IMAGE FORMING APPARATUS

• US 20120148273A1
• Filed: 12/01/2011
• Published: 06/14/2012
• Est. Priority Date: 12/08/2010
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Shimura, Yasuhiro, Kawarago, Atsushi, Hojo, Yuta, Sato, Kei
• Granted Patent: US 8,787,780 B2
• Time in Patent Office: Days
• US Class Current: 399/33
• CPC Class Codes: G03G 15/2039 with means for controlling the fixing temperature

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.

Claims

1. 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 either a first conduction path for supplying electric power to the first resistance heating element or a second conduction path for supplying electric power to the second resistance heating element,

and 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.

2. The image forming apparatus according to claim 1, 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 conduction path.

3. The image forming apparatus according to claim 1, further comprising a voltage detection unit configured to detect a voltage of a commercial power supply,

wherein the switching between the first operation mode and the second operation mode is automatically performed depending on the voltage detected by the voltage detection unit.