JPH0477315B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a fixing device for heating and fixing an unfixed image, such as a powder image, to an image support material such as paper, and is applicable to an electrophotographic recording device, a laser beam, a facsimile machine, a copying machine, etc. The present invention relates to a fixing device that can be applied to an image forming apparatus.

2. Description of the Related Art Conventionally, a heat fixing method has been employed in a fixing device that fixes an unfixed image (hereinafter referred to as a toner image) formed by an image forming method such as electrophotography onto a recording material such as paper. In this type of heat fixing, a system is often used in which paper carrying a toner image is conveyed between a heating roller equipped with a heat source and a pressure roller that is in pressure contact with the heating roller.

Since an image forming apparatus that performs heat fixing requires a fixing temperature of 150 to 200 degrees, a considerable amount of time, approximately 4 minutes, is required as a wait time after turning on the main switch. Many technological innovations have been made to reduce this waiting time, such as increasing the output of electrical control means and heating sources, but these have resulted in increased costs, other problems, and increased complexity of the equipment. was.

Furthermore, there are many problems in the roller configurations of the heating roller and the pressure roller. For example, in a heating roller, heat distribution tends to be uneven in the axial direction, and heat dissipates rapidly at the ends of the roller, causing an increase in wait time. Furthermore, during the fixing operation, the temperature may easily increase at the edges due to the fact that recording materials of different widths are used and the length of the roller is longer than the width of the maximum size.

On the other hand, the devices provided on the pressure roller side can be roughly divided into the following three types, each of which has drawbacks as described below.

In the first case, a primer is coated on the core metal and a thick layer of silicone rubber or the like is provided on the surface, that is, a uniform elastic layer is provided on the roller base. In this type of roller, oil, additives, etc. must be added to reduce the elasticity of the elastic material, such as rubber, resulting in changes in the mechanical and physical properties of the elastic material. Therefore, the hardness cannot be made too low while maintaining its properties.
In addition, the pressure contact area obtained with the support material that supports the toner image formed by electrophotography is small, and the amount of heat that can be applied per unit time is small, and the elastic layer In addition, it requires a large amount of materials such as rubber, which is often used as a rubber material, and is uneconomical.Furthermore, the waiting time is large to heat the entire elastic layer, which increases the fall of the initial roller surface. I ended up
This was causing a lack of retention. Moreover, the method of increasing the number of heaters to prevent this is uneconomical.

In the second case, a fixing roller is formed by coating a core with a primer and further providing a porous member made of silicone rubber. The disadvantages of this roller are that the surface of the fixing roller is not smooth and the fixing performance is reduced, and when a release agent is applied, a large amount of release agent is contained in the porous material, which causes damage to the porous member itself. tends to deteriorate, and its durability is inferior to that of solid.

In the third case, two elastic layers are added to improve oil resistance.
There are those with multi-layered or triple-layered structures. However, when a large number of elastic layers are provided simply to improve oil resistance, the cost increases significantly due to the use of a large amount of elastic material as described above.

In the first and third cases, the heat capacity becomes extremely large due to several layers or a thick rubber layer, resulting in an increase in waiting time, and the temperature distribution over the entire length tends to be uneven, which tends to cause fixing failure. The same was true in the case of In addition, since a large amount of rubber material is required, it is expensive and has poor durability.

As mentioned above, in a fixing device having a heating roller and a pressure roller, there are not only problems with the individual components, but also additive problems that arise due to the required configuration, especially an increase in wait time. was causing

The present invention has been made in order to solve the above-mentioned problems that occur when fixing objects to be fixed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a fixing device that reduces wait time and has better fixing performance than conventional fixing devices.

Another object of the present invention is to equalize the temperature on the surface of the rotating body while maintaining the physical properties,
Our goal is to provide products with high durability.

Another object of the present invention is to provide a fixing device equipped with a rotating body that is cheaper than the conventional fixing device and achieves resource saving.

Further objects of the invention will become apparent from the description below.

The present invention, which achieves the above object, includes a heating rotating body heated by a heating source and a pressure rotating body that is in pressure contact with the heating rotating body, and an image support in which an unfixed image is supported by these rotating bodies. In a fixing device that conveys and fixes a material, the pressure rotating body has a porous elastic layer and an elastic layer provided on the porous elastic layer, and the porous elastic layer is characterized by at least a large portion of closed cells.

In FIG. 1, reference numeral 1 denotes a heat fixing roller, which is a metal roller 5 having a heating means 4 inside, and a Teflon (trade name) coating layer 6 provided on the surface of the metal roller 5. 2 is a pressure roller that comes into pressure contact with the heat fixing roller 1, and a one-component liquid is placed on the core bar 7 that is the central axis of rotation.
Apply RTV silicone rubber primer 7 ₂ , and on top of that a sponge layer 8 made of silicone sponge.
It has an elastic coating layer 9 which is made by adhering and further coating RTV silicone rubber. The surface of the pressure roller 2 is generally coated with RTV (room temperature vulcanization type) silicone rubber and then polished to adjust the shape of the roller.

