement has been employed, which essentially includes two rollers, a heating roller having a heat source built-in and a pressing roller pressed to the heating roller with a predetermined pressure. In parallel with various related patent applications, this arrangement has been widely used.

In such two rollers arrangement, when it is required to provide a nip portion having a predetermined width at a position where the two rollers are rotatably contacted with each other, at least one of rollers must have a rubber elastic layer. Heretofore, the heating roller includes a rubber heat-resisting layer or fluororesin layer excellent in heat resistance because of having the heat source built-in, while the pressing roller includes a specific rubber elastic layer capable of assuring to form the nip portion.

If the rubber elastic layer of the pressing roller has a large heat capacity, the heating roller will be interfered in its temperature-rising due to the fact that the pressing roller in cool state contacts to the heating roller. As a result, a deteriorated temperature-rising rate causes a problem of long warming-up period of time. Particularly, as the heat conductivity of the rubber elastic roller is increased, this problem will come to the front, resulting in further extended warming-up period of time. Thus, it is desired to settle this problem.

In view of sufficiently providing the nip width described above, it is desirable to form the elastic layer of the pressing roller from a sponge rubber which has a high thermal responsiveness due to its low hardness or excellent elasticity, and extremely small heat capacity. This allows the rollers to be heated up to a desired fixing temperature in a short period of time. Applying this pressing roller to a fixing apparatus means to yield a capability for shortening the warming-up period of time, and is distinctly desirable from the standpoint of the recent demand for energy saving.

However, in the above case, the peripheral surface of the elastic layer in the pressing roller is heated up to the fixing temperature of, for example, about 180° C. by receiving heat from the heating roller or heat fixing-roller. While the elastic layer formed of sponge rubber is thermally expanded inevitably by being heated up to high temperature as described above, the level of this thermal expansion is different for each region of the elastic layer depending on differences in the foamed state of sponge rubber.

The outside diameter of the pressing roller applying sponge rubber to the elastic layer is randomly varied, or irregularly deformed, in the axial direction of the pressing roller, especially just after the warming-up operation has been completed.

As a result, when an unfixed sheet supporting unfixed toner is passed through the nip portion just after the completion of the warming-up operation, the unfixed sheet tends to have corrugations due to the irregularities on the peripheral surface of the pressing roller. When such corrugations have been created in the unfixed sheet, the sheet with the corrugations loses its utility value even if a toner image can successfully fixed thereon. Taking in the broad sense, this problematically corresponds to one defect in fixing operation.

SUMMARY OF THE INVENTION

The present invention is developed to solve the problems described above. It is one object of the present invention to provide a rubber fixing-roller capable of increasing temperature-rising rate of a fixing member by limiting the rate and amount of heat-transfer from the fixing member as small as possible.

It is another object of the present invention to provide a rubber fixing-roller capable of achieving a stable fixing operation when a sheet is passed therethrough by limiting the rate and amount of heat-transfer from the fixing member as small as possible.

It is still another object of the present invention to provide a rubber fixing apparatus capable of assuring a sufficient nip width and achieving a desired low heat capacity without using sponge rubber.

It is yet another object of the present invention to provide a rubber fixing apparatus capable of assuring a sufficient nip width and having no corrugation in a sheet even just after the completion of the warming-up operation.

It is a further object of the present invention to provide a rubber fixing apparatus capable of assuring a sufficient nip width and shortening the warming-up period of time.

In order to settle the problems and to achieve the objects described above, according to a first aspect of the present invention, a rubber fixing apparatus comprises a core and an elastic layer provided on the periphery of the core, the elastic layer is adapted to satisfy the following formula;

0.0004≦A≦0.0037

where A (J

2

/sec·cm

4

·K

2

) is a product value from the specific heat (J/g·K), density (g/cm

3

), and heat conductivity (W/m·K) of said elastic layer

In the rubber fixing-roller according to the first aspect of the present invention, the peripheral surface of the elastic layer may be covered with a releasing layer. This releasing layer may be formed of fluororesin.

In the rubber fixing-roller according to the first aspect of the present invention, the elastic layer may include a material having low specific heat and low heat conductivity dispersed in the elastic layer. This elastic layer may be formed of cellular rubber, preferably foamed rubber.

Alternatively, the elastic layer may be formed of a rubber with which a hollow filler, preferably a glass balloon, is dispersedly mixed as the material having low specific heat and low heat conductivity. The elastic layer may otherwise be formed of silicon rubber.

In the rubber fixing-roller according to the first aspect of the present invention, the rubber fixing-roller may be positioned to contact to the fixing member with a predetermined pressure.

According to a second aspect of the present invention, a rubber fixing-roller comprises a core and a non-foamed rubber elastic layer provided on the periphery of the core, the layer including a peripheral surface having a predetermined outside diameter, the layer being prepared in a predetermined heat capacity per unit volume by mixing a filler having low density and low specific heat.

In the rubber fixing-roller according to the second aspect of the present invention, the peripheral surface of the elastic layer may be covered with a releasing layer. This releasing layer may be formed of fluororesin.

In the rubber fixing-roller according to the second aspect of the present invention, the filler having low density and low specific heat may be a hollow material, or otherwise include a multi-component glass.

