Granted Patent B2

US 12,650,660 · App. 18/814,726 · Granted Jun 9, 2026

Inventor: Kazuhiro Doda (Kanagawa, JP)

Assignee: Canon Kabushiki Kaisha

G03G15/2039

Abstract

Claims (33)

1 . An image forming apparatus comprising:

a fixing unit including a tubular film, a pressure roller abutting against an outer surface of the film to form a nip portion, and a heater including a heating element, wherein the fixing unit is configured to fix a toner image to a recording material by heating the toner image on the recording material with the heater at the nip portion; and

a control unit configured to:

in a case where an accumulated electrical energy supplied to a portion of the heating element, is a first amount, perform a heat-leveling operation for a first period of time after the recording material has passed the nip portion, the heat-leveling operation being an operation for leveling a heat distribution in the nip portion; and

in a case where the accumulated electrical energy supplied to the portion of the heating element is a second amount greater than the first amount, perform the heat-leveling operation for a second period of time longer than the first period of time after the recording material has passed the nip portion,

wherein a first area of the nip portion is an area through which the recording material conveyed to the nip portion passes and a second area of the nip portion is an area through which the recording material conveyed to the nip portion does not pass, and

wherein the portion of the heating element is located in an area corresponding to the second area of the nip portion.

2 . The image forming apparatus according to claim 1 ,

wherein the heater is configured to be supplied with power from an AC power supply.

3 . The image forming apparatus according to claim 2 , further comprising

a switch configured to connect and disconnect a power supply path from the AC power supply to the heater,

wherein the control unit is configured to output a control signal for controlling the switch in each half cycle of a power supply frequency of the AC power supply.

4 . The image forming apparatus according to claim 3 , further comprising:

a voltage detection unit configured to detect a voltage applied to the heater by the AC power supply; and

a current detection unit configured to detect a current flowing from the AC power supply to the heater,

wherein the control unit is configured to calculate the accumulated electrical energy supplied to the portion of the heating element corresponding to the second area, based on a voltage value detected by the voltage detection unit, a current value detected by the current detection unit, a length of the recording material in a direction orthogonal to a conveyance direction of the recording material that passes through the nip portion, and a length of the heater in a longitudinal direction.

5 . The image forming apparatus according to claim 4 ,

wherein electrical energy supplied to the heating element is calculated based on the voltage value and the current value.

6 . The image forming apparatus according to claim 2 ,

wherein the heater includes a plurality of heating elements having different lengths in a longitudinal direction,

wherein the image forming apparatus further comprises a plurality of switches configured to connect and disconnect power supply paths from the AC power supply to the plurality of heating elements, and

wherein the control unit is configured to supply power to the plurality of heating elements every half cycle of a power supply frequency of the AC power supply by outputting a control signal for controlling the plurality of switches in accordance with a length, in a direction orthogonal to a conveyance direction, of the recording material that passes through the nip portion.

7 . The image forming apparatus according to claim 6 ,

wherein the control unit is configured to control the plurality of switches such that power is not supplied to two or more heating elements during each half cycle of the power supply frequency.

8 . The image forming apparatus according to claim 7 , further comprising

a temperature detection unit configured to detect a temperature of the heater at a time when printing on the recording material is started,

wherein the control unit is configured to determine proportions of power supply to a first heating element and to a second heating element among the plurality of heating elements, the second heating element having a length in the longitudinal direction shorter than a length of the first heating element, and a length, in a direction orthogonal to a conveyance direction, of the recording material that passes through the nip portion being closer to the length of the second heating element than to the length of the first heating element.

9 . The image forming apparatus according to claim 8 ,

wherein the proportion of power supply to the first heating element increases as a temperature of the heater detected by the temperature detection unit becomes lower, and the proportion of power supply to the second heating element increases as a temperature of the heater detected by the temperature detection unit becomes higher.

10 . The image forming apparatus according to claim 1 ,

wherein the control unit is configured to stop the pressure roller during a period of time in which the heat-leveling operation is executed, or to drive the pressure roller during the period of time.

11 . The image forming apparatus according to claim 1 ,

wherein the heater is arranged in an interior space of the film, the film being nipped by the heater and the pressure roller, and the toner image on the recording material is heated by the film at the nip portion.

Priority Claims (1)

Continuity (3)

References Cited (13)