Also, Teflon (product name) for heat fixing roller 1
The coating layer 6 is coated with a cleaning means such as a cleaning blade 16 and an anti-offset liquid applying means 3 (as shown in the figure, a silicone oil impregnated member 10 and a blocking member 1
2 and a continuous porous member 11) are in contact with each other.

Further, the pressure roller 2 has means for making the state of pressure contact with the heat fixing roller 1 variable, for example, supports the core bar 7 so as to be rotatable, and makes the position of the core bar 7 variable along with the attachment point ₇₁ . Arm 17 and point 17 ₁ that is the center of rotation of arm 17 and arm 17
A cam means 18 for changing the position as shown by the broken line arrow is provided as shown in the figure.

Now, the paper P having the toner image T formed by a predetermined image forming means is transferred to the transport roller pair 14.
The belt 15, which is hung on the belt 15, moves and is conveyed. Next, the paper P is transferred from the belt 15 to the guide member 13 and guided to the wide pressure contact area formed by the heating and pressure rollers 1 and 2.

On the other hand, in the wide pressure contact area, the layer 6 is uniformly heated by the heating means 4, and the elastic coating layer 9 is uniformly heated by the conductive heat from the heat fixing roller 1.
As for the pressure roller 2, due to the above structure, the coating layer 9 has higher thermal conductivity than the sponge layer 8. The time required to achieve this goal has been significantly shortened. Furthermore, since the sponge layer 8 has a large volume occupied by gas such as air in addition to the sponge component,
The thermal conductivity of this sponge layer 8 is poorer than that of the covering layer 9. In other words, the amount of heat required for the heat fixing roller 1 to maintain the entire pressure roller 2 itself at a predetermined temperature is only a small amount compared to conventional ones, and a large amount of heat is not wasted on other things. Since there is no heat, its thermal efficiency has been greatly improved, making it highly efficient. Further, even if the apparent hardness of the roller surface is the same, the above embodiment having the sponge layer 8 is more easily deformed than the one made of solid material alone, and the pressure contact area between the rollers can be made wider.

Therefore, even if the amount of heat generated by the toner is the same per unit time, heat can be applied to the toner image (or paper P) because the toner can be in contact with the toner for a long time.

Next, when the paper P enters the wide pressure contact area, the toner image supported by the paper P is permanently fixed to the paper P by uniform heat from above and below. At this time, the paper P, which is an example of the support material, has wrinkles that tend to be seen during fixing, even though no treatment such as processing it into an inverted crown shape, which is generally known as a treatment for wrinkles, has been taken. It had not occurred at all.

Next, the excellent effects of the embodiments of the present invention will be explained by statistically evaluating the results of the above embodiments.
In the following experiment, the outer diameter of the roller was 25φ, and (1) its composition was a silicone sponge layer of 6 mm thickness and a rubber layer of 1 mm thick.
(2) one with a double structure with a thick layer and the other with a single structure with an elastic layer consisting of a silicone rubber layer of only 7 mm thick, both of which were tested under the same conditions with a roller-like surface hardness of JIS-A6°. I went there. Then, this roller was placed opposite a Teflon (trade name) coated roller with an outer diameter of 25φ, and the roller was pressed with a constant pressure, and the change in the amount of nips and the incidence of wrinkles were investigated.

As a result, when using the roller (1) according to the present invention, the pressure contact width is 4.6 mm when 4 kg of full pressure is applied, and the occurrence of wrinkles is less than 0.15% when 1000 sheets of A4 size paper are continuously copied. It was hot. However, when using the conventional roller (1), the total pressure is (1)
Similarly, when 4 kg of pressure is applied, the pressure welding width is as small as 2.7 mm, and as in (1), when 1000 sheets of A4 size paper are
The occurrence of wrinkles when copying a sheet is always 0.7 to 1%.
It was within the range of

Also, when comparing the fixing properties according to the above experimental comparison,
Constant pressure during continuous copying (3.5 kg or more at full power)
If the temperature is constant (175℃ or higher), the product of pressure and temperature per unit time is almost equal, although there is a pressure difference per unit area, so the conventional method (2)
Except for the above-mentioned example (1) achieving higher image quality, no particular difference could be found between the two because of the stable condition of continuous copying.

However, in the initial state when fixing is started and in the device that brings the fixing (heating) roller and the pressure roller into contact with each other every time fixing, the above example (1) according to the present invention provides exceptional fixing performance and high quality. I was able to obtain an image with

As described above, by using the above-mentioned embodiment according to the present invention, that is, the double-structure fixing roller having a silicone rubber layer on top of a sponge layer, the following many advantages can be obtained. It became possible.