In the rubber fixing-roller according to the second aspect of the present invention, the rubber fixing-roller may be adapted to satisfy the following formula;

0.77≦ρ· c≦1.32

where ρ is a density (g/cm

3

) and c is a specific heat (J/g·K), in the range of from the peripheral surface of the elastic layer to at least 2 mm in depth.

In this case, the filler having low density and low specific heat is preferably not mixed in the range deeper than 2 mm in depth from the peripheral surface of the elastic layer.

In the rubber fixing-roller according to the second aspect of the present invention, the rubber fixing-roller may be adapted to satisfy the following formula;

0.77≦ρ· c≦1.32

where ρ is a density (g/cm

3

) and c is a specific heat (J/g·K), in the entire range of the elastic layer.

These and other aspects of the present invention are apparent in the following detailed description and claims, particularly when considered in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a schematic front view showing a fixing apparatus using a rubber fixing-roller according to one embodiment of the present invention;

FIG. 2

is a cross-sectional view showing the pressing roller used as the rubber fixing-roller in

FIG. 1

;

FIG. 3

is diagrammatic drawing showing the relationship between the fixing rate and the heat gain amount;

FIG. 4

is a schematic front view showing another fixing apparatus using a rubber fixing-roller of a first alternative example according to the present invention;

FIG. 5

is a schematic front view showing still another fixing apparatus using a rubber fixing-roller of a second alternative example according to the present invention;

FIG. 6

is a front view showing a rubber fixing-roller according to another embodiment of the present invention;

FIG. 7

is a cross-sectional view showing the rubber fixing-roller in

FIG. 6

;

FIG. 8

is a diagrammatic view showing the change of the shape of a pressing roller over time, in case that the pressing roller having an elastic layer with the mixed glass balloon of 5 parts is heated up;

FIG. 9

is a diagrammatic view showing the change of the shape of a pressing roller over time, in case that the pressing roller having an elastic layer with the mixed glass balloon of 10 parts is heated up;

FIG. 10

is a diagrammatic view showing the change of the shape of a pressing roller over time, in case that the pressing roller having an elastic layer with the mixed glass balloon of 15 parts is heated up;

FIG. 11

is a diagrammatic view showing the change of the shape of a pressing roller over time, in case that the pressing roller having an elastic layer composed of sponge rubber is heated up;

FIG. 12

is a diagrammatic view showing the change of the shape of a pressing roller over time, in case that the pressing roller having an elastic layer composed only of non-foamed rubber is heated up;

FIG. 13

is a diagrammatic view showing the relationship between mixing ratio of glass balloon and changing amount of outside diameter of a heating roller;

FIG. 14

is a front cross-sectional view showing a rubber fixing-roller according to another embodiment of the present invention, and

FIG. 15

is a cross-sectional view showing the rubber fixing-roller in FIG.

14

.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG.

1

and

FIG. 2

in the accompanying drawings, a rubber fixing-roller according to the first embodiment of to the present invention will now be described in detail.

With reference to

FIG. 1

, a fixing apparatus

20

provided with the rubber fixing-roller as the first embodiment will be firstly described. The fixing apparatus

20

includes a fixing housing (not shown) secured to a frame of an electronic image forming equipment (not shown), e.g. an electronic printer. In this fixing housing, the fixing apparatus

20

also includes a heat fixing-roller

22

as a fixing member, a pressing roller

10

as the rubber fixing-roller according to the first embodiment, which is pressed to the heat fixing-roller

22

with a predetermined pressure, and a heat source

24

, such as a halogen lump, disposed in the heat fixing-roller to heat the peripheral surface of the heat fixing-roller

22

.

As shown in

FIG. 2

, the pressing roller

10

includes an iron core

12

having a nickel-plated surface, a cylindrical elastic layer

14

made of cellular rubber (foamed rubber in this embodiment) and jointed tightly on the periphery of the core

12

with adhesive, and a releasing layer

16

having a predetermined thickness and formed of a fluororesin layer covering the peripheral surface of the elastic layer

14

. In the first embodiment, the elastic layer is arranged in 5.5 mm of thickness and the pressing roller

10

is arranged in 25 mm of outside diameter.

On the other hand, the heat fixing-roller

22

described above includes an aluminum core

26

, and a releasing layer

28

composed of fluororesin coated on the periphery of the core

26

. In this fixing apparatus, the heat fixing-roller

22

is arranged in 25 mm of outside diameter. Further, the heat fixing-roller

22

is rotatably driven at a predetermined rotational speed by driving means, not shown. With reference to

FIG. 3

, the elastic layer

14

of the pressing roller

10

as the rubber fixing-roller according to the first embodiment will now be described in detail.

The elastic layer

14

includes air or foam gas dispersed therein as a material having low specific heat and low heat conductivity. In this embodiment, the elastic layer

14

is formed of cellular rubber, more specifically, which is produced by foaming a material based on a silicon rubber designated by Model No: KE-90FU made by Shin-Etsu Chemical Co., Ltd. Thus, in the first embodiment, the foam gas as a material having low specific heat and low heat conductivity is mixed to and dispersed over the elastic layer

14

.

The elastic layer

14

is also arranged in 150% of foaming ratio, i.e. 33% of porosity. The optimal range of the foaming ratio (porosity) will be described later.

