JPH10133503A - Heating/fixing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heating/fixing device capable of preventing abnormality in fixing (hot offset) and carrying, in end parts and further, degradation in reliability caused by the overheating by suppressing the rising of the temp. in the end parts. SOLUTION: A pressure roller 20 arranged in press-contact with a fixing roller 10 is constituted in such a manner that a core metal 22 is covered with an elastic layer 24 and a plurality of metallic thin wires 26 having high-heat conductivity which are extended in the same direction as the axial direction of the pressure roller 20 are buried with uniform intervals along the circumference of the elastic layer 24, in its surface layer. Therefore, even if heat is radiated through a small-width printing paper in the central part of the pressure roller 20, but not radiated in the end parts, in passing the printing paper, heat conduction by the thin wires 26 having the high-heat conductivity which are buried in the surface layer of the elastic layer 24 is executed so that the heat in the end parts is transferred to the central part and the distribution of the temp. in the axial direction is uniformized all around the periphery of the pressure roller 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electrophotographic apparatus,
The present invention relates to a heat fixing device used for a copying machine, a facsimile, and the like, and more particularly to a heat fixing device having a small heat capacity of a base for power saving.

[0002]

2. Description of the Related Art In recent years, due to environmental regulations and increasing awareness of environmental protection, various types of electrophotographic apparatuses have been required to be energy saving apparatuses. As one of them, there is an electrophotographic apparatus in which a fixing heater is turned off when not in use and the fixing unit is not heated except during use. However, in such an energy-saving electrophotographic apparatus in which the fixing heater is turned off when not in use, it is required to quickly raise the temperature of the fixing unit during use. For this reason, for example, a technique of starting the temperature rise of the fixing heater in response to the approach of the user by a sensor has been proposed, but in order to realize the rapid rise in the temperature of the fixing unit itself, the following is required. Such ingenuity has been made. For example, in a system in which a halogen heater is used to heat the inside of a metal substrate, in order to satisfy the demand for rapid temperature rise of the fixing unit,
Substrates with a thickness of 1 mm or less have been reduced in thickness.

As another means, there is a fixing roller of a direct heating type having a heating layer. Again,
As in the above case, a more rapid temperature rise is achieved by combining the thinning of the substrate.

[0004]

However, any of the above-described fixing rollers that rapidly heats up has a technical problem of a rise in end temperature. This temperature rise at the end means that when a printing paper having a smaller width, for example, a vertical width of B5 size, is continuously passed with respect to the maximum paper passing width of the electrophotographic apparatus, for example, the vertical width of A3 size, the center is increased. Heat is supplied from the heater by the amount of heat consumed by the printing paper in the section, and a certain range of temperature is maintained, but since heat is not consumed by the printing paper at both ends, the heat is fixed to the pressure roller. This is a phenomenon in which the temperature accumulates on the roller and rises.

[0005] In addition to the end portion temperature rise, the heat-resistant life of the bearing member is shortened. In addition, when a large-width printing paper is passed immediately after the end portion temperature rise, the end portion at which the temperature is higher than the set temperature becomes higher. Fixing error (hot offset)
And a transport error occurs. Therefore, there is an advantage that the smaller the rise in the temperature of the end portion is, the more wasteful heat is not generated and the life of the fixing unit is extended.

The following method can be considered as a method for suppressing the temperature rise at the end. (1) Normally, rubber is used for the surface of the pressure roller. For example, a metal having high thermal conductivity is used instead of the rubber. This makes it possible to make the temperature distribution in the axial direction of the pressure roller uniform, so that the end portion temperature rise can be reduced. However, in this case, the metal is a rigid body, unlike rubber, which is an elastic body, so that the pressure roller does not deform. For this reason, a nip is not formed, and the time for applying heat and pressure necessary for fixing the toner is shortened, which causes a problem that a fixing failure occurs.

(2) Highly heat conductive particles are dispersed inside the pressure roller. This makes it possible to make the temperature distribution in the axial direction of the pressure roller uniform, so that the end portion temperature rise can be reduced. However, in the case of this particle dispersion, since the highly thermally conductive particles themselves do not completely contact in the axial direction, the effect of uniformizing the temperature distribution in the axial direction is low, and the rise in the end temperature cannot be sufficiently reduced. . Also, if the particle density is increased so that the particles come into contact with each other in order to enhance the effect of uniforming the temperature distribution in the axial direction, the rigidity of the elastic layer of the pressure roller increases, so that the pressure roller is less likely to be deformed, A nip is not formed due to the same phenomenon as in the case of the above (1), and there is a problem that a fixing failure occurs.

In view of the foregoing, the present invention has been made in view of the above-described problems, and suppresses a rise in end temperature to prevent a fixing abnormality (hot offset) and a conveyance abnormality at the end, and to prevent excessive temperature rise. It is an object of the present invention to provide a heat fixing device capable of preventing a decrease in reliability.