In other words, since the heat conduction of the lower roller is extremely poor due to the sponge layer, there is little drop in roller surface temperature immediately after waiting up, making it possible to prevent the deterioration of fixing performance during waiting up, which could not be solved in the past. .

Furthermore, in order to manufacture the roller as described above,
The amount of rubber used is approximately 1/2 or less, resulting in resource savings and cost savings.
I was able to contribute to the down.

Additionally, by reducing the contact pressure between the pressure roller and fixing roller, it is possible to create a large and uniform pressure contact area, which reduces the driving torque and also reduces the negative effects of compression set on the rubber roller. . Also, when a roller is formed from a single layer of silicone sponge and used for fixing, the air bubbles create areas with good fixation and areas with poor fixation, which is undesirable and requires surface smoothness. I understand.

Therefore, we conducted further experiments and investigated the thickness of the silicone rubber surface layer by varying it from 0.3 mm to 5 mm. However, if it was too thick, the effects of the sponge layer, which is rich in elasticity and multiplicity, could not be used effectively. gone,
Also, if it is too thin, it will increase the strength and manufacturing cost, and it will also affect the stability, so preferably 0.5
A thickness of mm to 2 mm is suitable, more preferably
It was found that 0.7 to 1 mm is appropriate. (However, for a roller diameter of 25φ) As shown in FIG. 3, the end surface of this pressure roller is not covered with a silicone rubber layer. That is, the rubber layer is provided only on the circumferential surface of the pressure roller, and the left and right sides have a rubber layer on the circumferential surface and a silicone rubber sponge layer on the inside. This makes the heat distribution more uniform in the longitudinal direction.

In addition, other examples of the above-mentioned examples include not only the method of covering a sponge tube to form a silicone sponge layer, but also the method of spreading rubber around a general core bar and then blowing it, and then heating it. It may be a method.

Alternatively, as a method of manufacturing at low cost, a tube of silicone rubber may be placed over the tube, placed in a mold, and NVR (low temperature vulcanization type) silicone rubber may be poured between the sponge layer and the mold using the in-die injection method. In this case, due to the precision of the release surface of the mold, there is no need for final polishing and it is suitable for mass production.

On the roller base, a layer made of a material with poor thermal conductivity and high elasticity, such as a silicone sponge layer or a porous layer made of fluororubber, and a thin layer of elastic material such as silicone rubber are provided on its surface. ,2
The layered structure makes it possible to provide a roller that has a large heat capacity, a rich surface smoothness, and can form a uniform and constant nip width with low contact pressure, eliminating the problems of conventional rollers. At the same time, it has become cheaper and more resource-saving, has greater tolerance to paper wrinkles, and has also become possible to widen the margin of error in assembly accuracy.

As explained above, this fixing device has good fixing performance during start-up, allows free elastic deformation, maintains high image quality resulting from exceptional fixing performance, and has an extremely high wrinkle prevention effect, unlike conventional fixing devices. This fixing device eliminates the need to add a filler to the fixing device, does not reduce the physical properties of the structure itself, is economical and resource-saving, and is easier to manufacture.

FIG. 2 shows a further improved embodiment of the embodiment shown in FIG. Since some parts of the configuration in FIG. 2 are the same as those in FIG. 1, the following explanation will focus on the parts that are different from those in FIG. 1. The feature of FIG. 2 is that the above-mentioned heating fixing roller has a thin metal roller 5a with a wall thickness d and a coating layer 6 of tetrafluoroethylene resin around the thin metal roller 5a.
The reason is that it has the following. In this embodiment, the roller 5
The diameter r of a is 25 mm, and the wall thickness d is 2.5 mm.
The pressure roller 2 has the aforementioned core metal 7, a primer 7 ₂ of one-component RTV silicone rubber, a sponge layer 8 made of silicone sponge, and an elastic coating layer 9 made of RTV silicone rubber. In this way, if the elastic sponge layer 8 and the elastic coating layer 9 are made of the same type of material, the bondability will be good and the durability will be improved. Furthermore, in this example, since the same type of material is used for the primer ₇₂ , the bondability to the core metal is improved.

This elastic coating layer 9 is thinner than the sponge layer 8, and the temperature distribution when heated is easily stabilized.

Another configuration in this embodiment includes the pressure adjusting means described above.

In this example, a pressure of about 15 kg/cm is applied between the heat fixing roller 1 and the pressure roller 2. The cam means 18 may be operated in response to the approach of the recording material such as paper P, or may be brought into pressure contact with a copy start signal, but normally (when not in use, the rollers 1 and 2 are in contact or separated). However, although it is preferable to provide this pressure adjustment means, it is not absolutely necessary.