Since the elastic layer

14

described above is formed of foamed rubber, both the density and heat conductivity of the elastic layer

14

decrease as its foaming ratio increases. As a result, the heat gain amount A per unit volume derived from multiplying the density and heat conductivity also decreases as the foaming ratio increases.

This heat gain amount A is a new parameter introduced by the inventors of the present invention in order to evaluate the rubber fixing-roller. According to this new parameter, smaller heat gain amount A indicates that the roller surface can be heated up in a shorter period of time without lowering the temperature of the heat fixing-roller.

However, excessively increasing the foaming ratio causes excessively increased compression set. As a result, the deformation in the portion for nip cannot be recovered, which makes the resulting roller useless. Thus, in view of average cell diameter, it is required to set an upper limit to the foaming ratio. It has also been proved that excessively decreased foaming ratio is undesirable in view of fixing rate. Finally, the inventors have discovered the presence of an optimal range for the heat gain amount A.

This optimal range of the heat gain amount A will now be verified.

With changing the foaming ratio between 102% and 325%, filling factor (%), density (g/cmE3) (where Ex indicates power of x. That is, cmE3 indicates cm

3

, and cm E2 indicating cm

2

. E−2 also indicates minus square or minus second power, and so forth.), specific heat (J/g·K), heat conductivity (W/m·K), compression set (%), and fixing rate (%) were determined respectively, and the temperature-rising time for rising up to 130° C. in each foaming ratio was also determined. This result is shown in Table 1.

As shown in Table 1, in view of compression set, the range up to 36% is the range where the deformation in the portion for nip can be reliably recovered. Thus, it was proved that the lower limit of the heat gain amount A was 4.19E−4 (≈0.0004).

The graph in

FIG. 3

shows the correlation between the fixing rate (%) and the heat gain amount A.

The density (g/cmE3) indicates values derived from determining the volume and weight of the measuring object and then dividing the volume by the weight. The specific heat (J/g·K) indicates values determined using a thermal analyzer. The heat conductivity (W/m·K) indicates values determined by a QTM heat conductivity meter. The compression set (%) indicates values determined based on JIS K6301. The fixing rate (%) indicates values obtained by using the fixing apparatus

20

and determining the fixing rate of the first sheet passed through the nip after having idle cycles for 5 seconds after heating the heat fixing roller up to 185° C. under the stationary state of the rollers.

The temperature-rising time indicates values obtained by incorporating this fixing apparatus into an actual equipment (Able 1321: Fuji Xerox Co., Ltd.) and then determining the actual temperature-rising time for heating the surface of the pressing roller

10

up to 130° C.

Considering 85% of the required fixing rate, the graph shown in

FIG. 3

was checked up by taking 85% or more of fixing rate as evaluation criteria. Then, it was proved that the upper limit of the heat gain amount A was 3.7E−3 (=0.0037).

Thus, it was proved that the optimal range of the heat gain amount A is the range of values satisfying the following inequality (1);

0.0004≦A≦0.0037 (1)

In the first embodiment, since the foaming ration is arranged in 150%, the heat gain amount A is 0.00165 based on Table 1 and is apparently in the above optimal range.

As described above, according to the first embodiment, the new parameter of the heat gain amount A is intoduced and the elastic layer

14

of the pressing roller

10

as the rubber fixing-roller is then arranged to make the heat gain amount A get in the above optimal range, so that the pressing roller can be heated up in a shorter period of time without lowering the temperature of the heat fixing-roller when the pressing roller

10

is heated.

While the elastic layer

14

of the pressing roller

10

as the rubber fixing-roller has been described as that formed of sponge rubber (or foamed rubber) in the above embodiment, the present invention is not limited to this construction and non-foamed cellular rubber may also be applied to form the elastic layer. In this case, it is apparent that the foaming rate is not defined and only porosity will be defined.

Further, while the rubber fixing-roller has been described as the pressing roller positioned to contact to the heat fixing-roller with a predetermined pressure in the above embodiment, the present invention is not limited to such an arrangement. For instance, it may be configured as a first alterative example shown in

FIG. 4

, in which a fixing roller

34

heated directly from outside by a heating roller

32

having a heat source

30

built-in is provided as the fixing member, and a pressing roller

10

A contacted to the fixing roller

34

with a predetermined pressure is applied with the rubber fixing-roller. It may also be configured as a second alternative example shown in

FIG. 5

, in which a fixing belt

40

formed of a heat transfer belt, which is endlessly wound around between a heating roller

38

having a heat source

36

built-in and a fixing roller

42

so as to transfer a heat from the heating roller

38

, is provided as the fixing member, and a pressing roller

10

B contacted to the fixing roller

42

through the fixing belt

40

with a predetermined pressure is applied with the rubber fixing-roller.

Further, while it has been described in the above embodiment that a roller type member was applied as the fixing member, the present invention is not limited to this construction. For instance, any belt type or sleeve type of fixing members may be apparently applied.

Further, while the material having low specific heat and low heat conductivity has been described as the cellular rubber with dispersed air therein or the foamed rubber with dispersed form gas therein in the above embodiment, the present invention is not limited to this construction. For instance, hollow filler, such as glass balloon, may be applied as the material having low specific heat and low heat conductivity.