[0009]

The above object can be attained by the following heat fixing apparatus according to the present invention. That is, in the heat fixing device according to the first aspect, a rotatable pressure roller having a surface covered with an elastic body is pressed against a heated cylindrical fixing roller, and the fixing roller and the pressure roller are rotated while rotating. In a heat fixing device that sandwiches printing paper and fuses toner to the printing paper, a high heat conductive thin wire extending in the same direction as the axial direction of the pressing roller is embedded inside the elastic body surface layer of the pressing roller. It is characterized by having been done.

In the heat fixing device according to the first aspect of the present invention, the high heat conductive thin wire extending in the same direction as the axial direction is embedded inside the elastic body surface layer of the pressure roller, so that the width is narrow. When the printing paper is passed through, even if heat is radiated only through the printing paper at the center and not from the end, heat conduction by the highly heat conductive thin wire embedded in the elastic layer of the pressure roller As a result, the heat at the end is transmitted to the center and the temperature distribution in the axial direction is made uniform, so that the rise in temperature at the end can be reduced. Therefore,
Deterioration of the heat-resistant life of the bearing member, or abnormal fixing (hot offset) at the edge where the temperature is higher than the set temperature when a large width of printing paper is passed immediately after the edge temperature rises
Further, it is possible to prevent occurrence of a transport abnormality.

According to a second aspect of the present invention, there is provided a heat fixing apparatus according to the first aspect, wherein the thin wire is made of metal.

In the heat fixing device according to the second aspect of the present invention, when a narrow printing paper is passed, the printing paper is passed only in the center portion by using a thin metal wire as the high thermal conductive thin wire. Even if the heat is not dissipated from the end, the heat at the end is transmitted to the center by the heat conduction by the highly heat conductive thin metal wire embedded in the elastic layer of the pressure roller, and the temperature distribution in the axial direction Are made uniform, so that an increase in end temperature can be reduced. In addition,
Although this thin metal wire is a rigid body, since the embedding direction is the same as the axial direction of the pressure roller, the elastic layer can be deformed without substantially hindering the deformation of the elastic body of the fixing roller. Therefore, a reliable nip width can be obtained.

According to a third aspect of the present invention, there is provided a heat fixing apparatus according to the first aspect, wherein the thin wire is hollow, and a heat storage fluid flows in the hollow thin wire. And

Thus, in the heat fixing device according to the third aspect, the heat storage fluid flows through the hollow thin wire extending in the same direction as the axial direction inside the elastic body surface layer of the pressure roller, so that the width is reduced. When a narrow printing paper is passed, even if heat is radiated through the printing paper only at the center and not radiated from the end, the heat at the end is centered by the flow of the heat storage fluid inside the hollow thin wire. The temperature distribution in the axial direction is transmitted to the portion and the temperature distribution in the axial direction is made uniform, so that the temperature rise at the end can be reduced. The heat storage fluid flowing in the hollow fine wire includes, for example, a heat storage gas, liquid, or powder.

According to a fourth aspect of the present invention, in the heat fixing apparatus according to the second or third aspect, a plurality of the thin wires are embedded in the same direction as the axial direction of the pressure roller. And

Thus, in the heat fixing device according to the fourth aspect, since a plurality of fine wires having high thermal conductivity extending in the same direction as the axial direction are provided inside the elastic body surface layer of the pressing roller, Since the temperature distribution can be made uniform over the entire circumference of the pressure roller, the temperature rise at the end can be reduced more quickly and effectively.

According to a fifth aspect of the present invention, there is provided a heat fixing apparatus according to the third aspect, wherein a plurality of the hollow fine wires are buried in the same direction as the axial direction of the pressure roller. One end of the thin wire is connected to form one flow path, and the heat storage fluid circulates in the hollow thin wire forming the one flow path.

Thus, in the heat fixing device according to the fifth aspect, the inside of the hollow fine wire that extends in the same direction as the axial direction inside the elastic body surface layer of the pressure roller and meanders to form one flow path. By circulating the heat storage fluid, the heat at the end is transmitted to the center by the circulation of the heat storage fluid in the hollow wire, and the axial temperature distribution is made uniform over the entire circumference of the pressure roller. Therefore, it is possible to more quickly and effectively reduce the end portion temperature rise.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of the present invention will be described. (First Embodiment) FIG. 1 is a sectional view of a main part showing a heat fixing device according to a first embodiment of the present invention, and FIG. 2 is an axial sectional view of a pressure roller. The fixing roller 10 has a hollow cored bar 12 made of aluminum or the like covered with a release layer 14 made of Teflon or the like. And hollow core 1
Although not shown, a heating element such as a rod-shaped halogen heater for heating the fixing roller 10 is inserted in 2.

