JPH05113728A - Fixing device - Google Patents

Abstract

PURPOSE:To reduce heat radiation from flange parts so as to eliminate power loss. CONSTITUTION:In a fixing roller, its roller part 10 is formed of material high in heat conductivity such as an aluminum alloy or copper, whereas its flange part 11 is formed of metal such as iron or stainless steel different from that of the roller part 10. The roller part 10 and both end flange parts 11 are connected by pressure bonding or welding. Since both end flange parts 11 are formed of metal lower in heat conductivity than the roller part 10, heat radiation from the flange parts 11 can be suppressed in this fixing roller 1 compared to the case of using high heat conductive material for the flange parts 11.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a roller portion holding at least one heat pipe, a fixing roller provided with flange portions provided at both ends of the roller portion, and a pressure applied to the fixing roller. A transfer material carrying an unfixed toner image is nipped and conveyed by the fixing roller and the pressure roller, and at this time, the unfixed toner image is fixed on the transfer material. The present invention relates to a fixing device.

[0002]

2. Description of the Related Art Fixing devices of the above type are well known and are used in copying machines, printers, facsimiles and the like. In this type of fixing device, a heater as a heating means is provided inside the fixing roller, and the heater is controlled so that the surface temperature of the fixing roller is maintained at a predetermined set temperature.

In such a fixing device, it is desirable that the surface temperature of the fixing roller is uniform in the axial direction. However, when a small-sized transfer material is continuously fed, the surface temperature of the fixing roller becomes non-uniform because a temperature rise phenomenon occurs in the non-sheet passing portion and a temperature difference occurs between the sheet passing portion. And
When the surface temperature of the fixing roller is non-uniform, when a large-sized transfer material is passed through, a problem such as an offset may occur on the image surface corresponding to the non-sheet passing portion.

Further, the pressure roller is usually covered with an elastic layer such as silicone rubber, and the elastic layer expands due to a temperature rise in the non-sheet passing portion, resulting in a non-uniform nip width with the fixing roller. There was also a problem that it could cause paper wrinkles.

Therefore, Japanese Utility Model Laid-Open No. 58-38165 discloses that a heat pipe is embedded in the fixing roller so that the surface temperature of the fixing roller is uniform in the axial direction.

[0006]

In the fixing device constructed as described above, the surface temperature of the fixing roller is substantially uniform in the axial direction due to the heat transporting action of the heat pipe even if the temperature rise phenomenon occurs in the non-sheet passing portion. The temperature becomes high, and problems such as offset are solved.

However, the fixing roller has a problem that power is lost because heat is transferred to the flange portion of the fixing roller by the heat pipe and is also radiated from the flange portion. Further, although the partial expansion of the elastic layer of the pressure roller is alleviated, it is difficult to instantly eliminate the partial expansion. Further, the fixing roller is replaced at the end of its life if the release layer coated on the surface of the fixing roller is worn, but there is a problem that it is uneconomical because the heat pipe can be used sufficiently. It is an object of the present invention to provide a fixing device that solves the above-mentioned conventional problems.

[0008]

The structure of the present invention for achieving the above object is as follows. (1) A roller portion holding at least one heat pipe, a fixing roller having flange portions provided at both ends of the roller portion, a pressure roller pressed against the fixing roller, and heating the fixing roller. In the fixing device, which has a heating unit for carrying out, by the fixing roller and the pressure roller, the transfer material carrying the unfixed toner image is nipped and conveyed, and at that time, the unfixed toner image is fixed to the transfer material, The fixing roller has a roller portion and a flange portion made of different metals,
Further, the fixing device is characterized in that the roller portion and the flange portion are joined by pressure contact or welding.

(2) The fixing device according to the above (1), wherein the roller portion of the fixing roller is made of a metal having a high thermal conductivity and the flange portion is made of a metal having a low thermal conductivity.

(3) The fixing device as described in (1) or (2) above, wherein the surface of the flange portion is covered with a heat insulating member made of a resin having a high heat insulating property.