With reference to FIG.

6

and

FIG. 7

, the elastic layer

14

of the pressing roller according to the second embodiment will now be described in detail.

In the second embodiment, the elastic layer

14

is formed by preparing a non-foamed rubber

14

a

designated by Silicon Rubber Model No: X-34-1279A/B made by Shin-Etsu Chemical Co., Ltd as a base rubber and then dispersing a glass balloon

14

b

as the material having low specific heat and low heat conductivity uniformly in the base rubber. In this embodiment, a multi-component glass balloon, specifically Model No: Z-27 made by Tokai Industries, Ltd., is applied. The density of glass balloon in this embodiment is not defined as an apparent density but as the true density determined independently for each filler.

The mixing amount of this glass balloon

14

b

is arranged in 15 parts.

A manufacturing process of the pressing roller

10

will be described.

The process has a beginning with preparing 500 g respectively for liquid A and liquid B of Silicon Rubber Model No: X-34-1279 made by Shin-Etsu Chemical Co., Ltd. as the non-foamed rubber

14

of material and also preparing 150 g of Model No: Z-27 made by Tokai Industries, Ltd. as the glass balloon

14

b

. The liquid A and liquid B are then put into a closed mixer and mixed for about 5 minutes. Then, the rubber with uniformly dispersed glass balloon is degassed by a vacuum deaerator.

On the other hand, a stainless shaft making up the core

12

and a fluororesin tube making up the releasing layer

16

are positioned in a molding machine, and the degassed rubber with the glass balloon is injected into the molding machine for subjecting to a primary curing for 30 minutes in an oven heated at 150° C. Then, the roller is taken out of the molding machine and subjected to a secondary curing for 4 hours in a oven heated at 200° C. to bring the pressing roller to completion.

In the produced pressing roller

10

, the glass balloon

14

b

is uniformly mixed in

15

parts with the non-foamed rubber

14

a

making up the elastic layer

14

so that both density and specific heat become lower as compared to the case where the elastic layer

14

is composed only of the non-foamed rubber. Consequently, the heat capacity per unit volume derived from multiplying the density and specific heat also decreases so that low heat capacity can be achieved and thermal responsiveness can be improved despite applying the non-foamed rubber

14

a

to the elastic layer

14

. This allows the warming-up period of time to be shortened. It is apparent that low thermal expansion affected originally by applying the non-foamed rubber

14

a

can also be achieved.

The glass balloon is mixed by 15 parts in the above embodiment. This compound will now be referred to as A. A compound B mixed by 20 parts and a compound C mixed by 15 parts were separately prepared and formed into respective elastic layers

14

. Then, each of density, specific heat, heat conductivity, compression set, and fixing rate of respective elastic layers

14

was determined in the same way as the first embodiment. The result is shown in Table 2.

As is apparent from Table 2, all heat gain amounts A of elastic layers

14

in respective compounds A, B, and C satisfies the inequality of the above-mentioned optimal range defined by

0.0004≦A≦0.0037,

and have the same effects as the first embodiment.

However, in parallel with increasing the mixing amount of the glass balloon

14

b

, the hardness of the elastic layer

14

is undesirably increased. Thus, the mixing rate of the glass balloon would have an optimal range. This optimal range of the mixing rate of the glass balloon will now be verified.

According to the manufacturing process described in connection with the second embodiment, samples A to G were produced in which their mixing rates of the glass balloon

14

b

were arranged in 0 part (i.e. no mixing), 2 parts, 3 parts, 5 parts, 10 parts, 15 parts, 20 parts, 25 parts, and 30 parts, respectively. Then, each of density, specific heat, hardness, heat conductivity, and compression set was determined.

The density ρ was defined by a value (g/cm

3

) derived from determining each volume (cm

3

) and mass (g) of the samples A to G and then dividing the mass by the weight. The specific heat c was defined by a value (J/g·K) determined using a specific heat meter. The hardness was defined by a value determined C hardness using a hardness meter (Kobunshi Keiki Co., Ltd.: Model C) under 1 Kg load. The heat conductivity was defined by a value determined in a QTM heat conductivity meter (Kyoto Electronics Manufacturing Co., Ltd.). The compression set was defined by a value determined based on JIS K6301.

The result is shown in Table 3.

As is apparent from Table. 3, the density ρ and specific heat c decrease in parallel with increasing the mixing rate of the glass balloon

14

b

. As a result, it can be understood that the heat capacity per unit volume defined by density ρ×specific heat gradually decreases.

As a comparative example where the pressing roller is composed of a silicon sponge rubber roller, the value corresponding to Table 3 was determined. This silicon sponge rubber roller was produced through preparing a base rubber of KE904FU made by Shin-Etsu Chemical Co., Ltd, and then mixing 0.6 parts of C-24 and 3.0 of C-3 as curing agent, and 3 parts of KE-P-13 as foaming agent. The result corresponding to Table 3 is shown in Table 4.

Comparing Table 4 and Table 3, in the sample A with no mixed glass balloon

14

b

, that is, in case of the elastic layer

14

composed only of non-foamed rubber, the value of density ρ×specific heat c represents a extremely high value of 1.510 and an inferior thermal responsiveness as compared to 0.762 of density ρ×specific heat c for the elastic layer

14

composed of sponge rubber.

