Image heating apparatus and heater for use therein

A heater for use in an image heating apparatus, comprising:

• a substrate;
• a heat generating resistor formed on said substrate;
• and
• first and second electrodes for supplying an electric power to said heat generating resistor;
• wherein each of said first and second electrodes has a first area to be contacted with a power supplying connector and a second area provided at an end portion electrically opposite to the first area, the second areas are provided along a longitudinal direction of said substrate, and said heat generating resistor is so provided as to electrically connect the second area of said first electrode and the second area of said second electrode;
• wherein, within the second area of said first electrode, a portion electrically closest to the first area of said first electrode is provided in the vicinity of an end portion of said substrate in the longitudinal direction thereof, and within the second area of said second electrode, a portion electrically closest to the first area of said second electrode is provided in the vicinity of the other end portion of said substrate in the longitudinal direction thereof;
• and
• wherein, when the heater is at a set temperature for an image heating operation in said image heating apparatus, a resistance value Rc of the second area of either of said first and second electrodes and a resistance value Rt between a portion within the second area of said first electrode electrically closest to the first area of said first electrode and a portion within the second area of said second electrode electrically closest to the first area of said second electrode satisfy a relation:
• Rc/Rt≦1/30.

An image heating apparatus for heating an image formed on a recording material, comprising:

• a heater, said heater including a substrate, a heat generating resistor formed on said substrate and first and second electrodes for supplying an electric power to said heat generating resistor;
• a back-up member for forming a nip portion in cooperation with said heater;
• control means which controls the electric power supply to said heat generating resistor in such a manner that a temperature of said heater is maintained at a set temperature during an image heating operation;
• wherein the recording material passes through the nip portion;
• wherein each of said first and second electrodes has a first area to be contacted with a power supplying connector and a second area provided at an end portion electrically opposite to the first area, the second areas are provided along a longitudinal direction of said substrate and said heat generating resistor is so provided as to electrically connect the second area of said first electrode and the second area of said second electrode;
• wherein, within the second areas of said first and second electrodes, portions electrically closest to the first areas are provided in the vicinity of an end portion of said substrate in the longitudinal direction thereof;
• and
• wherein, when the heater is at the set temperature, a resistance value Rc of the second area of either of said first and second electrodes and a resistance value Rt between a portion within the second area of said first electrode electrically closest to the first area of said first electrode and a portion within the second area of said second electrode electrically closest to the first area of said second electrode satisfy a relation:
• Rc/Rt≦1/60.

A heater for use in an image heating apparatus, comprising:

• a substrate;
• a heat generating resistor formed on said substrate;
• and
• first and second electrodes for supplying an electric power to said heat generating resistor;
• wherein each of said first and second electrodes has a first area to be contacted with a power supplying connector and a second area provided at an end portion electrically opposite to the first area, the second areas are provided along a longitudinal direction of said substrate and said heat generating resistor is so provided as to electrically connect the second area of said first electrode and the second area of said second electrode;
• wherein, within the second areas of said first and second electrodes, portions electrically closest to the first areas are provided in the vicinity of an end portion of said substrate in the longitudinal direction thereof;
• and
• wherein, when the heater is at a set temperature for an image heating operation in said image forming apparatus, a resistance value Rc of the second area of either of said first and second electrodes and a resistance value Rt between a portion within the second area of said first electrode electrically closest to the first area of said first electrode and a portion within the second area of said second electrode electrically closest to the first area of said second electrode satisfy a relation:
• Rc/Rt≦1/60.