Directly-heating roller for fuse-fixing toner images

Claim 2

A directly-heating roller for fuse-fixing images formed from a toner, the roller comprising: (a) a roller body having a small heat capacity; (b) a bonding layer formed substantially uniformly on the outer peripheral surface of said roller body; (c) a lower insulating layer provided on said bonding layer; (d) a heat generating layer provided on said lower insulating layer and having a ceramic matrix and a metallic resistance layer dispersed in said ceramic matrix, said metallic resistance layer consisting essentially of 10 to 35 wt. % of an Ni-Cr alloy, said metallic resistance layer extending substantially continuously in the lengthwise direction of said roller, said heat generating layer having a thermal expansion coefficient substantially the same as that of said lower insulating layer; (e) an upper insulating layer provided on said heat generating layer; (f) a protective layer formed on said upper insulating layer so as to prevent offset of said toner images; and (g) an electrode layer formed on each end of said roller and adapted to connect said heat generating layer to an external power source.

Claim 3

A directly-heating roller according to claim 1, wherein said Ni-Cr alloy consists essentially of 5 to 20 wt. % of Cr and the balance substantially Ni.

Claim 4

A directly-heating roller according to claim 1 wherein said ceramic is Al 2 O 3 formed from a molten state.

Claim 5

A directly-heating roller according to claim 1, wherein each of said lower insulating layer and said upper insulating layer has a thermal expansion coefficient which is not smaller than 6×10 -6 /deg.

Claim 6

A directly-heating roller according to claim 4, wherein said lower insulating layer has a thickness ranging between 200 and 500 μm.

Claim 7

A directly-heating roller according to claim 5, wherein said lower insulating layer has a thickness of about 300 μm, while said upper insulating layer has a thickness of about 100 μm.

Claim 8

A directly-heating roller according to claim 4, wherein said heat insulating layers are made of an oxide selected from a group consisting of Al 2 O 3 , MgO, ZrO 2 , MgAl 2 O 4 , ZrO 2 .SiO 2 , and MnO.NiO.

Claim 9

A directly-heating roller according to claim 7, wherein said oxide is MgAl 2 O 4 .

Claim 10

A directly-heating roller according to claim 7, wherein said oxide is Al 2 O 3 .

Claim 11

A directly-heating roller according to claim 1, wherein the roller is made from a material selected from the group consisting of iron and iron alloys.

Claim 12

A directly-heating roller according to claim 10, wherein the wall thickness of said roller body is not greater than 2 mm.

Claim 13

A directly-heating roller according to claim 10, wherein the wall thickness of said roller body is not greater than 1 mm.

Claim 14

A directly-heating roller according to claim 1, wherein said bonding layer is made of a material selected from a group which consists of Ni-Al-Mo alloy, Ni-Al alloy and Ni-Cr alloy, and is partially oxidized.

Claim 15

A directly-heating roller according to claim 1, wherein said upper insulating layer has a thickness ranging between 30 and 200 m.

Claim 16

A directly-heating roller according to claim 1, wherein said upper insulating layer has a thickness of about 100 m.

Claim 17

A directly-heating roller according to claim 1, wherein said heat generating layer is formed by plasma spraying.

Claim 18

A directly-heating roller according to claim 1, wherein said ceramic matrix is Al 2 O 3 , and wherein said dispersed Ni-Cr alloy and said Al 2 O 3 matrix are formed concurrently by plasma spraying a mixture of the Ni-Cr alloy powder and Al 2 O 3 powder.

Claim 19

A directly-heating roller for fuse-fixing images formed form a toner, the roller comprising: (a) a hollow cylindrical roller body formed from a material selected from the group consisting of iron and iron alloys and having a wall thickness not greater than 1 mm; (b) a bonding layer formed substantially uniformly on the outer peripheral surface of said roller body, said bonding layer being formed from a material selected from a group consisting of Ni-Al-Mo alloy, Ni-Al alloy and Ni-Cr alloy and partially oxidized. (c) a lower insulating layer provided on said bonding layer and formed of a ceramic having a thermal expansion coefficient not smaller than 6×10 -6 /deg, said lower insulating layer having a thickness ranging between 200 and 500 m; (d) a heat generating layer provided on said lower insulating layer and having matrix formed from molten Al 2 O 3 and an Ni-Cr alloy resistance layer constituted by an Ni-Cr alloy dispersed in said matrix, said Ni-Cr alloy resistance layer extending substantially continuously in the length-wise direction of said roller; (e) an upper insulating layer provided on said heat generating layer; (f) a protective layer formed on said upper insulating layer for preventing offset of said toner images; and (g) an electrode layer formed on each end of said roller and adapted to connect said heat generating layer to an external power source.

Claim 20

A directly-heating roller for fuse-fixing images formed form a toner, the roller comprising: (a) a hollow cylindrical roller body formed from a material selected from the group consisting of iron and iron alloys and having a wall thickness not greater than 1 mm; (b) a bonding layer formed substantially uniformly on the outer peripheral surface of said roller body, said bonding layer being formed from a material selected from a group consisting of Ni-Al-Mo alloy, Ni-Al alloy and Ni-Cr alloy and partially oxidized. (c) a lower insulating layer provided on said bonding layer and formed of a ceramic having a thermal expansion coefficient not smaller than 6×10 -6 /deg, said lower insulating layer having a thickness ranging between 200 and 500 m; (d) a heat generating layer provided on said lower insulating layer and having matrix formed from molten Al 2 O 3 and an Ni-Cr alloy resistance layer constituted by an Ni-Cr alloy dispersed in said matrix, said Ni-Cr alloy resistance layer extending substantially continuously in the length-wise direction of said roller; (e) an upper insulating layer provided on said heat generating layer; (f) a protective layer formed on said upper insulating layer for preventing offset of said toner images; and (g) an electrode layer formed on each end of said roller and adapted to connect said heat generating layer to an external power source.

Claim 21

A directly-heating roller according to claim 18, wherein said insulating layer is made of MgAl 2 O 4 , while said heat generating layer is formed of a material consisting essentially of 10 to 35 wt. % of an Ni-Cr alloy and the balance substantially Al 2 O 3 ceramic.

Claim 22

A directly-heating roller according to claim 18, wherein said insulating layer is made of Al 2 O 3 , while said heat generating layer is made of a material consisting essentially of 10 to 35 wt. % of an Ni-Cr alloy and the balance substantially Al 2 O 3 ceramic.