On the other hand, when the glass balloon

14

b

is mixed even by 3 parts, density ρ×specific heat c decreases to 1,322 so that thermal responsiveness is improved. Thus, it was proved that thermal responsiveness is improved by mixing 3 parts of glass balloon as compared to the elastic later

14

composed only of non-foamed rubber. The evaluation criteria of the rubber property in case of using for the pressing roller are as follows.

Hardness is preferably to be 65 degree or less which corresponds to the value of non-foamed rubber. Because more than 65 degree yields too much of stiffness so that the contacting portion to the heating roller is not resiliently deformed and the desired nip width cannot be obtained.

While there are not specific criteria for heat conductivity, lower heat conductivity is advantageously to shorten the warming-up period of time.

Compression set is preferably to be 20% or less which corresponds to sponge rubber. Because more than 20% of compression set undesirably makes a nip trace during waiting period, resulting in deteriorated image quality.

Considering the above evaluation criteria and the values of sponge rubber, it was proved that the mixing rate of the glass balloon

14

b

is preferably up to 25 parts. This means that the range where the value of density ρ×specific heat c satisfies the following formula (2) is optimal.

0.77≦ρ·c≦1.32 (2)

In accordance with the experimental verification described above, the pressing roller

10

having the elastic layer

14

with the mixed glass balloon

14

b

was produced, and various effects were actually verified by mounting the produced elastic layer to the fixing apparatus.

For this verification, an inventive example 1 of the pressing roller

10

having the elastic layer

14

with 5 parts of glass balloon

14

b

, an inventive example 2 of the pressing roller

10

having the elastic layer

14

with 10 parts of glass balloon

14

b

, and an inventive example 3 of the pressing roller

10

having the elastic layer

14

with 15 parts of glass balloon

14

b

were produced. A comparative example 1 of a pressing roller having an elastic layer composed of the above mentioned sponge roller, and a comparative example 2 of a pressing roller having an elastic layer composed only of non-foamed rubber with no mixed glass balloon were also produced.

Each pressing rollers were incorporated in the fixing apparatus with being contacted to the heating roller to make 4 mm of the nip width and were rotated at 100 mm/sec of peripheral speed. With heating the heating roller

22

from a room temperature up to the fixing temperature, the change over time of the surface temperature of each the pressing roller was determined.

The result is shown in Table 5.

In order to compare the warming-up period of time for each pressing roller, the time needed for the surface temperature of each pressing roller to reach 130° C. is picked up and this result is shown in Table 6.

As is apparent from Table 4, the comparative example 2 (the pressing roller having the elastic layer composed only of non-foamed rubber) needs considerable long warming-up period of time as compared to the comparative example 1 (the pressing roller having the elastic layer composed of sponge rubber). In contrast, it was proved that the inventive examples 1 to 3 were not superior to the comparative example 1 but were significantly improved as compared to the comparative example 2.

The change in shape of each the pressing roller under heating was verified. With setting a temperature controlled bath at 180° C. The outside diameter of each the pressing roller was determined by a laser length-measuring device (Tokyo Opt-Electronics Co., Ltd.) respectively after 5 minutes, 10 minutes, 15 minutes, and 30 minutes after introducing each the pressing rollers into the above 180° C. of atmosphere.

Tables 7, 8, 9, 10 and 11 show results of respective pressure rolls of the inventive examples 1, 2, and 3, and the comparative examples 1 and 2, respectively.

In addition, respective results in Tables 7 to 11 are graphed out in

FIGS. 8

to

12

.

Referring to these

FIGS. 8

to

10

and

FIG. 12

, in the inventive examples 1 to 3 and the comparative example 2, while the shape in the outside diameter is evidently expanded under heating, the change is substantially even in the axial direction of each pressing roller, so that corrugations in a sheet would not be caused due to this thermal change of the shape in the outside diameter (i.e. the shape of outside peripheral surface). This effect may be naturally expected because of applying non-foamed rubber as the base rubber of the elastic layer

14

a.

Referring to

FIG. 11

of the comparative example 1, as described in the context of the background of the invention, it can be understood that the thermal deformation appears in the axial direction of the pressing roller to cause corrugations in a sheet, as a particular problem of sponge rubber.

The changing amount at each the lapsed time is picked up from Tables 7 to 9 and Table 11 and this result is shown Table 12.

The result in Table 12 is graphed out in FIG.

13

. Based on

FIG. 13

, it was proved that increasing the mixing rate of the glass balloon desirably makes the changing amount of outside diameter under heating smaller.

It should be understood that the present invention is not limited to the embodiments described above and many other variations and modifications may be made without departing from the spirit and scope of the present invention.

For instance, while the glass balloon has been described to disperse all over the elastic layer

14

in the above embodiment, the present invention is not limited to this structure. Specifically, in a pressing roller

10

′ shown in

FIGS. 14 and 15

according to another embodiment of the present invention, the elastic layer

14

may be configured as two-layers structure composed of a lower layer

14

A of the core

12

and an upper layer

14

B located on the surface side. In this case, the glass balloon

14

b

may be dispersed uniformly in the upper layer

14

B of the non-foamed rubber

14

a

. That is, it is not necessary to disperse the glass balloon

14

b

in the lower layer

14

A partially making up the elastic layer

14

. The thickness of the upper layer

14

B is sufficiently to be 2 mm.

