FIXING APPARATUS AND IMAGE FORMING APPARATUS

Abstract

A fixing apparatus includes: a fixing roller and a pressure roller which transport a recording paper while sandwiching the recording paper P therebetween so that an unfixed toner image formed on the recording paper is fixed thereon under heat and pressure; two support rollers; an endless belt which is set over the support rollers and comes into contact with a surface of the fixing roller; and heater lamps which are provided respectively inside the support rollers. A fixing apparatus satisfies a relationship indicated by (C2+C3)/C1≧2 where C1 is a heat capacity of each of the heater lamps, C2 is a heat capacity of each of the support rollers, and C3 is a heat capacity of the endless belt in each of areas where the endless belt is in contact with the support rollers. This realizes an external belt heat fixing apparatus which suppresses (a) heat damage to the endless belt and the surface of the fixing member and (b) unevenness of an image.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view schematically illustrating a structure of a fixing apparatus according to an embodiment of the present invention.

FIG. 2 is a view schematically illustrating an internal structure of an image forming apparatus which includes a fixing apparatus illustrated in FIG. 1.

FIG. 3 is a sectional view illustrating a structure of an external heating device which is provided in the fixing apparatus illustrated in FIG. 1.

FIG. 4 is a top view of the external heating device which is provided in the fixing apparatus illustrated in FIG. 1.

FIG. 5 is a diagram schematically illustrating a structure of a modified fixing apparatus according to an embodiment of the present invention.

FIG. 6 is a graph showing a relationship between heat capacity ratio in the external heating apparatus and a temperature of an endless belt.

FIG. 7 is a diagram schematically illustrating a structure of another modified fixing apparatus according to an embodiment of the present invention.

Claims

1. A fixing apparatus comprising: a fixing member which transports a recording material while sandwiching the recording material so that an unfixed toner image formed on the recording material is fixed on the recording material under heat and pressure;a plurality of support rollers;an endless belt which is set over the support rollers and comes into contact with a surface of the fixing member; andheating means which are provided respectively inside the support rollers, whereina relationship indicated by the following equation (1) is satisfied: (C2+C3)/C1≧2  (1)where C1 is a heat capacity of the heating means, C2 is a heat capacity of each of the support rollers, and C3 is a heat capacity of the endless belt in each of areas where the endless belt is in contact with the support rollers.

2. A fixing apparatus comprising: a fixing member which transports a recording material while sandwiching the recording material so that an unfixed toner image formed on the recording material is fixed on the recording material under heat and pressure;a plurality of support rollers;an endless belt which is set over the support rollers and comes into contact with a surface of the fixing member; andheating means which are provided respectively inside the support rollers, whereina relationship indicated by the following equation (2) is satisfied: t/λ≦0.001 m2K/W  (2)where t is a thickness of the endless belt, and λ is a thermal conductivity of the endless belt.

3. A fixing apparatus comprising: a fixing member which transports a recording material while sandwiching the recording material so that an unfixed toner image formed on the recording material is fixed on the recording material under heat and pressure;a plurality of support rollers;an endless belt which is set over the support rollers and comes into contact with a surface of the fixing member; andheating means which are provided respectively inside the support rollers, whereina ratio of a length of the endless belt in a moving direction of the endless belt in an area of the endless belt that is in contact with the surface of the fixing member is not less than 0.1 relative to a peripheral length of the fixing member.

4. The fixing apparatus according to claim 1, wherein a lower temperature of (a) a glass transition temperature and (b) a melting temperature of the endless belt is not less than 250° C.

5. The fixing apparatus according to claim 2, wherein a lower temperature of (a) a glass transition temperature and (b) a melting temperature of the endless belt is not less than 250° C.

6. The fixing apparatus according to claim 3, wherein a lower temperature of (a) a glass transition temperature and (b) a melting temperature of the endless belt is not less than 250° C.

7. The fixing apparatus according to claim 1, wherein the heating means are halogen lamps each of which is filled with a gas having a thermal conductivity of not more than 110×10−4 W/m·K.