The pressure roller 20 is disposed in pressure contact with the fixing roller 10, and has an elastic layer 2 made of silicone sponge rubber or the like on a metal core 22 made of iron, aluminum or the like.
4 are coated. Then, copper extending in the same direction as the axial direction of the pressure roller 20 is provided inside the surface layer of the elastic layer 24.
The present embodiment is characterized in that a plurality of high thermal conductive metal thin wires 26 made of aluminum or the like are buried at equal intervals along the circumference of the elastic layer 24.

While rotating the fixing roller 10 and the pressure roller 20 configured as described above, the printing paper is passed between the fixing roller 10 and the pressure roller 20 as shown by arrows in FIG. Then, the toner is fused to the printing paper. When the printing paper is passed, if the printing paper is narrower than the maximum width of the fixing roller 10 and the pressing roller 20, heat is radiated through the printing paper at the center of the pressing roller 20. No heat is dissipated by the printing paper at the end where paper is not passed.

However, in the present embodiment, a plurality of high thermal conductive metal wires 2 buried at equal intervals along the circumference inside the surface layer of the elastic layer 24 of the pressure roller 20.
6, the heat at the ends is transmitted to the center, the temperature distribution in the axial direction is made uniform over the entire circumference of the pressure roller 20, and the temperature rise at the ends can be suppressed. Therefore, it is possible to prevent the fixing abnormality (hot-off method) and the conveyance abnormality at the end.

The high thermal conductive thin metal wire 26 embedded in the surface layer of the elastic layer 24 of the pressure roller 20 is a rigid body, but extends in the same direction as the axial direction of the pressure roller 20. Further, since a plurality of the elastic layers 24 are buried at equal intervals along the circumference of the elastic layer 24, the elastic layer 24 does not hinder the elastic layer 24 from being crushed in the normal direction.
A sufficient nip can be formed at the contact portion with zero.
Therefore, there is no problem that a fixing defect occurs due to insufficient heating and pressing.

In the first embodiment, the fine metal wire 26 having high thermal conductivity is formed along the circumference of the elastic layer 24 by one.
Although only the layer is buried, without being limited to this,
Two or more layers may be used. Therefore, when the heat radiation efficiency of the central part and the end part is largely different, the heat conduction is enhanced by burying the high thermal conductive thin metal wire 26 in the multilayer structure, and when the difference of the heat radiation efficiency is small, the nip width is increased. In order to secure a large space, it is possible to selectively use such as embedding in a one-layer structure.

(Second Embodiment) FIG. 3 is a sectional view of a main part showing a heat fixing device according to a second embodiment of the present invention.
FIG. 4 is a developed view in which an elastic layer in which the hollow fine wire of the pressure roller is embedded is developed in a tangential direction. Note that the same components as those of the heat fixing device shown in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. The fixing roller 10 has the same structure as that of the first embodiment, and the release layer 14
A heating element such as a rod-shaped halogen heater for heating is inserted in the hollow cored bar 12.

The pressure roller 30 is disposed in pressure contact with the fixing roller 10 as in the first embodiment, and the elastic layer 24 is coated on the core metal 22. Inside the surface layer of the elastic layer 24, a plurality of hollow fine wires 32 extending in the same direction as the axial direction of the pressure roller 30 are buried at equal intervals along the circumference of the elastic layer 24, and these hollow fine wires are embedded. Are connected to each other to form a single flow path, and the hollow thin wire 32 extending in the same direction as the axial direction of the pressure roller 30 and meandering to form a single flow path. A fluid such as a heat storage gas, a liquid, or a powder is circulated by a circulating device (not shown) such as a small pump installed inside the elastic layer 24, the core metal 22, or the outside of the pressure roller 30. The present embodiment is characterized in that (not shown) circulates.

While rotating the fixing roller 10 and the pressure roller 30 configured as described above, the printing paper is passed between the fixing roller 10 and the pressure roller 30 as shown by arrows in FIG. Then, the toner is fused to the printing paper. When the printing paper is passed, if the printing paper is narrower than the maximum width of the fixing roller 10 and the pressing roller 30, heat is radiated through the printing paper at the center of the pressing roller 30. No heat is dissipated by the printing paper at the end where paper is not passed. However, in the present embodiment, one channel is buried inside the surface layer of the elastic layer 24 of the pressure roller 30 at equal intervals along the circumference thereof, extending in the same direction as the axial direction, and meandering. Hollow thin wire 3
Since the heat storage fluid circulates through the inside of the pressure roller 2, the heat at the end is transmitted to the center, and the temperature distribution in the axial direction is made uniform over the entire circumference of the pressure roller 30, thereby suppressing the temperature rise at the end. Can be. Therefore, similarly to the case of the first embodiment, it is possible to prevent the fixing abnormality (hot-off method) and the conveyance abnormality at the end portion.