Further, while the filler having low density and low specific heat has been described as a glass balloon, i.e. a multi-component glass balloon, such as alumina silicate glass or borosilicate soda glass, in the above embodiment, the present invention is not limited to this structure. For instance, a Shirasu balloon of volcanic glass or carbon balloon, a resinous balloon, or a metallic balloon may be applied. That is, any suitable balloons which allows the elastic layer

14

to have a density and specific heat so as to make the heat capacity of the elastic layer

14

lower than that of non-foamed rubber

14

a

itself.

Further, while the elastic layer of the pressing roller has been described to make from a silicone rubber with the dispersed glass balloon as the filler having low density and low specific heat in the above embodiment, the present invention is not limited to this structure. It is apparent that low heat capacity may be achieved by applying the silicon rubber as the heating roller.

As described above, according to the present invention, a rubber fixing-roller is provided which is capable of increasing temperature-rising rate of the fixing member by limiting the rate and amount of heat-transfer from the fixing member as small as possible. In addition, a rubber fixing-roller is provided which is capable of achieving a stable fixing operation during a sheet is passed therethrough by limiting the rate and amount of heat-transfer from the fixing member as small as possible.

Further, according to the present invention, there is provided a rubber fixing-roller capable of assuring a sufficient nip width and achieving low heat capacity without using sponge rubber.

Further, according to the present invention, there is provided a rubber fixing-roller capable of assuring a sufficient nip width and preventing a sheet from having corrugations even just after the completion of warming-up period of time.

Further, according to the present invention, there is provided a rubber fixing-roller capable of assuring a sufficient nip width and shortening the warming-up period of time.

TABLE 1

HEAT

PERMANENT

FORMING

FILLING

SPECIFIC

CONDUC-

COMPRESSION

FIXING

TEMPERATURE

HEAT GAIN

RATIO

FACTOR

DENSITY

HEAT

TIVITY

SET

RATE

RISING-TIME

AMOUNT (A)

%

vol %

g/cm

3

J/g · K

W/m · K

%

%

sec

J

2

/sec · cm

4

· K

2

102

2.0

1.160

1.50

0.241

15

∘

77

x

52

4.19E-03

x

105

4.8

1.124

1.49

0.224

16

∘

81

x

52

3.75E-03

x

110

9.1

1.073

1.47

0.203

17

∘

86

Δ

51

3.20E-03

∘

125

20.8

0.944

1.45

0.178

19

∘

90

∘

48

2.43E-03

∘

150

33.3

0.780

1.43

0.148

21

∘

92

∘

45

1.65E-03

∘

175

42.9

0.674

1.42

0.128

23

∘

93

∘

42

1.23E-03

∘

200

50.0

0.590

1.40

0.416

25

∘

93

∘

40

9.58E-04

∘

225

55.6

0.524

1.38

0.104

28

∘

95

⊚

36

7.51E-04

∘

250

60.0

0.472

1.36

0.097

30

∘

95

⊚

33

6.23E-04

∘

275

63.6

0.429

1.32

0.088

33

∘

95

⊚

29

4.98E-04

∘

300

66.7

0.393

1.30

0.082

36

∘

96

⊚

27

4.19E-04

∘

325

69.2

0.363

1.25

0.077

40

x

96

⊚

24

3.49E-04

x

HEAT GAIN AMOUNT (A) = SPECIFIC HEAT × DENSITY × HEAT CONDUCTIVITY

TABLE 2

HEAT

PERMANENT

FILLING

SPECIFIC

CONDUC-

COMPRESSION

FIXING

TEMPERATURE

HEAT GAIN

FACTOR

DENSITY

HEAT

TIVITY

SET

RATE

RISING-TIME

AMOUNT (A)

vol %

g/cm

3

J/g · K

W/m · K

%

%

sec

J

2

/sec · cm

4

· K

2

COMPOUND (A)

41.4

0.940

1.01

0.221

12

∘

92

∘

50

2.10E-03

∘

COMPOUND (B)

48.5

0.860

0.98

0.195

15

∘

94

∘

48

1.64E-03

∘

COMPOUND (C)

