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US 8,787,780 B2Granted
Image forming apparatus having a fixing unit comprising a current detection unit
AssigneeCanon Kabushiki Kaisha
InventorsYasuhiro Shimura, Atsushi Kawarago, Yuta Hojo, Kei Sato
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Abstract
An apparatus is capable of switching between a mode in which a first resistance heating element and a second resistance heating element are connected in series and a mode in which they are connected in parallel. When a temperature increase rate detected by a temperature detection unit is smaller than a threshold rate although a current detected by a current detection unit is greater than a threshold current, a notification of a failure is issued.
Claims8
An image forming apparatus comprising:
- an image forming unit configured to form an image on a recording sheet;
- and
- a fixing unit comprising;
- an endless belt;
- a heater including a first resistance heating element and a second resistance heating element, the first and second resistance heating elements formed on a substrate and being in contact with an inner surface of the endless belt;
- a nip forming element that forms, together with the heater via the endless belt, a fixing nip for nipping and conveying a recording sheet having an image formed thereon, and
- a temperature detection unit that detects a temperature of the heater, the fixing unit capable of switching between a first operation mode in which the first resistance heating element and the second resistance heating element are connected in series and a second operation mode in which the first resistance heating element and the second resistance heating element are connected in parallel,
- wherein the image forming apparatus further comprises a current detection unit disposed in a conduction path after branching toward the first resistance heating element and the second resistance heating element in a parallel connecting state,
- wherein if a temperature increase rate detected by the temperature detection unit is less than a threshold rate, although a current detected by the current detection unit is greater than a threshold current, a notification of a failure is issued or a driving operation of the apparatus is stopped, and wherein the first resistance heating element is disposed on an upstream side in a recording sheet conveying direction with respect to the second resistance heating element, and the current detection unit detects a current in the first resistance heating element.
6 more elements
An image forming apparatus comprising:
- an image forming unit configured to form an image on a recording sheet;
- a fixing unit comprising;
- a heater including a first resistance heating element and a second resistance heating element;
- and
- a temperature detection unit that detects a temperature of the heater, the fixing unit capable of switching between a series connecting state in which the first resistance heating element and the second resistance heating element are connected in series and a parallel connecting state in which the first resistance heating element and the second resistance heating element are connected in parallel,
- a current detection unit disposed in a conduction path after branching toward the first resistance heating element and the second resistance heating element in the parallel connecting state, and
- a controller;
- wherein if a temperature increase rate detected by the temperature detection unit is less than a threshold rate, although a current detected by the current detection unit is greater than a threshold current, the controller issues a notification of a failure or stops a driving operation of the apparatus,
- wherein the first resistance heating element is provided between a first electrode and a third electrode and the second resistance heating element is provided between a second electrode and the third electrode, wherein the apparatus further comprises a first switch unit provided between the third electrode and a first output terminal of an AC power supply, and a second switch unit provided on a power supply path so as to switch whether the second electrode is connected to the first output terminal of the AC power supply or a second output terminal of the AC power supply, and wherein the current detection unit is provided between the first electrode and the second output terminal of the AC power supply.
6 more elements
Dependencies are inferred from the claim text.