(4) A fixing roller having a roller portion holding at least one heat pipe, flange portions provided at both ends of the roller portion, a pressure roller pressed against the fixing roller, and the fixing portion. A fixing unit that has a heating unit that heats the roller, and the transfer material carrying the unfixed toner image is nipped and conveyed by the fixing roller and the pressure roller, at which time the unfixed toner image is fixed to the transfer material. In the device,
At least one heat pipe is provided in the pressure roller, and both ends of the pressure roller are covered with a heat insulating member.

(5) A fixing roller having a roller portion holding at least one heat pipe, flange portions provided at both ends of the roller portion, a pressure roller pressed against the fixing roller, and the fixing member. A fixing unit that has a heating unit that heats the roller, and the transfer material carrying the unfixed toner image is nipped and conveyed by the fixing roller and the pressure roller, at which time the unfixed toner image is fixed to the transfer material. In the device,
A fixing device, wherein a roller portion of the fixing roller is divided into a surface roll member and a core metal member holding the heat pipe, and the core metal member is detachably fitted to the surface roll member.

(6) The surface roll member is made of a material having a small coefficient of thermal expansion conductivity, and the core metal member is made of a material having a large coefficient of thermal expansion conductivity. The fixing device according to the above (5), wherein the cored bar member is fitted to the surface roll member with a gap from the outer diameter.

[0014]

According to the above construction (1), since the roller portion and the flange portion of the fixing roller are made of different metals, only the roller portion can be made of a metal having excellent thermal conductivity. The uniformity of the surface temperature in the axial direction can be improved.

According to the above configuration (2), heat dissipation at the flange portion of the fixing roller can be suppressed and power loss can be reduced.

According to the above configuration (3), heat dissipation at the flange portion of the fixing roller is further suppressed by the heat insulating member, and power loss can be further reduced.

According to the structure of (4), since at least one heat pipe is provided in the pressure roller and both end portions of the pressure roller are covered with the heat insulating member, the pressure roller surface. Partial thermal expansion of the layer can be eliminated and paper wrinkles can be prevented.

According to the above constitution (5), the roller portion of the fixing roller is divided into the surface roll member and the core metal member holding the heat pipe, and the core metal member is detachably fitted to the surface roll member. Therefore, even if the surface of the roller portion is worn, only the surface roll member can be replaced.

According to the above configuration (6), the surface roll member is made of a material having a small coefficient of thermal expansion conductivity, and the core metal member is made of a material having a large coefficient of thermal expansion coefficient. Since the core metal member is fitted to the surface roll member with a gap between the core metal member and the outer diameter of the core metal member, the replacement work of the surface roll member can be simplified.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a sectional explanatory view showing a fixing roller of a fixing device according to the present invention. In FIG. 1, reference numeral 1 is a fixing roller, 2 is a pressure roller pressed against the fixing roller 1, and a heater 3 as a heating means is provided inside the fixing roller 1.
Are arranged. The fixing roller 1 is composed of a roller portion 10 into which a heat pipe 4 is inserted and flange portions 11 at both ends.

As shown in FIG. 2 or FIG. 3, four heat pipes 4 are inserted in the roller portion 10 of the fixing roller 1 so that the roller portion 10 has a heat pipe even if the temperature rise phenomenon occurs. Thermal uniformity is obtained by the heat transport action of No. 4. Further, on the inner surface side of the roller portion 10, heat-resistant black coating (for example, OKI) is provided in order to improve heat absorption from the heater 3.
Made by TSUMO, # 8000). On the other hand, the flange portion 11 is supported by the side plate 8 via the heat insulating bush 6 and the bearing 7, and the gear portion 5 for transmitting the drive to the fixing roller 1 is attached to the one flange portion 11.

According to the present invention, the roller portion 10 of the fixing roller 1 is made of a material having high heat conductivity, such as aluminum alloy or copper, whereas the flange portion 11 is more heat conductive than the roller portion 10. It is made of a metal having a low property, which is different from that of the roller portion 10, such as iron or stainless steel. The roller portion 10 and the flange portions 11 on both ends are joined by pressure welding or welding.

