FIXING DEVICE

Abstract

The fixing device includes a pair of rotating bodies which conveys a recording medium between a nip; a heating unit which heats at least one of the rotating bodies; and a temperature detection unit which detects a temperature of at least one of the rotating bodies. The temperature detection unit detects a temperature change until an image forming apparatus is normally operated since the heating unit starts the heating, and the temperature change is stored. It is judged that the image forming apparatus is in an abnormal state when the temperature detection unit detects a temperature change different from the temperature change in the normal operation. A temperature control unit stops passage of current through the heating unit when it is judged that the image forming apparatus is in the abnormal state.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a configuration of an image forming apparatus including a fixing device according to the invention;

FIG. 2 is a transverse sectional view showing a structure of a fixing unit constituting the fixing device according to the invention;

FIG. 3 is a longitudinal sectional view showing the structure of the fixing unit constituting the fixing device according to the invention;

FIG. 4 is a block diagram showing an electric configuration of the image forming apparatus including the fixing device according to the invention;

FIG. 5 is a view explaining a temperature curve stored in a storage unit included in the fixing device according to the invention;

FIG. 6 is a view explaining a state in which a jammed recording sheet winds around a heating roller; and

FIG. 7 is a flowchart explaining an operation of the fixing device according to the invention.

Claims

1. A fixing device comprising: a pair of rotating bodies which conveys a recording medium between a nip at which said rotating bodies are pressed against each other;a heating unit which heats at least one of said rotating bodies;a temperature detection unit which detects a temperature of at least one of said rotating bodies;a storage unit in which a temperature change is stored, said temperature detection unit detecting the temperature change until an image forming apparatus is normally operated since said heating unit starts heating;a judgment unit which judges that the image forming apparatus is in an abnormal state when said temperature detection unit detects a temperature change different from the temperature change of said normal operation; anda temperature control unit which stops passage of current through said heating unit when said judgment unit judges that the image forming apparatus is in the abnormal state.

2. A fixing device according to claim 1, further comprising a drive control unit which stops rotation of said rotating bodies when said judgment unit judges that the image forming apparatus is in the abnormal state.

3. A fixing device according to claim 1, wherein said temperature detection unit is a noncontact temperature detection unit which is placed near at least one of said pair of rotating bodies.

4. A fixing device according to claim 1, wherein said temperature detection unit is arranged in the substantial center of a region where the maximum recording sheet is conveyed between the nip of said pair of rotating bodies.

5. A fixing device according to claim 1, wherein said temperature detection unit is arranged in a sheet non-passing region except for the region where the maximum recording sheet is conveyed between the nip of said pair of rotating bodies.

6. A fixing device according to claim 1, wherein said temperature detection unit causes said temperature control unit to control said rotating bodies based on detection output of said temperature detection unit such that said rotating bodies is maintained at a predetermined temperature.

7. A fixing device according to claim 1, further comprising a display unit which displays the abnormality or provides warning when said judgment unit judges that the image forming apparatus is in the abnormal state.

8. A fixing device according to claim 1, wherein the temperature change until the image forming apparatus is normally operated is temperature rise since said heating unit starts the heating again after the rotation of said pair of rotating bodies is stopped to stop the passage of the current through the heating unit.

9. A fixing device according to claim 1, wherein the temperature rise in the case where the recording sheet winds around the rotating bodies while coming into close contact with the rotating bodies and the temperature rise in the case where the recording sheet winds around the rotating bodies while partially isolated from the rotating bodies are stored in said storage unit.

10. An image forming apparatus comprising a fixing device as in claim 1.

11. A fixing device according to claim 3, wherein said temperature detection unit is a noncontact temperature detection unit which is placed near at least one of said pair of rotating bodies.