FIXING APPARATUS, IMAGE FORMING APPARATUS, METHOD FOR CONTROLLING FIXING APPARATUS, PROGRAM FOR CONTROLLING FIXING APPARATUS, AND RECORDING MEDIUM STORING SAME PROGRAM

Abstract

For start of rotation of a fixing roller that is not currently being rotated, a control device causes a halogen lamp to heat an endless belt until a thermistor detects that a surface temperature of the endless belt has reached a first target temperature set at a temperature at which the endless belt is softened and is restored to its normal shape, from a deformed shape that the endless belt had while it was not rotated, to such an extent that the endless belt will never cause any rotation trouble during the rotation. This prevents the rotation trouble of the belt in a fixing apparatus in which a fixing member is heated by bringing the thus heated belt into contact with the fixing member.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

FIG. 2 is a diagram schematically illustrating an internal structure of an image forming apparatus including the fixing apparatus shown in FIG. 1.

FIG. 3 is a flowchart illustrating a flow of processes carried out upon warm-up of the fixing apparatus according to the embodiment of the present invention.

FIG. 4 is a graph illustrating respective how respective surface temperatures of an endless belt, a fixing roller, and a pressure roller each provided in the fixing apparatus according to the embodiment of the present invention change upon the warm-up.

FIG. 5 is an explanatory diagram illustrating a circumferential length L4 of the endless belt, which circumferential length L4 is minimally required for setting the endless belt around supporting rollers in the fixing apparatus according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating an example of a structure, which the fixing apparatus according to the embodiment of the present invention has and in which non-contact type temperature detecting means is used to detect the surface temperature of the endless belt.

FIG. 7 is an explanatory diagram illustrating protrusion existing in the endless belt when rotation of the endless belt is started before the endless belt is restored to its normal shape from a deformed shape that the endless belt had while it was not rotated.

FIG. 8 is a graph focusing on the temperature changes (see the graph of FIG. 4) occurring around the start of the rotation operation.

FIG. 9 is a graph illustrating how the surface temperatures of the endless belt and the fixing roller are changed when a rotation trouble of the endless belt occurs.

FIG. 10 is a flowchart illustrating processes carried out in cases where control is carried out so as to stop heating of the external heating device when the rotation trouble is detected in the fixing apparatus according to the embodiment of the present invention.

FIG. 11 is a graph illustrating how the temperature of the endless belt is changed when the control of FIG. 10 is carried out in response to the detection of the rotation trouble.

Each of FIG. 12(a) and FIG. 12(b) is an explanatory diagram illustrating an example of a structure, which the fixing apparatus according to the embodiment of the present invention has and in which a releasing/contacting mechanism for separating the external heating device from the fixing roller and bringing the eternal heating device into contact with the fixing roller.

Claims

1. A fixing apparatus, comprising a fixing member; a pressure member; an external heating device, in which a belt set around a plurality of supporting rollers in contact with a peripheral surface of the fixing member is heated by a first heating section so as to heat the fixing member and the belt is rotated according to rotation of the fixing member; the fixing member and the pressure member sandwiching and transporting a recording material, so that an unfixed image formed on the recording material is fixed onto the recording material by heating from the fixing member, said fixing apparatus, further comprising:a first temperature detecting section for detecting a surface temperature of the belt;a rotation driving section for driving to rotate the fixing member; anda control section for causing the first heating section to heat the belt for start of rotation of the fixing member, and causing the rotation driving section to rotate the fixing member when the belt reaches a first target temperature at which the belt is softened.

2. The fixing apparatus as set forth in claim 1, wherein: the control section sets the first target temperature at a temperature at which the belt is softened and restores flexibility so as not to cause any rotation trouble while the belt is rotated.

3. The fixing apparatus as set forth in claim 1, further comprising: a non-contact type second temperature detecting section, provided out of contact with the belt but facing to the belt at a region where the belt is not contact with the supporting rollers,wherein:the control section sets the first target temperature at a temperature at which the belt is softened and restores flexibility such that the belt does not meet the second temperature detecting section while the belt is rotated.

4. The fixing apparatus as set forth in claim 1, wherein: the control section sets the first target temperature at which toner is melted.

5. The fixing apparatus as set forth in claim 1, further comprising: a releasing and contacting mechanism for separating the belt from the fixing member,wherein:the control section causes the releasing and contacting mechanism to bring the belt into contact with the fixing member, before the start of the rotation of the fixing member.

6. The fixing apparatus as set forth in claim 1, wherein: 0.1 mm≦L5−L4≦2 mm is satisfied, where L4 represents a minimal internal circumferential length that the belt requires in theory so as to be set around the supporting rollers, and L5 represents an internal circumferential length that the belt actually has when the belt is set around the supporting rollers.

7. The fixing apparatus as set forth in claim 1, further comprising a second heating section for heating the fixing member, the first and second heating sections heating according to electric power supplied from a electric power supplying section, wherein:the control section controls the supply of electric power from the electric power supplying section to the first and second heating sections such that the surface temperature of the belt reaches a second target temperature, which is a warm-up completion temperature of the belt, and then a surface temperature of the fixing member reaches a third target temperature, which is a warm-up completion temperature of the fixing member.