In the thus constructed fixing device, as shown by the curve A in FIG. 4, since the flange portions 11 at both ends are made of a metal having lower thermal conductivity than the roller portion 10, the flange portion 11 indicated by the curve B is formed. In comparison with the case of using a high thermal conductive material, the fixing roller 1 can suppress the heat radiation from the flange portion 11.

Thus, in the fixing device, the heat radiation from the flange portion 11 of the fixing roller 1 is suppressed, so that the loss of electric power can be reduced and the heat uniformity in the roller portion 10 can be improved.

FIG. 5 is a cross-sectional explanatory view showing another embodiment of the present invention, in which the flange portion 11 is made of a metal having a low heat conductivity and is made of a resin having a high heat resistance, such as a polyimide resin. It is covered with a heat insulating member 13. With this configuration, the fixing roller 1 can be provided with a heat insulating effect, the heat radiation from the flange portion 11 can be further suppressed, and the power loss can be significantly reduced. Further, it becomes possible to further improve the heat uniformity of the roller portion 10.

By the way, the fixing roller 1 is treated with Teflon coating, silicone rubber coating or the like on the surface of the roller portion 10. In both cases, the releasability is enhanced so that toner (not shown) does not adhere to the surface of the fixing roller during fixing. However, if the release layer becomes worn, the fixing roller 1 needs to be replaced. However, at this time, since the heat pipe 4 can be sufficiently used, it is uneconomical to replace the heat pipe 4 as a whole, as described above.

Therefore, the present invention is configured as follows in order to solve such a problem.

In FIGS. 6 and 7, the roller portion 10 of the fixing roller 1 is divided into a core metal member 10a and a surface roll member 12, and the core metal member 10a is detachably fitted to the surface roll member 12. .. The core metal member 10a is made of a material having high thermal conductivity, such as aluminum alloy or copper. On the other hand, the surface roll member 12 is made of a material having a coefficient of thermal expansion lower than that of the cored bar, such as iron or nickel. That is, K ₁ is the coefficient of thermal expansion of the core metal member 10a, and K _{2 is}
Is the coefficient of thermal expansion of the surface roll member 12, the relationship K ₁ > K ₂ is established. 8 is a modification of FIG. 7 of the core metal member 10a of the fixing roller of this example.

Normally, when the fixing roller 1 is replaced, it is carried out in a state where the roller is cooled at about room temperature. In this cold state, the inner diameter of the surface roll member 12 is made larger than the outer diameter of the cored bar member 10a beforehand. It is set. Further, at the time of fixing, the fixing roller 1 is warmed by heating from the heater 3, and due to the difference in the thermal expansion coefficient described above, the surface roll member 12
Is set in advance so that the core metal member 10a is thermally expanded so that the core metal member 10a is in a shrink fit state.

In the thus constructed fixing device, as shown in FIG. 9, the inner diameter D ₂ of the surface roll member 12 is larger than the outer diameter D ₁ of the cored bar member 10a in the cold state T ₁ . However, at fixing time T ₂ , the outer diameter of the core metal member 10a expands from D ₁ to D ₄ , and the inner diameter of the surface roll member 12 expands from D ₂ to D ₃ , but the outer diameter D _{4 of the} core metal member 10a. Is larger than the inner diameter D ₃ of the surface roll member 12. Therefore, in the cold state T ₁ when the fixing roller is replaced, the state of D ₂ > D ₁ is satisfied, so that the surface roll member 12 can be easily detached by sliding the core metal member 10a. In addition, since D ₄ > D ₃ at the time of fixing, there is no problem that the surface roll member 12 comes off from the core metal member 10 a, and the rotational drive to the fixing roller 1 can be reliably transmitted. Is becoming

FIG. 10 shows a modification of the embodiment shown in FIG. 6, in which the protrusion 14 on the inner diameter side of the surface roll member 12 and the recess 15 on the outer diameter side of the cored bar member 10a are fitted together. .. By providing such a rotation stopper, the fixing roller 1
It is possible to more reliably transmit the rotational drive to the. Of course, during fixing, the roller is heated and is in a shrinking state, and the surface roll member 12 and the core metal member 10a are
It has the effect of increasing the thermal conductivity in the boundary portion between and.

