System and method for judging paper-jam conditions of an image forming apparatus

A method of judging a paper jam in an image forming apparatus, comprising the steps of:

• a) checking a pickup sensor unit;
• b) checking a feed sensor unit if it is judged that the pickup sensor unit is in an “ON” state in the step (a);
• c) operating a timer if it is judged that the feed sensor unit is switched to an “ON” state in the step (b);
• d) calculating a value T1 for a fuse lamp drive unit to be in an “ON” state;
• e) comparing the value T1 with a reference value T2;
• and
• f) judging a paper jam and aborting a printing operation if the value T1 is out of an error range of the value T2 in the comparison of the step (e).

A system for detecting a paper delivery abnormality in a device, such as an image forming apparatus, using at least one of a feed sensor unit and fuser temperature controller, the system comprising:

• a feed sensor unit, having a sensor and actuator for detecting a leading paper edge and in response switching to an “ON” state, and for detecting a rear paper edge and in response switching to an “OFF” state;
• a fuser, having at least one heating element and heating roller to fix an image on a paper surface;
• a fuser temperature controller, for maintaining a temperature at said heating roller at a substantially constant predetermined temperature by energizing said heating element;
• at least one timer, for monitoring said fuser temperature controller to measure a value T1, wherein said value T1 is a period said heating element is energized;
• and
• a controller, for detecting a paper delivery abnormality based upon said feed sensor unit state, value T1 and a reference value T2, wherein said reference value T2 is a reference period said heating element is energized during normal paper delivery.

A method for detecting a paper delivery abnormality in a device, such as an image forming apparatus, using at least one of a feed sensor unit and fuser temperature controller, the method comprising the steps of:

• detecting an input paper at a feed sensor unit and monitoring said feed sensor unit to detect a transition between an “OFF” and “ON” state to indicate normal input paper delivery based upon said transition, and detecting a paper delivery abnormality when said normal input paper delivery is not detected;
• monitoring a fuser temperature controller and measuring a value T1 wherein said value T1 is a period said fuser temperature controller energizes a heating element to fix an image on said input paper;
• and
• comparing said value T1 with a reference value T2, wherein said reference value T2 is a reference period said heating element is energized during normal paper delivery, and detecting a paper delivery abnormality when said normal input paper delivery is detected and said value T1 is greater than or less than the reference value T2.