In the first and second embodiments, the method of heating the inside of the metal base of the fixing roller 10 by a heating element such as a halogen heater has been described.
The present invention is not limited to this method, and it is needless to say that the present embodiment can be applied to, for example, a direct heating method. In this case, a heat generating layer is formed on the outer or inner surface of the hollow cored bar of the fixing roller.

[0029]

As described above, according to the heat fixing apparatus of the present invention, the following effects can be obtained. In other words, according to the heat fixing device of the first aspect, the high heat conductive thin wire extending in the same direction as the axial direction is embedded inside the elastic body surface layer of the pressure roller, so that the printing paper having a narrow width is formed. Even if is passed through, heat at the end is transmitted to the center by heat conduction by the high thermal conductive thin wire embedded in the elastic layer of the pressure roller, so that the temperature distribution in the axial direction is uniformed, The end temperature rise can be reduced. Therefore, a reduction in the heat-resistant life of the bearing member, and occurrence of a fixing error (hot offset) and a transport error at the end portion which is higher than the set temperature when a large width of printing paper is passed immediately after the end portion temperature rises. Can be prevented.

Further, according to the heat fixing device of the second aspect, by using a thin metal wire as the high thermal conductive thin wire, the same effect as the heat fixing device of the first aspect is obtained, and the thin metal wire is used. Even if is a rigid body, since the embedding direction is the axial direction of the pressure roller, the elastic layer of the fixing roller does not hinder deformation, so a sufficient nip is formed at the contact portion with the fixing roller. can do. Therefore, it is possible to prevent the occurrence of fixing failure due to insufficient heating and pressing.

Further, according to the heat fixing device of the third aspect, the heat storage fluid flows through the hollow thin wire extending in the same direction as the axial direction inside the elastic body surface layer of the pressure roller. Even when a narrow printing paper is passed, the heat at the end is transferred to the center by the flow of the heat storage fluid inside the hollow wire, so that the temperature distribution in the axial direction is uniformed and the temperature at the end rises. Can be reduced. Therefore, a reduction in the heat-resistant life of the bearing member, and occurrence of a fixing error (hot offset) and a transport error at the end portion which is higher than the set temperature when a large width of printing paper is passed immediately after the end portion temperature rises. Can be prevented.

Further, according to the heat fixing device of the fourth aspect, since there are a plurality of high thermal conductive thin wires extending in the same direction as the axial direction inside the elastic body surface layer of the pressure roller, the heat fixing device can be arranged in the axial direction. Since the temperature distribution is made uniform over the entire circumference of the pressure roller, it is possible to more quickly and more effectively reduce the end temperature rise than in the case of the heat fixing device according to claim 2 or 3.

According to the heat fixing device of the present invention, a plurality of hollow thin wires are buried in the same direction as the axial direction of the pressure roller, and the ends of these hollow thin wires are connected to one another. The heat storage fluid in the hollow thin wire is formed by circulating a heat storage fluid in a hollow thin wire that extends in the same direction as the axial direction and meanders while forming a single flow channel. The heat is transferred to the central portion by the circulation of the material, and the temperature distribution in the axial direction is made uniform over the entire circumference of the pressure roller. The temperature rise at the end can be reduced.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a main part showing a heat fixing device according to a first embodiment of the present invention.

FIG. 2 is an axial sectional view of the pressure roller of FIG.

FIG. 3 is a cross-sectional view of a main part showing a heat fixing device according to a second embodiment of the present invention.

4 is a developed view in which an elastic layer of the pressure roller of FIG. 3 in which a hollow fine wire is embedded is developed in a tangential direction.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Fixing roller 12 Hollow core metal 14 Release layer 20 Pressure roller 22 Core metal 24 Elastic layer 26 Metal thin wire 30 Pressure roller 32 Hollow thin wire

Claims (5)

[Claims] 1. A heated cylindrical fixing roller is pressed against a rotatable pressure roller having an elastic body coated on the surface thereof, and the printing paper is held while rotating the fixing roller and the pressure roller. In a heat fixing device for fusing toner to printing paper, a highly heat conductive thin wire extending in the same direction as the axial direction of the pressure roller is embedded inside the elastic body surface layer of the pressure roller. Heat fixing device. 2. The heat fixing device according to claim 1, wherein the fine wire is made of metal. 3. The heat fixing device according to claim 1, wherein the fine wire is hollow, and a heat storage fluid flows in the hollow fine wire. 4. The heat fixing device according to claim 2, wherein a plurality of the thin wires are embedded in the same direction as the axial direction of the pressure roller. 5. The heat fixing device according to claim 3, wherein a plurality of the thin wires are buried in the same direction as the axial direction of the pressure roller, and ends of the thin wires are connected to one flow path. Wherein a heat storage fluid circulates in the thin wire forming the one flow path.