8. The fixing apparatus as set forth in claim 7, wherein: the control section causes the electric power supplying section to supply electric power to the first heating section but not to supply electric power to the second heating section, until the surface temperature of the belt reaches the second target temperature, andafter the surface temperature of the belt has reached the second target temperature, the control section causes the electric power supplying section to supply electric power to the first and second heating sections.

9. The fixing apparatus as set forth in claim 1, further comprising (i) a second heating section for heating the fixing member, and (ii) a third heating section for heating the pressure member, the first to third heating sections heating according to electric power supplied from an electric power supplying section, wherein:the control section controls the supply of electric power to the first to third heating sections such that the surface temperature of the belt reaches a second target temperature, which is a warm-up completion temperature of the belt, then a surface temperature of the fixing member reaches the a third target temperature, which is a warm-up completion temperature of the fixing member, and then a surface temperature of the pressure member reaches a fourth target temperature, which is a warm-up completion temperature of the pressure member.

10. The fixing apparatus as set forth in claim 9, wherein: the control section causes the electric power supplying section to supply electric power to the first heating section but not to supply electric power to the second and third heating sections, until the surface temperature of the belt reaches the second target temperature,after the surface temperature of the belt has reached the second target temperature, the control section causes the electric power supplying section to supply electric power to the first and second heating sections but not to supply electric power to the third heating section, until the surface temperature of the fixing member reaches the third target temperature, andafter the surface temperature of the fixing member has reached the third target temperature, the control section causes the electric power supplying section to supply electric power to the first to third heating sections.

11. The fixing apparatus as set forth in claim 1, wherein: the control section causes the first heating section to stop heating the belt, in cases where the temperature detected by the first temperature detecting section does not decrease within a predetermined time from the start of the rotation of the fixing member.

12. An image forming apparatus, comprising: a fixing apparatus, including a fixing member; a pressure member; an external heating device, in which a belt set around a plurality of supporting rollers in contact with a peripheral surface of the fixing member is heated by a first heating section so as to heat the fixing member and the belt is rotated according to rotation of the fixing member; the fixing member and the pressure member sandwiching and transporting a recording material, so that an unfixed image formed on the recording material is fixed onto the recording material by heating from the fixing member, said fixing apparatus, further including:a first temperature detecting section for detecting a surface temperature of the belt;a rotation driving section for driving to rotate the fixing member; anda control section for causing the first heating section to heat the belt for start of rotation of the fixing member, and causing the rotation driving section to rotate the fixing member when the belt reaches a first target temperature at which the belt is softened.

13. A method for controlling a fixing apparatus, including a fixing member; a pressure member; an external heating device, in which a belt set around a plurality of supporting rollers in contact with a peripheral surface of the fixing member is heated by a first heating section so as to heat the fixing member and the belt is rotated according to rotation of the fixing member; the fixing member and the pressure member sandwiching and transporting a recording material, so that an unfixed image formed on the recording material is fixed onto the recording material by heating from the fixing member, said method, comprising:a heating step of heating the belt by the first heating section;a temperature detecting step of detecting a surface temperature of the belt; anda rotation starting step of starting rotation of the fixing apparatus when the temperature detected in the temperature detecting step reaches a first target temperature at which the belt is softened.

14. A control program for causing a computer to function as a control section of a fixing apparatus, including a fixing member; a pressure member; an external heating device, in which a belt set around a plurality of supporting rollers in contact with a peripheral surface of the fixing member is heated by a first heating section so as to heat the fixing member and the belt is rotated according to rotation of the fixing member; the fixing member and the pressure member sandwiching and transporting a recording material, so that an unfixed image formed on the recording material is fixed onto the recording material by heating from the fixing member, said fixing apparatus, further including:a first temperature detecting section for detecting a surface temperature of the belt;a rotation driving section for driving to rotate the fixing member; andthe control section for causing the first heating section to heat the belt for start of rotation of the fixing member, and causing the rotation driving section to rotate the fixing member when the belt reaches a first target temperature at which the belt is softened.

15. A computer-readable recording medium storing a control program for causing a computer to function as a control section of a fixing apparatus, including a fixing member; a pressure member; an external heating device, in which a belt set around a plurality of supporting rollers in contact with a peripheral surface of the fixing member is heated by a first heating section so as to heat the fixing member and the belt is rotated according to rotation of the fixing member; the fixing member and the pressure member sandwiching and transporting a recording material, so that an unfixed image formed on the recording material is fixed onto the recording material by heating from the fixing member, said fixing apparatus, further including:a first temperature detecting section for detecting a surface temperature of the belt;a rotation driving section for driving to rotate the fixing member; andthe control section for causing the first heating section to heat the belt for start of rotation of the fixing member, and causing the rotation driving section to rotate the fixing member when the belt reaches a first target temperature at which the belt is softened.