Further, a contact type thermistor 13 ₁ is elastically pressed by a plate spring 24 to the circumferential surface of the heat fixing roller 1 so as to maintain a predetermined pressure contact force. This thermistor 13 ₁ has a resin tape-like material on the surface so as not to damage the surface of the fixing roller 1.
A temperature sensing element (not shown) is held by a sponge-like elastic body.

Reference numeral 23 separates the paper P from the heat fixing roller 1 with a separating claw. 22 is a guide plate on the pressure roller 2 side;
Together with the separating claw 23, a transport path for the paper P is secured.
Reference numerals 16 ₁ and 16 ₂ are paper discharge rollers that pinch and convey the fixed paper P to the outside of the image forming apparatus or to the stacking section.

In this figure, reference numeral 25 denotes an upper support workpiece that integrally holds the fixing unit (the structure of which was explained in FIG. 1, see FIG. 1), and 26 is a similar lower support workpiece. Reference numeral 27 denotes a guide member within the image forming apparatus that removably supports the support member 26 of the fixing unit. 28 is a fixed part inside the image forming apparatus;
It is spaced apart from the support wall surrounding the thermistor ₁₃₁ with a gap therebetween.

Now, the paper P having the toner image T formed by a predetermined image forming means is conveyed along with the movement of the belt 15 that is applied to the pair of conveyance rollers 14 .
Next, the paper P is transferred from the belt 15 to the guide member 13a and guided to the pressure contact area formed by the heating and pressure rollers 1 and 2. The toner image T is fused and fixed on the paper P at this pressure contact portion, and is discharged together with the paper P.

On the other hand, in the pressure contact section, the metal roller/surface 5 is uniformly heated by the operation of the heating means 4.
The above-mentioned covering layer 6 and an elastic covering layer 9 which is uniformly heated by the conductive heat from the heat fixing roller 1 are formed. Since this heat fixing roller 1 has a thin wall thickness, it reaches a predetermined temperature immediately. As for the pressure roller 2, it is heated by the high-temperature heating and fixing roller, and due to the above structure, the coating layer 9 has higher thermal conductivity than the sponge layer 8, so the wait time at startup is reduced. (The time required until the process can be started) is extremely shortened compared to the one shown in FIG. Furthermore, since the sponge layer 8 has a large volume occupied by gas such as air in addition to the sponge component, the thermal conductivity of the sponge layer 8 is lower than that of the covering layer 9. In other words, the amount of heat required for the heat fixing roller 1 to maintain the entire pressure roller 2 itself at a predetermined temperature is only a small amount compared to conventional ones, and a large amount of heat is not wasted on other things. Since there is no heat, its thermal efficiency has been greatly improved, making it highly efficient. Further, even if the apparent hardness of the roller surface is the same, the above embodiment having the sponge layer 8 is more easily deformed than the rubber solid alone, and the pressure contact area between the rollers can be made wider.

Therefore, when the paper P having the toner image T passes through this pressure contact portion, the toner image is rapidly melted and reliably fixed on the paper P because the surfaces of the rollers 1 and 2 are thermally uniform. .

The roller configuration shown in FIG. 2 will be described in further detail.

First, the thickness d of the heat fixing roller 1 will be explained. As the wall thickness d becomes thinner, the time required for heating becomes shorter, and the wait time of the entire fixing device can be reduced. When making such a roller as thin as possible, strength calculations are usually performed to maintain mechanical strength by taking into consideration the roller diameter, the Young's modulus of the material, etc.

However, it has been found that even if the thickness is set so as to obtain a predetermined strength, the temperature distribution on the surface of the heating fixing roller may become uneven, and the fixing performance may deteriorate. For example, due to the thin wall thickness, localized overheating may occur to the extent that the entire surface of the roller cannot retain the same amount of heat, or heat transfer on the roller surface may become slow, especially for the heat fixing roller. Heat mobility in the generatrix direction of the surface cannot be obtained. Also, because of its thin wall thickness, although it can quickly respond to heat, it is easily influenced by the heat release characteristics of the superheating source, causing problems in heat retention and strength, and making it difficult to achieve sufficient fixing. It may not be possible.

In other words, the minimum necessary wall thickness to shorten the weight up time should be a wall thickness that allows for easy transfer of heat in the direction of the fuser roller's generatrix, and a thickness that allows the core metal of that wall thickness to not change over time. It is most effective to bring the pressure roller into contact with pressure.

In the present invention, with respect to this wall thickness d, the outer diameter r of the rotating body is
It has been found that the above-mentioned problem can be solved by one that satisfies the formula 5/r≦d≦r/10 for (mm). Furthermore, it has been found that preferable thermal conductivity can be obtained if the wall thickness d is 3 mm or less in consideration of strength, since the heat capacity increases as the thickness increases, such as when the outer diameter r is 30 mm or more.