54.1

0.820

0.95

0.174

19

∘

95

⊚

45

1.36E-03

∘

HEAT GAIN AMOUNT (A) = SPECIFIC HEAT × DENSITY × HEAT CONDUCTIVITY

TABLE 3

DENSITY ×

HEAT

PERMANENT

MIXING RATE OF

SPECIFIC

SPECIFIC

CONDUCT-

COMPRESSION

GLASS BALOON

DENSITY

HEAT

HEAT

HARDNESS

TICITY

SET

PARTS

g/cm

3

J/g · K

J/cm

3

· K

ASKER C

W/m · K

%

0

1.28

1.18

1.510

18

∘

0.31

3

∘

2

1.21

1.15

1.392

23

∘

0.30

4

∘

3

1.18

1.12

1.322

26

∘

0.29

5

∘

5

1.15

1.07

1.231

28

∘

0.28

6

∘

10

1.04

1.03

1.071

36

∘

0.25

9

∘

15

0.94

1.01

0.949

46

∘

0.23

12

∘

20

0.86

0.98

0.843

55

∘

0.21

15

∘

25

0.82

0.95

0.779

64

∘

0.20

19

∘

30

0.78

0.92

0.718

73

x

0.19

24

x

TABLE 4

DENSITY ×

SPECIFIC

HEAT

PERMANENT

SPECIFIC

HEAT

CONDUCT-

COMPRESSION

DENSITY

HEAT

HARDNESS

HARDNESS

TICITY

SET

g/cm

3

J/g · K

J/cm

3

· K

ASKER C

W/m · K

%

0.63

1.21

0.762

30

0.08

18

TABLE 5

WITH NO

WITH 5 PARTS OF

WITH 10 PARTS OF

WITH 15 PARTS OF

TIME

SPONGE TYPE

GLASS BALOON

GLASS BALOON

GLASS BALOON

GLASS BALOON

(sec)

H/R 178˜183° C.

H/R 178˜182° C.

H/R 179˜182° C.

H/R 178˜182° C.

H/R 178˜182° C.

0

25.2

25.2

25.2

25.2

25.2

5

31.4

29.0

30.3

30.5

31.2

10

41.4

33.9

36.9

37.6

38.8

15

52.0

43.5

46.4

47.6

48.2

20

64.1

54.5

57.2

58.8

61.3

25

77.8

64.0

66.6

69.9

72.2

30

90.0

73.8

77.5

80.8

82.5

40

112.0

93.3

98.2

103.5

107.4

50

134.5

114.0

121.2

124.5

129.2

60

144.0

128.5

134.2

136.0

137.7

90

150.4

139.9

143.8

144.2

145.8

120

151.4

143.8

147.8

148.7

149.5

150

152.3

146.5

149.4

150.2

150.7

180

153.3

149.0

151.7

151.9

152.1

210

153.8

150.7

152.1

153.1

153.4

240

154.2

151.8

153.7

154.5

154.7

TABLE 6

TIME(SEC.)

SPONGE TYPE

47

WITH NO GLASS BALOON

62

WITH 2 PARTS OF GLASS BALOON

61

WITH 3 PARTS OF GLASS BALOON

58

WITH 5 PARTS OF GLASS BALOON

55

WITH 10 PARTS OF GLASS BALOON

53

WITH 15 PARTS OF GLASS BALOON

50

TABLE 7

INITIAL

5 MIN.

10 MIN.

15 MIN.

30 MIN.

10.0

25.083

25.484

25.612

25.684

25.808

25.1

25.083

25.499

25.642

25.716

25.851

40.2

25.066

25.478

25.626

25.703

25.840

55.3

25.062

25.471

25.622

25.702

25.840

70.4

25.059

25.470

25.619

25.702

25.839

85.5

25.058

25.467

25.616

25.700

25.836

100.6

25.057

25.462

25.614

25.700

25.835

115.7

25.056

25.462

25.613

25.702

25.832

130.8

25.059

25.460

25.603

25.696

25.823

145.9

25.058

25.459

25.602

25.684

25.817

161.0

25.058

25.448

25.611

25.701

25.826

176.1

25.059

25.454

25.612

25.698

25.831

191.2

25.057

25.462

25.617

25.702

25.829

206.3

25.055

25.465

25.624

25.707

25.836

221.4

25.054

25.477

25.635

25.712

25.833

236.5

25.054

25.491

25.646

25.719

25.830

251.6

25.055

25.510

25.659

25.727

25.831

266.7

25.058

25.535

25.675

25.736

25.833

281.8

25.062

25.566

25.696

25.750

25.835

296.9

25.075

25.606

25.723

25.767

25.836

312.0

25.086

25.619

25.716

25.750

25.810

Ave.

25.063

25.493

25.637

25.712

25.831

TABLE 8

INITIAL

5 MIN.

10 MIN.

15 MIN.

30 MIN.

10.0

25.186

25.510

25.605

25.657

25.749

25.1

25.182

25.505

25.608

25.669

25.762

40.2

25.160

25.485

25.590

25.653

25.752

55.3

25.152

25.479

25.585

25.651

25.749

70.4

25.149

25.475

25.583

25.648

25.747

85.5

25.145

25.472

25.581

25.645

25.744

100.6

25.144

25.470

25.580

25.644

25.742

115.7

25.143

25.467

25.578

25.642

25.739

130.8

25.145

25.465

25.569

25.631

25.733

145.9

25.148

25.464

25.569

25.617

25.723

161.0

25.147

25.462

25.579

25.638

25.726

176.1

25.149

25.470

25.580

25.638

25.728

191.2

25.149

25.472

25.587

25.641

25.729

206.3

25.151

25.483

25.595

25.647

25.737

221.4

25.153

25.493

25.605

25.657

25.740

236.5

25.156

25.504

25.612

25.661

25.739

251.6

25.157

25.517

25.621

25.668

25.736

266.7

25.160

25.538

25.635

25.676

25.737

281.8

25.162

25.559

25.648

25.683

25.737

296.9

25.175

25.590

25.668

25.694

25.739

312.0

25.192

25.611

25.673

25.695

25.728

Ave.