By the way, the surface temperature of the fixing roller 1 is as shown in FIG.
When the transfer material P of the small size L1 shown in 1 is continuously fed, the temperature of the fixing roller 1 is controlled to a constant temperature in the paper passing portion, so that the heater continues to light up by the amount of heat taken by the paper passing. However, if the heater 3 continues to be turned on in the non-sheet passing portion of the maximum size L2, the temperature becomes higher than that in the small sheet passing portion of the size L1, and as a result, only the non-sheet passing portion of the pressure roller 2 is heated. Will be done. As a result, the elastic body 2a of the pressure roller 2 thermally expands and the roller diameter corresponding to the non-sheet passing portion expands (line B in the graph of FIG. 11). At this time,
If the difference in diameter due to the expansion of the pressure roller 2 is large, the nip width is widened at both ends, and excessive stress is applied in the axial direction of the paper at the time of paper passage, which causes paper wrinkles.

Therefore, the present invention is configured as follows in order to solve such a problem.

12 and 13, the pressure roller 2
The core bar 21 is made of a metal such as an aluminum alloy that has excellent extrudability and high thermal conductivity. A heat pipe 24 is embedded in the core metal 21, and an elastic layer 22 of silicone rubber is coated on the surface. The pressure roller 2 equipped with the heat pipe 24 has an effect that the surface temperature tends to be uniform in the axial direction even if it receives heat from the fixing roller 1. In addition,
In this example, the fixing roller 1 is not provided with a heat pipe.

Thus, in the pressure roller 2 having the heat pipe 24, the surface of the pressure roller 2 is made uniform by the heat transport function of the heat pipe 4, so that the diameter of the pressure roller 2 is as shown in the graph of FIG. As indicated by the line A, the difference between the diameter of the paper passing surface and the diameter of the non-paper passing surface becomes small. This can prevent paper wrinkles and the like.

FIG. 14 shows a modification of the embodiment shown in FIG. 12, in which the pressure roller 2 having the heat pipe 24 has a straight cored bar 21 and a journaled part 25.
The heat pipe 24 is divided into
It is embedded in and is composed of materials such as aluminum alloy. On the other hand, the journal portion 25 is made of a material having a high heat insulating property, for example, a material having excellent heat resistance such as a polyimide resin. By insulating the both ends in this way, it is possible to block the heat radiation to the side plate (not shown) (broken line arrow in the figure), prevent the temperature rise inside the machine, and heat pipe 24.
Thus, the surface temperature of the pressure roller 2 can be effectively equalized.

FIG. 15 shows an embodiment in which the heat pipes 4 and 24 are mounted on both the fixing roller 1 and the pressure roller 2. By mounting the heat pipe 4 on the fixing roller 1, the temperature in the axial direction is made uniform, and the temperature rise at the roller end portion after continuous small-size sheet passing is prevented to prevent offset. Further, by mounting the heat pipe 24 also on the pressure roller 2, it is possible to prevent unevenness in diameter due to expansion and prevent wrinkles from occurring.

[0038]

According to the first aspect, the uniformity of the surface temperature of the fixing roller in the axial direction can be enhanced.

According to the second aspect of the invention, the heat radiation at the flange portion of the fixing roller can be suppressed, so that the power loss can be reduced.

According to the third aspect, the heat radiation at the flange portion of the fixing roller can be further suppressed by the heat insulating member.
Power loss can be reduced significantly.

According to the fourth aspect, the partial thermal expansion of the surface layer of the pressure roller can be eliminated, so that the occurrence of paper wrinkles of the transfer material can be prevented.

According to the fifth aspect, even if the surface of the roller portion is worn, only the surface roll member can be replaced, so that the heat pipe can be reused and the cost is reduced.

According to the sixth aspect, the work of exchanging the surface roll member can be simplified.