Furthermore, in this embodiment, there are cases where it is desired to solve the above-mentioned problem of the heat fixing roller and further shorten the wait time, or where priority is given to mechanical strength and the thickness or material of the fixing roller cannot be freely selected from a thermal perspective. It has a configuration that solves the case. That is,
Due to the thin fixing roller, the disadvantage that heat transfer in the generatrix direction is not carried out is compensated for by the structure of the rollers that are pressed against each other. This problem can be solved by bringing a pressure roller having a smooth surface into contact with the surface of the pressure roller.

As a result, most of the heat from the surface of the fixing roller is transmitted to the pressure roller, except for heat dissipation into the air and heat escape to the fixing roller support member.

At this time, since the inside of the pressure roller is a porous layer that is difficult to conduct heat, heat is quickly transmitted only to the surface of the coating layer, which helps heat transfer in the direction of the generating line of the fixing roller. Furthermore, since the heat transfer to the pressure roller is significantly worse than that of conventional solid rubber rollers, it has become possible to shorten the weight-up time and to obtain a roller configuration with almost no fall-off phenomenon during the fixing operation.

Therefore, even if the amount of heat generated by the toner is the same per unit time, heat can be applied to the toner image (or paper P) because the toner can be in contact with the toner for a long time.
At this time, the paper P, which is an example of the support material, has wrinkles that tend to be seen during fixing, even though no treatment such as processing it into an inverted crown shape, which is commonly used as a treatment for wrinkles, has been taken. It never occurred.

In FIGS. 3 and 4, the fixing roller ₁₁ has a cylindrical shape. This roller ₁₁ is made by coating the surface of a thin aluminum pipe ₅₁ with a 25-30 μm polytetrafluoroethylene resin layer ₆₁ as an offset prevention layer. A notch 30a is provided at the end of the fixing roller ₁₁ , and serves as a fitting groove for a drive gear (described later). In addition, A in the figure
is an area through which B5 size sheets pass, B is an area through which A4 size sheets pass, and both ends thereof are sheet non-passage areas C.

31a and 31b are rolling bearings that rotatably support the fixing roller ₁₁ . Note that this bearing 31a,
31b is attached to a support frame (not shown) of the fixing device. In addition, 30 is a drive gear, and the notch portion 3
It is fitted and fixed to the fixing roller 1 ₁ at 0a,
Drive from a drive source 33 on the copying machine main body side is transmitted via a gear 29 on the main body side to rotate the fixing roller ₁₁ . Furthermore, 4 ₁ is a support member 4 that also serves as an electrode.
a, 4b as a heat source, a temperature sensing element ₁₃₁ in contact with the surface of the fixing roller ₁₁ , and a control circuit (not shown).
The fixing roller ₁
Controlled off. Note that the drive gear 30 is fitted into the notch 30a and fixed to the fixing roller 1 with a screw or the like.
Since it is fixed on the circumferential surface of the fixing roller ₁ , it also prevents the fixing roller ₁₁ from shifting with respect to the bearings 31a and 31b.

2 ₁ is a pressure roller, which faces the fixing roller 1 ₁ under pressure. A heat-resistant porous elastic layer 8 ₁ is provided around a stainless steel core 7, and the surface is covered with a very thin silicone layer. It is covered with a rubber elastic layer ₉₁ . This core metal 16 is also rotatably supported by rolling bearings 17a and 17b.

In this embodiment as well, the above-mentioned effects are obtained, and the uniformity of the surface temperature of the fixing roller 1 ₁ is further promoted by the action of the elastic layer 9 ₁ of the pressure roller 2 ₁ , and the characteristics of each roller are A certain reduction in wait time can be further improved reciprocally.

In this embodiment, the fixing roller 1 ₁ and the pipe 5 ₁
is a cylinder that is open at both ends and has approximately the same diameter. Therefore, in this embodiment, the excess heat is efficiently released to the outside, so that it is possible to effectively prevent the temperature increase in the sheet non-passing area C on the roller circumferential surface. Moreover, since the amount of heat transferred to the roller support portion during heating is reduced, the circumferential surface of each roller 1 ₁ , 9 ₁ can quickly reach a predetermined uniform temperature. Furthermore, in this embodiment, the pipe ₅₁ is located in the sheet passage area (A or B).
and the bearing portion to which the bearing supporting the pipe ₅₁ is attached are both on the same generatrix. Therefore, there is no risk of uneven thickness of the roller, which may occur when conventional fixing rollers (particularly the example shown in Figure 2) are manufactured using methods such as bulge pressing or cold tube forging. Even so, the heat distribution on the circumferential surface of the roller became uniform, and the temperature was raised to a uniform temperature.

