HEATING DEVICE FOR HEATING RECORDING MATERIAL, AND IMAGE FORMING APPARATUS HAVING THE SAME

• US 20140027441A1
• Filed: 06/26/2013
• Published: 01/30/2014
• Est. Priority Date: 07/26/2012
• Status: Active Grant

• Current Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Original Assignee: Canon Ayutthaya Limited (Canon Inc.)
• Inventors: Mine, Ryuta, Abe, Toshiyuki
• Granted Patent: US 10,321,518 B2
• Time in Patent Office: Days
• US Class Current: 219/538
• CPC Class Codes: H05B 1/0241 For photocopiers
• CPC Class Codes: H05B 2203/004 using zigzag layout
• CPC Class Codes: H05B 2203/005 using multiple resistive elements or resistive zones isolated from each other
• CPC Class Codes: H05B 2203/013 Heaters using resistive films or coatings
• CPC Class Codes: H05B 2203/037 Heaters with zones of different power density
• CPC Class Codes: H05B 3/02 Details
• CPC Class Codes: H05B 3/265 the insulating base being an inorganic material, e.g. ceramic H05B3/262 takes precedence

Abstract

A heating device capable of suppressing electrically conductive parts that electrically connect power supply electrodes and heating resistors from generating heat. The heating device has heating resistors disposed in a longitudinal direction of an elongated base plate and connected through electrically conductive parts to power supply electrodes disposed on one longitudinal end portion of the base plate and supplied with electric power from the power supply electrodes. The electrically conductive parts are formed such that electrically conductive parts that can provide larger amounts of power supply each have a larger cross-sectional area perpendicular to a power supply direction.

Claims

1. A heating device comprising:

a base plate;

a plurality of heating resistors disposed in a longitudinal direction of said base plate;

a plurality of power supply electrodes disposed on one longitudinal end portion of said base plate and configured to supply electric power to respective ones of said plurality of heating resistors; and

a plurality of electrically conductive parts configured to connect said plurality of heating resistors and said plurality of power supply electrodes to one another,

wherein said plurality of electrically conductive parts are formed such that electrically conductive parts capable of providing larger amounts of power supply have larger areas of cross section perpendicular to a power supply direction.

2. The heating device according to claim 1, wherein said plurality of electrically conductive parts are formed such that the electrically conductive parts capable of providing larger amounts of power supply are shorter in length, and

said plurality of power supply electrodes are disposed such that power supply electrodes connected to the electrically conductive part capable of providing larger amounts of power supply are disposed nearer to said plurality of heating resistors.

3. The heating device according to claim 1, wherein said plurality of electrically conductive parts have resistance values that are adjusted such that power losses in said plurality of electrically conductive parts become substantially uniform to one another.

4. The heating device according to claim 1, wherein said plurality of electrically conductive parts have resistance values whose ratio is proportional to reciprocals of squares of currents flowing through said plurality of electrically conductive parts.

5. The heating device according to claim 1, wherein said plurality of heating resistors have first and second heating resistor groups,

said first heating resistor group is comprised of a pair of heating resistors that are disposed substantially symmetrically with each other with respect to a virtual axis passing through a predetermined reference position in a lateral direction of said base plate and that have end portions thereof disposed on a side close to another longitudinal end portion of said base plate and connected to be electrically conductive to each other,

said second heating resistor group is comprised of a pair of heating resistors that are disposed remoter from the virtual axis than said first heating resistor group in the lateral direction of said base plate and substantially symmetrically with each other with respect to the virtual axis and that have end portions thereof disposed on the side close to the other longitudinal end portion of said base plate and connected to be electrically conductive to each other,

said first and second heating resistor groups each have two electrical end portions to which corresponding ones of said plurality of power supply electrodes are connected, and

end portions of said first and second heating resistor groups disposed on the side close to the other longitudinal end portion of said base plate are configured to be electrically non-conductive to each other.

6. The heating device according to claim 5, wherein one of power supply electrodes connected to said first heating resistor group and one of power supply electrodes connected to said second heating resistor group are formed into a common electrode.

7. The heating device according to claim 5, wherein the pair of heating resistors of said first heating resistor group are each configured such that an amount of heat generated at a longitudinal central portion of said base plate becomes greater than an amount of heat generated at each of opposite end portions of said base plate, and

the pair of heating resistors of said second heating resistor group are each configured such that an amount of heat generated at the longitudinal central portion of said base plate becomes smaller than an amount of heat generated at each of the opposite end portions of said base plate.

8. The heating device according to claim 5, wherein said first heating resistor group has a resistance value smaller than a resistance value of said second heating resistor group.

9. An image forming apparatus comprising:

a document reading unit, and

an image forming unit, the image forming unit including a thermal fixing device comprising

a base plate;

a plurality of heating resistors disposed in a longitudinal direction of said base plate;

a plurality of power supply electrodes disposed on one longitudinal end portion of said base plate and configured to supply electric power to respective ones of said plurality of heating resistors; and

a plurality of electrically conductive parts configured to connect said plurality of heating resistors and said plurality of power supply electrodes to one another,

wherein said plurality of electrically conductive parts are formed such that electrically conductive parts capable of providing larger amounts of power supply have larger areas of cross section perpendicular to a power supply direction.