[Brief description of drawings]

FIG. 1 is a cross-sectional explanatory view of a fixing roller of a fixing device according to the present invention.

FIG. 2 is a cross-sectional explanatory view of a roller portion of FIG.

FIG. 3 is a cross-sectional explanatory view showing a modified example of the roller portion of FIG.

FIG. 4 is a graph showing the heat radiation amounts of the present invention and the prior art and the flange portion in the axial direction of the fixing roller.

5 is a cross-sectional explanatory view of a part of a fixing roller showing a modified example of FIG.

FIG. 6 is a cross sectional view showing still another embodiment of the present invention.

7 is a cross-sectional explanatory view of the roller portion of FIG.

8 is a cross-sectional explanatory view showing a modified example of the roller portion of FIG.

FIG. 9 is a graph showing a difference in diameter between a core metal member and a surface roll member during cold and fixing.

FIG. 10 is a perspective view of a part of a fixing roller showing a modified example of FIG.

FIG. 11 is a graph showing a difference in diameter due to expansion between the present invention and the conventional case when the temperature rise phenomenon occurs in the axial direction of the pressure roller.

FIG. 12 is a cross sectional view showing still another embodiment of the present invention.

13 is a cross-sectional explanatory view of the pressure roller of FIG.

FIG. 14 is a cross-sectional explanatory view showing a modified example of FIG.

15 is a cross-sectional explanatory view showing another modified example of FIG.

[Explanation of symbols]

 1 Fixing Roller 2 Pressure Roller 3 Heater 4,24 Heat Pipe 10 Roller Part 10a Core Bar Member 11 Flange Part 12 Surface Roll Member 25 Heat Insulation Member

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yutaka Fukuchi 1-3-3 Nakamagome, Ota-ku, Tokyo Stock company Ricoh Company (72) Inventor Atsushi Arai 1-3-6 Nakamagome, Ota-ku, Tokyo Stocks Inside Ricoh Company (72) Inventor Masahiko Sato 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd.

Claims (6)

[Claims] 1. A fixing roller having a roller portion holding at least one heat pipe, flange portions provided at both ends of the roller portion, a pressure roller pressed against the fixing roller, and the fixing roller. And a heating unit that heats the transfer material holding the unfixed toner image between the fixing roller and the pressure roller, and fixes the unfixed toner image on the transfer material. In the fixing device, the roller portion and the flange portion are made of different kinds of metal, and the roller portion and the flange portion are joined by pressure contact or welding. 2. The fixing device according to claim 1, wherein the roller portion of the fixing roller is made of a metal having a high thermal conductivity and the flange portion is made of a metal having a low thermal conductivity. 3. The fixing device according to claim 1, wherein the surface of the flange portion is covered with a heat insulating member made of a resin having a high heat insulating property. 4. A fixing roller having a roller portion holding at least one heat pipe, flange portions provided at both ends of the roller portion, a pressure roller pressed against the fixing roller, and the fixing roller. And a heating unit that heats the transfer material holding the unfixed toner image between the fixing roller and the pressure roller, and fixes the unfixed toner image on the transfer material. In the fixing device, at least one heat pipe is also provided in the pressure roller, and both ends of the pressure roller are covered with a heat insulating member. 5. A fixing roller having a roller portion holding at least one heat pipe, flange portions provided at both ends of the roller portion, a pressure roller pressed against the fixing roller, and the fixing roller. And a heating unit that heats the transfer material holding the unfixed toner image between the fixing roller and the pressure roller, and fixes the unfixed toner image on the transfer material. In the fixing device, the roller portion of the fixing roller is divided into a surface roll member and a core metal member holding the heat pipe, and the core metal member is detachably fitted to the surface roll member. 6. The surface roll member is made of a material having a low coefficient of thermal expansion coefficient conductivity, and the core metal member is made of a material having a high coefficient of thermal expansion coefficient conductivity. The fixing device according to claim 5, wherein the core metal member is fitted to the surface roll member with a gap between the core metal member and the diameter.