Therefore, in this embodiment, the wall thickness of the pipe 5 ₁ is uniform over both the sheet passage area (A or B) and the bearing portion where the bearing supporting the pipe 5 ₁ is attached, that is, over the entire area of the pipe 5 ₁ . It was possible to form a thin wall, reduce non-uniformity in heat distribution, and maintain a uniform temperature around the roller surface. Furthermore, the manufacturing process could be shortened.

Examples of heat-fixing rollers that can be applied to the above apparatus and achieve substantially the same effect are shown in FIGS. 5 to 7.

In the embodiment shown in FIG. 5, instead of using drive gears 29 and 30 to prevent the cylinder 36 from coming off or slipping, as shown in FIG. It engages with grooves 35a and 35b provided on the circumferential surface of the cylinder 36. This also prevents the cylinder 36 from coming off or slipping from the bearings 31a and 31b, allowing the cylinder 36 to always rotate at a predetermined position.

Further, FIG. 6 shows another embodiment.

In this embodiment, a drive gear 39 is fixedly installed inside an end portion 37 of the cylinder 36, which is a non-sheet passing portion. The drive gear 39 also fits into the notch 38 of the cylinder 36. In this embodiment, the rate at which the cylinder end 37 is opened is slightly reduced compared to the previous embodiment due to drive transmission, but the other end of the cylinder 36 is completely opened, so that the above-mentioned sufficient effect can be obtained. be able to.

Furthermore, FIG. 7 shows another embodiment of drive transmission.

In this embodiment, a drive roller 40 is pressed against the circumferential surface of the end 37 of the cylinder 36, and the cylinder 36 is rotated by the rotational drive of the drive roller 40.
The drive roller 40 is a drive source (not shown) on the main body side.
It receives the drive from the machine and rotates.

Note that in all of the embodiments described above, the drive on the main body side is transmitted to the fixing rollers 1 ₂ , 1 ₃ , 1 ₄ , but for example, the drive may be transmitted to the pressure roller in a similar manner. . Furthermore, the drive may be transmitted to both rollers.

In the above embodiment, since heat cannot be accumulated inside the fixing roller, the temperature rise of the roller circumferential surface in the sheet non-passing region can be suppressed to within about 30 to 40°C. Also, when heating starts, the time required for the heater to turn on and the roller circumferential surface to uniformly reach around 180°C is compared to when using a roller with a support part that has a small diameter end. We were able to reduce the time by approximately 5 seconds (it used to take 20 seconds, but now it takes 15 seconds).

This eliminates the risk of uneven thickness of the roller, which occurs when manufacturing the fixing roller by conventional methods such as bulge pressing or cold tube forging. With this heated fixing roller, the heat distribution becomes uniform over the entire circumferential surface of the fixing roller and the pressure roller, and the temperature is raised to a uniform temperature.

Next, a specific example to which the present invention is applied will be explained,
The present invention will be explained in detail.

<Specific example 1> Total length 230 [mm] and outer diameter 25 as a heating fixing roller
[mm] / wall thickness 1.6 [mm] aluminum rotating body,
Coated with a 25μm tetrafluoroethylene layer,
A pressure roller with a built-in 1.2KW halogen heater is used, and the pressure roller has an outer diameter of 24mm and an inner layer of silicone sponge with a thickness of 6mm.
A rubber surface layer with a thickness of 0.7 mm was used.
Also, the temperature of the heating roller surface is normally set at 180℃.
The heater was made to operate when the main switch was turned on.

In this specific example, even in the normal pressure-welded state, the wait time is significantly longer than before (from 4 minutes to
What used to take 5 minutes was reduced to about 15 to 20 seconds.
The wait time was further reduced compared to (1) a single silicone rubber roller pressed against this heating roller, or (2) a normal heating roller pressed against this pressure roller. Furthermore, a much more uniform temperature distribution was obtained than in (1) and (2), resulting in exceptional fixing performance and high-quality images.

<Specific Example 2> The heat fixing roller 1 is a cylindrical roller with an outer diameter of 25 mm and a length of approximately 280 mm, and a coating layer of tetrafluoroethylene-barfluoroalkoxyethylene copolymer (PFA) is coated with a coating layer of 25 μm on an aluminum cylindrical roller with a wall thickness of 1.6 mm. It has a thickness of 〓.

Pressure roller 2 is a roller with an outer diameter of approximately 24 mm and a length of approximately 230 mm, and has a 6 mm thick HTV (high temperature vulcanization type) silicone sponge layer on a 10φ core metal, and a
It has a 0.7mm to 1mm RTV (room temperature vulcanization type) silicone rubber layer.