8. The fixing apparatus according to claim 2, wherein the heating means are halogen lamps each of which is filled with a gas having a thermal conductivity of not more than 110×10−4 W/m·K.

9. The fixing apparatus according to claim 3, wherein the heating means are halogen lamps each of which is filled with a gas having a thermal conductivity of not more than 110×10−4 W/m·K.

10. The fixing apparatus according to claim 1, wherein the fixing member comprises a fixing roller and a pressure roller both of which sandwich the recording material therebetween,the fixing roller comes into contact with the unfixed toner image formed on the recording material, andthe endless belt comes into contact with a surface of the fixing roller.

11. The fixing apparatus according to claim 2, wherein the fixing member comprises a fixing roller and a pressure roller both of which sandwich the recording material therebetween,the fixing roller comes into contact with the unfixed toner image formed on the recording material, andthe endless belt comes into contact with a surface of the fixing roller.

12. The fixing apparatus according to claim 3, wherein the fixing member comprises a fixing roller and a pressure roller both of which sandwich the recording material therebetween,the fixing roller comes into contact with the unfixed toner image formed on the recording material, andthe endless belt comes into contact with a surface of the fixing roller.

13. A fixing apparatus comprising: a fixing roller and a pressure roller which transport a recording material while sandwiching the recording material therebetween;a plurality of support rollers;an endless belt which is set over the support rollers and comes into contact with a surface of the fixing roller; andheating means which are provided respectively inside the support rollers,the fixing roller fixing an unfixed toner image formed on the recording material thereon under heat and pressure,the fixing apparatus further comprising:a heat roller which is in contact with a surface of the pressure roller and heats the pressure roller from outside the pressure roller.

14. An image forming apparatus comprising: a fixing apparatus which includes a fixing member which transports a recording material while sandwiching the recording material so that an unfixed toner image formed on the recording material is fixed on the recording material under heat and pressure, a plurality of support rollers, an endless belt which is set over the support rollers and comes into contact with a surface of the fixing member, and heating means which are provided respectively inside the support rollers; and toner image forming means for forming a toner image on the recording material, wherein a relationship indicated by the following equation (1) is satisfied: (C2+C3)/C1≧2  (1)where C1 is a heat capacity of the heating means, C2 is a heat capacity of each of the support rollers, and C3 is a heat capacity of the endless belt in each of areas where the endless belt is in contact with the support rollers.

15. An image forming apparatus comprising: a fixing apparatus which includes a fixing member which transports a recording material while sandwiching the recording material so that an unfixed toner image formed on the recording material is fixed on the recording material under heat and pressure, a plurality of support rollers, an endless belt which is set over the support rollers and comes into contact with a surface of the fixing member, and heating means which are provided respectively inside the support rollers; and toner image forming means for forming a toner image on the recording material, wherein a relationship indicated by the following equation (2) is satisfied: t/λ≦0.001 m2K/W  (2)where t is a thickness of the endless belt, and λ is a thermal conductivity of the endless belt.

16. An image forming apparatus comprising: a fixing apparatus which includes a fixing member which transports a recording material while sandwiching the recording material so that an unfixed toner image formed on the recording material is fixed on the recording material under heat and pressure, a plurality of support rollers, an endless belt which is set over the support rollers and comes into contact with a surface of the fixing member, and heating means which are provided respectively inside the support rollers; and toner image forming means for forming a toner image on the recording material, wherein a ratio of a length of the endless belt in a moving direction of the endless belt in an area of the endless belt that is in contact with the surface of the fixing member is not less than 0.1 relative to a peripheral length of the fixing member.

17. An image forming apparatus comprising: a fixing apparatus which includes a fixing roller and a pressure roller which transport a recording material while sandwiching the recording material therebetween, a plurality of support rollers, an endless belt which is set over the support rollers and comes into contact with a surface of the fixing roller, and heating means which are provided respectively inside the support rollers, the fixing roller fixing an unfixed toner image formed on the recording material thereon under heat and pressure; and toner image forming means for forming a toner image on the recording material, the image forming apparatus further including:a heat roller which is in contact with a surface of the pressure roller and heats the pressure roller from outside the pressure roller.