25.157

25.500

25.602

25.655

25.739

TABLE 9

INITIAL

5 MIN.

10 MIN.

15 MIN.

30 MIN.

10.0

25.178

25.511

25.624

25.695

25.798

25.1

25.189

25.531

25.651

25.725

25.838

40.2

25.185

25.531

25.652

25.727

25.845

55.3

25.180

25.528

25.650

25.725

25.848

70.4

25.179

25.525

25.649

25.731

25.845

85.5

25.178

25.523

25.646

25.726

25.845

100.6

25.177

25.520

25.644

25.725

25.843

115.7

25.176

25.518

25.641

25.727

25.837

130.8

25.177

25.516

25.637

25.727

25.835

145.9

25.173

25.506

25.630

25.718

25.826

161.0

25.168

25.508

25.634

25.707

25.822

176.1

25.174

25.508

25.642

25.717

25.837

191.2

25.170

25.517

25.643

25.726

25.831

206.3

25.166

25.516

25.648

25.722

25.829

221.4

25.165

25.519

25.653

25.730

25.828

236.5

25.164

25.532

25.659

25.728

25.827

251.6

25.163

25.543

25.670

25.742

25.827

266.7

25.163

25.562

25.681

25.741

25.826

281.8

25.164

25.585

25.694

25.754

25.819

296.9

25.168

25.607

25.703

25.754

25.813

312.0

25.166

25.610

25.689

25.730

25.778

Ave.

25.173

25.534

25.654

25.727

25.828

TABLE 10

INITIAL

5 MIN.

10 MIN.

15 MIN.

30 MIN.

10.0

24.990

25.433

25.579

25.678

25.797

25.1

24.975

25.456

25.613

25.720

25.856

40.2

24.968

25.448

25.606

25.713

25.852

55.3

24.967

25.443

25.604

25.713

25.853

70.4

24.965

25.439

25.603

25.711

25.855

85.5

24.965

25.437

25.601

25.711

25.856

100.6

24.966

25.433

25.601

25.713

25.856

115.7

24.966

25.432

25.599

25.710

25.856

130.8

24.967

25.431

25.597

25.709

25.850

145.9

24.968

25.426

25.585

25.696

25.842

161.0

24.969

25.418

25.587

25.693

25.844

176.1

24.975

25.421

25.597

25.711

25.852

191.2

24.977

25.425

25.598

25.713

25.848

206.3

24.978

25.420

25.603

25.717

25.862

221.4

24.981

25.432

25.611

25.722

25.860

236.5

24.981

25.438

25.623

25.728

25.860

251.6

24.980

25.456

25.630

25.733

25.856

266.7

24.979

25.469

25.641

25.729

25.857

281.8

24.979

25.489

25.650

25.748

25.858

296.9

24.986

25.516

25.673

25.760

25.859

312.0

25.017

25.518

25.661

25.744

25.820

Ave.

24.976

25.447

25.612

25.718

25.850

TABLE 11

INITIAL

5 MIN.

10 MIN.

15 MIN.

30 MIN.

10.0

25.047

25.805

26.107

26.143

26.011

25.1

25.014

25.728

26.094

26.184

26.101

40.2

25.004

25.686

26.033

26.142

26.055

55.3

25.000

25.638

25.953

26.032

25.968

70.4

24.986

25.569

25.845

25.903

25.850

85.5

24.984

25.536

25.803

25.858

25.794

100.6

24.966

25.512

25.794

25.865

25.790

115.7

24.971

25.493

25.740

25.828

25.748

130.8

24.964

25.454

25.686

25.751

25.676

145.9

24.983

25.412

25.689

25.709

25.693

161.0

25.006

25.433

25.724

25.762

25.722

176.1

25.007

25.430

25.698

25.726

25.685

191.2

25.017

25.467

25.725

25.729

25.699

206.3

25.009

25.479

25.737

25.762

25.702

221.4

25.017

25.516

25.747

25.773

25.712

236.5

25.019

25.541

25.731

25.746

25.698

251.6

25.020

25.583

25.762

25.756

25.695

266.7

25.011

25.639

25.782

25.760

25.691

281.8

25.025

25.780

25.914

25.865

25.734

296.9

25.018

25.854

25.930

25.861

25.716

312.0

25.012

25.802

25.817

25.752

25.643

TABLE 12

NO PARTS

5 PARTS

10 PARTS

15 PARTS

0

0

0

0

0

5

0.527

0.43

0.361

0.343

10

0.535

0.574

0.481

0.445

15

0.742

0.649

0.554

0.498

30

0.874

0.768

0.655

0.582

Number	Name	Date	Kind
4136613	Namiki	Jan 1979	A
4329565	Namiki et al.	May 1982	A
4883715	Kuge et al.	Nov 1989	A
5621510	Okuda et al.	Apr 1997	A
5665505	Malhotra	Sep 1997	A
6183929	Chow et al.	Feb 2001	B1
6282399	Tokimatsu et al.	Aug 2001	B1

Rubber fixing roller

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

US Referenced Citations (7)

Foreign Referenced Citations (1)