A gear is fitted to the surface part of the heat fixing roller 1 that does not contact the pressure roller 2, and a gear of 1.0 mm is fitted inside the gear.
It has a built-in ~1.2KW halogen heater. The heat fixing roller 1 and the pressure roller 2 always have a total pressure of about 7
Kg pressure welded. The width of the pressure welding part is approximately 2.5mm
~3.0mm.

The heat fixing roller 1 is driven, and the pressure roller 2 is caused to follow this.

The hardness of the silicone sponge layer above is Asker-C.
When measured with a type of sponge rubber hardness meter (manufactured by Koubunshi Kagakusha) with a load of 300g, it was 27° ± 3°.

A process of fixing a powder image onto paper was performed using the fixing device configured as described above. As a result, the wait time from the time when current was applied to the heater of the heat-fixing roller until the surface temperature of the fixing roller reached 180° C. was reduced to about 15 seconds. In addition, the pressure roller surface temperature was able to rise to 160°C. Furthermore, the powder image could be fixed on paper with almost uniform fixability.

This excellent and revolutionary result can be understood by comparing it with the waiting time of any conventional heat fixing device, which takes about 4 to 10 minutes. Furthermore, since the pressure roller of the conventional device has a rubber layer in units of 10 mm, it could only be heated to a maximum temperature of about 70°C. That is, it is understood that the pressure roller of the above specific example can rapidly heat up to 160° C., thereby reducing the waiting time, and has sufficient elasticity, thereby improving fixing performance.

The silicone sponge layers of Examples 1 and 2 were formed by a tubing method or an injection method using a paper tube. In the tubing method, high-temperature vulcanized silicone rubber compound is poured out from a container with a ring-shaped opening, and then the cylindrical rubber tube is placed inside a cylindrical heater and heated from the surrounding area to foam and form a sponge tube. It is something. The shape of the sponge tube is determined by the inner diameter of the ring-shaped opening and the inner diameter of the cylindrical heater. The pressure roller was molded using the following procedure. Since this sponge tube has a skin layer on its surface, the inner diameter of the tube is expanded by sucking the skin layer from the surrounding area. A core bar whose surface is coated with a silicone primer for adhesion is inserted into this inner diameter. After this, the suction is released and the sponge tube is glued to the core metal.
Furthermore, the skin layer on the surface of the sponge tube is scraped to form a sponge layer of a predetermined thickness. The surface of this sponge layer is laminated with RTV silicone rubber to a predetermined thickness. Thereafter, final polishing was performed to obtain the above-mentioned pressure roller.

In the injection method using a paper tube, a primer-treated core metal is inserted into a cylindrical paper tube of a predetermined diameter, and a high-temperature vulcanized silicone rubber compound is injected between the paper tube and the core metal and heated. to form a spongy silicone rubber layer. Furthermore, after this, the paper tube is removed and polished. Such a process is called an injection method using a paper tube. Hereinafter, the pressure roller may be molded using the above-mentioned RTV silicone rubber laminate coating.

In the above-described embodiments and specific examples, the configuration of the pressure roller has a great effect on the heating roller in terms of uniform temperature distribution and shortening of wait time.

This is because the heat conduction of the roller is extremely poor in the sponge layer, so there is little drop in roller surface temperature immediately after weight-up, and it is possible to prevent the deterioration of fixing performance when weight-up, which could not be solved in the past. .

That is, by having a higher thermal conductivity in the surface layer than in the inner layer of the roller, such as a sponge layer, thermal efficiency can be improved and heat can be used to uniformize the temperature on the surface of the heating roller. .

Furthermore, like a sponge layer, the elastic modulus of the inner layer of the roller is greater than that of the surface layer, so that a large pressure contact portion can be stably formed with the surface of the heating roller. Therefore, more favorable effects such as being able to immediately respond to the heat conduction of the heating roller and reliably guaranteeing the surface temperature of the heating roller are also achieved in the examples in the embodiments.

Furthermore, since the rollers are manufactured as described above, the amount of rubber used is approximately 1/2 or less, contributing to resource conservation and cost reduction.

Furthermore, since the contact pressure between the pressure roller and the fixing roller can be reduced, and a large and uniform pressure contact area can be obtained, the driving torque can also be reduced, and furthermore, the adverse effects caused by compression set of the rubber roller can be reduced.

Furthermore, the present inventor conducted experiments to obtain a more preferable embodiment, and found that one that satisfies the following requirements is even more preferable.

When a roller is formed from a single layer of silicone sponge and used for fixing, the air bubbles may create areas with good fixation and areas with poor fixation, which is undesirable and has a smooth surface. I found this to be preferable. In other words, it is preferable for the surface layer of the pressure roller to have surface smoothness because it can provide a higher level of fixation.

Also, regarding the thickness of the surface layer from another perspective,
Silicone surface layer thickness experiments ranging from 0.3 mm to 5 mm thickness were investigated. As a result, if it is too thick, the effect of the sponge layer, which is rich in elasticity and restorability, cannot be used effectively, and if it is too thin, the strength and manufacturing costs will increase, and stability will be affected.
It was found that the thickness is preferably 0.01 mm to 2 mm, more preferably 0.5 mm to 2 mm, and even more preferably 0.7 mm to 1 mm (however, if the roller diameter is 25φ ).

Considering this comprehensively and other results (not listed), it is preferable for the surface layer to have good thermal conductivity to have a thickness that is 1/4 or less of the thickness of the elastic lower layer such as a silicone sponge layer. I found out.

In addition, in other embodiments of the above-mentioned pressure roller, in order to form a silicone sponge layer, there is not only a method of covering a tube of sponge, but also a method of applying rubber around a general core metal and blowing it, and then applying heat. It may also be a method of letting it flow.

In addition, as a method of producing the sponge layer at a low cost, when creating the sponge layer in a mold, the surface layer can be formed at the same time without foaming the outside, or the in-die extension method can be used, in which a tube of silicone rubber is covered and then placed in the mold. NVR (low temperature vulcanization type) silicone rubber may be poured between the sponge layer and the mold. In this case, due to the precision of the release surface of the mold, there is no need for final polishing and it is suitable for mass production.

The pressure roller has an elastic layer on the base made of a material with relatively poor thermal conductivity and rich elastic restoring force, such as a silicone sponge layer or a porous layer made of fluororubber, and a thin layer of heat conductive material such as silicone rubber. Any rotating body may be used as long as it has a multi-layer structure and has a heat-resistant layer on its surface. This makes it possible to form a uniform and constant nip width (pressing force) with low contact pressure.

Although the surface release material provided on the surfaces of the heat fixing roller 1 and the fixing roller ₁₁ may not be provided, it is preferable to provide it in order to prevent offset. This material includes tetrafluoroethylene,
Fluororesins such as FEP resin and PEA resin, silicone resins, rubber materials, etc. are suitable.

Although not explained in the explanation of FIGS. 1 and 2 above, the pressure contact force between the fixing roller and the pressure roller can be small because the amount of deformation of the pressure roller is large and the thermal efficiency at the pressure contact portion is extremely favorable. but,
In order to improve durability, the total pressure applied between the fixing and pressure rollers should be 20 kg or less when fixing objects such as unfixed images or conveying recording materials such as paper. preferable. This structure is also effective in preventing paper wrinkles.

As described above, the fixing device has a thin rotary body and a heat-resistant rotary body, and has a porous elastic layer such as a sponge in the inner layer and a heat-resistant surface layer such as a thin silicone rubber on its surface. By using a heat fixing device, the mutual action of both rotating bodies occurs, making it possible to obtain an ideal device with an extremely short wait time. Ta.

Furthermore, by having a thin rotating body, it was possible to significantly reduce the wait time during startup.

The terms "sponge" and "sponge layer" above mean ceuars ayer (bubble layer) in English, and specifically, it has a large amount of gas-containing bubbles, most of which are Expanded foams or expanded ces are closed cell cells in which each cell is independent and isolated from others.

However, even if this "sponge" contains some open cells (sponge) whose cells communicate with each other, it is included in the present invention as long as the desired elasticity and desired heat insulation properties are obtained. .

ceuar in this example and the following examples
Ayer is mostly composed of closed cells containing gas (for example, air or vaporized additives in rubber), and has a resin film such as silicone rubber as a partition wall. This has the advantage that closed cells have a higher heat insulating effect than open cells, have more elasticity, and are easier to obtain a predetermined pressure.

The present invention relates to the configuration of a fixing device for heating and fixing an unfixed image, such as a powder image, to an image support material such as paper, and is a new and innovative device that significantly shortens the conventional wait time.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of one embodiment of the present invention, FIG. 2 is an explanatory diagram of another embodiment of the present invention, FIG. 3 is an explanatory diagram of another embodiment of the present invention, and FIG. 4 is an explanatory diagram of another embodiment of the present invention. FIG. 3 is an explanatory diagram of a main part, and FIGS. 5 to 7 are explanatory diagrams of embodiments of a heat fixing roller that can be applied to the present invention. 1 is a heat fixing roller, 2 is a pressure roller, 8
9 is a sponge layer, 9 is an elastic coating layer, r is a radius, and d is a wall thickness.

Claims (1)

[Claims] 1. An image support material comprising a heating rotating body heated by a heat source and a pressure rotating body that is in pressure contact with the heating rotating body, and supporting an unfixed image with these rotating bodies. In the fixing device that performs fixing by conveying, the pressure rotating body has a porous elastic layer and an elastic layer provided on the porous elastic layer,
A fixing device characterized in that the porous elastic layer has at least a large portion of closed cells.